Name: a protocol for safe lithiation reactions using organolithium reagents
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Description: Watch this Scientific Journal Video about A Protocol for Safe Lithiation Reactions Using Organolithium Reagents at JoVE.com

Support of this research by the National Science Foundation through grants 1254545 and 1437814 is gratefully acknowledged.

NOTE: tBuLi solutions (1.7 M in pentane) and anhydrous tert-butylamine were purchased and used immediately, without purification. In our experience, this protocol works best with freshly-purchased reagents. Standardization of the organolithium reagent may be employed via titration with dibromoethane28, diphenylacetic acid29, or N-pivaloylanilines30, since concentrations of commercial organolithium reagents may vary and the quality of reagents degrades over time. Pentane was purified using a solvent purification system. Solvents were degassed and stored over activated molecular sieves for 24 hr before use.
1. Preparation of Hood Space
NOTE: See Figure 1.
<ol>
	<li>Clear a hood of all clutter.</li>
	<li>Fill a small beaker with a volume of toluene approximately equal to the volume of organolithium reagent to be used (here, 10 ml for the small-scale protocol and 50 ml for the large-scale protocol) and cover with an appropriately-sized watch glass.</li>
	<li>Prepare a beaker of isopropanol with a volume approximately 5 times the amount of organolithium reagent to be used (here, 50 ml for the small-scale and 250 ml for the large-scale) and cover with an appropriately-sized watch glass.</li>
	<li>Prepare a beaker containing dry ice pellets filled up to the volume line approximately 10 times the volume of organolithium reagent to be used (here, 100 ml for the small scale and 500 ml for the large-scale).</li>
	<li>Before proceeding further, inspect the seal/cap of the lithiating agent for corrosive buildup. If the seal is compromised, dispose of the reagent by slowly adding it to 8-10x its volume of dry ice in a beaker.</li>
</ol>
2. Procedure for Small-scale Lithiation in a Hood
NOTE: See Figure 1.
<ol>
	<li>Charge a 25 ml Schlenk flask with a stir bar and neat tBuNH2 (1.8 ml, 17.1 mmol) and fit it with a rubber septum.</li>
	<li>Degas the neat tBuNH2 by opening the Schlenk flask stopcock and turning the Schlenk line to vacuum briefly (~1 sec; tBuNH2 is volatile and will evaporate if held under vacuum). Immediately backfill with inert gas by turning the Schlenk stopcock to inert gas. Repeat twice more. Close the flask stopcock to isolate the flask.</li>
	<li>Prepare an inert gas blanket by attaching three tubes to a glass &#34;T&#34; adapter. Attach one tube to an inert gas source, a second to an oil bubbler, and a third to a Luer-lock needle adapter.</li>
	<li>Purge the blanket apparatus with inert gas for 5 min.</li>
	<li>Slow the flow rate so that a few bubbles per second pass through the oil bubbler.</li>
	<li>Insert the inert gas blanket needle into the septum of the reaction flask and immerse the flask in a dry ice/acetone bath with a magnetic stirrer. Stir gently until the flask has cooled.</li>
	<li>Clamp the tBuLi bottle (25 ml, 1.7 M in pentane) to a ring stand and remove the outer cap. If present, remove any Parafilm and wipe away any grease.</li>
	<li>Select a 20 ml glass syringe and an appropriately-sized plunger. The plunger should slide in easily and should not be able to wiggle or rattle. If a thumb is placed over the syringe tip to seal it, the plunger should not be easily pulled out.</li>
	<li>Fit the 20 ml glass syringe with a long (12 inches), flexible syringe needle. Always be certain to select a syringe with a volume at least double the volume of the reagent to be drawn, and always be sure to attach the needle securely to the syringe.</li>
	<li>Remove the needle adapter for the inert gas blanket from the reaction flask and move it to the tert-butyllithium bottle, piercing the bottle septum to put the reagent bottle under ambient inert gas pressure.
	<ol>
		<li>Alternatively, use a septum-inlet transfer adapter from the reagent vendor as an inert gas blanket. Attach the septum-inlet transfer adapter to the reagent bottle and open the side and top caps. Attach a Schlenk hose to the side arm and purge with inert gas. While purging, replace the top cap with a septum. Leave the Schlenk line stopcock open to the septum-inlet transfer adapter to keep it under positive pressure. 
		NOTE: The commercial vendor suggests the use of a pressurized inert gas source instead of a blanket. This permits the reagent to be &#34;pushed&#34; into the syringe instead of drawn in by pulling the syringe. If the back-pressure setting is not right, over-pressurization can cause the plunger to be pushed out, exposing the reagent to air. Further, back pressure requires the experimenter to apply an equal and opposite pressure on the plunger with the thumb once the desired volume is reached so that the volume in the syringe is held constant. This can cause the reagent to squirt when the needle is pulled from the septum. Thus, the authors prefer the use of an ambient pressure inert gas blanket.</li>
	</ol>
	</li>
	<li>Purge the syringe with inert gas. Open an unoccupied Schlenk hose to inert gas so that there is a gentle flow of inert gas out of the Schlenk hose. Place the needle of the syringe loosely into the end of the hose and draw the plunger in and out several times to purge the interior of the syringe with inert gas.</li>
	<li>With the syringe plunger fully depressed, pierce the bottle septum and immerse the needle in the reagent.</li>
	<li>Gently draw back the plunger until an excess (~11 ml) of reagent has been drawn into the syringe (never invert the reagent bottle). Expel the headspace gas and excess reagent from the syringe by flexing the needle so that the syringe points up and then depressing the plunger until there is no headspace and there is 10.0 ml of reagent in the syringe. At this point, relax the flexion of the syringe needle, turning the syringe right side up.</li>
	<li>With the syringe needle still in the bottle septum, move the inert gas blanket needle adapter back to the reagent flask septum and pierce it.</li>
	<li>Remove the syringe needle from the bottle septum using a free hand (never pull on the syringe to remove the needle, as the needle may pop off). Some flames may be observed upon removal of the needle from the septum. Pierce the rubber septum of the reaction flask with the long syringe needle and suspend it above the stirred tBuNH2.</li>
	<li>Depress the plunger slowly to add all the tBuLi solution dropwise to the stirred tBuNH2.</li>
	<li>Remove the long syringe needle from the septum, leaving the inert gas blanket needle in the reaction flask septum.</li>
	<li>Remove the watch glass from the beaker of toluene and draw a volume of toluene approximately equal to the volume of tBuLi used (~10 ml) into the syringe to dilute the residual tBuLi.</li>
	<li>Remove the watch glass from the isopropanol beaker, place the long needle into the isopropanol, and empty the dilute solution in the syringe into the isopropanol.</li>
	<li>Rinse the syringe several more times with isopropanol to remove residual reagent, after which the syringe is clean.</li>
	<li>Seal the tBuLi reagent bottle septum with some grease to avoid leaks at the puncture sites and place a piece of Parafilm over the greased septum. Replace the outer cap.</li>
	<li>Remove the flask from the ice bath and stir under an ambient inert gas atmosphere until it comes to room temperature.</li>
	<li>Remove the inert gas blanket needle.</li>
	<li>Store the flask at -30 &#176;C overnight. After this time, white powdery solid of [LiNHtBu]8 will be observed.</li>
	<li>Filter the solution, rinse the solid with cold pentane under an inert atmosphere, and dry in vacuo.</li>
</ol>
3. Procedure for Large-scale Lithiation in a Hood
<ol>
	<li>Charge a 100 ml Schlenk flask with a stir bar and neat tBuNH2 (9 ml, 85.5 mmol) and fit it with an addition funnel that holds at least 50 ml. Clip the addition funnel to the flask using a keck clamp. Cap the top of the addition funnel with a rubber septum. Close the addition funnel&#39;s stopcock.</li>
	<li>Degas the neat tBuNH2 by opening the Schlenk flask stopcock and turning the Schlenk line to vacuum briefly (~1 sec; tBuNH2 is volatile and will evaporate if held under vacuum). Immediately backfill with inert gas by turning the Schlenk stopcock to inert gas. Repeat twice more. Close the flask stopcock to isolate the flask and the addition funnel.</li>
	<li>Prepare an inert gas blanket by attaching three tubes to a glass &#34;T&#34; adapter. Attach one tube to an inert gas source, a second to an oil bubbler, and a third to a Luer-lock needle adapter.</li>
	<li>Purge the blanket apparatus with inert gas for 5 min.</li>
	<li>Slow the flow rate so that a few bubbles per sec pass through the oil bubbler.</li>
	<li>Clamp the tBuLi bottle to a ring stand and remove the outer cap. Remove any Parafilm and wipe away any grease.</li>
	<li>Transfer the inert gas blanket to the septum of the addition funnel. Lower the flask into a dry ice bath to cool.</li>
	<li>Using another inert gas line, apply a gentle flow of inert gas to the tBuLi bottle.</li>
	<li>Insert one end of a cannula into the tBuLi bottle and suspend it above the solution.</li>
	<li>Insert the other end into the addition funnel so that the tip is below the pressure equalizing side-arm.</li>
	<li>Lower the end of the cannula above the tBuLi into the liquid and control the speed of addition via the inert gas line. Fill the addition funnel to the 50 ml line.</li>
	<li>When the addition is complete, remove the cannula end from the lithiating reagent solution and leave it suspended above the tBuLi reagent.</li>
	<li>Remove the opposite end of the cannula from the addition funnel.</li>
	<li>Remove the end of the cannula in the tBuLi bottle. Then, remove the inert gas line from the tBuLi bottle.</li>
	<li>Turn the stopcock on the addition funnel to add the tBuLi dropwise to the stirring tBuNH2.</li>
	<li>Seal the tBuLi reagent bottle septum with some grease to avoid leaks at the puncture sites and place a piece of Parafilm over the greased septum. Replace the outer cap.</li>
	<li>Remove the addition funnel from the Schlenk flask using the following steps:
	<ol>
		<li>Place the Schlenk flask under positive pressure of inert gas by opening the Schlenk flask stop cock and the Schlenk line stop cock. Remove the keck clamp and the addition funnel from the Schlenk flask. The flask will be protected by a flow of inert gas out of the flask, but the addition funnel may smoke or flame briefly upon exposure to air.</li>
		<li>Wipe away the grease on the inner neck of the Schlenk flask using a paper towel wetted with hexanes and repeat until the ground glass of the flask appears dry. Stopper the flask with a rubber septum.</li>
		<li>Place the inert gas blanket needle into the Schlenk flask septum.</li>
	</ol>
	</li>
	<li>Remove the flask from the ice bath and stir under an ambient inert gas atmosphere until it comes to room temperature.</li>
	<li>Remove the inert gas blanket needle.</li>
	<li>Store the flask at -30 &#176;C overnight. After this time, white powdery solid of [LiNHtBu]8 will be observed.</li>
	<li>Filter the solution, rinse the solid with cold pentane under an inert atmosphere, and dry in vacuo.</li>
</ol>
4. Procedure for Lithiation in a Glovebox
<ol>
	<li>Bring all reagents, a reaction flask, a stir bar, a stopper, and a greased desiccator (or another sealable container to be used for waste) into the glovebox via the antechamber.</li>
	<li>Charge a flask with a stir bar and degassed neat tBuNH2 (1.8 ml, 17.1 mmol). Cover the flask with a glass stopper or septum to prevent evaporation of volatile tert-butyl amine.</li>
	<li>Clamp the tBuLi bottle (25 ml, 1.7 M in pentane) to a ring stand and remove the outer cap. Optional: Remove the septum cap using a bottle opener, with the bottle firmly clamped in place. Once the bottle cap is removed, do not remove the bottle from the glovebox until empty. If removed, carefully quench the remaining tBuLi in a hood with an appropriate quenching reagent such as dry ice or isopropanol.</li>
	<li>Prepare a small vial of ~10 ml toluene to wash the syringe after the addition.</li>
	<li>Fit a 20 ml syringe with a needle. Always be certain to select a syringe with a volume at least double the volume of the reagent to be drawn, and always be sure to attach the needle securely to the syringe.</li>
	<li>Insert the needle into the tBuLi reagent and gently draw the plunger back until an excess (~11 ml) of reagent has been drawn into the syringe. Then, invert the syringe, pointing the needle up.</li>
	<li>Hold a paper towel near the needle and gently depress the plunger to remove the headspace gas until a microdroplet of reagent emerges from the end of the needle. Remove excess reagent from the syringe by placing the needle into the reagent bottle and depressing the plunger until 10.0 ml of reagent remains in the syringe. If any reagent solution spills, wipe it up with a paper towel or Kimwipe and place the waste into the waste desiccator.</li>
	<li>Remove the stopper or septum from the reaction flask and slowly add the tBuLi to the stirred tBuNH2. Since the reaction is performed without a cold bath, take care to avoid adding the reagent too quickly, as the exotherm can cause boiling. Stopper the reaction flask.</li>
	<li>Draw toluene from the toluene vial into the syringe to dilute the residual reagent, and place the syringe, needle, and any paper towel waste into the desiccator. Seal the desiccator.</li>
	<li>Re-cap and store the tBuLi reagent bottle, preferably in a glovebox freezer to improve longevity.</li>
	<li>Remove the sealed desiccator containing the used glassware, the syringe with toluene, and any paper towels from the glovebox, and immediately place it into a hood.</li>
	<li>Open the desiccator and empty the syringe containing dilute tBuLi into a beaker of isopropanol to quench the reagent. Rinse the syringe several more times with isopropanol.</li>
	<li>Store the reaction flask at -30 &#176;C overnight, after which time white powdery solid of [LiNHtBu]8 are observed.</li>
	<li>Filter the solution, rinse the solid with cold pentane under an inert atmosphere, and dry in vacuo.</li>
</ol>
5. How to Abort the Reaction or in Case of Fire
NOTE: See Figure 1.
<ol>
	<li>If at any point the reaction needs to be aborted, slowly empty any unused organolithium reagent in the syringe into the dry ice. Flames may occur as the reagent is emptied, but the dry ice should quench them.</li>
	<li>If at any point the toluene or isopropanol catches fire, simply place the watch glass onto the beaker so that the flames will be smothered.</li>
	<li>If a circumstance ever occurs where a fire cannot be quenched by this method, immediately use the fire extinguisher.</li>
	<li>In the unlikely event that hair or clothing catches fire, immediately use the safety shower.</li>
</ol>

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K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+analysis+of+organolithium+compounds.">The analysis of organolithium compounds.</a> Journal of Organometallic Chemistry. 2 (6), 447-454 (1964).</li><li>Kofron, W. G., Baclawski, L. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+convenient+method+for+estimation+of+alkyllithium+concentrations.">A convenient method for estimation of alkyllithium concentrations.</a> J Org Chem. 41 (10), 1879-1880 (1976).</li><li>Suffert, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Simple+direct+titration+of+organolithium+reagents+using+N-pivaloyl-o-toluidine+and/or+N-pivaloyl-o-benzylaniline.">Simple direct titration of organolithium reagents using N-pivaloyl-o-toluidine and/or N-pivaloyl-o-benzylaniline.</a> J Org Chem. 54 (2), 509-510 (1989).</li><li>Barnett, N. D. R., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Novel+octameric+structure+of+the+lithium+primary+amide+[{ButN(H)Li}8]+and+its+implication+for+the+directed+synthesis+of+heterometallic+imide+cages.">Novel octameric structure of the lithium primary amide [{ButN(H)Li}8] and its implication for the directed synthesis of heterometallic imide cages.</a> Chem Comm. 32 (20), 2321-2322 (1996).</li><li>Sigma-Aldrich. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Technical Bulletin AL-134: Handling Air-Sensitive Reagents. , (2012).</li></ol>

The authors have nothing to disclose.

For this lithiation experiment, tert-butyl lithium amide (LiNHtBu) is synthesized via lithiation of tert-butyl amine (tBuNH2) using tert-butyl lithium (tBuLi), forming isobutane as a side product. The described protocol is a modification of a previously-reported protocol31 and proceeds according to the following reaction:
tBuNH2 + tBuLi&#160; &#8594;&#160; tBuH + 1/8 [LiNHtBu]8. &#160; &#160;&#160; (2)
The original report for the synthesis of LiNHtBu differs from this protocol in that it employed the use of less reactive n-butyl lithium as the organolithium reagent. In general, one should always choose the less reactive organolithium reagent whenever possible. However, for the purpose of this paper, the authors have elected to demonstrate the safe usage of the more reactive tert-butyl lithium solution so that viewers can observe the proper handling of the most challenging reagent. This protocol may be easily applied to the use of the less reactive organolithium reagents.
Critical Steps 
Due to the highly pyrophoric nature of organolithium reagents, all operations must be carried out under inert atmosphere conditions, necessitating the use of a Schlenk or inert gas line, or an inert atmosphere glovebox. While operation in a glovebox is a far simpler approach, it is associated with its own risks, different from those of performing lithiations on an inert gas line. Either of these approaches therefore requires great care and adherence to protocol. Described here are two protocols for lithiation: one on an inert gas (Schlenk) line, and one within a glovebox. When performing a lithiation on an inert gas line, a familiarity with the operation of air-free glassware and protocols is invaluable. However, since different laboratories may adopt slightly different practices, a step-by-step protocol for each method is thoroughly described. The chemical vendor offers its own recommended glassware apparatus and protocol for proper use of air-sensitive reagents32. The Protocol section outlines a procedure similar to the vendor&#39;s, but which has been modified to maximize safety and ease, specifically for alkyllithium protocols. The detailed procedure is available in the Protocol section, but here, some important points are highlighted to maximize safety and success.
NOTE: Never work in the laboratory alone. 
PPE 
An extremely important consideration is the use of proper personal protective equipment (PPE), which for lithiation includes a proper-fitting lab coat, safety glasses, long pants (preferably made of non-flammable material), closed-toed shoes, and a hair tie (if applicable). While best practices can ensure that no fires occur in most cases, tert-butyl lithium is extremely pyrophoric, and accidents can happen. When they do, the safety of the researcher is better secured if they are shielded by the proper PPE. The UCLA alumna&#39;s most significant mistakes were that she performed a lithiation with no laboratory coat and that she was wearing clothing made of flammable material20.
Ventilation 
Lithiations outside the glovebox should always be performed in a hood. If a clear hood is not available, do not perform a lithiation until a clear, uncluttered hood space free of other flammable chemicals is secured. The sash should be lowered as much and as often as possible. An additional mistake of the UCLA alumna was that there were other flammables in the hood (hexanes), which spilled and caught fire, igniting her clothes20.
Inert Gas 
A lithiation requires the use of inert gas. A Schlenk line (double manifold switchable between inert gas and vacuum) is ideal, though any inert gas source with good flow control will work.
Syringe 
Glass syringes are preferable to plastic syringes due to their chemical inertness and smoother plunger motion. A long (1-2 ft)32, flexible needle must always be attached securely to the delivery syringe. Another of the UCLA alumna&#39;s mistakes was the use of a too-short (1.5 inches)20 needle, which may have necessitated inverting the reagent bottle to draw the reagent into the syringe, which can lead to spills and fire. Thus, a long needle should always be used so that the bottle does not need to be inverted. The needle should be attached securely so that it does not pop off during reagent delivery. Luer-lock style syringes (Figure 2) are best. If using a push-on &#34;slip-tip&#34; syringe needle system, ensure that the needle is extremely well attached before proceeding. A syringe should always be selected that is at least twice the volume of the desired quantity of organolithium reagent32. This is due to the fact that head space always occupies some volume of the syringe while drawing a reagent. Another of the UCLA alumna&#39;s mistakes was the use of a syringe that was too small. When the syringe reached capacity, it likely popped open, splashing tBuLi onto her unprotected arm20.
Quenching Agents 
A small beaker containing toluene (volume approximately equal to the volume of organolithium reagent to be delivered) should be located in the hood within reach of &#8211; but not right next to &#8211; the reaction vessel. A watch glass appropriately sized to cover this beaker in case of fire should also be placed over the beaker. This beaker will be used to dilute the residual reagent contaminating the syringe after the reagent addition (Figure 1).
A second beaker containing isopropanol (volume approximately five times the volume of organolithium reagent to be delivered) should also be located in the hood within reach of &#8211; but not right next to &#8211; the reaction vessel. A second watch glass appropriately sized to cover this beaker in case of fire should also be placed on top of the beaker. This vessel is used to quench the residue left in the syringe after the addition (Figure 1).
Third, a beaker of dry ice (approximately ten times the volume of organolithium reagent to be delivered) should be located in reach of the reaction vessel. In the event of the syringe needle coming loose, or something else going wrong, this dry ice may be used to quench the remaining organolithium reagent in the syringe (Figure 1).
Finally, a fire extinguisher should be located nearby in case of emergency, and the location and proper operation of the safety shower should be noted.
The Reagent Bottle 
Outside the glovebox, use only organolithium reagent bottles with septum-sealed bottle caps (Figure 3). The purchase of small bottles is recommended since 1) organolithium reagents degrade over time, and long-term storage is not recommended, 2) septa can degrade over time, exposing the reagent to air, and 3) small volumes of pyrophorics are less dangerous than large volumes. The organolithium reagent bottle should be set on the bench and clamped to a ring stand before use (Figure 1).
The Reaction Vessel 
The reaction vessel should be oven- or flame-dried and cooled to room temperature under an inert atmosphere to ensure that no traces of water exist on the sides of the glass. The vessel containing the reagent to which the organolithium solution will be added should be clamped above a stir plate and degassed to remove air. This may be done either by purging the vessel with inert gas or by performing several evacuation-inert gas fill cycles on a Schlenk line. Alternatively, the flask can be charged with reagents and solvent in an inert atmosphere glovebox and sealed before removal from the glovebox. The degassed flask should be fitted with a septum and protected by an inert gas blanket (see Protocol and Figure 1). If the synthetic protocol permits, the flask should also be immersed into a cold bath such as dry ice/acetone to control the exotherm that will result when the organolithium reagent is added.
Notes on Lithiation in an Inert-atmosphere Glovebox 
The use of air-free gloveboxes makes the handling of air-sensitive reagents vastly simpler, but it comes with its own risks. Since organolithium reagents are shielded from air in the glovebox, it is easier to become complacent and careless. While handling the reagents is simpler, a spill within the glovebox creates a dilemma: the spilled reagent must be wiped up with paper towels, but then the pyrophoric reagent and flammable cloth must be removed from the box and placed back into air, at which point, they will immediately catch fire. To avoid these hazards, reagents and reaction flasks should always be clamped securely within the glovebox, and open bottles and flasks should never be moved or handled by hand. Any materials containing residual reagent should be removed from the glovebox in a sealed desiccator (or similar container) and moved to a hood before being opened and exposed to air.
Know the Location and Operation of Emergency Equipment 
Know the location and operation of the lab&#39;s fire extinguisher, so that in the event of a fire that cannot be put out by smothering with a watch glass, one can react quickly and decisively. Know also the location and operation of the laboratory&#39;s safety shower. In the unlikely event that a piece of clothing catches fire, immediately use the safety shower. If someone else&#39;s clothes catch fire, immediately direct them to the safety shower. If the laboratory does not have both a safety shower and a fire extinguisher, do not attempt a lithiation reaction. What may have been the final opportunity to save the life of the UCLA alumna was missed when neither she nor the postdoc working with her used the safety shower or an extinguisher to extinguish the flames. Rather, her postdoctoral coworker attempted to pat out the flames with a lab coat, which also caught fire. Ultimately, she sat on the floor while her postdoctoral coworker attempted to put out the flames by pouring beakers of water, filled from the sink, on the flames20.
Organolithium reagents are excellent for the deprotonation of weakly-acidic hydrogens or for acting as a source of alkyl groups, and they are more aggressive and reactive than the more standard Grignard reagents. Limitations of this technique can include kinetically sluggish reactions, in which case modification of the protocol can aid the chemical transformation19. Additionally, the high reactivity of organolithiums can interfere with desired chemistry. For instance, carbanions are generally excellent nucleophiles. Attempted deprotonation of an electrophilic substrate (such as a carboxylic acid) is likely to lead to nucleophilic attack instead of deprotonation. Thus, chemical knowledge and intuition is required when selecting reagents of this (or any) sort. Lithiation reactions will continue to play a role in synthetic organic and inorganic chemistry for the foreseeable future, and thus, an understanding of safe use is essential. Lithiation reactions are accomplished safely every day, and there is no cause to fear performing this reaction chemistry. However, the reagents deserve a measure of respect and care. It is essential that the multiple required fail-safes be followed to avoid the possibility of injury. In this protocol, a step-by-step procedure for a safe lithiation reaction is demonstrated and published as an open access article so that any researcher in the world can use it as training, free of charge. As such, the authors hope that this report may make the lithiation protocol accessible to a wide array of groups and prevent future tragedies.

reattivi di organo-litio (RLI) sono basi potenti che sfruttano i legami non polari, forti di idrocarburi per generare basi coniugate che possono deprotonate quasi qualsiasi composto di acidità anche moderata. Essi servono come alternative più aggressivi ad ammidi litio (ad esempio, LDA) e reagenti di Grignard. La loro incredibilmente forte basicità li rende di grande utilità nella sintesi organiche e inorganiche, e la loro ampia applicabilità è stata accuratamente descritta in diverse recensioni recenti 1-3. reattivi di organo-litio possono facilmente deprotonate acidi estremamente deboli quali alcoli, ammine, e idrocarburi sia benzilici e alifatici. La reazione è guidato dalla formazione di una stalla forte, legame, alchile CH. Li + R - + HX → LiX + RH (1) Concetti generali circostanti reattivi di organo-litio sono stati esaminati 4-7, ma noiqui evidenziare l&#39;utilità di questi reagenti di sfruttare la diversa pK a valori di più idrocarburi differenti per selezionare una base coniugata con appropriata alimentazione deprotonating. Per esempio, poiché l&#39;acidità di idrocarburi alifatici diminuisce con livelli crescenti di sostituzione (ad esempio, 1 °&gt; 2 °&gt; 3 °), terz -butyllithium è il reagente alkyllithium più aggressivo, mentre metillitio è il più delicato. Fenillitio è notevolmente più mite rispetto metillitio a causa della capacità del fenilico di delocalizzare la carica dell&#39;anione fenile deprotonato. Così, i reattivi di organo-litio più comunemente usati sono, in ordine crescente di basicità: PHLI &lt;Meli &lt;BuLi &lt;s -BuLi &lt;t BuLi. Mentre precisi valori di pK a delle alcani protonati sono difficili da misurare a causa della loro mancanza di acidità, pK approximate un valori sono forniti nella tabella 1 7-10 unlungo con altri reagenti protici incontrate comunemente deprotonato da reattivi di organo-litio in chimica sintetica. Tabella 1 prevede, in sintesi, uno strumento visivo per prevedere quali basi possono essere usati per deprotonate che acidi. Al di là di chimica acido-base, i reagenti alkyllithium sono state sfruttate in chimica inorganica e organometallica come mezzo per fornire leganti a base di carbonio 11,12, reagenti transmetallate nella catalisi 13-15, o facilitare la reattività organometallica da fotolito legame M-Me omolisi 16, 17. Mentre reagenti alkyllithium sono termodinamicamente basi molto forti, la loro reattività può essere lenta in alcune reazioni, che richiede l&#39;ottimizzazione delle condizioni di reazione 18. Generalmente, il loro comportamento cinetico può essere migliorata mediante sostituzione dello ione litio acido Lewis con un acido debole Lewis come il potassio, come si vede nella generazione di &quot;base di Schlosser&quot; di BuLi e tert potassio </em&gt; -butoxide 19. Mentre l&#39;utilità dei reattivi di organo-litio in sintesi è innegabile, l&#39;uso di questi reagenti richiede precauzioni appropriate. I reagenti sono piroforico, reagire violentemente in aria o con acqua e con una reazione esotermica vigorosa. Essi generano organiche volatili che spesso accendono a causa delle alte temperature di decomposizione. Così, gli incendi possono verificarsi durante lithiations, in particolare quando accurate procedure operative standard non vengono seguite. Più infame è il caso di un allieva di laurea di recente laureato della University of California, Los Angeles (UCLA), che lavora come assistente di ricerca. Come risultato di un tragico incidente durante una reazione litiazione con il reagente organolitio più reattiva, litio terz butil, lo studente ricevuto ustioni fatali quando una siringa piena di soluzione venne a parte e acceso i vestiti 20. Tra gli errori commessi erano l&#39;uso di una siringa impropriamente dimensioni unND ago, la mancanza di dispositivi di protezione adeguati (DPI), e un fallimento per usare la doccia di sicurezza disponibili 20. La natura sensibile dei reagenti carbanion comuni ha ispirato lo sviluppo di alternative più sicure in solventi ad alta polarità 21, come eutettiche miscele di solventi 22-24, e per i reagenti di Grignard, anche l&#39;acqua 25-27. Tuttavia, la versatilità di reattivi di organo-litio li rende di continuo programma di utilità per il prossimo futuro. L&#39;obiettivo di questo protocollo e sperimentare visualizzato è quello di dimostrare un approccio approfondito e attento a litiazione, accessibile a qualsiasi studente di chimica ben addestrato, che ha bisogno di reattivi di organo-litio. La nostra speranza è che questo protocollo di accesso aperto illustrerà che cosa fare (e cosa non fare) per ottenere un litiazione di successo e sicuro, che altri laboratori possono utilizzare questa pubblicazione come una risorsa di formazione, e che attraverso questo approfondita, demonstrati visivasu, futuri incidenti possono essere evitati. Qui, un protocollo sicuro per litiazione utilizzando litio tert-butil più reattiva viene descritta, che può essere adattato per l&#39;uso con i reagenti organolitio meno reattivi.

<table><tbody><tr><td>Schlenk Flask, 25 ml</td><td>Chemglass</td><td>AF-0520-02</td><td>25 ml Flask, Reaction, 14/20 outer joint, 2&amp;nbsp;mm glass stpk, Air-free, Schlenk</td></tr><tr><td>Rubber Septum</td><td>Chemglass</td><td>CG-3024-01</td><td>Septum stopper, suba-seal, For 14/20-14/35 outer joints and 12.5&amp;nbsp;mm ID tubing</td></tr><tr><td>Stir Bar</td><td>Fisher Scientific</td><td>14-512-130</td><td>Various sized stir bars</td></tr><tr><td>&lt;em&gt;tert&lt;/em&gt;-butyllithium</td><td>Sigma-Aldrich</td><td>186198-4X25ML</td><td>1.7 M &lt;em&gt;t&lt;/em&gt;-butyllithium in pentane, 4 x 25&amp;nbsp;ml</td></tr><tr><td>&lt;em&gt;tert&lt;/em&gt;-butylamine</td><td>Sigma-Aldrich</td><td>391433-100ML</td><td>&lt;em&gt;tert&lt;/em&gt;-butylamine, purified by redistillation, &gt;99.5%</td></tr><tr><td>hexanes</td><td>Fisher Scientific</td><td>H292-4</td><td>4 L, certified ACS, hexanes, &gt;98.5%</td></tr><tr><td>isopropanol</td><td>Fisher Scientific</td><td>A416-4</td><td>4 L, 2-propanol, certified ACS plus, &gt;99.5%</td></tr><tr><td>Dry ice</td><td>Airgas</td><td></td><td></td></tr><tr><td>Pure Solv Solvent Purification System</td><td>Inert Technology</td><td>MD-5</td><td>Alumina collumns through which fresh, degassed solvents are passed to remove water.</td></tr><tr><td>Aldrich Sure/Seal septum-inlet transfer adapter</td><td>Sigma-Aldrich</td><td>Z407186</td><td>Adapter for removal of air-sensitive reagents under nitrogen blanket</td></tr><tr><td>Keck Standard Taper Clips</td><td>Chemglass</td><td>CG-145-03</td><td>clamp for securing glassware connections</td></tr><tr><td>Addition Funnel</td><td>Kontes</td><td>K634000-0060</td><td>Funnel for dropwise addition of reagent to flask</td></tr></tbody></table>

a protocol for safe lithiation reactions using organolithium reagents

reattivi di organo-litio sono potenti strumenti nella cassetta degli attrezzi del chimico sintetico. Tuttavia, la natura estrema piroforico dei reagenti più reattivi garantisce la tecnica corretta, una formazione approfondita e corretta dispositivi di protezione individuale. Per aiutare nella formazione dei ricercatori svolta reattivi di organo-litio, un approfondito, step-by-step di protocollo per l&#39;uso sicuro ed efficace di terz -butyllithium su una linea di gas inerte o all&#39;interno di un cassetto portaoggetti è descritto. Come reazione di modello, preparazione di litio tert-butil amide dalla reazione di tert-butil ammina con un equivalente di litio tert-butil è presentato.

The typical yield of this reaction is ~670 mg (8.5 mmol, ~50%). Additional crops of crystals may be obtained by concentrating the filtrate and chilling the solution. However, purity is often compromised by additional crops. When this protocol is followed carefully by a prepared and practiced researcher, it generally proceeds without incident. In our experience, in the rare cases when the reaction must be aborted or a fire occurs, the availability of watch glass covers, dry ice, and isopropanol quench beakers, and the localization of the operation in a hood provide sufficient contingency.
Confirmation of the product by NMR (Figure 4) or X-ray diffraction is necessary, as the use of impure or water-contaminated reagents frequently leads to failure to obtain the desired product. The 1H NMR spectrum shows two peaks, as expected, in a ratio of 1:9 (representing, respectively, the single amide proton and the nine tert-butyl protons). Indexing of a crystal grown from pentane or hexane is consistent with the reported crystal structure of the product31. NMR (400 MHz, benzene-d6) &#948; -1.53 (s, 1H, NH), 1.37 (s, 9H, But). Unit cell: P2/n, a = 12.05(2), b = 12.62(2), c = 18.24(3) &#197;, &#946; = 105.52(5)&#176;, V = 2672(14) &#197;3.
<img alt="Figure 1" src="/files/ftp_upload/54705/54705fig1.jpg" /> 
Figure 1: Apparatus Diagram. The appearance of the interior of a hood for reaction outside the glovebox is shown. <a href="http://cloudflare.jove.com/files/ftp_upload/54705/54705fig1large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 2" src="/files/ftp_upload/54705/54705fig2.jpg" /> 
Figure 2: The Syringe with Needle. A 10 ml syringe with a needle attached using a Luer-lock tip is shown. <a href="http://cloudflare.jove.com/files/ftp_upload/54705/54705fig2large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 3" src="/files/ftp_upload/54705/54705fig3.jpg" /> 
Figure 3: Septum-sealed Bottle Cap. The reagent is sold by the vendor with a sealed metal bottle cap with a rubber septum that may be pierced with a needle. <a href="http://cloudflare.jove.com/files/ftp_upload/54705/54705fig3large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 4" src="/files/ftp_upload/54705/54705fig4.jpg" /> 
Figure 4: 400 MHz 1H NMR Spectrum of LiNHtBu in C6D6. The NMR spectrum of the product shows the expected two signals for the amide and tert-butyl protons, with an integral ratio of 1:9, respectively. Residual protiosolvent signal is labelled with *. <a href="http://cloudflare.jove.com/files/ftp_upload/54705/54705fig4large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<table fo:keep-together.within-page="1">
	<tbody>
		<tr>
			<td>Acid</td>
			<td>pKa</td>
			<td>Base</td>
		</tr>
		<tr>
			<td>i-butane7</td>
			<td>&#62;51</td>
			<td>tBuLi</td>
		</tr>
		<tr>
			<td>n-butane (2o carbon) 7</td>
			<td>~50</td>
			<td>s-BuLi</td>
		</tr>
		<tr>
			<td>n-butane (1o carbon) 7</td>
			<td>~50</td>
			<td>BuLi</td>
		</tr>
		<tr>
			<td>methane7</td>
			<td>48</td>
			<td>MeLi</td>
		</tr>
		<tr>
			<td>benzene7</td>
			<td>43</td>
			<td>PhLi</td>
		</tr>
		<tr>
			<td>toluene7</td>
			<td>40</td>
			<td>TolLi</td>
		</tr>
		<tr>
			<td>R2NH8</td>
			<td>36</td>
			<td>RNHLi</td>
		</tr>
		<tr>
			<td>ArNH29</td>
			<td>31</td>
			<td>ArNHLi</td>
		</tr>
		<tr>
			<td>ROH9</td>
			<td>15</td>
			<td>ROLi</td>
		</tr>
		<tr>
			<td>ArOH8,9</td>
			<td>10</td>
			<td>ArOLi</td>
		</tr>
	</tbody>
</table>
Table 1: pKa values of Hydrocarbons and Their Corresponding Lithiated Conjugate Bases.

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Video: A Protocol for Safe Lithiation Reactions Using Organolithium Reagents

Solid-state Graft Copolymer Electrolytes for Lithium Battery Applications

Battery safety has been a very important research area over the past decade. Commercially available lithium ion batteries employ low flash point (&lt;80 &deg;C), flammable, and volatile organic electrolytes. These organic based electrolyte systems are viable at ambient temperatures, but require a cooling system to ensure that temperatures do not exceed 80 &deg;C. These cooling systems tend to increase battery costs and can malfunction which can lead to battery malfunction and explosions, thus endangering human life. Increases in petroleum prices lead to a huge demand for safe, electric hybrid vehicles that are more economically viable to operate as oil prices continue to rise. Existing organic based electrolytes used in lithium ion batteries are not applicable to high temperature automotive applications. A safer alternative to organic electrolytes is solid polymer electrolytes. This work will highlight the synthesis for a graft copolymer electrolyte (GCE) poly(oxyethylene) methacrylate (POEM) to a block with a lower glass transition temperature (Tg) poly(oxyethylene) acrylate (POEA). The conduction mechanism has been discussed and it has been demonstrated the relationship between polymer segmental motion and ionic conductivity indeed has a Vogel-Tammann-Fulcher (VTF) dependence. Batteries containing commercially available LP30 organic (LiPF6 in ethylene carbonate (EC):dimethyl carbonate (DMC) at a 1:1 ratio) and GCE were cycled at ambient temperature. It was found that at ambient temperature, the batteries containing GCE showed a greater overpotential when compared to LP30 electrolyte. However at temperatures greater than 60 &deg;C, the GCE cell exhibited much lower overpotential due to fast polymer electrolyte conductivity and nearly the full theoretical specific capacity of 170 mAh/g was accessed.

Lithium ion batteries employ flammable and volatile organic electrolytes that are suitable for ambient temperature applications. A safer alternative to organic electrolytes are solid polymer batteries. Solid polymer batteries operate safely at high temperatures (&gt;120 &deg;C), thus making them applicable to high temperature applications such as deep oil drilling and hybrid electric vehicles. This paper will discuss (a) the polymer synthesis, (b) the polymer conduction mechanism, and (c) provide temperature cycling for both solid polymer and organic electrolytes.

A stato solido innesto elettroliti Copolimero per Batterie di litio Applicazioni

Battery safety has been a very important research area over the past decade. Commercially available lithium ion batteries employ low flash point (&lt;80 ...

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Ingegneria

Synthesis and Purification of Iodoaziridines Involving Quantitative Selection of the Optimal Stationary Phase for Chromatography

The highly diastereoselective preparation of cis-N-Ts-iodoaziridines through reaction of diiodomethyllithium with N-Ts aldimines is described. Diiodomethyllithium is prepared by the deprotonation of diiodomethane with LiHMDS, in a THF/diethyl ether mixture, at -78 &#176;C in the dark. These conditions are essential for the stability of the LiCHI2 reagent generated. The subsequent dropwise addition of N-Ts aldimines to the preformed diiodomethyllithium solution affords an amino-diiodide intermediate, which is not isolated. Rapid warming of the reaction mixture to 0 &#176;C promotes cyclization to afford iodoaziridines with exclusive cis-diastereoselectivity. The addition and cyclization stages of the reaction are mediated in one reaction flask by careful temperature control.
Due to the sensitivity of the iodoaziridines to purification, assessment of suitable methods of purification is required. A protocol to assess the stability of sensitive compounds to stationary phases for column chromatography is described. This method is suitable to apply to new iodoaziridines, or other potentially sensitive novel compounds. Consequently this method may find application in range of synthetic projects. The procedure involves firstly the assessment of the reaction yield, prior to purification, by 1H NMR spectroscopy with comparison to an internal standard. Portions of impure product mixture are then exposed to slurries of various stationary phases appropriate for chromatography, in a solvent system suitable as the eluent in flash chromatography. After stirring for 30 min to mimic chromatography, followed by filtering, the samples are analyzed by 1H NMR spectroscopy. Calculated yields for each stationary phase are then compared to that initially obtained from the crude reaction mixture. The results obtained provide a quantitative assessment of the stability of the compound to the different stationary phases; hence the optimal can be selected. The choice of basic alumina, modified to activity IV, as a suitable stationary phase has allowed isolation of certain iodoaziridines in excellent yield and purity.

A protocol for the diastereoselective one-pot preparation of cis-N-Ts-iodoaziridines is described. The generation of diiodomethyllithium, addition to N-Ts aldimines and cyclization of the amino gem-diiodide intermediate to iodoaziridines is demonstrated. Also included is a protocol to rapidly and quantitatively assess the most appropriate stationary phase for purification by chromatography.

Sintesi e purificazione di Iodoaziridines Coinvolgere quantitativa Selezione del Ottimale fase stazionaria per cromatografia

The highly diastereoselective preparation of cis-N-Ts-iodoaziridines through reaction of diiodomethyllithium with N-Ts aldimines is described. ...

Chimica

Protocol of Electrochemical Test and Characterization of Aprotic Li-O2 Battery

We demonstrate a method for electrochemical testing of an aprotic Li-O2 battery. An aprotic Li-O2 battery is made of a Li-metal anode, an aprotic electrolyte, and an O2-breathing cathode. The aprotic electrolyte is a solution of lithium salt with aprotic solvent; and porous carbon is commonly used as the cathode substrate. To improve the performance, an electrocatalyst is deposited onto the porous carbon substrate by certain deposition methods, such as atomic layer deposition (ALD) and wet-chemistry reaction. The as-prepared cathode materials are characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray absorption near edge structure (XANES). A Swagelok-type cell, sealed in a glass chamber filled with pure O2, is used for the electrochemical test on a battery test system. The cells are tested under either capacity-controlled mode or voltage controlled mode. The reaction products are investigated by electron microscopy, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy, and Raman spectroscopy to study the possible pathway of oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). This protocol demonstrates a systematic and efficient arrangement of routine tests of the aprotic Li-O2 battery, including the electrochemical test and characterization of battery materials.

Protocol of Electrochemical Test and Characterization of Aprotic Li-O2 Battery

A protocol for the electrochemical testing of an aprotic Li-O2 battery with the preparation of electrodes and electrolytes and an introduction of the frequently used methods of characterization is presented here.

Protocollo di elettrochimica di test e caratterizzazione di aprotico Li-O<sub&gt; 2</sub&gt; Batteria

We demonstrate a method for electrochemical testing of an aprotic Li-O2 battery. An aprotic Li-O2 battery is made of a Li-metal anode, an aprotic ...

Accessing Valuable Ligand Supports for Transition Metals: A Modified, Intermediate Scale Preparation of 1,2,3,4,5-Pentamethylcyclopentadiene

A reliable, intermediate scale preparation of 1,2,3,4,5-pentamethylcyclopentadiene (Cp*H) is presented, based on modifications of existing protocols that derive from initial 2-bromo-2-butene lithiation followed by acid mediated dienol cyclization. The revised synthesis and purification of the ligand avoids the use of mechanical stirring while still permitting access to significant quantities (39 g) of Cp*H in good yield (58%). The procedure offers other additional benefits, including a more controlled quench of excess lithium during the production of the intermediate heptadienols and a simplified isolation of Cp*H of sufficient purity for metallation with transition metals. The ligand was subsequently used to synthesize [Cp*MCl2]2 complexes of both iridium and ruthenium to demonstrate the utility of the Cp*H prepared and purified by our method. The procedure outlined herein affords substantial quantities of a ubiquitous ancillary ligand support used in organometallic chemistry while minimizing the need for specialized laboratory equipment, thus providing a simpler and more accessible entry point into the chemistry of 1,2,3,4,5-pentamethylcyclopentadiene.

Reliable, intermediate scale preparation of 1,2,3,4,5-pentamethylcyclopentadiene (Cp*H) is presented. The revised protocol for the synthesis and purification of the ligand minimizes the need for specialized laboratory equipment while simplifying reaction workups and product purification. Use of Cp*H in the synthesis of [Cp*MCl2]2 complexes (M = Ru, Ir) is also described.

Accesso prezioso Ligand Supporti per metalli di transizione: una versione modificata, Intermedio Scala Preparazione di 1,2,3,4,5-Pentamethylcyclopentadiene

A reliable, intermediate scale preparation of 1,2,3,4,5-pentamethylcyclopentadiene (Cp*H) is presented, based on modifications of existing protocols that ...

A Two-Step Protocol for Umpolung Functionalization of Ketones Via Enolonium Species

&#945;-Functionalization of ketones via umpolung of enolates by hypervalent iodine reagents is an important concept in synthetic organic chemistry. Recently, we have developed a two-step strategy for ketone enolate umpolung that has enabled the development of methods for chlorination, azidation, and amination using azoles. In addition, we have developed C-C bond&#8211;forming arylation and allylation reactions. At the heart of these methods is the preparation of the intermediate and highly reactive enolonium species prior to addition of a reactive nucleophile. This strategy is thus reminiscent of the preparation and use of metal enolates in classical synthetic chemistry. This strategy allows the use of nucleophiles that would otherwise be incompatible with the strongly oxidizing hypervalent iodine reagents. In this paper we present a detailed protocol for chlorination, azidation, N-heteroarylation, arylation, and allylation. The products include motifs prevalent in medicinally active products. This article will greatly assist others in using these methods.

A two step one-pot protocol for the umpolung of ketone enolates to enolonium species and addition of a nucleophile to the &#945;-position is described. Nucleophiles include chloride, azide, azoles, allyl-silanes, and aromatic compounds.

Un protocollo in due fasi per Umpolung funzionalizzazione di chetoni Via Enolonium le specie

&#945;-Functionalization of ketones via umpolung of enolates by hypervalent iodine reagents is an important concept in synthetic organic chemistry. ...

Efficient Synthesis of All-Carbon Quaternary Centers via the Conjugate Addition of Functionalized Monoorganozinc Bromides

The conjugate addition of organometallic reagents to &#945;,&#946;-unsaturated carbonyls represents an important method to generate C&#8211;C bonds in the preparation of all-carbon quaternary centers. Though conjugate additions of organometallic reagents are typically performed utilizing highly reactive organolithium or Grignard reagents, organozinc reagents have garnered attention for their enhanced chemoselectivity and mild reactivity. Despite numerous recent advances with more reactive diorganozinc and mixed diorganozinc reagents, the generation of all-carbon quaternary centers via the conjugate addition of functionalized monoorganozinc reagents remains a challenge. This protocol details a convenient and mild &#8220;one-pot&#8221; preparation and copper mediated conjugate addition of functionalized monoorganozinc bromides to cyclic &#945;,&#946;-unsaturated carbonyls to afford a broad scope of all-carbon quaternary centers in generally excellent yield and diastereoselectivity. Key to the development of this technology is the utilization of DMA as a reaction solvent with TMSCl as a Lewis acid. Notable advantages to this methodology include the operational simplicity of the organozinc reagent preparation afforded by the utilization of DMA as a solvent, as well as an efficient conjugate addition mediated by various Cu(I) and Cu(II) salts. Moreover, an intermediate silyl enol ether can be isolated utilizing a modified workup procedure. The substrate scope is limited to cyclic unsaturated ketones, and the conjugate addition is impeded by stabilized (e.g., allyl, enolate, homoenolate) and sterically encumbered (e.g., neopentyl, o-aryl) monoorganozinc reagents. Conjugate additions to five- and seven-membered rings were effective, albeit in lower yields compared with six-membered ring substrates.

A simple and practical protocol for the efficient conjugate addition of functionalized monoorganozinc bromides to cyclic &#945;,&#946;-unsaturated carbonyls to furnish all-carbon quaternary centers was developed.

Sintesi efficiente dei centri quaternari All-Carbon tramite l'aggiunta di coniugato di Monoorganozinc di bromide funzionalizzati

The conjugate addition of organometallic reagents to &#945;,&#946;-unsaturated carbonyls represents an important method to generate C&#8211;C bonds in the ...

n-Butyllithium Titration

Source: Vy M. Dong and Diane Le, Department of Chemistry, University of California, Irvine, CA
This experiment will demonstrate a simple technique to titrate and obtain an accurate concentration of the organolithium reagent, n-butyllithium (n-BuLi). Organolithium reagents are extremely air- and moisture-sensitive and proper care must be taken to maintain the quality of the reagent so that it may be used successfully in a reaction. The n-BuLi titration experiments should be performed regularly to obtain accurate concentrations prior to use in a chemical reaction. Subsequently, we will demonstrate the addition of the titrated n-BuLi to benzaldehyde.

Determining n-Butyllithium Concentration by Titration

Titolazione di n-butillitio

Source: Vy M. Dong and Diane Le, Department of Chemistry, University of California, Irvine, CA
This experiment will demonstrate a simple technique to ...

Didattica

JoVE Science Education

Chimica organica II

Organocatalysis

Source: Vy M. Dong and Faben Cruz, Department of Chemistry, University of California, Irvine, CA
This experiment will demonstrate the concept of organocatalysis by illustrating the proper setup of a reaction that utilizes enamine catalysis. Organocatalysis is a form of catalysis that uses substoichiometric amounts of small organic molecules to accelerate reactions. This type of catalysis is complementary to other forms of catalysis such as transition metal or biocatalysis. Transition metal catalysis involves transition metals as catalysts and biocatalysis uses enzymes as catalysts. Some advantages of organocatalysis include the low toxicity and cost of the organocatalysts in comparison to many metal catalysts. In addition, most organocatalysts are not sensitive to air and moisture, unlike metal catalysts. In contrast to enzymes found in living organisms, the small molecules that act as organocatalysts are typically easy to access. Furthermore, organocatalysis offers complementary and new reactivity not observed with other forms of catalysis.

Organocatalysis: Principles and Applications

Organocatalisi

Source: Vy M. Dong and Faben Cruz, Department of Chemistry, University of California, Irvine, CA
This experiment will demonstrate the concept of ...

Acid Halides to Alcohols: LiAlH4 Reduction

Acid halides are reduced to alcohols in the presence of a strong reducing agent like lithium aluminum hydride.
The mechanism proceeds in three steps. First, the nucleophilic hydride ion attacks the carbonyl carbon of the acid halide to form a tetrahedral intermediate. Next, the carbonyl group is re-formed, and the halide ion departs as a leaving group, generating an aldehyde. A second nucleophilic attack by the hydride yields an alkoxide ion, which, upon protonation, gives a primary alcohol as the final product.
<img alt="Organic reaction mechanism diagram, illustrating nucleophilic substitution using AlCl3 catalyst." src="/files/ftp_upload/12364/12364_PT_Figure_1.svg" style="text-align: center; height: 200px;" data-altupdatedat="1747908711000" data-alt="Figure1">
However, it is possible to stop the reaction at the aldehyde by using a milder reducing agent like diisobutylaluminum hydride or lithium tri(t-butoxy)aluminum hydride.

Acid Halides to Alcohols: LiAlH4 Reduction

Alogenuri acidi in alcoli: Riduzione LiAlH4

Acid halides are reduced to alcohols in the presence of a strong reducing agent like lithium aluminum hydride.
The mechanism proceeds in three steps. ...

JoVE Core

Chimica Organica

Unità 1

Carboxylic Acid Derivatives

TERMINI E CONCETTI CHIAVE

Acid Halides to Alcohols: Grignard Reaction

Organomagnesium halides, commonly known as Grignard reagents, convert acid halides to tertiary alcohols. The reaction requires two equivalents of the Grignard reagent and proceeds via a ketone intermediate.
Grignard reagents are a source of carbanions and function as nucleophiles. The mechanism begins with the nucleophilic attack by the carbanion at the carbonyl carbon of the acid halide to form a tetrahedral intermediate. Next, the carbonyl group is re-formed, and the halide ion departs, forming a ketone. The addition of another equivalent of the carbanion generates a tertiary alkoxide ion. Protonation of the alkoxide gives a tertiary alcohol as the final product.
<img alt="Figure1" src="/files/ftp_upload/12827/12827_PT_Figure_1.svg" style="text-align: center; height: 225px;" />

Alogenuri acidi in alcoli: reazione di Grignard

Organomagnesium halides, commonly known as Grignard reagents, convert acid halides to tertiary alcohols. The reaction requires two equivalents of the ...

Un protocollo per reazioni sicuro litiazione Utilizzando organolitio Reagenti

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