Name: a scalable balz-schiemann reaction protocol in a continuous flow reactor
Uploaded: 2023-02-10T12:55:00
Description: Watch this Scientific Journal Video about A Scalable Balz-Schiemann Reaction Protocol in a Continuous Flow Reactor at JoVE.com

We would like to thank the support of Shenzhen Science and Technology Program (Grant No. KQTD20190929172447117).

CAUTION: Carefully check the properties and toxicities of the chemicals described here for the appropriate chemical handling of the relevant material as per the material safety data sheets (MSDS). Some of the chemicals used are detrimental to health, and special care must be taken. Avoid inhalation and contact with skin of these materials. Please wear the proper PPE during the whole process.
1. Preparation of feeds for continuous flow protocol
<ol>
	<li>Purchase BF3</su...

<ol>
	<li>Alexander, J. C., Stephen, G. D., Paul, M. R., James, E. T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Beyond+the+Balz-Schiemann+reaction:+The+utility+of+Tetrafluoroborates+and+Boron+Trifluoride+as+nucleophilic+fluoride+sources.">Beyond the Balz-Schiemann reaction: The utility of Tetrafluoroborates and Boron Trifluoride as nucleophilic fluoride sources.</a> Chemical Reviews. 115 (2), 566-611 (2014).</li><li>Mo, F., Qiu, D., Zhang, L., Wang, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Recent+development+of+Aryl+Diazonium+chemistry+for+the+derivatization+of+aromatic+compounds.">Recent development of Aryl Diazonium chemistry for the derivatization of aromatic compounds.</a> Chemical Reviews. 121 (10), 5741-5829 (2021).</li><li>Riccardo, P., Maurizio, B., Alessandra, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Flow+chemistry:+Recent+developments+in+the+synthesis+of+pharmaceutical+products.">Flow chemistry: Recent developments in the synthesis of pharmaceutical products.</a> Organic Process Research &amp; Development. 20 (1), 2-25 (2016).</li><li>Ball, N. D., Sanford, M. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Synthesis+and+reactivity+of+a+Mono-&#963;-aryl+Palladium(iv)+fluoride+complex.">Synthesis and reactivity of a Mono-&#963;-aryl Palladium(iv) fluoride complex.</a> Journal of the American Chemical Society. 131 (11), 3796-3797 (2009).</li><li>Griffete, N., Herbst, F., Pinson, J., Ammar, S., Mangeney, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Preparation+of+water-soluble+magnetic+nanocrystals+using+aryl+diazonium+salt+chemistry.">Preparation of water-soluble magnetic nanocrystals using aryl diazonium salt chemistry.</a> Journal of the American Chemical Society. 133 (6), 1646 (2011).</li><li>Stefan, A., Gunther, S., Matthew, J. F., Heinz, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+one-pot+Diazotation-Fluorodediazoniation+reaction+and+fluorine+gas+for+the+production+of+fluoronaphthyridines.">A one-pot Diazotation-Fluorodediazoniation reaction and fluorine gas for the production of fluoronaphthyridines.</a> Organic Process Research &amp; Development. 18 (8), 993-1001 (2014).</li><li>Carl, T., Alexandre, L., Rajeev, S. B., R&#233;jean, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Concise+and+efficient+synthesis+of+4-Fluoro-1H-pyrrolo[2,3-b]pyridine.">Concise and efficient synthesis of 4-Fluoro-1H-pyrrolo[2,3-b]pyridine.</a> Organic Letters. 5 (26), 5023-5025 (2003).</li><li>Nicolas, O., Erwan, L. G., Fran&#231;ois, X. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Handling+diazonium+salts+in+flow+for+organic+and+material+chemistry.">Handling diazonium salts in flow for organic and material chemistry.</a> Organic Chemistry Frontiers. 2 (5), 590-614 (2015).</li><li>Fortt, R., Wootton, R., Mello, A. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Continuous-flow+generation+of+anhydrous+diazonium+species:+Monolithic+microfluidic+reactors+for+the+chemistry+of+unstable+intermediates.">Continuous-flow generation of anhydrous diazonium species: Monolithic microfluidic reactors for the chemistry of unstable intermediates.</a> Organic Process Research &amp; Development. 7 (5), 762-768 (2003).</li><li>Liu, Y., Zeng, C., Wang, C., Zhang, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Continuous+diazotization+of+aromatic+amines+with+high+acid+and+sodium+nitrite+concentrations+in+microreactors.">Continuous diazotization of aromatic amines with high acid and sodium nitrite concentrations in microreactors.</a> Journal of Flow Chemistry. 8 (3-4), 139-146 (2018).</li><li>Arlene, B., Aisling, L., Alex, C. P., Marcus, B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Forgotten+and+forbidden+chemical+reactions+revitalised+through+continuous+flow+technology.">Forgotten and forbidden chemical reactions revitalised through continuous flow technology.</a> Organic &amp; Biomolecular Chemistry. 19 (36), 7737-7753 (2021).</li><li>Jianli, C., Xiaoxuan, X., Jiming, L., Zhiqun, Y., Weike, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Revisiting+aromatic+diazotization+and+aryl+diazonium+salts+in+continuous+flow:+highlighted+research+during+2001-2021.">Revisiting aromatic diazotization and aryl diazonium salts in continuous flow: highlighted research during 2001-2021.</a> Reaction Chemistry &amp; Engineering. 7 (6), 1247-1275 (2022).</li><li>Li, B., Widlicka, D., Boucher, S., Hayward, C., Young, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Telescoped+flow+process+for+the+syntheses+of+N-Aryl+pyrazoles.">Telescoped flow process for the syntheses of N-Aryl pyrazoles.</a> Organic Process Research &amp; Development. 16 (12), 2031-2035 (2012).</li><li>Zhi, Y., Yan, L., Chuan, Y., Wei-ke, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Continuous+flow+reactor+for+Balz-Schiemann+reaction:+a+new+procedure+for+the+preparation+of+aromatic+fluorides.">Continuous flow reactor for Balz-Schiemann reaction: a new procedure for the preparation of aromatic fluorides.</a> Tetrahedron Letters. 54 (10), 1261-1263 (2013).</li><li>Li, B., Steven, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Development+of+flow+processes+for+the+syntheses+of+N-aryl+pyrazoles+and+diethyl+cyclopropane-cis-1,2-dicarboxylate.">Development of flow processes for the syntheses of N-aryl pyrazoles and diethyl cyclopropane-cis-1,2-dicarboxylate.</a> Acs Symposium. 1181 (14), 383-402 (2014).</li><li>Zhiqun, Y., Hei, D., Xiaoxuan, X., Jiming, L., Weike, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Continuous-Flow+diazotization+for+efficient+synthesis+of+Methyl+2-(Chlorosulfonyl)benzoate:+An+example+of+inhibiting+parallel+side+reactions.">Continuous-Flow diazotization for efficient synthesis of Methyl 2-(Chlorosulfonyl)benzoate: An example of inhibiting parallel side reactions.</a> Organic Process Research &amp; Development. 20 (12), 2116-2123 (2016).</li><li>Jiming, L., 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=Continuous-flow+double+diazotization+for+the+synthesis+of+m-difluorobenzene+via+Balz-Schiemann+reaction.">Continuous-flow double diazotization for the synthesis of m-difluorobenzene via Balz-Schiemann reaction.</a> Journal of Flow Chemistry. 10 (4), 589-596 (2020).</li><li>Zhiqun, Y., Yanwen, L., Chuanming, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+Continuous+kilogram-scale+process+for+the+manufacture+of+o-Difluorobenzene.">A Continuous kilogram-scale process for the manufacture of o-Difluorobenzene.</a> Organic Process Research &amp; Development. 16 (10), 1669-1672 (2012).</li><li>Hathaniel, H. P., Timothyl, J. S., Stephen, L. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Rapid+synthesis+of+aryl+fluorides+in+continuous+flow+through+the+Balz-Schiemann+reaction.">Rapid synthesis of aryl fluorides in continuous flow through the Balz-Schiemann reaction.</a> Angewandte Chemie International Edition. 55 (39), 11907-11911 (2016).</li><li>David, R. S., Fran&#231;ois, L., William, J. M., John, R. N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=An+improved+Balz-Schiemann+reaction+enabled+by+ionic+liquids+and+continuous+processing.">An improved Balz-Schiemann reaction enabled by ionic liquids and continuous processing.</a> Tetrahedron. 75 (32), 4261-4265 (2019).</li><li>He, G., Wang, D., Liang, C., Chen, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Theoretical+study+on+thermal+safety+of+preparing+fluorobenzene+by+the+Balz-Schiemann+reaction+and+fluorodenitration+reaction.">Theoretical study on thermal safety of preparing fluorobenzene by the Balz-Schiemann reaction and fluorodenitration reaction.</a> Journal of Chemical Health &amp; Safety. 20 (1), 30-34 (2013).</li><li>Schotten, C., Leprevost, S. K., Yong, L. M., Hughes, C. E., Browne, D. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Comparison+of+the+thermal+stabilities+of+diazonium+salts+and+their+corresponding+triazenes.">Comparison of the thermal stabilities of diazonium salts and their corresponding triazenes.</a> Organic Process Research &amp; Development. 24 (10), 2336-2341 (2020).</li><li>Sharma, Y., Nikam, A. V., Kulkarni, A. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Telescoped+sequence+of+exothermic+and+endothermic+reactions+in+multistep+flow+synthesis.">Telescoped sequence of exothermic and endothermic reactions in multistep flow synthesis.</a> Organic Process Research &amp; Development. 23 (2), 170-176 (2018).</li></ol>

A continuous flow protocol of the Balz-Schiemann reaction has been successfully performed through a combination of a micro-channel flow reactor and a dynamically mixed flow reactor. This strategy features several advantages compared with the batch process: (i) it is safer with controlled diazonium salt formation; (ii) it is more amenable to a higher reaction temperature, 10 &#176;C versus -20 &#176;C; and (iii) it is more efficient without isolation of the diazonium intermediate, two steps in one continuous process. Spec...

The Balz&#8722;Schiemann reaction is a classic method for replacing the diazonium group with fluorine by heating ArN2+BF4&#8722; without a solvent1,2. The reaction can be applied to a wide variety of aryl amine substrates, making it a generally applicable approach to synthesize aryl amines, which are frequently utilized for advanced intermediates in pharmaceutical or fine chemical industries2,3. Unfortunately, harsh reaction conditions are often employed in the Balz-Schiemann reaction, and the reaction generates potentially explosive aryldiazonium salts4,5,6,7,8. Other challenges associated with the Balz-Schiemann reaction are the formation of side products during the thermal decomposition process and its modest yield. In order to minimize the side product formation, thermal dediazotization can be performed in nonpolar solvents or using neat diazonium salts9,10, which means the aryldizanium salts should be isolated. However, the diazotization of aromatic amines is generally exothermic and fast, which is a risk associated with the isolation of the explosive diazonium salt, especially in large-scale production.
In recent years, continuous flow synthesis technologies have helped to overcome the safety issues associated with the Balz-Schiemann reactions11,12. Although there are some examples of diazotization of aromatic amines using continuous microreactors for deamination at positions para to aryl-chlorides, 5-azodyes, and chlorosulfonylation, these contributions were only reported on a laboratory scale13,14,15,16,17. Yu and co-workers developed a continuous kilo-scale process for the synthesis of aryl fluorides18. They have shown that the improved heat and mass transfer of a flow system would benefit both the diazotization process and the fluorination process. However, they used two separate continuous flow reactors; therefore, the diazotization and thermal decomposition processes were investigated separately. A further contribution was published by Buchwald and co-workers19, where they presented a hypothesis that if the product formation was proceeding through the SN2Ar or SN1 mechanism, then the yield may be improved by increasing the concentration of the fluoride source. They developed a flow-to-continuous stirred tank reactor (CSTR) hybrid process in which the diazonium salts were generated and consumed in a continuous and controlled manner. However, the heat and mass transfer efficiency of a CSTR is not good enough as a tube flow reactor, and a large CSTR cannot be expected to be used with explosive diazonium salts in large-scale production. Subsequently, Naber and co-workers developed a fully continuous flow process to synthesize 2-fluoroadenine from 2,6-diaminopurine20. They found that the exothermic Balz-Schiemann reaction was easier to control in a continuous flow manner and that the tubing dimensions of the flow reactor would influence the heat transfer and temperature control aspects - a tube reactor with large dimensions shows a positive improvement. However, the tube reactor&#39;s scaled-up effect will be notable, and the poor solubility of the polar aryl diazonium salt in organic solvents is troublesome for static tube reactors, which face a blockage risk. Even though remarkable progress has been established, there are still some problems associated with large-scale Balz-Schiemann reactions. Thus, the development of an improved protocol that would provide rapid and scalable access to aryl-fluorides is still significant.
The challenges associated with large-scale Balz&#8722;Schiemann reaction processing include the following:(i)the thermal instability of an accumulated diazonium intermediate over a short time period21; (ii) the long processing times; and (iii) the non-uniform heating or the presence of water in the diazonium fluoroborate, leading to uncontrollable thermal decomposition and increased by-product formation22,23. Additionally (iv) in some flow processing modes, an isolation of the diazonium intermediate is still required due to its low solubility14, which is then fed into a uncontrolled rate decomposition reaction. The risk of handling a large quantity of in-line diazonium salt cannot be avoided. Thus, there is significant benefit in developing a continuous flow strategy to solve the abovementioned problems and avoid both the accumulation and the isolation of the unstable diazonium species.
In order to establish an inherently safer production of chemicals in pharmaceuticals, our group has focused on multi-step continuous flow technology. In this work, we apply this technology to the Balz&#8722;Schiemann synthesis on a kilogram scale in a way that eliminates the isolation of aryl diazonium salts, while facilitating efficient fluorination.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>2-Methylpyridin-3-amine</td>
			<td>Raffles Pharmatech Co. Ltd</td>
			<td>C2021236-SM5-H221538-008</td>
			<td>HPLC: &#62;98%, Water by KF &#8804;0.5%</td>
		</tr>
		<tr>
			<td>316L piston constant flow pump</td>
			<td>Oushisheng (Beijing) Technology Co.,Ltd</td>
			<td>DP-S200</td>
			<td></td>
		</tr>
		<tr>
			<td>BF3.Et2O</td>
			<td>Whmall.com</td>
			<td>B802217</td>
			<td></td>
		</tr>
		<tr>
			<td>Citric acid</td>
			<td>Titan Technology Co., Ltd</td>
			<td>G83162G</td>
			<td></td>
		</tr>
		<tr>
			<td>con.HCl</td>
			<td>Foshang Xilong Huagong</td>
			<td>1270110101601M&#160;&#160;</td>
			<td></td>
		</tr>
		<tr>
			<td>Dynamically mixed flow reactor</td>
			<td>Autichem Ltd</td>
			<td>DM500</td>
			<td>316L reator with 500 mL of internal volume</td>
		</tr>
		<tr>
			<td>Heptane</td>
			<td>Shenzhen Huachang</td>
			<td>HCH606</td>
			<td>Water by KF &#8804;0.5%</td>
		</tr>
		<tr>
			<td>Micro flow reactor</td>
			<td>Corning Reactor Technology Co.,Ltd</td>
			<td>G1 Galss AFR</td>
			<td>Glass module with 9 mL of internal volume</td>
		</tr>
		<tr>
			<td>PTFE piston constant flow pump</td>
			<td>Sanotac China</td>
			<td>MPF1002C</td>
			<td></td>
		</tr>
		<tr>
			<td>Sodium hydroxide</td>
			<td>Foshang Xilong Huagong</td>
			<td>1010310101700</td>
			<td></td>
		</tr>
		<tr>
			<td>tert-Butyl methyl ether</td>
			<td>Titan Technology Co., Ltd</td>
			<td>01153694</td>
			<td></td>
		</tr>
		<tr>
			<td>tert-Butyl nitrite</td>
			<td>Whmall.com</td>
			<td>XS22030900060</td>
			<td></td>
		</tr>
		<tr>
			<td>Tetrahydrofuran</td>
			<td>Titan Technology Co., Ltd</td>
			<td>1152930</td>
			<td>Water by KF &#8804;0.5%</td>
		</tr>
	</tbody>
</table>

a scalable balz-schiemann reaction protocol in a continuous flow reactor

The demand for aromatic fluorides is steadily increasing in the pharmaceutical and fine chemical industries. The Balz-Schiemann reaction is a straightforward strategy for preparing aryl fluorides from aryl amines, via the preparation and conversion of diazonium tetrafluoroborate intermediates. However, significant safety risks exist in handling the aryl diazonium salts when scaling up. In order to minimize the hazard, we present a continuous flow protocol that has been successfully performed at a kilogram scale that eliminates the isolation of aryl diazonium salts while facilitating efficient fluorination. The diazotization process was performed at 10 &#176;C with a residence time of 10 min, followed by a fluorination process at 60 &#176;C with a residence time of 5.4 s with about 70% yield. The reaction time has been dramatically reduced by introducing this multi-step continuous flow system.

The model reaction is shown in Figure 2. 2-Methylpyridin-3-amine (compound 1 in Figure 2) was chosen as the starting material to prepare 2-methylpyridin-3-fluoride (compound 3 in Figure 2) via the Balz-Schiemann reaction. The experimental parameters were systematically investigated by varying reaction temperature and residence time. Feed A is 0.35 M 2-methylpyridin-3-amine in THF. Feed B is pure BF3&#183;Et2...

Watch this Scientific Journal Video about A Scalable Balz-Schiemann Reaction Protocol in a Continuous Flow Reactor at JoVE.com

A Scalable Balz-Schiemann Reaction Protocol in a Continuous Flow Reactor

A detailed scalable continuous flow protocol is presented to synthesize an aryl fluoride from an aryl amine through the Balz-Schiemann reaction.

The demand for aromatic fluorides is steadily increasing in the pharmaceutical and fine chemical industries. The Balz-Schiemann reaction is a ...

Our protocol is a straightforward strategy for preparing aryl fluoride from aryl amine in a continuous flow manner. The is safe, controllable, and efficient. This measure could provide an insight into the fine chemical and the pharmaceutical industry, which could make a safe and a reliable process.Please be careful and attentive will performing this technique. First, read all the steps and figure out the details of operating before you try this technique. To perform the Balz-Schiemann reaction in a continuous flow system, prepare two modules of the microflow reactor with an internal reaction volume of nine milliliters, and one dynamic mixing tube reactor with an internal reaction volume of 500 milliliters.Also, prepare one constant flow pump with a PTFE pump head, and three constant flow pumps with the 316 L stainless steel pump head. Assemble the equipment as described in the manuscript. Check the mechanical integrity of all the connections between pumps, pipelines, and flow reactors before use.Set the flow rates of the pumps. Then set the jacket outlet, temperature of the premixing and diazonium salt formation zone at minus five degrees Celsius and the jacket outlet temperature of the thermal decomposition zone at 60 degrees Celsius to maintain the temperature regulation. To check equipment safety and leakage, first place the dosing pipeline of pumps A, B, C and D into the feed E bottle.And discharging pipeline into the waste collecting bottle. Then start the pumps and slowly regulate the back pressure up to three bars. Observe the stability of each pump and check all the joints, pipelines, and reactors for any solvent leakage.Also, check if the jacket inlet and outlet temperature of each zone and the current inlet pressure of each pump are within the target ranges. Then, stop pumps after 10 minutes of steady state equilibrium. To begin the reaction process, place the dosing pipeline's A, B, C and D into the corresponding feeds, and put the discharging pipeline into the waste collection bottle.Start pumps A and B simultaneously and record the time. Then start pump C after 30 seconds and pump D after 8 minutes. After 10 minutes of steady state equilibrium, place the discharging pipeline into the product collection vessel.Observe and record the temperature of each zone and the pressure of each pump. Once feed B pumping is complete, insert the dosing pipeline B into feed E.Then put the discharging pipeline into a waste collection bottle. And dosing pipeline's, A, C and D into the feed E bottle.Turn off pumps A, B, C, and D after 10 minutes of washing. A continuous flow reactor was successfully applied to the Balz-Schiemann reaction on a model substrate. The reaction temperature of the flow experiments was successfully controlled at 10 degrees Celsius with 70%crude product purity, which was higher than what was obtained in batch processing.Almost 98%of conversion was reached in 600 seconds of the resident's time. When the flow rate was 50 milliliters per minute in the diazotization zone, and 5.4 seconds in the thermal decomposition zone, at 100 milliliters per minute flow rate. Increasing the flow rate leaves a large amount of starting material in the reaction and reducing the flow rate may completely consume the starting material, but limit production efficiency.The crude product was further purified and analyzed using mass spectroscopy, proton-NMR and fluorine-NMR. It's important to show the reactors are pumps according to the chemical property and absorbability of substances, especially for those who highly or for those reactions with solid formation. Reactions that have a liquid effect and faster reaction rate can be carried out effectivity using a continuous flow system.In addition, it can cause reaction that may or may not result in the formation of a solid.

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Preparation and Use of Samarium Diiodide (SmI2) in Organic Synthesis: The Mechanistic Role of HMPA and Ni(II) Salts in the Samarium Barbier Reaction

Although initially considered an esoteric reagent, SmI2 has become a common tool for synthetic organic chemists. SmI2 is generated through the addition of molecular iodine to samarium metal in THF.1,2-3 It is a mild and selective single electron reductant and its versatility is a result of its ability to initiate a wide range of reductions including C-C bond-forming and cascade or sequential reactions. SmI2 can reduce a variety of functional groups including sulfoxides and sulfones, phosphine oxides, epoxides, alkyl and aryl halides, carbonyls, and conjugated double bonds.2-12 One of the fascinating features of SmI-2-mediated reactions is the ability to manipulate the outcome of reactions through the selective use of cosolvents or additives. In most instances, additives are essential in controlling the rate of reduction and the chemo- or stereoselectivity of reactions.13-14 Additives commonly utilized to fine tune the reactivity of SmI2 can be classified into three major groups: (1) Lewis bases (HMPA, other electron-donor ligands, chelating ethers, etc.), (2) proton sources (alcohols, water etc.), and (3) inorganic additives (Ni(acac)2, FeCl3, etc).3
Understanding the mechanism of SmI2 reactions and the role of the additives enables utilization of the full potential of the reagent in organic synthesis. The Sm-Barbier reaction is chosen to illustrate the synthetic importance and mechanistic role of two common additives: HMPA and Ni(II) in this reaction. The Sm-Barbier reaction is similar to the traditional Grignard reaction with the only difference being that the alkyl halide, carbonyl, and Sm reductant are mixed simultaneously in one pot.1,15 Examples of Sm-mediated Barbier reactions with a range of coupling partners have been reported,1,3,7,10,12 and have been utilized in key steps of the synthesis of large natural products.16,17 Previous studies on the effect of additives on SmI2 reactions have shown that HMPA enhances the reduction potential of SmI2 by coordinating to the samarium metal center, producing a more powerful,13-14,18 sterically encumbered reductant19-21 and in some cases playing an integral role in post electron-transfer steps facilitating subsequent bond-forming events.22 In the Sm-Barbier reaction, HMPA has been shown to additionally activate the alkyl halide by forming a complex in a pre-equilibrium step.23
Ni(II) salts are a catalytic additive used frequently in Sm-mediated transformations.24-27 Though critical for success, the mechanistic role of Ni(II) was not known in these reactions. Recently it has been shown that SmI2 reduces Ni(II) to Ni(0), and the reaction is then carried out through organometallic Ni(0) chemistry.28
These mechanistic studies highlight that although the same Barbier product is obtained, the use of different additives in the SmI2 reaction drastically alters the mechanistic pathway of the reaction. The protocol for running these SmI2-initiated reactions is described.

Preparation and Use of Samarium Diiodide SmI2 in Organic Synthesis: The Mechanistic Role of HMPA and NiII Salts in the Samarium Barbier Reaction

A straightforward procedure for the preparation of samarium diiodide (SmI2) in THF is described. The role of two main additives namely hexamethylphosphoramide (HMPA) and Ni(acac)2 in Sm mediated reactions is demonstrated in the Sm-Barbier reaction.

Although initially considered an esoteric reagent, SmI2 has become a common tool for synthetic organic chemists. SmI2 is generated through the addition of ...

Untargeted Metabolomics from Biological Sources Using Ultraperformance Liquid Chromatography-High Resolution Mass Spectrometry (UPLC-HRMS)

Here we present a workflow to analyze the metabolic profiles for biological samples of interest including; cells, serum, or tissue. The sample is first separated into polar and non-polar fractions by a liquid-liquid phase extraction, and partially purified to facilitate downstream analysis. Both aqueous (polar metabolites) and organic (non-polar metabolites) phases of the initial extraction are processed to survey a broad range of metabolites. Metabolites are separated by different liquid chromatography methods based upon their partition properties. In this method, we present microflow ultra-performance (UP)LC methods, but the protocol is scalable to higher flows and lower pressures. Introduction into the mass spectrometer can be through either general or compound optimized source conditions. Detection of a broad range of ions is carried out in full scan mode in both positive and negative mode over a broad m/z range using high resolution on a recently calibrated instrument. Label-free differential analysis is carried out on bioinformatics platforms. Applications of this approach include metabolic pathway screening, biomarker discovery, and drug development.

Untargeted Metabolomics from Biological Sources Using Ultraperformance Liquid Chromatography-High Resolution Mass Spectrometry UPLC-HRMS

Untargeted metabolomics provides a hypothesis generating snapshot of a metabolic profile. This protocol will demonstrate the extraction and analysis of metabolites from cells, serum, or tissue. A range of metabolites are surveyed using liquid-liquid phase extraction, microflow ultraperformance liquid chromatography/high-resolution mass spectrometry (UPLC-HRMS) coupled to differential analysis software.

Here we present a workflow to analyze the metabolic profiles for biological samples of interest including; cells, serum, or tissue. The sample is first ...

A Simple and Rapid Protocol for Measuring Neutral Lipids in Algal Cells Using Fluorescence

Algae are considered excellent candidates for renewable fuel sources due to their natural lipid storage capabilities. Robust monitoring of algal fermentation processes and screening for new oil-rich strains requires a fast and reliable protocol for determination of intracellular lipid content. Current practices rely largely on gravimetric methods to determine oil content, techniques developed decades ago that are time consuming and require large sample volumes. In this paper, Nile Red, a fluorescent dye that has been used to identify the presence of lipid bodies in numerous types of organisms, is incorporated into a simple, fast, and reliable protocol for measuring the neutral lipid content of Auxenochlorella protothecoides, a green alga. The method uses ethanol, a relatively mild solvent, to permeabilize the cell membrane before staining and a 96 well micro-plate to increase sample capacity during fluorescence intensity measurements. It has been designed with the specific application of monitoring bioprocess performance. Previously dried samples or live samples from a growing culture can be used in the assay.

A simple protocol to determine the neutral lipid content of algal cells using a Nile Red staining procedure is described. This time-saving technique offers an alternative to traditional gravimetric-based lipid quantification protocols. It has been designed for the specific application of monitoring bioprocess performance.

Algae are considered excellent candidates for renewable fuel sources due to their natural lipid storage capabilities. Robust monitoring of algal ...

Real-time Monitoring of Reactions Performed Using Continuous-flow Processing: The Preparation of 3-Acetylcoumarin as an Example

By using inline monitoring, it is possible to optimize reactions performed using continuous-flow processing in a simple and rapid way. It is also possible to ensure consistent product quality over time using this technique. We here show how to interface a commercially available flow unit with a Raman spectrometer. The Raman flow cell is placed after the back-pressure regulator, meaning that it can be operated at atmospheric pressure. In addition, the fact that the product stream passes through a length of tubing before entering the flow cell means that the material is at RT. It is important that the spectra are acquired under isothermal conditions since Raman signal intensity is temperature dependent. Having assembled the apparatus, we then show how to monitor a chemical reaction, the piperidine-catalyzed synthesis of 3-acetylcoumarin from salicylaldehyde and ethyl acetoacetate being used as an example. The reaction can be performed over a range of flow rates and temperatures, the in-situ monitoring tool being used to optimize conditions simply and easily.

Real-time monitoring allows for fast optimization of reactions performed using continuous-flow processing. Here the preparation of 3-acetylcoumarin is used as an example. The apparatus for performing in-situ Raman monitoring is described, as are the steps required to optimize the reaction.

By using inline monitoring, it is possible to optimize reactions performed using continuous-flow processing in a simple and rapid way. It is also possible ...

Post Column Derivatization Using Reaction Flow High Performance Liquid Chromatography Columns

A protocol for the use of reaction flow high performance liquid chromatography columns for methods employing post column derivatization (PCD) is presented. A major difficulty in adapting PCD to modern HPLC systems and columns is the need for large volume reaction coils that enable reagent mixing and then the derivatization reaction to take place. This large post column dead volume leads to band broadening, which results in a loss of observed separation efficiency and indeed detection in sensitivity. In reaction flow post column derivatization (RF-PCD) the derivatization reagent(s) are pumped against the flow of mobile phase into either one or two of the outer ports of the reaction flow column where it is mixed with column effluent inside a frit housed within the column end fitting. This technique allows for more efficient mixing of the column effluent and derivatization reagent(s) meaning that the volume of the reaction loops can be minimized or even eliminated altogether. It has been found that RF-PCD methods perform better than conventional PCD methods in terms of observed separation efficiency and signal to noise ratio. A further advantage of RF-PCD techniques is the ability to monitor effluent coming from the central port in its underivatized state. RF-PCD has currently been trialed on a relatively small range of post column reactions, however, there is currently no reason to suggest that RF-PCD could not be adapted to any existing one or two component (as long as both reagents are added at the same time) post column derivatization reaction.

A protocol for the use of reaction flow high performance liquid chromatography columns for methods employing post column derivatization (PCD) is presented.

A protocol for the use of reaction flow high performance liquid chromatography columns for methods employing post column derivatization (PCD) is ...

Synthesis and Exfoliation of Discotic Zirconium Phosphates to Obtain Colloidal Liquid Crystals

Due to their abundance in natural clay and potential applications in advanced materials, discotic nanoparticles are of interest to scientists and engineers. Growth of such anisotropic nanocrystals through a simple chemical method is a challenging task. In this study, we fabricate discotic nanodisks of zirconium phosphate [Zr(HPO4)2&#183;H2O] as a model material using hydrothermal, reflux and microwave-assisted methods. Growth of crystals is controlled by duration time, temperature, and concentration of reacting species. The novelty of the adopted methods is that discotic crystals of size ranging from hundred nanometers to few micrometers can be obtained while keeping the polydispersity well within control. The layered discotic crystals are converted to monolayers by exfoliation with tetra-(n)-butyl ammonium hydroxide [(C4H9)4NOH, TBAOH]. Exfoliated disks show isotropic and nematic liquid crystal phases. Size and polydispersity of disk suspensions is highly important in deciding their phase behavior.

A two dimensional model material of discotic zirconium phosphate was developed. The inorganic crystal with lamellar structure was synthesized by hydrothermal, reflux, and microwave-assisted methods. On exfoliation with organic molecules, layered crystals can be converted to monolayers, and nematic liquid crystal phase was formed at sufficient concentration of monolayers.

Due to their abundance in natural clay and potential applications in advanced materials, discotic nanoparticles are of interest to scientists and ...

A Protocol for Safe Lithiation Reactions Using Organolithium Reagents

Organolithium reagents are powerful tools in the synthetic chemist&#39;s toolbox. However, the extreme pyrophoric nature of the most reactive reagents warrants proper technique, thorough training, and proper personal protective equipment. To aid in the training of researchers using organolithium reagents, a thorough, step-by-step protocol for the safe and effective use of tert-butyllithium on an inert gas line or within a glovebox is described. As a model reaction, preparation of lithium tert-butyl amide by the reaction of tert-butyl amine with one equivalent of tert-butyl lithium is presented.

The safe and proper use of organolithium reagents is described.

Organolithium reagents are powerful tools in the synthetic chemist&#39;s toolbox. However, the extreme pyrophoric nature of the most reactive reagents ...

A Protocol for Electrochemical Evaluations and State of Charge Diagnostics of a Symmetric Organic Redox Flow Battery

Redox flow batteries have been considered as one of the most promising stationary energy storage solutions for improving the reliability of the power grid and deployment of renewable energy technologies. Among the many flow battery chemistries, non-aqueous flow batteries have the potential to achieve high energy density because of the broad voltage windows of non-aqueous electrolytes. However, significant technical hurdles exist currently limiting non-aqueous flow batteries to demonstrate their full potential, such as low redox concentrations, low operating currents, under-explored battery status monitoring, etc. In an attempt to address these limitations, we recently reported a non-aqueous flow battery based on a highly soluble, redox-active organic nitronyl nitroxide radical compound, 2-phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (PTIO). This redox material exhibits an ambipolar electrochemical property, and therefore can serve as both anolyte and catholyte redox materials to form a symmetric flow battery chemistry. Moreover, we demonstrated that Fourier transform infrared (FTIR) spectroscopy could measure the PTIO concentrations during the PTIO flow battery cycling and offer reasonably accurate detection of the battery state of charge (SOC), as cross-validated by electron spin resonance (ESR) measurements. Herein we present a video protocol for the electrochemical evaluation and SOC diagnosis of the PTIO symmetric flow battery. With a detailed description, we experimentally demonstrated the route to achieve such purposes. This protocol aims to spark more interests and insights on the safety and reliability in the field of non-aqueous redox flow batteries.

We present the protocols for electrochemically evaluating a symmetric non-aqueous organic redox flow battery and for diagnosing its state of charge using FTIR.

Redox flow batteries have been considered as one of the most promising stationary energy storage solutions for improving the reliability of the power grid ...

Continuous Flow Chemistry: Reaction of Diphenyldiazomethane with p-Nitrobenzoic Acid

Continuous flow technology has been identified as instrumental for its environmental and economic advantages leveraging superior mixing, heat transfer and cost savings through the &#34;scaling out&#34; strategy as opposed to the traditional &#34;scaling up&#34;. Herein, we report the reaction of diphenyldiazomethane with p-nitrobenzoic acid in both batch and flow modes. To effectively transfer the reaction from batch to flow mode, it is essential to first conduct the reaction in batch. As a consequence, the reaction of diphenyldiazomethane was first studied in batch as a function of temperature, reaction time, and concentration to obtain kinetic information and process parameters. The glass flow reactor set-up is described and combines two types of reaction modules with &#34;mixing&#34; and &#34;linear&#34; microstructures. Finally, the reaction of diphenyldiazomethane with p-nitrobenzoic acid was successfully conducted in the flow reactor, with up to 95% conversion of the diphenyldiazomethane in 11 min. This proof of concept reaction aims to provide insight for scientists to consider flow technology&#39;s competitiveness, sustainability, and versatility in their research.

Continuous Flow Chemistry: Reaction of Diphenyldiazomethane with p-Nitrobenzoic Acid

Flow chemistry carries environmental and economic advantages by leveraging superior mixing, heat transfer and cost benefits. Herein, we provide a blueprint to transfer chemical processes from batch to flow mode. The reaction of diphenyldiazomethane (DDM) with p-nitrobenzoic acid, conducted in batch and flow, was chosen for proof of concept.

Continuous flow technology has been identified as instrumental for its environmental and economic advantages leveraging superior mixing, heat transfer and ...

Combustion Chemistry of Fuels: Quantitative Speciation Data Obtained from an Atmospheric High-temperature Flow Reactor with Coupled Molecular-beam Mass Spectrometer

This manuscript describes a high-temperature flow reactor experiment coupled to the powerful molecular beam mass spectrometry (MBMS) technique. This flexible tool offers a detailed observation of chemical gas-phase kinetics in reacting flows under well-controlled conditions. The vast range of operating conditions available in a laminar flow reactor enables access to extraordinary combustion applications that are typically not achievable by flame experiments. These include rich conditions at high temperatures relevant for gasification processes, the peroxy chemistry governing the low temperature oxidation regime or investigations of complex technical fuels. The presented setup allows measurements of quantitative speciation data for reaction model validation of combustion, gasification and pyrolysis processes, while enabling a systematic general understanding of the reaction chemistry. Validation of kinetic reaction models is generally performed by investigating combustion processes of pure compounds. The flow reactor has been enhanced to be suitable for technical fuels (e.g. multi-component mixtures like Jet A-1) to allow for phenomenological analysis of occurring combustion intermediates like soot precursors or pollutants. The controlled and comparable boundary conditions provided by the experimental design allow for predictions of pollutant formation tendencies. Cold reactants are fed premixed into the reactor that are highly diluted (in around 99 vol% in Ar) in order to suppress self-sustaining combustion reactions. The laminar flowing reactant mixture passes through a known temperature field, while the gas composition is determined at the reactors exhaust as a function of the oven temperature. The flow reactor is operated at atmospheric pressures with temperatures up to 1,800 K. The measurements themselves are performed by decreasing the temperature monotonically at a rate of -200 K/h. With the sensitive MBMS technique, detailed speciation data is acquired and quantified for almost all chemical species in the reactive process, including radical species.

An investigation of the oxidative combustion chemistry of novel biofuels, fuel components, or jet fuels by comparison of quantitative speciation data is presented. The data can be used for kinetic model validation and enables fuel assessment strategies.This manuscript describes the atmospheric high-temperature flow reactor and demonstrates its capabilities.

This manuscript describes a high-temperature flow reactor experiment coupled to the powerful molecular beam mass spectrometry (MBMS) technique. This ...