This work was supported by the Universit&#233; libre de Bruxelles (ULB), the F&#233;d&#233;ration Wallonie-Bruxelles (ARC Consolidator 2014-2019), Innoviris (project PhotoCop), and the COST action CM1202. H.B. acknowledges the Fonds pour la formation &#224; la Recherche dans l&#8217;Industrie et dans l&#8217;Agriculture (F.R.I.A.) for graduate fellowship. C.T. acknowledges the Fonds de la Recherche Scientifique (FNRS) for research fellowship.

1. Synthesis of [(DPEPhos)(bcp)Cu]PF6
<ol>
	<li>Add 3.73 g (10.00 mmol) of tetrakisacetonitrile copper(I) hexafluorophosphate and 5.39 g (10.00 mmol) of DPEPhos to a 2 L round bottom flask equipped with a magnetic stir bar.</li>
	<li>Fit the round bottom flask with a three neck vacuum adapter connected to a vacuum line and an argon line.</li>
	<li>Evacuate the flask under vacuum and backfill with argon three times. Replace the three neck vacuum adapter by a rubber septum. 
	NOTE: The reaction can be performed under air with slightly reduced efficiency (see discussion section for details).</li>
	<li>Add 800 mL of dry dichloromethane. 
	NOTE: Dichloromethane is freshly distilled from CaH2. The reaction can also be performed in regular dichloromethane (99.8%) with similar efficiency (see discussion section for details).</li>
	<li>Stir the reaction mixture for 2 h in the dark (reaction flask covered with aluminum foil) at room temperature (23-25 &#186;C)&#160;under an argon atmosphere.</li>
	<li>Add 3.60 g (10.00 mmol) of bcp to a 500 mL round bottom flask equipped with a magnetic stir bar.</li>
	<li>Fit the round bottom flask with a three neck vacuum adapter connected to a vacuum line and an argon line.</li>
	<li>Evacuate the flask under vacuum and backfill with argon three times. Replace the three neck vacuum adapter by a rubber septum.</li>
	<li>Add 200 mL of dry dichloromethane and gently stir the suspension until complete dissolution of the bcp.</li>
	<li>Add the solution of bcp in dichloromethane to the reaction mixture using a cannula.</li>
	<li>Stir for an additional hour in the dark (reaction flask covered with aluminum foil) at room temperature (23-25&#160;&#186;C) under an argon atmosphere.</li>
	<li>Filter the mixture through a pad of Celite, wash with ca. 100 mL of dichloromethane and concentrate the filtrate to ca. 50-100 mL under reduced pressure.</li>
	<li>Add the concentrate dropwise to 1 L of diethyl ether using an addition funnel and with vigorous stirring to induce precipitation of the desired complex.</li>
	<li>Collect the precipitate by filtration through a fritted glass (pore size 3) and wash the precipitate with ca. 100 mL of diethyl ether.</li>
	<li>Dry the bright yellow precipitate under vacuum at room temperature (23-25&#160;&#186;C) for 5 h to recover 10.1 g (91% yield) of the copper complex. 
	NOTE: A 75% yield was obtained when the reaction was performed under air using distilled dichloromethane; a 89% yield was obtained when the reaction was performed under argon using regular dichloromethane; when performing the reaction under air with regular dichloromethane, the reaction was found to be less efficient and led to much lower purity (ca 70%, as estimated by 1H NMR with an internal standard).</li>
	<li>Characterize [(DPEPhos)(bcp)Cu]PF6 as previously reported31.</li>
</ol>
2. Direct arylation of N-methylpyrrole with 4-iodobenzonitrile
<ol>
	<li>Add 55 mg (0.05 mmol) of [(DPEPhos)(bcp)Cu]PF6, 59 mg (0.25 mmol) of dicyclohexylisobutylamine (Cy2NiBu), 138 mg (1.0 mmol) of K2CO3 and 114 mg (0.50 mmol) of 4-iodobenzonitrile to an oven-dried 10 mL vial.</li>
	<li>Add a magnetic stir bar, seal the vial with a rubber septum, evacuate the vial under vacuum and backfill with argon three times.</li>
	<li>Add 5 mL of acetonitrile and 890 &#956;L (10.00 mmol) of N-methylpyrrole. Replace the rubber septum by a screw cap. 
	NOTE: Acetonitrile is freshly distilled from CaH2 and degassed using freeze-pump-thaw cycles prior to use to ensure high yields and reproducibility.</li>
	<li>Stir the reaction mixture for 3 days at room temperature (23-25&#160;&#186;C) in a photoreactor under 420 nm wavelength irradiation. 
	NOTE: As an alternative to the use of a photoreactor, the reaction can also be conveniently performed using blue LEDs strips or a photochemistry device with a blue LED lamp (440 nm, 34 W). These experimental setups are shown in Figure 3 (see Representative results) and a discussion on their respective results is provided in the &#34;Discussion&#34;&#160;section.</li>
	<li>Filter the reaction mixture through a pad of Celite, wash with ca. 5 mL of diethyl ether and concentrate the filtrate under reduced pressure.</li>
	<li>Purify the crude residue by flash column chromatography over silica gel (eluent system petroleum ether/EtOAc: 90/10).</li>
	<li>Dry the pure compound under vacuum at room temperature (23-25&#160;&#186;C) for 3 h to recover 65 mg (72% yield) of the desired C2-arylated pyrrole. 
	NOTE: The use of blue LEDs strips afforded a 76% yield (69 mg) while the use of a photochemistry device with a blue LED lamp (440 nm, 34 W) afforded an 86% yield (78 mg).</li>
	<li>Characterize the pure compound as previously reported32.</li>
</ol>
3. Cyclization of N-benzoyl-N-[(2-iodoquinolin-3-yl)methyl]cyanamide to luotonin A
<ol>
	<li>Add 37 mg (0.09 mmol) of N-benzoyl-N-[(2-iodoquinolin-3-yl)methyl]cyanamide, 9 mg (9.0 &#956;mol) of [(DPEPhos)(bcp)Cu]PF6, 11 mg (0.04 mmol) of Cy2NiBu and 25 mg (0.18 mmol) of K2CO3 to an oven-dried 7 mL vial equipped with a magnetic stir bar.</li>
	<li>Seal the vial with a rubber septum, evacuate the vial under vacuum and backfill with argon three times.</li>
	<li>Add 2 mL of acetonitrile. Replace the rubber septum by a screw cap. 
	NOTE: Acetonitrile is distilled from CaH2 and degassed using freeze-pump-thaw cycles prior to use to ensure high yields and reproducibility.</li>
	<li>Stir the reaction mixture for 5 days at&#160;room temperature (23-25&#160;&#186;C) in a photoreactor under 420 nm wavelength irradiation.</li>
	<li>Filter the reaction mixture through a pad of Celite, wash with ca. 2 mL of dichloromethane and concentrate the filtrate under reduced pressure.</li>
	<li>Purify the crude residue by flash column chromatography over silica gel (eluent system: petroleum ether/EtOAc 60:40).</li>
	<li>Dry the pure compound under vacuum at room temperature (23-25&#160;&#186;C) for 3 h to recover 20 mg (79% yield) of the desired luotonin A.</li>
	<li>Characterize the desired luotonin A as previously reported29.</li>
</ol>

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The authors have nothing to disclose.

Synthesis of [(DPEPhos)(bcp)Cu]PF6 
The synthesis of [(DPEPhos)(bcp)Cu]PF6 is typically performed using dry dichloromethane (distilled prior to use) and under argon to ensure the highest yield, purity and good reproducibility. As mentioned in the protocol, the synthesis of [(DPEPhos)(bcp)Cu]PF6 can be performed with regular dichloromethane (99.8%) and/or under air with variable efficiencies. Indeed, while the use of regular dichloromethane under argon afforded the sa...

Radical transformations have been known for decades to provide remarkably efficient pathways in synthetic chemistry which are often complementary to transformations based on cationic, anionic or pericyclic processes1. While particularly promising for various types of transformations, radical-based chemistry has however long been underexploited, mainly because of the need for highly toxic reagents which considerably limits its attractiveness. Moreover, radical processes have long been considered as transformations associated with poor levels of control in terms of regio- and/or stereoselectivity, or leading to extensive dimerization and/or polymerization issues.
Alternative strategies have recently been developed in order to facilitate the generation and better control the reactivity of radical species. Among them, photoredox catalysis has become one of the most powerful methods as it allows the convenient generation of radical species using a light-responsive compound, namely the photoredox catalyst, and visible light irradiation2,3. Visible light itself is indeed able to promote population of the excited state of the photoredox catalyst which becomes, consequently, both a stronger reductant and oxidant than in its corresponding ground state. These enhanced redox properties make single-electron transfer processes, not feasible in the ground state, possible under mild conditions from the excited state. Over the past decade, visible light photoredox catalysis has become an attractive and powerful technique in organic synthesis and has allowed the development of numerous remarkably efficient and selective transformations based on radical intermediates generated under sustainable, mild and user-friendly conditions.
While most photoredox processes reported to date are dominated by the use of iridium- and ruthenium-based photoredox catalysts, as well as by some organic dyes such as pyrylium and acridinium derivatives4, cheaper alternatives are still highly demanded for the development of complementary processes of interest for industrial applications. In this regard, the use of copper-based photoredox catalysts appears particularly appealing as they are not only cheaper but also provide opportunities to activate a broader and/or different range of substrates, which therefore opens new perspectives in photoredox catalysis5,6,7,8. Despite some promising early works reported by the Kutal9, Mitani10&#160;and Sauvage11&#160;groups, photoactivatable copper complexes have, however, only been scarcely used in photoredox catalysis, most probably because of their short-lived excited states compared to their ruthenium- and iridium-based congeners. More recently, recent remarkable contributions by Peters and Fu12,13,14,15, Reiser16,17,18,19,20&#160;and other groups21,22,23,24,25&#160;have clearly brought attention back to copper-based photoredox catalysts and demonstrated their unique potential.
As part of our recent interest in copper-catalyzed radical processes26,27, we recently reported a general and broadly applicable copper-based photoredox catalyst, [(DPEPhos)(bcp)Cu]PF6 (DPEPhos: bis[(2-diphenylphosphino)phenyl] ether; bcp: bathocuproine), which turned out to be particularly efficient for the activation of organic halides under visible light irradiation (Figure 1A)28,29,30. Upon irradiation with visible light and in the presence of an amine as sacrificial reductant, a wide range of unactivated aryl and alkyl halides was shown to be easily activated by catalytic amounts of [(DPEPhos)(bcp)Cu]PF6 and therefore to participate in various radical transformations including reductions, cyclizations and direct arylation of several electron-rich (hetero)arenes. Furthermore, [(DPEPhos)(bcp)Cu]PF6 has also proven successful at promoting photoinduced radical domino cyclizations of ynamides and cyanamides, providing an efficient and straightforward access to complex tri-, tetra- and pentacyclic nitrogen heterocycles at the core structures of various natural products. This strategy permitted the efficient synthesis of rosettacin, luotonin A, and deoxyvasicinone, natural products that exhibit anticancer, antimicrobial, anti-inflammatory and antidepressant activities. These transformations are illustrated in Figure 1C. From a mechanistic standpoint, the photoinduced activation of organic halides with [(DPEPhos)(bcp)Cu]PF6 proceeds through a rare Cu(I)/Cu(I)*/Cu(0) catalytic cycle, which has been confirmed by extensive mechanistic and photophysical studies. In particular, excitation of the ground state [(DPEPhos)(bcp)Cu]PF6 [Cu(I)] upon irradiation by visible light leads to the formation of the corresponding excited complex [(DPEPhos)(bcp)Cu]PF6* [Cu(I)*] which is then reduced by the sacrificial amine to generate the corresponding [(DPEPhos)(bcp)Cu]PF6 [Cu(0)] species. This Cu(0) intermediate is reductive&#160;enough to reduce the carbon&#8211;halogen bond of various organic halides to generate the corresponding radicals, which can then participate in the aforementioned transformations, together with regeneration of the starting catalyst (Figure 1B).
In the following section, we first describe the protocol to synthesize the photoactivatable [(DPEPhos)(bcp)Cu]PF6 (whose NMR and spectroscopic characterizations are presented in the representative results section). The synthesis is straightforward and particularly convenient, and simply requires addition of 1 equivalent of DPEPhos and 1 equivalent of bcp to a solution of tetrakisacetonitrile copper(I) hexafluorophosphate in dichloromethane. The desired [(DPEPhos)(bcp)Cu]PF6 is then isolated by precipitation from diethyl ether and can be easily obtained on a multigram scale (Figure 2A). Importantly, the isolated copper complex is not particularly sensitive to oxygen and moisture and can therefore be conveniently handled with no specific precautions other than being stored away from light.
Secondly, we describe the protocols to activate organic halides using [(DPEPhos)(bcp)Cu]PF6 under visible light irradiation by focusing on two different transformations. The first reaction is the direct arylation of N-methylpyrrole with 4-iodobenzonitrile using catalytic amounts of [(DPEPhos)(bcp)Cu]PF6 as photoredox catalyst, dicyclohexylisobutylamine as the sacrificial reductant and potassium carbonate as the base under irradiation at 420 nm (Figure 2B). The second reaction is the radical cyclization of N-benzoyl-N-[(2-iodoquinolin-3-yl)methyl]cyanamide, using the same catalyst and sacrificial reductant, whose cyclization directly leads to luotonin A, a natural product displaying interesting anticancer activities (Figure 2C). Detailed protocols are provided for both transformations.

<table border="0" cellpadding="0" cellspacing="0" style="width:572px;" width="573">
	<colgroup>
		<col />
		<col />
		<col />
		<col />
	</colgroup>
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Material</td>
			<td style="width:71px;"></td>
			<td style="width:119px;"></td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Bathocuproine (bcp)</td>
			<td style="width:71px;">Acros</td>
			<td style="width:119px;">161340010</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Acetonitrile, 99.9+</td>
			<td style="width:71px;">Acros</td>
			<td style="width:119px;">326811000</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Celite 545</td>
			<td style="width:71px;">Acros</td>
			<td style="width:119px;">349670025</td>
			<td></td>
		</tr>
		<tr height="63">
			<td height="63" style="height:63px;width:216px;">Bis[(2-diphenylphosphino)phenyl] ether (DPEphos)</td>
			<td style="width:71px;">Acros</td>
			<td style="width:119px;">383370050</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Calcium hydride</td>
			<td style="width:71px;">Acros</td>
			<td style="width:119px;">C/1620/48</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Dichloromethane, 99.8%</td>
			<td style="width:71px;">Fisher Chemical</td>
			<td style="width:119px;">D/1852/25</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Dietyl ether, &#62;= 99%</td>
			<td style="width:71px;">Fisher Chemical</td>
			<td style="width:119px;">D/2400/MS21</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Ethyl acetate</td>
			<td style="width:71px;">Fisher Chemical</td>
			<td style="width:119px;">E/0900/25</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">N-Methylpyrrole, 99%</td>
			<td style="width:71px;">Sigma Aldrich</td>
			<td style="width:119px;">M78801</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">4-Iodobenzonitrile, 98%</td>
			<td style="width:71px;">Combi-Blocks</td>
			<td style="width:119px;">OR-3151</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Petroleum ether (40-60 &#176;)</td>
			<td style="width:71px;">Fisher Chemical</td>
			<td style="width:119px;">P/1760/25</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Potassium carbonate, anhydrous</td>
			<td style="width:71px;">Fisher Chemical</td>
			<td style="width:119px;">P/4120/60</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Tetrakisacetonitrile copper(I) hexafluorophosphate, 97%</td>
			<td style="width:71px;">Sigma Aldrich</td>
			<td style="width:119px;">346276</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Equipment</td>
			<td style="width:71px;"></td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">1H and 13C NMR spectrometer</td>
			<td style="width:71px;">Bruker</td>
			<td style="width:119px;">Avance 300 Spectrometer</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">1H and 13C NMR spectrometer</td>
			<td style="width:71px;">Varian</td>
			<td style="width:119px;">VNMRS 400 Spectrometer</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">420 nm light tubes</td>
			<td style="width:71px;">Luzchem</td>
			<td style="width:119px;">LZC-420</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Blue LEDs lamp</td>
			<td style="width:71px;">Kessil</td>
			<td style="width:119px;">H150-Blue</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Blue LEDs strips</td>
			<td style="width:71px;">Eglo</td>
			<td style="width:119px;">92065</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Photochemistry Device PhotoRedOx Box</td>
			<td style="width:71px;">Hepatochem</td>
			<td style="width:119px;">HCK1006-01-016</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Photoreactor</td>
			<td style="width:71px;">Luzchem</td>
			<td style="width:119px;">CCP-4V</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Spectrofluorimeter</td>
			<td style="width:71px;">Shimadzu</td>
			<td style="width:119px;">RF-5301PC</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">UV/Vis spectrometer</td>
			<td style="width:71px;">Perkin Elmer</td>
			<td style="width:119px;">Lambda 40</td>
			<td></td>
		</tr>
	</tbody>
</table>

[(dpephos)(bcp)cu]pf6: a general and broadly applicable copper-based photoredox catalyst

Our group recently reported the use of [(DPEPhos)(bcp)Cu]PF6 as a general copper-based photoredox catalyst which proved efficient to promote the activation of a broad variety of organic halides, including unactivated ones. These can then participate in various radical transformations such as reduction and cyclization reactions, as well as in the direct arylation of several (hetero)arenes. These transformations provide a straightforward access to a range of small molecules of interest in synthetic chemistry, as well as to biologically active natural products. Altogether, [(DPEPhos)(bcp)Cu]PF6 acts as a convenient photoredox catalyst which appears to be an attractive, cheap and complementary alternative to the state-of-the-art iridium- and ruthenium-based photoredox catalysts. Here, we report a detailed protocol for the synthesis of [(DPEPhos)(bcp)Cu]PF6, as well as NMR and spectroscopic characterizations, and we illustrate its use in synthetic chemistry for the direct arylation of (hetero)arenes and radical cyclization of organic halides. In particular, the direct arylation of N-methylpyrrole with 4-iodobenzonitrile to afford&#160;4-(1-methyl-1H-pyrrol-2-yl)benzonitrile and the radical cyclization of N-benzoyl-N-[(2-iodoquinolin-3-yl)methyl]cyanamide to afford natural product luotonin A are detailed. The scope and limitations of this copper-based photoredox catalyst are also briefly discussed.

Synthesis of [(DPEPhos)(bcp)Cu]PF6 
As shown by the protocol described in the above section, the synthesis of [(DPEPhos)(bcp)Cu]PF6 is particularly convenient and can be easily performed on a multigram scale. The 1H and 13C NMR spectra indicate formation of the pure complex (Figure 4A,B). The spectroscopic data correspond to those previously reported31.
...

Watch this Scientific Journal Video about [DPEPhosbcpCu]PF6: A General and Broadly Applicable Copper-Based Photoredox Catalyst at JoVE.com

[DPEPhosbcpCu]PF6: A General and Broadly Applicable Copper-Based Photoredox Catalyst

Detailed and general protocols are presented for the synthesis of [(DPEPhos)(bcp)Cu]PF6, a general copper-based photoredox catalyst, and for its use in synthetic chemistry for the direct arylation of C-H bonds in (hetero)arenes and radical cyclization of organic halides.

[(DPEPhos)(bcp)Cu]PF6: A General and Broadly Applicable Copper-Based Photoredox Catalyst

Our group recently reported the use of [(DPEPhos)(bcp)Cu]PF6 as a general copper-based photoredox catalyst which proved efficient to promote the ...

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9.1K Views.  Université libre de Bruxelles (ULB). Detailed and general protocols are presented for the synthesis of [(DPEPhos)(bcp)Cu]PF6, a general copper-based photoredox catalyst, and for its use in synthetic chemistry for the direct arylation of C-H bonds in (hetero)arenes and radical cyclization of organic halides.

Video: [DPEPhosbcpCu]PF6: A General and Broadly Applicable Copper-Based Photoredox Catalyst

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 ...

From Constructs to Crystals &#8211; Towards Structure Determination of &#946;-barrel Outer Membrane Proteins

Membrane proteins serve important functions in cells such as nutrient transport, motility, signaling, survival and virulence, yet constitute only ~1% percent of known structures. There are two types of membrane proteins, &#945;-helical and &#946;-barrel. While &#945;-helical membrane proteins can be found in nearly all cellular membranes, &#946;-barrel membrane proteins can only be found in the outer membranes of mitochondria, chloroplasts, and Gram-negative bacteria. One common bottleneck in structural studies of membrane proteins in general is getting enough pure sample for analysis. In hopes of assisting those interested in solving the structure of their favorite &#946;-barrel outer membrane protein (OMP), general protocols are presented for the production of target &#946;-barrel OMPs at levels useful for structure determination by either X-ray crystallography and/or NMR spectroscopy. Here, we outline construct design for both native expression and for expression into inclusion bodies, purification using an affinity tag, and crystallization using detergent screening, bicelle, and lipidic cubic phase techniques. These protocols have been tested and found to work for most OMPs from Gram-negative bacteria; however, there are some targets, particularly for mitochondria and chloroplasts that may require other methods for expression and purification. As such, the methods here should be applicable for most projects that involve OMPs from Gram-negative bacteria, yet the expression levels and amount of purified sample will vary depending on the target OMP.

From Constructs to Crystals &amp;#8211; Towards Structure Determination of &amp;#946;-barrel Outer Membrane Proteins

&#946;-barrel outer membrane proteins (OMPs) serve many functions within the outer membranes of Gram-negative bacteria, mitochondria, and chloroplasts. Here, we hope to alleviate a known bottleneck in structural studies by presenting protocols for the production of &#946;-barrel OMPs in sufficient quantities for structure determination by X-ray crystallography or NMR spectroscopy.

Membrane proteins serve important functions in cells such as nutrient transport, motility, signaling, survival and virulence, yet constitute only ~1% ...

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 ...

HKUST-1 as a Heterogeneous Catalyst for the Synthesis of Vanillin

Vanillin (4-hydoxy-3-methoxybenzaldehyde) is the main component of the extract of vanilla bean. The natural vanilla scent is a mixture of approximately 200 different odorant compounds in addition to vanillin. The natural extraction of vanillin (from the orchid Vanilla planifolia, Vanilla tahitiensis and Vanilla pompon) represents only 1% of the worldwide production and since this process is expensive and very long, the rest of the production of vanillin is synthesized. Many biotechnological approaches can be used for the synthesis of vanillin from lignin, phenolic stilbenes, isoeugenol, eugenol, guaicol, etc., with the disadvantage of harming the environment since these processes use strong oxidizing agents and toxic solvents. Thus, eco-friendly alternatives on the production of vanillin are very desirable and thus, under current investigation. Porous coordination polymers (PCPs) are a new class of highly crystalline materials that recently have been used for catalysis. HKUST-1 (Cu3(BTC)2(H2O)3, BTC = 1,3,5-benzene-tricarboxylate) is a very well known PCP which has been extensively studied as a heterogeneous catalyst. Here, we report a synthetic strategy for the production of vanillin by the oxidation of trans-ferulic acid using HKUST-1 as a catalyst.

The conversion of trans-ferulic acid to vanillin was achieved by heterogeneous catalysis. HKUST-1 was employed in this synthesis and the essential step in the catalytic process was the generation of unsaturated metal sites. Thus, when the catalyst was activated under vacuum, full vanillin conversion (yield of 95%) was obtained.

Vanillin (4-hydoxy-3-methoxybenzaldehyde) is the main component of the extract of vanilla bean. The natural vanilla scent is a mixture of approximately ...

Facile Synthesis of Worm-like Micelles by Visible Light Mediated Dispersion Polymerization Using Photoredox Catalyst

Presented herein is a protocol for the facile synthesis of worm-like micelles by visible light mediated dispersion polymerization. This approach begins with the synthesis of a hydrophilic poly(oligo(ethylene glycol) methyl ether methacrylate) (POEGMA) homopolymer using reversible addition-fragmentation chain-transfer (RAFT) polymerization. Under mild visible light irradiation (&#955; = 460 nm, 0.7 mW/cm2), this macro-chain transfer agent (macro-CTA) in the presence of a ruthenium based photoredox catalyst, Ru(bpy)3Cl2 can be chain extended with a second monomer to form a well-defined block copolymer in a process known as Photoinduced Electron Transfer RAFT (PET-RAFT). When PET-RAFT is used to chain extend POEGMA with benzyl methacrylate (BzMA) in ethanol (EtOH), polymeric nanoparticles with different morphologies are formed in situ according to a polymerization-induced self-assembly (PISA) mechanism. Self-assembly into nanoparticles presenting POEGMA chains at the corona and poly(benzyl methacrylate) (PBzMA) chains in the core occurs in situ due to the growing insolubility of the PBzMA block in ethanol. Interestingly, the formation of highly pure worm-like micelles can be readily monitored by observing the onset of a highly viscous gel in situ due to nanoparticle entanglements occurring during the polymerization. This process thereby allows for a more reproducible synthesis of worm-like micelles simply by monitoring the solution viscosity during the course of the polymerization. In addition, the light stimulus can be intermittently applied in an ON/OFF manner demonstrating temporal control over the nanoparticle morphology.

This article describes a process for producing polymeric self-assembled nanoparticles using visible light mediated dispersion polymerization. Using low energy visible light to control the polymerization allows for the reproducible formation of self-assembled worm-like micelles at high solids content.

Presented herein is a protocol for the facile synthesis of worm-like micelles by visible light mediated dispersion polymerization. This approach begins ...

Peptide and Protein Quantification Using Automated Immuno-MALDI (iMALDI)

Mass spectrometry (MS) is one of the most commonly used technologies for quantifying proteins in complex samples, with excellent assay specificity as a result of the direct detection of the mass-to-charge ratio of each target molecule. However, MS-based proteomics, like most other analytical techniques, has a bias towards measuring high-abundance analytes, so it is challenging to achieve detection limits of low ng/mL or pg/mL in complex samples, and this is the concentration range for many disease-relevant proteins in biofluids such as human plasma. To assist in the detection of low-abundance analytes, immuno-enrichment has been integrated into the assay to concentrate and purify the analyte before MS measurement, significantly improving assay sensitivity. In this work, the immuno- Matrix-Assisted Laser Desorption/Ionization (iMALDI) technology is presented for the quantification of proteins and peptides in biofluids, based on immuno-enrichment on beads, followed by MALDI-MS measurement without prior elution. The anti-peptide antibodies are functionalized on magnetic beads, and incubated with samples. After washing, the beads are directly transferred onto a MALDI target plate, and the signals are measured by a MALDI-Time of Flight (MALDI-TOF) instrument after the matrix solution has been applied to the beads. The sample preparation procedure is simplified compared to other immuno-MS assays, and the MALDI measurement is fast. The whole sample preparation is automated with a liquid handling system, with improved assay reproducibility and higher throughput. In this article, the iMALDI assay is used for determining the peptide angiotensin I (Ang I) concentration in plasma, which is used clinically as readout of plasma renin activity for the screening of primary aldosteronism (PA).

Peptide and Protein Quantification Using Automated Immuno-MALDI iMALDI

A protocol for the protein quantification in complex biological fluids using automated immuno-MALDI (iMALDI) technology is presented.

Mass spectrometry (MS) is one of the most commonly used technologies for quantifying proteins in complex samples, with excellent assay specificity as a ...

Controlled Photoredox Ring-Opening Polymerization of O-Carboxyanhydrides Mediated by Ni/Zn Complexes

Here, we describe an effective protocol that combines photoredox Ni/Ir catalysis with the use of a Zn-alkoxide for efficient ring-opening polymerization, allowing for the synthesis of isotactic poly(&#945;-hydroxy acids) with expected molecular weights (&#62;140 kDa) and narrow molecular weight distributions (Mw/Mn &#60; 1.1). This ring-opening polymerization is mediated by Ni and Zn complexes in the presence of an alcohol initiator and a photoredox Ir catalyst, irradiated by a blue LED (400 - 500 nm). The polymerization is performed at a low temperature (-15 &#176;C) to avoid undesired side reactions. The complete monomer consumption can be achieved within 4 - 8 hours, providing a polymer close to the expected molecular weight with narrow molecular weight distribution. The resulted number-average molecular weight shows a linear correlation with the degree of polymerization up to 1000. The homodecoupling 1H NMR study confirms that the obtained polymer is isotactic without epimerization. This polymerization reported herein offers a strategy for achieving rapid, controlled O-carboxyanhydrides polymerization to prepare stereoregular poly(&#945;-hydroxy acids) and its copolymers bearing various functional side-chain groups.

Controlled Photoredox Ring-Opening Polymerization of O-Carboxyanhydrides Mediated by Ni/Zn Complexes

A protocol for the controlled photoredox ring-opening polymerization of O-carboxyanhydrides mediated by Ni/Zn complexes is presented.

Here, we describe an effective protocol that combines photoredox Ni/Ir catalysis with the use of a Zn-alkoxide for efficient ring-opening polymerization, ...

Synthesis and Performance Characterizations of Transition Metal Single Atom Catalyst for Electrochemical CO2 Reduction

This protocol presents both the synthesis method of the Ni single atom catalyst, and the electrochemical testing of its catalytic activity and selectivity in aqueous CO2 reduction. Different from traditional metal nanocrystals, the synthesis of metal single atoms involves a matrix material that can confine those single atoms and prevent them from aggregation. We report an electrospinning and thermal annealing method to prepare Ni single atoms dispersed and coordinated in a graphene shell, as active centers for CO2 reduction to CO. During the synthesis, N dopants play a critical role in generating graphene vacancies to trap Ni atoms. Aberration-corrected scanning transmission electron microscopy and three-dimensional atom probe tomography were employed to identify the single Ni atomic sites in graphene vacancies. Detailed setup of electrochemical CO2 reduction apparatus coupled with an on-line gas chromatography is also demonstrated. Compared to metallic Ni, Ni single atom catalyst exhibit dramatically improved CO2 reduction and suppressed H2 evolution side reaction.

Synthesis and Performance Characterizations of Transition Metal Single Atom Catalyst for Electrochemical CO2 Reduction

Here, we present a protocol for the synthesis and electrochemical testing of transition metal single atoms coordinated in graphene vacancies as active centers for selective carbon dioxide reduction to carbon monoxide in aqueous solutions.

This protocol presents both the synthesis method of the Ni single atom catalyst, and the electrochemical testing of its catalytic activity and selectivity ...

Heterogeneous Removal of Water-Soluble Ruthenium Olefin Metathesis Catalyst from Aqueous Media Via Host-Guest Interaction

A highly efficient transition metal catalyst removal method is developed. The water-soluble catalyst contains a newly-designed NHC ligand for the catalyst removal via host-guest interactions. The new NHC ligand possesses an adamantyl (guest) tethered linear ethylene glycol units for hydrophobic inclusion into the cavity of a &#946;-cyclodextrin (&#946;-CD) host compound. The new NHC ligand was applied to a Ru-based olefin metathesis catalyst. The Ru catalyst demonstrated excellent activity in representative ring-closing metathesis (RCM) and ring-opening metathesis polymerization (ROMP) reactions in aqueous media as well as organic solvent, CH2Cl2. After the reaction was complete, the lingering Ru residue was removed from the aqueous solution with the efficiency of more than 99% (53 ppm of Ru residue) by simple filtration utilizing a host-guest interaction between insoluble silica-grafted &#946;-CD (host) and the adamantyl moiety (guest) on the catalyst. The new Ru catalyst also demonstrated high removal efficiency via extraction when the reaction is run in organic solvent by partitioning the crude reaction mixture between layers of diethyl ether and water. In this way, the catalyst stays in aqueous layer only. In organic layer, the residual Ru amount was only 0.14 ppm in the RCM reactions of diallyl compounds.

A removable water-soluble N-heterocyclic carbene (NHC) ligand in aqueous media via host-guest interaction has been developed. We demonstrated representative olefin metathesis reactions in water as well as in dichloromethane. Via either host-guest interaction or extraction, the residual ruthenium (Ru) catalyst was as low as 0.14 ppm after the reaction.

A highly efficient transition metal catalyst removal method is developed. The water-soluble catalyst contains a newly-designed NHC ligand for the catalyst ...

Preparation of Polyoxometalate-based Photo-responsive Membranes for the Photo-activation of Manganese Oxide Catalysts

This paper presents a method to prepare charge-transfer chromophores using polyoxotungstate (PW12O403-), transition metal ions (Ce3+ or Co2+), and organic polymers, with the aim of photo-activating oxygen-evolving manganese oxide catalysts, which are important components in artificial photosynthesis. The cross-linking technique was applied to obtain a self-standing membrane with a high PW12O403- content. Incorporation and structure retention of PW12O403- within the polymer matrix were confirmed by FT-IR and micro-Raman spectroscopy, and optical characteristics were investigated by UV-Vis spectroscopy, which revealed successful construction of the metal-to-metal charge transfer (MMCT) unit. After deposition of MnOx oxygen evolving catalysts, photocurrent measurements under visible light irradiation verified the sequential charge transfer, Mn &#8594; MMCT unit &#8594; electrode, and&#160;the photocurrent intensity was consistent with the redox potential of the donor metal (Ce or Co). This method provides a new strategy for preparing integrated systems involving catalysts and photon-absorption parts for use with photo-functional materials.

Here, we present a protocol to prepare charge transfer chromophores based on a polyoxometalate/polymer composite membrane.

This paper presents a method to prepare charge-transfer chromophores using polyoxotungstate (PW12O403-), transition metal ions (Ce3+ or Co2+), and organic ...