- Carbon-carbon bond formation by electrochemical catalysis in conductive microemulsions
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Bicontinuous microemulsions made from oil, water, and surfactants were examined as substitutes for organic solvents in carbon-carbon bond-forming reactions. Conjugated additions of primary alkyl iodides 3a-c to 2-cyclohexen-1-one (4) to give 3-alkyl cyclohexanones 5a-c and cyclization of 2-(4-bromobutyl)-2-cyclohexen-1-one (9) to 1-decalone (10) were mediated by the Co(I)L complex vitamin B12s generated at carbon cloth electrodes under mild conditions. Reaction of the Co(I)L nucleophile with the alkyl halides gives a Co-alkyl complex. Cleavage of the Co-alkyl complexes by using an electrode potential of -0.85 V (all vs SCE) and irradiation with visible light, or a potential of -1.45 V in the dark, were compared. Addition of the resulting alkyl radicals to the activated double bonds gave comparable yields of 3-alkylcyclohexanone 5a-c (70-80% using -0.85 V + light) and 1-decalone (90%, both cleavage modes) 10 in microemulsions and in DMF. Microemulsions containing hexadecyltrimethylammonium bromide (CTAB) gave remarkable stereoselectivity for the trans isomer of 10, while homogeneous DMF and a sodium dodecylsulfate (SDS) microemulsion gave little stereoselectivity.
- Gao, Jianxin,Rusling, James F.,Zhou, De-Ling
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p. 5972 - 5977
(2007/10/03)
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- CuX3Li2-catalysed Conjugate Addition of Dialkylmagnesium Reagents to α,β-Unsaturated Carbonyl Compounds
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Copper salts of the type CuX3Li2 (X = halogen) catalyse the conjugate addition of dialkylmagnesium compounds to α,β-unsaturated carbonyl compounds in the presence or absence of Me3SiCl as an additive, the organomagnesium compounds being prepared from α-ol
- Reetz, Manfred T.,Kindler, Alois
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p. 2509 - 2510
(2007/10/02)
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- Direct Formation and Reaction of Thienyl-Based Organocopper Reagents
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The preparation of a highly reactive zerovalent copper complex by the direct reduction of lithium (2-thienylcyano)cuprate with preformed lithium naphthalenide is described.This active copper species oxidatively adds to carbon-halogen bonds to form organocopper reagents.The ability to directly form the organocopper reagent from organic halides and active copper allows for the incorporation of a wide variety of functionalities to be present in the organic halides and the organocopper reagents.Significantly, this formulation of active copper was able to oxidatively add to allyl chlorides and acetates at low temperatures to allow the direct formation of allylic organocopper reagents without Wurtz-type homocoupling.These functionalized organocopper compounds are able to undergo a variety of reactions, such as cross-coupling with acid chlorides, 1,4-conjugate addition with α,β-unsaturated carbonyl compounds, and intermolecular and intramolecular epoxide-opening reactions.Subsequently, this copper species avoids the use of phosphine ligands affording the product isolation much more convenient than with phosphine-based organocopper reagents.
- Rieke, Reuben D.,Klein, Walter R.,Wu, Tse-Chong
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p. 2492 - 2500
(2007/10/02)
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- Preparation and Chemistry of the Active Copper Species Derived from CuI*PBu3, CuI*PPh3, and CuCN*nLiX Complexes
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The preparation of highly reactive copper by the reduction of CuI*PBu3, CuI*PPh3, and CuCN*nLiX copper(I) complexes with the preformed lithium naphthalenide is described.It was found, for all three Cu(I) complexes, that the reduction temperature proved crucial to reactivity of the zerovalent copper species as measured by the ability of the active copper to undergo oxidative addition to carbon-halogen bonds.The lower the reduction temperature the more reactive the zerovalent copper species becomes.The low-temperature reduction allows for the formation of highly reactive copper from CuCN*nLiX complexes.This active copper species undergoes oxidative addition to alkyl and aryl bromides in high yield to form the corresponding organocopper reagent directly without the need for other organometallic precursors.Moreover, the alkyl and aryl bromides can obtain a wide range of functional groups as they are not affected in the oxidative addition step.The functionalized organocopper reagents derived from CuCN*nLiX based active copper are the reagent of choice in the cross-coupling of acid chlorides to produce ketones as well as the 1,4-addition reaction with enones.The lack of phosphines associated with organocopper reagents stemming from CuCN-based active copper makes product isolation more facile.While the functionalized organocopper reagents derived from CuCN*nLiX complexes provide higher isolated yields in the formentioned reactions, they are not nucleophilic enough to undergo inter- or intramolecular epoxide openings.The use of both CuI*PBu3 and CuI*PPh3 Cu(I) complexes in the intramolecular epoxide openings of aryl bromoepoxides is presented.The regiochemistry, endo vs. exo, was shown to be affected by the Cu(I) complex used to generate the active copper species, the solvent, and the pattern of substitution around the epoxide moiety.The active copper species as well as the resulting organocopper reagents derived from both CuI*PBu3 and CuCN*nLiX were investigated using both 31P and 13C NMR.The data from 31P NMR investigation held some evidence for a highly reduced copper(0)-phosphine complex while the 13C studies of the CuCN*nLiX complexes indicated that these species have limited solubility in THF.
- Rieke, Reuben D.,Stack, Douglas E.,Dawson, Bryan T.,Wu, Tse-Chong
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p. 2483 - 2491
(2007/10/02)
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- Soluble highly reactive form of calcium and reagents thereof
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A soluble highly reactive form of calcium, prepared from Ca(II) salts and a reducing agent in ethereal, polyethereal, or hydrocarbon solvents, is presented. This form of calcium can be used in the preparation of organocalcium reagents. The organocalcium reagents resulting from the reaction of the soluble highly reactive calcium with organic compounds containing either halide, cyanide, a 1,3-diene, or a polyunsaturated functionality, are stable, useful reagents for organic synthesis. The organocalcium halide reagents undergo Grignard-type reactions. They also undergo reactions with Cu(I) salts to form organocalcium cuprate reagents. The organocalcium cuprate reagents undergo a variety of cross-coupling reactions. The soluble highly reactive calcium reacts with 1,3-dienes to yield the corresponding 2-butene-1,4-diylcalcium complexes. These bis-organocalcium reagents can undergo dialkylation reactions with α,ω-alkylene dihalides and dichlorosilanes to form the corresponding 3-, 5-, and 6-membered ring derivatives. The soluble highly reactive calcium also reacts with organic dihalides to form mono- or diorganocalcium compounds which can be converted into a wide variety of polymers.
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- Two Equivalent Reduction of Copper(I) Complexes; Evidence of an Anionic Copper Species
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Reactive copper solutions have been prepared by a cold temperature, two equivalent lithium naphthalenide reduction of copper(I) complexes.One equivalent of organic halides react with one equivalent of the anionic copper to yield organocopper reagents.
- Rieke, Reuben D.,Dawson, Bryan T.,Stack, Douglas E.,Stinn, Dean E.
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p. 2711 - 2721
(2007/10/02)
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- Organocalcium Chemistry: Preparation and Reactions of Highly Reactive Calcium
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A highly reactive form of calcium was prepared by the reduction of Ca(II) salts with preformed lithium biphenylide.Remarkably, this activated calcium undergoes oxidative addition to organic bromides, chlorides, or even fluorides to form the organocalcium reagents under very mild conditions in high yields.The resulting organocalcium compounds undergo Grignard-type reactions.Transmetalation with Cu(I) salts forms calcium cuprate reagents which undergo a variety of cross-coupling reactions.The activated calcium reacts with 1,3-dienes to yield the corresponding 2-butene-1,4-diylcalcium complexes.These bis-organocalcium reagents can undergo dialkylation reactions with α,ω-alkylene dihalides and dichlorosilanes to form the corresponding 3-, 5-, and 6-membered ring derivatives.Significantly, these reactions are highly stereospecific and regioselective.
- Wu, Tse-Chong,Xiong, Heping,Rieke, R. D.
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p. 5045 - 5051
(2007/10/02)
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- NEW ORGANOCOPPER REAGENTS PREPARED UTILIZING HIGHLY REACTIVE COPPER
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Highly reactive copper solutions have been prepared by the lithium naphthalide reduction of copper(I) iodide/trialkylphosphine complexes.These activated copper solutions will react with organic halides under very mild conditions to form stable organocopper reagents.Significantly, the organocopper reagents can contain considerable functionalities such as ester, nitrile, chloride, epoxide, and ketone groups.These functionalized organocopper species undergo many reactions typical of other organocopper species.Intermolecular 1,4-additions, epoxide-opening reactions, and ketone formation with acid chlorides have been successfully achieved.In addition, this methodology has been applied to an intramolecular epoxide-cleavage reaction.The influence of the connecting chain length, substitution pattern, reaction solvent, and CuI/phosphine complex upon the regioselectivity of the intramolecular cyclization is described.
- Rieke, Reuben D.,Wehmeyer, Richard M.,Wu, Tse-Chong,Ebert, Greg W.
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p. 443 - 454
(2007/10/02)
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- Direct Formation of Functionalized Alkylcopper Reagents from Alkyl Halides Using Activated Copper. Conjugate Addition Reactions with 2-Cyclohexen-1-one
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Activated copper, prepared by the lithium naphthalide reduction of CuIPR3 complexes, has been shown to readily form stable alkylcopper compounds at low temperatures by direct insertion into carbon-halogen bonds.Alkylcopper reagents containing ester, nitrile, and chloride functionalities have been prepared directly from the corresponding alkyl bromides.These alkylcopper reagents have been used effectively in conjugate additions to 2-cyclohexen-1-one, giving functionalized 3-alkylcyclohexanones in good to excellent yields.This approach allows for functionality previously unavailable in organocopper and cuprate reagents.
- Wehmeyer, Richard M.,Rieke, Reuben D.
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p. 5056 - 5057
(2007/10/02)
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