Lithium diphenyl cuprate

As stated above, intermolecular coupling reactions between carbon atoms are of limited use. In the classical Wurtz reaction two identical primary alkyl iodide molecules are reduced by sodium. n-Hectane (C100H202), for example, has been made by this method in 60% yield (G. Stallberg, 1956). The unsymmetrical coupling of two alkyl halides can be achieved via dialkylcuprates. The first halide, which may have a branched carbon chain, is lithiated and allowed to react with copper(I) salts. The resulting dialkylcuprate can then be coupled with alkyl or aryl iodides or bromides. Although the reaction probably involves radicals it is quite stereoselective and leads to inversion of chiral halides. For example, lithium diphenyl-cuprate reacts with (R)-2-bromobutane with 90% stereoselectivity to form (S)-2-phenylbutane (G.M. Whitesides, 1969). 

Lithium dimethyl cuprate, 209-215 Lithium diphenylarsenide, 341 Lithium diphenyl cuprate, 234 Lithium diphenylphosphide, 340-341, 645 Lithium diphenylphosphinate, 340 Lithium di-n-propyl cuprate, 245 Lithium ethynyltrialkylborates, 324-325 Lithium fluoride, 17... 

Secondary and tertiary dialkylcuprates, lithium dialkenyl-, and even diphenyl-cuprates, add in very good yields to the reactive propionaldehyde diethyl acetal. The syn addition products may be trapped with a variety of electrophiles such as alkyl, alkenyl, alkynyl and aryl halides. The method has been used for the synthesis of several natural products. Substituted alkynic acetals also react with lithium dialkylcuprates in ether to furnish stable dialkenylcuprates of type (128) which do not eliminate to the corresponding alkoxy allenes (129) if the temperature is maintained below -20 C.164-179... 

The synthetic power of these silylcuprate and stannylcuprate reactions lies in the synthetic utility of the product silanes and stannanes for carbon-carbon bond formation and also in the utilization of the silyl [38] or stannyl substituents as agents for stereocontrol and regiocontrol. Additionally use of appropriate silylcuprates permits conversion of the produced C Si bond into a C OH bond (Tab. 3.1) [39]. This C Si to C OH conversion is a particularly difficult transformation for an allyl silane and the development of lithium diphenyl(2-methyl-2-butenyl)silylcuprate for this purpose illustrates the characteristic transformations of silylcuprates (Scheme 3.1) [14e]. Several silyl substituents convertible into hydrosy groups are not amenable to the cuprate methodologj vinyl silanes - generated by... 

The reaction is illustrated by the formation of propiophenone from diphenyl-cadmium and propanoyl chloride (Expt 6.126). Better yields are obtained by carrying out the synthesis in this manner rather than attempting the alternative combination of diethylcadmium with benzoyl chloride. Alternatively an alkyl-lithium cuprate could be used with an aromatic acid chloride (p. 616). 

Phenylation, by using diphenyl lithium cuprate, was stereospecific in both E and Z isomers of appropriate alkenyl iodonium salt, proceeding with complete retention of configuration. 

DIALKYLACETIC ACIDS 2-Methyl-4-methoxymethyl-5-phenyl-2-oxazoline. frans-2,3-DlALKYLCYCLOPENTANONES Lithium methyl(vinyl) cuprate. a, a-DIALKYL KETONES Diphenyl disulfide. 

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