Lithium diorganocuprates, reactions

The stereoselective 1,4-addition of lithium diorganocuprates (R2CuLi) to unsaturated carbonyl acceptors is a valuable synthetic tool for creating a new C—C bond.181 As early as in 1972, House and Umen noted that the reactivity of diorganocuprates directly correlates with the reduction potentials of a series of a,/ -unsaturated carbonyl compounds.182 Moreover, the ESR detection of 9-fluorenone anion radical in the reaction with Me2CuLi, coupled with the observation of pinacols as byproducts in equation (40) provides the experimental evidence for an electron-transfer mechanism of the reaction between carbonyl acceptors and organocuprates.183... 

In an effort to demonstrate the synthetic utility of vinyliodonium salts, small-scale reactions of (4-rm-butyl-1 -cyclohexenyl)phenyliodonium tetrafluoroborate (62) with various nucleophilic species, especially copper(I) reagents, have been conducted125,126. The copper(I)-assisted reactions include the conversions of 62 to 1-cyano-, 1-halo-, 1-alkyl- and 1-phenyl-4-ter r-butylcyclohexenes (equation 215). The alkylation and phenylation of the cyclohexenyl ligand in 62 with lithium diorganocuprates is noteworthy, since the treatment of 62 with H-butyllithium leads to fragmentation of the iodonium ion and affords only a 0.2% yield of 1 -w-butyl-4-terr-butylcyclohexene (equation 216)126. 

The reactions of lithium diorganocuprates with a./3-unsaturated carbonyl compounds give excellent yields of 1.4-addition products ... 

The coupling of j8-bromostyrene with lithium diorganocuprates at a low temperature was also accompanied by reduction and elimination as important side reactions (309). The reaction is summarized by Eq. (54). 

Conjugate addition to an a,3-unsaturated carbonyl compound is achieved routinely by using a lithium organocopper reagent or a copper-catalyzed Grignard reaction. " It should be noted that in many of these examples, and in particular in the case of lithium diorganocuprates, the resultant enolate has... 

Additions. Lithium diorganocuprates R2CuLi (e.g., R = n-Bu) add to the double bond of cyclopropenyl carbinols. The stereochemical course of the reaction is different from that employing RMgBr-CuI. 

Organoboranes, 228, 230-233 Organocopper compounds. See Lithium diorganocuprates Organolithium reagents basicity of, 551-553, 570 preparation of, 549-550, 571 reaction of... 

Reaction of an Acid Chioride with a Lithium Diorganocuprate (Section 18.9C)... 

Early observations that certain Grignard reactions could be catalyzed by copper salts eventually led to systematic studies of organocopper compounds as reagents for carbon-carbon bond formation. Of these, lithium diorganocuprates known as Gilman reagents proved to be the most effective. 

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