Homocuprates mixed

Mixed homocuprates.7 Mixed cuprates (1) in which the nontransferable ligand is an a-sulfonyl carbanion are easily prepared from dimethyl sulfone or methyl phenyl sulfone (equation I), and are effective for conjugate addition to enones and for a synthesis of ketones from acid chlorides. 

Mixed cuprates derived fiom deprotonation and transmetalation of ketone dimethylhydrazones, using copper(I) thiophenoxide as the copper(I) source, are effective as enolate equivalents in 1,4-conjugate additions to a,3-unsaturated esters. The mixed phenylthio cuprate was found to exhibit approximately the same selectivity and reactivity in these reactions as a similar homocuprate (63) prepaid from the aza-allyllithium reagents and copper(I) iodide (equation 29). 

Nucleophilic Substitutions of Halides. Although unreactive with benzyl bromide and vinyl iodides, lithium (3,3-diethoxy-l-propen-2-yl)(phenylthlo)cuprate undergoes clean substitutions with allyllc bromides to afford 1,4-dienes (eq 1). The mixed homocuprate lithium (3,3-diethoxy-l-propen-2-yl)(3,3-dlmethyl-l-bulynyl)cuprate provides similar results. ... 

Additions to 2-Alkenones. The reagent undergoes 1,4-addltlon to cyclohexenone, cyclopentenone, and 3-penten-2-one In 50-80% chemical yields in diethyl ether the use of THF greatly diminishes formation of 1,4-adducts. A comparative study indicates that mixed homocuprates, especially lithium (3,3-dlethoxy-l-propen-2-yl)(3,3-dimethyl 1 bulynyl)cuprate, are the reagents of choice in 1,4-additions (eq 2). ... 

Thus, the reaction of mixed (phenylthio)alkylcuprates with 9-BBN overcomes the problem associated with (1) the thermal instability of phenoxy- and tert-bu-toxyalkylcuprates, (2) the low reactivity of mixed acetylenic cuprates, and (3) the wasting of one R group of the homocuprates. 

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