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4.4.10.2 Method 2: Synthesis of Mixed Alkyl(triorganosilyl)copper(I) Reagents

DOI: 10.1055/sos-SD-004-00260

Singer, R. D.Science of Synthesis, (20024232.

The mixed cuprates, such as (R3Si)(Me)Cu(CN)Li2, can be prepared by substituting 1 equivalent of methyllithium for 1 equivalent of the triorganosilyl anion (i.e., PhMe2SiLi). These modified triorganosilylcopper reagents selectively transfer the trialklylsilyl moiety to the usual substrates in good to excellent yields. They also minimize silicon-containing byproducts formed during workup and, hence, simplify purification. Due to the numerous equilibria that exist between interchanging silylcopper species[‌16‌‌18‌] in solution these mixed reagents can be prepared in a number of ways. For example, they can be prepared by sequential addition of stoichiometric amounts of the requisite anions to the copper(I) salt or by the admixture of preformed cuprate reagents [i.e., (PhMe2Si)2CuLi plus Me2CuLi], with the former method being most common. Noteworthy is that these mixed alkyl(triorganosilyl)copper(I) reagents give generally lower yields than lithium bis(dimethylphenylsilyl)cuprate.[‌19‌]

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