Science of Synthesis

Figadère, B.; Franck, X., Science of Synthesis, (2005) 26, 274.

Diaryl- or dialkylcuprates add readily to thioesters in diethyl ether or tetrahydrofuran (in the case of bulky cuprates) at low temperature (–40°C or –78°C). The two alkyl or aryl residues of a lithium diorganocuprate (R22CuLi) are transferred, but to achieve good yields, an excess (1.1 equiv) of the cuprate is often used.[‌202‌] Care must be taken to avoid the presence of oxygen in the medium as it yields the corresponding ester through oxidation of the cuprate or causes transesterification with pyridyl thioesters.[‌203‌] Higher-order cuprates (R22CuCNLi2) and alkyl(cyano)cuprates of the type R2CuCNLi also give good yields of ketones ‌50‌ when treated with S-phenyl or S-benzothiazol-2-yl thioesters (‌Scheme 47‌).[‌204‌] It is better to use cuprates of the type R2CuCNLi in the case of the benzothiazole derivatives.

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