Mixed Gilman cuprate

Introduction of the frans-CH=CHCH20H moiety may be conveniently accomplished using a mixed Gilman cuprate reagent bearing a terminal THP-protected ether (eq 15). The transformation is of considerable utility in several fields of synthesis, including prostaglandin chemistry. 

In 1952 Gilman and co-workers reported that the yellow, ether-insoluble methylcopper dissolved to give a clear colorless solution on addition of a further equivalent of methyllithium 119). The new copper compound, of composition LiCu(CH3)2, is an ate complex now usually known as lithium dimethylcuprate. Mixed cuprates can be prepared from a preformed organocopper compound, RCu, and a lithium reagent 147, 259, 298, 301). 

A less general method involves transfer of a chiral group from the cuprate to the enone. The chiral Gilman reagent [R 2CuLi, R = (R)-2-(l-dimethylamino)phenyl] reacted with (4 )-methyl-3-penten-2-one (473) to give 474 in 30% yield and 80% ee. 33 Reaction of the mixed cuprate [ThR CuLi where Th = 2-thienyl and R = (R)-2-(l-dimethylamino)phenyl] gave 474 in 70% yield (82% ee). 3... 

Confirmation that cw-addition of alkyl copper complexes occurs in these reactions has been obtained by studies of lanthanide-induced shift H n.m.r. spectra of the products. Corey has now introduced (3-methyl-3-methoxybut-l-ynyl)copper in THF as a relatively inexpensive reagent for the generation of mixed cuprates (Gilman s reagents), which enable coupling reactions to occur in high yield with alkyl-lithium reagents. ... 

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