Alkylation of 4-substituted 1-acetoxy-2-cyclopentenes by using copper reagents derived from alkylmagnesium halides and copper(I) cyanide

Alkylation of the acetates derived from 4-phenyl- and 4-butyl-2-cyclopenten-1-ols 2 was investigated with copper reagents derived from n-BuMgX (X=Cl, Br) and CuCN in 2:1 and 1:1 ratios in THF and in Et2O. cis 1,4-Isomers 4a,b (R=Ph, n-Bu) were produced regioselectively from the corresponding trans acetates 3a,b with the reagent in a 2:1 ratio of BuMgCl and CuCN in THF, while the BuMgBr-based reagents of 2:1 and 1:1 ratios in Et2O furnished cis 3,4-isomers 5a,b. A similar tendency was obtained with cis acetates 6a,b (R=Ph, n-Bu).