Addition of n-Butylcuprates to α-Methylenecycloalkylidene Epoxides

Article abstract of DOI:10.1021/jo00210a010

The addition of n-butylmagnesium bromide-copper(I) iodide in THF-dimethyl sulfide has been carried out with the 10-, 12-, 13-, 14-, 15-, and 16-membered α-methylenecycloalkylidene epoxides 2a-f.In each case the S_N2' substitution products 4 and 5 were formed with the trans isomer predominating by 85:15 or greater.The findings are consistent with a reactant-like transition state involving the s-trans conformer of the epoxide-cuprate complex.The starting alkylidene epoxides 2a-d and 2f were prepared by addition of dimethylsulfonium methylide to the α-methylene ketones 1a-d and 1f.Epoxide 2e was obtained via Wittig methylenation of epoxy ketone 3.