A convenient preparation of β-boronate carbonyl derivatives. Evidence for the intervention of boronate “ate”-complexes in enolate alkylations.

Halomethylboronate derivatives from “ate”-complexes with lithium ester enolates, which are relatively stable at room temperature and can be observed by 11B N.M.R. Reaction of an iodomethylboronate derivative with either an ester, ketone or amide enolate provides the corresponding β-boronate carbonyl derivatives in 43–83% yield.