C-Acylation of Enolates by Methyl Cyanoformate: An Examination of Site- and Stereoselectivity

The scope and limitations of the acylation of preformed lithium enolates by methyl cyanoformate have been explored further. In particular, the proportion of C-acylation products in sterically hindered substrates is significantly enhanced by the use of diethyl ether as solvent, while diastereofacial selectivity in the reactions of chiral enolates is found to be similar to that observed for C-alkylations in most cases. Exceptions may occur as a consequence of the higher steric demand of the cyanoformate reagent, however.