Oxiranes from Methylenation of the Ester Carbonyl Group by Diazomethane

Esters suitably substituted by electronegative groups were found to react with diazomethane with the anchimeric assistance of a a-system or a trifluoromethyl group close to the ester oxygen to yield 2-alkoxy-2-substituted-oxiranes in good to excellent yields without catalysts.