Reaction of dimethoxycarbene with strained cyclic carbonyl compounds

A cyclopropanone, a cyclopropenone, cyclobutanones, a cyclobutane-1,3-dione , and a cyclobutene-1,2-dione reacted with dimethoxycarbene to afford aceta ls of the next larger ring by formal insertion of the carbene into a C-C bo nd alpha to the carbonyl group. When either of two saturated alpha-ring car bons could be involved in the process, the ring expansion was selective, af fording primarily the product of apparent insertion into the more substitut ed ring bond. With 2,3-dimethoxycyclobutene-1,2-dione, insertion occurred b etween the carbonyl groups and with beta-propiolactone it occurred at the l actone bond. beta-Propiolactam, however, reacted by insertion of the carben e into the N-H bond.