CARBON-OXYGEN BOND INSERTION IN THE REACTION OF DIALKOXYCARBENES WITH ANHYDRIDES

Dimethoxycarbene (1a) and methoxy(2,2,2-trifluoroethoxy)carbene (1b) were generated in benzene solution by thermolysis of the corresponding 2,2-dialkoxyoxadiazolines 7. The carbenes were trapped by intermolecular reaction with a variety of cyclic anhydrides 8. The products 9 are formally the result of carbene insertion into the bond between the carbonyl carbon and the ring oxygen atoms. The results of a competition between dimethylmaleic and dichloromaleic anhydrides for dimethoxycarbene suggests that this reaction proceeds by nucleophilic attack of dialkoxycarbene onto the carbonyl carbon atom of the anhydride.