EPOXIDATION OF 2,3-DIMETHYLBENZOFURANS BY DIMETHYLDIOXIRANE

The synthesis of epoxides 2 by the reaction of the chloro- and methyl-substiluted 2,3-dimethylbenzofurans 1 with dimethyldioxirane at low temperature is reported. These labile epoxides were spectroscopically characterized (H-1 and C-13 NMR) at subambient temperatures. Epoxidation of benzofuran 1c affords a 31:69 mixture of epoxide 2c and quinone methide 3c, the latter presumably being produced by valence isomerization of the epoxide. On warming up above -10-degrees-C, the epoxides 2 suffer decomposition. Treatment of epoxide 2i with methanol yields the tautomeric mixture of adducts 4i and 4i'.