1,3-Dipolar cycloaddition to a 1,4-quinone methide: 2,6-Di-t-butyl-4-methylenecyclohexa-2,5-dienone

Abstract

The reactive 1,3-dipoles ethoxycarbonylformonitrile oxide, benzonitrile oxide, diphenylnitrile imine and benzonitrilium 4-nitrobenzylid add to the 4-methylenecyclohexa-2,5-dienone (1) to give the respective 1 : 1 cycloadducts (4a-d). The yields are high and the reactions therefore provide ready access to members of the hetero-spiro[4,5]decatrienone system. Diazomethane, phenyldiazomethane and diphenyldiazomethane also add to the exocyclic methylene moiety of (1) to give only the nitrogen deficient spiro[2,5]octa-4,7-dienones (10a-c).