Heterocycles by Cycloaddition. IV. Cycloaddition Reactions of Mesoionic Compounds with a 7-Azabicyclo[2.2.1]heptadiene, and Double Fragmentation of the Adducts

Abstract

Abstract Cycloaddition of some five-membered mesoionic compounds with dimethyl 7-tosyl-7-azabicyclo[2.2.1]hepta-2,5-diene-2,3-dicarboxylate occurs only across the unsubstituted double bond. Pyrolysis of the adducts resulted in a double fragmentation reaction to give two five-membered aromatic heterocycles. A dithiolone adduct gave the S-oxide, which was pyrolyzed to the corresponding thiopyran-2-one.