The reactivity of the title compounds towards some electrophiles is investigated. An interesting ring-enlargement product is isolated in the reaction of 3-pyrrolidin-1-yl-5,6-dihydro-4H-thiopyran 1,1-dioxide with methanesulphonyl chloride.
The structures and the reactivities of the title vinylogous sulphonamides are compared with those of the corresponding vinylogous amides derived from cyclohexane-1,3-dione. Their behaviour on alkylation, acylation, and addition-substitution has been studied. Isolation of some of the products can be explained in terms of the existence of a tautomeric equilibrium in the parent systems.