One-Pot Synthesis of Arylsulfonamides and Azetidine-2,4-diones via Multicomponent Reaction of an Amine, an Acetylenic Compound, and an Arylsulfonyl Isocyanate

An effective route to novel arylsulfonamides is described. It involves the reaction of an enamine derived from the addition of primary or secondary amines to acetylenecarboxylates (dialkyl acetylenedicarboxylates or alkyl propiolates) with an arylsulfonyl isocyanate. These arylsulfonamides show dynamic NMR behavior in solution. A different reactivity pattern was observed with the methyl 3-(diethylamino)acrylate. The latter, generated in situ from Et 2 NH and methyl propiolate, on reaction with an arylsulfonyl isocyanate afforded exclusively the azetidine-2,4-dione (malonimide-) derivatives in good yield. These malonimides also show dynamic NMR behavior in solution because of restricted rotation around the C-N bond resulting from conjugation of the side-chain N-atom with the adjacent α,β-unsaturated carbonyl group.