Ring-enlargement and ring-opening reactions of 1,2-thiazetidin-3-one 1,1-dioxides with ammonia and primary amines as nucleophiles

The N-benzyl- and N-alkyl-substituted 1,2-thiazetidin-3-one 1,1-dioxides 1b -d reacted readily with NH3 and primary amines via ring opening. The reacti on with NH3 proceeded at -78 degrees - room temperature yielding ring-opene d adducts via nucleophilic attack of NH3 at the sulfonyl group, whereas the reactions with amines at room temperature yielded products via attack at t he carbonyl group. The N-unsubstituted analogue la; when reacted with benzy lamine in refluxing EtOH, also gave a product of ring opening via nucleophi lic attack at the carbonyl group of 1a. The transamidation-like reactions o f the 2-(aminoalkyl)-1,2-thiazetidin-3-one 1,1-dioxides 19a-d proceeded via six-, seven-, and eight-membered intermediates, giving the ring-enlarged e ight-, nine-, and ten-membered products 21-24 (Schemes 8 and 9), respective ly, in 42-87% yields. The products resulted from the nucleophilic attack of the amino group of the side chain at the carbonyl C-atom. The structure of the eight-membered product 24 with an asymmetrically situated methyl subst ituent Has established by X-ray crystallography.