Reactions of 3-alkoxy- and 3-alkylthio-benzo[b]thiophen 1,1-dioxides with morpholine, piperidine, and pyrrolidine

2-Phenyl-(1a) and 2-methyl-3-methoxybenzo[b]thiophen 1,1-dioxide (1b) undergo ring opening to form amides on treatment with morpholine and with piperidine, but react with pyrrolidine to yield enamines; the 2-unsubstituted analogue (1c) undergoes ring-cleavage to amides with all three amines. 3-Benzyloxy- 6(a) and 3-benzylthio-2-phenylbenzo[b]thiophen 1,1-dioxide (8a) also yield the corresponding amide or thioamide with morpholine and piperidine but the enamine with pyrrolidine.