Novel conversions of benzo[b]thiophen-3(2H)-ones into 1,2-benzisothiazole and tetrahydro-1,2-benzothiazepin-5-one systems via sulphimide intermediates

Abstract

S-Amination of 2,2-dimethyl-(3a) and 2-benzyl-2-methyl-benzo[b]thiophen-3(2H)-one (3b) with O-mesitylene-sulphonylhydroxylamine followed by treatment with base yielded 3-isopropenyl-(4a) and 3-(1-benzylvinyl)-1,2-benzisothiazole (4b), respectively. Similar treatment of 2-methyl-2-phenyl-(3c) and 2-methyl-2-(p-chlorophenyl)-benzo[b]thiophen-3(2H)-one (3d) gave, in addition to the corresponding 3-vinyl-1,2-benzisothiazoles (4c and d), 4-phenyl-(5a) and 4-(p-chlorophenyl)-2,3,4,5-tetrahydro-1,2-benzothiazepin-5-one (5b), respectively. Reaction of (3a) with chloramine-T gave the corresponding N-tosylsulphimide (9) and sulphoxide (10). Refluxng the N-tosylsulphimide (9) in benzene in the presence of triethylamine causes rearrangement to 4-methyl-2-tosyl-2,3,4,5-tetrahydro-1,2-benzothiazepin-5-one (12a). When the reaction of chloramine-T was applied to (3c), as many as four products, the corresponding 1,2-benzothiazepine (12b), one N-tosylsulphimide (15), and two isomeric sulphoxides (16) were isolated. Reaction pathways are discussed.