Synthesis and reactions of 3-alkylsulfanyl-1,3-dihydro-2,1-benzisothiazole 2,2-dioxides

Alkyl- and arylsulfanylation of 1,3-dihydro-2,1-benzisothiazole 2,2-dioxides (benzosultams) and pyridosultam with dialkyl and diaryl disulfides provides dithioacetals of 2-aminobenzaldehydes . 1,3-Dimethylbenzosultam with disulfides forms 3-alkyl(aryl)sulfanyl-1,3-dimethylbenzosultams that undergo thermal extrusion of SO2 followed by a [1,5] sigmatropic hydrogen shift in the intermediate aza-ortho-xylylene leading to 1-arylvinyl sulfides . Tandem alkylation–sulfanylation of benzo- and pyridosultams with 4-bromobutyl thiocyanate gives tetrahydrothiopyrano-spiro-benzosultams that, after extrusion of SO2 and [1,5] hydrogen shift, form 2-aryl-5,6-dihydro-4H-thiopyrans . Alkylation of pyridosultam with 3-chloropropyl thiocyanate leads directly to 2-pyrido-3,4-dihydrothiophene derivative .