On the sulfimidation of benzo[b]thiophene

Benzo[b]thiophene and chloramine-T react in the presence of catalytic amounts of [Cu(NCMe)4]BF4 to yield a novel dihydrobenzothiazine arising from a ring-expansion; if the reaction is conducted in the absence of the copper(I) catalyst no reaction takes place, but the expected sulfimide can be made using [(N-tosylimino)iodo]benzene, PhI=NTs.