One-Pot Synthesis of Benzisothiazoles from ortho-Mercaptoacylphenones

Significance

Reported is a one-pot synthesis of 3-substituted benzisothiazoles from ortho-­mercaptoacylphenones by an in situ S-nitrosation procedure. The starting materials, readily prepared from thiosalicylic acids, are transformed into the unstable S-nitroso intermediates A, which upon treatment with EtPPh₂ undergo an aza-­Wittig reaction to produce the products in overall poor to very good yield. i-PentylONO proved to be the best oxidant for the formation of the S-nitroso intermediates without effecting the oxidation of EtPPh₂.