Oxyfunctionalization of novel diaryl- and triaryl-isothiazolium salts: the first isolable crystalline 3-hydroperoxyisothiazole

The synthesis of novel monocyclic di- and triphenyl-substituted hydroperoxysultims rac-cis 7 and 8 and sultams 11 and 12, as well as the 3-oxosultams 15 and 16, by oxidation of corresponding salts 1 and 2 with H2O2 in acetic acid is described. For the first time, it was possible to isolate a 3-hydroperoxide (3a) and also to determine the position of the primary oxidizing attack on the C-3 atom of isothiazolium salts 1, which have generally a much lower oxidation reactivity. Novel 3-hydroxysultams 13 and 14 were obtained by oxidation reaction of salts 1 and 2 with magnesium monoperoxyphthalate (MMPP) in acetonitrile in the ultrasound bath. Dedicated to Professor Dr. Jurgen Liebscher on the occasion of his 60th birthday.