Synthesis of 2-substituted isothiazolo[5,4-b]pyridin-3-(2H)-one 1,1-dioxides

The Isothiazolo[5,4-b]pyridin-3(2H)-one 1,1-dioxides (3a - g) were prepared from the corresponding isothiazolo[5,4-b]pyridin-3(2H)-ones (1a - g) by means of an oxidation with oxone(R) (KHSO5) and sodium hypochlorite (NaOCl) in two steps. The influence of the substituents (R), in position 2 of this system, on the oxidation process was studied. While the oxidation of 1a - g with 3-chloroperoxybenzoic acid gave yields of 3a - g depending greatly on the nature of R, the combined KHSO5/NaOCl method gave good yields of 3a - g in all of the cases studied.