Chemoselective and enantioselective synthesis of 3-aminoisothiazolo S-oxides

Chemoselective and enantioselective synthesis of 3-aminoisothiazolo S-oxidesThe main scope of our project is the chemoselective oxidation of 3-amino-isothiazoles 1 affording the new 3-amino-isothiazole S-oxides 3. The number of oxidizing reagent used for the oxidation of sulfides to sulfoxides are many and varied but few have general or broad application. Many oxidizing reagents are too reactive over-oxidizing sulfoxides to sulfones, with other the chemoselectivity is poor or they give undesiderable side reactions. Additional limitations include slow reaction rates, the necessity for careful control of the reaction parameters, instability and expense. Among the oxidizing reagents available we found N-sulfonyloxaziridines 2 as the more effective and selective reagents affording 3 in satisfactory yield (61-64%) together with minor amount of the corresponding sulfones 4 (10-15%) Much efforts has also been devoted to the development of methodology for the preparation of optically active sulfoxides. Several kind of chiral sulfonyloxazirides have been tested affording optically active sulfoxides with satisfactory yield and ee% depending on the hindrance of oxaziridines. As an example the reaction between 1 and 4a or 4b is reported: