SYNTHESIS OF PYRIDO-1,2,4-THIADIAZINES RELATED TO ANTIHYPERTENSIVE 1,2,4-BENZOTHIADIAZINE-1,1-DIOXIDES

Oxidation of 3-phenyl-2H-pyrido[2,3-e]-1,2,4-thiadiaz with sodium hypo chlorite and, separately, m-chloroperoxybenzoic acid afforded a 1,1-di oxide and a 5-oxide derivative, respectively. Further examples of such 1,1-dioxide derivatives were synthesised by treating 2-amino-5-methyl pyridine with orthoesters and these were subsequently oxidised to nove l 1,1,5-trioxides. A short route has been developed for the synthesis of 4-aminopyridine3-sulfonamide which was used for the preparation of 4H-pyrido[4,3-e]-1,2,4-thiadiazine 1,1-dioxides; oxidation of the pare nt member of the series gave a 1,1,7-trioxide derivative. 3-Aminopyrid ine-4-sulfonamide has been prepared, and then condensed with triethyl orthoformate to afford 4H-pyrido[3,4-e]-1,2,4-thiadiazine 1,1-dioxide. (C) 1998 Elsevier Science Ltd. All rights reserved.