Methylation of 3-hexyloxy-10H-pyridazino[4,3-b][1,4]benzothiazine

Abstract

3-Hexyloxy-10H-pyridazino[4,3-b][1,4]benzothiazine reacts with methyl iodide in the presence of sodium hydride to give the 10-methyl-derivative, the 1-methyl derivative of a tautomeric form, and, under more vigorous conditions, 2,10-dimethyl-10H-pyridazino[4,3-b][1,4]benzothiazin-3(2H)-one. The 10-methyl compound has been identified by an independent synthesis while the structures of the other products are established mainly by spectroscopic methods. Some 3- and 4-alkoxy and aryloxy-10H-pyridazino[4,3-b][1,4]benzothiazines are also described.