Thiazoloisoquinolines. III. Structure and methylation of 2-hydroxythiazolo[4,5-c]- and -[5,4-c]isoquinolines

Abstract

2-Hydroxythiazolo[4,5-c]isoquinoline (1) and 2-hydroxythiazolo[5,4-c]isoquinoline (2) were both found to exist predominantly in the lactam form (1b and 2b respectively) from infrared, nuclear magnetic resonance, and ultraviolet spectral evidence. Various methylating agents methylated compound 1 exclusively on the N-3 atom in the thiazole ring. Compound 2 on the other hand, gave a mixture of O-and N-3 methylated products with diazomethane and a mixture of N-1 and N-4 methylated products with either methyl iodide or dimethyl sulfate.