Thiazoloisoquinolines. IV. The Synthesis and Spectra of Thiazolo[4,5-h]- and Thiazolo[5,4-f]isoquinolines. The Ultraviolet and Proton Magnetic Resonance Spectra of Some Substituted Isoquinolines

Abstract

Thiazolo[4,5-h]isoquinoline was synthesized from 7-aminoisoquinoline in four steps: by the reaction with potassium thiocyanate and bromine to give 7-amino-8-thiocyanoisoquinoline; cyclization of the latter with hydrochloric acid to produce 2-aminothiazolo[4,5-h]isoquinoline, followed by the Sandmeyer reaction to yield a 2-chloro derivative, and finally, reduction with hydriodic acid and phosphorus. Thiazolo[5,4-f]isoquinoline was prepared from 6-aminoisoquinoline via 6-amino-5-thiocyanoisoquinoline. The synthesis of 2,5-diaminothiazolo[5,4-h]isoquinoline was achieved by cyclization of 5-acetamido-8-aminoisoquinoline which was obtained from 5-aminoisoquinoline. In 5-amino-8-thiocyano- and 8-amino-5-thiocyanoisoquinolines, the thiocyano group was hydrolyzed to the thiol group with 8 N hydrochloric acid and ethanol (1:1).The u.v. and p.m.r. spectra of the intermediate isoquinolines, and the i.r., u.v., and n.m.r. spectra of thiazoloisoquinolines were studied.