Studies on Pyrimidine Derivatives and Related Compounds. LXII. Cycloadditions of Alkyl Isothiocyanates with Thiamine and Related Thiazolium Ylids and Facile Conversions of the Adducts to Dihydroimidazo [4, 5-d] thiazole Derivatives

Abstract

Thiamine and related thiazolium ylids react with alkyl isothiocyanates to give spiro-(perhydrofuro [2, 3-d] thiazole-2, 4'-imidazolidine) derivatives (IIa-i) involving two step cycloaddition. Confirmation of the structures is provided by chemical degradations and by infrared, ultraviolet, nuclear magnetic resonance spectroscopic evidences as well as by characteristic mass spectral fragmentations. On heating in acetic acid, some of these (1 : 2) adducts are readily converted to dihydroimidazo [4, 5-d] thiazole derivatives (XIa-d) involving a novel intramolecular cyclization.