Single-Step Syntheses of 2-Amino-7-chlorothiazolo[5,4-<i>d</i>]pyrimidines:  Intermediates for Bivalent Thiazolopyrimidines

A single-step process for the preparation of 2-amino-7-chlorothiazolo[5,4-<i>d</i>]pyrimidines, <b>2</b>, was achieved by the reaction of the commercially available 4,6-dichloro-5-aminopyrimidine <b>1</b> with isothiocyanates. This mild reaction accommodates a variety of functionalized isothiocyanates and proceeds in good to excellent yields. The utility of such intermediates is exemplified by subsequent reaction with alkyl or arylamine nucleophiles to afford novel, differentially functionalized 2,7-diaminothiazolo[5,4-<i>d</i>]pyrimidines, <b>3</b>.