Synthesis of Thiazolopyrimidinones under Solvent-Free Conditions

Significance

Reported here is the regioselective synthesis of 5H-thiazolo[3,2-a]pyrimidin-5-ones 3 and 4 from acetates 1 and 2-aminothiazoles 2 under solvent- and base-free conditions. The regio-selectivity is easily controlled by adjusting the ­reaction temperature, with 3 formed exclusively at room temperature and 4 at 130 ˚C. A wide range of aromatic (R^¹) groups are tolerated, including EDGs and EWGs. Substitution on the thiazole ring was inadequately examined, although two examples of benzothiazole syntheses were also demonstrated. The yields ranged from moderate to ­excellent in most cases.