Novel syntheses of pyrido[1,2-a]pyrimidin-2-ones, 2H-quinolizin-2-ones, pyrido[1,2-a]quinolin-3-ones, and thiazolo[3,2-a]pyrimidin-7-ones

Abstract

As novel 1,3-bis-electrophilic synthons, 1-benzotriazolyl-2-propynones provide access to the fused ring systems of pyrido[1,2-a]pyrimidin-2-ones and 2H-quinolizin-2-ones, known for their diverse biological activities. Reactions of N-(phenylpropioyl)benzotriazole (13a) with substituted 2-aminopyridines 14 afforded pyrido[1,2-a]pyrimidin-2-ones 16a-c in good yields (71-73%). Likewise, 2H-quinolizin-2-ones 18a-f were obtained in moderate to good yields (39-81%) from reactions of benzotriazolyl-2-propynones 13a,b with substituted 2-picolines 14. Extension of this methodology to other fused ring systems has provided 1-alkyl- and 1-arylpyrido[1,2-a]quinolin-3-ones 20a,b (40%) and 5-phenylthiazolo[3,2-a]pyrimidin-7-one (22) (54%) in moderate yields.