Transition Metal-free Single Step Approach for Arylated Pyrazolopyrimidinones and Quinazolinones Using Benzylamines/Benzylalcohols/Benzaldehydes

Abstract

A transition metal-free, one step approach has been developed for the synthesis of pyrazolopyrimidinones using in-situ condensation of benzylamines, benzylalcohol and benzaldehyde with 4-amino-2-methyl-5-propyl-2H-pyrazole-3-carboxylic acid amide promoted by K2S2O8 and water at room temperature. Present protocol tolerated various functional groups such as halides (Cl, F, Br), methoxy, ethoxy, hydroxyl, nitro, trifluromethyl, trifluoromethoxy and was also applicable to heterocyclic moieties. Different arylated pyrazolopyrimidinones were prepared in good to excellent yields. In the present reaction, K2S2O8 is catalyzing the formation of imine as well helping in the cyclization to the desired product. We also reduced the industrially used synthesis steps for sildenafil analogues and prepared in three steps using present method. Arylquinazolinones were also synthesized in high yields using anthranilamide and benzylamines by this methodology.