Synthesis of 7-arylethyl-5-arylpyrazolo $$[1{,}5\hbox {-}a]$$ [ 1 , 5 - a ] pyrimidines through an aza-Michael addition/nucleophilic addition/1,3-hydrogen transfer cascade

Abstract

An efficient method for the synthesis of pyrazolo[1,5-a]pyrimidines by the tandem reactions of dienones with pyrazole-3-amine through an aza-Michael addition/nucleophilic addition/1,3-hydrogen transfer process in the presence of potassium hydroxide is described. This protocol offers access to 7arylethyl-5-arylpyrazolo[1,5-a]pyrimidines in good to excellent yield. Meanwhile for 4-substituted dienones, different products, 7-arylethylene-5-arylpyrazolo[1,5-a]pyrimidines, are given through an aza-Michael addition/nucleophilic addition/oxidation process. A gram-scale reaction has been performed to demonstrate the potency of optimized procedure for the scale-up process.