Ag2CO3 catalyzed aza-michael addition of pyrazoles to α, β-unsaturated carbonyl compounds: A new access to N-alkylated pyrazole derivatives

Abstract

An efficient Ag2CO3 catalyzed aza-Michael addition of pyrazoles to α, β-unsaturated carbonyl compounds is developed. In the present of 5 mol% of Ag2CO3, the reaction smoothly occurs in DCE at 120 °C to afford a series of N-alkylated pyrazoles in good to excellent yields. It is noteworthy that N1-alkylated pyrazoles are obtained with high regioselectivity (N1/N2 up to above 25:1) when asymmetrically substituted pyrazoles reacted with α, β-unsaturated carbonyl compounds. The method can also extend to gram scale.