Green synthesis of new acyl hydrazide derivatives by single and double aza-Michael reaction under solvent-free conditions

In this paper, we describe a new, simple and efficient strategy for the formation of novel and valuable acyl hydrazide derivatives from reaction between diverse acyl hydrazides and α,β-unsaturated esters in the presence of 1,4-diaza-bicyclo[2,2,2]octane (DABCO) – an inexpensive base – and tetrabutylammonium bromide (TBAB) – an ionic organic salt – under solvent-free conditions. In the reaction, double Michael adducts were produced in good yields in 7 h when acrylic esters were used as Michael acceptors. Surprisingly, no double Michael adducts were produced with fumaric esters, and single Michael adducts were the only products of these reactions in 10 h.