Solvent-free organic salt media mono symmetrical aza-Michael: synthesis of new N-mono substituted phthalhydrazide derivatives

In this paper, C-N bond formation between 2,3-dihydrophthalazine-1(4H),4-dione (phthalhydrazide) and alpha,beta-unsaturated esters was investigated and a new series of phthalazine derivatives was synthesized using an efficient and simple method under solvent-free conditions. An aza-Michael addition of phthalhydrazide to both acrylic and fumaric esters led to N-monosubstituted phthalhydrazides (as mono-Michael adduct) in the presence of tetrabutylammonium bromide as a high polar media, and 1,4-diaza-bicyclo[2,2,2] octane as an available organic base. In this reaction, the N1,N2-bis-Michael adduct was not observed at all. Also, reactions were performed at 90 degrees C and yields of products were good to excellent.