Synthesis, Experimental and Computational Spectroscopic Studies, and Formation Thermodynamics of Diethyl [[2-(1-Aryl-4,5-dihydro-1H-imidazol- 2-yl)hydrazinyl]methylene]propanedioates

We present experimental and computational studies on the pseudo-Michael reaction of (E)-1-aryl-2-hydrazinyl- 4,5-dihydro-1H-imidazoles with diethyl (ethoxymethylene)malonate (DEEM). The pseudo-Michael reaction leads to chain adducts, i.e. diethyl [[2-(1-aryl-4,5-dihydro-1H-imidazol-2-yl)hydrazinyl]methylene]propanedioates. This result is in contrast to our earlier studies on the pseudo-Michael reaction of DEEM with 1-aryl-4,5-dihydro-1H-imidazol-2-amines which results in imidazo[1,2-α]pyrimidine derivatives even at low temperature without the possibility of isolating chain intermediates. The structure of all the compounds is confirmed with experimental and computational spectroscopy (1H and 13C NMR, IR, MS). Furthermore, thermodynamics of the reaction and HOMO-LUMO of the reactants are studied by using of quantum chemical calculations.