The Pseudo-Michael Reaction of 2-Hydrazinylidene-1-Arylimidazolidines with Diethyl Ethoxymethylenemalonate

摘要

The pseudo-Michael reaction of 2-hydrazinylidene-1-arylimidazolidines with diethyl ethoxymethylenemalonate (DEEM) was investigated. The reaction yields the chain adduct, namely diethyl{[2-(1-arylimidazolidin-2-ylidene)hydrazinyl]methylidene}propanedioates. This is contrary to the pseudo-Michael reaction of DEEM with 1-aryl-4,5-dihydro-1H-imidazol-2-amines that does not allow isolation of chain derivatives and leads to cyclic imidazo[1,2-a]pyrimidine derivatives while even at thermodynamic control. At first cyclization of diethyl{[2-(1-arylimidazolidin-2-ylidene)hydrazinyl]methylidene}propanedioates leads to ethyl 1-aryl-5(1H,8H)oxo-2,3-dihydro-imidazo[2,1-c][1,2,4]triazepine-6-carboxylates. 1,5-Sigmatropic shift, following the cyclization, caused isomerization of 5(1H,8H)oxo-2,3-dihydro-imidazo[2,1-c][1,2,4]triazepine-6-carboxylates to ethyl 1-aryl-5(1H)hydroxy-2,3-dihydroimidazo[2,1-c][1,2,4]triazepine-6-carboxylates. Presence of both isomers in the reaction product was detected in the NMR spectra. The structure of all the compounds was confirmed with spectroscopic studies (H-1 NMR and MS). The structure of diethyl{[2-(1-phenylimidazolidin-2-ylidene)hydrazinyl]methylidene}propanedioate was also confirmed by X-ray crystallography. In the addition reaction, thermodynamics and HOMO-LUMO orbitals of the reactants were studied by using quantum chemical calculations.