The pseudo-Michael reaction of 1-aryl-4,5-dihydro-1H-imidazol-2-amines with ethyl ethoxymethylenecyanoacetate

Abstract

The pseudo-Michael reaction of 1-aryl-4,5-dihydro-1H-imidazol-2-amines with ethyl 2-cyano-3-methoxyprop-2-enoate (ethyl ethoxymethylenecyanoacetate) is investigated. At −10 °C reaction takes place on the exocyclic nitrogen atom, giving exclusively ethyl esters of 2-cyano-3-[(1-phenyl-4,5-dihydro-1H-imidazol-2-yl)amino]prop-2-enoic acid. The formation of isomeric enamines which may be a theoretical product of the reaction on N3 ring nitrogen atom is not observed. The N6 enamines, heated in boiling acetic acid, yield cyclic 1-aryl-5-oxo-2,3-dihydroimidazo[1,2-a]pyrimidine-6-carbonitriles. Heating of the enamines to the temperature of 120–140 °C without a solvent makes it possible to obtain a mixture of 1-aryl-5-oxo-2,3-dihydroimidazo[1,2-a]pyrimidine-6-carbonitriles and ethyl 1-aryl-5-imino-2,3-dihydroimidazo[1,2-a]pyrimidine-6-carboxylates. The reaction of the respective hydrobromides of 1-aryl-4,5-dihydro-1H-imidazol-2-amines with ethyl ethoxymethylenecyanoacetate in the presence of triethylamine gives selectively 1-aryl-5-oxo-1,2,3,5-dihydroimidazo[1,2-a]pyrimidine-6-carbonitriles.Graphical Abstract

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

“…Compounds 2a , 2b , 2c , 2d , 2e were subjected to pseudo‐Michael reaction with DEEM in 96% ethyl alcohol, yielding chain adducts 3a , 3b , 3c , 3d , 3e . The isolation of chain derivatives was possible in this case, similarly as in our previously reported reaction of 1‐aryl‐4,5‐dihydro‐1 H ‐imidazol‐2‐amines with EMCA (Scheme ) and contrary to the earlier reported reaction of DEEM with 1‐aryl‐4,5‐dihydro‐1 H ‐imidazol‐2‐amines .…”

“…We also investigated the pseudo‐Michael reaction of 1‐aryl‐4,5‐dihydro‐1 H ‐imidazol‐2‐amines with ethyl ethoxymethylenecyanoacetate (EMCA; Scheme ). In the case of this Michael reagent, we were successful in isolating the chain enamines .…”

Trivinylphosphine Oxide: Synthesis, Characterization, and Polymerization Reactivity Investigated Using Single-Crystal Analysis and Density Functional Theory

“…The exploration of the reactivity of TVPO at the critical β-C position (of the vinyl group) provides opportunities for innovative synthetic methodologies. The present investigation is centred on the examination of the nucleophilic addition reactions of TVPO with piperazine (i.e., pseudo-Michael addition) [ 22 , 23 ] and VMB (i.e., anionic addition reaction using a Grignard reagent) reactions. Our objective is to elucidate the complex thermodynamic and kinetic aspects of every reaction through the determination of the free energy and barrier heights for both the forward and reverse directions.…”