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

: Kaczor AA, Kijkowska-Murak U, Pihlaja K, Sinkkonen J, Wysocki W, Karczmarzyk Z, Matosiuk D

: Springer

Publisher: SPRINGER WIEN

: 2013

: Chemical Monthly / Monatshefte für Chemie

: MONATSHEFTE FUR CHEMIE

: MONATSH CHEM

: 8

: 144

: 8

: 1171

: 1182

: 12

: 0026-9247

DOI: https://doi.org/10.1007/s00706-013-0982-y

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 A degrees 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 A degrees 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.