Derivatives of α,β-dehydroamino acids: V. Intramolecular cyclization of 2-{2-[(Z)-1-Benzamido-2-phenylvinyl]acetamidomethyl}benzimidazole

Reaction of 4-benzylidene-2-phenyl-1,3-oxazol-5(4 H )-one with 2-(1 H -benzimidazol-2-yl)ethaneamine led to the formation of 2-{2-[( Z )-1-benzamido-2-phenylvinyl]acetamidomethyl}benzimidazole that in a reaction with hexamethyldisilazane in DMF gave 5-benzylidene-1-(1 H -benzimidazol-2-yl)-2-phenyl-3,5-dihydro-4 H -imidazol-4-one. In the presence of K 2 CO 3 in dioxane the reaction with hexamethyldisilazane resulted in the product of intramolecular addition, N -(4-benzyl-3-oxo-1,2,3,4-tetrahydropyrazino[1,2- a ]-benzimidazol-4-yl)benzamide