10.1007/s11178-008-3029-9

Abstract

SHORT COMMUNICATIONSThe synthesis of 4-arylmethylidene-1-(arylmethylideneamino)imidazol-5-ones via cyclization of N-benzoyl α,β-dehydro amino acid arylmethylidenehydrazides by the action of acid reagents was reported in [1,2]. We recently showed that primary amides [3], arylamides [4], and hydrazides derived from N-substituted α,β-dehydro amino acids [5] in the presence of silylating agents (chlorotrimethylsilane, hexamethyldisilazane) undergo dehydration to give 2,4-di-or 1,2,4trisubstituted imidazol-5-ones.In the present communication we describe the synthesis of 2-aryl-4-arylmethylidene-1-arylmethylideneamino-4,5-dihydro-1H-imidazol-5-ones II by cyclization of N-substituted α,β-unsaturated amino acid arylmethylenehydrazides I in the presence of hexamethyldisilazane (HMDS). The reactions were carried out by heating the reactants in boiling DMF for 15-30 min. The proposed procedure for the cyclization of com-pounds I is more advantageous than those reported in [1, 2] from the viewpoints of both reaction time and yield of the target imidazol-5-ones.The 1 H NMR spectra of compounds IIa-IIi contained a singlet from the CH=C proton at δ 7.07-7.22 ppm, indicating their Z configuration (cf. [2]). N-[2-(4-Methoxyphenyl)-1-(3,4-methylenedioxybenzylidenehydrazinocarbonyl)ethenyl]benzamide (Ie). Yield 78%, mp 212-214°C. Found, %: C 67.59; H 4.91; N 9.13. C 25 H 21 N 3 O 5 . Calculated, %: C 67.71; H 4.77; N 9.47. N-[1-(4-Methoxybenzylidenehydrazinocarbonyl)-2-(3,4-methylenedioxyphenyl)ethenyl]furan-2-carboxamide (Ig). Yield 92%, mp 225-226°C. Found, %: C 64.