Iminofuran chemistry. Unexpected direction of reaction between 5-(4-methylphenyl)-2-(2-methylphenylimino)furan-3-one with ethylenediamine

Publications on derivatives of 2-imino-2H-furan-3one are not numerous. In recyclization reactions with binucleophiles they form new heterocyclic systems [1]. It was shown formerly that the reaction of Nsubstituted 5-aryl-2-imino-2Н-furan-2-ones with оphenylenediamine via the opening of the furan ring after the attack of the primary amino group on the С 2 atom of the heterocycle led to the formation of 2-[3amino-quinoxalin-2(1Н)-ylidene]-1-phenylethanone 1 [2]. Aiming at the preparation of 1-(4-methylphenyl)2-{-3-[(2-methylphenyl)imino]piperazin-2-ylidene}ethanone 2 we attempted to bring into the reaction instead of о-phenylenediamine a structural analog of the biologically active compound “mephepyron,” 3[2-oxo-2-(4-methylphenyl)ethylidene]piperazin-2-one 3 [3]. To this end from (4-methylbenzoyl)ketene, generated in situ by thermal decarbonylation of 5-(4-methylphenyl)furan-2,3-dione 4, and 1-isocyano-2-methylbenzene we prepared 5-(4-methylphenyl)-2-[(2-methylphenyl)