The Reactions of β-Amino α,β-Unsaturated Esters with Amines. II. Syntheses of Some New Derivatives of Quinazolines

Abstract The reaction of 1,4-bis(ethoxycarbonyl)-2,5-diamino-1,4-cyclohexadiene(Ia) with aniline in aprotic solvents gave N,N′-diphenylurea, whereas in the presence of a proton acid this reaction gave an amine-exchanged product,14-bis(ethoxycarbonyl)-2,5-dianilino-1,4-cyclohexadiene(Ib). However, when 2-aminopyridine was used in place of aniline for this reaction, 1,4-bis(ethoxycarbonyl)-2,5-bis(2-pyridylamino)-1,4-cyclohexadiene(Ic) was not isolated but its cyclyzed analogue, 6,7,14,15-tetrahydropyrido[2,1-b]pyrido[1′,2′:1,2]pyrimido[4,5-g]quinazoline-7,15-dione(IIa), was obtained. The reaction of 2-amino-6-methylpyridine with la also gave a quinazoline derivative without producing a 1,8-naphthyridine derivative. Since this reaction took place easily in a weak acid, AcOH, this cyclization could proceed by an intramolecular proton-transfer mechanism.