ChemInform Abstract: Preparation of Imidazo(2,1-b)quinazolin-5(3H)-ones and Related Tricyclic Systems Using a Novel, Double Displacement Reaction

New methodology is described for the construction of tricyclic heterocycles. Thus, a double displacement reaction of l-(2-fluorobenzoyl)-2-methylthio-2-imidazoline (8a) with 1,1-dialkylhydrazines gave 10-substituted 2,10-dihydroimidazo[2,1-b]quinazolin-5(3H)-ones in good yield. The corresponding 1-(2-nitrobenzoyl)-2-meth-ylthio-2-imidazolines also underwent double displacement reactions with hydrazines. Other tricyclics made using double displacement reactions were pyrimido[2,1-b]quinazolines, imidazo[1,2-a]pyrido[2,3-d]pyrimidines, and imidazo[1,2-a]pyrazolo[3,4-d]pyrimidines. Treatment of 8a with hydrazine hydrate or methylhydrazine gave products resulting from displacement, but did not afford fused benzotriazepinones.