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-dihydroimidazo2,1-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 pyrimido2,1-b]quinazolines, imidazo1,2-a]pyrido2,3-d]pyrimidines, and imidazo1,2-a]pyrazolo3,4-d]pyrimidines. Treatment of 8a with hydrazine hydrate or methylhydrazine gave products resulting from displacement, but did not afford fused benzotriazepinones.