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Paper | Regular issue | Vol 24, No. 9, 1986, pp.2493-2506
Published online, 1st January, 1970
DOI: 10.3987/R-1986-09-2493
The Reaction of Quinazolin-4-ones with Organo-metalic Agents — A Presistent Preference for Ring Rupture over Cyclization

Darshan Ranganathan,* Firdous Farooqui, Sanjiv Mehrotra, and Krishnan Kesavan

*Department of Chemistry, Indian Institute of Technology, Kanpur 208016, India


A range of 3-substituted quinazolin-4-ones whose conjugate bases can undergo intramolecular cyclization to tricyclic systems, have been prepared (Scheme 2). The reaction of these with a variety of organolithium agents gave products arising from reagent addition to the quinazolin-4-one 1,2 bond, although experimental results tended to demonstrate that the desired conjugate bases existed in equilibrium with the tricyclic systems. The acetyl salt of 1a with NaH gave product 3c from ring fragmentation. The imidazoquinazoline 8, the parent of which is markedly antihypotensive, resulted from endeavours to prepare a prototype of the desired tricyclic system by an alternate route. Most compounds studied have more than one site for reactivity against the reagents used. The experimental results clearly highlight an overwhelming preference for addition to quinazolin-4-one 1,2 bond.