An easy and efficient protocol for oxidative synthesis of quinazolinones and benzoxazinones using novel catalyst fromed in- situ from chromium trioxide has been developed. Here chromium trioxide acts as an oxidant and its reduction products catalyze the coupling reaction. Newly developed method demonstrates a new alternative to existing method which is a cost effective approach to synthesize important moieties like quinazolinones and benzoxazinones from easily available starting materials in good to excellent yields.