Benzyne-Mediated Route to Benzoxazinones

Significance

A general route to benzoxazinone derivatives by the reaction of benzynes with imines under 1 atm of CO₂ is described. The reaction presumably proceeds by generation of zwitterionic intermediates arising from nucleophilic attack of imines to arynes followed by CO₂ trapping and cyclization. Electron-withdrawing groups on Ar and bulky R¹ lead to low yields or no product, which suggests that decreased nucleophilicity and steric hindrance are detrimental to the reaction.