Synthesis of 4-Benzo[][]oxazin-4-ones by a Carbonylation-Cyclization Domino Reaction of -Halophenols and Cyanamide.

A mild and convenient one-step preparation of 4-1,3-benzoxazin-4-ones by a domino carbonylation-cyclization process is developed. Readily available -iodophenols are subjected to palladium-catalyzed carbonylative coupling with Mo(CO) and cyanamide, followed by a spontaneous, intramolecular cyclization to afford 4-1,3-benzoxazin-4-ones in moderate to excellent yields. Furthermore, the scope of the reaction is extended to include challenging -bromophenols. Finally, to highlight the versatility of the developed method, Mo(CO) is successfully replaced with a wide array of CO-releasing reagents, such as oxalyl chloride, phenyl formate, 9-methylfluorene-9-carbonyl chloride, and formic acid, making this an appealing strategy for the synthesis of 4-benzo[][]oxazin-4-ones.