Synthesis of 4 H -Benzo[ e ][ 1,3 ]oxazin-4-ones by a Carbonylation-Cyclization Domino Reaction of ortho -Halophenols and Cyanamide.

A mild and convenient one-step preparation of 4H-1,3-benzoxazin-4-ones by a domino carbonylation-cyclization process is developed. Readily available ortho-iodophenols are subjected to palladium-catalyzed carbonylative coupling with Mo(CO)(6) and cyanamide, followed by a spontaneous, intramolecular cyclization to afford 4H-1,3-benzaxazin-4-ones in moderate to excellent yields. Furthermore, the scope of the reaction is ex tended to include challenging orthobromophenols. 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 4H-benzo[e][1,3]oxazin-4-ones.