A Facile and Efficient Synthesis of 4H-1,3-Benzoxazine-4-one with Electron-Withdrawing Group Derivatives.

An efficient and environmentally friendly protocol of 4H-1,3-benzoxazine-4-ones was developed based on the ring-formation of o-halogenbenzoylurea under alkaline condition with K2CO3 as the base. The method scope and limitations were also investigated. The results indicated that the electron-withdrawing ability of the substituents on the phenyl ring is beneficial to this heterocyclization.