DMAP-catalyzed cyclization of Schiff bases with alpha-halo ketones: Synthesis of 1,4-benzoxazines

We demonstrate that 1,4-benzoxazines can be efficiently synthesized using 4-dimethylaminopyridine (DMAP) as a catalyst. We found that the DMAP catalyst can successfully promote the incorporation of the activated carbon atoms of a-halo ketones into the Schiff bases. The 1,4-benzoxazines can be synthesized through the formation of C-O and C-C bonds in high yield, using DMAP as the catalyst, a-halo ketones and phenolic Schiff bases as the reactants. Furthermore, a possible mechanism is proposed. This work provides a simple and efficient route to prepare the 1,4-benzoxazines.