Catalyst-Free Synthesis of Functionalized 4-Substituted-4 H -Benzo[ d ][1,3]oxazines via Intramolecular Cyclization of ortho- Amide- N -tosylhydrazones.

Functionalized 4-aryl-4 H -benzo[ d ][1,3]oxazines are synthesized under transition-metal-free conditions using ortho -amide- N -tosylhydrazones. This synthetic method uses readily available N -tosylhydrazones as the diazo compound precursors and involves an intramolecular ring closure reaction mediated by a protic polar additive ( i PrOH). A wide range of functionalized oxazines are obtained by this straightforward method in good to excellent yields. Furthermore, the viability of our strategy is illustrated by the gram-scale elaboration of a bromo-substituted 4 H -benzo[ d ][1,3]oxazine and its post-functionalization by palladium-catalyzed cross-couplings.