Synthesis of 1,4-Benzoxazepines via [4 + 3] Annulation of ortho-Vinylphenols and Azaoxyallyl Cations.

A concise formal [4 + 3] annulation between ortho-vinylphenols and in situ generated azaoxyallyl cations from α halohydroxamates has been realized under Cs2CO3-mediated, transition-metal-free conditions in dichloromethane at ambient temperature. This modular protocol enables efficient construction of structurally diverse 1,4-benzoxazepine derivatives with moderate to excellent yields, featuring broad substrate generality and remarkable functional group compatibility. The potential synthetic utility of this protocol is demonstrated by late-stage modification of natural product-derived alcohols (1-undecanol, Majantol, and citronellol) in 85-97% yield and scale-up reaction.