Formal [7 + 2] Cycloaddition of Arynes with N-Vinyl-α,β-Unsaturated Nitrones: Synthesis of Benzoxazonines and Their N-O Bond Cleavage

Formal [7 + 2] Cycloaddition of Arynes with N-Vinyl-α,β-Unsaturated Nitrones: Synthesis of Benzoxazonines and Their N-O Bond Cleavage