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

ABSTRACT

Various benzoxazonines were synthesized through a formal [7 + 2] cycloaddition of arynes with N-vinyl-α,ß-unsaturated nitrones under mild conditions. Controllable N-O bond cleavage of benzoxazonines afforded polysubstituted pyrrole-tethered benzopyrans and acyclic ketone-substituted phenols in moderate to good yields. Further transformations provided a facile approach to access useful building blocks with specific stereoselectivity.