A novel α,β-unsaturated nitrone-aryne [3+2] cycloaddition and its application in the synthesis of the cortistatin core

We describe here a novel α,β-unsaturated nitrone-aryne [3+2] cycloaddition. The resulting benzoisoxazolines underwent N–O bond reduction–elimination–electrocyclization sequence to furnish a variety of polysubstituted 2H or 2-alkylated-1-benzo-pyrans. The application of this methodology was further demonstrated in the synthesis of the oxa[3.2.1]octene moiety of cortistatin A.