N-Hydroxy indoles as flexible substrates in rearrangements—a novel reaction with activated triple bonds

A novel rearrangement of N-hydroxy indole derivatives obtained from addition of N-hydroxy indoles to the activated triple bonds of alkynes was found to coexist with 3,3-sigmatropic rearrangements to the indolic ring. A mechanism involving an intermediate oxaziridinium ring rationalizes the transformation.