Reverse-Cope elimination versus 1,3-dipolar cycloaddition in the reaction of enantiopure 2-azetidinone-tethered alkynylaldehydes with N-methylhydroxylamine

Enantiopure 2-azetidinone-tethered alkynylaldehydes 1 react stereoselectively under mild conditions with N-methylhydroxylamine to yield products derived from either intramolecular reverse-Cope elimination or 1,3-dipolar cycloaddition, depending on both the length of the tether and the experimental conditions.