Construction of 1-pyrroline skeletons by Lewis acid-mediated conjugate addition of vinyl azides

Lewis acid-mediated conjugate addition of vinyl azides to electrondeficient alkenes led to the efficient construction of 1-pyrroline skeletons. The reactions of vinyl azides with 3-alkylidene-2-oxoindolines afford 30,40-dihydrospiro[indoline-3,20-pyrrol]-2-ones in a diastereoselective fashion, whereas those with dimethyl 2-alkylidenemalonates provide 4,5-dihydro-3H-pyrroles.