One-Pot Construction of -Selective Quinolines with -Quaternary Carbon from Vinylquinolines with Active Ylides via Pd/Sc/Bronsted Acid Co-Catalysis

Vinyl-substituted N-heterocycles, as more challenginginert olefinswith more stable reactivity, have brought about widespread attentionin the reaction of aza-Michael addition or reduction coupling reaction.Here, we report a [Pd-(eta(3)-C3H5)-Cl](2)/Sc-(OTf)(3)-catalyzed catalytic processaccelerated by Bronsted acids with a beta-selective aza-Michaeladdition to yield a gamma-quaternary carbon from vinyl-substitutedquinolines, diazos, and anilines/alcohols in one pot. The generationof anhydride analogues from Bronsted acid and the counter anion(OTf-) of Lewis acid promotes the activation ofthe corresponding Lewis acid and the nearly quantitative transformation.Both pi-cation and coordination interactions play pivotal rolesin the activation of the vinyl-quinoline substrates by the activatedLewis acid Sc-(OTf)(3). The control mechanistic evidence andDFT calculations presented a Pd/Sc/Bronsted acid co-catalyzedaddition mechanism. The triple co-catalytic system provides a strategyfor the activation of vinyl-quinolines with a linear selectivity containing gamma-quaternary carbon, and the developed method shows a broadsubstrate scope varying from alkyl/aryl alcohols and amines whichprovides a general and rapid strategy for the quinoline-based diverselibrary construction.