Direct access of the chiral quinolinyl core of cinchona alkaloids via a brønsted acid and chiral amine co-catalyzed chemo- and enantioselective α-alkylation of quinolinylmethanols with enals

A strategy for the facile construction of the chiral quinolinylmethanolic structure, a core featured in cinchona alkaloids, is reported. A new reactivity is harnessed by TfOH-promoted chemoselective activation of α-C-H over O-H bond in quinolinylmethanols. The new reactivity is successfully engineered with an iminium catalysis in a synergistic manner to create a powerful conjugate addition-cyclization cascade process for synthesis of chiral quinoline derived π-butyrolactones in good yields and with good to excellent enantioselectivities. The method enables the first total synthesis of natural product broussonetine in three steps.