title: Asymmetric cascade annulation based on enantioselective oxa-Diels-Alder cycloaddition of in situ generated isochromenyliums by cooperative binary catalysis of Pd(OAc)2 and (S)-Trip.
abstract: An asymmetric cascade annulation between 2-hydroxystyrenes and 2-alkynylbenaldehyes or 1-(2-alkynylphenyl)ketones has been established with good to excellent enantioselectivities (up to >99.5% ee), on the basis of an enantioselective oxa-Diels-Alder cycloaddition of in situ generated metallo-isochromenylium intermediates, by cooperative binary catalysis of Pd(OAc)2 and (S)-Trip. The developed methodology is workable for a broad spectrum of substrates and shows great efficiency in establishing dense multiple chiral centers including quaternary carbons of variable bridged ring systems. The mechanism study suggests that (S)-Trip plays multiple roles in assembling the reactants and controlling the stereoselectivity.
authors.affiliation: State Key Laboratory of Coordination Chemistry, Nanjing National Laboratory of Microstructures, School of Chemistry and Chemical Engineering, Nanjing University, 22 Hankou Road, Nanjing, Jiangsu 210093, China.
authors.forename: Shu-Yan
authors.initials: SY
authors.lastname: Yu
authors.forename: Hao
authors.initials: H
authors.lastname: Zhang
authors.forename: Yang
authors.initials: Y
authors.lastname: Gao
authors.forename: Lei
authors.initials: L
authors.lastname: Mo
authors.forename: Shaozhong
authors.initials: S
authors.lastname: Wang
authors.forename: Zhu-Jun
authors.initials: ZJ
authors.lastname: Yao