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.
J Am Chem Soc. 2013 Jul 31;135(30):11402-7. doi: 10.1021/ja405764p. Epub 2013 Jul 18.
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.
建立了一种不对称级联环化反应，可通过 Pd(OAc)2 和 (S)-Trip 的协同双催化作用，以良好到优异的对映选择性（最高可达 >99.5%ee），从 2-羟基苯乙烯和 2-炔基苯甲醛或 1-(2-炔基苯基)酮原位生成的手性氧杂-Diels-Alder 环加成反应中生成的手性金属异苯并呋喃中间体来实现。该方法适用于广泛的底物，并在构建包括可变桥环系统的季碳原子在内的密集多个手性中心方面具有很高的效率。机理研究表明，(S)-Trip 在组装反应物和控制立体选择性方面发挥了多种作用。
