title: Phosphine-mediated Highly Enantioselective Spirocyclization with Ketimines as Substrates.
abstract: Phosphine-catalyzed enantioselective annulation reactions involving ketimines are a daunting synthetic challenge owing to the intrinsic low reactivity of ketimine substrates. A highly enantioselective [3+2] cycloaddition reaction that makes use of isatin-derived ketimines as reaction partners was developed. Notably, both simple and γ-substituted allenoates could be utilized, and various 3,2'-pyrrolidinyl spirooxindoles with a tetrasubstituted stereocenter were obtained in excellent yields and with nearly perfect enantioselectivity (>98 % ee in all cases).
authors.affiliation: Zhejiang Provincial Key Laboratory for Chemical & Biological Processing Technology of Farm Products, School of Biological and Chemical Engineering/School of Light Industry, Zhejiang University of Science and Technology, No. 318 Liuhe Road, Hangzhou, 310023, China. chemhanxy@zust.edu.cn.
authors.forename: Xiaoyu
authors.initials: X
authors.lastname: Han
authors.affiliation: Department of Chemistry, National University of Singapore (NUS), 3 Science Drive 3, Singapore, 117543, Singapore.
authors.forename: Wai-Lun
authors.initials: WL
authors.lastname: Chan
authors.affiliation: Department of Chemistry, National University of Singapore (NUS), 3 Science Drive 3, Singapore, 117543, Singapore.
authors.forename: Weijun
authors.initials: W
authors.lastname: Yao
authors.affiliation: Zhejiang Provincial Key Laboratory for Chemical & Biological Processing Technology of Farm Products, School of Biological and Chemical Engineering/School of Light Industry, Zhejiang University of Science and Technology, No. 318 Liuhe Road, Hangzhou, 310023, China.
authors.forename: Yongjiang
authors.initials: Y
authors.lastname: Wang
authors.affiliation: Department of Chemistry, National University of Singapore (NUS), 3 Science Drive 3, Singapore, 117543, Singapore. chmlyx@nus.edu.sg.
authors.forename: Yixin
authors.initials: Y
authors.lastname: Lu
keywords: [3+2] cycloaddition; acyclic ketimines; amino acids; phosphine catalysts; spirooxindoles