title: N,N'-dioxide/nickel(II)-catalyzed asymmetric inverse-electron-demand hetero-diels-alder reaction of β,γ-unsaturated α-ketoesters with enecarbamates.
abstract: N,N'-Dioxide/nickel(II) complexes have been developed to catalyze the inverse-electron-demand hetero-Diels-Alder reaction of β,γ-unsaturated α-ketoesters with acyclic enecarbamates. After detailed screening of the reaction parameters, mild optimized reaction conditions were established, affording 3,4-dihydro-2H-pyranamines in up to 99 % yield, 99 % ee and more than 95:5 d.r. The catalytic system was also efficient for β-substituted acyclic enecarbamates, affording more challenging 2,3,4-trisubstituted 3,4-dihydro-2H-pyranamine with three contiguous stereogenic centers in excellent yields, diastereoselectivities, and enantioselectivities. The reaction could be scaled up to a gram scale with no deterioration of either enantioselectivity or yield. Based on these experiments and on previous reports, a possible transition state was proposed.
authors.affiliation: Key Laboratory of Green Chemistry and Technology, Ministry of Education, College of Chemistry, Sichuan University, Chengdu 610064 (China), Fax: (+86) 28-85418249.
authors.forename: Yuhang
authors.initials: Y
authors.lastname: Zhou
authors.forename: Yin
authors.initials: Y
authors.lastname: Zhu
authors.forename: Lili
authors.initials: L
authors.lastname: Lin
authors.forename: Yulong
authors.initials: Y
authors.lastname: Zhang
authors.forename: Jianfeng
authors.initials: J
authors.lastname: Zheng
authors.forename: Xiaohua
authors.initials: X
authors.lastname: Liu
authors.forename: Xiaoming
authors.initials: X
authors.lastname: Feng
keywords: Diels-Alder reaction; N,N′-dioxides; asymmetric catalysis; cycloaddition; nickel