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Atom Transfer Radical Polymerization of Functionalized Vinyl Monomers Using Perylene as a Visible Light Photocatalyst
Published on: April 22, 2016
Visible-Light-Enabled Ir-Catalyzed Asymmetric Allylic Etherification and Dearomative Photocycloaddition
Pusu Yang1, Rui-Xiang Wang1,2, Yuan-Zheng Cheng1
1New Cornerstone Science Laboratory, State Key Laboratory of Organometallic Chemistry, Shanghai Institute of Organic Chemistry, University of Chinese Academy of Sciences, Chinese Academy of Sciences, 345 Lingling Lu, Shanghai 200032, China.
Abstract:
A relay catalytic system that integrates visible-light-enabled Ir-catalyzed asymmetric allylic etherification and dearomative [2 + 2] photocycloaddition has been developed. Unlike conventional ground-state asymmetric allylic dearomatization, this strategy takes advantage of the reactivity of triplet-state indoles. A diverse array of thermally disfavored cyclobutane-fused indolines was achieved in up to 92% yield with excellent diastereo- and enantioselectivities (up to >20:1 dr, >99% ee). Mechanistic studies, including control experiments and intermediate isolation, revealed that the irradiation of CHCl3 with blue LEDs generates HCl in situ, promoting the allylic substitution step. Kinetic analysis and "same excess" experiments indicated that photocycloaddition accelerates the preceding allylic substitution by consuming the allyl ether intermediate, thereby enabling the relay catalysis to achieve a synergistic "1 + 1 > 2" effect.
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