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Photoredox-Catalyzed Reductive Dimerization of Isatins and Isatin-Derived Ketimines: Diastereoselective Construction of 3,3′-Disubstituted Bisoxindoles

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posted on 2017-03-10, 00:00 authored by Chao-Ming Wang, Peng-Ju Xia, Jun-An Xiao, Jun Li, Hao-Yue Xiang, Xiao-Qing Chen, Hua Yang
Reductive dimerization of isatin and its derivatives can be regarded as a step-economical pathway to construct 3,3′-disubstituted bisoxindoles, which was unfortunately accompanied by severe direct reduction as well as low efficiency. A visible-light driven, photoredox-catalytic protocol was developed to readily furnish 3,3′-dihydroxy- (dl-, > 20:1 dr) and 3,3′-diamino-bisoxindoles (meso-, 3.5:1 to 5:1 dr) in moderate to good yields, successfully circumventing the common problem. Two vicinal quaternary carbon centers were effectively assembled under the irradiation of visible light.