Asymmetric Reductive Homocoupling of Isatin Imines Templated by Chiral Diboron

An efficient asymmetric reductive homocoupling of isatin imines is developed with a chiral diboron template, affording the corresponding chiral vicinal diamines bearing 3,3'-bisoxindole scaffolds in up to 90% yield and 99% ee. The reaction features mild conditions and is compatible with various substitution patterns, signifying the broad applicability of diboron-participated [3,3]-sigmatropic rearrangement for the first time on functionalized ketimines. The unstable nature of chiral vicinal diamine products bearing 3,3'-bisoxindole scaffolds, which are prone to undergo retro-Mannich reaction, complicates the reaction.