Copper( <scp>II</scp> )‐Catalyzed Enantioselective Addition of Alcohols and <i>tert</i> ‐Butyl Hydroperoxide to Tryptanthrin‐Derived Ketimines

Comprehensive Summary Construction of biologically interesting tryptanthrin‐derived N , O ‐ketals was enabled via Cu(II)‐catalyzed enantioselective addition of alcohols and tert ‐butyl hydroperoxide to tryptanthrin‐derived N ‐Boc ketimines. Stereoselective activation of the electrophiles was possible using structurally confined chiral catalysts although such electrophiles suffered from the drawbacks such as low reactivity or steric hindrance around the reaction center. The protocol tolerated variations in both the tryptanthrin part and the alcohol scopes, and the products could be obtained with up to 99% ee and in up to 99% yield. Gram‐scale reaction was possible, and functional group transformations could also be realized. X‐ray diffraction experiments confirmed the configuration of tryptanthrin‐derived N ‐Boc ketimine as well as the absolute configuration of the product.