Enantioconvergent Indole Alkylation Using Diols via Oxocarbenium Intermediate by Borrowing Hydrogen To Access...

The asymmetric synthesis of chiral carbonyl compounds bearing remote stereocenters remains an attractive, yet challenging, goal in modern chemical synthesis. Herein, we report an enantioconvergent approach to γ- and δ-chiral ketones from simple racemic diols through a formal indole alkylation mediated by borrowing hydrogen catalysis. Mechanistic investigations revealed the involvement of a transient oxocarbenium intermediate that plays a key role in the transformation. The development of a new class of iridacycle catalysts featuring a chiral pyrroline backbone proved to be essential for achieving high levels of enantioselectivity. This cascade catalysis process proceeds without stoichiometric reagents and enables the efficient synthesis of a broad range of γ- and δ-chiral ketones in high yields and enantiopurity.