Facile access to chiral chromanone-2-carboxylic acids enabled by rhodium-catalyzed chemo- and enantioselective hydrogenation.

Rh-catalyzed highly chemo- and enantioselective hydrogenation of chromone-2-carboxylic acids was successfully established for the first time, providing a wide range of enantiopure chromanone-2-carboxylic acids with excellent results (up to 97% yield and 99% ee) and high efficiency (up to 10 000 TON). The carboxylic group in the substrate was demonstrated to play a vital role and an enantio-induction mode was elucidated by DFT calculation. This hydrogenation protocol provided straightforward access to various bioactive chromanoids.