Shedding light on organocatalysis-light-assisted asymmetric ion-pair catalysis for the enantioselective hydrogenation of pyrylium ions

Abstract

A new light-driven asymmetric ion-pair catalysis procedure for the metal-free enantioselective hydrogenation of in situ generated pyrylium ions from readily available chalcones was developed (see scheme). The photo-assisted Brønsted acid catalyzed procedure has broad scope and allows, for the first time, access to valuable 4H-chromenes in good yields and with excellent enantioselectivities.

Keywords: asymmetric catalysis; benzopyrane; chiral ion pair; oxocarbenium ion; reduction.