“Inverse” Frustrated Lewis Pairs: An Inverse FLP Approach to the Catalytic Metal Free Hydrogenation of Ketones

For the first time have boron-containing weak Lewis acids been demonstrated to be active components of Frustrated Lewis Pair (FLP) catalysts in the hydrogenation of ketones to alcohols. Combining the organosuperbase (pyrr)₃P=NtBu with the Lewis acid 9-(4-CF₃-C₆H₄)-BBN generated an “inverse” FLP catalyst capable of hydrogenating a range of aliphatic and aromatic ketones including N-, O- and S-functionalized substrates and bio-mass derived ethyl levulinate. Initial computational and experimental studies indicate the mechanism of catalytic hydrogenation with “inverse” FLPs to be different from conventional FLP catalysts that contain strong Lewis acids such as B(C₆F₅)₃.