A Molecularly Defined Iron-Catalyst for the Selective Hydrogenation of α,β-Unsaturated Aldehydes

A selective iron-based catalyst system for the hydrogenation of ,-unsaturated aldehydes to allylic alcohols is presented. Applying the defined iron-tetraphos complex [FeF(L)][BF4] (L=P(PhPPh2)3) in the presence of trifluoroacetic acid a broad range of aldehydes are reduced in high yields using low catalyst loadings (0.05-1mol%). Excellent chemoselectivity for the reduction of aldehydes in the presence of other reducible moieties, for example, ketones, olefins, esters, etc. is achieved. Based on the in situ detected hydride species [FeH(H2)(L)]+ a catalytic cycle is proposed that is supported by computational calculations.