Hydrogen borrowing mediated, iron catalyzed, functionalization of Α,Β unsatured alcohols

The design of new and sustainable transformations is one of the most challenging task of our time. Catalytic activation of unreactive substrates is conform to the practice of green chemistry and it is attractive also from an economical point of view. In particular, we focused our attention on the activation of alcohols using hydrogen borrowing (HB) technique.1 We use an iron based catalyst for the HB step, the Knölker complex,2 in combination with an organocatalyst in order to functionalize α,β unsaturated alcohols. After the first oxidation, performed by the metal catalyst, the attack of the nucleophile is controlled by the organocatalyst and leads to the formation of a new stereocenter. There are few examples of stereoselective organocatalyzed reactions using alcohols, in combination with the HB activation.3 Our aim was to enlarge the synthetic applicability of the approach, by exploring different combinations of alcohols and nucleophiles. Scheme 2 alcohols functionalization: References: 1. For a review on alcohols activation see: Malai Haniti S., A. Hamid, Slatford, P. A., and Williams, J. M. J. Adv. Synth. Catal. 2007, 349, 1555 – 1575. Obora, J., ACS Catal. 2014, 4, 3972−3981. 2. Quintard, A. and Rodriguez, J. Angew. Chem. Int. Ed. 2014, 53, 4044 – 4055. 3. Roudier, M., Constantieux, T., Quintard, A., and Rodriguez, J. Org. Lett. 2014, 16, 2802−2805. Quintard, A., Costantieux, T., Rodriguez, J. Angew. Chem. Int. Ed. 2013, 52, 12883.