Versatile photocatalytic methods for functionalisation of electron-deficient alkenes

Olefins are among the most abundant and widely available chemical feedstock, indispensable for both the synthetic and biological communities due to their unique reactivity profile. Thus, hydrogenation and hydrofunctionalisation of C-C double bonds are important transformations to access pharmaceutical and chemical compounds that are produced at an industrial scale [1]. The photocatalytic reduction opens a path for the development of greener and safer hydrogenation methodologies, avoiding the use of high-energy, strong reductants as well as the use of pressure equipment. We have developed wide-scope, efficient protocols using Ir-based photocatalysts for the reduction and regioselective hydroaminoalkylation of electron-deficient alkenes [2].

Radical addition to α,β-unsaturated carbonyl compounds has been widely investigated as a useful method for functionalisation at the β-position [3]. The α-aminoalkyl radicals formed by photocatalytic oxidation are highly nucleophilic and consequently prone to attack electron deficient alkenes at β-position via Giese-type reaction. There are examples of stereoselectivity control for this reaction, but regioselectivity is completely predetermined by the nature of the substrate. As a result of our research we were able to direct radical addition to the α-position of α,β-unsaturated esters to produce potentially valuable β-amino acids. Importantly, our method overcomes relevant scope limitations of alternative approaches to these products, such as Mannich-type reactions. 

Natalia A. Larionova, Jun Miyatake Ondozabal, Emily G. Smith, Xacobe C. Cambeiro*
School of Biological and Chemical Sciences – Queen Mary University of London

[1] H.-U. Blaser, F. Spindler and M. Thommen, in The Handbook of Homogeneous Hydrogenation, eds. J. G. de. Vries and C. J. Elsevier, Wiley-VCH, Weinheim, 2007, p. 1279.

[2] N. A. Larionova, J. Miyatake Ondozabal and X. C. Cambeiro. Reduction of electron-deficient alkenes enabled by a photoinduced hydrogen atom transfer. Advanced Synthesis & Catalysis2019, 10.1002/adsc.202000751. 

[3] Some examples: a) A. Millet, Q. Lefebvre, and M. Rueping, Visible‐Light Photoredox‐Catalyzed Giese Reaction: Decarboxylative Addition of Amino Acid Derived α‐Amino Radicals to Electron‐Deficient Olefins, Chem.Eur.J. 2016, 22, p.13464; b) K. Nakajima, Y. Miyake, and Y. Nishibayashi, Synthetic Utilization of α‑Aminoalkyl Radicals and Related Species in Visible Light Photoredox Catalysis, Acc. Chem. Res. 2016, 49, p.1946.

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