Synergistic Photoenzymatic Anti-Markovnikov Hydroarylation of Olefins via Heteroaryl Radical Intermediates
Prasun Mukherjee, Zayed Alassad, Todd K. Hyster
Abstract
Heteroaromatic alkylations are indispensable reactions for synthesizing biologically active molecules. The anti-Markovnikov hydroarylation of olefins using heteroaryl halides furnishes the product as a single regioisomer; however, catalytic variants are ineffective at controlling the stereochemical outcome of these reactions. Here, we report a synergistic photoenzymatic hydroarylation of olefins using flavin-dependent "ene"-reductases with ruthenium photoredox catalysts. Enzyme homologues were identified, which provide access to both product enantiomers in greater than 80% yield with up to 99:1 er. This method is effective for styrenyl- and unactivated alkenes, highlighting the generality of this approach. The highest yielding system involves a carboxylated photocatalyst with increased affinity for the enzyme. This work expands the types of radical intermediates that enzymes can use for stereoselective intermolecular coupling reactions.