Photocatalytic Reductive Radical‐Polar Crossover for a Base‐Free Corey–Seebach Reaction.

Donabauer, Karsten; Murugesan, Kathiravan; Rozman, Urša; Crespi, Stefano; König, Burkhard

A metal‐free generation of carbanion nucleophiles is of prime importance in organic synthesis. Herein we report a photocatalytic approach to the Corey–Seebach reaction. The presented method operates under mild redox‐neutral and base‐free conditions giving the desired product with high functional group tolerance. The reaction is enabled by the combination of photo‐ and hydrogen atom transfer (HAT) catalysis. This catalytic merger allows a C−H to carbanion activation by the abstraction of a hydrogen atom followed by radical reduction. The generated nucleophilic intermediate is then capable of adding to carbonyl electrophiles. The obtained dithiane can be easily converted to the valuable α‐hydroxy carbonyl in a subsequent step. The proposed reaction mechanism is supported by emission quenching, radical–radical homocoupling and deuterium labeling studies as well as by calculated redox‐potentials and bond strengths.

ABSTRACTION reactions; CARBANIONS; ORGANIC synthesis; CATALYSIS; BOND strengths

Chemistry - A European Journal, 2020, Vol 26, Issue 57, p12945

0947-6539

Academic Journal

10.1002/chem.202003000