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

Chemistry

Department of Organic Chemistry, University of Regensburg, Universitätsstraße 31, 93053, Regensburg, Germany.

Published: October 2020

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.

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http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7589390PMC
http://dx.doi.org/10.1002/chem.202003000DOI Listing

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Article Synopsis
  • The Corey-Seebach reagent is a key tool in organic synthesis, created by reacting aldehydes or ketones with 1,3-propanedithiol under acidic conditions and deprotonating with -butyllithium.
  • This reagent enables the successful synthesis of a diverse range of natural products, including alkaloids, terpenoids, and polyketides.
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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.

View Article and Find Full Text PDF

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