Health & Environmental Research Online (HERO)


Print Feedback Export to File
8536845 
Journal Article 
Generation of Phosphoranyl Radicals via Photoredox Catalysis Enables Voltage-Independent Activation of Strong C-O Bonds 
Stache, EE; Ertel, AB; Rovis, T; Doyle, AG 
2018 
ACS Catalysis
ISSN: 2155-5435 
American Chemical Society 
8 
12 
11134-11139 
English 
Despite the prevalence of alcohols and carboxylic acids as functional groups in organic molecules and the potential to serve as radical precursors, C-O bonds remain difficult to activate. We report a synthetic strategy for direct access to both alkyl and acyl radicals from these ubiquitous functional groups via photoredox catalysis. This method exploits the unique reactivity of phosphoranyl radicals, generated from a polar/SET crossover between a phosphine radical cation and an oxygen-centered nucleophile. We show the desired reactivity in the reduction of benzylic alcohols to the corresponding benzyl radicals with terminal H atom trapping to afford the deoxygenated products. Using the same method, we demonstrate access to synthetically versatile acyl radicals, which enables the reduction of aromatic and aliphatic carboxylic acids to the corresponding aldehydes with exceptional chemoselectivity. This protocol also transforms carboxylic acids to heterocycles and cyclic ketones via intramolecular acyl radical cyclizations to forge C-O, C-N, and C-C bonds in a single step. © 2018 American Chemical Society. 
C-O Bond activation; carboxylic acid; phosphoranyl radical; photoredox catalysis; radical cyclization; β-scission