Work

Experimental and Computational Investigations into Trivalent Phosphorous-Mediated Radical Thiol Desulfurization

Year: 2021

Type: preprint

Abstract: Radical-mediated thiol desulfurization processes using tricoordinate phosphorous reagents are used in a range of applications from small molecule synthesis to peptide modification. A combined experimental and computational examination of the mechanism and kinetics of the radical desulfurization of alkyl thiyl radicals using trivalent phosphorus reagents was performed. Primary alkyl thiols undergo desulfurization between 10^6 to 10^9 M-1s-1 depending on the phosphorus component with either an H-atom transfer step or β-fragmentation of the thiophosphoranyl intermediate may be rate-controlling. While the desulfurization of primary aliphatic thiols showed a marked dependence on the identity of phosphorous reagent used with either a rate-controlling H-atom transfer or -fragmentation, thiols yielding stabilized C-centered radicals showed much less sensitivity. Support for a stepwise S-atom transfer process progressing via a distorted trigonal bipyramidal thiophosphoranyl radical intermediate was obtained from DFT calculated energetics and hyperfine splitting values.

Source: ChemRxiv

DOI: 10.26434/chemrxiv-2021-fgq3c

Authors: John Lopp, Valerie Schmidt

Institution: University of California San Diego

Language: English

Topic: Radical Photochemical Reactions

Subfield: Organic Chemistry

Field: Chemistry

Domain: Physical Sciences

Open Access status: green

Funders: W. M. Keck Foundation, National Institutes of Health, University of California, San Diego, National Institute of General Medical Sciences

Award: Radical-Mediated Atom-Transfer Strategies for Chemical Synthesis