Selective deoxygenative alkylation of alcohols via photocatalytic domino radical fragmentations

Hong-Mei Guo,Xuesong Wu

doi:10.1038/s41467-021-25702-4

Hong-Mei Guo, Xuesong Wu

Open Access

https://doi.org/10.1038/s41467-021-25702-4

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Abstract

The delivery of alkyl radicals through photocatalytic deoxygenation of primary alcohols under mild conditions is a so far unmet challenge. In this report, we present a one-pot strategy for deoxygenative Giese reaction of alcohols with electron-deficient alkenes, by using xanthate salts as alcohol-activating groups for radical generation under visible-light photoredox conditions in the presence of triphenylphosphine. The convenient generation of xanthate salts and high reactivity of sequential C–S/C–O bond homolytic cleavage enable efficient deoxygenation of primary, secondary and tertiary alcohols with diverse functionality and structure to generate the corresponding alkyl radicals, including methyl radical. Moreover, chemoselective radical monodeoxygenation of diols is achieved via selective formation of xanthate salts.

Highlights

The delivery of alkyl radicals through photocatalytic deoxygenation of primary alcohols under mild conditions is a so far unmet challenge
Minisci-type reactions using primary alcohols, including methanol, as alkyl precursors have been achieved under photoredox conditions via α-H abstraction of alcohols and C–O bond cleavage by spin-center shift elimination of water; these approaches are limited to the alkylation of heteroarenes[32,33,34]
Theoretical calculations have demonstrated that alkoxythiocarbonyl radicals III extrude carbonyl sulfide (COS) rapidly through β-scission to produce the corresponding alkyl radicals, including the methyl radical, in three orders of magnitude faster than the loss of carbon dioxide from alkoxycarbonyl radicals[66]

Summary

Introduction

The delivery of alkyl radicals through photocatalytic deoxygenation of primary alcohols under mild conditions is a so far unmet challenge. Redox auxiliaries that include oxalates[14,15,16,17,18,19,20,21,22,23], xanthates[19,24,25,26,27], carboxylates[28,29,30], and ethers[31] have emerged to transform hydroxyl groups into activating groups for alkyl radical generation via C–O bond homolysis under visible-light photoredox conditions (Fig. 1b).

Results

Conclusion