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Issue 24, 2018
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Transition-metal-free radical cleavage of a hydrazonyl N–S bond: tosyl radical-initiated cascade C(sp3)–OAr cleavage, sulfonyl rearrangement and atropisomeric cyclopropanation

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Abstract

For the first time, the combination of catalytic 1,10-phenanthroline and potassium carbonate enables a radical cleavage of a hydrazonyl N–S bond to deliver a tosyl radical and a diazo compound, along with releasing molecular hydrogen spontaneously. The tosyl radical and hydrogen evolution are witnessed by radical trapping, EPR experiment and gas chromatography. An innovative application of this strategy into metal-free coupling of N-tosylhydrazone and phosphinyl allene provides a one-step synthesis of novel atropisomeric 3-tosyl-1-enyl-cyclopropyl-diphenylphosphine oxide derivatives with excellent diastereoselectivity and E-selectivity. Moreover, these atropisomeric products, verified by 1H-NMR, DFT calculations and X-ray crystallography, are controllably formed. Mechanistic studies indicate that the multistep cascade reaction occurs through radical hydrazonyl N–S bond cleavage, radical C(sp3)–OAr bond cleavage, sulfonyl rearrangement and atropisomeric cyclopropanation.

Graphical abstract: Transition-metal-free radical cleavage of a hydrazonyl N–S bond: tosyl radical-initiated cascade C(sp3)–OAr cleavage, sulfonyl rearrangement and atropisomeric cyclopropanation

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Publication details

The article was received on 14 Aug 2018, accepted on 02 Nov 2018 and first published on 02 Nov 2018


Article type: Research Article
DOI: 10.1039/C8QO00873F
Org. Chem. Front., 2018,5, 3567-3573

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    Transition-metal-free radical cleavage of a hydrazonyl N–S bond: tosyl radical-initiated cascade C(sp3)–OAr cleavage, sulfonyl rearrangement and atropisomeric cyclopropanation

    Y. Chen, T. Liu, J. Zhu, H. Zhang and L. Wu, Org. Chem. Front., 2018, 5, 3567
    DOI: 10.1039/C8QO00873F

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