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Fast Ring-Opening of an Intermediary α-Stannyl-β-Cyclopropylvinyl Radical Does Not Support Formation of an α-Stannylvinyl Cation in the O-Directed Free Radical Hydrostannation of Dialkyl Acetylenes

preprint
submitted on 13.07.2019 and posted on 15.07.2019 by Hamish A. Watson, Soraya Manaviazar, Hannah G. Steeds, Karl Hale
O-Directed free radical hydrostannation of a β-cyclopropyl propargylic alcohol probe with stannanes and cat. Et3B in THF/H2O, or PhMe/MeOH, failed to deliver any detectable products of α-stannylvinyl cation capture. Instead only α-stannyl-β-cyclopropylvinyl radical intermediates could be detected, which underwent fast H-atom abstraction and/or cyclopropane ring-opening as a result of fast eliminative β-scission. These outcomes strongly rule against the claimed intermediacy of α-stannylvinyl cations in the O-directed free radical hydrostannation of disubstituted acetylenes, and provide further good supporting evidence for such reactions proceeding by an exclusively free radical O-coordinatively-controlled mechanism.

Funding

Leverhulme Trust RPG-2015-438

EPSRC Grant GR/N20959/01

Queen's University Belfast Postgraduate Studentship to HAW

History

Email Address of Submitting Author

k.j.hale@qub.ac.uk

Institution

Queen's University Belfast

Country

United Kingdom

ORCID For Submitting Author

0000-0002-6756-8763

Declaration of Conflict of Interest

There are no conflicts of interest to declare

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