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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

submitted on 13.07.2019, 08:30 and posted on 15.07.2019, 16:46 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.


Leverhulme Trust RPG-2015-438

EPSRC Grant GR/N20959/01

Queen's University Belfast Postgraduate Studentship to HAW


Email Address of Submitting Author


Queen's University Belfast


United Kingdom

ORCID For Submitting Author


Declaration of Conflict of Interest

There are no conflicts of interest to declare