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

15 July 2019, Version 1
This content is a preprint and has not undergone peer review at the time of posting.

Abstract

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.

Keywords

hydrostannation reactions

Supplementary materials

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Title
Hale Stannylcyclopropyl Vinyl Radical Probe SI
Description
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Supplementary weblinks

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