Tethered 1,2-Si-Group Migrations in Radical-Mediated Ring Enlargements of Cyclic Alkoxysilanes: An EPR Spectroscopic and Computational Investigation

John C. Walton, Ryutaro Kanada, Takeaki Iwamoto, Satoshi Shuto, Hiroshi Abe

Research output: Contribution to journalArticlepeer-review

2 Citations (Scopus)

Abstract

5- to 6-member ring enlargements of 3-oxa-2-silacyclopentylmethyl to 4-oxa-3-silacyclohexyl radicals were investigated by EPR spectroscopy and QM computations of model indano-oxasilacyclopentane and oxasilinanyl compounds. Both experimental and computational evidence favored a mechanism via a concerted 1,2-migration of the "tethered" Si-group. Thus, the "forbidden" 1,2-Si-group migration from carbon to carbon becomes allowed when the Si-group is "tethered". The EPR data from 3-oxa-2-silacyclopentylmethyl radicals disclosed ground state conformations having semioccupied p-orbitals close to antiperiplanar with respect to their β-Si-C bonds, but indicated Si-hyperconjugation (β-silicon effect) was insignificant in radicals. Kinetic data was obtained by the steady state EPR method for ring enlargement of indano-3-oxa-2-silacyclopentylmethyl radicals. The scope of the novel rearrangement in terms of other ring types and sizes, as well as the analogous 1,2-migration of "tethered" C-centered groups, was explored computationally.

Original languageEnglish
Pages (from-to)6886-6894
Number of pages9
JournalJournal of Organic Chemistry
Volume82
Issue number13
DOIs
Publication statusPublished - 2017 Jul 7

ASJC Scopus subject areas

  • Organic Chemistry

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