Campus Units

Chemistry, Ames Laboratory

Document Type

Article

Publication Version

Published Version

Publication Date

11-1995

Journal or Book Title

Journal of the American Chemical Society

Volume

117

Issue

47

First Page

11695

Last Page

11703

DOI

10.1021/ja00152a010

Abstract

Thermal isomerization of olefins to carbenes via a 1,2-silyl shift was examined by both experiment and theory. No evidence of this rearrangement was found for acyclic vinylsilanes, nor could electronic assistance by silicon be identified in cis, trans isomerizations. Serendipitous synthesis of a 2,4-dimethylene-1,3-disilacyclobutane allowed a kinetic examination of its gas-phase, thermal ring expansion to a 2-methylene-1,3-disilacyclopentene. The Arrhenius parameters (log A = 12.48, Eact = 54.09 kcallmol) are the first to be reported for an olefin-to-carbene rearrangement. The analogous all-carbon system failed to ring expand. Ab initio calculations revealed that this was opposite to any predictions which would be made from ring strain considerations. Calculations showed that for silyl migration the transition state was late and was actually the carbene, while for carbon migration the TS was early and considerably higher in energy than the resulting carbene. The 2-methylene-1-silacyclobutane rearrangement (ref 5) was reexamined to find that reversible ring opening to a 1,4-diradical occurred at temperatures below those required to ring expand via a carbene TS.

Comments

Reprinted (adapted) with permission from Journal of the American Chemical Society 117 (1995): 11695, doi:10.1021/ja00152a010. Copyright 1995 American Chemical Society.

Copyright Owner

American Chemical Society

Language

en

File Format

application/pdf

Included in

Chemistry Commons

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