Evidence That Epoxide-Opening Cascades Promoted by Water Are Stepwise and Become Faster and More Selective After the First Cyclization
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Author(s)
Morten, Christopher J.
Byers, Jeffery A.
Jamison, Timothy F.
Date Issued
January 2011
Journal
Journal of the American Chemical Society
Publisher
American Chemical Society (ACS)
Citation
Morten, Christopher J., Jeffery A. Byers, and Timothy F. Jamison. “Evidence That Epoxide-Opening Cascades Promoted by Water Are Stepwise and Become Faster and More Selective After the First Cyclization.” Journal of the American Chemical Society 133.6 (2011): 1902–1908.
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Author's final manuscript
Abstract
A detailed kinetic study of the endo-selective epoxide-opening cascade reaction of a diepoxy alcohol in neutral water was undertaken using 1H NMR spectroscopy. The observation of monoepoxide intermediates resulting from initial endo and exo cyclization indicated that the cascade proceeds via a stepwise mechanism rather than through a concerted one. Independent synthesis and cyclization of these monoepoxide intermediates demonstrated that they are chemically and kinetically competent intermediates in the cascade. Analysis of each step of the reaction revealed that both the rate and regioselectivity of cyclization improve as the cascade reaction proceeds. In the second step, cyclization of an epoxy alcohol substrate templated by a fused diad of two tetrahydropyran rings proceeds with exceptionally high regioselectivity (endo:exo = 19:1), the highest we have measured in the opening of a simple trans-disubstituted epoxide. The origins of these observations are discussed.
MIT Department
Massachusetts Institute of Technology. Department of Chemistry
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DOI of Published Version
https://doi.org/10.1021/ja1088748
