Organic Letters
Letter
depicted in Scheme 2. The reaction begins by substitution of
the alkyl tosylate by a cobaltate nucleophile.8,9 This is followed
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Scheme 2. Plausible Catalytic Cycle for the
Silylcarbonylation
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(11) The silylcarbonylation of octyl tosylate under the standard
conditions provided the silyl enol ether product in only 30% yield. See
by CO insertion to afford an acyl cobalt complex. Oxidative
addition of Et3SiH is then followed by a 1,3-silantropic shift to
deliver a cobalt carbene intermediate.8,10 A subsequent 1,2-
hydride shift is then followed by β-hydride elimination to
deliver the silyl enol ether product. Interestingly, the reaction
performs poorly with primary alkyl tosylates,11 which is
potentially a result of the decreased rate of β-hydride
elimination of alkyl cobalt species with less substitution.5
In conclusion, we have developed a cobalt-catalyzed, low
pressure transformation of unactivated alkyl tosylates providing
silyl enol ethers. This process is a rare example of the catalytic
activation of secondary alkyl tosylates. The reaction proceeds
under mild conditions and displays a broad substrate scope in
the production of synthetically versatile silyl enol ethers.
Mechanistic studies are consistent with the direct formation of
product without the presence of aldehyde intermediates.
ASSOCIATED CONTENT
* Supporting Information
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The Supporting Information is available free of charge on the
Experimental procedures and spectral data for all new
AUTHOR INFORMATION
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Corresponding Author
ORCID
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
This work was supported by Award No. R01 GM107204 from
the National Institute of General Medical Sciences.
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Org. Lett. XXXX, XXX, XXX−XXX