Journal of the American Chemical Society
Article
Scheme 4. General Catalytic Mechanism As Corroborated by Deuterium Labeling Experiments
wherein ruthenium resides at the oxygen-bearing carbon atom.
This haptomeric preference is presumably due to the negative
inductive effect of oxygen. Protonolytic cleavage of the result-
ing homoallylic ruthenium(II) alkoxide releases the product and
regenerates the starting ruthenium(II) complex.
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CONCLUSIONS
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In summary, we report a direct alkyne-mediated carbonyl
(siloxy)crotylation via redox-triggered carbonyl addition that
is enabled through a unique 1,2-hydride-shift mechanism. This
method directly converts primary alcohols to secondary alcohols
bearing a propionate-based monoketide structural motif. Com-
plete levels of regio- and anti-diastereoselectivity are accompanied
by uniformly high levels of enantioselectivity using a Josiphos
(SL-J009-1) modified ruthenium(II) catalyst. Deuterium label-
ing studies corroborate a novel catalytic mechanism wherein
1,2-hydride migration of a ruthenium-bound alkyne forms an
α,β-unsaturated carbene, which upon protonation delivers a
1,3-disubstituted π-allylruthenium complex. Thus, metal-bound
alkynes are directly converted to chiral allylmetal species in the
absence of intervening allenes. The present transformation con-
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formations that merge the characteristics of carbonyl addition
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ASSOCIATED CONTENT
* Supporting Information
The Supporting Information is available free of charge on the
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S
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Single crystal X-ray diffraction data for 5c (CIF)
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AUTHOR INFORMATION
Corresponding Author
Notes
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The authors declare no competing financial interest.
ACKNOWLEDGMENTS
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The Robert A. Welch Foundation (F-0038) and the NIH-
NIGMS (RO1-GM069445) and the Center for Green Chemistry
and Catalysis are acknowledged for partial support of this
research.
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