Organic Letters
Letter
two Pd(II) species formed by oxidative addition of silane to
Pd(0) (see the Supporting Information).
XPS studies. P.K. also acknowledges the Royal Thai Government
Fellowship for financial support.
Based on the observations noted above, the following
mechanistic scheme can be proposed (Scheme 6). The silane
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Scheme 6. Proposed Mechanistic Rationale
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reduces Pd(II) to Pd(0), which leads to oxidative addition to the
aryl halide. Either dihydrogen or a palladium hydride in the
medium converts 25 to 26. Palladium hydride can be generated
from Pd(0) and TMDS or via dihydrogen. In either case, the
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dehydrogenative coupling of TMDS21 to give 27, which can
now be hydrolyzed in water to 28 which gives 29 upon
dehydration. Siloxane 29 can polymerize to 30.
In summary, an efficient and relatively environmentally benign
method for dehalogenation of aryl halides has been uncovered
using cat. PdCl2/TMDS under mild conditions in water. Iodides
and mainly aryl bromides can be reduced at ambient temper-
atures, while chlorides require gentle heating to 45−50 °C.
Several functional groups tolerate these conditions, including
aldehydes and ketones. This technology also exploits the
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as a synthetically valuable example of a process where recyclable
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ASSOCIATED CONTENT
* Supporting Information
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S
Experimental procedures and characterization information for all
new compounds. This material is available free of charge via the
AUTHOR INFORMATION
Corresponding Author
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Author Contributions
†These authors contributed equally.
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
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Financial support provided by the NIH (GM 86485) is warmly
acknowledged with thanks. We acknowledge Johnson Matthey
(Tom Colacot) for Pd catalysts, Dr. Tom Mates, Materials
Research Laboratory, UCSB, and NSF DMR 1121053 for the
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Org. Lett. XXXX, XXX, XXX−XXX