C O M M U N I C A T I O N S
for reaction with more electron-poor arenes. The reaction of
triethylsilane with a 1:1 molar mixture of trifluorotoluene and
toluene generated a 1.5:1 ratio of products resulting from silylation
of the trifluorotoluene and silylation of toluene (63% yield overall),
and the reaction of tripropylsilane with the more electronically
distinct m-xylene and 1,3-bistrifluoromethylbenzene generated a
of the p-trifluoromethylphenyl triethylsilane remained unreacted.
Moreover, heating of triethylsilyl m-xylene and 10 atm of hydrogen
Me
in a Parr reactor at 200 °C in the presence of either Tp
2
2
PtMe H
Me
or a combination of Tp
2
2
PtMe H, benzene, and triethylsilane did
not generate detectable amounts of m-xylene. Thus, the dehydro-
genative silylation of the arenes appears to be irreversible, even in
a sealed reaction vessel.
3.3:1 mixture of the two products from silylation of the 5-positions
favoring reaction with the electron-poor arene (51% yield overall).
Although one might expect the relatively low selectivity to result
from the high reaction temperature, most organometallic C-H
activations of arenes occur without strong electronic effects.15
In summary, we have reported an acceptorless dehydrogenative
coupling of silane Si-H bonds with aromatic and aliphatic C-H
bonds to form products with new Si-C bonds in high yields. The
rates and scope of this catalytic process must be improved, and
current efforts focus on such reaction development.
Intramolecular dehydrogenative coupling of silanes was also
conducted for the first time in high yield to form both five- and
six-membered organosilicon products (eq 2). Heating of di-
Acknowledgment. We thank the NSF for support of this work.
N.T. thanks the Ministry of Education, Culture, Sports, Science
and Technology, Japan, for support of his stay.
methyl-2-phenylethylsilane (n ) 1 in eq 3) in the presence of 5%
Me
Tp
2
2 2
PtMe H led to the extrusion of H and formation of the cyclic
organosilane in 70% yield. The hydrosilylation of allylbenzene with
diethylsilane in the presence of Wilkinson’s catalyst formed diethyl-
Supporting Information Available: Reaction procedures and
characterization of reaction products. This material is available free of
charge via the Internet at http://pubs.acs.org.
3
-phenylpropylsilane (n ) 2 in eq 2), which underwent cyclization
Me
in the presence of 5% Tp
2
2
PtMe H in 64% yield. These intramo-
lecular processes can be envisioned as a route to bifunctional
products after Tamao-Fleming oxidation of appropriately substi-
tuted cyclization products.16
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1
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(
(
(
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7
reagent was not. Moreover, individual aryl-silicon bond energies
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2
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3
the presence of 1.5 equiv (relative to HSiPr ) of pure p-trifluoro-
methylphenyl triethylsilane (eq 4). If the silylation of arenes was
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(
(
(
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(
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J. AM. CHEM. SOC.
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