D.E. Jung et al. / Journal of Organometallic Chemistry 724 (2013) 40e44
43
intermediate A. Except for benzene, all the unsaturated compounds,
2b, 2c, and cyclohexene, can react with 1a to yield the hydro-
silylation products, 3b, 3c and 5, respectively.
Table 1 (entry # 1e5). To check for the optimal molar ratio of
reactants, 16.40 g (121.1 mmol), 8.20 g (60.5 mmol), and 4.90 g
(36.2 mmol) of 1a were reacted with 2.00 g (30.3 mmol) of 2a,
respectively. The results are summarized in Table 1 (entry # 6e8).
In conclusion, we describe a rare example of a thermal hydro-
silylation of cyclic alkadienes with 1a affording the hydrosilylated
products in moderate to good yields without the use of a catalyst.
Additionally, the thermal reaction of 2a with 1a is a one-pot
synthesis affording cyclopentenylchlorosilane (3a) in good yield.
Although these reactions require the relatively high temperature of
250 ꢀC, they remain simple and require no catalyst. Importantly, the
mixture of the two isomers of exo- and endo-dicyclopentadene
(2a0), which are cheap and commercially available in large scales,
can be used as a starting material in place of 2a. This does not
require the use of an additional thermal cracking process of 2a0 to
2a and its subsequent distillation. This reaction is a possible
method for SieC bond formation for the synthesis of cyclo-
alkenylchlorosilanes, which are expected to be utilized as coupling
agents for composites of inorganic oxide particles and olefin poly-
mers within the plastics industry.
3.3. Thermal hydrosilylation of dicyclopentadiene (2a0) with
trichlorosilane (1a)
Following the same procedure as described in the general
procedure, the reaction of 1a (12.30 g, 90.8 mmol) with 2a0 (2.00 g,
15.1 mmol, 97:3 mixture of exo- and endo-) was carried out at
250 ꢀC for 1 h. 3a was obtained in 82% yield.
In a scaled-up preparation, a 250-mL dried stainless steel tube
was charged commercial 2a0 (25.00 g, 189.1 mmol, 97:3 mixture of
exo- and endo-) and 1a (102.50 g, 756.7 mmol) under an atmo-
sphere of nitrogen. The reaction was carried out at 250 ꢀC for 1 h.
The excess 1a was removed under vacuum, and 62.51 g (82%) of 3a
was isolated by vacuum distillation. And the residue was bulb-to-
bulb vacuum distilled to give 4.63 g of a mixture of high boilers,
which contains four isomers of [4 þ 2] cycloadducts 4 (CAS no.
14579-12-5) in 7:90:1:2 ratio (GC area %).
3. Experimental
3.1. General comments
3.4. Thermal reaction of dicyclopentadiene (2a0) with
methyldichlorosilane (1b)
Allreactionsandmanipulationswere carriedout undera nitrogen
atmosphere usingcannulatechniques. Solventsweredriedaccording
to standard procedures. Trichlorosilane, methyldichlorosilane,
cyclopentene, cyclohexene, 1-hexene, and dicyclopentadiene were
purchased from Aldrich Chem. Co or TCI and used without further
purification. 1,3-Cyclohexadiene and 1,4-cyclohexadiene were
purchased from Aldrich Chem. Co and purified by simple distillation
before use. Cyclopentadiene was freshly prepared by thermal dedi-
merization of dicyclopentadiene before use. The reaction products
were analyzed by gaseliquid chromatography (GLC) over a packed
column (10% OV-101 on 80e100 mesh Chromosorb W/AW, 1/
8 in. ꢁ1.5 m) or a capillary column (SE-30, 30 m) using a Varian 3300
gas chromatograph equipped with a thermal conductivity detector
(TCD). The yields of products were calibrated with the GLC response
factor. The samples for characterization were purified by a prepara-
tive GLC using a packed column (20% OV-101 on 80e100 mesh
ChromosorbP/AW,1/8 in. ꢁ 4 m)with a DS6200 gaschromatography
(Donam Instruments Inc.) equipped with a TCD. NMR spectra were
recorded on a Bruker Avance 300 spectrometer (300 MHz for 1H;
75 MHz for 13C) or a Varian Gemini 300 spectrometer (60 MHz
for 29Si) using CDCl3 as a solvent. The chemical shifts are given in
ppm relative to the standards as follows: CHCl3 7.25 ppm (1H),
CDCl3 central transition 77.0 ppm (13C), and external SiMe4
0.0 ppm (29Si). GC/MS analyses were conducted on a HP 6890/5973
system (70 eV, EI) equipped with a capillary column (HP-1, i.d.
0.2 mm ꢁ 25 m). Elemental analyses were performed by the
Advanced Analysis Center of the Korea Institute of Science and
Technology.
Following the same procedure as described in the general
procedure, a 1 h reaction of a 97:3 mixture of exo- and endo-2a0
(2.00 g, 15.1 mmol), 1b (10.42 g, 90.6 mmol), and n-dodecane
(1.00 g) at 250 ꢀC afforded 3.2 g (29%, based on the amount of 2a0
used) of (2-cyclopentenyl)methyldichlorosilane (3ba, CAS no.
68559-08-0) [21] as well as other high boilers, which GC/MS
analysis indicated to be polycyclic compounds formed by the self-
[4 þ 2] cycloaddition of 2a [20].
3.5. Thermal reaction of 1,3-hexadiene (2b) with trichlorosilane (1a)
Following the same procedure as described in the general
procedure, the reactions of 2b (2.00 g, 25.0 mmol), 1a (10.10 g,
74.6 mmol), and n-dodecane (1.00 g) as an internal standard were
carried out at temperatures ranging from 170 ꢀC to 250 ꢀC. The
yields of 3b (CAS no. 18139-74-7), 3c (CAS no. 10137-69-6), 5 (CAS
no. 98-12-4), and 2b0 (CAS no. 2808-38-0) are based on the amount
of 2b used and were calculated using n-dodecane as an internal
standard. The results are summarized in Table 2 (entry # 9e12).
3.6. Thermal reaction of 1,4-hexadiene (2c) with trichlorosilane (1a)
Following the same procedure as described in the general
procedure, the reactions of 2c (2.00 g, 25.0 mmol), 1a (10.10 g,
74.6 mmol), and n-dodecane (1.00 g) were carried out at various
temperature between 170 ꢀC and 250 ꢀC. The yields of 3, 3c, 5, and
2b0 (CAS no. 2808-38-0) are based on the amount of 2c used and
were calculated using n-dodecane as an internal standard. The
results are summarized in Table 3 (entry # 13e16).
3.2. General procedure for optimizing thermal hydrosilylation of
cyclopentadiene (2a) with trichlorosilane (1a)
Acknowledgments
In a typical experiment reactants 1a (12.30 g, 90.8 mmol), 2a
(2.00 g, 30.3 mmol), and n-dodecane (1.00 g) as an internal stan-
dard were charged into a 25-mL dried stainless tube under an
atmosphere of nitrogen. After the tube was sealed with a cap, the
reactions were carried out at temperatures ranging from 170 to
270 ꢀC. The progress of the reaction was monitored by GLC. The
yields of 3a (CAS no. 14579-09-0), 4 (CAS no. 14579-12-5), and 2a0
are based on the amount of 2a used and were calculated using
n-dodecane as an internal standard. The results are summarized in
This research was supported by the Korea Institute of Science
and Technology.
References
[1] B. Marciniec, Hydrosilylation: a Comprehensive Review on Recent Advances,
Springer, New York, 2008.
[2] L.N. Lewis, J. Stein, Y. Gao, R.E. Colborn, G. Hutchins, Platinum Met. Rev. 41
(1997) 66e75.