Titanocene-catalyzed carbosilylation of alkenes and dienes using alkyl halides and chlorosilanes

Article abstract of DOI:10.1021/jo000483p

A new method for regioselective carbosilylation of alkenes and dienes has been developed by the use of a titanocene catalyst. This reaction proceeds efficiently at 0 °C in THF in the presence of Grignard reagents by the combined use of alkyl halides (R'-X, X = Br or Cl) and chlorotrialkylsilanes (R₃'Si-Cl) as the alkylating and silylating reagents, respectively. Terminal alkenes having aryl or silyl substituents (YRC=CH₂, Y = Ar or Me₃Si, R = H or Me) afford addition products YRC- (SiR(3))-CH₂R' in good yields, whereas 1-octene and internal alkenes were sluggish. When 2,3-disubstituted 1,3-butadienes were used instead of alkenes, alkyl and silyl units are introduced at the 1- and 4-positions giving rise to allylsilanes in high yields under similar conditions. The present reaction involves (i) addition of alkyl radicals toward alkenes or dienes, and (ii) electrophilic trapping of benzyl- or allylmagnesium halides with chlorosilanes. The titanocene catalyst plays important roles in generation of these actiye species, i.e., alkyl radicals and benzyl- or allylmagnesium halides.

Full text of DOI:10.1021/jo000483p

J . Org. Chem. 2000, 65, 5291-5297
5291
Tita n ocen e-Ca ta lyzed Ca r bosilyla tion of Alk en es a n d Dien es Usin g
Alk yl Ha lid es a n d Ch lor osila n es
Shinsuke Nii, J un Terao,* and Nobuaki Kambe*
Department of Applied Chemistry, Faculty of Engineering, Osaka University,
Suita, Osaka 565-0871, J apan
kambe@ap.chem.eng.osaka-u.ac.jp
Received March 29, 2000
A new method for regioselective carbosilylation of alkenes and dienes has been developed by the
use of a titanocene catalyst. This reaction proceeds efficiently at 0 °C in THF in the presence of
Grignard reagents by the combined use of alkyl halides (R′-X, X ) Br or Cl) and chlorotrialkylsilanes
(R3′′Si-Cl) as the alkylating and silylating reagents, respectively. Terminal alkenes having aryl
or silyl substituents (YRCdCH2, Y ) Ar or Me3Si, R ) H or Me) afford addition products YRC-
(SiR′′3)-CH2R′ in good yields, whereas 1-octene and internal alkenes were sluggish. When 2,3-
disubstituted 1,3-butadienes were used instead of alkenes, alkyl and silyl units are introduced at
the 1- and 4-positions giving rise to allylsilanes in high yields under similar conditions. The present
reaction involves (i) addition of alkyl radicals toward alkenes or dienes, and (ii) electrophilic trapping
of benzyl- or allylmagnesium halides with chlorosilanes. The titanocene catalyst plays important
roles in generation of these active species, i.e., alkyl radicals and benzyl- or allylmagnesium halides.
In tr od u ction
During the course of our study, we wish to report herein
the titanocene-catalyzed regioselective carbosilylation of
alkenes and dienes by the combined use of alkyl halides
and chlorotrialkylsilanes in the presence of Grignard
reagents (eqs 1 and 2).
Carbosilylation of carbon-carbon unsaturated bonds
is a synthetically very useful reaction for introduction of
silicon functionalities into organic molecules with con-
comitant construction of carbon skeletons via carbon-
carbon bond formation. There have already been devel-
oped several methods for the carbosilylation of alkynes.
The simple examples are Lewis acid-catalyzed addition
of allylsilanes1 and palladium-catalyzed addition of
Me3SiCN2a or strained silacyclic compounds such as sila-
cyclopropene,2b -propane,2c and -butanes.2d Vinylsilanes
were also obtained from terminal alkynes by the com-
bined use of Me3SiI and organotin2e or -zinc2f compounds
in the presence of Pd(0). As for the reactions involving
carbon-carbon double bonds, it is known that 1,3-dienes3
and allenes4 are carbosilylated to give allylsilanes, in
which π-allyl palladium species play an important role
as a key intermediate. However, carbosilylation of al-
kenes has not been attained so far. Recently we have
established new methodologies to introduce alkyl or silyl
groups into alkenes and dienes using early transition
metal catalysts such as titanocene5 and zirconocene.6
Resu lts a n d Discu ssion
For example, to a THF solution of styrene, chlorotri-
ethylsilane (1.1 equiv), a catalytic amount of titanocene
dichloride (0.05 equiv), and nBuMgCl (2.2 equiv) was
added tert-butyl bromide (1.1 equiv) at 0 °C for 10 min
under nitrogen, and the solution was stirred for 1 h. The
NMR analysis of the crude mixture indicated the forma-
tion of the addition product (1) in 96%. This reaction is
highly regioselective to yield a single regioisomer pos-
sessing tert-butyl group at the terminal carbon and
triethylsilyl group at the benzylic carbon (Table 1, run
1). It is known that double alkylation5a and double
silylation5b can take place under similar conditions;
however, any byproducts arising from such reactions
were not formed. The use of EtMgCl instead of nBuMgCl
afforded 1 in 50% yield, but 1 was not obtained when
iPrMgBr or PhMgCl was employed. As shown in runs 2,
5, and 6, this reaction proceeds efficiently when second-
ary bromides were used. Primary alkyl bromides can also
be employed as the alkylating reagents, but the reaction
is somewhat less efficient, affording moderate yields of
products (runs 3, 4). When chloro-substituted substrates
were used, the reaction took place site selectively at the
bromo functional group leaving the chloro substituents
(1) Asao, N.; Yoshikawa, E.; Yamamoto, Y. J . Org. Chem. 1996, 61,
4874-4875.
(2) Pd-catalyzed carbosilylation: (a) Chatani, N.; Hanafusa, T. J .
Chem. Soc., Chem. Commun. 1985, 838-839. (b) Sakurai, H.; Ka-
miyama, Y.; Nakadaira, Y. J . Am. Chem. Soc. 1977, 99, 3879-3880.
(c) Saso, H.; Ando, W. Chem. Lett. 1988, 1567-1570. (d) Sakurai, H.;
Imai, T. Chem. Lett. 1975, 891-894. (e) Chatani, N.; Amishiro, N.;
Murai, S. J . Am. Chem. Soc. 1991, 113, 7778-7780. (f) Chatani, N.;
Amishiro, N.; Morii, T.; Yamashita, T.; Murai, S. J . Org. Chem. 1995,
60, 1834-1840.
(3) Obora, Y.; Tsuji, Y.; Kawamura, T. J . Am. Chem. Soc. 1995, 117,
9814-9821.
(4) Wu, M.; Yang, F.; Cheng, C. J . Org. Chem. 1999, 64, 2471-2474.
(5) (a) Terao, J .; Saito, K.; Nii, S.; Kambe, N.; Sonoda, N. J . Am.
Chem. Soc. 1998, 120, 11822-11823. (b) Terao, J .; Kambe, N.; Sonoda,
N. Tetrahedron Lett. 1998, 39, 9697-9698.
(6) (a) Terao, J .; Torii, K.; Saito, K.; Kambe, N.; Baba, A.; Sonoda,
N. Angew. Chem., Int. Ed. Engl. 1998, 37, 2653-2656. (b) Terao, J .;
Watanabe, T.; Saito, K.; Kambe, N.; Sonoda, N. Tetrahedron Lett. 1998,
39, 9201-9204.
10.1021/jo000483p CCC: $19.00 © 2000 American Chemical Society
Published on Web 08/03/2000

5292 J . Org. Chem., Vol. 65, No. 17, 2000
Ta ble 1. Tita n ocen e-Ca ta lyzed Ca r bosilyla tion Usin g Alk yl Ha lid es a n d Ch lor osila n esa
Nii et al.
a
b
For details of reaction conditions and product characterization, see Experimental Section. NMR yield. Isolated yield is in parentheses.
intact, giving rise to 4 in 48% yield (run 4). R-Methyl-
styrene efficiently underwent carbosilylation (run 5), but
styrenes having a substituent (Me or Ph) at the â-posi-
tion did not afford the desired products. In addition to
aryl-substituted alkenes, a vinylsilane underwent car-
bosilylation to give the corresponding gem-disilyl product
(6) in a good yield (run 6). Under similar conditions,
1-octene and 1-phenyl-1-propyne did not give the desired
products.
yields, respectively (runs 10, 11), whereas desired prod-
ucts were not obtained from isoprene and 1,3-butadiene.
A plausible pathway of this reaction is outlined in
Scheme 1 for the case of dienes. Titanocene dichloride
(11) reacts with nBuMgCl to generate dibutyltitanate-
(III) complex (13) via Cp2TiCl7 and butyltitanocene (12).8
One electron transfer from 13 to alkyl halides leads to
the cleavage of the C-X bond to give the corresponding
alkyl radical9 along with dibutyltitanocene (14), which
When 2,3-dimethyl-1,3-butadiene was treated with
tert-butyl bromide and Et3SiCl under identical conditions,
alkyl and silyl units are introduced at the 1- and
4-positions forming 7 in high yield with an E/Z ratio of
96/4 (run 7). It should be noted that secondary and
tertiary alkyl chlorides can be employed as suitable
alkylating reagents in this reaction, giving 7 and 8 in
good yields although longer reaction time was required
(runs 8, 9). Phenyl- and benzyl-substituted 1,3-butadienes
also gave the corresponding products in 82% and 95%
(7) For the formation of Cp2TiCl from Cp2TiCl2 and alkyl Grignard
reagents, see: Martin, H. A.; J ellinek, F. J . Organomet. Chem. 1968,
12, 149-161.
(8) Reaction of Cp2TiCl with nBuLi affords the thermally instable
12, see: (a) Klei, E.; Telgen, J . H.; Teuben, J . H. J . Organomet. Chem.
1981, 209, 297-307. (η5-C5Me5)2TinPr was formed by the reaction of
(η5-C5Me5)2TiCl with nPrMgBr, see: (b) Luinstra, G. A.; ten Cate, L.
C.; Heeres, H. J .; Pattiasina, J . W.; Meetsma, A.; Teuben, J . H.
Organometallics 1991, 10, 3227-3237.
(9) It is known that alkyl radicals are generated in the titanocene-
catalyzed reduction of alkyl bromides with iPrMgBr. Rilatt, J . A.;
Kitching, W. Organometallics 1982, 1, 1089-1093.

Titanocene-Catalyzed Carbosilylation
J . Org. Chem., Vol. 65, No. 17, 2000 5293
Sch em e 1. A P la u sible P a th w a y of Tita n ocen e-Ca ta lyzed Ca r bosilyla tion of Dien es
ascribable to the coupling with the four equivalent
R-hydrogens of the two butyl groups of 13. This is
quite similar to the ESR spectrum of [Cp2TiEt2]- Li+ (g
) 1.991, 2.3 G) generated by the reaction of Cp2TiCl2 with
EtLi.12 Addition of cyclohexyl bromide into the THF
solution of 13 quickly changed the color to green, and
the ESR signal disappeared. This result is in accord with
the SET process in Scheme 1 (13 to 14).
To confirm the radical mechanism for the carbon-
carbon bond forming step, we carried out the reaction of
styrene using (bromomethyl)cyclopropane as the alky-
lating reagent. This reaction afforded the sole carbosi-
lylation product (18) having 3-butenyl units at the
terminal carbon in 49% yield, and the corresponding
product containing cyclopropylmethyl group was not
detected in the resulting mixture (eq 3). This result can
be explained by the evidence that the rate constant of
the ring opening of cyclopropylmethyl radical, k ) 1.3 ×
108 s-1 at 25 °C,13 is much faster than the addition of
primary radicals to styrene, k ) 5.4 × 104 M-1 s-1 at
25 °C.14 Since the rearrangement of cyclopropylmeth-
ylmagnesium bromide to CH2dCHCH2CH2MgBr is a
slow process with t1/2 ) 30 h in THF at 27 °C,15 it is
unlikely that alkylation at the terminal carbon is an
F igu r e 1. ESR spectrum of [Cp2TinBu2]-MgCl+.
readily forms Cp2Ti (15) via â-hydrogen elimination.10
Addition of thus-formed alkyl radical to a diene at the
terminal carbon affords allyl radical species, which
recombines with 15 to give the corresponding allyl
titanium complex (16). Subsequent transmetalation11 of
n
16 with BuMgCl gives the corresponding allyl Grignard
reagent (17) along with regeneration of 12. Then 17
reacts with a chlorosilane to give carbosilylation product.
Arylalkenes may react similarly via benzylic, instead of
allylic, intermediates. The evidence shown below sup-
ports this reaction pathway.
(12) Brintzinger, H. H. J . Am. Chem. Soc. 1967, 89, 6871-6877.
(13) Maillard, B.; Forrest, D.; Ingold, K. U. J . Am. Chem. Soc. 1976,
98, 7024-7026.
(14) Citterio, A.; Arnoldi, A.; Minisci, F. J . Org. Chem. 1979, 44,
2674-2682.
(15) Silver, M. S.; Shafer, P. R.; Nordlander, J . E.; Ruchardt, C.;
Roberts, J . D. J . Am. Chem. Soc. 1960, 82, 2646-2647.
(16) (C5Me5)2Ti(CH2dCH2) complex has been isolated and well
catalyzed. The crystal structure of this complex is more similar to a
(titanacyclopropane) δ-coordination rather than a π-coordination struc-
ture, see: Cohen, S. A.; Auburn, P. R.; Bercaw, J . E. J . Am. Chem.
Soc. 1983, 105, 1136-1143.
(17) Martin, H. A.; J ellinek, F. Angew. Chem. 1964, 76, 274. Chen,
J .; Kai, Y.; Kasai, N.; Yasuda, H.; Yamamoto, H.; Nakamura, A. J .
Organomet. Chem. 1991, 407, 191-205.
First, we tested the intermediacy of a Ti(III) ate
complex as follows. Cp2TiCl2 (0.025 M) was treated with
n
a large excess of BuMgCl (1 M) at 0 °C in THF. The
ESR spectrum of the resulting dark brown solution
(Figure 1) showed a quintet hyperfine splitting at g )
1.989 with a coupling constant of 2.4 G which might be
(10) It is reported that 14 decomposes rapidly at -50 °C forming
15 along with a 1:1 mixture of n-butane and butenes. McDermott, J .
X.; Wilson, M. E.; Whitesides, G. M. J . Am. Chem. Soc. 1976, 98, 6529-
6536.
(11) Transmetalation of vinyltitanocene complexes with PrMgBr is
known. Gao, Y.; Sato, F. J . Chem. Soc., Chem. Commun. 1995, 659-
660.
(18) Allyl Grignard reagents react with chlorosilanes much faster
than alkyl Grignard reagents. For example, a reaction of CH2dCHCH2-
MgCl with nPr3SiCl was complete within 1 min at 0 °C in THF to give
the corresponding allylsilane, whereas only a trace amount (<1%) of
butyltripropylsilane was formed under identical conditions when
nBuMgCl was used.
i

5294 J . Org. Chem., Vol. 65, No. 17, 2000
Nii et al.
(CH2CH2Ph)2 yields Cp2Ti(CH2dCHPh) which then can
undergo ligand exchange with p-methylstyrene, it is
likely that alkyl radicals attack free alkenes rather than
titianocene-alkene complexes.16
To shed light on the active species of the subsequent
silylation step, allyltitanocene complex (24) was prepared
by the reported procedure17 and examined its reactivity
toward chlorosilanes. When a THF solution of 24 and
Et3SiCl (1 equiv) was stirred at 0 °C for 1 h, no reaction
took place. On the other hand, 25 was formed in 73%
yield when a similar reaction was performed in the
t
F igu r e 2. Reaction of p-methylstyrene (2 mmol) with BuBr
(2 mmol) and nPr3SiCl (2 mmol) using PhCH2CH2MgCl (2
mmol) in the presence of Cp2TiCl2 (0.1 mmol) at 0 °C in THF.
n
anionic process. Furthermore, when the reaction of
6-bromo-1-phenyl-1-hexene with Me3SiCl was performed
under the identical conditions, only the cyclized product
(21) was obtained probably via 5-exo cyclization from 19
to 20 (eq 4).
presence of a stoichiometric amount of BuMgCl (eq 6).
These results suggest that chlorosilane reacted with an
ate complex (26) or with allylmagnesium chloride (27)18
which was formed by transmetalation from 24 via 26.
Although a possibility that titanocene ate complexes such
as 26 react directly with chlorosilanes cannot be ruled
out, the following evidence supports that the transmeta-
lation does proceed under the conditions employed. A
reaction of 2,3-dimethyl-1,3-butadiene with cyclohexyl
bromide (1.1 equiv) was conducted at 0 °C for 1 h in the
absence of chlorosilane. Subsequent addition of D2O
afforded monoalkylated compound (28) containing a
deuterium at the allylic positions in 77% yield as a
mixture of regioisomers (eq 7). This result indicates that
the titanocene complex catalyzes the carbon-carbon bond
formation even in the absence of chlorotrialkylsilanes
giving rise to 29.
An alternative route leading to 16 is the addition of
alkyl radicals toward alkenes or dienes moiety coordi-
nated to titanocene rather than toward free molecules.
Such a possibility was examined in the case of styrene.
According to Scheme 1, when PhCH2CH2MgCl is used
n
instead of BuMgCl, styrene should be formed. So, we
carried out the reaction of tert-butyl bromide and
Et3SiCl (1 equiv) with PhCH2CH2MgCl (2.2 equiv) using
5 mol % of Cp2TiCl2 in the absence of alkenes. Under
similar conditions, 1 was obtained in 78% yield as a single
product, indicating that styrene generated in situ was
incorporated in this catalytic cycle (eq 5). We then
n
conducted a similar reaction using Pr3SiCl (1 equiv) as
the silylating reagent in the presence of p-methylstyrene
(1 equiv), and the yields of the products at different
reaction time were plotted in Figure 2. A carbosilylated
product (23) from p-methylstyrene was formed predomi-
nantly at any stage of the reaction over 22, which is
derived from in situ generated styrene. It should also be
noted that only a trace amount of 22 was formed at the
early stage of the reaction (reaction time <1 min)
whereas the yield of 23 increased continually from the
beginning of the reaction. Taking into account these
results and a hypothesis that â-elimination of Cp2Ti-
Con clu sion s
A new method for carbosilylation of alkenes and dienes
has been developed by the aid of a titanocene catalyst.
This reaction proceeds efficiently under mild conditions
using alkyl halides and chlorotrialkylsilanes, which can
rarely been employed in catalytic reactions promoted by
late transition metals. The present reaction involves (i)
addition of alkyl radicals toward alkenes or dienes in the

Titanocene-Catalyzed Carbosilylation
J . Org. Chem., Vol. 65, No. 17, 2000 5295
(51% NMR yield). Purification by HPLC gave 92 mg (41%) of
carbon-carbon bond forming step and (ii) electrophilic
trapping of benzyl- or allylmagnesium halides with
chlorosilanes in the carbon-silicon bond forming step.
The titanocene catalyst plays important roles for gener-
ating active key species to promote these crucial steps,
i.e., (iii) alkyl radicals are formed by electron transfer
from titanocene ate complexes to alkyl halides and (iv)
benzyl- or allylmagnesium halides are formed by trans-
metalation of Ti(III) complexes with Grignard reagents.
1
3. IR (neat) 2955, 2875, 1458, 1016, 782, 699 cm-1; H NMR
(400 MHz, CDCl3) δ 7.23-7.03 (m, 5H), 2.13 (dd, J ) 3.2, 12.4
Hz, 1H), 1.83-1.77 (m, 1H), 1.72-1.68 (m, 1H), 1.40-1.02 (m,
4H), 0.87 (t, J ) 8.0 Hz, 9H), 0.82 (t, J ) 6.8 Hz, 3H), 0.49 (q,
J ) 8.0 Hz, 6H); 13C NMR (100 MHz, CDCl3) δ 143.9, 127.8,
127.8, 124.0, 34.2, 31.7, 29.6, 22.6, 14.1, 7.7, 2.6; MS (EI) m/z
(relative intensity, %) 262 (M+, 17), 235 (6), 234 (20), 233 (100),
117 (6), 115 (24); HRMS calcd for C17H30Si: 262.2117, found
262.2137. Anal. Calcd for
Found: C, 77.65; H, 11.49.
C17H30Si: C, 77.78; H, 11.52.
7-Ch lor o-1-(4-ch r oloph en yl)-1-(tr ieth ylsilyl)h eptan e (4).
To a THF solution (10 mL) of p-chlorostyrene (405 mg, 2.92
mmol), 1-bromo-5-chloropentane (1110 mg, 5.99 mmol),
Et3SiCl (910 mg, 6.03 mmol), and nBuMgCl (0.90 M in THF,
9.00 mmol) was added Cp2TiCl2 (79.5 mg, 0.32 mmol) at 0 °C.
After stirring for 4 h, similar workup gave an orange crude
product (48% NMR yield). Purification by HPLC afforded 419
mg (40%) of 4. IR (neat) 2933, 2875, 2857, 1489, 1012, 837,
Exp er im en ta l Section
Gen er a l Meth od s. THF was distilled just before use from
benzophenone ketyl. 6-Bromo-1-phenyl-1-hexene was prepared
by the reaction of 6-chrolo-1-phenyl-1-hexene19 with LiBr
following a literature.20 Other alkenes, dienes, and Grignard
reagents were used as purchased without further purifica-
tion. Analytical and purification procedures for NMR, IR, MS,
GC-MS, elemental analysis, and HPLC were the same as
mentioned before.5a
1
718 cm-1; H NMR (400 MHz, CDCl3) δ 7.12 (d, J ) 8.4 Hz,
2H), 6.89 (d, J ) 8.4 Hz, 2H), 3.41 (t, J ) 6.7 Hz, 2H), 2.04 (d,
J ) 12.2 Hz, 1H), 1.74-1.59 (m, 4H), 1.30-1.11 (m, 5H), 1.03-
1.00 (m, 1H), 0.81 (t, J ) 8.0 Hz, 9H), 0.42 (q, J ) 8.0 Hz,
6H); 13C NMR (100 MHz, CDCl3) δ 142.4, 129.6, 128.9, 128.0,
45.1, 33.8, 32.7, 29.7, 29.2, 28.7, 26.8, 7.7, 2.5; MS (EI) m/z
(relative intensity, %) 358 (M+, 2), 208 (26), 151 (18), 140 (17),
138 (49), 131 (15), 115 (100), 87 (85), 59 (26); HRMS calcd for
3,3-Dim eth yl-1-p h en yl-1-(tr ieth ylsilyl)bu ta n e (1). Into
a 10 mL glass vessel containing styrene (114 mg, 1.10 mmol),
Et3SiCl (181 mg, 1.20 mmol), and a catalytic amount of
Cp2TiCl2 (13 mg, 0.05 mmol) was added a THF solution of
nBuMgCl (0.90 M in THF, 2.70 mL, 2.43 mmol). tert-Butyl
bromide (169 mg, 1.23 mmol) was added by a syringe to the
solution kept at 0 °C over the period of 10 min under nitrogen.
After stirring for 40 min, ca. 2 mL of 1 N HCl aq was added to
the solution at 0 °C, and the mixture was warmed to 20 °C. A
saturated aqueous NH4Cl solution (50 mL) was added, and
the product was extracted with ether (50 mL), dried over
MgSO4, and evaporated to give an orange crude product (96%
NMR yield). Purification by HPLC with CHCl3 as an eluent
afforded 286 mg (95%) of 1 in pure form. IR (neat) 2953, 2909,
C
C
19H32SiCl2(35Cl): 358.1650, found 358.1648. Anal. Calcd for
19H32SiCl2: C, 63.49; H, 8.97. Found: C, 63.73; H, 9.08.
2-[2-P h en yl-2-(tr ip r op ylsilyl)p r op yl]n or bor n a n e(5). To
a mixture of R-methylstyrene (119 mg, 1.01 mmol), 2-norbornyl
bromide (427 mg, 2.44 mmol), and nPr3SiCl (494 mg, 2.56
mmol) was added nBuMgCl (0.90 M in THF, 4.40 mL, 4.00
mmol). A catalytic of amount of Cp2TiCl2 (24.5 mg, 0.10 mmol)
was added to the solution at 0 °C and stirred for 6 h. The
similar workup gave an orange crude product (85% GC yield).
Purification by HPLC afforded 276 mg (74%) of 5 as a mixture
of isomers with ca. 1:1 ratio indicated by 1H and 13C NMR.
The 1H NMR showed two singlet peaks of methyl protons at
1.36 and 1.31 ppm, which are more reasonably assigned to
those of a diastereomer pair having different configurations
at the benzylic carbons rather than to those of a mixture of
exo, endo isomers with the same stereochemistry at the
benzylic carbons. A 1:1 mixture of diastereomers: IR (neat)
2951, 2867, 1495, 1454, 1064, 804, 787, 745, 699 cm-1; 1H NMR
(400 MHz, CDCl3) δ 7.22-7.01 (m, 5H), 2.26-1.39 (m, 4H),
1.37-0.85 (m, 18H), 0.83 (t, J ) 7.2 Hz, 9H), 0.38 (t, J ) 9.5
Hz, 6H); 13C NMR (100 MHz, CDCl3) δ (147.4, 147.3), (127.5,
127.4), (126.8, 126.6), 123.6 (1 C), (45.1, 44.6), (44.1, 43.6), 42.1
(1 C), (38.2, 38.1), (37.1, 36.2), (36.1, 35.8), (33.5, 33.1), (29.9,
29.6), (28.8, 28.5), (21.4, 21.0), (19.09, 19.05), 18.0 (1 C), (13.93,
13.89); MS (EI) m/z (relative intensity, %) 370 (M+, 17), 287
(2), 245 (3), 212 (37), 187 (6), 157 (100), 115 (51), 73 (15), 59
(6), 45 (6); HRMS (EI) calcd for C25H42Si: 370.3056, found
2876, 1466, 1006, 789, 750, 701 cm-1 1H NMR (400 MHz,
;
CDCl3) δ 7.18-7.02 (m, 5H), 2.28 (d, J ) 11.2 Hz, 1H), 1.89
(dd, J ) 10.4, 11.2 Hz, 1H), 1.57 (d, J ) 10.4 Hz, 1H), 0.87 (t,
J ) 7.6 Hz, 9H), 0.74 (s, 9H), 0.48 (q, J ) 7.6 Hz, 6H); 13C
NMR (100 MHz, CDCl3) δ 145.7, 127.8, 127.7, 123.6, 43.6, 33.1,
30.6, 30.1, 7.7, 2.4; MS (EI) m/z (relative intensity, %) 276 (M+,
12), 248 (21), 247 (100), 115 (31); HRMS calcd for C18H32Si:
276.2273, found 276.2281. Anal. Calcd for C18H32Si: C, 78.18;
H, 11.66. Found: C, 78.20; H, 11.58.
3-Meth yl-1-p h en yl-1-(tr ieth ylsilyl)bu ta n e (2). A mixture
of styrene (93 mg, 0.89 mmol), isopropyl bromide (123 mg, 1.00
n
mmol), Et3SiCl (148 mg, 0.98 mmol), and BuMgCl (0.90 M in
THF, 2.20 mL, 2.00 mmol) was cooled to 0 °C, and Cp2TiCl2
(11 mg, 0.04 mmol) was added. After stirring for 1 h, similar
workup as mentioned above afforded an orange crude product
(85% NMR yield). Purification by HPLC gave 195 mg (84%)
of 2. IR (neat) 2953, 2911, 2875, 766, 727, 713, 700 cm-1; H
1
NMR (400 MHz, CDCl3) δ 7.26-7.03 (m, 5H), 2.28 (dd, J )
2.8, 12.8 Hz, 1H), 1.90 (ddd, J ) 2.8, 12.8, 13.2 Hz, 1H), 1.48-
1.34 (m, 1H), 1.36-1.30 (m, 1H), 0.87 (t, J ) 7.6 Hz, 9H), 0.82
(d, J ) 6.2 Hz, 3H), 0.78 (d, J ) 6.2 Hz, 3H), 0.49 (q, J ) 7.6
Hz, 6H); 13C NMR (100 MHz, CDCl3) δ 143.7, 127.82, 127.80,
123.9, 38.9, 31.6, 26.2, 24.2, 20.8, 7.7, 2.5; MS (EI) m/z (relative
intensity, %) 262 (M+, 12), 234 (18), 233 (100), 232 (10), 115
(8); HRMS calcd for C17H30Si: 262.2117, found 262.2108. Anal.
Calcd for C17H30Si: C, 77.78; H, 11.52. Found: C, 77.64; H,
11.56.
1-P h en yl-1-(tr ieth ylsilyl)p en ta n e (3). A mixture of sty-
rene (90 mg, 0.86 mmol), propyl bromide (119 mg, 0.98 mmol),
Et3SiCl (143 mg, 0.95 mmol), and nBuMgCl (0.90 M in THF,
2.11 mL, 1.90 mmol) was cooled to 0 °C, and then Cp2TiCl2
(11 mg, 0.04 mmol) was added. After stirring for 1 h, similar
workup as mentioned above afforded an orange crude product
370.3048. Anal. Calcd for
Found: C, 80.80; H, 11.37.
C25H42Si: C, 81.00; H, 11.42.
2-[2-T r im e t h y ls ily l-2-t r ip r o p y ls ily l)e t h y l]n o r b o r -
n a n e (6). To a mixture of trimethylvinylsilane (113 mg, 1.13
mmol), 2-norbolnyl bromide (354 mg, 2.02 mmol), and
nPr3SiCl (388 mg, 2.01 mmol) was added nBuMgCl (0.90 M in
THF, 3.30 mL, 3.00 mmol). A catalytic of amount of Cp2TiCl2
(24.5 mg, 0.06 mmol) was added to the solution at 0 °C and
stirred for 6 h. Similar workup gave an orange crude product
(66% GC yield). Purification by HPLC afforded 140 mg (35%)
of 6 as a mixture of diastereomers with ca. 1:1 ratio as in the
case of 5. 13C NMR showed two singlet peaks assinable to
methyl carbons of trimethylsilyl group at 1.00 and 0.86 ppm
with similar intensities. A 1:1 mixture of diastereomers: IR
(neat) 2951, 2926, 2868, 1455, 1247, 1065, 1015, 894, 853, 832,
758, 683 cm-1; 1H NMR (400 MHz, CDCl3) δ 2.15 (s, 1H), 1.95-
1.90 (m, 1H), 1.52-0.87 (m, 17H), 0.94 (t, J ) 7.20 Hz, 9H),
0.59-0.47 (m, 6H), 0.04- -0.12 (m, 1H), 0.02 (s, 9H); 13C NMR
(100 MHz, CDCl3) δ (44.4, 44.1), (40.7, 39.7), (38.5, 38.1), (36.6,
36.5), (35.3, 35.1), (33.0, 32.9), (30.3, 30.2), (29.1, 29.0), 19.0
(3 C), 18.0 (3 C), 16.7 (3 C), (8.57, 8.21), (1.00, 0.86); MS (EI)
(19) 6-Chloro-1-phenyl1-1-hexene was prepared by the reaction of
styrene with 1-bromo-4-chlorobutane in the presence of nBuMgCl (2
M in Et2O) using Cp2TiCl2 as the catalyst (unpublished result). The
details will be published in due course.
(20) Li, X.; Singh, S. M.; Labrie, F. Synth. Commun. 1994, 24, 733-
743.

5296 J . Org. Chem., Vol. 65, No. 17, 2000
Nii et al.
m/z (relative intensity, %) 310 (26), 309 (90), 268 (15), 267 (57),
208 (20), 207 (100), 180 (16), 179 (63), 165 (62), 157 (32), 152
(10), 129 (25), 115 (36), 101 (23), 87 (19), 73 (42), 59 (32), 42
(13); HRMS calcd for C20H41Si2(M-CH3)+: 337.2747, found
337.2721. Anal.Calcd for C21H44Si2: C, 71.50; H, 12.57.
Found: C, 71.28; H, 12.69.
(-CH2-SiEt3); 13C NMR (100 MHz, CDCl3) (Z isomer) δ 144.4,
143.5, 136.1, 133.2, 129.7, 126.9, 126.8, 125.0, 124.7, 42.3, 36.3,
33.2, 26.6, 26.3, 21.2, 7.2, 3.6; MS (EI) m/z (relative intensity,
%) 404 (M+, 100), 375 (16), 116 (10), 115 (75), 87 (33), 59 (10);
HRMS calcd for C28H40Si: 404.2899, found 404.2904. Anal.
Calcd for C14H40Si: C, 83.10; H, 9.96. Found: C, 82.72; H, 9.81.
(E)-1-Cycloh exyl-2,3-d i(p h en ylm eth yl)-4-tr ieth ylsilyl-
2-b u t en e (10). To a mixture of 2,3-dibenzyl-1,3-butadiene
(230 mg, 0.98 mmol), cyclohexyl bromide (326 mg, 2.00 mmol),
Et3SiCl (323 mg, 2.14 mmol), and nBuMgCl (0.90 M in THF,
3.33 mL, 3.00 mmol) was added Cp2TiCl2 (14 mg, 0.06 mmol)
at 0 °C. After stirring for 4 h, similar workup gave an orange
crude product (95% NMR yield). Purification by silica gel
column chromatography with hexane as an eluent afforded 391
mg (92%) of 10 as a mixture of stereoisomers (E/Z ) 80/20):
IR (neat) 2921, 2874, 2851, 734, 698 cm-1; 1H NMR (400 MHz,
CDCl3) (E isomer) δ 7.30-7.17 (m, 10H), 3.42 (s, 4H), 1.95 (d,
J ) 7.1 Hz, 2H), 1.72-1.63 (m, 6H), 1.58 (s, 2 H), 1.49-1.46
(m, 1H), 1.26-1.10 (m, 4H), 0.95 (t, J ) 7.9 Hz, 9H), 0.60 (q,
J ) 7.9 Hz, 6H); NOE difference measurement: irradiation
of methylene protons at δ 1.95 (-CH2-cyclohexyl) caused 3.8%
enhancement of the benzyl protons at δ 3.42, while no
enhancement was observed for methylene protons at δ 1.58
(-CH2-SiEt3); 13C NMR (100 MHz, CDCl3) (E isomer) δ 140.9,
140.7, 131.9, 129.5, 128.3, 128.2, 127.9, 127.8, 125.5, 125.4,
39.4, 39.0, 38.1, 37.9, 33.7, 26.6, 26.5, 17.9, 7.5, 4.3; MS (EI)
m/z (relative intensity, %) 432 (M+, 82), 403 (13), 349 (5), 225
(10), 163 (6), 143 (5), 129 (4), 116 (13), 115 (100), 91 (11), 87
(41), 59 (13); HRMS calcd for C30H44Si: 432.3212, found
(E)-2,3,5,5-Tetr a m eth yl-1-tr ieth ylsilyl-2-h exen e (7). To
a mixture of 2,3-dimethyl-1,3-butadiene (160 mg, 1.94 mmol),
Et3SiCl (598 mg, 3.98 mmol), nBuMgCl (0.90 M in THF, 6.7
mL, 6.0 mmol), and Cp2TiCl2 (25 mg, 0.10 mmol) was added
slowly a THF solution of tert-butyl bromide (0.47 M, 5.00 mL,
2.35 mmol) using a dropping funnel over a period of 1 h at 0
°C. After stirring for 2 h, similar workup gave an orange crude
product (83% NMR yield). Purification by HPLC afforded 387
mg (78%) of 7. 1H NMR shows a mixture of stereoisomers with
an E/Z ratio of 96/4: IR (neat) 2954, 2911, 2876, 1466, 1016,
1
774, 739 cm-1; H NMR (400 MHz, CDCl3) (E isomer) δ 2.00
(s, 2H), 1.65 (s, 3H), 1.63 (s, 3H), 1.54 (s, 2H), 0.95 (t, J ) 7.9
Hz, 9H), 0.90 (s, 9H), 0.55 (q, J ) 7.9 Hz, 6H); NOE difference
measurement: irradiation of methylene protons at δ 2.00
(-CH2-tBu) caused enhancement of the methyl protons at δ 1.65
(6.7%) and 1.63 (2.1%), while no enhancement was observed
for methylene protons at δ 1.54 (-CH2-SiEt3); 13C NMR (100
MHz, CDCl3) (E isomer) δ 128.8, 123.6, 48.3, 33.8, 30.7, 22.5,
22.2, 21.0, 7.7, 4.4; MS (EI) m/z (relative intensity, %) 254
(M+, 30), 225 (67), 197 (27), 115 (100), 87 (21), 59 (16); HRMS
calcd for C16H34Si: 254.2430, found 254.2434. Anal. Calcd for
C
16H34Si: C, 75.50; H, 13.46. Found: C, 75.47; H 13.50.
P r ep a r a tion of 7 Usin g ter t-Bu tyl Ch lor id e. To a
mixture of 2,3-dimethyl-1,3-butadiene (168 mg, 2.04 mmol),
tert-butyl chloride (268 mg, 2.89 mmol), Et3SiCl (460 mg, 3.05
mmol), and nBuMgCl (0.90 M in THF, 6.7 mL, 6.0 mmol) was
added Cp2TiCl2 (25.3 mg, 0.10 mmol) at 0 °C under nitrogen.
After stirring for 6 h, similar workup gave an orange crude
product (76% NMR yield). Purification by silica gel column
chromatography with hexane as an eluent afforded 323 mg
(64%) of 7 as a mixture of stereoisomers (E/Z ) 98/2).
432.3216. Anal. Calcd for
Found: C, 83.39; H, 10.32.
C30H44Si: C, 83.26; H, 10.25.
6-P h en yl-6-tr ieth ylsilyl-1-h exen e (18). To a mixture of
styrene (96 mg, 0.92 mmol), (bromomethyl)cyclopropane (137
mg, 1.02 mmol), Et3SiCl (155 mg, 1.03 mmol), and nBuMgCl
(0.90 M in THF, 2.3 mL, 2.07 mmol) was added Cp2TiCl2 (11
mg, 0.04 mmol) at 0 °C under nitrogen. After stirring for 1 h,
similar workup gave an orange crude product (49% NMR
yield). Purification by HPLC with CHCl3 as an eluent afforded
81 mg (32%) of 18. IR (neat) 3023, 2952, 2934, 2875, 1450,
(E )-1-Cycloh e xyl-2,3-d im e t h yl-4-t r ie t h ylsilyl-2-b u -
ten e (8). To a mixture of 2,3-dimethyl-1,3-butadiene (162 mg,
1.97 mmol), cyclohexyl chloride (591 mg, 4.98 mmol), Et3SiCl
(466 mg, 3.09 mmol), and nBuMgCl (0.90 M in THF, 6.66 mL,
6.00 mmol) was added Cp2TiCl2 (26 mg, 0.11 mmol) at 0 °C
under nitrogen. After stirring for 6 h, similar workup gave an
orange crude product (66% NMR yield). Purification by HPLC
with CHCl3 as an eluent afforded 290 mg (53%) of 8. 1H NMR
as a mixture of stereoisomers (E/Z ) 97/3): IR (neat) 2921,
1
769, 714, 700 cm-1; H NMR (400 MHz, CDCl3) δ 7.24-7.03
(m, 5H), 5.73 (tdd, J ) 6.6, 10.3, 18.5 Hz, 1H), 4.94 (d, J )
18.5 Hz, 1H), 4.89 (d, J ) 10.3 Hz, 1H), 2.14 (dd, J ) 3.2, 12.4
Hz, 1H), 2.08-1.91 (m, 2H), 1.89-1.79 (m, 1H), 1.77-1.66 (m,
1H), 1.45-1.34 (m, 1H), 1.29-1.14 (m, 1H), 0.87 (t, J ) 7.8
Hz, 9H), 0.49 (q, J ) 7.8 Hz, 6H); 13C NMR (100 MHz, CDCl3)
δ 143.7, 138.7, 127.9, 127.8, 124.1, 114.1, 34.0 33.7, 29.3, 28.7,
7.7, 2.5; MS (EI) m/z (relative intensity, %) 274 (M+, 0.5), 246
(21), 245 (100), 217 (6), 115 (15); HRMS calcd for C18H30Si:
274.2117, found 274.2110. Anal. Calcd for C18H30Si: C, 78.75;
H, 11.02. Found: C, 78.45; H, 11.03.
1
2875, 2852, 774, 752, 737 cm-1; H NMR (400 MHz, CDCl3)
(E isomer) δ 1.90 (d, J ) 7.8 Hz, 2H), 1.72-1.62 (m, 3H), 1.62
(s, 3H), 1.58 (s, 3H), 1.53 (s, 2H), 1.45-1.30 (m, 1H), 1.27-
1.05 (m, 4H), 0.94 (t, J ) 8.0 Hz, 9H), 0.93-0.81 (m, 3H), 0.53
(q, J ) 8.0 Hz, 6H); NOE difference measurement: irradiation
of methylene protons at δ 1.90 (-CH2-cyclohexyl) caused
enhancement of methyl protons at δ 1.62 (3.6%) and 1.58
(2.2%), while no enhancement was observed for methylene
protons at δ 1.53 (-CH2-SiEt3); 13C NMR (100 MHz, CDCl3) (E
isomer) δ 126.4, 123.8, 42.5, 37.4, 33.7, 26.9, 26.7, 21.3, 20.8,
19.8, 7.6, 4.4; MS (EI) m/z (relative intensity, %) 280 (M+, 94),
251 (100), 115 (43); HRMS calcd for C18H36Si: 280.2586, found
[P h en yl(tr im eth ylsilyl)m eth yl]cyclop en ta n e (21). To a
mixture of 6-bromo-1- phenyl-1-hexene (189 mg, 0.79 mmol),
Me3SiCl (250 mg, 2.31 mmol), and Cp2TiCl2 (12 mg, 0.05 mmol)
was added THF solution of nBuMgCl (0.90 M, 2.44 mL, 2.20
mmol). After stirring for 1 h, similar workup gave an orange
crude product (87% NMR yield). Purification by HPLC with
CHCl3 as an eluent afforded 156 mg (85%) of 21. IR (neat)
3021, 2952, 2869, 1248, 859, 835, 743, 700 cm-1; 1H NMR (400
MHz, CDCl3) δ 7.24-7.17 (m, 2H), 7.07-6.99 (m, 3H), 2.36-
2.25 (m, 1H), 1.94-1.92 (m, 1H), 1.83 (d, J ) 11.2 Hz, 1H),
1.71-1.32 (m, 5H), 1.25-1.13 (m, 1H), 0.99-0.89 (m, 1H),
-0.066 (s, 9H); 13C NMR (100 MHz, CDCl3) δ 145.2, 127.9,
127.7, 124.0, 43.9, 42.7, 34.4, 33.4, 25.7, 24.2, -1.13; MS (EI)
m/z (relative intensity, %) 232 (M+, 16), 158 (53), 135 (12), 91
(8), 74 (11), 73 (100); HRMS calcd for C15H24Si: 232.1647,
found 232.1649. Anal. Calcd for C15H24Si: C, 77.51; H, 10.41.
Found: C, 77.68; H, 10.61.
280.2567. Anal. Calcd for
Found: C, 76.78; H, 12.74.
C18H36Si: C, 77.06; H, 12.93.
(Z)-1-Cycloh e xyl-2,3-d ip h e n yl-4-t r ie t h ylsilyl-2-b u -
ten e (9). To a mixture of 2,3-diphenyl-1,3-butadiene (209 mg,
1.01 mmol), cyclohexyl bromide (248 mg, 1.52 mmol), Et3SiCl
(247 mg, 1.65 mmol), and nBuMgCl (0.90 M in THF, 2.78 mL,
2.50 mmol) was added Cp2TiCl2 (13 mg, 0.05 mmol) at 0 °C.
After stirring for 2 h, similar workup gave an orange crude
product (82% NMR yield). Purification by HPLC with CHCl3
as an eluent afforded 325 mg (80%) of 9 as a mixture of
stereoisomers (E/Z ) 10/90); IR (neat) 2950, 2922, 2874, 2851,
1-Cycloh exyl-2,3-d im eth yl-4-d eu ter io-2-bu ten e (28a )
an d 4-Cycloh exyl-2,3-dim eth yl-3-deu ter io-1-bu ten e (28b).
To a mixture of 2,3-dimethyl-1,3-butadiene (158 mg, 1.93
1
772, 755, 699 cm-1; H NMR (400 MHz, CDCl3) (Z isomer) δ
n
7.03-6.87 (m, 10H), 2.43 (d, J ) 6.84 Hz, 2H), 2.11 (s, 2H),
1.73-1.56 (m, 5H), 1.48-0.94 (m, 6H), 0.81 (t, J ) 8.0 Hz, 9H),
0.37 (q, J ) 8.0 Hz, 6H); NOE difference measurement:
irradiation of methylene protons at δ 2.11 (-CH2-cyclohexyl)
caused 4.7% enhancement of methylene protons at δ 2.43
mmol), cyclohexyl bromide (367 mg, 2.26 mmol), and BuMgCl
(0.90 M in THF, 4.90 mL, 4.40 mmol) was added Cp2TiCl2 (26
mg, 0.11 mmol) at 0 °C under nitrogen. After stirring for 1 h,
ca. 2 mL of D2O was added to the solution at 0 °C. Similar
workup gave an orange crude product (77% NMR yield).

Titanocene-Catalyzed Carbosilylation
J . Org. Chem., Vol. 65, No. 17, 2000 5297
Purification by HPLC with CHCl3 as an eluent afforded 205.2
mg (64%) of product as a mixture of 28a and 28b. IR (neat)
2921, 2851, 1642, 1448, 1373, 1151, 887 cm-1; MS (EI) m/z
(relative intensity, %) 167 (M+, 62), 123 (25), 85 (100), 71 (54),
70 (42), 56 (35), 55 (78), 42 (12), 41 (31); HRMS calcd for
C12H21D: 167.1783, found 167.1781. Anal. Calcd for C12H21D:
C, 86.14; H and D, 13.86 Found: C, 85.88; H and D, 13.52. An
aliquot of the mixture was subjected to HPLC again using
CHCl3 as an eluent in order to separate these isomers. 28a :
1H NMR (400 MHz, CDCl3) δ 1.91 (d, J ) 7.32 Hz, 2H), 1.66-
1.61 (m, 13H), 1.40-1.37 (m, 1H), 1.24-1.11 (m, 3H), 0.96-
0.82 (m, 2H); 13C NMR (100 MHz, CDCl3) δ 126.4, 124.5, 42.3,
37.1, 33.6, 26.9, 26.7, 20.7, 20.5 (t, J ) 19.4 Hz), 19.1. 28b:1H
NMR (400 MHz, CDCl3) δ 4.66 (s, 2H), 1.74-1.64 (m, 8H),
1.29-1.04 (m, 6H), 0.96 (s, 3H), 0.90-0.77 (m, 2H); 13C NMR
(100 MHz, CDCl3) δ 150.4, 109.0, 43.0, 37.6 (t, J ) 19.7 Hz),
35.2, 33.9, 33.5, 26.9, 26.6, 20.2, 18.8.
Ack n ow led gm en t. This work was supported, in
part, by a Grant-in-Aid from the Ministry of Education,
Science, Sports and Culture, J apan. J .T. thanks the
J apan Society for Promotion of Science for a scholarship.
Thanks are due to the Instrumental Analysis Center,
Faculty of Engineering, Osaka University.
J O000483P