Synthesis of 2-cycloalkyl-4-phenylindenes and the derived ansa-zirconocenes

Article abstract of DOI:10.1007/s11172-008-0217-2

An efficient route to 2-cycloalkyl-4-phenylindenes and the corresponding ansa-zirconocenes with the -SiMe₂- bridge was proposed.

Full text of DOI:10.1007/s11172-008-0217-2

Russian Chemical Bulletin, International Edition, Vol. 57, No. 8, pp. 1661—1664, August, 2008
1661
Synthesis of 2ꢀcycloalkylꢀ4ꢀphenylindenes and the derived ansaꢀzirconocenes
P. V. Ivchenko and I. E. Nifant´ev
Department of Chemistry, M. V. Lomonosov Moscow State University,
1 Leninskie Gory, 119992 Moscow, Russian Federation.
Fax: +7 (495) 939 4523. Eꢀmail: inpv@org.chem.msu.ru
An efficient route to 2ꢀcycloalkylꢀ4ꢀphenylindenes and the corresponding ansaꢀzirconocenes
with the —SiMe2— bridge was proposed.
Key words: indenes, the Friedel—Crafts reaction, the Suzuki reaction, 2ꢀcycloalkylindenes,
ansaꢀzirconocenes, organosilicon compounds.
To study the influence of the geometry of zirconocene
on its catalytic properties, we found it interesting to
obtain ligands whose steric properties would be interꢀ
mediate between those in compounds 1 and 2. In this
context, introduction of the cyclopentyl and especially
cyclobutyl fragments appeared optimal. The cyclopropyl
substituent was discarded for the low stability of the threeꢀ
membered ring under polymerization conditions in the
presence of polymethylaluminoxane (MAO) as an elecꢀ
trophilic cocatalyst.
Zirconocenes of the general formula 1 are efficient
catalysts for propene polymerization.1 Replacement of
the methyl group in position 2 (compound 2) by an isoꢀ
propyl one has been found to appreciably change the
catalytic properties of the complex.2
Ar
R
ZrCl2
R´
SiMe2
Results and Discussion
R
The target products were the simplest symmetric
zirconocenes 3 and 4. Their possible precursors are 2ꢀcycloꢀ
pentylꢀ7ꢀphenylindene (5) and 2ꢀcyclobutylꢀ7ꢀphenylꢀ
indene (6), respectively.
5, 6
Ar
1—4
A convenient route to 2ꢀalkylꢀ4ꢀ and 2ꢀalkylꢀ7ꢀarylꢀ
indenes starts from a sodium derivative of ethyl 2ꢀalkylꢀ
malonate and appropriate 2ꢀ(bromomethyl)biaryl. The
R = R´ = Me (1), cycloꢀC H (3), cycloꢀC H (4);
5
9
4 7
R = Me, R´ = CHMe (2);
2
R = cycloꢀC H (5), cycloꢀC H (6).
5
9
4 7
Scheme 1
Ar
Ar
Ar
Br
COOH
ii
R
i
R
+
Na
a
O
COOEt
COOEt
–
ArB(OH)2,
Pd(0)
R
Br
Br
Br
b
Br
COOH
ii
R
i
R
O
Reagents and conditions: i, 1) EtOH, 2) NaOH, EtOH, ∆, 3) ∆; ii, 1) SOCl2, CH2Cl2, 2) AlCl3, CH2Cl2.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1630—1633, August, 2008.
1066ꢀ5285/08/5708ꢀ1661 © 2008 Springer Science+Business Media, Inc.

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Russ.Chem.Bull., Int.Ed., Vol. 57, No. 8, August, 2008
Ivchenko and Nifant´ev
Scheme 2
catalysis of similar reactions by copper(I) salts has been
earlier illustrated with indenes containing no bulky subꢀ
stituent in position 2.4 In turn, we successfully applied
this catalysis to sterically hindered substrates. ansaꢀ
Zirconocenes 3 and 4 were obtained in a standard way
from dilithium derivatives 13 and 14, respectively, and
ZrCl4 in pentane in the presence of a minimum amount
of ether (Scheme 3). Pure enantiomers were not isolated
by recrystallization. However, reflux of their mixture in
dimethoxyethane in the presence of LiCl for many hours
resulted in almost complete decomposition of the mesoꢀ
forms and only partial decomposition of the chiral forms.
Because of this, recrystallization from ether gave diastereoꢀ
merically pure compounds 3 and 4 in 11 and 9% yields,
respectively.
Na
COOEt
Br
COOEt
Br
i
ii
COOEt
Li
Br
Br
COOH
iii
R
R
Scheme 3
O
7, 76%
8, 73%
9, >98%
10, >98%
Ph
Ph
Ph
R
iv
v
i
R
Ph
R
5,6
O
R
11, 95%
12, 96%
5, 98%
6, 97%
Me Si Me
Ph
R = cycloꢀC H (5, 7, 9, 11), cycloꢀC H (6, 8, 10, 12).
5
9
4 7
ii
t
Reagents and conditions: i, 1) THF, ∆, 2) Bu OK, ∆, 3) 180 °C;
ii, 1) 1,3ꢀdimethyltetrahydroꢀ2(1H)ꢀpyrimidone (DMPU), THF,
2) KOH/MeOH, ∆; iii, 1) SOCl , CH Cl , 2) AlCl , CH Cl ;
R
R
2
2
2
3
2
2
Ph
Me2Si
ZrCl2
reaction is followed by hydrolysis, decarboxylation, and
intramolecular cyclization leading to 2ꢀalkylꢀ4ꢀarylꢀ
indanone1 (Scheme 1, pathway a). An alternative scheme
(pathway b) involves 1ꢀbromoꢀ2ꢀ(bromomethyl)benzene
and the Suzuki crossꢀcoupling3 as the final step. A second
approach seems to be more versatile because of the possiꢀ
bility of widely varying aryl substituents in position 4 of
indene. The resulting indanones are then reduced and
dehydrated to give the target products in high yields.
To obtain compound 5 (Scheme 2), we employed a
synthetic scheme corresponding to pathway b (see Scheme 1).
However, this scheme was unsuitable for the synthesis of
indene 6 because ethyl cyclobutylmalonate is prepared
from expensive bromocyclobutane producing a low yield
in a reaction with a sodium derivative of diethyl malonate.
For this reason, we followed an alternative route starting
from ethyl cyclobutylacetate (Scheme 2). Note that we
were the first to use this approach for the synthesis of
substituted 3ꢀ(2ꢀbromophenyl)propionic acids.
13,14
R
Ph
3,4
R = cycloꢀC H (3, 5, 13), cycloꢀC H (6, 4, 14).
5
9
4 7
Reagents: i, 1) BuLi/Et O, 2) SiMe Cl /CuCN;
2
2
2
ii, 1) BuLi/Et O, 2) ZrCl /pentane.
2
4
To sum up, with the two simplest bisindenyl comꢀ
pounds as examples, we demonstrated the possibility of
the synthesis of 2ꢀcyclopentylꢀ and 2ꢀcyclobutylindenyl
zirconocenes.
Experimental
All experiments were carried out in an inert (argon) atmoꢀ
sphere. For recrystallization of zirconium complexes, allꢀsealed
systems like Schlenk vessels were used. Ether solvents were disꢀ
tilled over metallic sodium in the presence of benzophenone.
Dichloromethane was purified by distillation over CaH2. 2ꢀBromoꢀ
toluene (ACROS), ethyl malonate (ACROS), bromocyclopentane
(ACROS), and diethyl cyclobutaneꢀ1,1ꢀdicarboxylate (Aldrich)
Bisindenyl compounds 13 and 14 containing a dimethylꢀ
silylene bridge were synthesized in high yields by CuCNꢀ
catalyzed reactions of appropriate lithium indenides with
SiMe2Cl2 in ether (Scheme 3). The efficiency of the

Zirconocenes from 2ꢀcycloalkylindenes
Russ.Chem.Bull., Int.Ed., Vol. 57, No. 8, August, 2008
1663
were used as purchased. Ethyl cyclobutylacetate was prepared
from diethyl cyclobutaneꢀ1,1ꢀdicarboxylate according to known
procedures in several steps including the synthesis of cycloꢀ
butanecarboxylic acid,5 cyclobutylmethanol,6 (bromomethyl)ꢀ
cyclobutane,7 and cyclobutylacetic acid. Ethyl cyclopentylꢀ
malonate was synthesized from ethyl malonate and bromoꢀ
cyclopentane.8 1ꢀBromoꢀ2ꢀ(bromomethyl)benzene was prepared
by bromination of 2ꢀbromotoluene.9 1H and 13C NMR spectra
were recorded on a Varian VXRꢀ400 instrument in CDCl3 at 20 °C.
Elemental analysis for hydrogen and carbon was carried out on a
Carlo Erba 1106 automatic analyzer. Samples of oily compounds
for elemental analysis were preheated in a vacuum setup at
70—80 °C to a constant residual pressure (of the order of
10–2 Torr).
J = 1.2 Hz); 11 (br, 1 H, COOH). 13C NMR, δ: 17.9; 26.4; 27.0;
35.9 (CH2); 38.1; 51.5 (CH); 127.2; 128.0; 130.9; 132.7 (CH=);
124.4; 138.3 (C=); 180.7 (COOH). Found (%): C, 55.10; H, 5.29.
C13H15BrO2. Calculated (%): C, 55.14; H, 5.34.
4ꢀBromoꢀ2ꢀcyclopentylindanꢀ1ꢀone (9). Thionyl chloride
(9.6 mL, 135 mmol) and several drops of DMF were added to
a solution of compound 7 (13.11 g, 43.9 mmol) in CH2Cl2
(20 mL). The mixture was stirred at room temperature for 1 h,
refluxed for 2 h, and concentrated under reduced pressure. The
residue was dissolved in CH2Cl2 (30 mL) and added at 0 °C to a
suspension of AlCl3 (8.79 g, 66 mmol) in CH2Cl2 (100 mL). The
reaction mixture was warmed to room temperature, stirred for
4 h, and poured into a mixture of 10% HCl (200 mL) and ice
(100 g). The product was extracted with CH2Cl2 (6×50 mL).
The combined organic extracts were dried with MgSO4 and
concentrated. The yield of product 9 was 12.20 g (>98%), a light
brown oil. 1H NMR, δ: 1.09—1.13 (m, 1 H); 1.44—1.69 (m,
6 H); 1.93—1.98 (m, 1 H); 2.30—2.37 (m, 1 H); 2.76—2.84
(m, 2 H); 3.18 (dd, 1 H, J = 18.4 Hz, J = 8.5 Hz); 7.27 (dd, 1 H,
J = 7.8 Hz, J = 7.5 Hz); 7.69 (d, 1 H, J = 7.5 Hz); 7.75 (d, 1 H,
J = 7.8 Hz). Found (%): C, 60.29; H, 5.50. C14H15BrO.. Calcuꢀ
lated (%): C, 60.23; H, 5.42.
4ꢀBromoꢀ2ꢀcyclobutylindanꢀ1ꢀone (10) was obtained analoꢀ
gously from precursor 8 (11.3 g, 40 mmol). The yield was 10.62 g
(>98%), a light brown oil. 1H NMR, δ: 1.80—2.18 (m, 6 H);
2.80 (m, 2 H); 3.19 (dd, 1 H, J = 18.1 Hz, J = 8.0 Hz); 7.28 (t, 1 H,
J = 7.7 Hz); 7.68 (d, 1 H, J = 7.7 Hz); 7.76 (d, 1 H, J = 7.7 Hz).
13C NMR, δ: 18.7; 25.8; 26.7; 31.5 (CH2); 37.2; 51.7 (CH); 122.5;
129.0; 137.2 (CH=); 122.1; 138.9; 153.3 (C=); 207.2 (C=O).
Found (%): C, 58.98; H, 5.00. C13H13BrO. Calculated (%):
C, 58.89; H, 4.94.
2ꢀCyclopentylꢀ4ꢀphenylindanꢀ1ꢀone (11). Palladium diacetate
(0.31 g, 1.35 mmol) and PPh3 (0.71 g, 2.70 mmol) were added to
a stirred mixture of compound 9 (12.20 g, 43.9 mmol), phenylꢀ
boronic acid (7.51 g, 61.5 mmol), and Na2CO3 (13.03 g, 123 mmol)
in 1,2ꢀdimethoxyethane—water (150 mL : 45 mL). The mixture
was refluxed for 8 h, cooled, and poured into water (0.5 L). The
product was extracted with CH2Cl2 (5×100 mL). The combined
extracts were washed with water, dried with MgSO4, passed
through a short column with silica gel (diameter 10 cm, height
5 cm, CH2Cl2 as an eluent), and concentrated. The yield of
product 11 was 12.12 g (95%). 1H NMR, δ: 1.12—1.15 (m, 1 H);
1.42—1.45 (m, 1 H); 1.53—1.66 (m, 5 H); 1.93—1.98 (m, 1 H);
2.30—2.36 (m, 1 H); 2.76—2.80 (m, 1 H); 2.89 (dd, 1 H,
J = 17.5 Hz, J = 3.7 Hz); 3.29 (m, 1 H); 7.44—7.51 (m, 6 H);
7.60 (dd, 1 H, J = 7.5 Hz, J = 1.2 Hz); 7.80 (dd, 1 H, J = 7.8 Hz,
J = 1.5 Hz). 13C NMR, δ: 25.0; 28.5; 30.1; 30.5 (CH2); 41.1;
50.8 (CH); 122.6; 127.5; 127.8; 128.4; 128.5; 134.6 (CH=);
137.7; 139.1; 140.0; 151.2 (C=); 208.7 (C=O). Found (%):
C, 87.00; H, 7.33. C20H20O. Calculated (%): C, 86.92; H, 7.29.
2ꢀCyclobutylꢀ4ꢀphenylindanꢀ1ꢀone (12) was obtained analoꢀ
gously from precursor 10 (10.62 g, 40 mmol). The yield was
10.11 g (96%), a light brown oil. 1H NMR, δ: 1.82—2.20 (m,
6 H); 2.64—2.70 (m, 1 H); 2.75—2.81 (m, 1 H); 2.88 (dd, 1 H,
J = 17.5 Hz, J = 3.2 Hz); 3.33 (dd, 1 H, J = 17.5 Hz, J = 7.5 Hz);
7.43—7.57 (m, 6 H); 7.63 (dd, 1 H, J = 7.5 Hz, J = 1.2 Hz); 7.79
(dd, 1 H, J = 7.5 Hz, J = 1.4 Hz). 13C NMR, δ: 18.6; 25.8; 26.7;
30.2 (CH2); 37.4; 51.8 (CH); 122.6; 127.5; 127.7; 128.3; 128.4;
134.5 (CH=); 137.4; 139.1; 140.1; 150.9 (C=); 208.0 (C=O).
Found (%): C, 86.91; H, 6.99. C19H18O. Calculated (%): C, 86.99;
H, 6.92.
3ꢀ(2ꢀBromophenyl)ꢀ2ꢀcyclopentylpropionic acid (7). Ethyl
cyclopentylmalonate (24.7 g, 108 mmol) was added to a stirred
suspension of NaH (4.16 g of 60% dispersion in mineral oil;
104 mmol) in THF (400 mL). The mixture was stirred for 2 h.
Then a solution of 1ꢀbromoꢀ2ꢀ(bromomethyl)benzene (25.30 g,
101 mmol) in THF (100 mL) was added at room temperature
and the stirring was continued for an additional 3 h. The reaction
mixture was heated to boiling, cooled, and refluxed with potassium
tertꢀbutoxide (28.00 g, 0.25 mol) and water (4.5 mL) for 16 h.
On cooling, the mixture was poured into ice water (1 L) and the
product was extracted with hexane (4Ѕ100 mL). The aqueous
layer was acidified to pH 1 and the product was extracted with
CH2Cl2 (6×100 mL). The combined organic extracts from the
aqueous layer were dried with MgSO4 and concentrated. The
residue was heated at 180 °C for 40 min. The yield of product 7
was 22.8 g (76%), a dark yellow oil. 1H NMR, δ: 1.30—1.50 (m,
2 H); 1.55—1.80 (m, 5 H); 1.95 (m, 1 H); 2.08—2.14 (m, 1 H);
2.62—2.68 (m, 1 H); 2.88—2.94 (m, 1 H); 3.10—3.15 (m, 1 H);
7.05—7.09 (m, 1 H); 7.14—7.21 (group of m, 2 H); 7.53 (dd,
1 H, J = 7.9 Hz, J = 0.9 Hz). 13C NMR, δ: 24.99; 25.00; 30.52;
30.59; 37.7 (CH2); 42.9; 51.1 (CH); 127.4; 128.2; 130.9; 132.9
(CH=); 124.5; 138.6 (C=); 181.2 (COOH). Found (%): C, 56.48;
H, 5.70. C14H17BrO2. Calculated (%): C, 56.58; H, 5.77.
3ꢀ(2ꢀBromophenyl)ꢀ2ꢀcyclobutylpropionic acid (8). A 1.6 M
solution of BuLi (41.5 mL, 66.4 mmol) in hexane was added at
–20 °C to a solution of diisopropylamine (9.33 mL, 66.4 mmol)
in THF (100 mL). After 45 min, the mixture was cooled to
–78 °C and a solution of ethyl cyclobutylacetate (7.70 g,
54.2 mmol) and 1,3ꢀdimethyltetrahydroꢀ2(1H)ꢀpyrimidone
(DMPU; 7.70 g, 60.2 mmol) in THF (100 mL) was added in
20 min. The mixture was stirred at –78 °C for 45 min and then a
solution of 1ꢀbromoꢀ2ꢀ(bromomethyl)benzene (16.62 g, 66.4 mmol)
in THF (25 mL) was added. The reaction mixture was warmed
to room temperature, stirred for 16 h, and poured into 10% HCl
(0.5 L). The product was extracted with hexane (6×100 mL).
The combined organic extracts were concentrated, dissolved in
methanol (100 mL), and added to a vigorously stirred solution of
KOH (18 g) in methanol—water (100 mL : 20 mL). The resulting
mixture was refluxed for 10 h. On cooling, it was poured into ice
water (1 L) and the product was extracted with hexane (4×100 mL).
The aqueous solution was acidified to pH 1 and the product was
extracted with CH2Cl2 (6×100 mL). The combined organic
extracts were dried with MgSO4 and concentrated. The yield of
product 8 was 11.32 g (73%), a yellow oil. 1H NMR, δ:
1.80—1.95 (m, 4 H); 2.05—2.13 (m, 2 H); 2.55—2.62 (m, 1 H);
2.83—2.98 (m, 3 H); 7.10 (ddd, 1 H, J = 7.5 Hz, J = 9.0 Hz,
J = 2.3 Hz); 7.17—7.23 (m, 2 H); 7.55 (dd, 1 H, J = 7.8 Hz,

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Ivchenko and Nifant´ev
5
2ꢀCyclopentylꢀ7ꢀphenylindene (5). A solution of ketone 11
(12.12 g, 43.8 mmol) in Et2O (40 mL) was added at –40 °C to a
suspension of LiAlH4 (0.50 g, 13.2 mmol) in Et2O (60 mL). The
mixture was warmed to room temperature and stirred for 2 h.
Then 2% HCl (50 mL) was added and the organic phase was
separated. The product was extracted from the aqueous phase
with CH2Cl2 (4×50 mL). The combined organic extracts were
washed with water, dried with MgSO4, and concentrated.
Benzene (150 mL) was added and the mixture was transferred to
an argonꢀfilled flask containing pꢀtoluenesulfonic acid (0.2 g)
and refluxed with a Dean—Stark trap for 2 h. The resulting
yellow solution was washed with water, a solution of KHCO3,
and again water, dried with MgSO4, passed through a short
column with silica gel (diameter 10 cm, height 2 cm, benzene as
an eluent), concentrated, and dried in vacuo. The yield of product
Dichloroꢀµꢀ{1,1´ꢀ(dimethylsilylene)bis[η ꢀ2ꢀcyclopentylꢀ
4ꢀphenylꢀ1Hꢀindene]}zirconium(IV) (3). A solution of nꢀBuLi in
hexane (1.6 mol L–1, 27.5 mL, 44 mmol) was added at –40 °C to a
solution of compound 13 (12.40 g, 21.5 mmol) in Et2O (100 mL).
The mixture was warmed to room temperature, stirred for 3 h,
and concentrated. The resulting yellowꢀorange powder was
suspended in pentane (200 mL) and cooled to –60 °C. Zircoꢀ
nium tetrachloride (5.13 g, 22 mmol) was added. After 5 min,
Et2O (1 mL) was also added. The resulting mixture was graduꢀ
ally warmed to room temperature and stirred for 16 h. The
yellowꢀorange precipitate that formed was filtered off, washed
with pentane, and dried in vacuo. Then 1,2ꢀdimethoxyethane
(150 mL) and LiCl (0.5 g) were added and the mixture was
refluxed on a water bath for 6 h. The product was isolated by
crystallization from dimethoxyethane and recrystallized from
CH2Cl2—Et2O (1 : 1). The yield of the chiral form was 1.7 g
(11%), a yellowꢀorange crystalline solid. Found (%): C, 66.33;
H, 5.86. C42H42Cl2SiZr. Calculated (%): C, 68.45; H, 5.74.
1H NMR, δ: 1.36 (s, 6 H, CH3); 1.17—1.22 (m, 2 H); 1.54—1.74
(m, 12 H); 1.74—2.05 (m, 2 H); 3.25—3.29 (m, 2 H); 6.96 (s,
2 H); 7.11 (dd, 2 H, J = 8.6 Hz, J = 6.8 Hz); 7.37 (d, 4 H,
J = 7.3 Hz); 7.45 (t, 4 H, J = 7.6 Hz); 7.62—7.66 (m, 6 H).
1
5 was 11.23 g (98%), a light yellow oil. H NMR, δ: 1.60—2.10
(m, 8 H); 2.90—3.00 (m, 1 H); 3.50 (s, 2 H); 6.65 (s, 1 H); 7.24
(dd, 1 H, J = 7.2 Hz, J = 1.4 Hz); 7.33—7.45 (m, 3 H); 7.52 (t,
2 H, J = 7.2 Hz); 7.65 (d, 2 H, J = 8.0 Hz). 13C NMR, δ: 25.0;
32.7; 39.8 (CH2); 41.8 (CH); 119.0; 124.2; 124.4; 126.8; 126.9;
128.2; 128.3; (CH=); 137.4; 140.4; 141.3; 146.0; 154.7 (C=).
Found (%): C, 92.22; H, 7.78. C20H20. Calculated (%): C, 92.26;
H, 7.74.
5
Dichloroꢀµꢀ{1,1´ꢀ(dimethylsilylene)bis[η ꢀ2ꢀcyclobutylꢀ
2ꢀCyclobutylꢀ7ꢀphenylindene (6) was obtained analogously
from precursor 12 (10.11 g, 38.5 mmol). The yield was 9.21 g
(97%), a light yellow oil. 1H NMR, δ: 1.86—2.32 (m, 6 H); 3.42
(m, 1 H); 3.43 (s, 2 H); 6.59 (s, 1 H); 7.19 (dd, J = 7.3 Hz,
J = 1.3 Hz); 7.30—7.40 (m, 3 H); 7.48 (t, 2 H, J = 7.8 Hz); 7.58
(d, 2 H, J = 7.6 Hz). 13C NMR, δ: 18.5; 28.8; 38.9 (CH2); 36.8
(CH); 119.2; 124.2; 124.4; 126.8; 126.9; 128.3; 128.4 (CH=);
137.5; 140.5; 141.2; 146.0; 154.8 (C=). Found (%): C, 92.57;
H, 7.43. C19H18. Calculated (%): C, 92.64; H, 7.36.
4ꢀphenylꢀ1Hꢀindene]}zirconium(IV) (4) was obtained analogously
from precursor 14 (10.21 g, 18.6 mmol). The yield of the chiral form
was 1.2 g (9%), a yellowꢀorange crystalline solid. Found (%):
C, 65.49; H, 5.56. C40H38Cl2SiZr. Calculated (%): C, 67.77;
1
H, 5.40. H NMR, δ: 1.34 (s, 6 H, CH3); 1.65—1.89 (m, 8 H);
2.25—2.34 (m, 4 H); 3.65—3.71 (m, 2 H); 7.11 (s, 2 H); 7.16
(dd, 2 H, J = 8.6 Hz, J = 6.8 Hz); 7.35—7.38 (m, 4 H); 7.46
(t, 4 H, J = 7.3 Hz); 7.66 (d, 4 H, J = 8.1 Hz); 7.71 (d, 2 H,
J = 8.6 Hz, CAr—H).
Bis(2ꢀcyclopentylꢀ4ꢀphenylꢀ1Hꢀindenꢀ1ꢀyl)dimethylsilane
(13). A solution of nꢀBuLi in hexane (1.6 mol L–1, 27.2 mL,
43.5 mmol) was added at –40 °C to a solution of compound 5
(11.23 g, 43 mmol) in Et2O (150 mL). The mixture was warmed
to room temperature, stirred for 2 h, and cooled to –60 °C.
Cuprous cyanide (115 mg, 1.29 mmol) and SiMe2Cl2 (2.6 mL,
21.5 mmol) were added. The mixture was warmed to room temꢀ
perature, stirred for 16 h, and diluted with water (10 mL) and
hexane (200 mL). The organic phase was separated, dried with
MgSO4, passed through a short column with silica gel (diameter
10 cm, height 2 cm, benzene as an eluent), and concentrated.
The residue (a glassy pale yellow substance) was dried in vacuo
to a constant weight. Product 13 was further used without addiꢀ
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Chem., 1999, 64, 8242.
1
tional purification. H NMR, δ: –0.16; –0.04; 0.01 (all s, 6 H,
SiCH3); 1.27—2.15; 2.72; 2.88—2.96 (groups of m, 18 H,
cyclopentyl); 3.91; 3.94 (both s, 2 H, CH); 6.81; 6.90 (both s,
2 H, CH=); 7.20—7.63 (group of m, 16 H, CAr—H).
Bis(2ꢀcyclobutylꢀ4ꢀphenylꢀ1Hꢀindenꢀ1ꢀyl)dimethylsilane (14)
was obtained analogously from precursor 6 (9.21 g, 37.3 mmol)
and used subsequently without additional purification. 1H NMR,
δ: –0.23; –0.12; –0.10 (all s, 6 H, Si—CH3); 1.80—2.40; 3.28—2.31;
3.42—3.47 (groups of m, 14 H, cyclobutyl); 3.88; 3.91 (both s,
2 H, CH); 6.91; 6.96 (both s, 2 H, CH=); 7.26—7.64 (group
of m, 16 H, CAr—H).
Received January 30, 2008;
in revised form April 17, 2008