1,2,3,4-Tetrasubstituted cyclopentadienes and their applications for metallocenes: Efficient synthesis through zirconocene- and CuCl-mediated intermolecular coupling of two alkynes and one diiodomethane

Article abstract of DOI:10.1002/chem.201300416

1,2,3,4-Tetrasubstituted cyclopentadienes and indene derivatives with identical or different substituents were obtained in good to excellent isolated yields through a zirconocene- and CuCl-mediated intermolecular coupling process. This synthetic procedure involved three organic partners, including one CH ₂I₂, and two different or identical alkynes. Two alkynes or one diyne undergo Cp₂Zr^II-mediated (Cp= η⁵-C₅H₅) pair-selective reductive coupling to afford the corresponding zirconacyclopentadiene derivatives, which react, in the presence of CuCl and 1,3-dimethyl-3,4,5,6-tetrahydro-2(1 H)-pyrimidinone (DMPU), with CH₂I₂ through intermolecular followed by intramolecular coupling to afford the cyclopentadiene derivatives. An application of the prepared tetrasubstituted cyclopentadiene derivatives was demonstrated by the facile synthesis of the corresponding zirconocene complexes [(^4RCp)₂ZrCl₂] and [(^4RCp) ₂ZrR′₂] (R′=Me, Et, or nBu). The unique 1,2,3,4-tetrasubstituted cyclopentadiene ligands and the corresponding metallocenes are expected to have further applications in organometallic chemistry and organic synthesis. Ringing in the changes: A one-pot synthesis of 1,2,3,4-tetrasubstituted cyclopentadienes by zirconocene- and CuCl-mediated intermolecular coupling of two alkynes and diiodomethane (see scheme; Cp=η⁵-C₅H₅; DMPU=1,3-dimethyl-3,4,5,6- tetrahydro-2(1 H)-pyrimidinone) gave products that were successfully applied for the synthesis of the corresponding zirconocene derivatives. Copyright

Full text of DOI:10.1002/chem.201300416

FULL PAPER
DOI: 10.1002/chem.201300416
1,2,3,4-Tetrasubstituted Cyclopentadienes and Their Applications for
Metallocenes: Efficient Synthesis through Zirconocene- and CuCl-Mediated
Intermolecular Coupling of Two Alkynes and One Diiodomethane
Weizhi Geng,[a] Chao Wang,[a] Jie Guang,[a] Wei Hao,[a] Wen-Xiong Zhang,[a] and
Zhenfeng Xi*[a, b]
Abstract: 1,2,3,4-Tetrasubstituted cy-
clopentadienes and indene derivatives
with identical or different substituents
were obtained in good to excellent iso-
lated yields through a zirconocene- and
CuCl-mediated intermolecular coupling
process. This synthetic procedure in-
volved three organic partners, including
one CH2I2, and two different or identi-
cal alkynes. Two alkynes or one diyne
undergo Cp2ZrII-mediated (Cp=h5-
C5H5) pair-selective reductive coupling
to afford the corresponding zirconacy-
clopentadiene derivatives, which react,
in the presence of CuCl and 1,3-di-
tion of the prepared tetrasubstituted
cyclopentadiene derivatives was dem-
onstrated by the facile synthesis of the
corresponding zirconocene complexes
[(4RCp)2ZrCl2] and [(4RCp)2ZrR’2] (R’=
Me, Et, or nBu). The unique 1,2,3,4-
tetrasubstituted cyclopentadiene li-
gands and the corresponding metallo-
cenes are expected to have further ap-
plications in organometallic chemistry
and organic synthesis.
methyl-3,4,5,6-tetrahydro-2
ACHTUNGTRENNUNG
midinone (DMPU), with
through intermolecular followed by in-
tramolecular coupling to afford the cy-
clopentadiene derivatives. An applica-
Keywords: cyclopentadienyl
li-
gands · metallocenes · pair-selective
coupling · transmetallation · zirconi-
um
Introduction
It is well known that the reactivity of metallocenes is signifi-
cantly influenced by the substitution pattern on the cyclo-
pentadienyl ligands.[1–4] For example, Chirik and co-workers
investigated cyclopentadienyl-substituent effects in zircono-
cenes and realized the homogeneous transformation of dini-
trogen into ammonia with a zirconocene containing h5-
C5Me4H ligands.[4] As a consequence, synthetic methods for
multiply-substituted cyclopentadiene derivatives, which are
mostly used as precursors for metallocene complexes, have
always been in great demand.[5–9] Among the multiply-sub-
stituted cyclopentadienes,[5] 1,2,3,4-tetrasubstitution (I,
Scheme 1) is unique, not only because this substitution pat-
tern would increase the solubility and stability of the corre-
sponding metallocenes,[6] but also because the remaining
Scheme 1. 1,2,3,4-Tetrasubstituted cyclopentadienes (I), related indene
derivatives (II), and the corresponding metallocene complexes (III and
IV; L=ligand).
À
C H bond could be functionalized more easily to give new
ligands.[7] However, in contrast to the many reports in the
literature for the synthesis of cyclopentadiene derivatives
with other substitution patterns, reports on the synthesis of
1,2,3,4-tetrasubstituted compounds are rare.[8] The well-
known tetrasubstituted cyclopentadiene is 1,2,3,4-tetra-
AHCTUNGTREGmNNNU ethylcyclopentadiene, which is synthesized from tetra-
methyl-2-cyclopenten-1-one by following the conventional
reduction and dehydrogenation procedure.[9] As a conse-
quence, knowledge of the properties and applications of
metallocenes with 1,2,3,4-tetrasubstituted cyclopentadienyl
ligands (III, Scheme 1) is very limited.[4,10]
In this article, we report an efficient one-pot synthesis of
1,2,3,4-tetrasubstituted cyclopentadiene derivatives through
zirconocene- and CuCl-mediated three-component coupling
of two identical or different alkynes with one CH2I2. Similar-
ly, indene derivatives (II, Scheme 1) and tetrahydroindene
derivatives could also be prepared in excellent yields after
isolation from the corresponding benzyne or diyne with
CH2I2. An application of the prepared 1,2,3,4-tetrasubstitut-
ed cyclopentadiene derivatives was demonstrated by the
[a] W. Geng, Dr. C. Wang, J. Guang, W. Hao, Dr. W.-X. Zhang,
Prof. Dr. Z. Xi
Beijing National Laboratory for Molecular Sciences (BNLMS)
Key Laboratory of Bioorganic Chemistry and
Molecular Engineering of Ministry of Education
College of Chemistry, Peking University, Beijing 100871 (P.R. China)
Fax : (+86)10-62751708
E-mail: zfxi@pku.edu.cn
[b] Prof. Dr. Z. Xi
State Key Laboratory of Organometallic Chemistry
CAS, Shanghai 200032 (P.R. China)
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/chem.201300416.
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facile synthesis of the corresponding zirconocene complexes
[(4RCp)2ZrCl2]. The corresponding dialkyl zirconocene com-
plex could also be obtained efficiently.
in excellent yields after isolation. If unsymmetric alkynes
such as 1-phenyl-1-propyne, 1-phenyl-1-pentyne, and 1-
phenyl-1-hexyne were used, the corresponding cyclopenta-
dienes 2e–g were obtained as the sole double-bond-position-
al isomers. Tetrahydroindene derivative 3a and the double-
bond-positional isomer 3a’ were obtained in 1:2 molar ratio
in 80% combined yield after isolation from the diyne and
CH2I2. However, the phenyl-substituted tetrahydroindene
3b was obtained as a single isomer in 91% yield after isola-
tion.
Results and Discussion
One-pot synthesis of tetrasubstituted cyclopentadienes: Zir-
conacyclopentadienes 1 (Scheme 2) could be readily formed
To investigate the scope of the reaction, we used two dif-
ferent alkynes, such as one diphenylacetylene and one alkyl-
substituted alkyne. As shown in Scheme 3, under the same
Scheme 3. One-pot synthesis of 1,2,3,4-tetrasubstituted cyclopentadienes
5 from Cp2ZrII- and CuCl-mediated coupling of CH2I2 with two different
alkynes.
conditions as those described above, unsymmetric cyclopen-
tadienes 5a and 5b were both obtained in 90% yield after
isolation. When 1-phenyl-1-propyne was used, the corre-
sponding cyclopentadiene 5c was formed selectively in 91%
yield after isolation. The cyclopentadiene derivative 5d,
formed from two aliphatic alkynes, was isolated in 85%
yield. It should be pointed out that such unsymmetrically
substituted cyclopentadienes are not available by other
methods.
Scheme 2. One-pot synthesis of tetrasubstituted cyclopentadienes 2 and
tetrahydroindenes 3 or 3’ from Cp2ZrII- and CuCl-mediated coupling of
CH2I2 with two identical alkynes or one diyne. Cp=h5-C5H5; THF=tet-
rahydrofuran; DMPU=1,3-dimethyl-3,4,5,6-tetrahydro-2ACTHNUTRGNE(UNG 1H)-pyrimidi-
none.
in excellent yields through Cp2ZrII-mediated pair-selective
coupling of two identical or two different alkynes, as report-
ed by the groups of Takahashi, Negishi, and others.[11]
Copper-mediated synthetic applications of zirconacylopenta-
dienes 1 have been extensively studied by Takahashi and co-
workers[12] and by others.[13] Addition of two equivalents of
CuCl to the solution of 1 in THF that was formed in situ
caused the gradual formation of an insoluble yellow precipi-
tate. When three equivalents of DMPU were added to the
mixture, the yellow powder dissolved to form a dark-brown
solution. Two equivalents of CH2I2 were then added, and
the solution was heated to 708C. The reaction was complete
when the color of the solution changed to light yellow. After
cooling of the mixture to room temperature, a normal
workup afforded products 2 in excellent yields after isola-
tion (Scheme 2).
One-pot synthesis of substituted indene derivatives: The de-
velopment of useful methods for the synthesis of substituted
indenes has attracted much attention.[5a–c,g] After the success-
ful development of the above one-pot preparation of cyclo-
pentadiene derivatives, we applied this strategy to the prep-
aration of substituted indenes. As illustrated in Scheme 4,
treatment of [Cp2ZrPh2] with one alkyne afforded zirconain-
dene 6 after the mixture had been stirred for 9 h at 1108C in
toluene.[14] The toluene was evaporated, and the solvent was
changed to THF. After that, CuCl, DMPU, and CH2I2 were
successively added into the reaction mixture. After the reac-
tion mixture had been kept at 708C for 1 h, substituted
indene derivatives 7a–c were obtained.
Both tetraalkyl-substituted cyclopentadienes (2a–c) and
the tetraphenyl-substituted product 2d could be synthesized
Mechanistic aspects: As mentioned above, a relatively high
temperature (708C) was required for the reaction between
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1,2,3,4-Tetrasubstituted Cyclopentadienes and the Corresponding Metallocenes
FULL PAPER
Scheme 4. One-pot synthesis of indene derivatives 7 from Cp2ZrII- and
CuCl-mediated coupling of CH2I2 with one alkyne and one benzyne.
Scheme 6. Synthesis of zirconocene complexes 9 via Cp’Li compounds 8.
1a and CH2I2. By contrast, if CH2ICl was used in the reac-
tion with 1a, room temperature was enough to afford 2a in
8a,b were firstly prepared in 80% yield from the reaction of
compounds 2 and nBuLi. The formation of 8a,b was con-
firmed by NMR spectroscopy. The chemical shifts of the cy-
clopentadienyl ring protons of 8a (d=4.86 ppm) and 8b
(d=5.17 ppm) are shifted upfield compared with those for
CpLi (d=5.64 ppm) due to the electron-donating effect of
the alkyl substituents. The signals for the Cp-ring carbon
atoms connected to protons (d=96.7 ppm in 8a, d=
98.7 ppm in 8b) in the 13C NMR spectra are also shifted up-
field compared with those for CpLi (d=103.5 ppm). The re-
action of these lithio reagents with ZrCl4 proceeded cleanly
to afford the corresponding zirconocenes 9. The structures
of 9a and 9b were determined by single-crystal X-ray struc-
tural analysis (Figure 1 and Table 1).
90% isolated yield, probably because of the higher reactivi-
À1
À
ty of the C I bond in CH2ICl (48.8 kcalmol ) than that in
CH2I2 (50.6 kcalmolÀ1).[15]
Based on all of the above observations and related refer-
ences,[12,13] a proposed reaction mechanism is given in
Scheme 5. If a zirconacyclopentadiene 1 is treated with
Scheme 5. Proposed reaction mechanism.
CuCl, transmetalation of the diene moiety from zirconium
to copper could proceed to form intermediate V. The effect
of DMPU is remarkable: in addition to stabilizing inter-
mediate V, DMPU could also obstruct the homocoupling of
À
V. The high reactivity of the C I bond is essential for the in-
termolecular coupling to generate the intermediate VI and
for reducing the possibility of the homocoupling reaction.
Finally, intramolecular coupling affords the products 2.
Application of 1,2,3,4-tetrasubstituted cyclopentadienes for
the synthesis of metallocenes: To demonstrate the synthetic
utility of these 1,2,3,4-tetrasubstituted cyclopentadienes as
ligands for the corresponding
Figure 1. ORTEP drawings of 9a (left) and 9b (right) with thermal ellip-
soids at 30% probability. Hydrogen atoms are omitted for clarity.
metallocenes and to learn the
properties of such metallo-
cenes, multiply-substituted zir-
Table 1. Bond lengths and angles for 9a,b and similar reported zirconocene compounds.
[Cp2ZrCl2] [(C5Me4H)2ZrCl2] [(C5Et4H)2ZrCl2] (9a) ACHTUNGTRENNU[G (C5Pr4H)2ZrCl2] (9b)
G
R
G
À
Zr Cl1 [ꢁ]
2.437(2)
2.433(18)
2.194(7)
2.488(7)
96.70(7)
2.434(3)
2.434(3)
2.225(3)
2.531(6)
97.61(9)
2.4239(14)
2.437(12)
2.234(4)
2.536(4)
95.27(5)
2.4345(11)
2.4345(11)
2.240(3)
2.546(3)
96.41(8)
conocene complexes
9 were
À
Zr Cl2
(Cl1’) [ꢁ]
(Cent) [ꢁ]
synthesized from metal-ex-
change process via cyclopenta-
dienyl lithium intermediates 8
(Scheme 6).[16] Thus, the cyclo-
pentadienyl lithium reagents
À
Zr Cp
G
À
Zr Cp(av) [ꢁ]
a Cl1-Zr-Cl2
N
a Cp
G
E
131.46(16)
54.45(16)
131.54(19)
55.31(19)
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Z. Xi et al.
The molecular structures of 9a and 9b are shown in
Figure 1. Both structures take a least-repulsion state. Select-
ed bond lengths and angles are given in Table 1. The
Cl-Zr-Cl angle is 95.27(5)8 for 9a and 96.41(8)8 for 9b,
values that are similar to those for [Cp2ZrCl2] and
[(C5Me4H)2ZrCl2].[17a,e] The Cent-Zr-Cent angle (Cent is the
centroid of the Cp ring) of 131.5(2)8 for 9a and 9b is small-
er than the value of 133.1(1)8 for [(C5Me4H)2ZrCl2]. Howev-
er, the dihedral angle between the two Cp planes becomes
larger as the size of the substituents on the Cp ring increases
(H<Me<Et<Pr), which could be attributed to the steric
À
effect of the substitutions. The Zr Cl bond lengths of com-
plexes 9 (2.431(3) ꢁ for 9a and 2.435(1) ꢁ for 9b) are in a
normal range for zirconocene dichlorides. The distances
from the Zr atom to the centriods of the cyclopentadienyl
rings (2.234(4) ꢁ for 9a and 2.240(3) ꢁ for 9b) are larger
than those (2.215–2.225 ꢁ) found in analogous zirconocene
compounds.[17]
Substituted dimethylzirconocene complexes [Cp’2ZrMe2]
have been proved to be useful as catalysts for olefin poly-
merization.[18,19] The zirconocene dichlorides 9 were further
applied for the synthesis of the corresponding dimethylzirco-
Figure 2. ORTEP drawings of 10 with 30% thermal ellipsoids. Hydrogen
À
atoms are omitted for clarity. Selected bond lengths: Zr1 C1 2.242(3),
À
À
À
À
Zr1 C1’ 2.242(2), Zr1 Cp
N
1.402(3) ꢁ; selected angles: C1-Zr1-C1’ 93.2(2), C3-C2-C6 109.6 (2),
Cp(Cent)-Zr1-Cp(Cent) 133.10(17)8.
A
ACHTUNGTRENNUNG
Obviously, the 1,2,3,4-tetrasubstitution pattern played a key
role for the reactivity of the dialkyl zirconocene complexes.
Conclusion
An efficient one-pot synthesis of 1,2,3,4-tetrasubstituted cy-
clopentadienes was realized through zirconocene- and CuCl-
mediated intermolecular coupling of two alkynes and diio-
domethane. These 1,2,3,4-tetrasubstituted cyclopentadienes
were successfully applied for the synthesis of the corre-
sponding zirconocene derivatives. The unique 1,2,3,4-tetra-
substituted cyclopentadiene ligands and the corresponding
metallocenes are expected to have further applications in or-
ganometallic chemistry and organic synthesis.
Scheme 7. Synthesis of dialkyl zirconocene complexes 10–12.
nocenes. As illustrated in Scheme 7, treatment of the zirco-
nocene dichloride 9b with two equivalents of MeLi generat-
ed the dimethylzirconocene complex 10 as a white solid in
91% yield after isolation. The structure was determined by
single-crystal X-ray structural analysis (Figure 2). The
À
Me-Zr-Me angle is 93.2(2)8 and the Me Zr bond length is
Experimental Section
2.243(2) ꢁ, values that are similar to those of dimethylzirco-
nocenes.[18]
General methods: All reactions were conducted under a slightly positive
pressure of dry nitrogen by using standard Schlenk line techniques or
under a nitrogen atmosphere in a Mikrouna Super (1220/750) glovebox.
The nitrogen in the glove box was constantly circulated through a
copper/molecular sieves catalyst unit. The oxygen and moisture concen-
trations in the glovebox atmosphere were monitored by an O2/H2O
Combi-Analyzer to ensure that both were always below 1 ppm. Unless
otherwise noted, all starting materials were commercially available and
were used without further purification. Solvents were purified by an
Mbraun SPS-800 solvent purification system and dried over fresh Na
chips in the glovebox. nBuLi was obtained from Acros. Organometallic
samples for NMR spectroscopic measurements were prepared in the glo-
vebox by using J. Young valve NMR tubes (Wilmad 528-JY). 1H and
13C NMR spectra were recorded on a Bruker-400 spectrometer (FT,
400 MHz for 1 H; 100 MHz for 13C) or a JEOL-AL300 spectrometer (FT,
300 MHz for 1 H; 75 MHz for 13C) at room temperature, unless otherwise
noted. High-resolution mass spectra (HRMS) were recorded on a Bruker
Apex IV FTMS mass spectrometer by using ESI (electrospray ioniza-
tion). Microelemental analyses were performed on an Elemental Ana-
lyzer vario EL apparatus.
It is known that dialkyl zirconocene complexes with b-hy-
drogen atoms, such as [Cp2ZrBu2] and [Cp2ZrEt2], are not
stable. b-Hydride abstraction and reductive elimination
readily take place to generate low-valent Cp2ZrII species,[20]
which have been demonstrated to undergo an oxidative cyc-
lization process with alkynes to afford zirconacyclopenta-
dienes, such as the above-mentioned zirconacyclopenta-
dienes 1, 4, and 6.[11–13] However, if complex 9b, instead of
[Cp2ZrCl2], was applied to the reaction process for the prep-
aration of zirconacyclopentadienes 1, 4, and 6, the corre-
sponding zirconacyclopentadiene derivatives could not be
formed, even at higher temperatures and with prolonged re-
action times. NMR studies indicated that the corresponding
diethylzirconocene complex 11 and dibutylzirconocene com-
plex 12 (Scheme 7) did not undergo the commonly observed
b-hydride abstraction and reductive elimination process.[21]
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1,2,3,4-Tetrasubstituted Cyclopentadienes and the Corresponding Metallocenes
FULL PAPER
One-pot synthesis of tetrasubstituted cyclopentadienes from two alkynes
and one CH2I2: A typical procedure for the preparation of 1,2,3,4-tetrapro-
pylcyclopentadiene (2a): nBuLi (4.8 mmol, 1.6m, 3.0 mL) was added
One-pot synthesis of substituted tetrahydroindenes from one diyne and
one CH2I2: A typical procedure for the preparation of 1,3-dipropyl-4,5,6,7-
tetrahydro-1H-indene (3a): The procedure was the same as that for the
preparation of 2a but instead of 4-octyne (4.0 mmol, 440 mg), tetradeca-
4,10-diyne (2.0 mmol, 380 mg) was used.
dropwise with
a syringe to a THF (10 mL) solution of [Cp2ZrCl2]
(2.4 mmol, 700 mg) at À788C (dry ice/acetone) in a 20 mL Schlenk tube.
After the addition was complete, the reaction mixture was stirred at
À788C for 1 h. Then, 4-octyne (4.0 mmol, 440 mg) was added, and the re-
action mixture was warmed to 258C and stirred at this temperature for
3 h. The mixture was cooled to À788C, and CuCl (396 mg, 4.0 mmol),
DMPU (768 mg, 6.0 mmol), and CH2I2 (1.072 g, 4.0 mmol) were added.
The solution was heated to 708C and kept at this temperature for 1 h.
The reaction mixture was then cooled down to room temperature and
quenched with saturated aqueous NaHCO3. The resulting mixture was
extracted with diethyl ether three times, then washed with water and
brine. The extract was dried over anhydrous MgSO4. The solvent was
evaporated in vacuo to give a yellow oil, which was subjected to a SiO2
chromatography column with hexane as the eluent.
1,3-Dipropyl-4,5,6,7-tetrahydro-1H-indene (3a): Yellow oil; 2:1 mixture
of positional double-bond isomers; 80% combined yield (327 mg);
1H NMR of the mixture (300 MHz, C6D6): d=0.83–0.93 (m, 6H, CH3),
1.04–2.63 (m, 17H, CH2), 5.16–5.40 ppm (m, 1H, CH); 13C NMR of the
major isomer (75 MHz, C6D6): d=14.65 (CH3), 14.83 (CH3), 20.67 (CH2),
22.42 (CH2), 22.92 (CH2), 22.98 (CH2), 23.57 (CH2), 25.22 (CH2), 33.46
(CH), 36.55 (CH2), 45.85ACTHNUTRGNE(NUG CH2), 115.76 (CH), 136.08 (quat C), 146.06
(quat C), 146.39 ppm (quat C); HRMS: calcd for C15H25 [M+H]+:
205.1951; found: 205.1949.
1,3-Diphenyl-4,5,6,7-tetrahydro-2H-indene (3b): Yellow solid; 90% yield
1
(490 mg); H NMR (300 MHz, CDCl3): d=1.71–1.75 (m, 4H, CH2), 2.79–
2.81 (t, J=3.0 Hz, 4H, CH2), 3.74 (s, 2H, CH2), 7.19–7.49 ppm (m, 10H,
CH); 13C NMR (75 MHz, CDCl3): d=23.41 (2CH2), 27.29 (2CH2), 43.78
(CH2), 125.71 (2CH), 126.97 (4CH), 128.36 (4CH), 136.39 (2 quat C),
137.21 (2 quat C), 141.23 ppm (2 quat C); HRMS: calcd for C21H21
[M+H]+: 273.1638; found: 273.1640.
1,2,3,4-Tetrapropylcyclopentadiene (2a): Yellow oil; 93% yield after iso-
lation (436 mg); 1H NMR (300 MHz, CDCl3): d=0.87–0.97 (m, 12H,
CH3), 1.33–1.52 (m, 8H, CH2), 2.14–2.28 (m, 8H, CH2), 2.74 ppm (s, 2H,
CH2); 13C NMR (75 MHz, CDCl3): d=14.37 (2CH3), 14.52 (2CH3), 23.74
(4CH2), 28.10 (2CH2), 30.63 (2CH2), 43.62 (CH2), 138.14 (2 quat C),
140.20 ppm (2 quat C); HRMS: calcd for C17H31 [M+H]+: 235.2420;
found: 235.2422.
One-pot synthesis of unsymmetric tetrasubstituted cyclopentadienes from
two different alkynes and one CH2I2: A typical procedure for the prepara-
tion of 1,2-diethyl-3,4-diphenyl cyclopentadiene (5a): EtMgBr (4.8 mmol,
1.6m, 3.0 mL) was added dropwise with a syringe to a THF (10 mL) solu-
tion of [Cp2ZrCl2] (2.4 mmol, 700 mg) at À788C (dry ice/acetone) in a
20 mL Schlenk tube. After the addition was complete, the reaction mix-
ture was stirred at À788C for 1 h. Then, 1,2-diphenylethyne (2.0 mmol,
356 mg) was added, and the reaction mixture was warmed to 08C and
stirred at this temperature for 3 h. 3-Hexyne (2.0 mmol, 164 mg) was
added, and the reaction mixture was warmed to 258C and stirred at this
temperature for 1 h. The mixture was then cooled to À788C, and CuCl
(396 mg, 4.0 mmol), DMPU (768 mg, 6.0 mmol), and CH2I2 (1.072 g,
4.0 mmol) were added. The solution was heated to 708C and kept at this
temperature for 1 h. The reaction mixture was then cooled down to room
temperature and quenched with saturated aqueous NaHCO3. The result-
ing mixture was extracted with diethyl ether three times, then washed
with water and brine. The extract was dried over anhydrous MgSO4. The
solvent was evaporated in vacuo to give a yellow oil, which was subjected
to a SiO2 chromatography column with hexane as the eluent.
1,2,3,4-Tetrabutylcyclopentadiene (2b): Yellow oil; 86% yield after isola-
tion (499 mg); 1H NMR (400 MHz, C6D6): d=0.88–0.94 (m, 12H, CH3),
1.25–1.51 (m, 16H, CH2), 2.29–2.35 (m, 8H, CH2), 2.71 ppm (s, 2H,
CH2); 13C NMR (100 MHz, C6D6): d=14.31 (2CH3), 14.36 (2CH3), 23.29
(2CH2), 23.43 (2CH2), 26.14 (2CH2), 28.62 (2CH2), 33.31 (2CH2), 33.32
(2CH2), 43.96 (CH2), 137.98 (2 quat C), 140.51 ppm (2 quat C); HRMS:
calcd for C21H39 [M+H]+: 291.3046; found: 291.3048.
1,2,3,4-Tetraethylcyclopentadiene (2c): Yellow oil; 76% yield after isola-
tion (271 mg); the NMR spectra were consistent with the reported
data.[8e]
1,2,3,4-Tetraphenylcyclopentadiene (2d): White solid; 93% yield after iso-
lation (688 mg); the NMR spectra are consistent with the reported
data.[6c]
1,3-Dimethyl-2,4-diphenylcyclopentadiene (2e): Yellow oil; 85% yield
1
(418 mg); H NMR (300 MHz, CDCl3): d=2.03 (s, 3H, CH3), 2.04 (s, 3H,
CH3), 3.40 (s, 2H, CH2), 7.20–7.43 ppm (m, 10H, CH); 13C NMR
(75 MHz, CDCl3): d=14.23 (CH3), 14.40 (CH3), 47.16 (CH2), 125.56
(CH), 126.50 (CH), 127.52 (2CH), 128.01 (2CH), 128.21 (2CH), 129.40
(2CH), 136.52 (quat C), 136.64 (quat C), 137.80 (quat C), 138.17 (quat
C), 138.31 (quat C), 143.96 ppm (quat C); HRMS: calcd for C19H19
[M+H]+: 247.1481; found: 247.1486.
1,2-Diethyl-3,4-diphenylcyclopentadiene (5a): Yellow oil; 90% yield after
isolation (493 mg); 1H NMR (400 MHz, CDCl3): d=0.78 (t, J=7.5 Hz,
3H, CH3), 1.18 (t, J=7.5 Hz, 3H, CH3), 2.19 (q, J=7.5 Hz, 2H, CH2),
2.46 (q, J=7.5 Hz, 2H, CH2), 3.40 (s, 2H, CH2), 7.99–7.54 ppm (m, 10H,
CH); 13C NMR (75 MHz, CDCl3): d=14.52 (CH3), 15.05 (CH3), 18.77
(CH2), 21.45 (CH2), 44.12 (CH2), 125.50 (CH), 126.71 (CH), 127.24
(2CH), 127.94 (2CH), 128.50 (2CH), 129.23 (2CH), 137.00 (quat C),
137.50 (quat C), 138.34 (quat C), 141.93 (quat C), 142.83 (quat C),
144.35 ppm (quat C); HRMS: calcd for C21H23 [M+H]+: 275.1794; found:
275.1799.
1,3-Dipropyl-2,4-diphenylcyclopentadiene (2 f): Yellow oil; 89% yield
(554 mg); 1H NMR (400 MHz, CDCl3): d=0.67 (t, J=7.2 Hz, 3H, CH3),
0.86 (t, J=7.2 Hz, 3H, CH3), 1.14–1.24 (m, 2H, CH2), 1.45–1.55 (m, 2H,
CH2), 2.28 (t, J=8.0 Hz, 2H, CH2), 2.38 (t, J=8.0 Hz, 2H, CH2), 3.37 (s,
2H, CH2), 7.18–7.40 ppm (m, 10H, CH); 13C NMR (100 MHz, CDCl3):
d=14.17 (CH3), 14.21 (CH3), 22.36 (CH2), 23.67 (CH2), 29.02 (CH2),
30.79 (CH2), 45.13 (CH2), 125.70 (CH), 126.47 (CH), 127.62 (2CH),
127.97 (2CH), 128.27 (2CH), 129.32 (2CH), 136.70 (quat C), 137.37
(quat C), 138.17 (quat C), 143.07 (quat C), 143.40 (quat C), 143.78 ppm
(quat C); HRMS: calcd for C23H27 [M+H]+: 303.2107; found: 303.2113.
1,2-Dipropyl-3,4-diphenylcyclopentadiene (5b): Yellow oil; 90% yield
after isolation (544 mg); 1H NMR (400 MHz, CDCl3): d=0.67 (t, J=
7.3 Hz, 3H, CH3), 0.86 (t, J=7.5 Hz, 3H, CH3), 1.14–1.24 (m, 2H, CH2),
1.45–1.55 (m, 2H, CH2), 2.28 (t, J=7.7 Hz, 2H, CH2), 2.38 (t, J=8.0 Hz,
2H, CH2), 3.37 (s, 2H, CH2), 7.18–7.40 ppm (m, 10H, CH); 13C NMR
(75 MHz, CDCl3): d=14.13 (CH3), 14.39 (CH3), 22.87 (CH2), 23.70
(CH2), 27.78 (CH2), 30.69 (CH2), 44.51 (CH2), 125.46 (CH), 126.66 (CH),
127.20 (2CH), 127.93 (2CH), 128.45 (2CH), 129.17 (2CH), 136.94 (quat
C), 137.35 (quat C), 138.36 (quat C), 141.02 (quat C), 141.73 (quat C),
144.41 ppm (quat C); HRMS: calcd for C23H27 [M+H]+: 303.2107; found:
303.2113.
1,3-Dibutyl-2,4-diphenylcyclopentadiene (2g): Yellow oil; 90% yield
(596 mg); 1H NMR (400 MHz, CDCl3): d=0.67 (t, J=7.2 Hz, 3H, CH3),
0.85 (t, J=7.2 Hz, 3H, CH3), 1.03–1.06 (m, 2H, CH2), 1.14–1.24 (m, 2H,
CH2), 1.45–1.67 (m, 4H, CH2), 2.27 (t, J=7.6 Hz, 2H, CH2), 2.38 (t, J=
7.6 Hz, 2H, CH2), 3.37 (s, 2H, CH), 7.18–7.40 ppm (m, 10H, CH);
13C NMR (75 MHz, CDCl3): d=13.56 (CH3), 13.96 (CH3), 22.55 (CH2),
22.61 (CH2), 26.39 (CH2), 28.34 (CH2), 31.02 (CH2), 32.70 (CH2), 45.00
(CH2), 125.60 (CH), 126.40 (CH), 127.50 (2CH), 127.89 (2CH), 128.20
(2CH), 129.25 (2CH), 136.38 (quat C), 137.21 (quat C), 138.02 (quat C),
143.10 (quat C), 143.47 (quat C), 143.56 ppm (quat C); HRMS: calcd for
C25H31 [M+H]+: 331.2420; found: 331.2424.
2-Methyl-1,3,4-triphenylcyclopentadiene (5c): Yellow solid; 91% yield
after isolation (560 mg); 1H NMR (400 MHz, CDCl3): d=1.98 (s, 3H,
CH3), 3.85 (d, J=1.4 Hz, 2H, CH2), 7.08–7.48 ppm (m, 15H, CH);
13C NMR (100 MHz, CDCl3): d=13.96 (CH3), 45.17 (CH2), 126.12
(2CH), 127.04 (CH), 127.47 (2CH), 127.73 (2CH), 128.10 (2CH), 128.38
(CH), 128.63 (2CH), 129.44 (2CH), 131.59 (CH), 136.49 (quat C), 137.48
(quat C), 137.54 (quat C), 138.69 (quat C), 139.36 (quat C), 139.48 (quat
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C), 145.56 ppm (quat C); HRMS: calcd for C24H21 [M+H]+: 309.1638;
found: 309.1633.
Bis(1,2,3,4-tetraethylcyclopentadienyl) zirconium dichloride (9a): White
solid; 85% yield after isolation (1.48 g); H NMR (300 MHz, CDCl3): d=
1
1.07–1.15 (m, 24H, CH3), 2.35–2.57 (m, 16H, CH2), 5.68 ppm (s, 2H,
CH); 13C NMR (75 MHz, CDCl3): d=15.26 (4CH3), 16.18 (4CH3), 20.23
(4CH2), 21.89 (4CH2), 107.14 (2CH), 129.13 (4 quat C), 132.84 ppm (4
quat C); elemental analysis: calcd (%) for C26H42Cl2Zr: C 60.43, H 8.19;
found: C 60.55, H 8.08.
1,2-Diethyl-3,4-tripropylcyclopentadiene (5d): Yellow oil; 85% yield after
isolation (350 mg); 1H NMR (300 MHz, CDCl3): d=0.89–1.10 (m, 12H,
CH3), 1.37–1.52 (m, 4H, CH2), 2.16–2.37 (m, 8H, CH2), 2.76 ppm (s, 2H,
CH2); 13C NMR (75 MHz, CDCl3): d=14.37 (CH3), 14.48 (CH3), 15.12
(2CH3), 18.76 (CH2), 21.23 (CH2), 23.78 (2CH2), 28.05 (CH2), 30.64
(CH2), 43.11 (CH2), 138.20 (quat C), 139.13 (quat C) 140.03 (quat C),
141.17 ppm (quat C); HRMS: calcd for C15H27 [M+H]+: 207.2107; found:
207.2110.
Bis(1,2,3,4-tetrapropylcyclopentadienyl) zirconium dichloride (9b): White
solid; 80% yield after isolation (2.0 g); 1H NMR (300 MHz, C4D8O): d=
0.93–1.02 (m, 24H, CH3), 1.41–1.54 (m, 16H, CH2), 2.19–2.43 (m, 16H,
CH2), 5.85 ppm (s, 2H, CH); 13C NMR (75 MHz, C4D8O): d=14.50
(4CH3), 15.24 (4CH3), 25.33 (4CH2), 26.09 (4CH2), 30.77 (4CH2), 31.60
(4CH2), 109.29 (2CH), 127.45 (4 quat C), 132.62 ppm (4 quat C); ele-
mental analysis: calcd (%) for C34H58Cl2Zr: C 64.93, H 9.29; found: C
64.81, H 9.18.
One-pot synthesis of substituted indene derivatives from one alkyne and
one CH2I2: A typical procedure for the preparation of 2,3-diethyl-1H-
indene (7a): PhLi (2.0 mmol, 2.0m, 2.0 mL) was added dropwise with a
syringe to a toluene (10 mL) solution of [Cp2ZrCl2] (2.0 mmol, 584 mg)
at À788C (dry ice/acetone) in a 20 mL Schlenk tube. After the addition
was complete, the reaction mixture was stirred at 258C for 2 h. 3-Hexyne
(2.0 mmol, 164 mg) was added, and the reaction mixture was warmed to
1108C and stirred at this temperature for 9 h. The mixture was cooled to
room temperature, and the solvent was changed to THF. This solution
was cooled to À788C, and CuCl (396 mg, 4.0 mmol), DMPU (768 mg,
6.0 mmol), and CH2I2 (1.072 g, 4.0 mmol) were added. The solution was
heated to 708C and kept at this temperature for 1 h. The reaction mix-
ture was then cooled to room temperature and quenched with saturated
aqueous NaHCO3. The resulting mixture was extracted with diethyl ether
three times, then washed with water and brine. The extract was dried
over anhydrous MgSO4. The solvent was evaporated in vacuo to give a
yellow oil, which was subjected to a SiO2 chromatography column with
hexane as the eluent.
A
typical procedure for dimethylzirconocene complex 10: MeLi
(1.0 mmol, 1.0m, 1.0 mL) was added with a syringe to a THF (10 mL) sol-
ution of 9b (0.5 mmol, 313 mg) at room temperature in a 20 mL Schlenk
tube. After the addition was complete, the reaction mixture was stirred
at room temperature for 12 h, and the solvent was removed under
vacuum. The residue was extracted with hexane, and the LiCl salt was re-
moved by filtration. The filtrate was dried out under vacuum to give
product 10 as a white solid. Similarly, diethylzirconocene 11 and dibutyl-
zirconocene 12 were prepared from EtLi and nBuLi, respectively.
Dimethyl bis(1,2,3,4-tetrapropylcyclopentadienyl) zirconium (10): White
solid; 91% yield after isolation (267 mg); 1H NMR (300 MHz, C4D8O):
d=À0.94 (s, 6H, CH3), 0.94 (t, J=7.2 Hz, 12H, CH3), 1.02 (t, J=7.2 Hz,
12H, CH3), 1.40–1.60 (m, 16H, CH2), 1.89–1.99 (m, 4H, CH2), 2.20–2.38
(m, 12H, CH2), 5.00 ppm (s, 2H, CH); 13C NMR (75 MHz, C4D8O): d=
14.66 (4CH3), 15.33 (4CH3), 26.02 (4CH2), 26.16 (4CH2), 30.54 (4CH2),
31.02 (4CH2), 35.23 (2CH3), 104.55 (2CH), 122.59 (4 quat C),
125.09 ppm (4 quat C); elemental analysis: calcd (%) for C36H64Zr: C
73.52, H 10.97; found: C 73.37, H 10.77.
2,3-Diethyl-1H-indene (7a): Yellow oil; 90% yield after isolation
(310 mg); the NMR spectra are consistent with the reported data.[5h]
2,3-Dipropyl-1H-indene (7b): Yellow oil; 91% yield after isolation
(362 mg); the NMR spectra are consistent with the reported data.[5h]
2,3-Diphenyl-1H-indene (7c): Yellow solid; 91% yield after isolation
Diethyl bis(1,2,3,4-tetrapropylcyclopentadienyl) zirconium (11): Yellow
solid; 86% yield after isolation (106 mg, 0.2 mmol scale); 1H NMR
(400 MHz, C6D6): d=0.87–1.00 (m, 30H, CH3), 1.54–1.62 (m, 20H, CH2),
2.07–2.14 (m, 2H, CH2), 2.18–2.23 (m, 2H, CH2), 2.37–2.50 (m, 4H,
CH2), 2.60–2.78 (m, 8H, CH2), 5.51 ppm (s, 2H, CH); 13C NMR
(100 MHz, C6D6): d=14.34 (4CH3), 15.10 (4CH3), 18.60 (2CH3), 25.26
(4CH2), 25.79 (4CH2), 29.58 (4CH2), 30.55 (4CH2), 46.56 (2CH2), 107.08
(2CH), 123.43 (4 quat C), 124.24 ppm (4 quat C).
(488 mg); the NMR spectra are consistent with the reported data.[5h]
Synthesis of tetrasubstituted cyclopentadienyl lithium: A typical proce-
dure for the preparation of 1,2,3,4-tetraethylcyclopentadienyl lithium (8a):
nBuLi (10.0 mmol, 1.6m, 6.25 mL) was added dropwise with a syringe to
a THF (20 mL) solution of 2c (10.0 mmol, 1.78 g) at À788C (dry ice/ace-
tone) in a 50 mL Schlenk tube. After the addition was complete, the re-
action mixture was stirred at À788C for 1 h, then warmed to 258C and
stirred at this temperature for 3 h. THF was removed under vacuum, and
hexane was added. The produced lithium salt was isolated by filtration to
give 8a as a white precipitate.
Dibutyl bis(1,2,3,4-tetrapropylcyclopentadienyl) zirconium (12): Yellow
oil; NMR yield: 76%; 1H NMR (400 MHz, C4D8O): d=1.05–1.13 (m,
30H, CH3), 1.41–1.63 (m, 24H, CH2), 2.10–2.52 (m, 20H, CH2), 5.60 ppm
(s, 2H, CH); 13C NMR (100 MHz, C4D8O): d=14.10 (2CH3), 14.45
(4CH3), 15.20 (4CH3), 25.11 (2CH3), 26.38 (4CH2), 29.99 (2CH2), 30.76
(4CH2), 31.59 (4CH2), 36.54 (2CH2), 54.44 (2CH2), 107.75 (2CH), 123.98
(4 quat C), 128.47 ppm (4 quat C).
1,2,3,4-Tetraethylcyclopentadienyl lithium (8a): White solid; 80% yield
after isolation (1.47 g); 1H NMR (400 MHz, C4D8O): d=0.85 (t, J=
7.4 Hz, 6H, CH3), 0.97 (t, J=7.4 Hz, 6H, CH3), 2.14–2.24 (m, 8H, CH2),
4.86 ppm (s, 1H, CH); 13C NMR (100 MHz, C4D8O): d=16.72 (2CH3),
18.45 (2CH3), 19.65 (2CH2), 21.24 (2CH2), 96.71 (CH), 114.14 (2 quat
C), 114.49 ppm (2 quat C); elemental analysis: calcd (%) for C13H21Li: C
84.74, H 11.49; found: C 84.59, H 11.62.
X-ray crystallographic studies: Single crystals of 9a, 9b, and 10 suitable
for X-ray analysis were grown. The crystals were manipulated under a ni-
trogen atmosphere and were sealed in a thin-walled glass capillary. Data
collections were performed at 258C on a Rigaku Raxis Rapid IP diffrac-
tometer by using graphite-monochromated Mo Ka radiation (l=
0.71073 ꢁ). The determination of crystal class and unit cell parameters
was carried out with the Rapid-Auto (Rigaku 2000) program package.
The raw frame data were processed by using the Crystal Structure
(Rigaku/MSC 2000) software to yield the reflection data file. The struc-
tures were solved by use of the SHELXTL program.[19] Refinement was
performed on F2 anisotropically for all non-hydrogen atoms by the full-
matrix least-squares method. The hydrogen atoms were placed at the cal-
culated positions and were included in the structure calculation without
further refinement of the parameters. Crystal data, data collection, and
processing parameters for compounds 9a, 9b and 10 are summarized in
the Supporting Information. CCDC 921086 (9a), 921085 (9b), and
921084 (10) contain the supplementary crystallographic data (excluding
structure factors) for this paper. These data can be obtained free of
charge from the Cambridge Crystallographic Data Centre via
www.ccdc.cam.ac.uk/data_request/cif.
1,2,3,4-Tetrapropylcyclopentadienyl lithium (8b): White solid; 80% yield
after isolation (1.93 g); 1H NMR (300 MHz, C4D8O): d=0.87–0.93 (m,
12H, CH3), 1.31–1.55 (m, 8H, CH2), 2.30–2.36 (m, 8H, CH2), 5.17 ppm
(s, 1H, CH); 13C NMR (75 MHz, C4D8O): d=15.11 (2CH3), 15.14
(2CH3), 26.28 (2CH2), 27.75 (2CH2), 30.05 (2CH2), 31.66 (2CH2), 98.71
(CH), 113.39 (2 quat C), 113.79 ppm (2 quat C); elemental analysis:
calcd (%) for C17H29Li: C 84.95, H 12.16; found: C 84.77, H 12.31.
Synthesis of tetrasubstituted zirconocene complexes: A typical procedure
for the preparation of bis(1,2,3,4-tetraethylcyclopentadienyl) zirconium di-
chloride (9a): ZrCl4 (4.0 mmol, 924 mg) was added to a toluene (20 mL)
solution of 8a (8.0 mmol, 1.47 g) at room temperature in
a 50 mL
Schlenk tube under an N2 atmosphere. After the addition was complete,
the reaction mixture was stirred at room temperature for 12 h, then
warmed to 608C and stirred at this temperature for 12 h. The LiCl salt
was removed by filtration, and the filtrate was dried out under vacuum
to give product 9a as a white solid.
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1,2,3,4-Tetrasubstituted Cyclopentadienes and the Corresponding Metallocenes
FULL PAPER
f) W.-X. Zhang, M. Nishiura, Z. Hou, Chem. Eur. J. 2007, 13, 4037–
4051.
Acknowledgements
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Received: February 2, 2013
Revised: March 27, 2013
Published online: && &&, 0000
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These are not the final page numbers!

1,2,3,4-Tetrasubstituted Cyclopentadienes and the Corresponding Metallocenes
FULL PAPER
Synthetic Methods
W. Geng, C. Wang, J. Guang, W. Hao,
W.-X. Zhang, Z. Xi* ......... &&&& — &&&&
1,2,3,4-Tetrasubstituted Cyclopenta-
dienes and Their Applications for
Metallocenes: Efficient Synthesis
through Zirconocene- and CuCl-Medi-
ated Intermolecular Coupling of Two
Alkynes and One Diiodomethane
Ringing in the changes: A one-pot syn-
thesis of 1,2,3,4-tetrasubstituted cyclo-
pentadienes by zirconocene- and
CuCl-mediated intermolecular cou-
pling of two alkynes and diiodome-
thane (see scheme; Cp=h5-C5H5;
DMPU=1,3-dimethyl-3,4,5,6-tetrahy-
dro-2(1H)-pyrimidinone) gave prod-
ucts that were successfully applied for
the synthesis of corresponding zircono-
cene derivatives.
AHCTUNGTRENNUNG
Chem. Eur. J. 2013, 00, 0 – 0
ꢀ 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
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These are not the final page numbers!