Zirconocene-mediated intermolecular coupling of Si-tethered diynes with alkynes, ketones, aldehydes, and isocyanates by means of novel skeletal rearrangement of zirconacyclobutene-silacyclobutene and zirconacyclohexadiene- silacyclobutene fused-ring intermediates

Article abstract of DOI:10.1002/chem.200400697

Bis(alkynyl)silanes react with low valent zirconocene species to afford zirconacyclobutene intermediates. These in situ generated reactive organometallic intermediates can react with alkynes, ketones, aldehydes, and isocyanates by means of a novel skeletal rearrangement. When a zirconacyclobutene intermediate was treated with an alkyne, an α-alkynylsilyl zirconacyclopentadiene was formed. Addition of dimethyl acetylenedicarboxylate (DMAD) and CuCl resulted in one-pot formation of an alkynylsilyl-benzene derivative from three different alkynes. At a higher temperature, the α-alkynyl-silylzirconacyclopentadiene was transformed by means of an intramolecular skeletal rearrangement to a zirconacyclohexadiene- silacyclobutene fused-ring compound, which reacted with DMAD in the presence of CuCl affording the same alkynylsilyl-benzene derivative. When treated with a ketone, an aldehdye, or an isocyanate, the zirconocyclobutene intermediate also underwent the above-mentioned skeletal rearrangement, generating zirconocene-mediated cross-coupling products.

Full text of DOI:10.1002/chem.200400697

FULL PAPER
Zirconocene-Mediated Intermolecular Coupling of Si-tethered Diynes with
Alkynes, Ketones, Aldehydes, and Isocyanates by means of Novel Skeletal
Rearrangement of Zirconacyclobutene–Silacyclobutene and
Zirconacyclohexadiene–Silacyclobutene Fused-Ring Intermediates
Tao Yu,[a] Xiaohua Sun,[b] Congyang Wang,[a] Liang Deng,[a] and Zhenfeng Xi*[a, c]
Abstract: Bis(alkynyl)silanes react with
low valent zirconocene species to
afford zirconacyclobutene intermedi-
ates. These in situ generated reactive
organometallic intermediates can react
with alkynes, ketones, aldehydes, and
isocyanates by means of a novel skele-
tal rearrangement. When a zirconacy-
clobutene intermediate was treated
with an alkyne, an a-alkynylsilyl zirco-
nacyclopentadiene was formed. Addi-
tion of dimethyl acetylenedicarboxylate
(DMAD) and CuCl resulted in one-pot
formation of an alkynylsilyl–benzene
derivative from three different alkynes.
At a higher temperature, the a-alkynyl-
silylzirconacyclopentadiene was trans-
formed by means of an intramolecular
skeletal rearrangement to a zirconacy-
ring compound, which reacted with
DMAD in the presence of CuCl af-
fording the same alkynylsilyl–benzene
derivative. When treated with
a
ketone, an aldehdye, or an isocyanate,
the zirconocyclobutene intermediate
also underwent the above-mentioned
skeletal rearrangement, generating zir-
clohexadiene–silacyclobutene
fused-
conocene-mediated
products.
cross-coupling
Keywords: cross-coupling
·
rear-
rangement · silanes · zirconium
Introduction
on preparation and reaction of four- and six-membered met-
allacyclic intermediates.[4–8] Thus, development of synthetic
methods for four- and six-membered metallacycles and in-
vestigation into their reaction chemistry and applications in
organic synthesis are demanding.
The chemistry of metallacyclic compounds has attracted
much attention because many synthetically important transi-
tion-metal-assisted reactions proceed via metallacyclic inter-
mediates.[1] Compared with a large number of reports on
five-membered metallacycles,[2,3] there are not many reports
Several years ago,[9] Takahashi and co-workers reported
an interesting zirconocene-mediated reaction of bis(alky-
nyl)silanes. As illustrated in Scheme 1, treatment of bis(al-
[a] T. Yu, C. Wang, L. Deng, Prof. Dr. Z. Xi
Key Laboratory of Bioorganic Chemistry and
Molecular Engineering of Ministry of Education
College of Chemistry, Peking University, Beijing 100871 (China)
Fax : (+86)10-627-51708
E-mail: zfxi@pku.edu.cn
[b] X. Sun
Institute of Chemistry, Chinese Academy of Sciences
Beijing 100080 (China)
[c] Prof. Dr. Z. Xi
State Key Laboratory of Organometallic Chemistry
Shanghai Institute of Organic Chemistry
Chinese Academy of Sciences, Shanghai 200032 (China)
Supporting information for this article is available on the WWW
1
under http://www.chemeurj.org/ or from the author. Copies of H and
13C NMR spectra for new compounds and X-ray crystallography data
for 14b and 17a.
Scheme 1. Zirconocene-mediated skeleton rearrangement of bis(alkynyl)-
silanes affording four- and six-membered zirconacycles.
Chem. Eur. J. 2005, 11, 1895 – 1902
DOI: 10.1002/chem.200400697
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1895

kynyl)silanes 1 with low valent zirconocene species afforded
four-membered zirconacyclobutene derivatives 2, while re-
action of 1 with zirconacyclopentenes 3 firstly resulted in
the formation of zirconacyclopentadienes 4, which subse-
quently transformed to six-membered zirconacyclohexa-
diene derivatives 5. Both reactions proceeded by means of a
novel intramolecular skeleton rearrangement. As we are in-
terested in synthesis and applications of metallacycles, we
have investigated the reaction chemistry of zirconacyclobu-
tene derivatives 2. Recently, we reported that reaction of 2
with three equivalents of organonitriles affords pyrro-
lo[3,2c]pyridine derivatives after hydrolysis.[10] Cleavage of
one of the three CꢀN triple bonds was observed. In this
paper, we report reactions and synthetic applications of zir-
conacyclobutene derivatives 2 with alkynes, ketones, alde-
hydes, and isocyanates.[11] Novel skeletal rearrangement of 2
took place in these reactions.
Formation of isomeric products 6 was not observed. Howev-
er, surprisingly, experimental results demonstrated that
products 5 were not formed through the expected insertion
À
reaction path, but through a novel cleavage of a C C bond
À
in the zirconacyclobutene skeleton and a C Si bond in the
silacyclobutene skeleton (Scheme 2).
As illustrated in Scheme 2, after addition of one equiva-
lent of 5-decyne to a solution of 2 in THF, the reaction mix-
ture was warmed to 508C and stirred at this temperature for
1 h. Hydrolysis of the reaction mixture with 3% aqueous
HCl afforded 7a in 71% isolated yield (72% GC yield),
along with <3% yield of 8a. With longer reaction times
and higher temperature, the concentration of 7a decreased
while that of 8a increased. Finally, on prolonged heating at
reflux, 7a disappeared completely and 8a was formed as the
sole product in 80% isolated yield (90% GC yield). In simi-
lar fashions, products 7b and 8b were obtained in high
yields. Deuteriolysis of the reaction mixtures instead of hy-
drolysis afforded the deuterated products [D2]-7b and [D2]-
8b in 77% and 70% isolated yields, respectively, with more
than 98% of deuterium incorporation. When an unsymmet-
rical alkyne such as 1-phenyl-1-butyne was used, both 7c
and 8c were formed in excellent isolated yields with perfect
regioselectivity. The phenyl substituent was always located
at the terminal position. Interestingly, in case of 1-trimethyl-
silyl-1-propyne, only compound 7d was formed with perfect
regioselectivity, and product 8d was not be formed even
after a prolonged reaction time, probably due to the bulki-
ness of SiMe3 group.
Results and Discussion
Alkyne-induced skeleton rearrangement of zirconacyclobu-
tene derivatives 2 leading to the formation of six-membered
zirconacyclohexadiene derivatives 5 via five-membered zir-
conacyclopentadienes 4: The four-membered zirconacyclo-
butene derivatives 2 can be easily prepared by following Ta-
kahashiꢁs procedure.[9] Insertion reaction of an alkyne into
À
one of the Zr C bonds of 2 was expected to generate the
six-membered zirconacycles 5 (Scheme 2). The reaction did
proceed, affording 5 highly selectively in excellent yields.
The above results indicate that intermediate 4 is kinetical-
ly favored, whilst intermediate 5 is thermodynamically fa-
vored.
It is still not clear how the zirconacyclobutene derivative
2 undergoes skeleton rearrangement in the presence of al-
kynes to finally afford zirconacyclopentadienes 4. For the
formation of 5 from 4, Takahashi and co-workers have pro-
posed a reaction path.[9] For the formation of 4 from the re-
action of an alkyne with 2, we assume that two pathways
might be considered. One is the associative path (Scheme 3,
path a), the other is
a disassociative path (Scheme 3,
path b). In path a, coordination of the alkyne onto the zirco-
nium atom is assumed to be critical for inducing cleavage of
À
À
the C C bond and Si C bond in 2.
One-pot formation of alkynylsilyl–benzene derivatives from
three molecules of alkynes including one Si-tethered diyne:
Transition-metal-mediated selective aromatization of al-
kynes has attracted much attention.[1,12] The strategy of cou-
pling a tethered diyne with a monoyne has been successfully
applied to achieve preparation of bicyclic aromatic com-
pounds from these three triple bonds [Eq. (1) in
Scheme 4].[13] In recent years, one-pot construction of ben-
zene derivatives from three different monoynes has also
been developed [Eq. (2) in Scheme 4].[14–17] In this work, we
found that three triple bonds out of four [shown in Eq. (3)
in Scheme 4] could be highly selectively integrated into a
benzene derivative; one of the triple bonds in bis(alkynyl)si-
Scheme 2. Reaction of alkynes with 2 by means of skeleton rearrange-
ment.
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Zirconium Chemistry
FULL PAPER
Scheme 5. Reactions of 4 and 5 with DMAD in the presence of CuCl.
Scheme 3. Proposed reaction mechanisms from 2 to 4.
À
Figure 1. X-ray structure of 14b. Selected bond lengths [ꢂ]: C1 C2 1.425
À
À
À
À
(3), C2 C3 1.399 (3), C3 C4 1.381 (3), C4 C5 1.409 (3), C5 C6 1.409
À
À
Scheme 4. Types of one-pot aromatization of alkynes.
(3), C1 C6 1.400 (3), C25 C26 1.197 (3).
lanes 1 remains unreacted as a functional group attached to
the products.
Interestingly, the in situ generated zirconacyclohexa-
diene–silacyclobutene fused-ring compounds 5 reacted with
DMAD in the presence of CuCl to give the same alkynylsil-
yl–benzene derivatives 14.
The reaction mechanism for CuCl-mediated formation of
benzene derivatives from zirconacyclopentadienes and
DMAD has been previously discussed in the literature.[16]
However, formation of benzene derivatives 14 from the six-
membered zirconacycles 5 is not clear yet. A novel skeletal
rearrangement must be involved in this CuCl-mediated ben-
zene formation reaction.
Takahashi and co-workers have reported the CuCl-medi-
ated formation of benzene derivatives from reaction of zir-
conacyclopentadienes with dimethyl acetylenedicarboxylate
(DMAD).[2,14,16] In our work, treatment of zirconacyclopen-
tadiene derivatives 4, generated in situ from bis(alkynyl)si-
lane 1 and monoalkynes via zirconacyclobutene intermedi-
ates 2, with one equivalent of DMAD in the presence of
CuCl afforded benzene derivatives 14 in high isolated yields
(Scheme 5). The structure of 14b has been determined by
single-crystal X-ray structural analysis (Figure 1).[18] These
benzene derivatives are formed chemo- and regioselectively
from three different alkynes.
Reactions of ketones, aldehydes, and isocyanates with zirco-
nacyclobutene derivatives 2 affording allylic alcohols and
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Z. Xi et al.
unsaturated amides: In addition to alkynes, ketones, alde-
hydes, and isocyanates were also found to be able to induce
When 2 was treated with isocyanates, alkynylsilyl amides
were obtained in good yields upon hydrolysis or halogena-
tion of the reaction mixtures with I2 or NBS (Scheme 7).
Table 2 shows the results obtained. The structure of 17a has
been determined by single-crystal X-ray structural analysis
(Figure 2).[21] Proposed reaction intermediates are given in
Scheme 8.[22]
À
À
the novel cleavage of C C and C Si bond (Scheme 6). Five-
Scheme 6. Reactions of 2 with ketones and aldehydes affording alkynyl-
silyl-substituted allylic alcohols.
membered oxazirconacyclopentenes 15[19,20] are proposed to
be formed as the organometallic intermediates, probably by
similar reaction paths shown in Scheme 3. Allylic alcohols
16 were isolated in good yields after hydrolysis of the reac-
tion mixtures (Scheme 6). The results are listed in Table 1.
Scheme 7. Reaction of 2 with isocyanates.
Table 2. Isolation of alkynylsilyl amides from zirconocene-mediated in-
termolecular coupling reaction of a Si-tethered diyne with an isocya-
nate.[a]
RNCO
Products
17 and 18
Yield [%][b]
Table 1. Zirconocene-mediated intermolecular coupling of a Si-tethered
diyne with a ketone or an aldehyde by means of novel skeletal rearrange-
ment of zirconacyclobutene–silacyclobutene fused-ring intermediates af-
fording allylic alcohols after hydrolysis.[a]
Entry
Ketone or aldehyde
RR’CO
Product 16
Yield [%][b]
17a
17b
17c
17d
62
1
2
16a
16b
(75)
(65)
55
43
64
3
4
5
6
16c
16d
16e
16 f
(80)
86 (82)
83 (63)
72 (63)
7
16g
71 (69)
18a: X=I
18b: X=Br
53
67
8
16h
16i
16j
81 (81)
93 (79)
(79)
9
18c: X=I
18d: X=Br
60
55
10
[a] Reaction conditions are given in Scheme 6. [b] GC yields. Isolated
yields are given in parentheses.
[a] Reaction conditions are given in Scheme 7. [b] Isolated yields.
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Zirconium Chemistry
FULL PAPER
dichloride was obtained from Nichia
Co. THF was refluxed and distilled
from sodium benzophenone ketyl
under a nitrogen atmosphere.
1H and 13C NMR spectra were record-
ed on a JEOL-300 MHz spectrometer.
GLC analysis was performed on a gas
chromatograph (Shimadzu 14B) equip-
ped with a flame ionization detector
using a capillary column (CBP1M25–
25). GLC yields were determined by
using suitable hydrocarbons as internal
standards.
General procedure for the reaction of
compounds 2 with alkynes leading to
alkynylsilyl butadienes (7a–d): nBuLi
(2.1 mmol, 1.6m, 1.32 mL) was added
dropwise with a syringe to a solution
of Cp2ZrCl2 (1.05 mmol, 307 mg) in
À
À
À
Figure 2. X-ray structure of 17a. Selected bond lengths [ꢂ]: C1 C2 1.186 (4), C9 C10 1.329 (3), C10 C17
À
À
1.502 (3), C17 O 1.228 (3), C17 N 1.353 (3).
THF (10 mL) at À788C (dry ice/ace-
tone) in a 20 mL Schlenk tube. After
the addition was complete, the reac-
tion mixture was stirred at À788C for 1 h. Then 1 mmol of bis(phenyl-
ethynyl)dimethylsilane (1) was added, and the reaction mixture was
warmed up to 508C and stirred at this temperature for 3 h. After an
alkyne (1.0 mmol) was added, the reaction mixture was stirred at this
temperature for 1 h. The reaction mixture was quenched with aqueous
HCl (1n), extracted with diethyl ether, then washed with saturated aque-
ous NaHCO3, water, and brine. The extract was dried over anhydrous
MgSO4. The solvent was evaporated in vacuo to give the crude product,
which was further purified by column chromatography.
Alkynylsilyl butadiene 7a: Colorless liquid, GC yield 72%, isolated yield
71% (284 mg); 1H NMR (CDCl3, TMS): d=À0.07 (s, 6H), 0.87 (t, J=
6.9 Hz, 3H), 0.94 (t, J=6.9 Hz, 3H), 1.26–1.60 (m, 8H), 2.07 (t, J=
7.2 Hz, 2H), 2.32 (t, J=7.2 Hz, 2H), 5.21 (t, J=7.5 Hz, 1H), 5.85 (s, 1H),
7.17–7.45 ppm (m, 10H); 13C NMR (CDCl3, TMS): d=À0.17, 13.95,
14.03, 22.47, 22.85, 27.39, 28.55, 31.23, 31.76, 94.47, 105.01, 122.17, 123.43,
126.98, 127.51, 128.11, 128.30, 129.77, 131.92, 134.12, 142.46, 142.85,
160.45 ppm; HRMS: m/z calcd for C28H36Si: 400.2586; found: 400.2600.
Scheme 8. Proposed reaction intermediates in the reaction of 2 with iso-
cyanates.
Conclusion
Alkynylsilyl butadiene 7b: Colorless liquid, isolated yield 75% (279 mg);
1H NMR (CDCl3, TMS): d=À0.14 (s, 6H), 0.77 (t, J=7.5 Hz, 3H), 0.88
(t, J=7.2 Hz, 3H), 1.18–1.28 (m, 2H), 1.37–1.49 (m, 2H), 1.99 (q, J=
7.2 Hz, 2H), 2.24 (t, J=7.2 Hz, 2H), 5.16 (t, J=7.5 Hz, 1H), 5.78 (s, 1H),
7.10–7.38 ppm (m, 10H); 13C NMR (CDCl3, TMS): d=À0.17, 12.89,
13.21, 21.16, 21.73, 28.68, 29.88, 93.45, 103.99, 121.19, 122.39, 125.97,
126.52, 127.10, 127.30, 128.75, 130.92, 133.19, 141.44, 141.78, 159.43 ppm;
HRMS: m/z calcd for C26H32Si: 372.2273; found: 372.2266.
Investigation into the reaction chemistry of isolable reactive
organometallic intermediates and applications of these inter-
mediates in organic synthesis have been of great interest. In
this work, we have studied on the reaction chemistry of zir-
conacyclobutene–silacyclobutene and zirconacyclohexa-
diene–silacyclobutene fused-ring compounds. Novel skeletal
rearrangements, though their mechanisms are not clear yet,
take place in all the reactions involving the zirconacyclobu-
tene and zirconacyclohexadiene derivatives. Through novel
skeletal rearrangement mechanisms, several synthetically
useful methods have been developed, including selective
cross-coupling of bis(alkynyl)silanes with monoynes, alde-
hydes, ketones, and isocyanates, and a new one-pot proce-
dure for the formation of alkynylsilyl–benzene derivatives
from four CꢀC triple bonds.
Alkynylsilyl butadiene [D2]-7b: Obtained when the reaction mixture was
quenched with DCl/D2O instead of 1n aqueous HCl. Colorless liquid,
isolated yield 77% (288 mg); 1H NMR (CDCl3, TMS): d=À0.07 (s, 6H),
0.84 (t, J=7.2 Hz, 3H), 0.95 (t, J=7.5 Hz, 3H), 1.10–1.65 (m, 4H), 2.05
(t, J=7.5 Hz, 2H), 2.31 (t, J=7.5 Hz, 2H), 6.96–7.65 ppm (m, 10H);
13C NMR (CDCl3, TMS): d=À0.15, 13.89, 14.22, 22.17, 22.72, 29.67,
30.78, 94.46, 105.03, 121.84 (t, J=21 Hz), 123.43, 126.99, 127.53, 128.11,
128.30, 129.26, 131.92, 133.79 (t, J=21 Hz), 142.46, 142.70, 160.40 ppm;
HRMS: m/z calcd for C26H30D2Si: 374.2402; found: 374.2399.
Alkynylsilyl butadiene 7c: Colorless liquid, GC yield 84%, isolated yield
77% (302 mg); 1H NMR (CDCl3, TMS): d=À0.20 (s, 6H), 1.00 (t, J=
7.5 Hz, 3H), 2.35 (q, J=7.5 Hz, 2H), 5.91 (s, 1H), 6.10 (s, 1H), 6.99–
7.27 ppm (m, 15H); 13C NMR (CDCl3, TMS): d=À0.19, 13.98, 21.29,
94.08, 105.27, 125.03, 126.60, 127.31, 127.75, 127.91, 128.08, 128.12, 128.38,
128.68, 129.78, 131.56, 131.92, 138.13, 141.93, 146.71, 159.91 ppm; HRMS:
m/z calcd for C28H28Si: 392.1960; found: 392.1957.
Experimental Section
Alkynylsilyl butadiene 7d: Colorless liquid, GC yield 81%, isolated yield
77% (288 mg); 1H NMR (CDCl3, TMS): d=À0.07 (s, 6H), 0.08 (s, 9H),
2.08 (s, 3H), 5.34 (s, 1H), 6.01 (s, 1H), 7.16–7.44 ppm (m, 10H);
13C NMR (CDCl3, TMS): d=À0.33, À0.05, 19.77, 94.04, 105.24, 124.41,
126.36, 127.09, 127.56, 128.13, 128.38, 129.86, 131.95, 132.94, 141.85,
General: Unless otherwise noted, all starting materials were commercial-
ly available and were used without further purification. All reactions in-
volving organometallic compounds were run under a slightly positive
pressure of dry N2 with use of standard Schlenk techniques. Zirconocene
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Z. Xi et al.
153.20, 161.88 ppm; HRMS: m/z calcd for C24H30Si2: 374.1886; found:
374.1877.
(CDCl3): d=1.83, 14.63, 14.92, 24.07, 24.87, 32.15, 33.43, 52.11, 52.37,
93.83, 105.24, 123.27, 127.86, 127.93, 128.12, 128.36, 130.71, 131.94, 133.27,
133.58, 136.36, 139.70, 141.66, 142.00, 150.51, 169.73, 170.11 ppm; HRMS:
m/z calcd for C32H36O4Si: 512.2383; found: 512.2367.
General procedure for the reaction compounds 2 with alkynes leading to
alkylidene silacyclobutenes (8a–c): After an alkyne (1.0 mmol) was
added to 2, the reaction mixture was stirred at reflux for 6 h. The reac-
tion mixture was quenched with aqueous HCl (1n), extracted with dieth-
yl ether, then washed with saturated aqueous NaHCO3, water, and brine.
The extract was dried over anhydrous MgSO4. The solvent was evaporat-
ed in vacuo to give the crude product, which was further purified by
column chromatography.
Alkynylsilyl–benzene 14b: Colorless solid, isolated yield 69% (367 mg)
from 4, isolated yield 75% from 5; 1H NMR (CDCl3, TMS): d=0.02 (s,
6H), 0.53 (t, J=7.2 Hz, 3H), 2.29–2.36 (q, J=7.2 Hz, 2H), 3.43 (s, 3H),
3.80 (s, 3H), 7.26–7.47 ppm (m, 15H); 13C NMR (CDCl3): d=1.74, 14.46,
23.78, 51.98, 52.23, 93.52, 105.38, 123.10, 127.46, 127.77, 127.97, 128.02,
128.11, 128.39, 129.36, 130.74, 131.90, 134.12, 135.22, 135.69, 138.30,
140.81, 141.09, 143.10, 150.29, 169.27, 169.45 ppm; HRMS: m/z calcd for
C34H32O4Si: 532.2070; found: 532.2033.
Alkylidene silacyclobutene 8a: Colorless liquid, GC yield 90%, isolated
yield 80% (320 mg); 1H NMR (CDCl3, TMS): d=0.49 (s, 6H), 0.83 (t,
J=6.6 Hz, 3H), 0.99 (t, J=6.9 Hz, 3H), 1.26–1.52 (m, 8H), 2.12 (t, J=
7.5 Hz, 2H), 2.26 (t, J=6.9 Hz, 2H), 5.46 (t, J=7.5 Hz, 1H), 7.19–7.36
(m, 10H), 7.88 ppm (s, 1H); 13C NMR (CDCl3, TMS): d=À0.58, 13.96,
14.03, 22.55, 22.61, 27.76, 29.57, 30.60, 32.26, 126.53, 126.67, 126.86,
127.34, 128.00, 128.54, 131.84, 137.66, 138.63, 142.14, 142.89, 143.36,
148.55, 156.99 ppm; HRMS: m/z calcd for C28H36Si: 400.2586; found:
400.2594.
Alkynylsilyl–benzene 14c: Colorless solid, isolated yield 53% (273 mg)
from 4; 1H NMR (CDCl3, TMS): d=À0.04 (s, 6H), 0.34 (s, 9H), 2.14 (s,
3H), 3.79 (s, 3H), 3.87 (s, 3H), 7.14–7.45 ppm (m, 10H); 13C NMR
(CDCl3): d=1.71, 1.75, 23.02, 52.19, 52.41, 93.32, 105.51, 123.15, 127.77,
128.12, 128.35, 128.39, 130.22, 131.88, 135.10, 135.55, 137.95, 138.45,
141.99, 144.45, 149.77, 169.83, 170.67 ppm; HRMS: m/z calcd for
C30H34O4Si2: 514.1996 found 514.1963.
General procedure for the reaction of compounds 2 with ketones and al-
dehydes leading to alkynylsilyl allylic alcohols (16a–j): After a ketone or
an aldehyde (1.0 mmol) was added to 2, the reaction mixture was stirred
at 508C for 3 h. The reaction mixture was quenched with aqueous HCl
(1n), extracted with diethyl ether, and then washed with saturated aque-
ous NaHCO3, water and brine. The extract was dried over anhydrous
MgSO4. The solvent was evaporated in vacuo to give the crude product,
which was further purified by column chromatography.
Alkylidene silacyclobutene 8b: Colorless liquid, isolated yield 66%
(246 mg); 1H NMR (CDCl3, TMS): d=0.42 (s, 6H), 0.76 (t, J=7.2 Hz,
3H), 0.95 (t, J=7.5 Hz, 3H), 1.19–1.27 (m, 2H), 1.42–1.49 (m, 2H), 2.02
(t, J=6.9 Hz, 2H), 2.17 (q, J=7.5 Hz, 2H), 5.39 (t, J=7.2 Hz, 1H), 7.14–
7.28 (m, 10H), 7.80 ppm (s, 1H); 13C NMR (CDCl3, TMS): d=À1.55,
13.09, 13.14, 20.65, 22.25, 29.23, 30.98, 125.55, 125.69, 125.87, 126.37,
127.03, 127.56, 130.90, 136.65, 137.66, 141.14, 141.95, 142.33, 147.60,
156.00 ppm; HRMS: m/z calcd for C26H32Si: 372.2273; found: 372.2275.
Alkynylsilyl allylic alcohol 16a: Colorless liquid, isolated yield 75%
(270 mg); 1H NMR (CDCl3, TMS): d=À0.11 (s, 6H), 1.44–1.63 (m, 4H),
1.83–2.04 (m, 4H), 2.32–2.38 (m, 2H), 5.41–5.46 (br, 1H), 6.12 (s, 1H),
7.16–7.44 ppm (m, 10H); 13C NMR (CDCl3, TMS): d=À0.37, 21.86,
25.27, 36.11, 74.82, 93.91, 105.09, 121.75, 123.23, 127.08, 127.41, 128.07,
128.32, 129.85, 131.85, 140.50, 166.97 ppm; HRMS: m/z calcd for
C24H28OSi: 360.1909; found: 360.1900.
Alkylidene silacyclobutene [D2]-8b: Obtained when the reaction mixture
was quenched with DCl/D2O instead of 1n aqueous HCl. Colorless
liquid, GC yield 70%, isolated yield 66% (247 mg); 1H NMR (CDCl3,
TMS): d=0.49 (s, 6H), 0.83 (t, J=7.2 Hz, 3H), 1.03 (t, J=7.5 Hz, 3H),
1.27–1.32 (m, 2H), 1.49–1.57 (m, 2H), 2.10 (t, J=7.5 Hz, 2H), 2.24 (t, J=
7.2 Hz, 2H), 7.17–7.37 ppm (m, 10H); 13C NMR (CDCl3, TMS): d=
À0.55, 14.10, 14.14, 21.67, 23.25, 30.14, 31.96, 126.57, 126.71, 126.89,
127.36, 128.04, 128.57, 131.51 (t, J=21 Hz), 137.67, 138.64, 142.17, 142.90,
143.30, 148.34 (t, J=21 Hz), 156.92 ppm; HRMS: m/z calcd for
C26H30D2Si: 374.2399; found: 374.2397.
Alkynylsilyl allylic alcohol 16b: Pale yellow liquid, isolated yield 65%
(244 mg); 1H NMR (CDCl3, TMS): d=À0.09 (s, 6H), 0.73–1.13 (m, 6H),
1.23–1.89 (m, 8H), 1.96–2.00 (br, 1H), 6.02 (s, 1H), 7.14–7.66 ppm (m,
10H); 13C NMR (CDCl3, TMS): d=À0.32, 14.33,16.76, 41.49, 78.90,
93.94, 105.09, 123.26, 123.75, 127.18, 127.57, 128.06, 128.29, 129.15, 131.81,
140.68, 163.83 ppm; HRMS: m/z calcd for C25H32OSi: 376.2222; found:
376.2217.
Alkylidene silacyclobutene 8c: Colorless liquid, isolated yield 77%
(302 mg); 1H NMR (CDCl3, TMS): d=0.54 (s, 6H), 1.01 (t, J=7.2 Hz,
3H), 2.41 (q, J=7.2 Hz, 2H), 6.53 (s, 1H), 7.21–7.43 (m, 15H), 7.95 ppm
(s, 1H); 13C NMR (CDCl3, TMS): d=À0.51, 12.96, 23.74, 126.51, 126.81,
126.85, 126.95, 127.60, 128.21, 128.27, 128.59, 128.85, 130.18, 137.46,
137.97, 141.68, 142.27, 143.38, 144.34, 148.13, 158.30 ppm; HRMS: m/z
calcd for C28H28Si: 392.1960; found: 392.1967.
Alkynylsilyl allylic alcohol 16c: Yellow liquid, isolated yield 80%
(306 mg); 1H NMR (CDCl3, TMS): d=À0.09 (s, 6H), 1.69 (s, 3H), 2.20–
2.26 (br, 1H), 6.27 (s, 1H), 6.29–6.49 ppm (m, 15H); 13C NMR (CDCl3,
TMS): d=À0.42, À0.38, 28.47, 77.95, 93.66, 105.31, 122.77, 123.10, 125.80,
126.85, 127.23, 127.25, 127.84, 128.03, 128.31, 129.77, 131.78, 139.55,
145.33, 164.32 ppm.
General procedure for the preparation of alkynylsilyl–benzene deriva-
tives (14a-c) from reaction of five-membered zirconacyclopentadienes 4
or six-membered zirconacyclohexadienes 5 with DMAD in the presence
of CuCl: Five-membered zirconacyclopentadienes 4 were generated in
situ as described above. After the reaction mixture was cooled to 08C,
DMAD (2 mmol) and CuCl (2 mmol) were added. The reaction mixture
was then warmed up to room temperature and stirred at room tempera-
ture for 6 h. The reaction mixture was quenched with aqueous HCl (1n),
extracted with diethyl ether, then washed with saturated aqueous
NaHCO3, water and brine. The extract was dried over anhydrous MgSO4.
The solvent was evaporated in vacuo to give the crude product, which
was further purified by column chromatography.
Alkynylsilyl allylic alcohol 16d: Yellow liquid, GC yield 86%, isolated
yield 82% (325 mg); 1H NMR (CDCl3, TMS): d=À0.03 (s, 6H), 1.01 (t,
J=7.2 Hz, 3H), 1.90–1.96 (br, 1H), 2.16 (q, J=7.2 Hz, 2H), 6.31 (s, 1H),
6.72–7.44 ppm (m, 15H); 13C NMR (CDCl3): d=À0.40, À0.32, 7.96,
32.22, 80.28, 93.76, 105.31, 123.20, 123.52, 126.32, 126.81, 127.37, 127.41,
127.86, 128.14, 128.43, 129.83, 131.91, 139.59, 144.40, 163.32 ppm; HRMS:
m/z calcd for C27H28OSi: 396.1909; found: 396.1909.
Alkynylsilyl allylic alcohol 16e: Yellow liquid, GC yield 83%, isolated
yield 63% (250 mg); 1H NMR (CDCl3, TMS): d=À0.10 (s, 3H), À0.08
(s, 3H), 1.70 (s, 3H), 1.96–2.00 (br, 1H), 2.35 (s, 3H), 6.24 (s, 1H), 6.80–
7.44 ppm (m, 14H); 13C NMR (CDCl3): d=À0.38, À0.33, 21.04, 28.70,
78.03, 93.77, 105.30, 122.82, 125.78, 127.38, 128.14, 128.49, 128.72, 129.90,
131.93, 136.60, 139.68, 142.54, 164.43 ppm; HRMS: m/z calcd for
C27H28OSi: 396.1909; found: 396.1897.
Six-membered zirconacyclohexadienes 5 were generated in situ as de-
scribed above. After the reaction mixture was cooled to 08C, DMAD
(2 mmol) and CuCl (2 mmol) were added. The reaction mixture was then
warmed up to room temperature and stirred at room temperature for
6 h. Normal workup afforded the same alkynylsilyl–benzene derivatives
14.
Alkynylsilyl allylic alcohol 16 f: Colorless liquid, GC yield 72%, isolated
yield 63% (262 mg); 1H NMR (CDCl3, TMS): d=À0.10 (s, 3H), À0.07
(s, 3H), 1.70 (s, 3H), 2.00–2.04 (br, 1H), 6.23 (s, 1H), 6.78–7.44 ppm (m,
14H); 13C NMR (CDCl3): d=À0.45, À0.37, 28.80, 77.84, 93.46, 105.48,
123.09, 123.62, 127.39, 127.54, 127.59, 128.08, 128.16, 128.49, 129.85,
131.90, 132.79, 139.17, 144.15, 163.74 ppm.
Alkynylsilyl–benzene 14a: Colorless solid, m.p. 114–1168C, isolated yield
74% (378 mg) from 4, isolated yield 66% from 5; 1H NMR (CDCl3,
TMS): d=À0.02 (s, 6H), 0.68 (t, J=7.5 Hz, 3H), 0.99 (t, J=7.5 Hz, 3H),
1.14–1.40 (m, 2H), 1.60–1.77 (m, 2H), 2.32–2.50 (m, 2H), 2.60–2.75 (m,
2H), 3.79 (s, 3H), 3.89 (s, 3H), 7.11–7.62 ppm (m, 10H); 13C NMR
1900
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Chem. Eur. J. 2005, 11, 1895 – 1902

Zirconium Chemistry
FULL PAPER
Alkynylsilyl allylic alcohol 16g: Yellow liquid, GC yield 71%, isolated
yield 69% (298 mg); 1H NMR (CDCl3, TMS): d=À0.08 (s, 3H), À0.05
(s, 3H), 1.81 (s, 3H), 1.96–2.04 (br, 1H), 6.32 (s, 1H), 6.80–7.83 ppm (m,
17H); 13C NMR (CDCl3): d=À0.39, À0.32, 28.76, 78.34, 93.66, 105.44,
123.16, 123.77, 124.22, 124.66, 125.84, 125.96, 127.45, 127.73, 128.13,
128.25, 128.44, 129.85, 131.91, 132.47, 132.98, 139.44, 142.88, 163.95 ppm;
HRMS: m/z calcd for C30H28OSi: 432.1909; found: 432.1900.
Alkynylsilyl amide 18b: Colorless solid, isolated yield 67% (317 mg);
1H NMR (CDCl3, TMS): d=0.23 (s, 6H), 2.30 (s, 3H), 7.13–7.50 ppm (m,
15H); 13C NMR (CDCl3): d=0.19, 20.87, 90.56, 107.45, 120.17, 122.47,
125.61, 128.16, 128.52, 128.82, 128.91, 129.28, 129.51, 132.04, 134.47,
134.63, 136.46, 152.96, 166.06 ppm; HRMS: m/z calcd for C26H24BrNOSi:
473.0811; found: 473.0788.
Alkynylsilyl amide 18c: Yellow liquid, isolated yield 60% (313 mg);
1H NMR (CDCl3, TMS): d=0.18 (s, 6H), 4.52 (d, J=5.7 Hz, 2H), 7.26–
7.41 ppm (m, 16H); 13C NMR (CDCl3): d=À0.83, 43.82, 91.36, 105.60,
107.43, 122.63, 127.64, 128.09, 128.28, 128.38, 128.45, 128.63, 129.10,
131.95, 137.34, 137.58, 137.71, 158.86, 170.03 ppm; HRMS: m/z calcd for
C26H24INOSi: 521.0672; found: 521.0666.
Alkynylsilyl allylic alcohol 16h: Yellow liquid, GC yield 81%, isolated
1
yield 81% (298 mg); H NMR (CDCl3, TMS): d=À0.01 (s, 6H), 2.16 (br,
1H), 5.42 (s, 1H), 6.23 (s, 1H), 6.99–7.43 ppm (m, 15H); 13C NMR
(CDCl3): d=À0.26, À0.15, 79.48, 93.63, 105.52, 123.16, 127.01, 127.54,
127.69, 127.71, 128.12, 128.28, 128.44, 129.11, 131.93, 140.02, 141.22,
161.17 ppm; HRMS: m/z calcd for C25H24OSi: 368.1596; found: 368.1600.
Alkynylsilyl amide 18d: Yellow liquid, isolated yield 55% (260 mg);
1H NMR (CDCl3, TMS): d=0.19 (s, 6H), 4.52 (d, J=5.7 Hz, 2H), 7.26–
7.44 ppm (m, 16H); 13C NMR (CDCl3): d=0.17, 43.78, 90.59, 107.34,
122.52, 125.21, 127.64, 128.11, 128.16, 128.47, 128.67, 128.70, 128.85,
129.16, 132.03, 136.71, 137.49, 153.03, 168.23 ppm.
Alkynylsilyl allylic alcohol 16i: Colorless liquid, GC yield 93%, isolated
1
yield 79% (315 mg); H NMR (CDCl3, TMS): d=À0.01 (s, 6H), 2.08 (br,
1H), 3.77 (s, 3H), 5.37 (s, 1H), 6.21 (s, 1H), 6.78–7.43 ppm (m, 14H);
13C NMR (CDCl3): d=À0.22, À0.13, 55.20, 78.98, 93.74, 105.51, 113.73,
122.69, 123.21, 127.49, 127.69, 128.14, 128.36, 128.44, 129.10, 131.95,
133.43, 140.27, 159.20, 161.43 ppm; HRMS: m/z calcd for C26H26O2Si:
398.1702; found: 398.1709.
Alkynylsilyl allylic alcohol 16j: Yellow liquid, isolated yield 79%
(351 mg); 1H NMR (CDCl3, TMS): d=À0.02 (s, 3H), À0.03 (s, 3H),
5.27(s, 1H), 5.59 (br, 1H), 6.09 (s, 1H), 6.86–7.45 ppm (m, 19H);
13C NMR (CDCl3): d=À0.25, À0.14, 0.56, 0.64, 78.16, 79.10, 93.44, 93.64,
105.53, 107.21, 123.13, 126.88, 126.92, 126.98, 127.19, 127.40, 127.52,
127.67, 127.91, 127.95, 128.09, 128.15, 128.40, 128.62, 128.66, 128.83,
129.08, 131.81, 131.87, 139.19, 140.00, 140.22, 140.28, 140.33, 140.59,
140.72, 141.76, 142.78, 143.08, 166.11 ppm; HRMS: m/z calcd for
C31H28OSi: 444.1909; found: 444.1892.
Acknowledgement
This work was supported by the National Natural Science Foundation of
China (20172003, 20232010, 20328201), the Major State Basic Research
Development Program (G2000077502-D), and Dow Corning Corpora-
tion. Cheung Kong Scholars Program, Qiu Shi Science & Technologies
Foundation, and BASF are gratefully acknowledged.
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1H NMR (CDCl3, TMS): d=0.06 (s, 6H), 2.26 (s, 3H), 7.04–7.41 ppm (m,
16H); 13C NMR (CDCl3): d=À0.88, 20.76, 91.87, 106.32, 119.80, 122.76,
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1H NMR (CDCl3, TMS): d=0.06 (s, 6H), 7.22–7.45 ppm (m, 16H);
13C NMR (CDCl3): d=À0.85, 91.73, 106.49, 121.07, 122.79, 128.17,
128.69, 128.92, 128.94, 129.07, 129.50, 129.71, 131.94, 136.26, 136.99,
138.96, 150.54, 163.86 ppm; HRMS: m/z calcd for C25H22ClNOSi:
415.1159; found: 415.1171.
Alkynylsilyl amide 17c: Yellow liquid, isolated yield 43% (197 mg);
1H NMR (CDCl3, TMS): d=0.06 (s, 6H), 7.29–7.45 ppm (m, 16H);
13C NMR (CDCl3): d=À0.86, 91.71, 106.49, 117.12, 121.37, 122.77,
128.16, 128.69, 128.93, 129.07, 129.70, 131.86, 131.93, 136.74, 136.94,
139.00, 150.52, 163.85 ppm; HRMS: m/z calcd for C25H22BrNOSi:
459.0654; found: 459.0640.
Alkynylsilyl amide 17d: Yellow liquid, isolated yield 64% (253 mg);
1H NMR (CDCl3, TMS): d=0.03 (s, 6H), 4.49 (d, J=5.7 Hz, 2H), 7.21–
7.39 ppm (m, 17H); 13C NMR (CDCl3): d=À0.83, 44.05, 92.04, 106.24,
122.87, 127.36, 127.41, 128.15, 128.63, 129.61, 131.94, 137.49, 137.58,
138.10, 150.47, 166.04 ppm; HRMS: m/z calcd for C26H25NOSi: 395.1705;
found: 395.1690.
Alkynylsilyl amide 18a: Colorless solid, isolated yield 53% (276 mg);
1H NMR (CDCl3, TMS): d=0.22 (s, 6H), 2.30 (s, 3H), 7.11–7.48 ppm (m,
15H); 13C NMR (CDCl3): d=1.05, 20.87, 91.34, 106.04, 107.54, 120.25,
122.57, 128.14, 128.51, 128.85, 129.24, 129.51, 131.97, 134.51, 134.54,
137.47, 158.76, 167.88 ppm; HRMS: m/z calcd for C26H24INOSi:
521.0672; found: 521.0666.
Chem. Eur. J. 2005, 11, 1895 – 1902
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Received: July 8, 2004
Revised: October 2, 2004
Published online: January 26, 2005
1902
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