Novel synthetic route to octasubstituted naphthalenes from four alkynes and one olefin unit via zirconacyclopentadienes and 1,2-Diiodo-3,4,5,6- tetraalkylbenzene

Article abstract of DOI:10.1021/jo0497297

1,2,3,4-Tetrasubstituted benzene derivatives were prepared by the reaction of zirconacyclopentadienes with vinyl bromide in the presence of NiCl ₂(PPh₃)₂. 1,2-Diiodo-3,4,5,6-tetraalkylbenzenes were formed by treatment of 1,2,3,4-tetraalkylbenzenes with iodine and periodic acid in the presence of a catalytic amount of sulfuric acid. Reaction of the 1,2-diiodo-3,4,5,6-tetraalkylbenzenes with zirconacyclopentadienes in the presence of a stoichiometric amount of CuCl gave sterically crowded octasubstituted naphthalenes in moderate yields.

Full text of DOI:10.1021/jo0497297

SCHEME 1
Novel Syn th etic Rou te to Octa su bstitu ted
Na p h th a len es fr om F ou r Alk yn es a n d On e
Olefin Un it via Zir con a cyclop en ta d ien es
a n d 1,2-Diiod o-3,4,5,6-tetr a a lk ylben zen e
Xin Zhou,† Zhiping Li,† Hui Wang,† Masanori Kitamura,†
Ken-ichiro Kanno,† Kiyohiko Nakajima,‡ and
Tamotsu Takahashi*,†
SCHEME 2
Catalysis Research Center and Graduate School of
Pharmaceutical Sciences, Hokkaido University,
and SORST, J apan Science and Technology Corporation
(J ST), Sapporo 001-0021, J apan, and Department of
Chemistry, Aichi University of Education, Igaya,
Kariya 448-8542 J apan
tamotsu@cat.hokudai.ac.jp
Received February 16, 2004
Abst r a ct : 1,2,3,4-Tetrasubstituted benzene derivatives
were prepared by the reaction of zirconacyclopentadienes
with vinyl bromide in the presence of NiCl2(PPh3)2. 1,2-
Diiodo-3,4,5,6-tetraalkylbenzenes were formed by treatment
of 1,2,3,4-tetraalkylbenzenes with iodine and periodic acid
in the presence of a catalytic amount of sulfuric acid.
Reaction of the 1,2-diiodo-3,4,5,6-tetraalkylbenzenes with
zirconacyclopentadienes in the presence of a stoichiometric
amount of CuCl gave sterically crowded octasubstituted
naphthalenes in moderate yields.
of octasubstituted naphthalenes by coupling of four
alkynes and one vinyl bromide as shown in Scheme 2.
Methods for preparation of 1,2,3,4-tetrasubstituted
benzene derivatives from alkynes are very limited. In this
strategy, a novel synthetic method of 1,2,3,4-tetrasub-
(2) Representative examples for the synthesis of octasubstituted
naphthalenes. Via the Diels-Alder reaction: (a) Tong, L.; Ho, D. M.;
Vogelaar, N. J .; Schutt, C. E.; Pascal, R. A., J r. J . Am. Chem. Soc.
1997, 119, 7291. (b) Qiao, X.; Padula, M. A.; Ho, D. M.; Vogelaar, N.
J .; Schutt, C. E.; Pascal, R. A., J r. J . Am. Chem. Soc. 1996, 118, 741.
(c) Troll, T.; Schmid, K. Tetrahedron Lett. 1984, 25, 2981. (d) Hart,
H.; Teuerstein, A. Synthesis 1979, 693. (e) Hart, H.; Oku, A J . Org.
Chem. 1972, 37, 4269. See also: (f) Zhang, J .; Ho, D. M.; Pascal, R. A.,
J r. J . Am. Chem. Soc. 2001, 123, 10919. Via nucleophilic substitution:
(g) Biemans, H. A. M.; Zhang, C.; Smith, P.; Kooijman, H.; Smeets, W.
J . J .; Spek, A. L.; Meijer, E. W. J . Org. Chem. 1996, 61, 9012. (h)
Downing, G. A.; MacNicol, D. D.; Mallinson, P. R.; Milligan, P. K. Acta
Crystallogr. 1996, C52, 2887. (i) MacNicol, D. D.; McGregor, W. M.;
Mallinson, P. R.; Robertson, C. D. J . Chem. Soc., Perkin Trans. 1 1991,
3380. With bicyclo[2.2.0]octane frameworks: (j) Matsuura, A.; Nishi-
naga, T.; Komatsu, K. Tetrahedron Lett. 1999, 40, 123. Others: (k)
Roush, W. R.; Coffey, D. S.; Madar, D. J . J . Am. Chem. Soc. 1997, 119,
11331. (l) Ashton, P. R.; Brown, G. R.; Foubister, A. J .; Smith, D. R.;
Spencer, N.; Stoddart, J . F.; Williams, D. J . Tetrahedron Lett. 1993,
34, 8333.
(3) For studies on the structures of octasubstituted naphthalenes,
see: (a) Simaan, S.; Marks, V.; Gottlieb, H. E.; Stanger, A.; Biali S. E.
J . Org. Chem. 2003, 68, 637. (b) Christofi, A. M.; Garratt, P. J .;
Hogarth, G.; Ibbett, A. J .; Ng, Y.-F.; Steed, J . W. Tetrahedron 2002,
58, 4543. (c) Pascal, R. A., J r.; Barnett, L.; Qiao, X.; Ho, D. M. J . Org.
Chem. 2000, 65, 7711. (d) Oiao, X.; Pelczer, I.; Pascal, R. A., J r.
Chirality 1998, 10, 154. (e) Garc´ıa, R.; Riera, J .; Carilla, J .; J ulia´, L.;
Sa´nchez-Baeza, F. J .; Molins, E. Tetrahedron 1995, 51, 3627. (f) Sim,
G. A. Acta Crystallogr. 1982, B38, 623. (g) Hart, H.; Teuerstein, A.;
J effares, M.; Kung, W.-J . H.; Ward, D. L. J . Org. Chem. 1980, 45, 3731.
(h) Ward, D. L. Acta Crystallogr. 1980, B36, 963. (i) Gafner, G.;
Herbstein, F. H. Nature 1963, 200, 130. (j) Donaldson, D. M.;
Robertson, J . M. J . Chem. Soc. 1953, 17. See also ref 2a,b,f-i.
(4) (a) Takahashi, T.; Li, Y.; Stepnicka, P.; Kitamura, M.; Liu, Y.;
Nakajima, K.; Kotora, M. J . Am. Chem. Soc. 2002, 124, 576. (b)
Takahashi, T.; Hara, R.; Nishihara, Y.; Kotora, M. J . Am. Chem. Soc.
1996, 118, 5154. (c) Takahashi, T.; Tsai, F.-Y.; Li, Y.; Nakajima, K.;
Kotora, M. J . Am. Chem. Soc. 1999, 121, 11093. (d) Takahashi, T.; Xi,
Z.; Yamazaki, A.; Liu, Y.; Nakajima, K.; Kotora, M. J . Am. Chem. Soc.
1998, 120, 1672. (e) Takahashi, T.; Kotora, M.; Xi, Z. J . Chem. Soc.,
Chem. Commun. 1995, 361. (f) Takahashi, T.; Kitamura, M.; Shen,
B.; Nakajima, K. J . Am. Chem. Soc. 2000, 122, 12876. (g) Takahashi,
T.; Tsai, F.-Y.; Li, Y.; Wang, H.; Kondo, Y.; Yamanaka, M.; Nakajima,
K.; Kotora, M. J . Am. Chem. Soc. 2002, 124, 5059. (h) Takahashi, T.;
Tsai, F.-Y.; Kotora, M. J . Am. Chem. Soc. 2000, 122, 4994. (i) Xi, Z.-
F.; Sato, K.; Gao, Y.; Lu, J .-M.; Takahashi, T. J . Am. Chem. Soc. 2003,
125, 9568.
Octasubstituted naphthalenes have attracted consider-
able interest in the field of synthetic organic chemistry,1
because synthetic methodology of the octasubstituted
naphthalenes is usually limited as a result of the steric
repulsion caused by the eight substituents on the naph-
thalene ring.2 The overcrowded naphthalene cores are
twisted from planar to release the steric hindrance and
form a twisted aromatic ring system that has unique
structural characteristics and properties.3
There are several precedented synthetic methods for
the persubstituted naphthalenes, such as Diels-Alder
reaction,2a-f nucleophilic substitution of perfluoronaph-
thalene,2g-j coupling reactions of the lithiated butadiene
and dibromobenzene derivatives having a bicyclo[2.2.0]
framework,2i and so on.2k,l However, in these methods it
is difficult to prepare the naphthalenes with mixed
substituents. The simplest way to prepare the octasub-
stituted naphthalene is the coupling of four internal
alkynes and one acetylene as shown in Scheme 1. To
realize this reaction, transition-metal-mediated coupling
of internal alkynes is one attractive method.
Our group has developed zirconium-mediated highly
selective coupling reactions of internal alkynes to con-
struct a series of aromatic rings.4 In this paper, we
describe a zirconium-mediated method for the synthesis
* To whom correspondence should be addressed. Phone: +81-11-
706-9149. Fax: +81-11-706-9150.
† Hokkaido University.
‡ Aichi University of Education.
(1) For reviews for substituted naphthalenes, see: (a) de Koning,
C. B.; Rousseau A. L.; van Otterlo, W. A. L. Tetrahedron 2003, 59, 7.
(b) Balasubramaniyan, V. Chem. Rev. 1966, 66, 567.
10.1021/jo0497297 CCC: $27.50 © 2004 American Chemical Society
Published on Web 05/29/2004
J . Org. Chem. 2004, 69, 4559-4562
4559

SCHEME 3
to give the corresponding diiodobenzenes 6b-d in good
yields (eq 2).6
Finally, the desired octasubstituted naphthalenes 7
were produced via a coupling reaction between 1,2-di-
iodobenzene 6 with a second zirconacyclopentadiene 1′
(eq 3), which could be either the same or different from
the first zirconacyclopentadiene 1.4a,b The coupling reac-
tion proceeded smoothly in the presence of CuCl at 50
°C, and after 3 h of stirring, the corresponding octasub-
stituted naphthalenes 7a -g were obtained in good yields.
All results are summarized in Table 1. The best yield was
achieved when tetraphenylzirconacycle 1d was used,
probably as a result of the smaller steric hindrance of
7d at the peri-position compared to that of the peralky-
lated derivatives.
stituted benzenes had to be developed. To obtain the
1,2,3,4-tetrasubstituted benzene, acetylene or its equiva-
lent is required as the third alkyne, since tetrasubstituted
zirconacyclopentadienes as intermediates are readily
available from two internal alkynes and Cp2ZrBu2 or
Cp2ZrEt2. We used vinyl bromide as an acetylene equiva-
lent. The thus-formed 1,2,3,4-tetrasubstituted benzenes
were converted into diiodides, which in turn reacted with
the second zirconacyclopenadienes to give octasubstituted
naphthalenes as shown in Scheme 2.
It is known that 1,2,3,4-tetraalkylbenzene formation
from alkynes is very limited. Usually, coupling reaction
of alkynes gives a mixture of regioisomers of alkyl-
substituted benzenes. Although rearrangement of the
alkyl substituents on the benzene rings has been reported
as the J acobsen reaction, only 1,2,3,4-tetramethyl- or
-tetraethylbenzene has been synthesized by this method.5
We have already reported selective formation of ben-
zene derivatives from alkynes via zirconacyclopenta-
dienes.4d,e Here we developed a novel preparative method
of 1,2,3,4-tetraalkylbenzene derivatives by the reaction
of zirconacyclopentadienes and vinyl bromide. As shown
in eq 1, zirconacyclopentadiene 1 reacted with vinyl
bromide (2.0 equiv) in the presence NiCl2(PPh3)2 (1.1
equiv) to afford the corresponding 1,2,3,4-tetrasubstituted
benzenes 2 in good yields. In this reaction, vinyl bromide
acted as an acetylene equivalent.
These results clearly show the advantage of this zir-
conocene-mediated method. That is, zirconacyclopenta-
dienes could be efficiently used for the naphthalene cores.
Different substitutents could be introduced in the naph-
thalene by changing the zirconacyclopentadines. For
example, when tetraethylzirconacyclopentadiene 1a pre-
pared from 3-hexyne and Cp2ZrBu2 coupled with 1,2-
diiodo-3,4,5,6-tetramethylbenzene (6a ), mixed methyl-
and ethyl-substituted naphthalenes 7a could be obtained
in good yield. In a similar way, ethyl- and phenyl-
substituted naphthalene 7d was also obtained in high
yield. With the bicyclic zirconacycle 1e, which was
prepared from 3,9-dodecadiyne, the corresponding tet-
rahydroanthracene 7e was formed. Furthermore, unsym-
metrical zirconacycles can be easily prepared by a
selective cyclization of two different alkynes with zir-
conocene as we reported previously.7 So unsymmetrical
zirconacycles 1f and 1g were used in this reaction to
afford the naphthalene (7f and 7g, respectively) with
three different substituents. To the best of our knowledge,
these persubstituted naphthalenes are unprecedented
even though they have simple substitution patterns.
Figure 1 shows the result of X-ray crystallographical
analysis of naphthalene 7d . The naphthalene ring was
twisted to release the steric repulsion as reported.3 The
The proposed reaction mechanism is shown in Scheme
3. First, transmetalation from Zr to Ni proceeds to give
a nickelacycle 3 as we reported.4c Then insertion of
vinyl bromide followed by migration of an sp2 carbon and
â-H elimination seem reasonable to afford the final
product.
Iodination of the tetraalkylbenzenes 2b-d with iodine
(3.9 equiv) and periodic acid (1.7 equiv) in the presence
of a catalytic amount of sulfuric acid proceeds smoothly
(6) (a) Suzuki, H. Organic Syntheses; Wiley: New York, 1988;
Collect. Vol. VI, p 700. (b) Suzuki, H.; Nakamura, K.; Goto, R. Bull.
Chem. Soc. J pn. 1966, 39, 128. (c) Suzuki, H.; Haruta, Y. Bull. Chem.
Soc. J pn. 1973, 46, 589-592
(7) (a) Xi, Z.; Hara, R.; Takahashi, T. J . Org. Chem. 1995, 60, 4444.
(b) Takahashi, T.; Kageyama, M.; Denisov, V.; Hara, R.; Negishi, E.
Tetrahedron Lett. 1993, 34, 687. See also ref 4c-e.
(5) (a) Smith, L. I.; Guss, C. O. J . Am. Chem. Soc. 1940, 62, 2631-
2635: (b) Marvell, E. N.; Webb, D. J . Org. Chem. 1962, 27, 4408-
4412
4560 J . Org. Chem., Vol. 69, No. 13, 2004

TABLE 1. F or m a tion of Octa su bstitu ted Na p h th a len es
F IGURE 1. Perspective view of naphthalene 7d . C(14) of an
ethyl group is disordered.
(2b). To a THF (5 mL) solution of Cp2ZrCl2 (292 mg, 1.0 mmol)
was added n-BuLi (1.59 M hexane solution, 1.26 mL, 2.0 mmol)
at -78 °C, and the mixture was stirred for 1 h. 3-Hexyne (0.22
mL, 2.0 mmol) was added, and the mixture was warmed to room
temperature. After 3 h, vinyl bromide (0.14 mL, 2.0 mmol) and
NiCl2(PPh3)2 (0.65 g, 1.0 mmol), which was prepared from NiCl2-
(H2O)6 and PPh3,8 were added to the resulting reaction mixture
at room temperature. After stirring for 1 h, the mixture was
quenched with 3 N HCl and extracted with hexane. The
combined organic extracts were dried over MgSO4 and concen-
trated in vacuo. The residue was purified by column chroma-
tography on silica gel (hexane as eluent) to afford the title
compound as a colorless oil (91 mg, 48% isolated yield). NMR
yield, 53%. All spectral data are consistent with the literature.4i
1,2,3,4-Tetr a p r op ylben zen e (2c). 4-Octyne (40.0 mmol) was
used as starting material. Colorless oil (2.54 g, 52% isolated
yield). All spectral data are consistent with the literature.4i
1,2,3,4-Tetr a bu tylben zen e (2d ). 5-Decyne (20.0 mmol) was
used as starting material in this case. Colorless oil (1.55 g,
1
isolated yield 55%). H NMR (CDCl3, Me4Si): δ 1.00 (t, J ) 7.5
Hz, 6H), 1.03 (t, J ) 6.9 Hz, 6H), 1.40-1.66 (m, 16H), 2.58-
2.66 (m, 8H), 6.98 (s, 2H). 13C NMR (CDCl3, Me4Si): δ 13.9, 14.0,
23.1, 23.5, 28.8, 32.8, 33.6, 33.9, 126.7, 138.4, 138.6. HRMS:
calcd for C22H38 302.2973, found 302.2964.
Typ ica l Rea ction P r oced u r e for Iod in a tion of 1,2,3,4-
Tetr a a lk ylben zen es.6 P r ep a r a tion of 5,6-Diiod o-1,2,3,4-
tetr a eth ylben zen e (6b). 1,2,3,4-Tetraethylbenzene 2b (1.90 g,
10.0 mmol) was dissolved in 80% acetic acid (50 mL) and added
with 10 mL of concentrated sulfuric acid, iodine (10.0 g, 39.0
mmol), and periodic acid (3.89 g, 17.0 mmol). The mixture was
rapidly stirred and heated at 70-80 °C for 1 h. Saturated
aqueous solution of sodium hydrogensulfite was added to remove
an excess of iodine. The white precipitate was collected by
filtration and purified by recrystallization from ethanol to afford
the title compound as a colorless solid (3.80 g, 81% isolated yield).
All data are consistent with the literature.6
1,2-Diiod o-3,4,5,6-tetr a p r op ylben zen e (6c). 1,2,3,4-Tetra-
propylbenzene 2c (5.0 mmol) was used as starting material.
Recrystallization from ethanol gave the title compound as a
colorless solid (1.37 g, 55% isolated yield). 1H NMR (CDCl3,
Me4Si): δ 1.03 (t, J ) 7.3 Hz, 6H), 1.04 (t, J ) 7.3 Hz, 6H), 1.45-
1.58 (m, 8H), 2.54-2.58 (m, 4H), 2.93-3.00 (m, 4H). 13C NMR
(CDCl3, Me4Si): δ 14.50, 15.0, 23.1, 24.6, 33.4, 45.1, 116.1, 140.1,
144.4. HRMS calcd for C18H28I2 498.0269, found 498.0281. Anal.
Calcd for C18H28I2: C, 43.39; H, 5.66; I, 50.94. Found: C, 43.58;
H, 5.64; I, 50.77.
a
b
Used in 2.0 equiv to 6 unless otherwise noted. Prepared from
the iodination of 1,2,3,4-tetramethylbenzene. c Used in 4.0 equiv
to 6b.
end-to-end twist angle of 7d was 27°, which is in the
range of the usual twist angle (20-30°) of octasubstituted
naphthalenes.
In summary, we have reported an effective method to
synthesize octasubstituted naphthalenes from four alkynes
and a vinyl halide via zirconacyclopentadienes.
1,2-Diiod o-3,4,5,6-Tet r a b u t ylb en zen e (6d ). 1,2,3,4-Tet-
rabutylbenzene 2d (3.0 mmol) was used as starting material.
Exp er im en ta l Section
(8) (a) Venanzi, L. M. J . Chem. Soc. 1958, 719. (b) Yamamoto, K.
Bull. Chem. Soc. J pn. 1954, 27, 501. (c) Cotton, F. A.; Faut, O. D.;
Goodgame, D. M. L. J . Am. Chem. Soc. 1961, 83, 344.
Typ ica l P r oced u r e for P r ep a r a tion of 1,2,3,4-Tetr a su b-
stitu ted Ben zen e Der iva tives. 1,2,3,4-Tetr a eth ylben zen e
J . Org. Chem, Vol. 69, No. 13, 2004 4561

Recrystallization from ethanol gave the title compound as a
colorless solid (1.15 g, 69%). 1H NMR (CDCl3, Me4Si): δ 0.98 (t,
J ) 6.9 Hz, 12H), 1.45-1.57 (m, 16H), 2.59 (t, J ) 7.9 Hz, 4H),
2.98 (t, J ) 8.0 Hz, 4H). 13C NMR (CDCl3, Me4Si): δ 13.8, 13.9,
23.1, 23.4, 30.8, 31.8, 33.3, 42.7, 116.0, 140.1, 144.4. HRMS calcd
for C22H36I2 554.0906, found 554.0885. Anal. Calcd for C22H36I2:
C, 47.67; H, 6.55; I, 45.79. Found: C, 47.45; H, 6.32; I, 45.84.
Rep r esen ta tive P r oced u r e for Cou p lin g Rea ction of
Zir con a cyclop en ta d ien es 1′ a n d 1,2,3,4-Tetr a a lk yl-5,6-d i-
iod oben zen es 6. Syn th esis of 1,2,3,4-tetr a eth yl-5,6,7,8-
tetr a p h en yln a p h th a len e (7d ). To a solution of Cp2ZrCl2 (584
mg, 2.0 mmol) in THF (10 mL) was added n-butyllithium (1.59
M in hexane solution, 2.5 mL, 4.0 mmol) at -78 °C. After the
mixture stirred for 1 h at the same temperature, diphenylacety-
lene (712 mg, 4.0 mmol) was added, and the reaction mixture
was warmed to room temperature for 3 h. Then copper(I)
chloride (416 mg, 4.2 mmol), DMPU (0.73 mL, 6.0 mmol), and
1,2,3,4-tetraethyl-5,6-diiodobenzene (6b) (221 mg, 0.5 mmol)
were added and stirred at 50 °C for 3 h. After usual workup,
the crude mixture was purified by column chromatography on
silica gel (hexane/ethyl acetate ) 99/1) to afford the title
compound (203 mg, 75% isolated yield) as a colorless solid. Single
crystals suitable for X-ray structural analysis were prepared by
0.99 (t, J ) 6.9 Hz, 12H), 1.11-1.23 (m, 8H), 1.26-1.36 (m, 8H),
1.41-1.57 (m, 16H), 2.66 (t, J ) 7.5 Hz, 8H), 2.89 (t, J ) 7.5
Hz, 8H). 13C NMR (CDCl3, Me4Si) δ 14.0, 23.1, 23.5, 29.5, 31.4,
33.9, 34.0, 133.3, 133.7, 135.0. HRMS calcd for C42H72 576.5634,
found 576.5641.
1,2,3,4,9,10-Hexa eth yl-6,7,8,9-tetr a h yd r oa n th r a cen e (7e).
Zirconacycle 1e was prepared from Cp2ZrCl2 (584 mg, 2.0 mmol),
3,9-dodecadiyne (391 µL, 2.0 mmol), and n-BuLi (1.59 M in
hexane, 2.5 mL, 4.0 mmol). 1,2-Diiodo-3,4,5,6-tetraethylbenzene
(6b) (442 mg, 1.0 mmol) was used as the coupling partner.
1
Isolated yield 30%, GC yield 50%, white solid. H NMR (CDCl3,
Me4Si): δ 1.07 (t, J ) 7.5 Hz, 6H), 1.15 (t, J ) 7.2 Hz, 6H), 1.16
(t, J ) 7.5 Hz, 6H), 1.74, (br, 4H), 2.73 (q, J ) 7.5 Hz, 4H), 2.77-
(br, 4H), 2.83(q, J ) 6.9 Hz, 4H), 2.85(q, J ) 7.5 Hz, 4H). 13C
NMR (CDCl3, Me4Si): δ 14.9, 15.8, 16.8, 22.2, 23.4, 24.3, 24.5,
27.4, 132.7, 134.1, 134.3, 134.6, 136.9. HRMS calcd for C26H38
350.2973, found 350.2964.
5,6-Diet h yl-1,2,3,4-t et r a m et h yl-7,8-d ip h en yln a p h t h a -
len e (7f). To a solution of Cp2ZrCl2 (643.1 mg, 2.2 mmol) in THF
(10 mL) was added ethylmagnesium bromide (4.4 mmol, 0.89
M in THF solution, 4.94 mL) at -78 °C. After 1 h of stirring at
the same temperature, diphenylacetylene (356.5 mg, 2.0 mmol)
was added, and the reaction mixture was stirred at 0 °C for 3 h.
Then 3-hexyne (0.227 mL, 2.0 mmol) was added, and the mixture
was heated at 50 °C for 1 h. Copper(I) chloride (416 mg, 4.2
mmol), DMPU (0.73 mL, 6.0 mmol), and 1,2-diiodo-3,4,5,6-
tetramethylbenzene 6a (386 mg, 1.0 mmol) were added at room
temperature. The mixture was stirred at 50 °C for 3 h. After
usual workup, the crude mixture was purified by column
chromatography on silica gel (hexane/ethyl acetate ) 99/1) to
afford the title compound (208 mg, 53% isolated yield) as a white
1
crystallization from AcOEt/hexane. H NMR (CDCl3, Me4Si): δ
0.68 (t, J ) 7.3 Hz, 6H), 1.20 (t, J ) 7.4 Hz, 6H), 2.33 (q, J ) 7.3
Hz, 4H), 2.74 (q, J ) 7.4 Hz, 4H), 6.59-6.62 (m, 4H), 6.77-6.79
(m, 6H), 6.99-7.04 (m, 10H). 13C NMR (CDCl3, Me4Si): δ 15.9,
16.3, 22.7, 23.1, 124.6, 125.6, 126.2, 126.9, 131.4, 131.5, 132.7,
136.4, 136.7, 137.4, 139.2, 141.2, 143.6. HRMS calcd for C42H40
544.3130, found 544.3132. Anal. Calcd for C42H40: C, 92.60; H,
7.40. Found: C, 92.74; H, 7.31.
5,6,7,8-Tetr a eth yl-1,2,3,4-tetr a m eth yln a p h th a len e (7a ).
Zirconacycle 1a was prepared from Cp2ZrCl2 (584 mg, 2.0 mmol),
3-hexyne (454.4 µL, 4.0 mmol), and n-BuLi (1.59 M in hexane
solution, 2.5 mL, 4.0 mmol). 1,2-Diiodo-3,4,5,6-tetramethylben-
zene (6a ) (386 mg, 1.0 mmol) was used as the starting material.
1
solid. GC yield 60%. H NMR (CDCl3, Me4Si): δ 0.97 (t, J ) 7.5
Hz, 3H), 1.22 (t, J ) 7.2 Hz, 3H), 1.70 (s, 3H), 2.22 (s, 3H), 2.39
(s, 3H), 2.64 (q, J ) 7.5 Hz, 2H), 2.68 (s, 3H), 3.20 (q, J ) 7.2
Hz, 2H), 6.87-7.14 (m, 10H). 13C NMR (CDCl3, Me4Si) δ 15.77,
16.70, 17.05, 17.37, 20.83, 21.95, 23.73, 24.81, 125.06, 125.49,
126.70, 126.80, 128.19, 130.44, 131.02, 131.76, 132.20, 133.32,
133.83, 134.91, 135.70, 136.50, 137.13, 138.94, 141.73, 144.05.
HRMS calcd for C30H32 392.2504, found 392.2509.
1
Isolated yield 62%, GC yield 70%, white solid. H NMR (CDCl3,
Me4Si): δ 1.15 (t, J ) 7.5 Hz, 6H), 1.20 (t, J ) 7.5 Hz, 6H), 2.32
(s, 6H), 2.53 (s, 6H), 2.81 (q, J ) 7.5 Hz, 4H), 2.97 (q, J ) 7.5
Hz, 4H). 13C NMR (CDCl3, Me4Si): δ 15.9, 16.8, 17.0, 21.5, 22.2,
24.5, 128.4, 132.0, 134.5, 134.7, 137.2. HRMS calcd for C22H32
296.2504, found 296.2506
1,2,3,4,5,6,7,8-Octa eth yln a p h th len e (7b). Zirconacycle 1a
was prepared from Cp2ZrCl2 (584 mg, 2.0 mmol), 3-hexyne (454.4
µL, 4.0 mmol), and n-BuLi (1.59 M in hexane solution, 2.5 mL,
4.0 mmol). 1,2-Diiodo-3,4,5,6-tetraethylbenzene (6b) (442 mg, 1.0
mmol) was used as starting material. Isolated yield 52%, white
solid. 1H NMR (CDCl3, Me4Si): δ 1.14 (t, J ) 7.3 Hz, 12H), 1.17
(t, J ) 7.3 Hz, 12H), 2.78 (q, J ) 7.3 Hz, 8H), 2.96 (q, J ) 7.3
Hz, 8H). 13C NMR (CDCl3, Me4Si) δ 15.9, 16.5, 22.3, 24.3, 134.1,
134.8, 136.5. HRMS calcd for C26H40 352.3130, found 352.3131.
Anal. Calcd for C26H40: C, 88.57; H, 11.43. Found: C, 88.41; H,
11.58.
5,6-Die t h yl-1,2,3,4-t e t r a m e t h yl-7,8-d ip r op yln a p h t h a -
len e (7g). This reaction was carried out in the same way
described above for 7f using 4-octyne instead of diphenylacety-
lene. Isolated yield 41%, GC yield 59%, colorless oil. 1H NMR
(CDCl3, Me4Si): δ 0.91 (t, J ) 7.5 Hz, 3H), 1.04 (t, J ) 7.2 Hz,
3H), 1.15 (t, J ) 7.5 Hz, 3H), 1.19 (t, J ) 7.5 Hz, 3H), 1.44-1.55
(m, 4H), 2.31 (s, 6H), 2.51 (s, 3H), 2.52 (s, 3H), 2.67-2.73 (m,
2H), 2.79 (q, J ) 7.5 Hz, 2H), 2.86-2.91 (m, 2H), 2.96(q, J ) 7.5
Hz, 2H). 13C NMR (CDCl3, Me4Si): δ 14.90, 14.97, 15.85, 16.72,
16.94, 21.26, 21.49, 22.34, 24.45, 25.07, 25.43, 31.94, 34.28,
128.35, 128.37, 131.83, 131.88, 133.66, 134.51, 134.55, 135.95,
137.30. HRMS calcd for C24H36 324.2817, found 324.2791
1,2,3,4,5,6,7,8-Octa bu tyln a p h th a len e (7c). Zirconacycle 1c
was prepared from Cp2ZrCl2 (584 mg, 2.0 mmol), 5-Decyne (718
µL, 4.0 mmol), and n-BuLi (1.59 M in hexane, 2.5 mL, 4.0 mmol).
1,2-Diiodo-3,4,5,6-tetrabutylbenzene 6d (554 mg, 1.0 mmol) was
used as the coupling partner. Isolated yield 40%, GC yield 52%,
colorless oil. 1H NMR (CDCl3, Me4Si): δ 0.81 (t, J ) 7.2 Hz, 12H),
Su p p or tin g In for m a tion Ava ila ble: X-ray crystallo-
graphic data of naphthalene 7d and and NMR spectra for 2d ,
7a , 7c, 7e, 7f, and 7g. This material is available free of charge
via the Internet at http://pubs.acs.org.
J O0497297
4562 J . Org. Chem., Vol. 69, No. 13, 2004