C O M M U N I C A T I O N S
complex 5a was prepared by the treatment of tetraphenylzircona-
cyclopentadiene with t-BuOH. Selective monoprotonation pro-
ceeded to afford 5a cleanly. To the ring-opened linear zirconocene
3
compound 5a, 1 equiv of CrCl was added. The mixture was heated
to 50 °C and stirred. As expected, the desired tetraene 2a was
formed in 69% yield within 1 day. This result indicates that the
reaction from 11 to 2 is relatively fast. Rate-determining step is
the transmetalation or the ring-opening step.
presence of CrCl
3
. This is probably due to the low reactivity toward
insertion of nitriles or isocyanates. To the contrary, alkyl-substituted
zirconacyclopentadienes did not give tetramers of dialkylacetylenes
by the Zr/Cr system. This is probably because the ring opening is
not favorable in the case of tetraalkyl-substituted chromacyclopen-
tadienes.
Further investigation on the mechanism and new applications is
now in progress.
Supporting Information Available: Experimental details and
spectroscopic characterization of new compounds, and X-ray data for
a and 2c. This material is available free of charge via the Internet at
http://pubs.acs.org.
This prompted us to use the chromacyclopentadienes formed in
situ. Recently, we have reported the preparation of pyridines and
pyridones from azazirconacyclopentadienes in the presence of Ni(II)
2
7
complexes. However, it is well-known that zirconacyclopentadienes
do not directly react with usual nitriles8d or even after transmeta-
lation to Ni or Cu. Pyridines were not formed with Ni or Cu. It is
interesting to note that when the reaction mixture of tetrapropyl-
zirconacyclopentadiene with CrCl was treated with butyronitrile,
3
pentapropylpyridine 6a was obtained in 62% yield at 50 °C.
References
(
1) (a) Grotjahn, D. B. In ComprehensiVe Organometallic Chemistry II;
Hegedus, L. S., Abel, E. W., Stone, F. G. A., Wilkinson, G., Eds.;
Pergamon: Oxford, 1995; Vol. 12, pp 753-770. (b) Shore, N. E. In
ComprehensiVe Organic Synthesis; Trost, B. M., Fleming I., Eds.;
Pergamon: Oxford, 1991; Vol. 5, pp 1152-1162. (c) Mashima, K.;
Nakayama, Y.; Nakamura, A. Catalyst & Catalysis 1997, 39, 645-653.
(d) Eisch, J. J.; Ma, X.; Han, K. I.; Gitua, J. N.; Kr u¨ ger, C. Eur. J. Inorg.
Chem. 2001, 77-88.
Similarly, bicyclic zirconacyclopentadiene prepared from 4,9-
tridecadiyne reacted with butyronitrile after treatment with CrCl
3
to afford bicyclic pyridine derivative 6d in 84% yield. The reaction
of tetrapropylzirconacyclopentadiene with isocyanates gave pyridine
derivatives 7a and 7b in 60 and 84% yields, respectively. Thus,
(
2) (a) Bruce, M. I.; Hall, B. C.; Skelton, B. W.; White, A. H.; Zaitseva, N.
N. J. Chem. Soc., Dalton Trans. 2000, 2279. (b) Haskel, A.; Straub, T.;
Dash, A. K.; Eisen, M. S. J. Am. Chem. Soc. 1999, 121, 3014. (c) Haskel,
A.; Wang, J.; Straub, T.; Neyround, T. G.; Eisen, M. S. J. Am. Chem.
Soc. 1999, 121, 3025. (d) Burrows, A. D.; Green, M.; Jeffery, J. C.; Lynam,
J. M.; Mahon, M. F. Angew. Chem., Int. Ed. 1999, 38, 3043. (e) Biagini,
P.; Caporusso, A. M.; Funaioli, T.; Fachinetti, G. Angew. Chem. 1989,
the combination of zirconacyclopentadienes and CrCl
reactivity toward nitriles or isocyanates. When the mixture of
tetrapropylzirconacyclopentadiene and CrCl was treated with the
-octyne, hexapropylbenzene 9 was obtained in 87% yield. This
3
showed new
3
4
101, 1079.
reaction is similar to the Ni-mediated reaction of zirconacyclopen-
tadienes with alkynes.8f The reaction with an olefin having an
(3) A part of this work has been orally reported at the 227 ACS National
Meeting in Anaheim, CA, March 28, 2004.
electron-withdrawing group, such as acrylonitrile, proceeded to give
cyanocyclohexadiene derivative 8 in 56% yield. The results are
shown in Scheme 1.
(
4) For dimerization of internal alkynes with a zirconocenedibutyl complex,
see: (a) Negishi, E.; Cederbaum, F. E.; Takahashi, T. Tetrahedron Lett.
1986, 27, 2829. (b) Takahashi, T.; Swanson, R. D.; Negishi, E. Chem.
Lett. 1987, 623-626. (c) Negishi, E.; Holmes, S. J.; Tour, J.; Miller, J.
A.; Cederbaum, F. E.; Swanson, D. R.; Takahashi, T. J. Am. Chem. Soc.
1989, 111, 3336-3346. (d) Xi, Z.; Hara, R.; Takahashi, T. J. Org. Chem.
Scheme 1
1995, 60, 4444-4448.
(
(
(
(
5) Compound 2a has been obtained as a byproduct, and its X-ray structure
has been reported. However, there is no procedure for the formation of
2
a. See: Rheingold, A. L.; Staley, D. L.; Heck, R. F.; Silverberg, L. Acta
Crystallogr. 1990, C46, 144-146.
6) Compounds 4 were synthesized by the following procedure: To a solution
of a zirconacyclopentadiene (1 mmol) were added 1-iodo-1,2,3,4-tetraaryl-
(
3 4
1Z,3E)-butadiene (1 mmol), CuCl (1 mmol), and Pd(PPh ) (0.05 mmol).
After stirring the mixture at 50 °C for 24 h, 4 was obtained.
7) (a) Takahashi, T.; Tsai, F. Y.; Kotora, M. J. Am. Chem. Soc. 2000, 122,
4
994. (b) Takahashi, T.; Tsai, F. Y.; Li, Y. Z.; Wang, H.; Kondo, Y.;
Yamanaka, M.; Nakajima, K.; Kotora, M. J. Am. Chem. Soc. 2002, 124,
059.
5
8) For the transmetalation of zirconacyclopentadienes to Cu, see: (a)
Takahashi, T.; Xi, Z.; Yamazaki, A.; Liu, Y.; Nakajima, K.; Kotora, M.
J. Am. Chem. Soc. 1998, 120, 1672-1680. (b) Takahashi, T.; Hara, R.;
Nishihara, Y.; Kotora, M. J. Am. Chem. Soc. 1996, 118, 5154-5155. To
Bi: (c) Fagan, P. J.; Nugent, W. A. J. Am. Chem. Soc. 1988, 110, 2310-
2312. (d) Takahashi, T.; Li, Y. Z.; Ito, T.; Xu, F.; Nakajima, K.; Liu, Y.
H. J. Am. Chem. Soc. 2002, 124, 1144-1145. To Li: (e) Takahashi, T.;
Huo, S.; Hara, R.; Noguchi, Y.; Nakajima, K.; Sun, W.-H. J. Am. Chem.
Soc. 1999, 121, 1094-1095. To Ni: (f) Takahashi, T.; Tsai, F. Y.; Li,
Y.; Nakajima, K.; Kotora, M. J. Am. Chem. Soc. 1999, 121, 11093-
11100.
(
9) Wilke, G.; Benn, H.; Goddards, R.; Kruger, A. C.; Pfeil, B. Inorg. Chim.
Acta 1992, 198-200, 741-748.
Interestingly, zirconacyclopentadienes prepared from diaryl-
alkynes did not react with nitriles nor with isocyanates in the
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