C O M M U N I C A T I O N S
Table 1. Co2(CO)8-Mediated Tandem [5 + 1]/[2 + 2 +
1]-Cycloadditions
1,2-addition of H2O or intramolecular proton transfer of their
corresponding intermediates D. Coordination of species D with a
tethered olefin species leads to oxidative cyclization to give cobalt-
containing cyclopentane species E. In the conversion of species D
to E, the C-C bond formation proceeds from the metal face such
that the methyl group is cis to the two neighboring protons. Insertion
of CO or reductive elimination of intermediate E gives the
derivative of cyclopentanone 5 or cyclobutane 6, respectively.
In summary, we have reported a new and highly stereocontrolled
coupling reaction of epoxyalkyne, CO, olefin which leads to tandem
cyclocarbonylation/[2 + 2 + 1] cycloadditions. The mechanism
involves an unusual cobalt-stablized cyclic allene intermediate. This
new approach is successfully extended to construct various tricyclic
carbo- and heterocyclic frameworks that can tolerate suitable oxygen
and nitrogen functionalities. Further application of this new method
to a short synthesis of complex bioactive molecules is under
investigation.
Acknowledgment. We thank National Science Council, Taiwan,
for support of this work.
Supporting Information Available: Experimental procedures,
synthetic schemes, and spectral data of new compounds 1-31 and X-ray
data of tricyclic compounds 5, 6, 22b and 28b (PDF).
References
(1) For general reviews, see: (a) Ho, T.-L. Tactics of Organic Synthesis;
Wiley-Interscience: New York, 1994; p 79. (b) Tietze, L. F. Chem. ReV.
1996, 96, 115. (c) Winkler, J. D. Chem. ReV. 1996, 96, 167. (d) Denmark,
S. E.; Thorarensen, A. Chem. ReV. 1996, 96, 137.
(2) For selected reviews, see: (a) Overman, L. E.; Abelman, M. M.; Kucera,
D. J.; Tran, V. D.; Ricca, D. J. Pure Appl. Chem. 1992, 64, 1813. (b)
Grigg, R. J Heterocycl. Chem. 1994, 31. 631. (c) de Meijere A.; Meyer,
P. E. Angew. Chem., Int. Ed. Engl. 1994, 33, 2379.
a Epoxyalkyne (1.0 equiv, 0.15 M) was treated with Co2(CO)8 (1.1 equiv)
in benzene at 23 °C for 2 h, followed by stirring at appropriate conditions.
Cond. A, CO (50 psi), benzene, 80 °C, 24 h; B, CO (1 atm), benzene, 75
°C, 12 h; C, N2, benzene, 80 °C, 24 h; D, N2, benzene, 28 °C, 24 h; E, CO
(1 atm), benzene, 60 °C, 24 h. b Yields were reported after silica column.
(3) For selected examples, see: (a) Trost, B. M.; Shi, Y. J. Am. Chem. Soc.
1991, 113, 701. (b) Overman, L. E. Ricca, D. J.; Tran, V. D. J. Am. Chem.
Soc. 1993, 115, 2042. (c) Trost, B. M.; Shen H. Angew. Chem., Int. Ed.
2001, 40, 2313. (d) Trost, B. M.; Calkins, T. L.; Bochet, C. G. Angew.
Chem., Int. Ed. Engl. 1997, 36, 2632. (e) Vorogushin, A. V.; Wulff, W.
D.; Hansen, H.-J. J. Am. Chem. Soc. 2002, 124, 6512.
Scheme 3
(4) For review papers, see: (a) Shore, N. E. In ComprehensiVe Organometallic
Chemistry II; Abel, E. W., Stone, F. G. A., Wilkenson, G., Eds.;
Pergamon: Oxford, 1995; Vol. 12, p 703. (b) Geis, O.; Schalz, H. Angew.
Chem., Int. Ed. 1998, 37, 911.
(5) (a) Jeong, N.; Hwang, S. H.; Lee, Y.; Chung, Y. K. J. Am. Chem. Soc.
1994, 116, 8793. (b) Hicks, F. A.; Buchwald, S. L. J. Am. Chem. Soc.
1996, 118, 11688. (c) Kondo, T.; Suzuki, N.; Okada, T.; Mitsudo, T. J.
Am. Chem. Soc. 1997, 119, 6187. (d) Koga, Y.; Kobayashi, T.; Narasaka,
K. Chem. Lett. 1998, 249. (e) Morimoto, T.; Chatani, N.; Kukumoto, Y.;
Murai, S. J. Org. Chem. 1997, 62, 3762. (f) Shiu, Y.-T.; Madhushaw, R.
J.; Li, W.-T.; Lee, G.-H.; Peng, S. H.; Liao, F.-L.; Wang, S.-L.; Liu, R.-
S., J. Am. Chem. Soc. 1999, 121, 4066.
Scheme 4
(6) (a) Brummond, K. M.; Lu, J. J. Am. Chem. Soc. 1999, 121, 5087. (b)
Tobisu, M.; Chatani, N.; Asaumi, T.; Amako, K.; Ie, Y.; Fukumoto, Y.;
Murai, S. J. Am. Chem. Soc. 2000, 122, 12633. (c) Kablaouni, N. M.;
Hicks, F. A.; Buchwald, S. L. J. Am. Chem. Soc. 1996, 118, 5818. (d)
Chatani, N.; Morimoto, T,; Fukumoto, Y.; Murai, S. J. Am. Chem. Soc.
1996, 120, 5335. (e) Chatani, Tobisu, M.; Asaumi, T.; Murai, S. Synthesis,
2000, 925. (f) Shibata, T.; Toshida, N.; Takagi, K. Org. Lett. 2002, 4,
1619.
(7) Co2(CO)6-complexed alkyne species is easily identified by its lower
polarity than that of alkyne on a TLC plate. It can be easily identified by
IR spectrum which shows a single band at 2050 cm-1. See Najdi, S. D.;
Olmsteaad, M. M.; Schore, N. E. J. Organomet. Chem. 1992, 431, 335.
(8) The ORTEP drawing and crystal data of tricyclic compounds 5, 6, 22b,
and 29b are provided in Supporting Information.
(9) The ease in the ring-opening of cis-epoxyalkyne is unclear at the present
stage. We believe that the vinyl or heteroatom at the cis substituent may
coordinate to the cobalt metal to increase its basicity that facilitates the
ring-opening of epoxide.
and methoxy functionalities 28c and 28d. Similar framework 30
was obtained in 89% yield from cis-epoxyalkyne 29 under the same
condition.
This new process likely involves an initial coupling of Co2(CO)8
with epoxyalkyne and CO in [5 + 1] mode, to give cobalt-stabilized
cyclic allene species10 D (Scheme 4), which was generated by the
ring-opening of epoxide 4 by SN2-attack of the Co2(CO)6 fragment.
The alcohols 2a-2b or pyran-2-one 3b are thought to derive from
(10) For metal-stabilized cyclic allene species, see: (a) Yin, J.; Abboud, K.
A.; Jones, W. M. J. Am. Chem. Soc. 1993, 115, 3810. (b) Jones, W. M.;
Klosin, J. AdV. Organomet. Chem. 1998, 42, 147.
JA0346633
9
J. AM. CHEM. SOC. VOL. 125, NO. 32, 2003 9611