J . Org. Chem. 2001, 66, 4433-4436
4433
Sch em e 1. Cycloisom er iza tion of En yn es
Ir id iu m (I)-Ca ta lyzed Cycloisom er iza tion of
En yn es
Naoto Chatani, Hiroki Inoue, Tsumoru Morimoto,†
Toyoshige Muto, and Shinji Murai*
Department of Applied Chemistry, Faculty of Engineering,
Osaka University, Suita, Osaka 565-0871, J apan
murai@chem.eng.osaka-u.ac.jp
Received J anuary 23, 2001
The development of new, efficient methods for the
construction of ring systems from simple acyclic building
blocks represents an important ongoing challenge for
synthetic organic chemists.1 One of the most extensively
studied, recent approaches involves the transition-metal-
catalyzed cycloisomerization of enynes.2 A variety of such
reactions have been developed thus far, and they can be
classified into several types, depending on the type of
transformation: (1) to cyclopentane derivatives contain-
ing an exo 1,3- or 1,4-diene unit,3 (2) to bicyclo[4.2.0]-
octene derivatives via a [2 + 2] cycloaddition,4 (3) to
bicyclo[4.1.0]heptene derivatives,5 (4) to seven-membered
cyclic alkenes,6 (5) to eight-membered cyclic dienylsilane,7
and (6) to 1-vinylcycloalkenes via skeletal reorganiza-
tion.8,9 The reaction course is complicated and depends
on reaction variables, such as the structure of the
substrates, the nature of the catalysts, additives, sol-
vents, and as well as others. Because of these variables,
it is clear that the examination of a variety of substrates
and catalyst type is of important in terms of finding new
types of cycloisomerization reactions of enynes. Although
a variety of transition metals have been examined for
their ability to catalyze cycloisomerizations, the Ir-
catalyzed cycloisomerization of enynes has not been
comprehensively examined. Recently, we found that
simple transition-metal halides, such as [RuCl2(CO)3]2
and PtCl2, serve as effective catalysts for the skeletal
reorganization of enynes to 1-vinylcycloalkenes in high
product yields and a high selectivity (>98% isomeric
purity in all cases).9a,b,10 A characteristic feature of these
catalytic systems is that they can be used with the enynes
having a terminal acetylenic moiety. The latter are not
suitable substrates for the other catalytic systems re-
ported to date.8 In the case of Ru(II) and Pt(II) catalyst
systems, only skeletal reorganization occurred, and other
types of cycloisomerization were not detected. In contrast,
it was found that the reaction pattern for the Ir(I)-
catalyzed reaction of enynes depends on both the struc-
ture of substrates and the nature of catalyst systems
used. We wish to report herein on the Ir-catalyzed
cycloisomerization of 1,6- and 1,7-enynes.
The reaction of 1,6-enyne 1 was carried out under both
CO and N2, because we had previously observed that the
presence of a CO ligand on the metal in the Ru(II)-
catalyzed reaction appears to be effective in allowing the
reaction to proceed.9a The treatment of 1,6-enyne 1 with
4 mol % [IrCl(CO)3]n in toluene at 80 °C under an
atmosphere of CO gave a skeletal reorganization product,
3-ethenyl-3-cyclopentene-1,1-dicarboxylic acid diethyl es-
ter (2), in 50% isolated yield (eq 1). The reaction was slow,
and 2 days were required to complete the reaction. No
byproducts were detected by GC and NMR, although the
starting substrate 1 was completely consumed.11 The
reaction was more effective when conducted in an atmo-
† Present address: Graduate School of Materials Science, Nara
Institute of Science and Technology (NAIST), Takayama, Ikoma, Nara
630-0101, J apan.
(1) For recent reviews on transition-metal-catalyzed cyclization,
see: Schore, N. E. Chem. Rev. 1988, 88, 1081. Lautens, M.; Klute, W.;
Tam, W. Chem. Rev. 1996, 96, 49. Ojima, I.; Tzamarioudaki, M.; Li,
Z.; Donovan, R. J . Chem. Rev. 1996, 96, 635.
(2) A recent review on cycloisomerization of enynes, see: Trost, B.
M.; Krische, M. J . Synlett 1998, 1.
(3) Pd: Trost, B. M.; Lautens, M. J . Am. Chem. Soc. 1985, 107, 1781.
Trost, B. M.; Lautens, M. Tetrahedron Lett. 1985, 26, 4887. Trost, B.
M.; Chen, S.-F. J . Am. Chem. Soc. 1986, 108, 6053. Trost, B. M.; Tour,
J . M. J . Am. Chem. Soc. 1987, 109, 5268. Trost, B. M.; Lautens, M.;
Chan, C.; J ebaratnam, D. S.; Mueller, T. J . Am. Chem. Soc. 1991, 113,
636. Trost, B. M.; Gelling, O. J . Tetrahedron Lett. 1993, 34, 8233.
Wartenberg, F.-H.; Hellendahl, B.; Blechert, S. Synlett 1993, 539. Trost,
B. M.; Czeskis, B. A. Tetrahedron Lett. 1994, 35, 211. Co: Kraft, M.
E.; Wilson, A. M.; Dasse, O. A.; Bonaga, L. V. R.; Cheung, Y. Y.; Fu,
Z.; Shao, B.; Scott, I. L. Tetrahedron Lett. 1998, 39, 5911. Ti: Sturla,
S. J .; Kablaoui, N. M.; Buchwald, S. L. J . Am. Chem. Soc. 1999, 121,
1976. Ru: Trost, B. M.; Toste, F. D. J . Am. Chem. Soc. 2000, 122, 714.
Paih, J . L.; Rodr´ıguez, D. C.; De´rien, S.; Dixneuf, P. H. Synlett 2000,
95. Nishida, M.; Adachi, N.; Onozuka, K.; Matsumura, H.; Mori, M. J .
Org. Chem. 1998, 63, 9158. Rh: Cao, P.; Wang, B.; Zhang, X. J . Am.
Chem. Soc. 2000, 122, 6490. Cao, P.; Zhang, X. Angew. Chem., Int.
Ed. Engl. 2000, 39, 4104.
(4) Trost, B. M.; Yanai, M.; Hoogsteen, K. J . Am. Chem. Soc. 1993,
115, 5294.
(5) (a) Blum, J .; Beer-Kraft, H.; Badrieh, Y. J . Org. Chem. 1995,
60, 5567. (b) Borodkin, V. S.; Shpiro, N. A.; Azov, V. A.; Kochetkov, N.
K. Tetrahedron Lett. 1996, 37, 1489. (c) Fu¨rstner, A.; Szillat, H.;
Stelzer, F. J . Am. Chem. Soc. 2000, 122, 6785.
(6) Trost, B. M.; Toste, F. D. J . Am. Chem. Soc. 1999, 121, 9728.
(7) Kagoshima, H.; Hayashi, M.; Hashimoto, Y.; Saigo, K. Organo-
metallics 1996, 15, 5439.
(9) (a) Chatani, N.; Morimoto, T.; Muto, T.; Murai, S. J . Am. Chem.
Soc. 1994, 116, 6049. (b) Chatani, N.; Furukawa, N.; Sakurai, H.;
Murai, S. Organometallics 1996, 15, 901. (c) Chatani, N.; Kataoka,
K.; Murai, S.; Furukawa, N.; Seki, Y. J . Am. Chem. Soc. 1998, 120,
9104.
(10) Recently, Fu¨rstner and Trost utilized our catalytic system for
total synthesis. Fu¨rstner, A.; Szillat, H.; Gabor, B.; Mynott, R. J . Am.
Chem. Soc. 1998, 120, 8305. Trost, B. M.; Doherty, G. A. J . Am. Chem.
Soc. 2000, 122, 3801.
(8) Pd: (a) Trost, B. M.; Tanoury, G. J . J . Am. Chem. Soc. 1988,
110, 1636. (b) Trost, B. M.; Trost, M. K. Tetrahedron Lett. 1991, 32,
3647. (c) Trost, B. M.; Trost, M. K. J . Am. Chem. Soc. 1991, 113, 1850.
(d) Trost, B. M.; Chang, V. K. Synthesis 1993, 824. W: Katz, T. J .;
Sivavec, T. M. J . Am. Chem. Soc. 1985, 107, 737. Cr: Watanuki, S.;
Ochifuji, N.; Mori, M. Organometallics 1994, 13, 4129. Ru: Kinoshita,
A.; Mori, M. Synlett 1994, 1020. Mori, M.; Sakakibara, N.; Kinoshita,
A. J . Org. Chem. 1998, 63, 6082. Mori, M.; Kitamura, T.; Sakakibara,
N.; Sato, Y. Org. Lett. 2000, 2, 543. Ackermann, L.; Bruneau, C.;
Dixneuf, P. H. Synlett 2001, 397. Pt: See ref 5c.
(11) Small amounts of insoluble polymeric materials are formed in
some cases, causing incomplete material balances.
10.1021/jo010091y CCC: $20.00 © 2001 American Chemical Society
Published on Web 05/11/2001