Rev., 1987, 16, 187–238; (d) E. Ciganek, Org. React., 1984, 32, 1–374;
(e) G. Brieger and J. N. Bennett, Chem. Rev., 1980, 80, 63–97.
2 (a) P. Kim, M. H. Nantz, M. J. Kurth and M. M. Olmstead, Org. Lett.,
2000, 2, 1831–1834; (b) M. E. Jung, A. Huang and T. W. Johnson,
Org. Lett., 2000, 2, 1835–1837; (c) E. L. Pearson, L. C. H. Kwan,
C. I. Turner, G. A. Jones, A. C. Willis, M. N. Paddon-Row and M. S.
Sherburn, J. Org. Chem., 2006, 71, 6099–6109; (d) S. Inoue, C. Yin, H.
Kosugi, A. Nabeta, Y. Sakai, K. Honda and Y. Hoshino, Bull. Chem.
Soc. Jpn., 2008, 81, 1308–1314.
3 D. J. Tantillo, K. N. Houk and M. E. Jung, J. Org. Chem., 2001, 66,
1938–1940.
4 S. F. Martin, S. A. Williamson, R. P. Gist and K. M. Smith, J. Org.
Chem., 1983, 48, 5170–5180.
Scheme 2
5 For a review on conformation and stereoelectronic effect of ester
compounds, see: P. Deslongchamps, In Stereoelectronic Effects in
Organic Chemistry, Pergamon, Oxford, 1983, pp. 54–100.
6 (a) D. Cain, D. M. Pawar, M. Stewart, H. Billings, Jr. and E. A. Noe,
J. Org. Chem., 2001, 66, 6092–6095; (b) T. Uchimaru, S. Tsuzuki, M.
Sugie and A. Sekiya, Chem. Phys. Lett., 2003, 373, 182–190.
7 For a review, see: T. Taguchi, A. Saito and H. Yanai, Chem. Rec., 2007,
7, 167–179.
8 (a) A. Saito, H. Ito and T. Taguchi, Org. Lett., 2002, 4, 4619–4621;
(b) A. Saito, H. Yanai and T. Taguchi, Tetrahedron, 2004, 60, 12239–
12247; (c) A. Saito, H. Yanai, W. Sakamoto, K. Takahashi and T.
Taguchi, J. Fluorine Chem., 2005, 126, 709–714; (d) A. Saito, W.
Sakamoto, H. Yanai and T. Taguchi, Tetrahedron Lett., 2006, 47, 4181–
4185.
resulted in poor conversion of 1i and the desired cycloadduct 2i
was obtained in only 14% yield.15 Under similar conditions, the
reaction of 1i in water gave 2i in a moderate yield with a competitive
intermolecular DA reaction due to the low solubility of 1i in pure
water.16
Regarding the present rate acceleration of the IMDA reaction of
ester-tethered 1,3,9-decatrienes, we propose that the solvent effects
by imidazolium-based ILs attributed to both the conformational
behavior of ester functionality and the kinetic acceleration in the
C–C bond forming process. In the intermolecular DA reaction
of methyl acrylate with cyclopentadiene, rate constant k is pro-
portional to solvent parameters such as dipolarity/polarizability
p* and hydrogen bond donor acidity a.17 Likewise, these solvent
effects possibly influence the rate of the IMDA reaction of dienyl
acrylates. However, since k of intermolecular DA reaction in
[bmim]BF4 is only two fold larger than that in acetonitrile14, the
observed rate acceleration in the IMDA reaction is not considered
just a simple kinetic acceleration in the C–C bond forming step by
ILs. For the rational explanation for the significant acceleration in
the present IMDA reaction, we propose some alternative factors
such as the conformational control of ester functionality by
ILs. That is, since the p* values of ILs are notably higher than
those of organic solvents such as acetonitrile and toluene, the
repulsive dipole interaction between the two oxygen atoms in ester
functionality should relax to form the cisoid form. In addition,
the microviscosity of ILs should control the conformation of the
ester and diene parts to stabilize the transition state.10
In summary, we found that the IMDA reaction of ester tethered
1,3,9-decatrienes can be significantly accelerated in imidazolium-
based ILs such as [emim]BF4, [bmim]BF4 and [bdmim]BF4. It is
well known that the IMDA reaction of ester tethered substrates in
several organic solvents requires both a high reaction temperature
and a long reaction time to obtain the cycloadducts in a reasonable
yield. The present reaction in ILs realized the highly diastereose-
lective construction of a cis-fused bicyclic lactone structure under
mild conditions. In addition, since the reaction in ILs did not
require the use of any Lewis acidic metal complexes and the ILs
used can be recycled after the removal of volatile residue simply
under reduced pressure, the present conditions are greener than
the previous conditions reported by our research group.
9 H. Yanai, A. Saito and T. Taguchi, Tetrahedron, 2005, 61, 7087–
7093.
10 S. Tiwari, N. Khupse and A. Kumar, J. Org. Chem., 2008, 73, 9075–
9083.
11 (a) Ionic Liquids in Synthesis, P. Wasserscheid, and T. Welton, Eds.,
Wiley-VCH, Weinheim, Germany, 2008, 2nd edition.; (b) T. Welton,
Chem. Rev., 1999, 99, 2071–2083; (c) H. Zhao and S. V. Malhotra,
Aldrichimica Acta, 2002, 35, 75–83; (d) N. Jain, A. Kumar, S. Chauhan
and S. M. S. Chauhan, Tetrahedron, 2005, 61, 1015–1060; (e) M. A. P.
Martins, C. P. Frizzo, D. N. Moreira, N. Zanatta and H. G. Bonacorso,
Chem. Rev., 2008, 108, 2015–2050; (f) N. V. Plechkova and K. R.
Seddon, Chem. Soc. Rev., 2008, 37, 123–150; (g) B. Wu, B., W. Liu,
Y. M. Zhang and H. Wang, Chem.–Eur. J., 2009, 15, 1804–1810.
12 (a) For examples of the inverse electron demand hetero-IMDA reac-
tions in ILs, see: J. S. Yadav, B. V. S. Reddy, L. Chetia, G. Srinivasulu
and A. C. Kunwar, Tetrahedron Lett., 2005, 46, 1039–1044; (b) J. S.
Yadav, B. V. Subba Reddy, G. Kondaji, S. Sowjanya and K. Nagaiah,
J. Mol. Catal. A: Chem., 2006, 258, 361–366.
13 (a) For selected examples of intermolecular DA reaction in ILs, see.D. A.
Jaeger and C. E. Tucker, Tetrahedron Lett., 1989, 30, 1785–1788; (b) J.
Howarth, K. Hanlon and P. B. McCormac, Tetrahedron Lett., 1997,
38, 3097–3100; (c) M. J. Earle, P. B. McCormac and K. R. Seddon,
Green Chem., 1999, 1, 23–25; (d) T. Fischer, A. Sethi, T. Welton and J.
Woolf, Tetrahedron Lett., 1999, 40, 793–796; (e) C. W. Lee, Tetrahedron
Lett., 1999, 40, 2461–2464; (f) C. E. Song, W. H. Shim, E. J. Roh and
J. H. Choi, Chem. Commun., 2000, 1695–1696; (g) A. P. Abbott, G.
Capper, D. L. Davies, R. K. Rasheed and V. Tambyrajah, Green Chem.,
2002, 4, 24–26; (h) A. Kumar and S. S. Pawar, J. Org. Chem., 2004, 69,
1419–1420; (i) S. Tiwari and A. Kumar, Angew. Chem., Int. Ed., 2006,
45, 4824–4825.
14 (a) R. Bini, C. Chiappe, V. L. Mestre, C. S. Pomellic and T. Welton, Org.
Biomol. Chem., 2008, 6, 2522–2529; (b) A. Aggarwal, N. L. Lancaster,
A. R. Sethi and T. Welton, Green Chem., 2002, 4, 517–520.
15 It has been reported that the thermal IMDA reactions of structurally
similar methyl fumarate derivatives in organic solvents required more
harsh conditions to obtain the DA product (xylene, reflux, 5 h or
toluene, 110 ◦C, 22 h), see: C.-Y. Chen and D. J. Hart, J. Org. Chem.,
1993, 58, 3840–3849; and ref. 2c.
16 (a) S. Narayan, S., V. V. Fokin, K. B. Sharpless, Chemistry ‘on water’–
organic synthesis in aqueous suspension, In Organic Reactions in Water,
U. M. Lindstroem, Ed., Blackwell Publishing, Oxford, UK, 2007,
pp. 350–365; (b) S. Narayan, J. Muldoon, M. G. Finn, V. V. Fokin,
H. C. Kolb and K. B. Sharpless, Angew. Chem., Int. Ed., 2005, 44, 3275–
3279.
References
1 (a) For reviews on IMDA reaction, see: K. Takao, R. Munakata and
K. Tadano, Chem. Rev., 2005, 105, 4779–4807; (b) W. R. Roush, In
Comprehensive Organic Synthesis, B. M. Trost, and I. Fleming, Eds.,
Pergamon, Oxford, UK, 1991, Vol. 2, pp. 513; (c) D. Craig, Chem. Soc.
17 L. Crowhurst, P. R. Mawdsley, J. M. Perez-Arlandis, P. A. Salter and
T. Welton, Phys. Chem. Chem. Phys., 2003, 5, 2790–2794.
This journal is
The Royal Society of Chemistry 2009
Org. Biomol. Chem., 2009, 7, 3657–3659 | 3659
©