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S. Nagumo et al. / Tetrahedron Letters 50 (2009) 26–28
COOMe
COOMe
O
References and notes
BF Et O
O
3
2
1. Nagumo, S.; Miyoshi, I.; Akita, H.; Kawahara, N. Tetrahedron Lett. 2002, 43,
2223.
o
OH
-30 C
MeO
2. Nagumo, S.; Mizukami, M.; Wada, K.; Miura, T.; Bando, H.; Kawahara, N.;
Hashimoto, Y.; Miyashita, M.; Akita, H. Tetrahedron Lett. 2007, 48, 8558.
3. Mizukami, M.; Saito, H.; Higuchi, T.; Imai, M.; Bando, H.; Kawahara, N.;
Nagumo, S. Tetrahedron Lett. 2007, 48, 7228.
50%
15
16
4. For representative examples: (a) Jamison, T. F.; Shambayati, S.; Crowe, W. E.;
Schreiber, S. L. J. Am. Chem. Soc. 1997, 119, 4353; (b) Iwasawa, N.; Satoh, H. J.
Am. Chem. Soc. 1999, 121, 7951; (c) Takai, S.; Isobe, M. Org. Lett. 2002, 4, 1183;
(d) Tanino, K.; Kondo, F.; Shimizu, T.; Miyashita, M. Org. Lett. 2002, 4, 2217; (e)
Kira, K.; Hamajima, A.; Isobe, M. Tetrahedron 2002, 58, 1875; (f) Teobald, B. J.
Tetrahedron 2002, 58, 4133; (g) Tanino, K.; Onuki, K.; Asano, K.; Miyashita, M.;
Nakamura, T.; Takahashi, Y.; Kuwajima, I. J. Am. Chem. Soc. 2003, 125, 1498; (h)
Young, D. G. J.; Burlison, J. A.; Peters, J. J. Org. Chem. 2003, 68, 3494; (i) Baba, T.;
Takai, S.; Sawada, N.; Isobe, M. Synlett 2004, 603; (j) Ortega, N.; Martin, T.;
Martin, V. S. Org. Lett. 2006, 8, 871; (k) DiMartino, J.; Green, J. R. Tetra-
hedron 2006, 62, 1402; (l) Inaba, K.; Takaya, J.; Iwasawa, N. Chem. Lett. 2007, 36,
474 references cited therein. See also: (m) Yet, L. Chem. Rev. 2000, 100,
2963.
Scheme 5.
MeOOC
MeO
CAN
CH2Cl2
OH
MeOOC
MeO
MeO
OH
O
O
O
5. (a) Nagasawa, T.; Kitamura, M.; Suzuki, K. Synlett 1995, 1183; (b) Kitamura, M.;
Ohmori, K.; Suzuki, K. Tetrahedron Lett. 1999, 40, 4563. For ene reaction of
Co2(CO)6-complexed eneyne, see also: (c) Mikami, K.; Feng, F.; Matsueda, H.;
Yoshida, A.; Grierson, D. S. Synlett 1996, 833.
17
MeO
MeOOC
MeO
6. All newly synthesized compounds gave spectroscopic data in agreement with
the assigned structures. Representative data are shown below. Compound 9e: IR
(CHCl3) 3468, 2092, 2036, 1717 cmꢁ1; Anal. Calcd for C24H20O11Co2: C, 47.86;
H, 3.35. Found: C, 47.57; H, 3.49; 1H NMR (400 MHz, CDCl3) d 7.81 (dd, J = 16.0,
8.3 Hz, 1H), 6.78 (d, J = 2.0 Hz, 1H), 6.41 (d, J = 2.0 Hz, 1H), 5.76 (d, J = 16.0 Hz,
1H), 4.37 (dd, J = 10.7, 2.4 Hz), 3.81 (s, 3H), 3.80 (s, 3H), 3.77 (m, 1H), 3.70 (s,
3H), 3,50 (dd, J = 18.0, 11.0 Hz, 1H), 3.20 (dd, J = 18.0, 6.3 Hz, 1H), 1.96 (ddd,
J = 14.0, 6.3, 2.4 Hz, 1H), 1.84 (d, J = 2.4 Hz, 1H), 1.80 (d, J = 14.0 Hz, 1H); 13C
NMR (100 MHz, CDCl3) d 199.64 (s), 167.09 (s), 159.84 (s), 158.27 (s), 150.55
(d), 139.66 (s), 121.85 (d), 119.89 (s), 110.44 (d), 102.59 (s), 99.60 (d), 92.07 (s),
71.08 (d), 55.67 (q), 55.34 (q), 51.41 (q), 48.33 (d), 33.44 (t), 28.86 (t).
Compound 17: IR (CHCl3) 3486, 1769, 1736 cmꢁ1; EI-MS m/z 388 (M+); HR-MS
m/z 388.1146 (Calcd for C20H20O8: 388.1157); 1H NMR (400 MHz, CDCl3) d 7.68
(dd, J = 16.1, 7.8 Hz, 1H), 6.68 (s, 1H), 6.57 (s, 1H), 5.83 (d, J = 16.1 Hz, 1H), 4.29
(d, J = 10.3 Hz, 1H), 3.83 (s, 3H), 3.81 (s, 3H), 3.71 (s, 3H), 3.59 (dd, J = 10.3,
7.8 Hz, 1H), 3.16 (m, 1H), 2.64 (m, 1H), 2.13 (br s, 1H), 1.87–1.73 (m, 2H); 13C
NMR (100 MHz, CDCl3) d 166.98 (s), 165.4 (s), 164.85 (s), 159.62 (s), 158.47 (s),
149.01 (d), 145.45 (s), 137.79 (s), 128.53 (s), 123.03 (d), 120.56 (s), 106.47 (d),
102.25 (d), 68.50 (d), 55.78 (q), 55.63 (q), 51.54 (q), 48.24 (d), 27.05 (t), 20.91
(t). Compound 18: IR (CHCl3) 3482, 1717 cmꢁ1; EI-MS m/z 318 (M+); HR-MS m/z
318.1479 (Calcd for C18H22O5: 318.1466); 1H NMR (400 MHz, CDCl3) d 7.77 (dd,
J = 15.9, 10.0 Hz, 1H), 6.47–6.30 (m, 2H), 6.32 (s, 1H), 6.31 (m, 1H), 5.84 (d,
J = 15.9 Hz, 1H), 4.21 (d, J = 10.0 Hz, 1H), 4.07 (t, J = 10.0 Hz, 1H), 3.77 (s, 3H),
3.75 (s, 3H), 3.70 (s, 3H), 2.68 (d, J = 15.0 Hz, 1H), 2.29–2.13 (m, 2H), 1.73 (t,
J = 15.0 Hz, 1H), 1.50 (br d, J = 15.0 Hz, 1H); 13C NMR (100 MHz, CDCl3) d 167.30
(s), 158.84 (s), 158.18 (s), 151.59 (d), 139.45 (s), 134.53 (d), 126.84 (d), 121.61
(d), 119.26 (s), 105.02 (d), 98.23 (d), 69.63 (d), 55.39 (q), 55.18 (q), 51.24 (q),
48.10 (d), 29.09 (t), 24.80 (t).
(OC)3Co Co(CO)3
OH
9e
Bu3SnH
toluene, 70°C
MeO
18
Scheme 6.
the ortho position of the benzene ring by stabilizing the developing
positive charge at the ipso position. Such a property of the complex
may prevent the ipso-cyclization of 8b. However, activation by the
cobalt complex is not strong enough to induce cyclization of an
eight-membered ring at the ortho position with an endo mode.
The methoxy group at the C30 position on the benzene ring is
essential for the eight-membered cyclization. Decomplexation
was performed under either oxidizing or reducing conditions.
Treatment of cyclic molecule 9e with ceric ammonium nitrate
afforded 176 in 72% yield.12 On the other hand, 9e was transformed
into poly-functional cyclooctene 18 in high yields upon treatment
with tributyltin hydride in toluene at 70 °C (Scheme 6).13
In conclusion, a novel route for constructing poly-functional
eight-membered carbocycles was developed based on the endo-
selective Friedel–Crafts reaction of vinyloxiranes with Co2(CO)6-
complexed benzeneacetylene. The cyclization showed high stere-
oselectivity and regioselectivity for the opening of the epoxide.
Furthermore, decomplexation of the cyclization product proceeded
smoothly. The present reaction is expected to provide a useful
method for the synthesis of natural products with eight-membered
carbocycles.
7. Sonogashira, K.; Tohda, Y.; Hagihara, N. Tetrahedron Lett. 1975, 50, 4467.
8. The meta methoxy group to the reacting site generally exerts an electron-
withdrawing inductive effect. It was thus interesting that the cyclization of 8d
proceeded smoothly in spite of the presence of the methoxy group at the
C40 position.
A
previously reported 7-endo cyclization of 30,40-dimethoxy-
phenylpropyl vinyloxirane (see Ref. 1) can be explained to proceed via an ipso-
cyclization and the subsequent migration. Such mechanism might be
a
inadequate in the case of 8d because the neighbouring effect of the cobalt
complex might inhibit an ipso-cyclization.
9. These vinyloxiranes were prepared as optically active compounds.
10. A previously reported 7-endo cyclization of 30-methoxyphenylpropyl vinyl-
oxirane having no adjacent ester group yielded a mixture of stereoisomers (see
Ref. 1). However, the corresponding vinyloxirane having an adjacent ester
group proceeded stereospecifically to give only trans-isomer.
11. Unpublished data.
Acknowledgement
12. Tanino, K.; Shimizu, T.; Miyashita, M.; Kuwajima, I. J. Am. Chem. Soc. 2000, 122,
6116.
13. Hosokawa, S.; Isobe, M. Tetrahedron Lett. 1998, 39, 2609.
This work was supported by a Grant-in Aid for Scientific
Research (C) (15590017 to S.N.).