M. C. Bernabeu et al. / Tetrahedron: Asymmetry 12 (2001) 1811–1815
1815
19. Crystallographic data (excluding structure factors) for the
structure reported in this paper have been deposited with
the Cambridge Crystallographic Data Centre as supple-
mentary publication no. CCDC 166268. Copies of the
data can be obtained free of charge on application to
CCDC, 12 Union Road, Cambridge CB2 1EZ, UK [fax:
+44(0)-1223-336033 or e-mail: deposit@ccdc.cam.ac.uk].
20. Evans, D. A.; Chapman, K. T.; Bisaha, J. J. Am. Chem.
Soc. 1988, 110, 1238–1256.
21. MOPAC, CS Chem3D 4, CambridgeSoft Corporation.
22. Frisch, M. J.; Trucks, G. W.; Schlegel, H. B.; Scuseria,
G. E.; Robb, M. A.; Cheeseman, J. R.; Zakrzewski, V.
G.; Montgomery, Jr., J. A.; Stratmann, R. E.; Burant, J.
C.; Dapprich, S.; Millam, J. M.; Daniels, A. D.; Kudin,
K. D.; Strain, M. C.; Farkas, O.; Tomasi, J.; Barone, V.;
Cossi, M.; Cammi, R.; Mennucci, B.; Pomelli, C.;
Adamo, C.; Clifford, S.; Ochterski, J.; Petersson, G. A.;
Ayala, Y.; Cui, Q.; Morokuma, K.; Malick, D. K.;
Rabuck, A. D.; Raghavachari, K.; Foresman, J. B.;
Cioslowski, J.; Ortiz, J. V.; Baboul, A. G.; Stefanov, B.
B.; Liu, G.; Liashenko, A.; Piskorz, P.; Komaromi, I.;
Gomperts, R.; Martin, R. L.; Fox, D. J.; Keith, T.;
Al-Laham, M. A.; Peng, C. Y.; Nanayakkara, A.; Challa-
combe, M.; Gill, P. M. W.; Johnson, B.; Chen, W.;
Wong, M. W.; Andres, J. L.; Gonzalez, C.; Head-Gor-
don, M.; Replogle, E. S.; Pople, J. A. Gaussian 98,
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23. See for example: Birney, D. M.; Houk, K. N. J. Am.
Chem. Soc. 1990, 112, 4127–4133.
14. Metz, P.; Seng, P.; Fro¨hlich, R.; Wibbeling, B. Synlett
1996, 741–742.
15. Tsuge, H.; Nagai, T.; Okano, T.; Eguchi, S.; Kimoto, H.
Synlett 1996, 1106–1108.
16. Okano, T.; Nagai, T.; Eguchi, S.; Kimoto, H. Heterocy-
cles 1999, 50, 53–56.
17. The following synthesis of cycloadduct 10a is representa-
tive: To a solution of 8 (100 mg, 0.3 mmol) in CH2Cl2 (5
mL) under nitrogen was added EtAlCl2 (1 M solution in
hexanes, 0.3 mL, 0.3 mmol) and freshly distilled
cyclopentadiene (247 mL, 3 mmol). The mixture was
stirred at −40°C for 5 h and to the resulting solution was
added aqueous HCl (1 M, 15 mL). The mixture was
extracted with CH2Cl2 (3×20 mL) and the organics were
dried (Na2SO4) and evaporated (15 Torr), affording a
residue which was purified by flash chromatography (sil-
ica gel, hexane/AcOEt gradients) affording adduct 10a.
18. Compound 10a: White solid, mp 154–155°C. [h]2D5=−13.4
(c 1.2, CHCl3). IR (KBr) w 3063, 3032, 1771, 1337, 1145,
1
1021, 972, 830, 764, 704. H NMR (CDCl3, 300 MHz): l
1.04 (d, J=6.7 Hz, 3H), 1.40 (d, J=9 Hz, 1H), 1.59 (d,
J=9 Hz, 1H), 1.64 (ddd, J=12.2, 4.9, 2.7 Hz, 1H), 2.25
(ddd, J=12.2, 9.5, 3.7 Hz, 1H), 3.07 (m, 1H), 3.42 (m,
1H), 4.44 (ddd, J=9.5, 4.9, 3.2 Hz, 1H), 4.60 (quint.,
J=6.7 Hz, 1H), 5.72 (d, J=7.3 Hz, 1H), 6.13 (dd, J=5.5,
2.9 Hz, 1H), 6.34 (dd, J=5.5, 3 Hz, 1H), 7.27–7.46 (m,
5H). 13C NMR (CDCl3, 75 MHz): l 16.7, 29.8, 42.8,
45.3, 49.8, 57.7, 63.3, 80.1, 125.7, 128.8, 129.1, 131.4,
132.8, 138.0, 152.5. Anal calcd for C17H19NO4S: C, 61.24;
H, 5.75; N, 4.20; S, 9.60. Found: C, 60.98; H, 5.71; N,
4.12; S, 9.40%.
24. The zero-point energies were obtained at HF/3-21G and
were scaled by a factor of 0.94 (Scott, A. P.; Radom, L.
J. Phys. Chem. 1996, 100, 16502–16513).