1714
M. E. Dudley et al.
SPECIAL TOPIC
3-Ethoxycarbonylnaphthofuran (2e)
References
The title compound was isolated in quantitative (1.41 g) yield from
2-hydroxy-1-naphthaldehyde (1.01 g, 5.87 mmol) and ethyl diazo-
acetate solution (8%; 11.1 mL, 9.39 mmol) in the presence of
HBF4·OEt2 (54%; 0.080 mL, 0.59 mmol).
(1) (a) The Chemistry of Heterocyclic Compounds:
Benzofurans; Weissberger, A.; Taylor, E. C., Eds.; John
Wiley and Sons: New York, 1974, Vol. 29. (b) Boyle, E.
A.; Morgan, F. R.; Markwell, R. E.; Smith, S. A.; Thomson,
M. J.; Ward, R. W.; Wyman, P. A. J. Med. Chem. 1986, 29,
894. (c) Pieters, L.; Van Dyck, S.; Gao, M.; Bai, R.; Hamel,
E.; Vlietinck, A.; Lemiere, G. J. Med. Chem. 1999, 42,
5475. (d) Ma, C.-Y.; Liu, W. K.; Che, C.-T. J. Nat. Prod.
2002, 65, 206. (e) Baxendale, I. R.; Griffiths-Jones, C. M.;
Ley, S. V.; Tranmer, G. K. Synlett 2006, 427.
(2) (a) Liao, Y.; Reitman, M.; Zhang, Y.; Fathi, R.; Yang, Z.
Org. Lett. 2002, 4, 2607. (b) Willis, M. C.; Taylor, D.;
Gillmore, A. T. Org. Lett. 2004, 6, 4755. (c) Lu, K.; Luo,
T.; Xiang, Z.; You, Z.; Fathi, R.; Chen, J.; Yang, Z. J. Comb.
Chem. 2005, 7, 958. (d) Nan, Y.; Miao, H.; Yang, Z. Org.
Lett. 2000, 2, 297.
1H NMR (CDCl3, 300 MHz): d = 9.52 (d, J = 8.42 Hz, 1 H), 8.42 (s,
1 H), 7.96 (d, J = 8.05 Hz, 1 H), 7.82 (d, J = 8.96 Hz, 1 H), 7.69 (m,
2 H), 7.56 (m, 1 H), 4.48 (q, J = 7.14 Hz, 2 H), 1.48 (t, J = 7.14 Hz,
3 H).
13C NMR (CDCl3, 75.5 MHz): d = 163.60, 153.85, 151.05, 131.15,
128.50, 128.05, 127.30, 126.70, 126.60, 125.05, 119.25, 116.70,
112.05, 60.75, 14.30.
NMR Study of Ethyl Diazoacetate with 0.1 equiv HBF4·OEt2
and Salicylaldehyde
Salicylaldehyde (0.215 mL, 2.04 mmol), HBF4·OEt2 (0.015 mL,
0.20 mmol), CDCl3 (0.250 mL), and ethyl diazoacetate (0.275 mL,
2.45 mmol) were cautiously mixed in a 5-mm NMR tube. The mix-
ture was allowed to evolve N2 overnight in the freezer. After warm-
ing to r.t., several NMR spectra (1H, 13C, COSY, HSQC, and
(3) Oftedahl, M. L.; Baker, J. W.; Dietrich, M. W. J. Org. Chem.
1965, 30, 296.
(4) Dudley, M. E.; Morshed, M. M.; Brennan, C. L.; Islam, M.
S.; Ahmad, M. S.; Atuu, M. R.; Branstetter, B.; Hossain, M.
M. J. Org. Chem. 2004, 69, 7599.
1
HMBC) were recorded. The H NMR spectrum revealed the pres-
ence of roughly 3% of 3-hydroxyacrylate (8), 5% of benzofuran 3-
ethyl ester (2a) and 90% of the hemiacetal 9, which was assigned
according to the ring numbering in Figure 2a.
(5) Rabjohn, N. Org. Synth. Coll. Vol. IV; John Wiley and Sons:
New York, 1963, 424.
3-Ethoxycarbonyl-2-hydroxy-2,3-dihydrobenzofuran (9)
1H NMR (CDCl3, 300 MHz): d = 7.30 (d, J = 7.32 Hz, 1 H, H-4),
7.10 (m, 1 H, H-6), 6.85 (m, 1 H, H-5), 6.80 (d, J = 7.87 Hz, 1 H,
H-7), 6.30 (s, 1 H, H-2), 5.40 (d, J = 4.94 Hz, 1 H, OH), 4.10 (q,
J = 7.14 Hz, 2 H, CH2), 4.00 (d, J = 7.14 Hz, 1 H, H-3), 1.20 (t,
J = 2.38 Hz, 3 H, CH3).
13C NMR (CDCl3, 75.5 MHz): d = 169.8 (C=O), 157.6 (C-8), 129.4
(C-6), 125.4 (C-4), 123.0 (C-9), 121.0 (C-5), 109.8 (C-7), 102.5 (C-
2), 61.7 (CH2), 55.0 (C-3), 14.1 (CH3).
Synthesis 2006, No. 10, 1711–1714 © Thieme Stuttgart · New York