Highly Alkoxy-Substituted Naphthaldehyde Derivatives
FULL PAPER
cm–1. MS (EI = 80 eV, 40 °C): m/z (%) = 498 (32) [M]+, 380 (21), was added to a solution of crude compound 7a (117 mg, max.
379 (100), 293 (24), 263 (12), 115 (5) [C6H11O2]+, 91 (17) [C7H7]+. 0.22 mmol) and diisopropylethylamine (0.11 mL, 0.64 mmol) in
HRMS (EI = 80 eV, 40 °C): calcd. for C28H34O8 498.22537; found DMF (3 mL). The mixture was stirred at room temp. for 6 h,
498.22477.
quenched with satd. aq. Na2CO3 solution (10 mL) and extracted
with diethyl ether (3×15 mL). The combined organic layers were
dried with MgSO4 and filtered, and the solvent was removed under
reduced pressure. Chromatography on silica gel (hexane/ethyl ace-
tate, 4:1) afforded 7b (82 mg, 64 %) as a yellow oil. 1H NMR
(500 MHz, CDCl3): δ = 0.59, 0.82 [q, t, J = 8.0 Hz, 6 H, 9 H,
OSi(CH2CH3)3], 3.81, 3.853, 3.855, 3.94, 3.99 (5 ×s, 3 H each,
OCH3), 5.13, 5.35 (AB system, JAB = 10.8 Hz, 2 H, OCH2Ph), 5.51
(dd, J = 2.1, 10.5 Hz, 1 H, 4-H), 5.59 (s, 1 H, 1-H), 6.25 (dd, J =
2.1, 17.4 Hz, 1 H, 4-H), 6.66 (s, 1 H, Ar), 6.88 (dd, J = 10.5, 17.4
Hz, 1 H, 3-H), 7.29–7.33, 7.35–7.38, 7.48–7.51 (3 m, 1 H, 2 H,
2 H, Ph) ppm. 13C NMR (126 MHz, CDCl3): δ = 4.8, 6.8 [q, t,
OSi(CH2CH3)3], 56.8, 57.2, 61.9, 62.0, 63.9 (5×q, OCH3), 72.6 (d,
C-1), 75.8 (t, OCH2Ph), 96.6 (d, Ar), 114.7, 126.6, 127.08 (3×s,
Ar), 127.1 (t, C-4), 127.9, 128.37, 128.41 (3×d, Ph), 131.6 (d, C-
3), 136.8, 138.0, 143.7, 148.9, 150.4, 151.9, 153.7 (7×s, Ph, Ar),
2-(3-Benzyloxy-1,4,5,8-tetramethoxynaphthalen-2-yl)-5,5-dimethyl-
1,3-dioxane (46): 1H NMR (270 MHz, CDCl3): δ = 0.75, 1.24 (2×s,
3 H each, CH3), 3.59, 3.77 (2×d, J = 11.6 Hz, 2 H each, OCH2),
3.83, 3.88, 3.92, 3.94 (4 × s, 3 H each, OCH3), 5.20 (s, 2 H,
OCH2Ph), 6.03 (s, 1 H, 2Ј-H), 6.73, 6.81 (2×d, J = 8.5 Hz, 1 H
each, Ar), 7.31–7.42, 7.57 (m, mc, 3 H, 2 H, Ph) ppm.
3-Benzyloxy-1,4,5,6,8-pentamethoxynaphthalene-2-carbaldehyde
(8b): Compound 45 (104 mg, 0.21 mmol) was dissolved in acetic
acid (5 mL, 80%) and stirred at room temp. for 4 h. The mixture
was diluted with water and extracted with diethyl ether (3×10 mL),
the combined organic layers were dried with MgSO4 and filtered,
and the solvent was removed under reduced pressure to afford
crude 8b (86 mg). After chromatography on silica gel (hexane/ethyl
acetate, 3:1), pure 8b (70 mg, 81%) was obtained as a yellow solid
(m.p. 115–118 °C). 1H NMR (500 MHz, CDCl3): δ = 3.86, 3.88,
3.90, 4.01, 4.02 (5×s, 3 H each, OCH3), 5.17 (s, 2 H, OCH2Ph),
6.68 (s, 1 H, Ar), 7.31–7.34, 7.37–7.40, 7.57–7.58 (3 m, 1 H, 2 H,
2 H, Ph), 10.48 (s, 1 H, CHO) ppm. 13C NMR (126 MHz, CDCl3):
δ = 56.7, 57.0, 62.1,* 64.8 (4×q, OCH3), 76.1 (t, OCH2Ph), 96.2
(d, Ar), 113.9, 120.7 (2× s, Ar), 128.2, 128.5, 128.9 (3 × d, Ph),
129.9, 136.7, 137.4, 144.4, 148.7, 153.1, 155.3, 158.9 (8×s, Ph, Ar),
200.4 (s, CO) ppm. IR (film): ν = 3110–3030 (=CH), 2990–2875
˜
(C–H), 2840 (OCH3), 1715, 1695 (C=O), 1605–1580 (C=C, Ar, Ph),
1500–1400 (C–H) cm–1. MS (EI = 80 eV, 100 °C): m/z (%) = 584
(13), 583 (44), 582 (97) [M]+, 529 (11), 528 (28), 527 (100), 466 (12),
465 (49), 464 (10), 407 (32), 86 (35), 84 (56), 75 (11), 73 (20), 57
(15), 51 (20), 49 (63), 44 (12), 42 (10). HRMS (EI = 80 eV, 100 °C):
calcd. for C32H42O8Si 582.26489; found 582.26555.
189.7 (d, CHO) ppm; *signal with higher intensity. IR (KBr): ν =
˜
3110–3030 (=CH), 2990–2880 (C–H), 2840 (OCH3), 1685 (C=O),
1600, 1565 (C=C, Ar, Ph), 1495–1420 (C–H) cm–1. C23H24O7
(412.4): calcd. C 66.98, H 5.87; found C 66.98, H 5.95.
Acknowledgments
The authors thank the Fonds der Chemischen Industrie (Kekulé
fellowship for S. S.) and the Schering AG for generous support of
this research. We also thank Dr. R. Zimmer for his assistance dur-
ing the preparation of this manuscript.
1-(3-Benzyloxy-1,4,5,6,8-pentamethoxynaphthalen-2-yl)-1-hydroxy-
but-3-en-2-one (7a): n-Butyllithium (0.17 mL, 2.5 in hexanes,
0.43 mmol) was added at –40 °C to a solution of methoxyallene
(60 µL, 0.72 mmol) in THF (4 mL) and the solution was stirred for
1 h. The reaction mixture was then cooled to –78 °C, a solution of
naphthaldehyde 8b (90 mg, 0.22 mmol) in THF (3 mL) was added,
and stirring was continued for an additional 4 h. The reaction mix-
ture was quenched by addition of aq. sulfuric acid (10 mL, 5%)
and allowed to warm to 0 °C over 1 h. Satd. aq. NaHCO3 solution
(10 mL) was added and the mixture was extracted with diethyl
ether (3×20 mL). The combined organic layers were washed once
with satd. aq. NaHCO3 solution (20 mL), dried with MgSO4 and
filtered, and the solvent was removed under reduced pressure to
afford 7a (117 mg, quant.) as a yellow oil. Compound 7a was used
in the next step without further purification. The analytic data were
obtained from a second experiment; chromatography on silica gel
(hexane/ethyl acetate, 2:1) afforded 7a as a yellow solid (m.p. 105–
107 °C). 1H NMR (500 MHz, CDCl3): δ = 3.79, 3.861, 3.863, 3.97,
4.00 (5×s, 3 H each, OCH3), 4.36 (d, J = 4.0 Hz, 1 H, OH), 5.16,
5.30 (AB system, JAB = 10.7 Hz, 2 H, OCH2Ph), 5.58 (dd, J = 2.3,
9.8 Hz, 1 H, 4-H), 5.71 (d, J = 4.0 Hz, 1 H, 1-H), 6.23 (dd, J =
2.3, 17.5 Hz, 1 H, 4-H), 6.29 (dd, J = 9.8, 17.5 Hz, 1 H, 3-H), 6.68
(s, 1 H, Ar), 7.31–7.34, 7.37–7.40, 7.51–7.53 (3 m, 1 H, 2 H, 2 H,
Ph) ppm. 13C NMR (126 MHz, CDCl3): δ = 56.8, 56.9, 61.97,
61.98, 63.8 (5×q, OCH3), 71.2 (d, C-1), 75.8 (t, OCH2Ph), 96.3 (d,
Ar), 114.4, 123.3, 127.3 (3×s, Ar), 128.1, 128.46, 128.54 (3×d, Ph),
129.0 (t, C-4), 131.5 (d, C-3), 136.7, 137.5, 144.0, 148.7, 150.8,
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152.1, 153.6 (7×s, Ph, Ar), 198.2 (s, CO) ppm. IR (KBr): ν = 3450
˜
(OH), 3110–3030 (=CH), 2995–2860 (C–H), 2840 (OCH3), 1705
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1-(3-Benzyloxy-1,4,5,6,8-pentamethoxynaphthalen-2-yl)-1-triethylsi-
lyloxybut-3-en-2-one (7b): Triethylsilyl chloride (50 µL, 0.47 mmol)
Eur. J. Org. Chem. 2006, 4405–4418
© 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
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