Article
Cui and Li
76%, 36 mmol). The reaction proceeded at 10 °C under vigorous
stirring during 5 h and the color of the reaction mixture gradually
turned from red-brown to yellow-orange. The yellow-orange
solid as the crude product was collected by filtration and was
carefully washed with cold water (30 mL). Then it was digested in
hot MeOH (35 mL) and filtered hot. Pure 10 as tiny orange crys-
tals could precipitate in the filtrate that was cooled in a salt-ice
bath to -15 °C and were collected by filtration. The mother liquid
was used for the recrystallization of the residue (the crude prod-
uct) for two times to give two-fifth of the product. Yield: 1.61 g
(68%). The quinone turned dark at 130-136 °C (dec.) (ref.26 mp
166 °C). Its spectral data were in accordance with the reported
values.26 IR (KBr): 3066w, 1670vs (C=O), 1577s, 1278s. 1H NMR
((D6)DMSO): 7.89 (d, J = 1.5, H-C(5)); 7.83 (d, J = 8.1, H-C(8));
7.76 (dd, J = 8.1, 1.5, H-C(7)); 7.61 (d, J = 10.2, H-C(4)); 6.46 (d,
J = 10.2, H-C(3)); 13C NMR ((D6)DMSO): 179.8, 177.4 (C(1),
C(2)); 142.7, 132.9, 132.3, 130.3 129.2 (5 Cnaph.H, C(3), C(4),
C(5), C(7), C(8)); 136.4, 130.7, 129.1 (3 Cnaph., quat., C(6), C(4a),
C(8a)).
cooled in a water-ice bath, a solution of tetrabutyl ammonium
bromide (2.25 g, 7 mmol) and sodium dithionite (8.70 g, 50
mmol) in water (15 mL) was added. Then NaOH (2.80 g, 70
mmol) in water (5 mL) and dimethyl sulfate (3.78 g, 30 mmol)
were added dropwise in turns during 5 min under nitrogen atmo-
sphere. After the addition, the stirring was continued for about 5
h. Then the organic layer was separated and the aqueous phase
was extracted with AcOEt and the combined organic layer was
washed with a saturated NaHCO3 solution and brine, dried over
Na2SO4 and concentrated under reduced pressure. The obtained
residue was purified by CC (PE/AcOEt 10:1) to give 7 or 11 as
colorless plates.
1,2-Dimethoxy-5-(methoxymethyloxy)naphthalene (7).
Yield: 1.61 g (65%). mp 69-71 °C (PE). IR (KBr): 2963w, 2941w,
1
1600m, 1508m, 1274vs, 1161vs, 1189vs, 1031vs (C-O-C). H
NMR ((D6)DMSO): 7.94 (d, J = 9.3, H-C(4)); 7.62 (d, J = 8.4,
H-C(8)); 7.44 (d, J = 9.3, H-C(3)); 7.38 (m, 1H, H-C(7)); 6.96 (d,
J = 7.5, H-C(6)); 5.39 (s, 2H, CH2O); 3.93, 3.86 (each s, 3H,
CH3O-Cnaph.); 3.44 (s, 3H, CH3O). 13C NMR ((D6)DMSO): 152.4,
148.5, 141.8, 129.7, 121.2 (5 Cnaph., quat., C(1), C(2), C(5), C(4a),
C(8a)); 126.4, 117.9, 114.6, 113.9, 105.9 (5 Cnaph.H, C(3), C(4),
C(6), C(7), C(8)); 94.2 (CH2O); 60.5, 56.4 (2 CH3O-Cnaph.); 55.8
(CH3O). HRMS: Calc. for C14H15O4 247.0970; found 247.0992
[M-H]-.
5-Methoxymethyloxy-1,2-naphthoquinone (6). Com-
pound 5 (1.74 g, 10 mmol) was suspended in dry CH2Cl2 (20 mL)
and the mixture was cooled in a water-ice bath under nitrogen at-
mosphere. After the addition of N,N-diisopropylethylamine
(DIEA, 1.94 g, 15 mmol), freshly distilled chloromethyl methyl
ether (MOMCl, 0.97 g, 12 mmol) was added dropwise to the mix-
ture during 3 min. The reaction proceeded for 2 h under the moni-
toring of TLC (toluene/MeOH 9:1). After the completion of the
reaction, CH2Cl2 (30 mL) and saturated NaHCO3 solution (30
mL) was poured into the reaction mixture. After having been
shaken for one minute, the organic layer was separated, washed
with brine and dried over MgSO4. Then the dark solution quickly
passed through a sintered glass Büchner funnel containing 50 g of
silica gel and the filter cake was washed with 600 mL of CH2Cl2.
The combined filtrate was concentrated under reduced pressure
and a red solid as the crude product of 6 was obtained. It was
recrystallized from n-hexane (200 mL) to give 6 as red crystals.
Yield: 1.66 g (76%). mp 103-104 °C (n-hexane). IR (KBr):
2950w, 1665vs (C=O), 1604m, 1584m, 1287vs, 1153s, 1035vs
(C-O-C). 1H NMR ((D6)DMSO): 7.89 (d, J = 10.5, H-C(4)); 7.60
(dd, 1H, J = 7.2, 1.5); 7.50 (m, 2H); 6.34 (d, J = 10.5, H-C(3));
5.36 (s, 2H, CH2O); 3.43 (s, 3H, CH3O). 13C NMR ((D6)DMSO):
180.1, 178.3 (C(1), C(2)); 153.7, 137.5, 133.0 (3 Cnaph., quat.,
C(5), C(4a) , C(8a)); 131.8, 126.7, 123.3, 122.1, 121.5 (5 Cnaph.H,
C(3), C(4), C(6), C(7), C(8)); 94.5 (CH2O); 56.0 (CH3O). HRMS:
Calc. for C12H11O4 219.0652; found 219.0658 [M+H]+.
6-Bromo-1,2-dimethoxynaphthalene (11). Yield: 1.92 g
(72%). mp 54-55 °C (PE), (ref.27 55 °C). IR (KBr): 2933m,
1589m, 1500m, 1354m, 1276vs, 1104vs, 1066s (C-O-C). 1H NMR
(CDCl3): 7.99 (d, J = 9.0, H-C(8)); 7.92 (d, J = 1.5, H-C(5)); 7.50
(m, 2H, H-C(4), H-C(7)); 7.29 (d, J = 9.0, H-C(3)); 3.99 (s, 6H,
CH3O); 13C NMR (CDCl3): 148.5, 143.0, 130.6, 127.5, 117.9 (5
C
naph., quat., C(1), C(2), C(6), C(4a) , C(8a)); 129.5, 129.3, 123.3,
123.1, 116.2 (5 Cnaph.H, C(3), C(4), C(5), C(7), C(8)); 61.1, 56.8
(2 CH3O).
5,6-Dimethoxy-2-naphthaldehyde (12). Compound 11
(2.67 g, 10 mmol) was dissolved in dry THF (40 mL) and n-BuLi
(2.5 M in n-hexane, 4.8 mL, 12 mmol) was added dropwise at -78
°C. The mixture was stirred at -78 °C for an additional 30 min and
dry DMF (2.0 mL) was slowly added at the same temperature. Af-
ter the addition, the reaction temperature was allowed to rise to 0
°C in 2 h. Then the reaction was quenched with a saturated NH4Cl
solution (20 mL) and the organic layer was separated. Then the
aqueous phase was extracted with AcOEt (15 mL × 3). The com-
bined organic layer was washed with a saturated NH4Cl solution
(15 mL) and brine, dried over Na2SO4 and concentrated. The resi-
due was subject to CC (PE/AcOEt 8:1) to afford 12 as light-yel-
low crystals. Yield: 1.69 g (78%). mp 80-81 °C (n-hexane). IR
(KBr): 2820m, 1687vs (C=O), 1621s, 1484m, 1352s, 1277vs,
General procedure for the reduction-methylation of 6
and 10. To a suspension of 6 or 10 (10 mmol) in THF (40 mL)
1166
© 2013 The Chemical Society Located in Taipei & Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
J. Chin. Chem. Soc. 2013, 60, 1163-1168