Li et al.
FULL PAPER
=CCH2C(Br)), 2.93 (d, J=18 Hz, 1H, the other H of
=CCH2C(Br)), 4. 25 (q, J=7.2 Hz, 2H, OCH2), 5.05—5.09
(m, 1H, CH=), 5.28—5.32 (m, 1H, CH=); 13C NMR
(CDCl3, 75 MHz) δ: 13.86 (CH3CH2O), 17.68 (CH3), 25.68
(CH3), 26.20, 27.18, 33.93, 37.04, 37.60 (CH2), 59.48 (CBr),
61.83 (CH2O), 117. 33, 123.86 (CH=), 131.64, 137.01
(C=), 170.88 (C=O). HRMS (ESI) calcd for C15H23BrO2:
314.0881, found 314.0877.
((CH3)2C), 34.3, 37.2, 39.2 (CH2), 60.7 (CBr), 61.7 (OCH2),
126.4 (C=), 132.4 (C=), 170.6 (C=O). HRMS (ESI)
calcd for C15H23BrO2 314. 0881, found 314. 0869.
11 Detailed procedure for the preparation of 8,8-dimethyl-
3,4,5,6,7,8-hexahydronaphthalene-2-carboxylic acid ethyl
ester (6): To a solution of 5 (3.14 g, 10 mmol) in anhydrous
CH2Cl2 (100 mL) was added dropwise DBU (2.28 g, 15
mmol) under cooling in an ice bath. The solution was stirred
at 0 ℃ for 6 h. The progress of the reaction was monitored
by GC. The reaction mixture was diluted with H2O (50 mL).
The phases were separated and the aqueous phase was ex-
tracted with additional CH2Cl2 (30 mL×2). The combined
organic phases were washed with aq. NH4Cl (50 mL×3),
aq. NaHCO3 (50 mL), H2O (50 mL) and saturated NaCl (50
mL), dried (MgSO4) and concentrated. The residue obtained
was purified by flash chromatography (SiO2, n-hexane/
EtOAc, V/V, 100∶ 1) to give 1.99 g of compound 6 as pale
yellow oil in 85% yield. IR (KBr) ν: 2932, 1701, 1584, 1462,
10 Procedure for conversion of 3a to 2-bromo-8,8-dimethyl-
1,2,3,4,5,6,7,8-octahydronaphthalene-2-carboxylic
acid
ethyl ester (5): To a solution of 3a (3.14 g, 10 mmol) in
toluene (100 mL) was added dilute sulfuric acid (62%, 1.74
g, 11 mmol). The mixture was refluxed for 12 h. After
cooling to r.t., the mixture was neutralized with aq. Na-
HCO3. The phases were separated and the organic phase
was washed with saturated aq. NaHCO3 (50 mL), H2O (50
mL) and saturated aq. NaCl (50 mL), dried over Na2SO4
and concentrated to give the crude product, which was puri-
fied by column chromatography (SiO2, n-hexane/EtOAc,
V/V, 100∶1). Compound 5 was obtained as pale yellow oil
in 65% yield. IR (neat) ν: 2959, 2931, 1737, 1463, 1206
cm- 1; 1H NMR (CDCl3, 300 MHz) δ: 0.97 (s, 6H, (CH3)2C),
1.29 (t, J=7.2 Hz, 3H, CH3CH2O), 1.44—2.37 (m, 10H, 5
CH2), 2.64 (d, J=16.5 Hz, 1H, C(1)-H), 2.91 (d, J=16.5
Hz, 1.18, 1H, C(1)-H), 4.23 (q, J=7.2 Hz, 2H, CH3CH2O);
13C NMR (CDCl3, 75 MHz) δ: 13.8 (CH3CH2), 19.0 (CH2),
26.9, 27.3 ((CH3)2C), 29.9 (CH2), 30.5 (CH2), 33.7
1252, 1094 cm- 1; H NMR (CDCl3, 300 MHz) δ: 1.04 (s,
1
6H, (CH3)2), 1.31 (t, J=7.2 Hz, 3H, CH3), 1.47—1.51 (m,
2H, CH2), 1.61—1.65 (m, 2H, CH2), 2.05—2.13 (m, 4H,
2CH2), 2.37 (t, J=9.6 Hz, 2H, CH2), 4.21 (q, J=7.2 Hz, 2H,
CH2), 7.14 (s, 1H, =CH); 13C NMR (CDCl3, 75 MHz) δ:
167.7 (C=O), 137.3, 134.6, 134.4, 125.1, 60.1, 38.8, 32.4,
31.3, 29.3, 28.40 (2C), 21.4, 19.1, 14.4; HRMS (ESI) calcd
for C15H22O2 234.1620, found 234.1615.
(E0908051 Cheng, F.; Lu, Z.)
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© 2010 SIOC, CAS, Shanghai, & WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Chin. J. Chem. 2010, 28, 613— 616