Molecules 2007, 12
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6.2 Hz), 1.59–1.57 (2 H, m), 1.55–1.49 (2 H, m), 1.41–1.32 (2 H, m), 1.07 (2 H, qt, J = 13.5, 4.1 Hz)
13
ppm; C-NMR/APT (75 MHz, CDCl3) δ 209.77 (C), 55.43 (CH), 41.13 (CH2), 24.92 (CH2), 24.36
(CH2) ppm; MS m/z (%) 166 (M+, 49), 138 (14), 123 (24), 111 (10), 110 (38), 109 (10), 98 (25), 97
(52), 96 (11), 95 (39), 94 (11), 84 (100), 83 (97), 82 (39), 81 (24), 79 (29), 69 (13), 68 (43), 67 (70), 66
(11), 65 (11), 55 (80), 54 (57), 53 (31), 51 (11), 50 (4), 43 (13), 42 (32), 41 (71).
1,2,3,5,6,7-Hexahydro-4,8-di(trimethylsilyloxy)naphthalene (3)
A solution of dione 2 (4:1 mixture of isomers; 1.0 g, 6.2 mmol) in dry CH2Cl2 (50 mL) was placed
under Ar, protected from light and cooled to –30 °C. 1,1,1,3,3,3-Hexamethyldisilazane (HMDS; 3.05
mL, 14.5 mmol, 2.4 eq) and trimethylsilyl iodide (1.89 mL, 13.3 mmol, 2.2 eq) were slowly added
dropwise. The mixture was stirred at –30 °C for 20 min, allowed to warm, stirred at rt for 30 min and
then cooled again to –60 °C. The reaction mixture was washed with a saturated NaHCO3 solution, the
organic layer was dried over anhydrous Na2SO4 and concentrated under reduced pressure. The residual
yellow oil was purified by column chromatography on Florisil (petroleum ether/CH2Cl2, 7:3) to afford
bis(trialkylsilyl)enol ether 3 (1.6 g, 83%): Rf (CH2Cl2) 0.75; IR (KBr film) ν 2956 (w), 2836 (w), 1628
(m), 1442 (w), 1353 (m), 1251 (s), 1213 (s), 1199 (s), 1119 (w), 1053 (w), 977 (s), 910 (w), 887 (w),
866 (s), 840 (s), 751 (w) cm–1; 1H-NMR (300 MHz, CDCl3) δ 2.22 (4 H, t, J = 6.1 Hz), 2.13 (4 H, t, J
= 6.2 Hz), 1.66 (4 H, quintet, J = 6.2 Hz), 0.17 (18 H, s) ppm.
3,4,7,8-Tetrahydronaphthalene-1,5(2H,6H)-dione (4)
After concentration in vacuo the residual oil 3 was s left in a round bottom flask open at the air (O2)
at rt for 96 h. From time to time the content of the flask is gently swirled so as to obtain a thin film at
the surface of the flask. During that period the oil slowly crystallises into a yellow solid. The latter was
purified by column chromatography on silica gel (CH2Cl2/EtOAc, 99:1) to give enedione 4 (0.495 g,
50% from 2). However, purified 3 left standing exposed to the air for 96 h afforded after purification 4
in 100% yield. Data of 4: mp 108 °C; Rf (CH2Cl2/EtOAc, 9:1) 0.37; UV (CH3OH) λmax 260 nm; IR
(KBr film) ν 2944 (m), 2873 (w), 1671 (s), 1461 (w), 1418 (w), 1321 (w), 1255 (w), 1227 (w), 1143
(m), 1120 (m), 1036 (m), 939 (w), 864 (w), 821 (w), 730 (w), 680 (w), 568 (w), 499 (w), 461 (w) cm–1;
1H NMR (500 MHz, CDCl3) δ 2.48–2.46 (8 H, m), 1.97 (4 H, quintet, J = 6.3 Hz) ppm; 13C NMR/APT
(75 MHz, CDCl3) δ 201.5 (C), 145.9 (C), 38.2 (CH2), 22.3 (CH2), 21.8 (CH2) ppm; MS m/z (%) 164
(M+, 99), 136 (100), 135 (24), 121 (31), 94 (6), 93 (14), 92 (10), 91 (14), 80 (40), 79 (97), 78 (10), 77
(29), 66 (12), 65 (17), 55 (33), 53 (21), 52 (38), 51 (27), 50 (11), 41 (17).
Acknowledgements
G. M. thanks the Ghent University for financial support (BOF 011D18804).
References and Notes
1. (a) Proceedings of the 12th Workshop on Vitamin D; Bouillon, R., Norman, A. W., Pasqualini, J.
R., Eds.; J. Steroid Biochem. Mol. Biol. 2004, 89–90, 1–633, and the previous 11 volumes in this