The Journal of Organic Chemistry
Page 24 of 44
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silica gel (petroleum ether/EtOAc = 100/1→80/1→50/1) to afford 34 (36 mg, 24% yield) and 35
1
(
89 mg, 59% yield). Compound 34: H NMR (300 MHz, CDCl
3
) δ (ppm) 7.09–6.97 (m, 2H),
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.68–6.61 (m, 2H), 6.02 (d, J = 9.6 Hz, 1H), 4.76 (bs, 1H), 4.14 (dd, J = 9.0, 7.8 Hz, 1H), 3.19 (m,
J = 6.9 Hz, 1H), 2.49 (dd, J = 15.0, 7.5 Hz, 1H), 2.21 (dd, J = 15.0, 9.0 Hz, 1H), 1.17 (d, J = 6.9
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Hz, 3H), 0.98 (d, J = 6.9 Hz, 3H), 0.94 (s, 9H), 0.86 (s, 3H), 0.13 (s, 3H), 0.11 (s, 3H); C{ H}
NMR (151 MHz, CDCl
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) δ (ppm) 151.2, 143.2, 137.4, 133.7, 132.6, 127.2, 120.9, 120.1, 117.1,
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14.1, 79.1, 50.3, 35.5, 27.0, 26.0, 21.9, 21.2, 18.3, 16.5, -4.2, -4.6. Compound 35: H NMR (300
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MHz, CDCl ) δ (ppm) 6.98 (d, J = 8.1 Hz, 1H), 6.91 (d, J = 2.7 Hz, 1H), 6.66 (dd, J = 8.1, 2.7 Hz,
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H), 6.25 (d, J = 9.6 Hz, 1H), 5.88 (d, J = 9.6 Hz, 1H), 5.04 (bs, 1H), 4.12 (dd, J = 9.0, 7.5 Hz,
H), 3.19 (m, J = 6.9 Hz, 1H), 2.48 (dd, J = 15.0, 7.5 Hz, 1H), 2.21 (dd, J = 15.0, 9.3 Hz, 1H),
.17 (d, J = 6.9 Hz, 3H), 0.98 (d, J = 6.9 Hz, 3H), 0.94 (s, 9H), 0.86 (s, 3H), 0.12 (s, 3H), 0.11 (s,
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H); C{ H} NMR (151 MHz, CDCl ) δ (ppm) 154.3, 143.3, 135.4, 133.8, 132.6, 128.1, 127.5,
123.9, 114.1, 113.7, 79.1, 50.4, 35.5, 26.9, 26.0, 21.9, 21.1, 18.2, 16.7, -4.2, -4.6.
Acid-mediated cyclization of 33: To a solution of 33 (24 mg, 0.06 mmol) in freshly distilled
ethyl ether (6.0 mL) was added BF
15 min. The mixture was stirred for 1 h at 0 °C and then at room temperature for an additional 6 h.
The reaction mixture was quenched with saturated aqueous NaHCO and extracted with ethyl
ether (2 × 15 mL). The combined organic layers were dried over Na SO , filtered, concentrated,
O = 50/1→30/1) to give
) δ (ppm) 7.04 (d, J = 8.4
3 2
•OEt (76 μL, 0.60 mmol, 10.0 equiv) at 0 °C over a period of
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and purified by column chromatography on silica gel (petroleum ether/Et
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6 (17.5 mg, 76% yield) as a colorless oil. H NMR (300 MHz, CDCl
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Hz, 1H), 6.96 (d, J = 2.4 Hz, 1H), 6.73 (dd, J = 8.4, 2.4 Hz, 1H), 6.26 (d, J = 9.3 Hz, 1H), 5.88 (d,
J = 9.3 Hz, 1H), 4.13 (dd, J = 9.0, 7.5 Hz, 1H), 3.83 (s, 3H), 3.21 (m, J = 6.9 Hz, 1H), 2.48 (dd, J
=
15.0, 7.5 Hz, 1H), 2.21 (dd, J = 15.0, 9.0 Hz, 1H), 1.19 (d, J = 6.9 Hz, 3H), 0.99 (d, J = 6.9 Hz,
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H), 0.94 (s, 9H), 0.85 (s, 3H), 0.12 (s, 3H), 0.10 (s, 3H); C{ H} NMR (151 MHz, CDCl
ppm) 158.4, 143.0, 135.5, 134.1, 132.3, 127.9, 127.4, 123.9, 113.5, 111.5, 79.1, 55.4, 50.5, 35.5,
7.0, 26.0, 21.9, 21.2, 18.3, 16.7, -4.2, -4.6.
3R,3aR,5S)-3-((tert-Butyldimethylsilyl)oxy)-1-isopropyl-3a-methyl-3,3a,4,5-tetrahydro-2H-c
3
) δ
(
2
(
yclopenta[a]naphthalene-5,6-diol (46): To a solution of 32 (0.804 g, 2.07 mmol) in THF (20 mL)
was added EtMgBr (1.0 M in THF, 2.3 mL, 2.3 mmol, 1.1 equiv) slowly over a period of 20 min
o
at -78 C under argon atmosphere. The mixture was then warmed up slowly to 40 °C, and stirred
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