Reaction Steps
A solution of (Z)-cyclooct-2-enol 30 (2.36 g, 14.0 mmol) and methyl benzoate (1.8 mL, 1.94 g, 14.3 mmol, 1.0 eq) in diethyl ether/heptanes 1:2 (500 mL) was irradiated for 32 hr, while it was continuously lead through a column filled with silica/silver nitrate 10:1 (41 g), silica (0.5 cm) and sand (0.5 cm). The column was placed in the dark during the irradiation. The column was eluted with dichloromethane (250 mL) to give unreacted starting material. The silica was stirred with dichloromethane/12.5% aqueous ammonia 1:1 (3×100 mL). The combined organic layers were dried over sodium sulfate, filtered and evaporated in vacuo to give crude product 31 as a grey oil. The oil was purified by column chromatography (silica, eluens pentane/diethyl ether 10% to 50%) to give (E)-cyclooct-2-enol 31 (major isomer, second fraction, 440 mg, 3.49 mmol, 24.9%) as a colorless oil and (E)-cyclooct-2-enol 31 (minor isomer, first fraction, 325 mg, 2.58 mmol, 18.4%) as a colorless oil. The major diastereoisomer is identical to the (1RS,2RS)-trans-cyclooct-2-en-1-ol prepared via a different route by G. H. Whitham, M. Wright, J. Chem. Soc. (C) 1971, 883. The minor diastereoisomer is identical to the (1SR,2RS)-trans-cyclooct-2-en-1-ol prepared via a different route by G. H. Whitham, M. Wright, J. Chem. Soc. (C) 1971, 886. Minor isomer: 1H-NMR (CDCl3, 300 MHz) δ=0.71-0.82 (m, 1H), 1.05-1.17 (m, 1H), 1.43-1.72 (m, 4H), 1.80-2.09 (m, 4H), 2.45-2.52 (m, 1H), 4.61 (s, 1H), 5.54-5.61 (m, 1H), 5.90-6.00 (m, 1H) ppm. 13C-NMR (CDCl3, 75 MHz) δ=23.35, 29.42, 36.08, 36.27, 43.40, 71.40, 130.78, 135.39 ppm. Major isomer: 1H-NMR (CDCl3, 300 MHz) δ=0.64-0.90 (m, 2H), 1.31-1.51 (m, 2H), 1.66-1.95 (m, 4H), 2.06-2.14 (m, 1H), 2.22-2.37 (m, 1H), 2.78 (br, 1H), 4.15-4.23 (m, 1H), 5.45-5.65 (m, 2H) ppm. 13C-NMR (CDCl3, 75 MHz) δ=27.83, 29.28, 30.52, 35.58, 36.05, 44.48, 131.86, 136.00 ppm.
