反应详情

Prepared according to general procedure A from oct-2-en-4-one (89 μL, 0.60 mmol), cyclopentadiene (74 μL, 0.90 mmol), 70% aqueous perchloric acid (10.3 μL, 0.12 mmol) and (2S, 5S)-5-benzyl-3-methyl-2-(5-methyl-furan-2-yl)-imidazolidin-4-one (32.4 mg, 0.12 mmol) neat for 34 hours at 0° C. Purification by silica gel chromatography (19:1 hexanes:ethyl acetate) provided the title compound as a colorless oil in 83% yield (95.7 mg, 0.50 mmol); 22:1 endo:exo, endo 92% ee. IR (film) 3061, 2958, 2871, 1707,1462, 1409, 1375, 1332, 1267, 1137, 1045, 904.4, 801.4, 715.9 cm−1; 1H NMR (300 MHz, CDCl3) δ 6.19 (dd, J=5.4, 3.0 Hz, 1H, CH═CH), 5.87 (dd, J=5.7, 2.7 Hz, 1H, CH═CH), 3.10 (br s, 1H, CHCH═CH), 2.43 (m, 1H, CHCH═CH), 2.39 (in, 3H, CHCO and CH2CO), 1.86 (m, 1H, CHCH3), 1.57-1.20 (m, 6H, COCH2CH2CH2, and CHCH2CH), 1.12 (d, J=6.9 Hz, 3H, CHCH3), 0.87 (dd, J=7.5, 7.5 Hz, 3H, CH2CH3); 13C NMR (75 MHz, CDCl3) δ 211.3, 138.6, 132.6, 61.2, 49.3, 46.6, 41.7, 35.9, 26.2, 22.8, 21.4, 14.3; HRMS (CI) exact mass calc'd for (C13H20O) requires m/z 192.1514, found m/z 192.1509. [α]D=+89.3 (c=1.0, CHCl3). Product ratios were determined by GLC analysis (150° C., 23 psi); (1R, 2R, 3S, 4R) endo isomer tr=6.1 min, and (1S, 2S, 3R, 4S) endo isomer tr=5.9 min, exo isomers tr=5.5, 5.6 min.

1. customPrepared
2. customPurification by silica gel chromatography (19:1 hexanes:ethyl acetate)