反应详情

Prepared according to general procedure B from ethyl vinyl ketone (70 μL, 0.70 mmol), isoprene (140 μL, 1.40 mmol), 70% aqueous perchloric acid (12.1 μL, 0.14 mmol) and (2S, 5S)-5-benzyl-3-methyl-2-(5-methyl-furan-2-yl)-imidazolidin-4-one (38 mg, 0.14 mmol) neat for 3 days at −20° C. Then, another portion of isoprene (100 μL, 1.00 mmol) was added and the solution was allowed to stir for an additional 3 days. Purification by silica gel chromatography (10:1 pentane:ether) provided the title compound as a single regioisomer (as judged by GLC analysis) in 79% yield (84 mg, 0.55 mmol) and 85% ee. IR (film) 2967, 2928, 2836, 1710, 1452, 1413, 1377, 1343, 1217, 1149, 1126, 952.6, 915.1, 871.9, 800.0 cm−1; 1H NMR (300 MHz, CDCl3) δ 5.34 (m, 1H, C═CH), 2.46 (m, 3H, CH2CO and CHCO), 2.09 (m, 2H, CH2CH═C(CH3)), 1.94 (m, 2H, CH2C(CH3)═CH), 1.86 (m, 1H, one of CH2CH2CH), 1.54 (m, 1H, one of CH2CH2CH), 0.99 (dd, J=7.5, 7.5 Hz, 3H, CH2CH3); 13C NMR (75 MHz, CDCl3) δ 214.4, 133.8, 119.6, 46.6, 34.1, 29.9, 27.6, 25.4, 23.7, 8.1; HRMS (CI) exact mass calc'd for (C10H16O) requires m/z 152.1201, found m/z 152.1201. [α]D=+37.8 (c=1.0, CHCl3). Product ratios were determined by GLC analysis (100° C., 23 psi); (R) isomer tr=16.1 min, and (S) isomer tr=15.4 min.

1. customPrepared
2. customPurification by silica gel chromatography (10:1 pentane:ether)