反应详情

(5-Ethoxycarbonyl-5-methylhexyl)-triphenylphosphonium bromide (35.0 g, 0.0619 mol) was dissolved in dichloromethane (100 mL) containing 2-chlorobenzaldehyde (8.70 g, 0.0619 mol). A solution of sodium hydroxide (10 g, 0.25 mol) in water (10 mL) was added in portions over ten minutes. The mixture stirred for 2 hours at room temperature. After two hours, the layers were separated and the dichloromethane fraction was washed with water (2×150 mL), dried over sodium sulfate, filtered, and concentrated under reduced pressure. The remaining brown oil (18.99 g) was filtered through silica gel (200 g), eluting with ethyl acetate/heptane (1:9). The product containing fractions were combined and concentrated under reduced pressure. The remaining yellow oil (10.5 g) was contaminated with 2-chlorobenzaldehyde (30-40%). The material was reprocessed by dissolving in fresh dichloromethane (100 mL) with additional phosphonium salt (25 g, 0.048 mol). Sodium hydroxide (10 g, 0.25 mol) in water (10 mL) was added in portions and the mixture was allowed to stir for 4 hours at room temperature. The layers were separated and the dichloromethane fraction was washed with water (2×100 mL), dried over sodium sulfate, filtered, and concentrated under reduced pressure. The remaining brown oil was purified by column chromatography on silica gel (200 g), eluting with ethyl acetate/heptane (1:9). The product-containing fractions were combined and concentrated under reduced pressure to provide 7-(2-chlorophenyl)-2,2-dimethylhept-6-enoic acid ethyl ester (12.0 g, 60% yield) as a light, yellow liquid. 1H NMR (300 MHz, CDCl3/TMS): δ=7.47 (d, 0.4H, J=7.5 Hz), 7.36-7.07 (m, 3.6H), 6.74 (d, 0.4H, J=15.6 Hz), 6.50 (d, 0.6H, J=11.4 Hz), 6.16 (dt, 0.4H, J=15.6, 7.2 Hz), 5.75 (dt, 0.6H, d=11.4, 7.2 Hz), 4.10 (m, 2H), 2.26-2.12 (m, 2H), 1.61-1.34 (m, 4H), 1.29-1.17 (m, 3H), 1.14 (s, 6H). (mixture of cis/trans isomers). 13C NMR (75 MHz, CDCl3/TMS): δ=177.59, 135.63 (2 peaks), 133.67, 133.45, 133.31, 132.38, 130.31, 129.41, 129.19, 127.84, 127.73, 126.57, 126.47, 126.24, 126.00, 60.16, 42.12, 42.07, 40.22, 33.56, 28.83, 25.21, 25.16, 24.69, 14.30. (mixture of cis/trans isomers). HRMS (MMI-TOF): Calculated for C22H29Cl2NO2S (MH+): 406.1202. Found 406.1594.

1. waitAfter two hours
2. customthe layers were separated
3. washthe dichloromethane fraction was washed with water (2×150 mL)
4. dry with materialdried over sodium sulfate
5. filtrationfiltered
6. concentrationconcentrated under reduced pressure
7. filtrationThe remaining brown oil (18.99 g) was filtered through silica gel (200 g)
8. washeluting with ethyl acetate/heptane (1:9)
9. additionThe product containing fractions
10. concentrationconcentrated under reduced pressure
11. stirringto stir for 4 hours at room temperature
12. customThe layers were separated
13. washthe dichloromethane fraction was washed with water (2×100 mL)
14. dry with materialdried over sodium sulfate
15. filtrationfiltered
16. concentrationconcentrated under reduced pressure
17. customThe remaining brown oil was purified by column chromatography on silica gel (200 g)
18. washeluting with ethyl acetate/heptane (1:9)
19. concentrationconcentrated under reduced pressure