反应详情

2.03 g of NaH (50% in mineral oil) was suspended in 120 ml of DMF. 12.9 g of 4-(diethoxy-phosphinyl)-3-methyl-but-2-enoic acid ethyl ester was added at 0°. The mixture was stirred for 15 min at 0° and for 30 min at RT. After recooling to 0°, 5.72 g of 2-bromo-cyclopent-1-enecarbaldehyde, dissolved in 11 ml of DMF, was added drop by drop and allowed to react for 10 min. at 0° and for 2 h at RT. The mixture was then poured onto crushed ice, extracted with EtOEt, washed with sat. NaCi-solution, dried over Na2SO4, and evaporated to dryness. Purification of the residue by flash chromatography (silica gel, hexane/AcOEt=97/3) and crystallization from hexane/trace amounts of AcOEt yielded finally 3.408 g of pure (2E,4E)-5-(2-bromo-cyclopent-1-enyl)-3-methyl-penta-2,4-dienoic acid ethyl ester as yellowish crystals of mp. 85°-86°.

1. customAfter recooling to 0°
2. additionwas added drop by drop
3. customto react for 10 min. at 0° and for 2 h at RT
4. additionThe mixture was then poured
5. customonto crushed ice
6. extractionextracted with EtOEt
7. washwashed with sat. NaCi-solution
8. dry with materialdried over Na2SO4
9. customevaporated to dryness
10. customPurification of the residue
11. customby flash chromatography (silica gel, hexane/AcOEt=97/3) and crystallization from hexane/