反应详情

A mixture of the cyclopentenol obtained according to Example 1 (5 g, 32.5 mmol) with triethyl orthoacetate (47.2 ml=42.1 g, 260 mmole, 8 eq.) was heated to 145° (temp. of oil bath 160°) under a nitrogen current in a reactor which was equipped with a Vigreux column and a condenser, while adding continuously, over 4 h, pivalic acid (232 mg, 2.28 mmole, 7 mol %) in triethyl orthoacetate (5.9 ml=5.26 g, 32.5 mmole, 1 eq.). During the reaction, the formed ethanol, as well as the ethyl acetate and a little orthoacetate, were removed by distillation. The reaction mixture was heated for 1 more hour, then cooled to 20°, hydrolyzed with diluted aqueous NaHCO3 and extracted with ether. The organic layer was washed 2x with water and once with brine, dried over Na2SO4 and evaporated, to give 15.4 g of crude product. After distillation of the heads (6.6 g, 50°/1.1×102 Pa), 5.30 g (95°/1.1×102 Pa) of (+)-ethyl (1 R)-2-pentyl-2-cyclopentene-1-acetate were obtained (yield 73%), having an enantiomeric purity of 90% e.e. (chiral column of the type Megadex® 5).

1. customobtained
2. temperaturewas heated to 145° (temp. of oil bath 160°) under a nitrogen current in a reactor which
3. customwas equipped with a Vigreux column and a condenser
4. additionwhile adding continuously, over 4 h
5. customDuring the reaction
6. customthe formed ethanol, as well as the ethyl acetate and a little orthoacetate, were removed by distillation
7. temperatureThe reaction mixture was heated for 1 more hour
8. temperaturecooled to 20°, hydrolyzed with diluted aqueous NaHCO3
9. extractionextracted with ether
10. washThe organic layer was washed 2x with water
11. dry with materialonce with brine, dried over Na2SO4
12. customevaporated
13. customto give 15.4 g of crude product
14. distillationAfter distillation of the heads (6.6 g, 50°/1.1×102 Pa)