反应详情

2-Methylglutaric acid (14.6 g.) and acetyl chloride (26 ml.) are heated in the steam bath for one hour. The mixture is concentrated to dryness in vacuo and the residue evaporated twice from toluene. The residue is dissolved in methanol (4.7 ml.), heated on the steam bath for one hour and concentrated to dryness. The residue is dissolved in a mixture of ether (17 ml.), dicyclohexylamine (16.7 ml.) and hexane (83 ml.). The crystalline salt is filtered, stirred and treated with boiling ethyl acetate (75 ml.). The insoluble material is filtered off, and the filtrate is concentrated to one-third volume and chilled. The crystals are filtered and dried to yield 11.3 g. of 4-methoxycarbonyl-2-methyl butanoic acid dicyclohexylamine salt, m.p. 97°-99°. The salt is converted to the free acid by treatment with Dowex 50.

1. concentrationThe mixture is concentrated to dryness in vacuo
2. customthe residue evaporated twice from toluene
3. dissolutionThe residue is dissolved in methanol (4.7 ml.)
4. temperatureheated on the steam bath for one hour
5. concentrationconcentrated to dryness
6. dissolutionThe residue is dissolved in a mixture of ether (17 ml.), dicyclohexylamine (16.7 ml.) and hexane (83 ml.)
7. filtrationThe crystalline salt is filtered
8. additiontreated with boiling ethyl acetate (75 ml.)
9. filtrationThe insoluble material is filtered off
10. concentrationthe filtrate is concentrated to one-third volume
11. temperaturechilled
12. filtrationThe crystals are filtered
13. customdried
14. customto yield 11.3 g