反应详情

A solution of 6.5 g (50.3 mmol) of ethyl valerimidate (free base) in 90 mL of dry CH2Cl2 was treated with 7.71 mL (5.60 g, 55.3 mmol) of triethylamine. The resulting solution was stirred under N2 at -10° C. in an ice-salt bath as a solution of 4.81 mL (5.46 g, 50.3 mmol) of ethyl chloroformate in 10 mL of CH2Cl2 was added dropwise over 25 minutes. Upon completion of the addition, the cooling bath was removed, and the mixture was stirred at room temperature for 2 hours. Next, the solvent was removed by evaporation in vacuo. The residue was taken up in hexane and filtered to remove triethylamine hydrochloride. Concentration of the filtrate yielded 7.08 g (70%) of the product as a yellow oil, suitable for use in the next step without further purification. NMR indicated a mixture of syn and anti isomers. TLC (98:2 CH2Cl2 -MeOH) showed a close pair of spots, Rf 0.48, 0.52.

1. additionwas added dropwise over 25 minutes
2. additionUpon completion of the addition
3. customthe cooling bath was removed
4. customNext, the solvent was removed by evaporation in vacuo
5. filtrationfiltered
6. customto remove triethylamine hydrochloride