反应详情

To a 3.0 M solution of lithium diisopropylamide in tetrahydrofuran [prepared from diisopropylamine (0.56 ml), tetrahydrofuran (5 ml) and a 1.4 M solution of butyllithium in hexane (2.2 ml)] was added dropwise 0.41 ml of ethyl isobutyrate at -70° C., and the mixture was stirred at that temperature for 40 minutes. To it was added dropwise a solution of 0.26 g of the benzyl chloride compound (prepared as described in Reference Example 2) in 2.8 ml of a mixture of HMPA and tetrahydrofuran (1:1) at -70° C., and the mixture was stirred at that temperature for 2 hours, and then at room temperature for one hour. The reaction mixture was poured into a saturated aqueous solution of ammonium chloride, and extracted with diethyl ether. The extract was washed with a saturated aqueous solution of sodium chloride, dried over sodium sulphate and concentrated under reduced pressure. The residue was purified by column chromatography on silica gel using a mixture of cyclohexane and ethyl acetate (2:1) as eluent to give 0.27 g of the title compound having the following physical characteristics:

1. stirringthe mixture was stirred at that temperature for 2 hours
2. waitat room temperature for one hour
3. extractionextracted with diethyl ether
4. washThe extract was washed with a saturated aqueous solution of sodium chloride
5. dry with materialdried over sodium sulphate
6. concentrationconcentrated under reduced pressure
7. customThe residue was purified by column chromatography on silica gel using
8. additiona mixture of cyclohexane and ethyl acetate (2:1) as eluent