反应详情

0.65 ml of a 1.7M solution of butyl lithium in hexane is added to a solution, cooled to -65°, of 111 mg (1.1 mmol) of diisopropylamine in 4 ml of tetrahydrofuran. The mixture is cooled to -78° and treated after 15 minutes with a solution of 321 mg (1 mmol) of (S)-1-(2,4-dimethoxy-benzyl)-4-[(R)-2,2-dimethyl-1,3-dioxolan-4-yl]-2-azetidinone in 1 ml of tetrahydrofuran. The mixture is stirred at -78° for 45 minutes and then a solution of 100 mg (2,27 mmol) of acetaldehyde in 0.5 ml of tetrahydrofuran is added dropwise within 3 minutes thereto, whereby the temperature rises to -70°. The mixture is stirred for 10 minutes, the cooling bath is removed, the reaction solution is treated with 2 ml of 14 percent aqueous ammonium chloride solution and extracted with 30 ml of ethyl acetate. The organic phase is washed with saturated sodium chloride solution, dried over sodium sulphate and evaporated in vacuo. The residue is chromatographed on 10 g of silica gel with ethyl acetate/hexane (2:1) as the eluent. There is obtained (3S,4S)-1-(2,4-dimethoxybenzyl)-4-[(R)-2,2-dimethyl-1,3-dioxolan-4-yl]-3-[(R)-1-hydroxyethyl]-2-azetidinone which is obtained as fine needles of melting point 145°-146° after crystallization from ethyl acetate/hexane.

1. temperatureThe mixture is cooled to -78°
2. customrises to -70°
3. stirringThe mixture is stirred for 10 minutes
4. customthe cooling bath is removed
5. additionthe reaction solution is treated with 2 ml of 14 percent aqueous ammonium chloride solution
6. extractionextracted with 30 ml of ethyl acetate
7. washThe organic phase is washed with saturated sodium chloride solution
8. dry with materialdried over sodium sulphate
9. customevaporated in vacuo
10. customThe residue is chromatographed on 10 g of silica gel with ethyl acetate/hexane (2:1) as the eluent