Asymmetric reduction of 2-bromo 3-nitro-4-benzyloxy acetophenone

2 ASYMMETRIC REDUCTION OF 2-BROMO-(3-NITRO-4-BENZYLOXY)ACETOPHENONE[161 

A solution of bromoketone 3 in tetrahydrofuran (lOOg in 800 mL THF, 0.35 M) was slowly added over 1 hour to the oxazoborolidine solution while the temperature was maintained between 0-5 °C. The mixture was stirred for 

Acetone (100 mL) was slowly added to quench the excess borane. The reaction mixture was concentrated to 300 mL and toluene (700 mL) was added. The solution was washed with 2% sulfuric acid (350 g) then with 20% NaCl (120 g). The organic phase was concentrated to 300 mL and cooled to 5°C. 

The resulting slurry was stirred at 5°C for 1 hour, heptane (200 mL) was slowlyadded and the mixture was stirred an additional 1 hour at 5°C. 

The slurry was filtered and the solid was washed with heptane (200 mL). The off-white solid was dried in vacuo to give 89 g (93% ee, 99% cp) of the desired alcohol. 

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Asymmetric reduction of 2-bromo-(3-nitro-4-benzyloxy) acetophenone. . 157... 

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