Benzenemethanol, 4-chloro-alpha-methyl- → P-Chloroacetophenone

Beteiligte Stoffe

Reaktionsschritte

There were weighed out p-chlorophenyl-ethanol (5, racemic compound) (78 mg, 0.05 mmol) and (S)-(−)-3,3,5,5-tetramethyl-4H-dinaphtho[2,1-c:1′,2′-e]-azepin-N-oxyl (1.8 mg, 0.05 mmol). Then, 2 ml of acetone was added to obtain a uniform solution. Added thereto was 250 mg of silica gel (product of Merck, grade 9385) and the mixture was vigorously agitated for 5 minutes. The acetone used was distilled off under reduced pressure. Added thereto was 7% aqueous solution of sodium bicarbonate (5 ml) containing 20 wt. % of sodium bromide. Then, the mixture was thoroughly stirred. Two platinum electrodes (1.5×1.0 cm) were applied to the mixture which was then subjected to electrolytic oxidation reaction for 0.68 hour while being vigorously stirred at −15° C. and maintaining the current at 30 mA (quantity of electricity being 2.2 F/mol). After completion of reaction, silica gel was filtered off from the reaction mixture, extraction was effected with 5 ml of acetone and acetone was distilled off. The obtained residue was purified by silica gel column chromatography (ethyl acetate/hexane=7/1), giving p-chloroacetophenone (6) [39 mg, yield 100% based on the starting compound (5a)] and the starting compound (5b) (38 m, recovery percentage 97%, optical purity 83%).

Herkunft & Nachweise