Potassium Bromide → (S)-2-methyl-3-quinoxalin-6-yl-propionaldehyde

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Reaction Steps

A solution of crude (S)-2-methyl-3-quinoxalin-6-yl-propan-1-ol (3.68 g, 18.19 mmol) in toluene (37 ml) is treated with TEMPO (28.4 mg, 0.152 mmol) and KBr (216.5 mg, 1.82 mmol) in 0.9 ml water. 37 ml of a 0.5 M sodiumhypochlorite solution of pH 8-9 (prepared by mixing 34 ml 0.75 M sodiumhypochlorite solution with 16 ml water and 0.85 g NaHCO3) is added dropwise over 20 minutes at 5° to 8°. After 5 minutes stifling at 0°, the two phase mixture is filtered over Hyflo, the phases separated, the organic phase washed with a solution of 116 mg KI in 15 ml 1 N HCl, then 15 ml of a 5% Na2S2O3 solution and finally 15 ml brine. Drying over Na2SO4 and evaporation afford crude aldehyde. MPLC purification (silicagel, EtOAc/hexane 2:1) yield pure (S)-2-Methyl-3-quinoxalin-6-yl-propionaldehyde as a slightly yellow clear oil. TLC (silicagel, EtOAc/hexanes 2:1): rf 0.37.

Provenance & Evidence