Sodium Thiosulfate Pentahydrate → HCID 54498398, compound

Participants

Reaction Steps

N-Carboxybenzyl-D-phenylalaninol (100 g ;0.35M) is dissolved in ethyl acetate/toluene (1:1; 1.5-2.0 L) or dichloromethane (1.0-2.0 L) and a solution of sodium bromide (18.0-25.2 g; 0.175-0.25M) in water (50-250 mL) added. The resulting two phase mixture is stirred and cooled to 0°-5° C. under a nitrogen atmosphere. 2,2,6,6-Tetramethyl-1-piperidinyloxy free radical (TEMPO) (0.055-0.55 g; 3.5-35 mM) is added. A solution of buffered sodium hypochlorite, freshly prepared by dissolving sodium bicarbonate (10-25 g; 0.12-0.3M) and commercial sodium hypochlorite solution (6-12.5% w/w; 250-584 g; 0.42-0.49M) in water (25-250 g), is added over a period of one hour with fast agitation, maintaining the reaction temperature <5° C. A solution of sodium thiosulfate pentahydrate (21.8-122 g; 0.088-0.49M) in water (64 -370 mL) is then immediately added and the reaction mixture efficiently stirred until excess oxidants have been quenched as demonstrated by starch/iodide test. Agitation is stopped and the mixture allowed to settle at 5°-10° C. After 15 minutes, the phases are separated. The organic phase is then washed with aqueous sodium bicarbonate solution (3% w/w; 500 mL) and aqueous sodium chloride solution (3% w/w; 500 mL). The organic phase is concentrated by vacuum distillation to a volume of approximately 300 mL maintaining the heating bath <20° C. Heptane (750 mL) is added and the vacuum distillation optionally continued to precipitate the product, while maintaining the heating bath <20° C. The precipitate is filtered, washed with heptane (2×200 mL) and dried under vacuum at 20° C. to constant weight to yield N-carboxybenzyl-D-phenylalaninal (90 g; 90% yield) as a white crystalline solid.

Provenance & Evidence