Citric Acid → HCID 11405313, compound

Participants

Reaction Steps

1.3 g (3.9 mmol) of the 1-(4-methoxybenzenesulfonyl)indoline-2-carboxylic acid of Example 28a are dissolved in 10 ml of N,N-dimethylacetamide (DMA) and, at −20° C., admixed successively with 0.37 ml (1 equivalent) of ethyl chloroformate and 0.81 ml of N-methylmorpholine. After an activation time of 30 minutes (min), the mixture is admixed with 3.8 ml (19.5 mmol) of O-trimethylsilylhydroxylamine and stirred at RT for a further 4 h. The mixture is diluted with ethyl acetate, acidified with citric acid and, after removal of the aqueous phase, washed with saturated NaCl solution. The organic phase is dried over sodium sulfate, filtered off and concentrated under reduced pressure. The resulting oil is subjected to chromatography under pressure over silica gel 60 using dichloromethane/ethyl acetate/acetic acid 5.5/3.5/1 as mobile phase. Product fractions (showing positive iron(III) chloride-reaction) are pooled and concentrated. The crystalline product is subsequently admixed with diethyl ether and freed of residual solvent under reduced pressure.

Provenance & Evidence