Oxalic Acid → 5,6-Dimethoxy-2-methyl-3-[2-(4-phenylhydroxymethylpiperidyl)-ethyl]indole oxalate

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Reaction Steps

A suspension of 20.2 g of 4-benzoyl-1-(5,6-dimethoxy-2-methylindol-3-ylglyoxyloyl)piperidine in 200 ml of tetrahydrofuran is added dropwise to a stirring solution, under nitrogen at reflux, of 9.6 g of lithium aluminum hydride in 210 ml of tetrahydrofuran. Stirring and refluxing is continued for 3 hours, the mixture is cooled in an ice bath and the excess hydride is destroyed with water. The mixture is filtered and the filtrate is concentrated under reduced pressure, leaving an off-white foam which is triturated with cyclohexane to give an off-white powder. The oxalate salt is prepared by dissolving the free base in isopropanol and slowly adding a solution of oxalic acid in isopropanol. The isoluble oxalate salt is collected and recrystallized from ethanol to give white crystals, mp 152°-154° C., 5,6-dimethoxy-2-methyl-3-[2-(4-phenylhydroxymethylpiperidyl)-ethyl]indole oxalate.

Provenance & Evidence