Hydrochloric Acid → Rivoglitazone

Participants

Reaction Steps

A mixture of 5-methoxy-N-methyl-1,2-phenylenediamine (21.8 g), 5-(4-methoxycarbonylmethyloxybenzyl)thiazolidine-2,4-dione (63.4 g), 1,4-dioxane (250 mg) and concentrated hydrochloric acid (750 ml) was heated under reflux for 60 hours. The reaction mixture was cooled in an ice bath and the precipitated crystals were filtered. To the crystals were added 5% aqueous sodium hydrogencarbonate solution (800 ml) and the mixture was stirred at room temperature for 2 hours. The mixture was filtered and the insoluble material was collected by filtration and dissolved in a mixture of N,N-dimethylformamide (1000 ml) and methanol (200 ml) and decolorized with active charcoal. The active charcoal was removed by filtration and the filtrate was concentrated to about 50 ml. To the solution was added diethyl ether (750 ml) and allowed to stand at room temperature for 2 days. The precipitated crystals were filtered to give the desired product (20.1 g, yield 35%, melting point 267-271° C., Rf=0.68: chromatography on a silica gel thin layer using 5% ethanol-methylene chloride as the eluant).

Provenance & Evidence