Hydrogen Bromide → Methyl 5-(piperazin-1-yl)benzofuran-2-carboxylate

Participants

Reaction Conditions

Reaction Steps

Methyl 5[4-(benzenesulfonyl)-1-piperazinyl]benzofuran-2-carboxylate (30 g) was added to a solution of hydrobromic acid in acetic acid (180 ml) and 4-hydroxybenzoic acid (24 g). The resulting mixture was stirred for 5 minutes at 25-30° C., followed by heating the mixture to 80-85° C. and maintaining for 6 hours at the same temperature. The reaction mass was poured into methanolic HCl (1000 ml), followed by heating to reflux and then stirring for 6 hours under reflux. The resulting mass was cooled to 0-5° C. and then stirred for 1 hour at the same temperature. The separated solid was filtered and washed with chilled methanol (100 ml). The wet solid was added to methanolic HCl (500 ml) and then heated to reflux for 4 hours. The resulting mass was cooled to 0-5° C. and then stirred for 1 hour at the same temperature. The separated solid was filtered, washed with chilled methanol (100 ml) and then dried at 60-65° C. The resulting solid was added to toluene (500 ml) at 25-30° C., followed by purging ammonia gas slowly for 7 hours. After completion of the ammonia gas purging, the reaction mass was stirred for 15 minutes at 25-30° C. The resulting mass was filtered and the filtrate was distilled to produce 16 g of methyl 5-(1-piperazinyl)benzofuran-2-carboxylate (Purity by HPLC: 99.5%; Yield: 82.5%).

Provenance & Evidence