Hydrochloric Acid → 4-[4-(3,4-dihydro-2H-quinoxalin-1-yl)phenyl]piperazine-1-carboxylic acid benzyl ester

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Reaction Steps

8.9 g of 4-[4-(4-(benzyloxycarbonyl)piperazin-1-yl)phenyl]-3,4-dihydro-2H-quinoxaline-1-carboxylic acid tert-butyl ester are placed in 220 ml of dichloromethane. 55 ml of a 4N solution of hydrochloric acid in dioxane are slowly added at 0° C. The mixture is stirred for 5 minutes under cold conditions and then it is allowed to return to ambient temperature. The reaction mixture is stirred at ambient temperature for 18 h and is then diluted with dichloromethane. A saturated aqueous sodium carbonate solution is added and then the addition is continued with solid sodium carbonate until a pH=7-8 is reached. The aqueous phase is extracted with dichloromethane. The organic phases are combined, washed with water, dried over sodium sulphate, filtered through a sintered glass filter and concentrated under vacuum. 7.2 g of 4-[4-(3,4-dihydro-2H-quinoxalin-1-yl)phenyl]piperazine-1-carboxylic acid benzyl ester are obtained in the form of an oil.

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