Ammonium Chloride → Prazosin Hydrochloride

Participants

Reaction Conditions

Reaction Steps

275 g (0.66 moles) of methyl-N-(3,4-dimethoxy-6-cyanophenyl)-[4-(2-furoyl)-1-piperazinyl]thioformamidate is dissolved in 3000 ml of formamide, and 1375 g (25.7 moles) of ammonium chloride is added while stirring. Thereafter, the reaction mixture is heated for 15-20 hours at 120° C., while stirring and also feeding nitrogen gas in order to remove the methane thiol produced (can be absorbed into a sodium hypochlorite solution). The prazosine hydrochloride produced gradually crystallizes out from the reaction mixture. After the reaction has ceased, 3-4 kg of ice is added to the mixture. The product is filtered, washed with cold water and acetone, and dried. Yield 254-259 g (93-95%). Purity 99.5% (HPLC). The product is crystallized out from about 10 liters of a mixture of water and ethanol (15:50). Yield 232-235 g (85-86%). Purity 99.7-99.8% (HPLC). The IR, NMR and mass spectra of the product are identical to the corresponding spectra of prazosine hydrochloride produced by methods previously described in the literature.

Provenance & Evidence