Ammonium Chloride → Prazosin Hydrochloride

HRID 1680075Notes

Reaction equation

C[N:2]([C:18]1[C:23]([C:24]#[N:25])=[CH:22][C:21]([O:26][CH3:27])=[C:20]([O:28][CH3:29])[CH:19]=1)[C:3]([N:5]1[CH2:10][CH2:9][N:8]([C:11]([C:13]2[O:14][CH:15]=[CH:16][CH:17]=2)=[O:12])[CH2:7][CH2:6]1)=S.[Cl-:30].[NH4+:31]>C(N)=O>[CH3:27][O:26][C:21]1[CH:22]=[C:23]2[C:24]([NH2:25])=[N:31][C:3]([N:5]3[CH2:6][CH2:7][N:8]([C:11]([C:13]4[O:14][CH:15]=[CH:16][CH:17]=4)=[O:12])[CH2:9][CH2:10]3)=[N:2][C:18]2=[CH:19][C:20]=1[O:28][CH3:29].[ClH:30]

Participants

Conditions

Temperature: 120 °C

Procedure

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.

Workup

stirringwhile stirring
customalso feeding nitrogen gas in order to remove the methane thiol
customproduced (
customcan be absorbed into a sodium hypochlorite solution)

Sources & evidence

ORD record: ord-dba157b9f2c3411da9795821d6e6de19
Source dataset: uspto-grants-1981_06
DOI: 10.6084/m9.figshare.5104873.v1
Patent number: US04271300

Reaction notes

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