Hydrogen Bromide → 2-(Butan-2-yl)-4-{4-[4-(4-hydroxyphenyl)piperazin-1-yl]phenyl}-2,4-dihydro-3H-1,2,4-triazol-3-one

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Reaction Steps

A mixture of 29.4 g of (+)-(S)-(2,4-dihydro-4-[4-[4-(4-methoxyphenyl)-1-piperazinyl]-phenyl]-2-(1-methylpropyl)-3H-1,2,4-triazol-3-one, (S)-7,7-dimethyl-2-oxobicyclo[2.2.1]heptane-1-methanesulfonate (1:2) (intermediate (5)), 2.0 g of sodium sulfite and 151 ml of a hydrobromic acid solution 48% in water was stirred for 5 hours at reflux temperature. The reaction mixture was cooled to room temperature and water was added. The while was neutralized with potassium carbonate to pH 7 while stirring in a mixture of dichloromethane and 1-butanol (90:10 by volume). The separated organic layer was dried, filtered and evaporated in vacuo. The residue was triturated in methanol. The precipitated product was filtered off and purified by column chromatography over silica gel using a mixture of trichloromethane and methanol (98:2 by volume) as eluent. The pure fractions were collected and the eluent was evaporated. The residue was crystallized from 4-methyl-2-pentanone. The product was filtered off and dried, yielding 10.4 g (77.7%) of (+)-(S)-(2,4-dihydro-4-[4-[4-(4-hydroxyphenyl)-1-piperazinyl]-phenyl]-2-(1-methylpropyl)-3H-1,2,4-triazol-3-one; mp. 180.6° C.: [α]D20 =+4.38° (conc.=1% in methanol) (interm. 7).

Provenance & Evidence