Hydrogen Bromide → 3-[(4-Fluorophenyl)(1-methyl-4-piperidinylidene)methyl]pyridine

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Reaction Steps

A mixture of 240 parts of α-(4-fluorophenyl)-α-(1-methyl-4-piperidinyl)-3-pyridinemethanol and 900 parts of a hydrobromic acid solution 48% in water was stirred and refluxed for 1 hour. The whole was concentrated to one third of its volume. The concentrate was treated with a sodium hydroxide solution. The product was extracted with 4-methyl-2-pentanone. The extract was dried, filtered and evaporated. The residue was purified by column-chromatography over silica gel using a mixture of trichloromethane and methanol (90:10 by volume), saturated with ammonia, as eluent. The pure fractions were collected and the eluent was evaporated. The residue was crystallized from a mixture of petroleumether and a small amount of 2,2'-oxybispropane (10:1 by volume). The product was filtered off and dried, yielding 112.5 parts (48%) of 3-[(4-fluorophenyl)(1-methyl-4-piperidinylidene)methyl]pyridine; mp. 93.1° C. (intermediate 19).

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