Process for the preparation of the pure Z isomer of 3-(4-bromophenyl)-N-methyl-3-(3-pyridyl)-allylamine

The pure Z isomer of 3-(4-bromophenyl)-N-methyl-3-(3-pyridyl)-allylamine of the formula (I) or one of its pharmaceutically acceptable acid addition salts is a highly selective inhibitor of the neuronal uptake of 5-hydroxytryptamine and can be used as antidepressants or neuroleptics. It is obtained by methylating a compound of the formula (V) The resulting mixture of stereoisomers is then, in the form of its acid addition salt, recrystallised several times from an organic solvent in which the two E and Z isomers display a considerably different solubility. The pure Z isomer of the formula (I) is obtained. In another preparation of the pure Z isomer of the formula (I), the starting compound used for the N-methylation is the pure Z isomer of the formula (V) which is obtained by recrystallisation of the mixture of stereoisomers of an acid addition salt of the compound of the formula (V) from an organic solvent.