The methylation of 2-methyl-3-propyl-3-(3-methoxyphenyl)-1-pyrroline (I) with dimethyl sulfate in refluxing butanone gives 1-methyl-3-propyl-2-exo-methylene-3-(3-methoxyphenyl)pyrrolidine (II), which by reaction with HBF4 in ethanol is converted into 1,2-dimethyl-3-propyl-3-(3-methoxyphenyl)pyrrolinium tetrafluoroborate (III). The methylation of (III) with diazomethane in dichloromethane ether yields 1,2-dimethyl-3-propyl-3-(3-methoxyphenyl)-1,2-ethylenepyrrolidinium tetrafluoroborate (IV), which by heating at 180 C and neutralization with NaOH affords 1,3-dimethyl-4-propyl-4-(3-methoxyphenyl)-1,4,5,6-tetrahydropyridine (V). The reduction of (V) with NaBH4 in THF gives 1,3-dimethyl-4-propyl-4-(3-methoxyphenyl)piperidine (VI), which is finally treated with 48% HBr in refluxing acetic acid.

The methylation of 2-methyl-3-propyl-3-(3-methoxyphenyl)-1-pyrroline (I) with dimethyl sulfate in refluxing butanone gives 1-methyl-3-propyl-2-exo-methylene-3-(3-methoxyphenyl)pyrrolidine (II), which by reaction with HBF4 in ethanol is converted into 1,2-dimethyl-3-propyl-3-(3-methoxyphenyl)pyrrolinium tetrafluoroborate (III). The methylation of (III) with diazomethane in dichloromethane ether yields 1,2-dimethyl-3-propyl-3-(3-methoxyphenyl)-1,2-ethylenepyrrolidinium tetrafluoroborate (IV), which by heating at 180 C and neutralization with NaOH affords 1,3-dimethyl-4-propyl-4-(3-methoxyphenyl)-1,4,5,6-tetrahydropyridine (V). The reduction of (V) with NaBH4 in THF gives 1,3-dimethyl-4-propyl-4-(3-methoxyphenyl)piperidine (VI), which is finally treated with 48% HBr in refluxing acetic acid.