The reaction of 3-(1-propylpiperidin-3(S)-yl)phenol (I) with trifluoromethanesulfonic anhydride gives the triflate (II), which is treated with Pd(OAc)4, CO and MeOH, yielding 3-(1-propylpiperidin-3(S)-yl)benzoic acid methyl ester (III). The reaction of (III) with sodium azide and H2SO4 affords the aniline (IV), which by reaction with NaNO2, HBr and CuBr provides 3(S)-(3-bromophenyl)-1-propylpiperidine (V). The reaction of (V) with dimethyl disulfide and n-BuLi gives the thioether (VI), which is oxidized with MCPBA to afford the target sulfone, which is easily separated from the N-oxide (VII) also formed in the oxidation process. The N-oxide (VII) can be reduced to the target compound by means of TiCl4 and NaI in acetonitrile.

The condensation of 3-(methylsulfonyl)bromobenzene (I) with diethyl(3-pyridyl)borane (II) by means of Pd(PPh3)4, KOH and tetrabutylammonium iodide (TBAI) gives 3-[3-(methylsulfonyl)phenyl]pyridine (III), which is hydrogenated with H2 over PtO2 in methanol, yielding the racemic piperidine (IV). The optical resolution of (IV) with (+)-tartaric acid affords the (S)-enantiomer (V), which is alkylated by reductocondensation with propionic aldehyde and NaBH(O-tBu)3 in dichloroethane and HOAc.

The reaction of 3-(1-propylpiperidin-3(S)-yl)phenol (I) with trifluoromethanesulfonic anhydride gives the triflate (II), which is treated with Pd(OAc)4, CO and MeOH, yielding 3-(1-propylpiperidin-3(S)-yl)benzoic acid methyl ester (III). The reaction of (III) with sodium azide and H2SO4 affords the aniline (IV), which by reaction with NaNO2, HBr and CuBr provides 3(S)-(3-bromophenyl)-1-propylpiperidine (V). The reaction of (V) with dimethyl disulfide and n-BuLi gives the thioether (VI), which is oxidized with MCPBA to afford the target sulfone, which is easily separated from the N-oxide (VII) also formed in the oxidation process. The N-oxide (VII) can be reduced to the target compound by means of TiCl4 and NaI in acetonitrile.

The reaction of 3-(1-propylpiperidin-3(S)-yl)phenol (I) with trifluoromethanesulfonic anhydride gives the triflate (II), which is treated with triisopropylsilylthiol sodium salt and Pd(PPh3)4 to yield the sill sulfanyl compound (III). The desilylation of (III) with HCl in methanol affords the thiophenol (IV), which is methylated with 13C- and 2H-labeled methyl iodide and TEA in dichloromethane, providing the methylsulfanyl derivative (V). Finally, this compound is oxidized to the target sulfone with MCPBA and trifluoroacetic acid.

The reaction of 3-(1-propylpiperidin-3(S)-yl)phenol (I) with trifluoromethanesulfonic anhydride gives the triflate (II), which is treated with triisopropylsilylthiol sodium salt and Pd(PPh3)4 to yield the sill sulfanyl compound (III). The desilylation of (III) with HCl in methanol affords the thiophenol (IV), which is methylated with 14C-labeled methyl iodide and TEA in dichloromethane, providing the methylsulfanyl derivative (V). Finally, this compound is oxidized to the target sulfone with MCPBA and trifluoroacetic acid.