Stereochemistry of organic sulfur compounds Part 20

Synthesis and conformational analysis of 1-phenyl-2-methylsulfinyl-(and -sulfonyl-) ethylamine (and its N -methyl and N , N -dimethylderivatives) are reported. Conformational preferences have been determined by carefully observing the changes of the vicinal coupling constants with protonation in the 1H-nmr spectra. The strongly configuration dependent conformational behavior displayed by sulfoxides is explained in terms of a previously proposed donor-acceptor interaction between nitrogen and sulfur. Conformational equilibria of sulfones are controlled by steric interactions except when nitrogen is protonated in which case a relatively weak electrostatic attraction takes place between the heteroatomic functions.