New chiral sulfoxides (R-S, S)-3, (S-S, S)-3, (R-S, S)-4, and (S-S, S)-4 and known chiral sulfoxides (R-S)5, (R-S)-6, and (R-S)-7 were synthesized, and the stereochemistry of the new sulfoxides (R-S, S)-3 and (R S, S)-4 was determined by X-ray crystallographic analysis. In their crystallographic structures, the intramolecular nonbonded S center dot center dot center dot O close contacts were recognized. Analyses of several sulfoxide complexes including rac-11 with N, N-dimethylacetamide (DMAC) or N-methyl-2-pyrrolidone (NMP) in a MeOH solution utilizing cold-spray ionization mass spectrometry provided, for the first time, direct information for intermolecular nonbonded S center dot center dot center dot O interactions between sulfoxides and amide (or lactam) in a solution. Highly diastereoselective and enantioselective Pummerer reactions based on the concept of intermolecular and intramolecular nonbonded S center dot center dot center dot O interactions were performed by treatment of several chiral sulfoxides (R-S, S)-3, (S-S, S)-3, (R-S, S)-4, (S-S, S)-4, (R-S)-5, (R-S)-6, and (R-S)-7 with acetic anhydride and trimethylsilyl triflate (TMSOTf) in DMAC, NMP, N, N-dimethylformamide, and N-formylpiperidine. Mechanistic studies on these facile stereoselective Pummerer reactions revealed the necessity for the amide/TMSOTf complex, such as 26 or 27, to be an efficient activation reagent for Ac2O and a trapping reagent for the released acetate ion, and that DMAC and NMP had a positive effect on this highly stereoselective chiral transfer reaction.