Studies in sulfur‐nitrogen nucleophilicity

Abstract

As part of a study of nitrogen vs sulfur nucleophiles, the behavior of methylation products from dimethyl‐(2‐methylthioethyl)amine CH3SCH2CH2N(CH3)2 1 is described. Of the 2 potential products (a sulfonium salt or an ammonium salt), the ammonium salt from N‐methylation 2 dominated. The isomeric sulfonium salt 3 prepared by an independent route was found to be unstable and rearranged to the isomeric ammonium salt. The rearrangement pathway was investigated using deuterium‐labeled reactants. The sulfonium salt 3 also produced a piperazinium double salt 9 on heating. The reaction pathway was also followed by deuterium labeling. The results support the conclusion that production of the double salt 9 involves intermediate formation of N,N‐dimethylaziridium ion 4.

Zwitterionic Sulfonium Sulfonate Polymers: Impacts of Substituents and Inverted Dipole

“…For instance, the methyl protons adjacent to the sulfur cation resonate as two distinct singlets at 2.82 and 2.69 ppm, with equal intensities indicative of a lack of stereoselectivity associated with the ring-opening reaction. These results reinforce our prior studies using 3 in ring-opening reactions with amine and phosphine nucleophiles, , though the modest yields experienced when employing dialkyl sulfide nucleophiles, relative to tertiary amines and phosphines, may be attributed to their generally weaker nucleophilicity. , …”