Synthesis, Structure, and Properties of Unsaturated Thiacrown Ethers Possessing Sulfonium Groups

Thiacrown ethers have attracted much attention in host‐guest chemistry. Herein, we present the polymethylation reactions of unsaturated thiacrown ethers. Unsaturated thiacrown ethers having sulfonium groups were synthesized by the reaction of corresponding unsaturated thiacrown ethers with methyl triflate. The obtained methylated unsaturated thiacrown ethers were characterized by single‐crystal X‐ray diffraction analysis, UV absorption measurement, and cyclic voltammetry. The occupied and unoccupied molecular orbitals of the obtained methylated unsaturated thiacrown ethers are essentially localized respectively around the sulfide groups and the sulfonium groups. Furthermore, the results of electrostatic potential maps indicated that positive charges were distributed throughout the entire unsaturated thiacrown ether moieties. The methylation reactions of unsaturated thiacrown ether with methyl triflate proceeded to give mono‐ and dimethylated unsaturated thiacrown ether. The stereochemistry of the obtained products were determined by single‐crystal X‐ray diffraction analysis. The positive charges of the products were found to distribute throughout the entire unsaturated thiacrown ether moieties by calculation of electrostatic potential maps.