Examining the Alkaline Stability of Tris(dialkylamino)sulfoniums and Sulfoxoniums.

Herein, a synthetic method was developed to prepare a series of tris(dialkylamino)sulfonium and sulfoxonium cations from sulfur monochloride. Alkaline stability studies of these two cation families in 2 M KOH/CD3OH solution at 80 °C revealed how degradation pathways change as a function of the oxidation state of the S center, as determined by 1H NMR spectroscopy. The sulfonium cations (+S(NR2)3) typically degrade by nucleophilic attack at the sulfur atom with loss of an amino group and a proton transfer reaction to produce sulfoxides, while the sulfoxoniums (+O═S(NR2)3) tend to degrade by loss of an R group to form sulfoximines. From the group of sulfoniums and sulfoxoniums explored in this work, the tris(piperidino)sulfoxonium cation was noted to have excellent alkaline stability. This sulfoxonium should be suitable for future examination as a tethered cation in anion-exchange membranes (AEMs), or as a phase-transfer catalyst in biphasic reactions.

Multicompartment Polymeric Nanoreactors for Non-Orthogonal Cascade Catalysis.

Spatial confinement of multiple catalysts presents an effective strategy for performing sequential or tandem chemical transformations in a one-pot reaction. These methods may be used to catalyze numerous reactions in conditions that are otherwise incompatible between catalyst and solvent, different catalysts, or reagents. Appropriate site isolation or support structure design will lead to significant advantages in atom economy, purification, and costs; the development of the interface between a catalyst and its confined microenvironment is paramount for realizing the next generation of nanoreactors. Polymer scaffolds can create tailor-made microenvironments resulting in catalyst compartmentalization. Through the optimization of a number of variables such as size, solubility, functionality, and morphology of the nanoreactor, catalyst activity and selectivity can be tuned. In this feature article, design principles and early strategies for polymer supports for catalyst site-isolation are introduced, and current strategies toward multicompartment polymer nanoreactors for non-orthogonal cascade catalysis are discussed. Future design trends in this burgeoning field are outlined in the conclusion.

Tetrakis(dialkylamino)phosphonium Polyelectrolytes Prepared by Reversible Addition-Fragmentation Chain Transfer Polymerization.

A tetrakis(dialkylamino)phosphonium cation ([P(NR2)4]+) was appended to a styrenic monomer and explored in reversible addition-fragmentation chain transfer polymerization (RAFT) to conduct random copolymerizations of the cationic monomer with styrene. Well-defined polyelectrolytes with molecular weights up to ∼30 100 and dispersities between ∼1.2 and 1.4 were obtained. Up to 18.9 mol % of the ionic monomer could be incorporated into the polymer with hexafluorophosphate or bis(trifluoromethane)sulfonimide acting as the counterion during polymerization. Differential scanning calorimetry of the hexafluorophosphate polymers revealed glass transition temperatures higher than polystyrene likely due to interactions between the anion and the polymer. Thermogravimetric analysis indicated these materials have high thermal stability with decomposition temperatures approaching 400 °C.