Quaternary Ammonium, Phosphonium, and Tertiary Sulfonium Salts as Hydrogen‐Bonding Catalysts

A new supramolecular bonding motif involving NH bonds of ammonium salts and macrocycles derived from platinum corners and butadiynediyl linkers

“…It is also well established that the NCH hydrogen atoms of ammonium salts can serve as hydrogen bond donors. 14 Similarly close NCH⋯(CuC) centroid and NC⋯(CuC) centroid contacts are evident in the preceding crystal structures (see atoms and distances in red). For example, the shortest NH⋯ (CuC) centroid distances in 1•Ha + I − •1.62CH 2 Cl 2 are 2.61, 2.83, and 2.92 Å.…”

Trialkylphosphonium oxoborates as C(sp3)–H oxyanion holes and their application in catalytic chemoselective acetalization

“…6–8 Saturated hydrocarbons bearing C(sp 3 )–H NCHB donors were also found to serve as oxyanion holes 8 f and play a pivotal role in stabilizing negatively charged intermediates in catalysis, although the cases are limited. 9 For instances, alkylonium salts including alkylammonium 10 and alkylsulfonium 11 bearing C(sp 3 )–H can activate electron-donor substrates and enhance the reaction rates via NCHB interactions. Although the mechanistic evidence is unclear, some phosphonium salts 12 bearing C(sp 3 )–H could serve as acid catalysts and they are also believed to activate substrates via NCHB.…”