Halonium, chalconium, and pnictonium salts as noncovalent organocatalysts: a computational study on relative catalytic activity

Abstract

This theoretical study sheds light onto the relative catalytic activity of pnictonium, chalconium, and halonium salts in the reactions involving elimination of the chloride and electrophilic activation of the carbonyl...

(Pre)association as a crucial step for computational prediction and analysis of the catalytic activity of σ-hole donating organocatalysts

“…It has been unambiguously shown that the catalytic activity of XB and ChB donors has similar trends, namely the increase of the catalytic activity from the lighter to heavier halogen or chalcogen σ-hole carriers, 16 and a significantly higher activity for the cationic species (Fig. 1, C-D) compared to the uncharged catalysts A and B.…”

Synthetic application of chalcogenonium salts: beyond sulfonium

“…The same group has disclosed density-functional theory (DFT) calculations for the hydrolysis of methyl chloride and the addition of ammonia to acetone promoted by chalcogenonium salts 75 (Scheme 39). 64 In the bimolecular substitution reaction, the transition state was found to proceed via a bifurcate Ch⋯Cl⋯H interaction 75′ , being the activity progressively increased from the sulfonium to the telluronium cation. The relative reactivity of chalcogens remains the same for the nucleophilic addition of ammonia to acetone; however, the transition state 75′′ shows further stabilization by a weak interaction of the H atom from NH 3 with the phenyl ring.…”

“…Within the chalcogen family, the activity increases from sulfur to tellurium, again in connection with the deepening of σ holes, associated in part with the greater electropositivity and polarizability of tellurium when compared to sulfur or selenium. 63–65 a Finally, the catalytic activity of chalcogenonium salts can be conveniently modulated in an electronic environment surrounding the chalcogen atom and by the utilization of less coordinating counteranions. 60,68…”

Cooperative Catalysis Involving Hydrogen and Halogen Bond Donors: A Computational Study on the Thiourea–Iodonium System

“…[47][48][49] We have chosen this functional according to our previous experience and its successful performance in a number of halogen and chalcogen bonds studies in various similar supramolecular systems and organocatalysis processes. 40,42 The quasi-relativistic MWB46 pseudopotentials, 50 which described 46 core electrons, and the appropriate contracted basis sets were used for iodine atoms, while the standard 6-31G* basis sets were used for other atoms. No symmetry restrictions were applied during the geometry optimizations.…”

“…22 In addition, this reaction has been studied by us previously for many other noncovalent organocatalysts (Figure 2). 29,40,41 -------------------------------------------------As model catalytic species, methylbenziodolium 1 has been chosen as XB donating representative, whereas N,N'-dimethyl derivatives of urea 2, thiourea 3, and squaramide 4 has been selected as the HB donors.…”