Chemistry Evolves, Terms Evolve, but Phenomena Do Not Evolve: From Chalcogen–Chalcogen Interactions to Chalcogen Bonding

Abstract

Chalcogen bonding is important in numerous aspects of chemistry, both in the solid state and in solution. Surveying the literature, it becomes clear that during its rebranding from chalcogen–chalcogen interactions, some parts of the community have somewhat neglected to recall its discovery and the initial studies referring to it in its previous guise. In this Viewpoint, we trace the path of research into this phenomenon, from its discovery, through its renaming, and to some of the varied and interesting chemistry it has led to so far, ranging from crystal engineering through supramolecular assembly to modern catalysis.

Chalcogen Bonding with Diaryl Ditellurides: Evidence from Solid State and Solution Studies.

“…The halogen bond (XB) is the archetype of such interaction, identified and then exploited in diverse areas such as organocatalysis, [1] medicinal chemistry [2] and crystal engineering, [3] to name a few. Together with earlier observations showing that chalcogen−chalcogen interactions are driving forces for the formation of superstructures in crystals of chalcogen‐rich organic compounds, [4] the XB reports have stimulated new studies concerning similar noncovalent interactions centered on other elements such as chalcogens (S, Se, Te) [5] . This led to term such interactions as chalcogen bond (ChB) in analogy to XB, and to recently define them as “a net attractive interaction between an electrophilic region associated with a chalcogen atom in a molecular entity and a nucleophilic region in another, or the same, molecular entity” [6] .…”

Enantioselective Synthesis of α‐Aryl‐β2‐Amino‐Esters by Cooperative Isothiourea and Brønsted Acid Catalysis

“…Reversible proton transfer from (R)-BTM•HCl to the hemiaminal ether generates the free isothiourea catalyst (for the Lewis base cycle) and the Nprotonated hemiaminal ether for the Brønsted acid cycle.I n the Brønsted acid cycle,p roton transfer generates I,w ith subsequent formation of the iminium ion chloride salt II.I n the Lewis base cycle, (R)-BTM can undergo reversible addition to the iminium ion II to give aminomethylated catalyst III as an off-cycle intermediate that is inconsequential to the outcome of the reaction. [38] Fort he constructive formation of the b-amino ester, N-acylationof(R)-BTM with the pentafluorophenyl ester generates an acyl ammonium pentafluorophenolate ion pair IV.Subsequent deprotonation generates the (Z)-C(1)-ammonium enolate V,with akey 1,5-O•••S contact, [39] that can be classified as either ac halcogenchalcogen interaction [40,41] or chalcogen bond (n O to s* C-S ), [42] providing ac onformational bias and ensuring coplanarity between the 1,5-O-and S-atoms.E nantioselective aminomethylation proceeds preferentially through reaction of the Re-face of the C(1)-ammonium enolate with the iminium ion II,l eading to intermediate VI.S ubsequent reaction with the pentafluorophenol generated in situ leads to the desired b 2amino ester and regenerates the isothiourea Lewis base and Brønsted acid catalysts.…”

Phosphine-Catalyzed Aryne Oligomerization: Direct Access to α,ω-Bisfunctionalized Oligo(ortho-arylenes)

“…This observation prompted us to decrease the reactivity of the electrophilic Se by electronic means. From our previous work in noncovalent chalcogen bonding, we were aware of strong interactions of the oxygen atoms of NO 2 groups with positively polarized selenium . Thus, we employed 2-nitrophenyl selenocyanate in combination with aryne precursor 2a .…”