Chalcogen Bonding Catalysis with Phosphonium Chalcogenide (PCH)

Abstract

Metrics & MoreArticle Recommendations CONSPECTUS:The exploration of new catalysis concepts and strategies to drive chemical reactions is of vital importance for the sustainable development of organic synthesis. Recently, chalcogen bonding catalysis has emerged as a new concept for organic synthesis and has been demonstrated to be an important synthetic tool capable of addressing elusive reactivity and selectivity issues. This Account describes our progress in the research field of chalcogen bonding catalysis, including (1) the discovery of phosphonium chalcogenide (PCH) as highly efficient chalcogen bonding catalyst;(2) the development of "chalcogen−chalcogen bonding catalysis" and "chalcogen•••π bonding catalysis" modes;(3) the demonstration that chalcogen bonding catalysis with PCH can activate hydrocarbons to achieve cyclization and coupling reactions of alkenes; (4) the discovery of unusual results that chalcogen bonding catalysis with PCH can solve elusive reactivity and selectivity issues that are inaccessible by classic catalysis approaches; and (5) the elucidation of chalcogen bonding mechanisms.With PCH catalysts, we systematically studied their chalcogen bonding properties, the relationship between structure and catalysis, and their application in facilitating a diverse array of reactions. Enabled by chalcogen−chalcogen bonding catalysis, an efficient assembly reaction of three molecules of β-ketoaldehyde and one indole derivative in a single operation was realized, delivering heterocycles with a newly constructed seven-membered ring. In addition, a Se•••O bonding catalysis approach achieved an efficient synthesis of calix[4]pyrroles. We developed a "dual chalcogen bonding catalysis" strategy to solve reactivity and selectivity issues in the Rauhut−Currier-type reactions and related cascade cyclizations, thus shifting conventionally covalent Lewis base catalysis to a cooperative Se•••O bonding catalysis approach. This strategy enables the cyanosilylation of ketones to take place in the presence of a ppm-level amount of PCH catalyst loading. Furthermore, we established chalcogen•••π bonding catalysis for catalytic transformation of alkenes. In the research field of supramolecular catalysis, the activation of hydrocarbons such as alkenes by weak interactions is a highly interesting unresolved topic. We showed that the Se•••π bonding catalysis approach could efficiently activate alkenes to achieve both coupling and cyclization reactions. Chalcogen•••π bonding catalysis with PCH catalysts is particularly highlighted by the capability of facilitating strong Lewis-acid inaccessible transformations, such as the controlled cross coupling of triple alkenes. Overall, this Account presents a panoramic view of our research on chalcogen bonding catalysis with PCH catalysts. The works described in this Account provide a significant platform to solve synthetic problems.

Selective Activation of Chalcogen Bonding: An Efficient Structuring Tool toward Crystal Engineering Strategies

“…Under these circumstances, we expect a differentiation of the two σ-holes up to a point where the strongest one will essentially control the supramolecular organization of cocrystals, in a way similar to that observed with XB. As illustrated in Figure b, this approach has been already used in cationic ChB donors aimed at interacting with different neutral or anionic Lewis bases toward anion recognition effects or organo-catalysis applications. − …”

Halogen effect in photomechanical molecular crystals

“…This heavy-atom effect is beneficial for phosphorescence. 56,57 It has also been found that halogen atoms endow an interesting ''halogen effect'' in tuning the selfassembling and functional properties, such as gelation, 58 mechanofluorochromism (MFC), 59 aggregation-induced emission (AIE), 60,61 room-temperature phosphorescence (RTP), thermally activated delayed fluorescence (TADF), [62][63][64] near-infrared fluorescence, 65 sensing, 66 supramolecular structures 67 and crystalline structures. 68 Considering that halogens can be used as a useful crystal engineering tool for topological chemical reactions, 69 the halogen effect plays a more indispensable role in fabricating photomechanical organic crystals.…”

Exploiting π and Chalcogen Interactions for the β‐Selective Glycosylation of Indoles through Glycal Conformational Distortion

“…Differing from XB, each chalcogenide atom is capable of establishing two sigma holes, which could confer ChB catalysts unique activation manifolds inaccessible through XBs. In particular, a privileged class of phosphonochalcogenide catalysts [9] developed by Wang and co‐workers has gained significant attention lately owing to the robustness of this catalyst across different reaction classes (Figure 1B). To date, the predominant proposed mode of activation of such catalysts solely involved Lewis acidity through the sigma holes of the selenium atoms, [10] which can be harnessed to activate electrophiles, such as carbonyl motifs.…”