Dual Chalcogen-Chalcogen Bonding Catalysis.

The noncovalent S···O bonding interaction is an evolutionary force that has been smartly exploited by nature to modulate the conformational preferences of proteins. The employment of this type of weak noncovalent force to drive chemical reactions is promising yet remains largely elusive. Herein, we describe a dual chalcogen-chalcogen bonding catalysis strategy that the distinct chalcogen atoms simultaneously interact with two chalcogen-based electron donors to give rise to the catalytic activity, thus facilitating chemical reactions. Conventional approaches to the Rauhut-Currier-type reactions require the use of strongly nucleophilic Lewis bases as essential promoters. The implementation of this dual chalcogen-chalcogen bonding catalysis strategy allows the simultaneous Se···O bonding interaction between chalcogen-bonding donors and an enone and an alcohol, enabling the realization of the Rauhut-Currier-type reactions in a distinct way. The further implementation of a consecutive dual Se···O bonding catalysis approach enables the achievement of an initial Rauhut-Currier-type reaction to give an enone product which further undergoes an alcohol-addition induced cyclization reaction. This work demonstrates that the nearly linear chalcogen-bonding interaction can differentiate similar alkyl groups to give rise to regioselectivity. Moreover, the new strategy shows its advantage as it not only enables less reactive substrates working efficiently but tolerates inaccessible substrates using conventional methods.

Chalcogen-Chalcogen Bonding Catalysis Enables Assembly of Discrete Molecules.

Despite the observation of noncovalent interactions between chalcogen atoms in X-ray crystal structures, catalysis that harnesses the power of such chalcogen-chalcogen bonding interactions to produce advanced molecules remains an unresolved problem. Here, we show that a class of extraordinary chalcogen-bonding catalysts enables assembly of discrete small molecules including three ß-ketoaldehydes and one indole, leading to the construction of N-heterocycles in a highly efficient manner. The strong activation ability of these rationally designed catalysts provides a general solution to the intrinsic limitations of chalcogen bonding catalysis.

Cooperative chalcogen bonding interactions in confined sites activate aziridines.

The activation of aziridines typically involves the use of strong Lewis acids or transition metals, and methods relying on weak interactions are rare. Herein, we report that cooperative chalcogen bonding interactions in confined sites can activate sulfonyl-protected aziridines. Among the several possible distinct bonding modes, our experiments and computational studies suggest that an activation mode involving the cooperative Se···O and Se···N interactions is in operation. The catalytic reactions between weakly bonded supramolecular species and nonactivated alkenes are considered as unfavorable approaches. However, here we show that the activation of aziridines by cooperative Se···O and Se···N interactions enables the cycloaddition of weakly bonded aziridine-selenide complex with nonactivated alkenes in a catalytic manner. Thus, weak interactions can indeed enable these transformations and are an alternative to methods relying on strong Lewis acids.