Design and Applications of Cyclopropenium Chalcogen Dihalides in Catalysis via C(sp 3 )–H···X Interactions

Noncovalent interactions originated from C­(sp 3 )–H···X hydrogen bonds frequently appear in different areas such as crystal engineering, protein binding, and supramolecular chemistry. However, employing this class of C­(sp 3 )–H···X interactions in catalysis is less common because they often offer insufficient catalytic performance due to their relatively weak strength. Herein, we report the use of cyclopropenium chalcogen dihalides as catalysts, in which effective site isolation of the counteranion significantly enhances the availability of the noncovalent interaction donor. The catalytic performance is comparable to those of some typical Lewis acids and much better than those of many common catalysts based on noncovalent interactions. Our mechanistic study suggests that the catalysts activate substrates via multiple C­(sp 3 )–H···X hydrogen bonds.