Chalcogen Bonding Catalysis Enables Ring-Opening of Cyclopropene and Ring Expansion of Aryl Ketones.

Catalytic transformation of carbene species constitutes a fundamental part in organic synthesis, and the research in this direction has been dominated by transition metals while organic catalysts are difficult to mimic such transition-metal-like reactivity. It would significantly advance carbene chemistry if organic catalysts enable achieving classical metal-carbene approaches otherwise unrealizable reactions. Herein, we report that chalcogen bonding catalysis can solve reactivity problem to achieve an elusive Buchner ring expansion of aryl ketones appending a cyclopropene moiety as carbene precursor. In this work, the ring-opening of cyclopropene and the ring-expansion of aryl systems were added in the field of noncovalent catalysis. This work demonstrates that chalcogen bonding can mediate carbene transformations beyond the known ionic approach. In contrast, transition metals such as rhodium, palladium, and copper complexes, could not solve the reactivity problem to achieve ring expansion of aryl ketones but instead these metal-carbene approaches prefer the formation of furan side product. In addition, a thermal approach even being conducted at 200 °C could not achieve this ring expansion reaction. Mechanistic investigation suggests Se⋅⋅⋅π interaction with cyclopropene facilitates the ring-opening of cyclopropene and chalcogen bonding with carbene intermediate changes the reaction pathway, thus overriding the furan reaction pathway.