Catalytic Synthesis of Cyclopropenium Cations with Rh-Carbynoids

Herein, we report the first catalytic one-step synthesis of cyclopropenium cations (CPCs) with readily available alkynes and hypervalent iodine reagents as carbyne sources. Key to the process is the catalytic generation of a novel Rh-carbynoid that formally transfers monovalent cationic carbynes (:C+-R) to alkynes via an oxidative [2+1] cycloaddition. Our process is able to synthesize a new type of CPC substituted with an ester group that underpins the regioselective attack of a broad range of carbon and heteroatomic nucleophiles, thus providing a new platform for the synthesis of valuable cyclopropenes difficult or not possible to make by current methodologies.

Automated summary

In this study, a catalytic one-step synthesis of cyclopropenium cations using readily available alkynes and hypervalent iodine reagents as carbyne sources is reported. A novel Rh-carbynoid catalytically generates monovalent cationic carbynes (:C+-R), which are then transferred to alkynes via an oxidative [2+1] cycloaddition, resulting in a new type of ester-substituted CPC. This method allows for regioselective attack of various carbon and heteroatomic nucleophiles, providing a new platform for the synthesis of valuable cyclopropenes that are difficult or impossible to make by current methodologies.