Rh-Catalyzed Formal [3 + 2] Cycloaddition Reactions with Cyclopropenones via Sequential C-H/C-C Bond Activation.

The utilization of high-valent metal catalysts to promote cycloaddition reactions involving π bonds through C-C bond activation remains challenging. Despite extensive research, the cycloaddition of aldehydes with cyclopropenones catalyzed by metal complexes has not been documented. Herein, we disclose a novel Rh(III)-catalyzed cycloaddition reaction between cyclopropenones and aldehydes, enabling the efficient synthesis of highly functionalized furanones. A detailed mechanistic investigation was conducted, revealing the likely involvement of a tripodal Rh-carbene intermediate in the catalytic cycle, which facilitates the product release pathway. This reaction exhibits a broad substrate scope, good functional group compatibility, and high atom economy, thereby offering a versatile and general approach to the construction of furanones.