Ruthenium Catalyzed Formal [4 + 2] C-H Annulation to Pyranone via Chemoselective Ester Demethylation/O-C Cleavage.

In this study, we delineate a highly efficient and operationally robust Ru(II)-catalyzed chemoselective ester demethylation/O-C cleavage enabled C-H annulation protocol for the expedient construction of pyranone architectures from readily accessible acrylates and internal alkynes. The transformation is postulated to proceed via Ru(0)-complex, intricately coordinated by p-cymene and the emergent pyranone scaffold. This catalytic paradigm is distinguished by a carboxylate-assisted C-H activation, subsequent formation of a thermodynamically stabilized sandwich Ru(0) intermediate, and a mechanistically intriguing chemoselective O-Me/Et bond scission of the ester moiety, collectively orchestrating the annulation sequence. A comprehensive exposition of this protocol underscores its synthetic efficacy and broad-spectrum applicability in the streamlined synthesis of pyranone frameworks.