Rh(III)-catalyzed C-H [4 + 2] annulation of oximes with (hetero)cyclic iodonium ylides to access pyrano[4,3-b]pyridin-5one derivatives

Abstract

We herein report a Rh(III)-catalyzed C-H [4 + 2] annulation of oximes with iodonium ylides, enabling efficient access to medicinally valuable pyrano [4,3-b]pyridin-5-one derivatives. This external oxidant-free approach demonstrates broad applicability across electronically diverse aryl oximes, vinyl oximes, and heterocyclic iodonium ylides. The reaction offers several advantages, including the use of readily accessible starting materials, excellent functional group tolerance, operational simplicity, and scalability. Importantly, the power of this approach is further illustrated by the late-stage functionalization of complex molecule, as well as the concise synthesis of a tricyclic pyrone derived from (S)-perillaldehyde, which exhibits promising MC65 cell protective activity. Mechanism studies indicate that the release of a peroxide species is involved in the [4 + 2] annulation process.