N-Heterocyclic Carbene-Catalyzed [3+3] Cycloaddition Reactions for the Construction of Multifunctional 2-Pyranones

The unique heterocyclic structure and diverse reactivity of 2-pyranone underpin its broad utility in organic synthesis, polymer science, and medicinal chemistry. Its excellent chemical and physical properties have motivated extensive research into its synthesis and functionalization over recent decades. In recent years, organocatalysis has emerged as an effective strategy for constructing chiral and achiral heterocyclic compounds. Although N-heterocyclic carbene (NHC) catalysis enables efficient synthesis of some 2-pyranone derivatives, the structural diversity of accessible products remains limited by narrow substrate scope and a scarcity of reaction types. Here, we report an NHC-catalyzed [3 + 3] cyclization reaction that addresses this limitation. The optimized NHC catalyst facilitates this transformation under mild conditions, affording the desired products in good to excellent yields. Notably, the 2-pyranone analogues synthesized under the optimal conditions exhibit broad applicability and can be further converted into bi-aromatic frameworks.