Scalable Multicomponent Synthesis of (Hetero)aryl-Substituted Phenyls: Focus on Metal-Free Halogenated Biaryls, 3-Arylindoles, and Isourolithine A Synthesis

In the context of the growing interest of the scientific community for the development of sustainable synthetic strategies to access aromatic structures, we present a practical and metal-free approach to (hetero)biaryls which exploits the advantages of multicomponent reactions in sustainable solvents. In situ acid-catalysed generation of (hetero)aryl acetoxy dienes from the corresponding (hetero)arylidene acetones in a metal vessel, followed by Diels-Alder reaction using an electron-poor alkyne as dienophile, delivers the expected aromatic products after final oxidation of the cycloadduct. This protocol has been demonstrated as a convenient alternative to the previously reported synthetic strategies, considering its scalability and environmental sustainability and the low cost of substrates and equipment. Moreover, it has been successfully applied to the metal-free regioselective synthesis of (hetero)aryl-substituted-phenyls, 2-unsubstituted-3-aryl-indoles, and to the total synthesis of isourolithine A.