The Palladium-Catalyzed Assembly and Functionalization of Benzo[b]furans

In the past decades, the great potential of palladium catalysis has been widely used in the de novo construction of the functionalized benzo[b]furan ring and in the selective functionalization of the preformed benzo[b]furan system providing a broad range of new and versatile procedures. The de novo construction of the benzo[b]furan system generally involves the assembly of the furan nucleus on a benzenoid scaffold via intramolecular or intermolecular cyclization of compounds containing oxygen nucleophiles and carbon-carbon triple bonds or carbon-carbon double bonds. Other less frequently used de novo syntheses of the benzo[b]furan system are based on the intramolecular Buchwald/Hartwig C-O bond forming process and the construction of the benzenoid ring on a furan scaffold. The functionalization of the preformed benzo[b]furan system is usually based on the functionalization via benzofuryl halides or triflates and the functionalization via organometallic derivatives such as benzofurylstannanes, benzofurylboronic acids and benzofurylzinc compounds. Functionalization via direct activation of C-H bonds has also been described.