Palladium-Catalyzed Cyclizative Borylation of Allenyl Ketones through Carbene Boryl Migratory Insertion: Access to Densely Substituted Furyl Boronates.

Herein the palladium-catalyzed cyclizative borylation of allenyl ketones with diboron compounds is reported which involves the carbene boryl migratory insertion as the key step. This reaction features mild conditions, good functional group tolerance and broad substrate scope. Thus, it represents an efficient methodology for the assembly of diverse tri-substituted furyl boronates. In addition, a series of transformations of the resultant multi-substituted furyl boronates were conducted to provide various densely substituted furan derivatives in good yields, further illustrating the potential synthetic utility of this methodology.