Palladium(II)-Catalyzed Cross-Coupling of Diazo Compounds and Isocyanides to Access Ketenimines

Diazo compounds and isocyanides are reactive functionalities and valuable building blocks commonly utilized in organic synthesis. Their cross-coupling for the synthesis of useful isolable ketenimines remains an unsolved challenge in synthetic chemistry. Herein, we report a general method for the preparation of ketenimines via a palladium-catalyzed cross-coupling of easily accessible diazo compounds with isocyanides. The reaction benefits from the use of readily available starting materials, a wide substrate scope, high functional group tolerance, and a high yield in products, and the resultant ketenimines are amenable to further functionalization. Experimental findings and DFT calculations unambiguously corroborate the initial formation of a Pd(II)-isocyanide complex as the active catalytic species, which enables the cross-coupling reaction via a migratory insertion of Pd(II)-carbene into isocyanide, with evidence suggesting that the oxidation state of Pd(II) remains unchanged during the reaction.