Palladium(II)-Catalyzed Cross-Coupling of Diazo Compounds and Isocyanides to Access Ketenimines
Zhaohong Liu, Shanshan Cao, Jiayi Wu, Giuseppe Zanoni, Paramasivam Sivaguru, Xihe Bi
Abstract
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.