Site‐Selective C−H Functionalization of Carbazoles

Carbazole alkaloids are of great interest to organic and medicinal chemists and material scientists. This unique direct C−H functionalization has enabled efficient derivatization of commercially available carbazoles in a highly site-selective manner via a unique six-membered palladacycle intermediate. This reaction boasts good functional group compatibility and displays distinct reactivities based on C3-substituents of unsymmetrical substrates.

Abstract

Carbazole alkaloids hold great potential in pharmaceutical and material sciences. However, the current approaches for C1 functionalization of carbazoles rely on the use of a pre-installed directing group, severely limiting their applicability and hindering their overall efficiency. Herein, we report for the first time the development of direct Pd-catalyzed C−H alkylation and acylation of carbazoles assisted by norbornene (NBE) as a transient directing mediator. Notably, the involvement of a six-membered palladacycle intermediate was suggested in this case, representing the first example of such intermediacy within the extensively studied Pd/norbornene reactions realm.

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