Diverse ortho-C(sp2)-H Functionalization of Benzaldehydes Using Transient Directing Groups.

Pd-catalyzed C-H functionalizations promoted by transient directing groups remain largely limited to C-H arylation only. Herein, we report a diverse set of ortho-C(sp2)-H functionalizations of benzaldehyde substrates using the transient directing group strategy. Without installing any auxiliary directing group, Pd(II)-catalyzed C-H arylation, chlorination, bromination, and Ir(III)-catalyzed amidation, could be achieved on benzaldehyde substrates. The transient directing groups formed in situ via imine linkage can override other coordinating functional groups capable of directing C-H activation or catalyst poisoning, significantly expanding the scope for metal-catalyzed C-H functionalization of benzaldehydes. The utility of this approach is demonstrated through multiple applications, including late-stage diversification of a drug analogue.