Nitrone Directing Groups in Rhodium(III)‐Catalyzed C−H Activation of Arenes: 1,3‐Dipoles versus Traceless Directing Groups

Functionalizable directing groups (DGs) are highly desirable in C−H activation chemistry. The nitrone DGs are explored in rhodium(III)‐catalyzed C−H activation of arenes and couplings with cyclopropenones. N‐tert ‐butyl nitrones bearing a small ortho substituent coupled to afford 1‐naphthols, where the nitrone acts as a traceless DG. In contrast, coupling of N‐tert ‐butyl nitrones bearing a bulky ortho group follows a C−H acylation/[3+2] dipolar addition pathway to give bicyclics. The coupling of N‐arylnitrones follows the same acylation/[3+2] addition process but delivers different bicyclics.