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. [ABSTRACT FROM AUTHOR]