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

Abstract

Functionalizable directing groups (DGs) are highly desirable in C À Ha ctivation chemistry.T he nitrone DGs are explored in rhodium(III)-catalyzed CÀHa ctivation of arenes and couplings with cyclopropenones.N -tert-butyl nitrones bearing as mall ortho substituent coupled to afford1 -naphthols,w here the nitrone acts as at raceless DG.I nc ontrast, coupling of N-tert-butyl nitrones bearing ab ulkyortho group follows aC À Ha cylation/[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.

I2-Mediated Iodobenzannulation of Yne-Allenones toward 1-Naphthols and Their Synthetic Application

“…In addition, the rhodium-catalyzed redox-neutral benzannulation of nitrones with cyclopropenones provided an alternative pathway to form 1-naphthols (Scheme 1b). 12 However, the use of the transition metals in these procedures is generally thought not to be environmentally friendly, especially when these 1-naphthols serve as pharmaceutically active ingredients, since they are typically allowed with a low level of the heavy metal content, thereby encountering a challenging problem in the removal of heavymetal catalysts from the final products. Very recently, Wang and co-workers reported metal-free bromide-mediated intermolecular benzannulation of phenylethanones with alkynes for 1-naphthol synthesis but with the requirement of a stoichiometric amount of oxidants (Scheme 1a).…”

Catalyst‐Controlled Regiodivergent Alkyne Insertion in the Context of C−H Activation and Diels–Alder Reactions: Synthesis of Fused and Bridged Cycles

“…[4] Given the power of cycloaddition reactions in synthesis of cyclic products,i ti sd esirable to integrate CÀH activation with cycloaddition reactions.H owever,e xamples are rather limited. [5] We recently reported aC À Ha ctivation/intramolecular 1,3-dipolar addition assisted by an itrone directing group (DG). [5c] Despite the progress,o nly dipolar addition was accommodated because of the specificity of the DG.Thus,we resorted to the combination of CÀHa ctivation with Diels-Alder (DA) reactions to solve the limitation.…”

Synthesis and Transformations of Nitrones for Organic Synthesis

“…224 Rhodium-catalyzed reaction of arylnitrones with cyclopropenones affords 1-naphthols (eq 90). 225 Similar rhodium-catalyzed reaction of C-benzoylnitrones with alkynes provides a redox-neutral naphthol synthesis (eq 91). 226 Rhodium-catalyzed C−H activation of N-arylnitrones and coupling with diazo compounds affords different indole derivatives depending on the additives.…”