Rhodium(III)‐Catalysed Carbenoid C(sp2)–H Functionalisation of Aniline Substrates with α‐Diazo Esters: Formation of Oxindoles and Characterisation/Utility of an Intermediate‐Like Rhodacycle

An efficient RhIII-catalysed reaction of 2-anilinopyridines with sulfonylated α-diazo esters under mild conditions gave oxindole derivatives, while an analogous reaction of anilinopyrimidine precursors using α-diazo esters led to the ortho-alkylation products. The carbenoid coupling reaction was successfully extended to 6-anilinopurine/purine nucleosides, and the ortho-alkylated 6-anilinopurines could be obtained in excellent yields. Proof of the involvement of an Rh–C-bonded species comes from the characterisation of an intermediate-like rhodacycle (which is also an active catalyst) by single-crystal X-ray crystallography.