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 Rh-III-catalysed reaction of 2-anilinopyridines with sulfonylated alpha-diazo esters under mild conditions gave oxindole derivatives, while an analogous reaction of anilinopyrimidine precursors using alpha-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.