Rhodium( iii )-catalyzed C–H activation/annulation of N -iminopyridinium ylides with alkynes and diazo compounds

A highly efficient process for Rh( iii )-catalyzed C–H activation/annulation of N -iminopyridinium ylides with alkynes and diazo compounds has been realized, providing a variety of isoquinolones and isocoumarins in moderate to excellent yields. This reaction proceeds smoothly under mild conditions and features operational simplicity, broad substrate scope and good functional group tolerance. Notably, the N -iminopyridinium ylide acts as an internal oxidant in the annulation with alkynes to afford isoquinolones through N–N bond cleavage, whereas as a leaving group in the reaction with diazo compounds through an alkylation–nucleophilic cyclization sequence for the synthesis of isocoumarins.