Rh( iii )-catalysed [4 + 2] annulation of N -arylpyrazolones with iodonium ylides: access to fused cinnolines

An efficient synthesis of fused cinnolines via Rh( iii )-catalysed [4 + 2] annulation of N -aryl pyrazolones with iodonium ylides was developed. The titled compounds exhibit strong fluorescence, enabling their potential application as probes.