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

Abstract

An efficient synthesis of fused cinnolines via Rh(III)-catalysed [4 + 2] annulation of N-aryl pyrazolones with iodonium ylides in up to 81% yields has been developed with 27 examples. This protocol features operational simplicity, ready availability of starting materials, broad substrate scope, and gram-scale scalability. Notably, the titled targets exhibit strong fluorescence, which enables their potential application as fluorescent probes.