Convenient synthesis of heterocyclic azo dyes in the class of pyranopyrazoles and chromenes.

A series of novel azo group fused 2H-chromenes and 4H-chromenes were synthesised as well as pyranopyrazole derivatives via the Knoevenagel condensation reaction of C–H acid compounds with 5-(arylazo)salicylaldehydes by a nucleophilic addition to the carbonyl group followed cyclisation. [ABSTRACT FROM AUTHOR]