The efficiency of HZSM-5 Zeolite, tungestophosphoric acid (H3PW12O40) and tungestosililic acid (H4O40SiW12) were investigated in three-component, one-pot synthesis of coumarin dyes. These green and noncorrosive acids were highly efficient in synthesis of some coumarin dyes in excellent yield during concurrent formation of coumarin and benzimidazole or benzoxazole heterocycles (e.g. C. I. disper...
