Silica-bonded propylpiperazine-N-sulfamic acid as recyclable solid acid catalyst for preparation of 2-amino-3-cyano-4-aryl-5,10-dioxo- 5,10-dihydro-4H-benzo[g]chromenes and hydroxy-substituted naphthalene-1,4-dione derivatives

Silica-bonded propylpiperazine-N-sulfamic acid as recyclable solid acid catalyst for preparation of 2-amino-3-cyano-4-aryl-5,10-dioxo-5,10-dihydro-4H-benzo[g]chromenes and hydroxy-substituted naphthalene-1,4-dione derivatives