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

Synthesis of tricyanomethanesulfonic acid as a novel nanostructured and recyclable solid acid: application at the synthesis of biological henna-based chromenes

A novel and unique nanostructured solid acid, namely tricyanomethanesulfonic acid (TCMS), was designed, synthesized, and attained as an ecofriendly, reusable catalyst for the one-pot three-component synthesis of 2-amino-3-cyano-4-aryl-5,10-dioxo-5,10-dihydro-4H-benzo[g]chromene derivatives from the reaction between aromatic aldehydes, 2-hydroxynaphthalene-1,4-dione (henna), and malononitrile under solvent-free conditions at room temperature with good to excellent yields and a short reaction time. The TCMS catalyst was prepared and fully characterized by FTIR, 1H NMR, 13C NMR, mass, X-ray diffraction patterns (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), thermal gravimetric (TG), and derivative thermal gravimetric (DTG) analyses. The nanostructured solid acid catalyst was simply recycled at least eight times without any loss of catalytic activity. This process is improved as a safe and appropriate procedure for the synthesis of 2-amino-3-cyano-4-aryl-5,10-dioxo-5,10-dihydro-4H-benzo[g]chromenes using an environmentally friendly and green recyclable catalyst. Thus, TCMS is a good candidate for the synthesis of new molecular organic frameworks and gelators.