A mesoporous SBA-15 silica catalyst functionalized with phenylsulfonic acid groups (SBA-15-Ph-SO3H) as a novel hydrophobic nanoreactor solid acid catalyst for a one-pot three-component synthesis of 2H-indazolo[2,1-b]phthalazine-triones and triazolo[1,2-a]indazole-triones

Phenyl sulfonic acid functionalized mesoporous SBA-15 silica (SBA-15-Ph-SO3H) was prepared through the silanization of activated mesoporous SBA-15 with diphenyldichlorosilane (DPCS) followed by silylation and sulfonation, and characterized by XRD, FT-IR, nitrogen adsorption analyses, BET theory and TEM. The sulfonic acid groups anchored to the silica surface of the pore walls were resistant to leaching in organic and aqueous solutions under mild conditions. This catalyst was found to be a recyclable heterogeneous catalyst for the rapid and efficient synthesis of various 2H-indazolo[2,1-b]phthalazine-triones and triazolo[1,2-a]indazole-triones. Also, this silylated mesoporous material containing phenylsulfonic acid groups has a greater stability of the sulfonic acid surface toward water than that of silica sulfuric acid (SSA) and sulfonated SBA-15.