Surface modification of silica-coated on the magnetic nanoparticles with covalently immobilized between imidazolium cation and silane groups for potential application as a green catalyst

Mechanochemical synthesis of coumarins via Pechmann condensation under solvent-free conditions: an easy access to coumarins and annulated pyrano[2,3-f] and [3,2-f]indoles

“…In addition, several modifications of the classical Pechmann procedure allowing moderate reaction conditions have been reported. 2 Several milder catalysts such as methanesulfonic acid (MsOH), 3 MsOH on Al 2 O 3 , 4 p-TsOH, 5 Ti(IV)-doped ZnO matrix, 6 3-methyl-1-sulfonic acid imidazo-lium hydrogen sulfate, 7 FeF 3 , 8 Fe 3 O 4 @SiO 2 -imidazolium nanoparticles, 9 poly(4-vinylpyridine)-CuI 10 and glutamic acid 11 have been employed. However, all these procedures have one or more practical disadvantages, such as the requirement of higher amounts of MsOH 4 or p-TsOH (0.5 to 1.5 equivalents) which reduced the merit of the process and increased the amount of waste.…”