title: Synthesis of cyclic sulfites from epoxides and sulfur dioxide with silica-immobilized homogeneous catalysts.
abstract: Quaternary ammonium- and amino-functionalized silica catalysts have been prepared for the selective synthesis of cyclic sulfites from epoxides and sulfur dioxide, demonstrating the effects of immobilizing the homogeneous catalysts on silica. The cycloaddition of sulfur dioxide to various epoxides was conducted under solvent-free conditions at 100 °C. The quaternary ammonium- and amino-functionalized silica catalysts produced cyclic sulfites in high yields (79-96 %) that are comparable to those produced by the homogeneous catalysts. The functionalized silica catalysts could be separated from the product solution by filtration, thereby avoiding the catalytic decomposition of the cyclic sulfite products upon distillation of the product solution. Heterogenization of a homogeneous catalyst by immobilization can, therefore, improve the efficiency of the purification of crude reaction products. Despite a decrease in catalytic activity after each recycling step, the heterogeneous pyridine-functionalized silica catalyst provided high yields after as many as five recycling processes.
authors.affiliation: National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba Central 5, Tsukuba, Ibaraki, Japan. yasumasa.takenaka@riken.jp
authors.forename: Yasumasa
authors.initials: Y
authors.lastname: Takenaka
authors.forename: Takahiro
authors.initials: T
authors.lastname: Kiyosu
authors.forename: Goro
authors.initials: G
authors.lastname: Mori
authors.forename: Jun-Chul
authors.initials: JC
authors.lastname: Choi
authors.forename: Norihisa
authors.initials: N
authors.lastname: Fukaya
authors.forename: Toshiyasu
authors.initials: T
authors.lastname: Sakakura
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Yasuda
mesh_terms: D000588:Amines / Q000737:chemistry; D002384:Catalysis; D060326:Chemistry Techniques, Synthetic / Q000379:methods*; D004852:Epoxy Compounds / Q000737:chemistry*; D000644:Quaternary Ammonium Compounds / Q000737:chemistry; D012822:Silicon Dioxide / Q000737:chemistry*; D013447:Sulfites / Q000138:chemical synthesis* / Q000737:chemistry*; D013458:Sulfur Dioxide / Q000737:chemistry*
chemical_list: D000588:Amines; D004852:Epoxy Compounds; D000644:Quaternary Ammonium Compounds; D013447:Sulfites; D013458:Sulfur Dioxide; D012822:Silicon Dioxide