Use of ionic liquids as solvents for epoxidation reactions catalysed by a chiral Katsuki-type salen complex: enhanced reactivity and recovery of catalyst

The Katsuki-type catalyst 2 has been recycled several times following its use in a model epoxidation reaction of 1,2-dihydronaphthalene in an ionic liquid, 3a or 3b. The enantioselectivity was comparable to that in dichloromethane, but recovery of the catalyst was easier, activity was higher, and activity and enantioselectivity were retained in recovered ionic liquid fractions to a much greater extent than those for the Jacobsen-type catalyst 1