Synthesis of new chiral Mn(III)-salen complexes as recoverable and reusable homogeneous catalysts for the asymmetric epoxidation of styrenes and chromenes

New chiral Mn(III)-salen complexes 1a-e and 2a-e were synthesized from the reaction of C-2-symmetric chiral sa[en Eigands and Mn(CH3COO)(2)center dot 4H(2)O under an inert atmosphere followed by aerobic oxidation. These complexes were obtained in 91-96% yields and characterized by HRMS, FT-IR, UV-visible spectroscopy, TGA, and elemental analysis. The chiral Mn(III)-salen complexes 1a-e and 2a-e were evaluated in the asymmetric epoxidation of styrene using NaOCl as an oxidant in ethyl acetate as a green solvent. The chiral Mn(III)-salen complexes 1b and 2b (2 mo[%) catalyzed the asymmetric epoxidation of substituted styrenes and chromenes to afford the corresponding epoxides in 95-98% yields with 29-88% ee's. The catalysts 1b and 2b were recovered and reused for up to 2 and 3 runs, respectively, in the asymmetric epoxidation of styrene, and the yield of styrene oxide gradually decreased but the ee was consistent.