Asymmetric epoxidation of styrene and chromenes catalysed by dimeric chiral (pyrrolidine salen)Mn(III) complexes
2006 (English)In: Applied Catalysis A: General, ISSN 0926-860X, E-ISSN 1873-3875, Vol. 315, 120-127 p.Article in journal (Refereed) Published
Two dimeric chiral (pyrrolidine salen)Mn(III) complexes 3 and 4 were prepared, in which the two (pyrrolidine salen)Mn(III) units are linked either by a p-xylylene or by ap-phthalyl bridge. High yields were attained for asymmetric epoxidation of styrene and substituted chromenes at 0.5-4.0 mol% catalyst loading of 3 and 4 using NaClO/PPNO and m-CPBA/NMO as oxidant systems, with 37-39% ee for styrene and 86-95% ee for substituted chromenes. Dimeric complexes 3 and 4 displayed higher activities than their parent monomeric complexes 1 and 2 of double equiv for epoxidation of substituted chromenes. Complex 3 bearing two tertiary amine units displayed considerably higher activity than analogous dimeric complex 4 containing two carboxamide units in the aforementioned reaction. The effect of excess CH3I on the epoxidation of 6-nitro-2,2-dimethylchromene catalysed by 3 in the aqueous/organic biphasic medium was explored. The recovery and recycling possibilities of the dimeric complexes 3 and 4 were studied.
Place, publisher, year, edition, pages
2006. Vol. 315, 120-127 p.
asymmetric epoxidation, chromene, dimeric manganese complex, salen ligand, styrene, highly enantioselective epoxidation, phase-transfer capability, nonfunctionalized alkenes, unfunctionalised olefins, salen complexes, epoxides, oxidant, silica
IdentifiersURN: urn:nbn:se:kth:diva-16203DOI: 10.1016/j.apcata.2006.09.011ISI: 000242775600014ScopusID: 2-s2.0-33750741096OAI: oai:DiVA.org:kth-16203DiVA: diva2:334245
QC 201005252010-08-052010-08-05Bibliographically approved