Influence of the built-in pyridinium salt on asymmetric epoxidation of substituted chromenes catalysed by chiral (pyrrolidine salen)Mn(III) complexes
2007 (English)In: Journal of Molecular Catalysis A: Chemical, ISSN 1381-1169, Vol. 270, no 02-jan, 278-283 p.Article in journal (Refereed) Published
Chiral (pyrrolidine salen)Mn(III) complexes 1 with an N-benzoyl group and 2 with an N-isonicotinoyl group as well as the corresponding N-methyl (3) and N-benzyl (4) pyridinium salts of 2 were synthesized. The catalytic properties of 1-4 and 2 with excess CH3I were explored to figure out the influence of the internal pyridinium salt in the catalyst on asymmetric epoxidation of substituted chromenes with NaClO/PPNO as an oxidant system in the aqueous/organic biphasic medium. The (pyrrolidine salen)Mn(III) complexes with an internal pyridinium salt, either formed in situ or isolated, displayed higher activities than analogous complexes 1, 2 and Jacobsen's catalyst in the aforementioned reaction, with comparable high yields and ee values. The acceleration of the reaction rate is attributed to the phase transfer capability of the built-in pyridinium salt of the (salen)Mn(III) catalyst. The effect of the internal pyridinium salt on the epoxidation of substituted chromenes is similar to that of the external pyridinium salts and ammonium halides.
Place, publisher, year, edition, pages
2007. Vol. 270, no 02-jan, 278-283 p.
asymmetric epoxidation, chiral pyrrolidine, chromene, pyridinium salt, (salen)Mn(III) complex, phase-transfer capability, enantioselective epoxidation, nonfunctionalized alkenes, mn(iii) salen, styrene, olefins
IdentifiersURN: urn:nbn:se:kth:diva-16647DOI: 10.1016/j.molcata.2007.01.052ISI: 000246640100037ScopusID: 2-s2.0-34247200061OAI: oai:DiVA.org:kth-16647DiVA: diva2:334689
QC 201005252010-08-052010-08-05Bibliographically approved