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Asymmetric epoxidation of styrene and chromenes catalysed by dimeric chiral (pyrrolidine salen)Mn(III) complexes

Paper ID Volume ID Publish Year Pages File Format Full-Text
43850 45991 2006 8 PDF Available
Title
Asymmetric epoxidation of styrene and chromenes catalysed by dimeric chiral (pyrrolidine salen)Mn(III) complexes
Abstract

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 a p-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.

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Keywords
Asymmetric epoxidation; Chromene; Dimeric manganese complex; Salen ligand; Styrene
First Page Preview
Asymmetric epoxidation of styrene and chromenes catalysed by dimeric chiral (pyrrolidine salen)Mn(III) complexes
Publisher
Database: Elsevier - ScienceDirect
Journal: Applied Catalysis A: General - Volume 315, 23 November 2006, Pages 120–127
Authors
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Subjects
Physical Sciences and Engineering Chemical Engineering Catalysis