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Methyl Iodide Accelerated Asymmetric Epoxidation of Alkenes Catalyzed by Chiral Salen‐Mn(III) Complexes with Tertiary Amine Units
Author(s) -
Sun Yang,
Tang Ning
Publication year - 2007
Publication title -
chinese journal of chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.28
H-Index - 41
eISSN - 1614-7065
pISSN - 1001-604X
DOI - 10.1002/cjoc.200790126
Subject(s) - chemistry , catalysis , pyridine n oxide , pyridine , iodide , ammonium iodide , ammonium , amine gas treating , enantioselective synthesis , medicinal chemistry , methyl iodide , tertiary amine , amine oxide , polymer chemistry , organic chemistry , alkyl
A series of chiral salen‐Mn(III) complexes featuring two tertiary amine units were synthesized and employed in the enantioselective epoxidation of unfunctionalized alkenes in the presence of pyridine N ‐oxide and 2,6‐dimeth‐ ylpyridine N ‐oxide as proximal ligands, respectively. Moderate to high enantioselectivity and acceptable yields were achieved when NaClO was used as terminal oxidant under CH 2 Cl 2 /H 2 O biphasic media. Methyl iodide was found to be an effective additive to accelerate the epoxidation, possibly owing to the formation of quaternary ammonium units on catalysts, which may facilitate the reaction in an oil/water biphasic medium. The subsequent stimulation experiment was carried out, and the resulting ESI‐HRMS analysis revealed the formation of a novel (salen)manganese(III) intermediate featuring two quaternary ammonium units, and bearing a pyridine N ‐oxide and a molecule of water simultaneously axially‐coordinated backbone.