Synthesis of new macrocyclic chiral manganese(III) Schiff bases as catalysts for asymmetric epoxidation.
We describe a general synthetic strategy for the preparation of a series of macrocyclic chiral manganese(III) salen complexes. The developed reaction pathway allows the modulation of the different key groups, namely, the chiral diimine, the bulky substituents in positions 3 and 3', and the linker used in the macrocyclization of the Schiff base. The different complexes presented here illustrate these readily available structural variations. The catalytic properties of the catalysts (5 mol %) were improved for the asymmetric epoxidation of 2,2'-dimethylchromene with NaOCl or H2O2 as oxygen atom donor. A large range of enantiomeric excesses was obtained (ee values from 30% to 96%), depending on the features and the stability of the complexes. The most efficient catalyst, in terms of stereoinduction (ee value = 96%), contains a diiminocyclohexyl moiety, ethyl groups in positions 3 and 3', and a short polyether junction arm.
Laboratoire de Chimie de Coordination du CNRS, 205 route de Narbonne, 31077 Toulouse cedex 4, France.
Alexandre
A
Martinez
Catherine
C
Hemmert
Christophe
C
Loup
Guillaume
G
Barré
Bernard
B
Meunier
D002384:Catalysis; D003432:Cross-Linking Reagents / Q000737:chemistry; D003500:Cyclization; D004852:Epoxy Compounds / Q000138:chemical synthesis*; D005029:Ethylenediamines; D007097:Imines / Q000737:chemistry; D047028:Macrocyclic Compounds / Q000138:chemical synthesis; D008345:Manganese / Q000737:chemistry; D012545:Schiff Bases / Q000138:chemical synthesis*; D013237:Stereoisomerism; D013329:Structure-Activity Relationship
D003432:Cross-Linking Reagents; D004852:Epoxy Compounds; D005029:Ethylenediamines; D007097:Imines; D047028:Macrocyclic Compounds; D012545:Schiff Bases; D008345:Manganese; C011452:disalicylaldehyde ethylenediamine