The influence of axial ligands on the catalytic activity and enantioselectivity of salen‐Mn complexes in the asymmetric epoxidation

2019 ◽  
Vol 32 (9) ◽  
Author(s):  
Liu Yang ◽  
Xingbang Hu ◽  
Youting Wu
Keyword(s):  
Catalytic Activity ◽  
Asymmetric Epoxidation ◽  
Axial Ligands

ChemInform Abstract: Ru-Salen Catalyzed Asymmetric Epoxidation: Photoactivation of Catalytic Activity.

ChemInform ◽  
2010 ◽  
Vol 30 (42) ◽  
pp. no-no
Author(s):  
Tsuyoshi Takeda ◽  
Ryo Irie ◽  
Yo Shinoda ◽  
Tsutomu Katsuki
Keyword(s):  
Catalytic Activity ◽  
Asymmetric Epoxidation

Investigation of axial ligand effects on catalytic activity of manganese porphyrin, evidence for the importance of hydrogen bonding in cytochrome-P450 model reactions

2014 ◽  
Vol 18 (05) ◽  
pp. 354-365 ◽  
Author(s):  
Elnaz Mesbahi ◽  
Nasser Safari ◽  
Mahin Gheidi
Keyword(s):  
Hydrogen Bonding ◽  
Catalytic Activity ◽  
Product Formation ◽  
Axial Ligand ◽  
Active Species ◽  
Manganese Porphyrin ◽  
Axial Ligands ◽  
Epoxidation Reaction ◽  
Phenyl Rings ◽  
Hydroxy Groups

Various nitrogenous bases, such as imidazoles, pyridines and amines were employed as axial ligands in epoxidation reaction of cyclooctene bytetra-n-butylammonium hydrogen monopersulfate (n- Bu 4 NHSO 5), in the presence of Mn ( III )-tetrakis(2,3-dimethoxyphenyl)porphyrin-acetate ( T (2,3- OMeP ) PorMnOAc ). T (2,3- OMeP ) PorMnOAc is a fairly stable catalyst, with the ability of producing hydrogen bonding. High epoxidation yield of 85 ± 6% was obtained in the presence of imidazole axial ligand with 100% selectivity in 30 min. Higher conversion of around 100% was obtained by pyridine axial base, while selectivity was reduced to 69%. Further epoxidation reactions were also performed using Mn ( III )-Tetrakis(2,3-dihydroxyphenyl)porphyrin-acetate ( T (2,3- OHP ) PorMnOAc ) as catalyst. In addition to the usual electronic and steric effects, it is proposed that the catalytic activity depends on the existence and kind of hydrogen bonding between the axial base and the ortho-methoxy or hydroxy groups on the phenyl rings of manganese porphyrin. The cis to trans ratio of cis-stilbene oxide formed by imidazole and pyridine axial bases were obtained as 7.5 and 2.5 respectively. In addition GC-Ms and UV-vis studies were employed to find the nature of active species and product formation. Our DFT calculations disclosed that pyridine hydrogen bonding with moiety of the macrocycle rings strongly affects the relative energies of S/Q spin states in [ T (2,3- OMeP ) PorMn V ( O )( Py )]+, in that it results in the longer Mn – O bond and reactivity toward substrates.

Ru-Salen Catalyzed Asymmetric Epoxidation: Photoactivation of Catalytic Activity

Synlett ◽  
1999 ◽  
Vol 1999 (7) ◽  
pp. 1157-1159 ◽  
Author(s):  
Tsuyoshi Takeda ◽  
Ryo Irie ◽  
Yo Shinoda ◽  
Tsutomu Katsuki
Keyword(s):  
Catalytic Activity ◽  
Asymmetric Epoxidation
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