4-Phenylpyridine-N-oxide

Jacobsen catalyst 4-Phenylpyridine N-oxide Methylen chloride Hexane... 

A 100 mL flask, was filled with (Z)-ethyl cinnamate, (666 mg of the mixture containing 75 % of (Z)-ethyl cinnamate), 4-phenylpyridine N-oxide (116 mg) and dichloromethane (6mL). Jacobsen s catalyst (108 mg) was then added. 

Resolution of a racemic mixture is still a valuable method involving fractional crystallization [113], chiral stationary phase column chromatography [114] and kinetic resolutions. Katsuki and co-workers demonstrated the kinetic resolution of racemic allenes by way of enantiomer-differentiating catalytic oxidation (Scheme 4.73) [115]. Treatment of racemic allenes 283 with 1 equiv. of PhIO and 2 mol% of a chiral (sale-n)manganese(III) complex 284 in the presence of 4-phenylpyridine N-oxide resulted... 

Over the years further tuning of the ligand by varying the substituents in the aromatic ring has led to >90% ee for a number of olefins [278]. Improvements were also achieved by adding amine-N-oxides such as 4-phenylpyridine-N-oxide... 

Phenylpyridine N-oxide was purchased from Aldrich Chemical Company, Inc., and used as received. Other pyridine N-oxide derivatives have been used with success in the epoxidation reaction. The choice of the pyridine N-oxide derivative has been demonstrated to have a small yet measurable impact on both the rate of reaction and the enantiomeric excess of the product epoxide. ... 

The chiral Mn-salen catalysts have successfully been used in pharmaceutical industry processes. For example, enantioselective epoxidation of indene 43 under Jacobsen et al. s conditions provided epoxide 44 in 71% yield and 84—86% ee. It was reported that both yield and enantiose-lectivity were increased by adding 4-phenylpyridine N-oxide (PPNO) as co-oxidant in the system. A modified Ritter reaction converted indene oxide 44 into the c -amino alcohol 46. The enantiomeric purity of 46 was enhanced to >99% ee by formation of the corresponding L-tartrate salt followed by recrystallization. Amino alcohol 46 was identified as a critical component of the highly effective HIV protease inhibitor Indinavir 47 developed by Merck (White-house Station, NJ) (Scheme 35.12). ... 

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