[62668-00-2] · C16H23NO2 · N-Phenylcampholylhydroxamic Acid · (MW 261.40)
(chiral ligand in asymmetric epoxidation of allylic alcohols1)
Solubility: sol toluene, acetonitrile.
Preparative Method: phenylhydroxylamine (2 equiv) is added to a solution of campholyl chloride (1 equiv) in acetonitrile.1
N-Phenylcampholylhydroxamic acid has been used as a chiral ligand in the transition metal-catalyzed asymmetric epoxidation of allylic alcohols.1 Three allylic alcohols [geraniol (1), (E)-a-phenylcinnamyl alcohol (2), and 1-hydroxymethyl-2-methylcyclohexene (3)] have been oxidized to the corresponding epoxides in the presence of the chiral hydroxamate complex of vanadium. The best asymmetric induction (50% ee) is observed for alcohol (2) at -78 °C. Generally, low temperature reactions give higher asymmetric inductions but lower yields. The optimum inductions are attained when a 5:1 ratio of hydroxamic acid and Vanadyl Bis(acetylacetonate) is used. t-Butyl Hydroperoxide gives substantially better inductions than Cumyl Hydroperoxide. The asymmetric oxidation is proposed to go through the intermediate
Myong Ji University, Seoul, Korea