期刊
TETRAHEDRON
卷 62, 期 15, 页码 3573-3581出版社
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.tet.2006.01.093
关键词
enantioselective allylic oxidation; olefins; phenylhydrazine; phenylhydrazone
Copper complexes of chiral tridentate pybox ligands synthesized using a modified procedure have been studied as catalysts for the enantioselective allylic oxidation of olefins. A variety of olefins have been used in this reaction. Using 5 mol% of a Cu(II) complex of the tridentate pybox ligand, phenylhydrazine, and tert-butyl perbenzoate as oxidant in acetone, optically active allylic benzoates were obtained up to 94% ee in few hours. It was also observed that the use of molecular sieves in the reaction did not alter the enantioselectivity. Temperature was found to be very crucial in rate of the enantioselective allylic oxidation of olefins. Using EPR spectra, it has been shown that the Cu(II) species is reduced to Cu(I) by phenyhydrazine and phenylhydrazone. but the reduction with the former is faster in comparison to the latter. It was concluded that the rate enhancement was not specific to the presence of phenylhydrazine or phenylhydrazone, but both were equally responsible provided acetone was used as a solvent. (c) 2006 Elsevier Ltd. All rights reserved.
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