Abstract
Practical synthesis of chiral C
2 -symmetric
substituted bisoxazoline ligands containing 2,5-diaryl-1,3,4-oxadiazole
units was investigated. Five chiral bisoxazoline ligands containing
2,5-diphenyl-1,3,4-oxadiazole have been synthesized from 2,5-di-(o -carboxylphenyl)-1,3,4-oxadiazole and
amino alcohols by methanesulfonyl chloride or p -toluenesulfonyl
chloride assisted cyclization via hydroxy amide intermediate. Preliminary
examination of copper complexes of new ligands as chiral catalysts
in the enantioselective cyclopropanation of styrene with ethyl diazoacetate
was performed. Enantioselectivities up to 35% ee and 87% ee
for trans - and cis -2-phenylcyclopropanecarboxylate,
respectively were observed.
Key words
bisoxazoline - oxadiazole - enantioselective
cyclopropanation
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