Asymmetric cyclopropanation catalyzed by C-2-symmetric bi(oxazolines)

C-2-symmetric bi(oxazolines) 3a-e were prepared in three steps based on a tartaric-derived vicinal diamine as common precursor. These chiral ligands were studied with respect to their directive influence on the enantioselective copper catalyzed cyclopropanation of 1,1 -diphenylethylene and styrene....

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Bibliographic Details
Published inTetrahedron letters Vol. 41; no. 7; pp. 1023 - 1026
Main Authors Boulch, R, Scheurer, A, Mosset, P, Saalfrank, RW
Format Journal Article
LanguageEnglish
Published OXFORD Elsevier 12.02.2000
Subjects
Chemistry
Chemistry, Organic
Physical Sciences
Science & Technology
KETONES
CHIRAL LIGANDS
ETHERS
asymmetric reactions
copper compounds
cyclopropanation
HYDROSILYLATION
copper
OLEFINS
alkenes
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Summary:C-2-symmetric bi(oxazolines) 3a-e were prepared in three steps based on a tartaric-derived vicinal diamine as common precursor. These chiral ligands were studied with respect to their directive influence on the enantioselective copper catalyzed cyclopropanation of 1,1 -diphenylethylene and styrene. The highest enantioselectivities (79% ee) were achieved with bi(oxazoline) 3e, bearing bulky adamantyl groups even using commercial CuOTf. The presence of desiccants such as molecular sieves or magnesium sulfate was found to be crucial for high yields and reproducibility. (C) 2000 Elsevier Science Ltd. All rights reserved.
ISSN:0040-4039
DOI:10.1016/S0040-4039(99)02220-0