期刊
TETRAHEDRON LETTERS
卷 52, 期 29, 页码 3718-3722出版社
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.tetlet.2011.05.017
关键词
Hydrazones; Chiral hydrazenes; Asymmetric hydrogenation; Reversed enantioselectivity
An enantioselective hydrogenation of hydrazones derived from heterocyclic ketones was developed with up to 85% ee. The enantiomeric purity was enriched to >99% ee by crystallization from EtOAc in >80% yield. Optimization studies have revealed a notable solvent effect that resulted in inversion of enantioselectivity from 85% ee in MeOH to -27% ee in DCE. The hydrazone geometry and possible hydrogenation via endocyclic alkene were examined as possible factors for the inversion of enantioselectivity. (C) 2011 Elsevier Ltd. All rights reserved.
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