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J Am Chem Soc. 2006 Nov 15;128(45):14440-1.

Dramatic ligand effect in catalytic asymmetric reductive aldol reaction of allenic esters to ketones.

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1
Graduate School of Pharmaceutical Sciences, The University of Tokyo, Tokyo 113-0033, Japan.

Abstract

A general catalytic asymmetric reductive aldol reaction of allenic esters to ketones is described. Two distinct constitutional isomers were selectively produced depending on the reaction conditions. A combination of CuOAc/(R)-DTBM-SEGPHOS/PCy3 as the catalyst predominantly produced gamma-cis-products in high yield with excellent enantioselectivity (up to 99% ee). The reaction was applicable to both aromatic and aliphatic ketones, including unsaturated ketones. On the other hand, CuF-Taniaphos complexes produced alpha-aldol products with high diastereo- and enantioselectivity (up to 84% ee). The new Taniaphos derivative L3, containing di(3,5-xylyl)phosphine and morpholine units, produced optimum results in the alpha-selective reaction. The products are versatile chiral building blocks in organic synthesis. Furthermore, the basic reaction pattern (i.e., conjugate addition-aldol reaction) was extended to a catalytic enantioselective alkylative aldol reaction to ketones using dialkylzinc reagents as the initiator.

PMID:
17090010
DOI:
10.1021/ja0652565
[Indexed for MEDLINE]
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