Universität zu Köln

Wolf, Florian F., Klare, Helge and Goldfuss, Bernd ORCID: 0000-0002-1814-8818 (2016). Asymmetric Michael Additions of 4-Hydroxycoumarin to beta-Nitrostyrenes with Chiral, Bifunctional Hydrogen-Bonding Catalysts. J. Org. Chem., 81 (5). S. 1762 - 1769. WASHINGTON: AMER CHEMICAL SOC. ISSN 1520-6904

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Abstract

Enantioselective Michael additions of 4-hydroxycoumarin to beta-nitrostyrenes are catalyzed by different chiral, bifunctional hydrogen-bonding catalysts, based on thiourea and squaramide motifs. The scope of the catalysis is tested by employing a series of substituted beta-nitrostyrenes as well as different solvents. The 3,5-bis(trifiuoromethyl)phenyl- and quinine-substituted squaramide catalyst is shown to be the most selective catalyst, resulting in 78% yield and 81% ee. Computational analyses of transition structures with different binding modes show that the most favored transition structure exhibits squaramide (NH)(2), binding to an oxygen atom of the enolate nucleophile, while the nitroalkene coordinates via hydrogen bonding to the ammonium function of the quinuclidine unit of the catalyst. Hence, the canted directionality of the squaramide (NH)(2) motif, favoring one-atom binding, might be decisive for the selectivity of the reaction. The absolute configuration of the major (-)-(R) enantiomer of the product is assigned computationally according to its optical rotation.

Item Type:	Journal Article
Creators:	Creators Email ORCID ORCID Put Code Wolf, Florian F. UNSPECIFIED UNSPECIFIED UNSPECIFIED Klare, Helge UNSPECIFIED UNSPECIFIED UNSPECIFIED Goldfuss, Bernd UNSPECIFIED orcid.org/0000-0002-1814-8818 UNSPECIFIED
URN:	urn:nbn:de:hbz:38-281694
DOI:	10.1021/acs.joc.5b02167
Journal or Publication Title:	J. Org. Chem.
Volume:	81
Number:	5
Page Range:	S. 1762 - 1769
Date:	2016
Publisher:	AMER CHEMICAL SOC
Place of Publication:	WASHINGTON
ISSN:	1520-6904
Language:	English
Faculty:	Faculty of Mathematics and Natural Sciences
Divisions:	Faculty of Mathematics and Natural Sciences > Department of Chemistry > Institute of Organic Chemistry
Subjects:	no entry
Uncontrolled Keywords:	Keywords Language MOLECULAR-ORBITAL METHODS; GAUSSIAN-BASIS SETS; ANION RECOGNITION; SQUARAMIDE; ORGANOCATALYSTS; THERMOCHEMISTRY; WARFARIN; BINDING; ATOMS Multiple languages Chemistry, Organic Multiple languages
Refereed:	Yes
URI:	http://kups.ub.uni-koeln.de/id/eprint/28169