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Lewis acid-Lewis base-catalysed enantioselective addition of alpha-ketonitriles to aldehydes
KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.ORCID iD: 0000-0002-1743-7650
2007 (English)In: Advanced Synthesis and Catalysis, ISSN 1615-4150, E-ISSN 1615-4169, Vol. 349, no 3, 364-372 p.Article in journal (Refereed) Published
Abstract [en]

Additions of structurally diverse alpha-ketonitriles to aromatic and aliphatic prochiral aldehydes yielding highly enantioenriched acylated cyanohydrins were achieved using a combination of a titanium salen dimer and an achiral or chiral Lewis base. In most cases high yields and high enantioselectivities were observed. The ee was moderate in the initial part of the reaction but increased over time. This could be avoided, and higher ees obtained, by keeping the titanium complex, in the presence or absence of aldehyde and ketonitrile, at -40 degrees C prior to the addition of the Lewis base. A mechanism initiated by nucleophilic attack of the tertiary amine at the carbonyl carbon atom of the ketonitile is supported by C-13 labelling experiments.

Place, publisher, year, edition, pages
2007. Vol. 349, no 3, 364-372 p.
Keyword [en]
Lewis acids; Lewis bases; O-acylcyanohydrins; Salen; Titanium
National Category
Organic Chemistry
Identifiers
URN: urn:nbn:se:kth:diva-6916DOI: 10.1002/adsc.200600365ISI: 000244268900015Scopus ID: 2-s2.0-33947594481OAI: oai:DiVA.org:kth-6916DiVA: diva2:11763
Note
QC 20100809Available from: 2007-03-22 Created: 2007-03-22 Last updated: 2017-12-14Bibliographically approved
In thesis
1. New Methods for Chiral Cyanohydrin Synthesis
Open this publication in new window or tab >>New Methods for Chiral Cyanohydrin Synthesis
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis deals with method development in asymmetric catalysis and specifically syntheses of enantioenriched O-functionalized cyanohydrins.

The first part describes the development of a method for the synthesis of O‑alkoxycarbonylated and O-acylated cyanohydrins. Ethyl cyanoformate and acyl cyanides were added to aldehydes in a reaction catalyzed by a chiral dimeric Ti-salen complex together with a tertiary amine. High yields and enantioselectivities were in most cases obtained. Mechanistic studies were performed and a reaction mechanism was proposed. ­

The second part describes a method in which the undesired minor enantiomer in a Lewis acid–Lewis base-catalyzed acylcyanation is continuously recycled into prochiral starting material. Close to enantiopure O‑acylated cyanohydrins were obtained in high yields.

The third part deals with asymmetric acylcyanations of ketones. Acetyl cyanide was found to add to α‑ketoesters in a reaction catalyzed by a chiral Lewis base. Yields up to 77% and 82% ee were obtained.

The final part describes an enzymatic method for high-throughput analysis of O‑acylated cyanohydrins. The enantiomeric excess and conversion were determined for products obtained from a number of aromatic and aliphatic aldehydes.

Place, publisher, year, edition, pages
Stockholm: KTH, 2009. 54 p.
Series
Trita-CHE-Report, ISSN 1654-1081 ; 2009:12
Keyword
acyl cyanides, asymmetric synthesis, biocatalysis, cyanide, cyanohydrins, dual activation, enzymes, high-throughput screening, Lewis acid, Lewis base, metal catalysis, minor enantiomer recycling, salen, titanium
National Category
Chemical Sciences
Identifiers
urn:nbn:se:kth:diva-10205 (URN)978-91-7415-263-0 (ISBN)
Public defence
2009-05-08, F3, Lindstedtsvägen 26, Stockholm, 10:00 (English)
Opponent
Supervisors
Note
QC 20100818Available from: 2009-05-07 Created: 2009-04-06 Last updated: 2010-09-22Bibliographically approved
2. Efficient Synthesis and Analysis of Chiral Cyanohydrins
Open this publication in new window or tab >>Efficient Synthesis and Analysis of Chiral Cyanohydrins
2007 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

This thesis deals with the development of new methods for efficient synthesis and analysis in asymmetric catalysis. It focuses on the preparation of chiral cyanohydrins by enantioselective addition of cyanide to prochiral aldehydes.

The initial part of the thesis describes the development of a dual Lewis acid– Lewis base activation system for efficient synthesis of chiral O-acylated and Ocarbonylated cyanohydrins. This system was used for the preparation of a variety of cyanohydrins in high isolated yields and with up to 96% ee. Activation of the cyanide by nucleophilic attack of the Lewis base at the carbonyl carbon atom was supported experimentally.

Secondly, convenient procedures for the synthesis of polymer-bound chiral YbCl3-pybox and Ti-salen complexes are described. The polymeric complexes were employed in cyanation of benzaldehyde.

A T-shaped microreactor was used for screening of reaction conditions for the enantioselective cyanation of benzaldehyde using trimethylsilyl cyanide and acetyl cyanide as cyanide sources. A microreactor charged with the polymeric Tisalen complex was used for enantioselective cyanation of benzaldehyde.

Finally, an enzymatic method for high throughput analysis of ee and conversion of products from chiral Lewis acid–Lewis base-catalysed additions of α- ketonitriles to prochiral aldehydes was developed. The method could be used for the analysis of a variety of O-acylated cyanohydrins. Microreactor technology was successfully combined with high throughput analysis for efficient catalyst optimisation.

Place, publisher, year, edition, pages
Stockholm: KTH, 2007. 54 p.
Series
Trita-CHE-Report, ISSN 1654-1081 ; 2007:11
Keyword
asymmetric catalysis, cyanohydrins, microreactor, polymersupported catalyst, ketonitriles, titanium, lanthanide, Lewis acid, Lewis base
National Category
Organic Chemistry
Identifiers
urn:nbn:se:kth:diva-4315 (URN)978-91-7178-599-2 (ISBN)
Public defence
2007-04-13, Sal F3, KTH, Lindstedtsvägen 26, Stockholm, 10:15 (English)
Opponent
Supervisors
Note
QC 20100809Available from: 2007-03-22 Created: 2007-03-22 Last updated: 2010-08-09Bibliographically approved

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