Co-reporter:Celin Richter, Michael Krumrey, Marwa Bahri, Sebastian Trunschke, and Rainer Mahrwald
ACS Catalysis 2016 Volume 6(Issue 8) pp:5549
Publication Date(Web):July 12, 2016
DOI:10.1021/acscatal.6b01699
An amine-catalyzed cascade reaction of unprotected carbohydrates with 1.3-diketones was elaborated. This cascade is based on a Knoevenagel reaction/intramolecular ketalization/retro-aldol reaction. By application of this operationally simple protocol, a direct access to optically active stereopentads or stereotetrads is given. Rules of configurative outcomes will be discussed.Keywords: amine-catalysis; carbohydrates; cascade reactions; chiral stereopentads; stereoselectivity
Co-reporter:Celin Richter, Falko Berndt, Tom Kunde, and Rainer Mahrwald
Organic Letters 2016 Volume 18(Issue 12) pp:2950-2953
Publication Date(Web):June 7, 2016
DOI:10.1021/acs.orglett.6b01287
An operationally simple protocol is reported to generate an α-hydroxyacyl anion by the decarboxylation of dihydroxyfumaric acid. To date, the “missing” utilization of the hydroxyacyl anion in highly chemo- and stereoselective cascade reactions enables short and direct construction of carbohydrates.
Co-reporter:Alexander Arndt;Tom Kunde
ChemTexts 2016 Volume 2( Issue 1) pp:
Publication Date(Web):2016 March
DOI:10.1007/s40828-015-0020-2
A system of logic disconnection or construction of organic molecules is given to overcome serious problems in the study of organic chemistry. Based on the logic system of polar reactions of donors and acceptors several different reactions can be created to access a required target molecule. By a following careful analysis of these proposals several transformations can be detected as the preferred ones. Moreover, by the introduction of the “umpolung” principle additional options are given to synthesize a required molecule. These considerations were discussed in the 1,2-, 1,3-, 1,4-, 1,5- and 1,6-difunctional series.
Co-reporter:A. Michael Downey, Celin Richter, Radek Pohl, Rainer Mahrwald, and Michal Hocek
Organic Letters 2015 Volume 17(Issue 18) pp:4604-4607
Publication Date(Web):September 10, 2015
DOI:10.1021/acs.orglett.5b02332
New, improved methods to access nucleosides are of general interest not only to organic chemists but to the greater scientific community as a whole due their key implications in life and disease. Current synthetic methods involve multistep procedures employing protected sugars in the glycosylation of nucleobases. Using modified Mitsunobu conditions, we report on the first direct glycosylation of purine and pyrimidine nucleobases with unprotected d-ribose to provide β-pyranosyl nucleosides and a one-pot strategy to yield β-furanosides from the heterocycle and 5-O-monoprotected d-ribose.
Co-reporter:Benjamin Voigt, Michael Linke, and Rainer Mahrwald
Organic Letters 2015 Volume 17(Issue 11) pp:2606-2609
Publication Date(Web):May 8, 2015
DOI:10.1021/acs.orglett.5b00887
Herein an operationally simple multicomponent reaction of unprotected carbohydrates with amino acids and isonitriles is presented. By the extension of this Ugi-type reaction to an unprotected disaccharide a novel glycopeptide structure was accessible.
Co-reporter:Celin Richter, Benjamin Voigt and Rainer Mahrwald
RSC Advances 2015 vol. 5(Issue 56) pp:45571-45574
Publication Date(Web):14 May 2015
DOI:10.1039/C5RA08757K
An amine-catalyzed cascade reaction of ketoses with 1,3-dicarbonyl compounds is described. Several highly chemo- as well as stereoselective reactions are operating in this novel cascade. The operationally simple protocol allows stereoselective access to optically active carbon chain elongated ketoses.
Co-reporter:Celin Richter, Minh Nguyen Trung, and Rainer Mahrwald
The Journal of Organic Chemistry 2015 Volume 80(Issue 21) pp:10849-10865
Publication Date(Web):October 9, 2015
DOI:10.1021/acs.joc.5b02003
A highly stereoselective multicomponent cascade reaction of ketones with unprotected amino acids was developed. This operationally simple methodology was expanded to reactions of unprotected ketohexoses and unprotected amino acids. By the careful choice of amino acid and isonitrile, an optional access to all possible enantiomers is given.
Co-reporter:Anastassia Matviitsuk, Falko Berndt, and Rainer Mahrwald
Organic Letters 2014 Volume 16(Issue 20) pp:5474-5477
Publication Date(Web):October 6, 2014
DOI:10.1021/ol5027443
This paper proposes a new and stereoselective access to glycosides. This operationally simple approach achieved via base-catalyzed conjugate additions of unprotected and unactivated carbohydrates to activated alkenes or alkynes is described.
Co-reporter:Benjamin Voigt and Rainer Mahrwald
Chemical Communications 2014 vol. 50(Issue 7) pp:817-819
Publication Date(Web):13 Nov 2013
DOI:10.1039/C3CC48120D
An organocatalyzed transformation to elongate unprotected carbohydrates is described. This operationally simple methodology is based on a Knoevenagel–oxa-Michael cascade. This reaction is catalyzed by proline and DBU. Products were obtained with exceptional high degrees of stereoselectivity.
Co-reporter:Sebastian Schmalisch and Rainer Mahrwald
Organic Letters 2013 Volume 15(Issue 22) pp:5854-5857
Publication Date(Web):November 1, 2013
DOI:10.1021/ol402914v
Organocatalyzed direct glycosylation of unprotected and unactivated carbohydrates is reported. This process is catalyzed by triphenylphosphine and tetrabromomethane at room temperature under neutral conditions. With this operationally simple protocol thermodynamically favored, glycosides were obtained in a very straightforward reaction.
Co-reporter:Maximillian Böhm;Kerstin Proksch
European Journal of Organic Chemistry 2013 Volume 2013( Issue 6) pp:1046-1049
Publication Date(Web):
DOI:10.1002/ejoc.201201644
Abstract
p-Methoxyphenylimines obtained from enolizable aldehydes react in the absence of catalysts at room temperature with β-keto carboxylic acids through a decarboxylative Mannich reaction. The Mannich products were obtained with a high degree of anti selectivity. By use of chiral oxygen-containing aldehydes, operationally simple access to aminohydroxylated polyketide substructures is possible.
Co-reporter:Benjamin Voigt, Anastassia Matviitsuk, Rainer Mahrwald
Tetrahedron 2013 69(21) pp: 4302-4310
Publication Date(Web):
DOI:10.1016/j.tet.2013.03.063
Co-reporter:Dr. Ulf Scheffler ;Dr. Rainer Mahrwald
Chemistry - A European Journal 2013 Volume 19( Issue 43) pp:14346-14396
Publication Date(Web):
DOI:10.1002/chem.201301996
Abstract
Beyond a doubt organocatalysis belongs to the most exciting and innovative chapters of organic chemistry today. Organocatalysis has emerged not only as a complement to metal-catalyzed reactions and to biocatalysis over the last decade, but also provides new asymmetric organocatalyzed reactions that cannot be accomplished by metal- or biocatalyzed reactions so far. A large number of organocatalytic processes are already well established in organic synthesis. Nevertheless, the number of publications in this field is still on the increase; new important results are produced constantly. This review gives a detailed overview of the latest developments and main streams in organocatalyzed asymmetric CC bond formation processes of the last three years. It is intended to outline the most important current findings focused on especially new synthetic methodologies.
Co-reporter:Benjamin Voigt, Ulf Scheffler and Rainer Mahrwald
Chemical Communications 2012 vol. 48(Issue 43) pp:5304-5306
Publication Date(Web):27 Mar 2012
DOI:10.1039/C2CC31541F
Aldol additions of unprotected carbohydrates to 1.3-dicarbonyl compounds have been described. This transformation is based on a dual activation by tertiary amines and 2-hydroxypyridine.
Co-reporter:Kerstin Rohr and Rainer Mahrwald
Organic Letters 2012 Volume 14(Issue 8) pp:2180-2183
Publication Date(Web):April 10, 2012
DOI:10.1021/ol300754n
Isoleucine-catalyzed direct enantioselective aldol additions between enolizable aldehydes are reported. Intermediate acetal structures dictate the configurative outcome and were supported by a hydrogen bond. This direct isoleucine-catalyzed aldol addition represents a welcome complement to both proline- and histidine-catalyzed aldol additions of enolizable aldehydes.
Co-reporter:Ulf Scheffler;Reinhard Stößer
Advanced Synthesis & Catalysis 2012 Volume 354( Issue 14-15) pp:2648-2652
Publication Date(Web):
DOI:10.1002/adsc.201200358
Abstract
A new concept to access unsymmetrical 1,2-diols with high yields is reported. This new methodology is based on a retropinacol/cross-pinacol coupling process. This transformation is characterized by its operational simplicity and very mild reaction conditions.
Co-reporter:Ulf Scheffler
Helvetica Chimica Acta 2012 Volume 95( Issue 10) pp:1970-1975
Publication Date(Web):
DOI:10.1002/hlca.201200402
Abstract
A new catalytic retro-pinacol/cross-pinacol reaction, followed by subsequent rearrangement or deoxygenation of the intermediately formed vicinal diols, is described. This operationally simple one-pot protocol allows isolation of geminal α,α-diphenyl ketones or 1,1-diphenyl alkenes with high yields and selectivities.
Co-reporter:Ulf Scheffler and Rainer Mahrwald
The Journal of Organic Chemistry 2012 Volume 77(Issue 5) pp:2310-2330
Publication Date(Web):February 6, 2012
DOI:10.1021/jo202558f
Extensive studies of asymmetric cross-aldol addition between enolizable aldehydes are described and provide a deeper insight into histidine-catalyzed aldol additions. In particular, aspects of enantio- as well as diastereoselectivity of these reactions are discussed. Rules and predictions of configurative outcome are explained by using different transition-state models. These discussions are confirmed by extensive computations.
Co-reporter:Andrea Seifert, Kerstin Rohr, Rainer Mahrwald
Tetrahedron 2012 68(4) pp: 1137-1144
Publication Date(Web):
DOI:10.1016/j.tet.2011.11.069
Co-reporter:Andrea Seifert, Ulf Scheffler, Morris Markert and Rainer Mahrwald
Organic Letters 2010 Volume 12(Issue 8) pp:1660-1663
Publication Date(Web):March 21, 2010
DOI:10.1021/ol100093u
A highly, stereo- and regioselective Meerwein−Ponndorf−Verley−Aldol etherification process of enolizable aldehydes is described. This new transformation is catalyzed by trifluoroacetic acid. The method also allows cross-aldol reactions with α-branched enolizable aldehydes and thus provides access to defined configured quaternary stereogenic centers.
Co-reporter:Morris Markert ; Ulf Scheffler
Journal of the American Chemical Society 2009 Volume 131(Issue 46) pp:16642-16643
Publication Date(Web):October 30, 2009
DOI:10.1021/ja907054y
A histidine-catalyzed asymmetric direct cross-aldol reaction of enolizable aldehydes is described. In contrast to proline, histidine is able to clearly differentiate the reactivity of various aldehydes. In addition, this approach provides access to syn-configured β-hydroxyaldehydes. Thus, by application of this new methodology, defined-configuration quaternary stereocenters can be constructed with ease. The utility of this method is demonstrated in several total syntheses of branched-chain carbohydrates.
Co-reporter:Kerstin Rohr, Rainer Mahrwald
Bioorganic & Medicinal Chemistry Letters 2009 Volume 19(Issue 14) pp:3949-3951
Publication Date(Web):15 July 2009
DOI:10.1016/j.bmcl.2009.03.040
An efficient tandem aldol condensation/Michael addition process of unactivated aldehydes and 1,3-cyclohexanedione is described. This transformation proceeds without any catalyst at room temperature with high isolated yields. By a fine-tuning of reaction conditions an access to both the aldol condensation/Michael addition products or to the dehydrated cyclized 9-substituted 1,8-dioxo-xanthenes is given.Catalyst-free tandem aldol condensation/Michael addition of enolizable aldehydes with 1,3-cyclohexanediones are described.
Co-reporter:Kerstin Rohr, Robert Herre and Rainer Mahrwald
The Journal of Organic Chemistry 2009 Volume 74(Issue 10) pp:3744-3749
Publication Date(Web):April 21, 2009
DOI:10.1021/jo9003635
Asymmetric aldol-Tishchenko reactions of enolizable aldehydes and ketones in the presence of chiral BINOLTi(OtBu)2/cinchona alkaloids complexes are described. Different configurative outcomes of these reactions depend on an equilibration through a retro aldol/aldol sequence and can be influenced by the configurative architecture of substrates. The results are explained by means of transition state models and rate constants. These considerations offer a fine-tuning of diastereoselectivity in aldol-Tishchenko reactions. Extensions of this research give access to defined configured stereotriads, stereotetrads, and stereopentads.
Co-reporter:Andrea Seifert, Rainer Mahrwald
Tetrahedron Letters 2009 50(47) pp: 6466-6468
Publication Date(Web):
DOI:10.1016/j.tetlet.2009.09.009
Co-reporter:Kerstin Rohr
Advanced Synthesis & Catalysis 2008 Volume 350( Issue 18) pp:2877-2880
Publication Date(Web):
DOI:10.1002/adsc.200800554
Abstract
Solvent- and catalyst-free aldol additions of activated aldehydes to 1,3-dicarbonyl compounds are described. Aldol condensation was not observed under these reaction conditions. This unexpected aldol reaction could be extended successfully to a variety of acyclic and cyclic β-dicarbonyl compounds.
Co-reporter:Rainer Mahrwald
Advanced Synthesis & Catalysis 2007 Volume 349(Issue 10) pp:
Publication Date(Web):17 JUL 2007
DOI:10.1002/adsc.200700169
Co-reporter:Rainer Mahrwald
Advanced Synthesis & Catalysis 2007 Volume 349(Issue 3) pp:
Publication Date(Web):2 FEB 2007
DOI:10.1002/adsc.200600571
Co-reporter:Bernd Schetter;Christoph Stosiek;Burkhard Ziemer
Applied Organometallic Chemistry 2007 Volume 21(Issue 3) pp:
Publication Date(Web):30 JAN 2007
DOI:10.1002/aoc.1183
Hexa- and nonanuclear titanium complexes were obtained by self-assembly of titanium(IV)-tert-butoxide and D-mandelic acid. Suitable single crystals of these complexes were characterized by X-ray structure analysis. When used with these complexes, aldol adducts were isolated with a high degree of regioselectivity in direct aldol additions of aromatic and aliphatic aldehydes to functionalized unsymmetrical ketones. High syn-diastereoselectivities were obtained in aldol additions of enolizable aldehydes with hydroxyacetone and methoxyacetone. Copyright © 2007 John Wiley & Sons, Ltd.
Co-reporter:Morris Markert Dr.
Chemistry - A European Journal 2007 Volume 14( Issue 1) pp:40-48
Publication Date(Web):
DOI:10.1002/chem.200701334
Abstract
The selective total synthesis of carbohydrates with defined configuration has been of great interest for a long time. This field has been the domain of enzymatic methods so far. But now the recent development of several organocatalyzed aldol methodologies has made a selective synthetic approach to configuratively defined carbohydrates possible. This development and different strategies will be discussed in this concept article.
Co-reporter:A. Bartels;R. Mahrwald;K. Müller
Advanced Synthesis & Catalysis 2004 Volume 346(Issue 4) pp:
Publication Date(Web):13 APR 2004
DOI:10.1002/adsc.200303200
The catalytic transformation of propargylic acetates into the corresponding α-acetoxyenones in the presence of palladium(II) chloride is described. Water is a necessary component in this unusual oxidative rearrangement.
Co-reporter:Rainer Mahrwald Priv.-Doz. Dr.
Angewandte Chemie 2003 Volume 115(Issue 22) pp:
Publication Date(Web):5 JUN 2003
DOI:10.1002/ange.200390502
Co-reporter:Rainer Mahrwald Priv.-Doz. Dr.
Angewandte Chemie International Edition 2003 Volume 42(Issue 22) pp:
Publication Date(Web):5 JUN 2003
DOI:10.1002/anie.200390475
Co-reporter:Rainer Mahrwald Priv.-Doz. Dr.
Angewandte Chemie 2002 Volume 114(Issue 8) pp:
Publication Date(Web):16 APR 2002
DOI:10.1002/1521-3757(20020415)114:8<1423::AID-ANGE1423>3.0.CO;2-2
Wesentlich beweglicher als allgemein angenommen sind Wasserstoffatome tertiärer Butylgruppen. Unter sehr milden und sauren Bedingungen reagieren Aldehyde mit Ti(OtBu)4 in Gegenwart von LiClO4 und α-Hydroxysäuren zu Diolen (siehe Schema).
Co-reporter:Rainer Mahrwald Priv.-Doz. Dr.
Angewandte Chemie International Edition 2002 Volume 41(Issue 8) pp:
Publication Date(Web):16 APR 2002
DOI:10.1002/1521-3773(20020415)41:8<1361::AID-ANIE1361>3.0.CO;2-S
Mobile hydrogen atoms: The hydrogen atoms of tertiary butyl groups are significantly more mobile than is generally assumed. Under very mild and acidic conditions aldehydes react with Ti(OtBu)4 to form diols in the presence of LiClO4 and α-hydroxy acid (see scheme).
Co-reporter:Rainer Mahrwald
Drug Discovery Today: Technologies (Spring 2013) Volume 10(Issue 1) pp:e29-e36
Publication Date(Web):1 March 2013
DOI:10.1016/j.ddtec.2012.08.001
Beyond doubt organocatalysis belongs to the most exciting and innovative chapters of organic chemistry today. Organocatalysis has emerged not only as a complement to metal-catalyzed reactions or to biocatalysis over the past decade, but also new asymmetric organocatalyzed reactions have been discovered that could not be accomplished by metal- or biocatalyzed reactions so far. This review gives a brief overview of organocatalyzed asymmetric CC bond formation processes currently available.
Co-reporter:Benjamin Voigt and Rainer Mahrwald
Chemical Communications 2014 - vol. 50(Issue 7) pp:NaN819-819
Publication Date(Web):2013/11/13
DOI:10.1039/C3CC48120D
An organocatalyzed transformation to elongate unprotected carbohydrates is described. This operationally simple methodology is based on a Knoevenagel–oxa-Michael cascade. This reaction is catalyzed by proline and DBU. Products were obtained with exceptional high degrees of stereoselectivity.
Co-reporter:Benjamin Voigt, Ulf Scheffler and Rainer Mahrwald
Chemical Communications 2012 - vol. 48(Issue 43) pp:NaN5306-5306
Publication Date(Web):2012/03/27
DOI:10.1039/C2CC31541F
Aldol additions of unprotected carbohydrates to 1.3-dicarbonyl compounds have been described. This transformation is based on a dual activation by tertiary amines and 2-hydroxypyridine.