138306-24-8Relevant academic research and scientific papers
Metathesis for catalyst design: Metacatalysis
Khumsubdee, Sakunchai,Burgess, Kevin
, p. 1326 - 1335 (2014/02/14)
Prior studies have shown an effective way to produce diverse ligand sets for catalyst discovery is by using mixtures of monodentate forms to generate catalysts in situ. Research described here was performed to illustrate that alkene-functionalized monodentate ligands could be used in this way and in another that increases the diversity of the ligand library in an interesting way. Specifically, we hypothesized that as well as being used as monomers, these alkenes could be cross metathesized in situ immediately before the catalysis step. This combination of metathesis to form ligands in situ, then catalysis is referred to here as metacatalysis. In the event, a library of quinidine and quinine alkaloid-derived phosphites were tested as mixtures of monomers and dimers formed via metathesis in situ. The data obtained illustrated that metacatalysis can be used to identify ligands that positively and negatively modulate enantioselectivities in iridium-mediated hydrogenations of α,β-unsaturated carboxylic acid derivatives, relative to the mixtures of the monomeric forms used.
Homo-Roche ester derivatives by asymmetric hydrogenation and organocatalysis
Khumsubdee, Sakunchai,Zhou, Hua,Burgess, Kevin
, p. 11948 - 11955 (2014/01/06)
Asymmetric hydrogenation routes to homologues of The Roche ester tend to be restricted to hydrogenations of itaconic acid derivatives, that is, substrates that contain a relatively unhindered, 1,1-disubstituted alkene. This is because in hydrogenations mediated by RhP2 complexes, the typical catalysts, it is difficult to obtain high conversions using the alternative substrate for the same product, the isomeric trisubstituted alkenes (D in the text). However, chemoselective modification of the identical functional groups in itaconic acid derivatives are difficult; hence, it would be favorable to use the trisubstituted alkene. Trisubstituted alkene substrates can be hydrogenated with high conversions using chiral analogs of Crabtree's catalyst of the type IrN(carbene). This paper demonstrates that such reactions are scalable (tens of grams) and can be manipulated to give optically pure homo-Roche ester chirons. Organocatalytic fluorination, chlorination, and amination of the homo-Roche building blocks was performed to demonstrate that they could easily be transformed into functionalized materials with two chiral centers and α,ω-groups that provide extensive scope for modifications. A synthesis of (S,S)- and (R,S)-γ-hydroxyvaline was performed to illustrate one application of the amination product.
A comparison between oxazoline-imidazolinylidene, -imidazolylidine, -benzimidazolylidene hydrogenation catalysts
Khumsubdee, Sakunchai,Fan, Yubo,Burgess, Kevin
, p. 9969 - 9974 (2013/10/22)
Imidazolinylidene, imidazolylidine, benzimidazolylidene complexes 1a-c were prepared and tested in asymmetric hydrogenations of a series of largely unfunctionalized alkenes. Similarities and differences in the catalytic performance of these complexes were rationalized in terms of the predicted mechanisms of these reactions, and their relative tendencies to generate protons under the hydrogenation conditions.
A ring-closing metathesis approach to cyclic α,β-dehydroamino acids
Hekking, Koen F. W.,Waalboer, Dennis C. J.,Moelands, Marcel A. H.,Van Delft, Floris L.,Rutjes, Floris P. J. T.
supporting information; experimental part, p. 95 - 106 (2009/04/10)
A comprehensive study on the synthesis and ring-closing metathesis (RCM) of α,β-dehydroamino acids is described. This sequence has led to the formation of a range of biologically relevant functionalized nitrogen heterocycles. The incorporation of chiral b
Total syntheses of amphidinolide H and G
Fuerstner, Alois,Bouchez, Laure C.,Funel, Jacques-Alexis,Liepins, Vilnis,Poree, Francois-Hugues,Gilmour, Ryan,Beaufils, Florent,Laurich, Daniel,Tamiya, Minoru
, p. 9265 - 9270 (2008/12/22)
(Chemical Equation Presented) Eureka! The first conquest of the exceptionally potent cytotoxic agent amphidinolide H, which exhibits activity in the picomolar range against human epidermoid cancer cells, was long overdue. The successful route critically h
Highly enantioselective rhodium-catalyzed hydrogenation of 2-(2-methoxy-2-oxoethyl)acrylic acid - A convenient access of enantiomerically pure isoprenoid building blocks
Ostermeier, Markus,Brunner, Bernhard,Korff, Christian,Helmchen, Guenter
, p. 3453 - 3459 (2007/10/03)
Asymmetric catalytic hydrogenation of 2-(2-methoxy-2-oxoethyl)acrylic acid (5) to give (2S)-4-methoxy-2-methyl-4-oxobutanoic acid [(S)-6] was studied. An enantiomeric excess of 99.7% ee was achieved with a catalyst formed in situ from [Rh(COD)2]BF4 and the chiral phosphite L2 in 1,2-dichloroethane as solvent. In addition, enzyme-catalyzed semi-saponification of dimethyl 2-methylsuccinate was investigated. Mono ester (S)-6 was transformed into a few compounds which can serve as C 5-building blocks in natural product syntheses. Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003.
