Continuous-flow catalytic asymmetric hydrogenations: Reaction optimization using FTIR inline analysis

• Magnus Rueping,
• Teerawut Bootwicha and
• Erli Sugiono

Beilstein J. Org. Chem. 2012, 8, 300–307, doi:10.3762/bjoc.8.32

• hydrogenation. Asymmetric hydrogenation of benzoxazines. Optimization of the Brønsted acid catalyzed reduction of benzoxazines.a Scope of the Brønsted acid catalyzed reduction of benzoxazines.a Optimization of the Brønsted acid catalyzed transfer hydrogenation of quinolines.a Scope of the Brønsted acid

Efficient and selective chemical transformations under flow conditions: The combination of supported catalysts and supercritical fluids

• M. Isabel Burguete,
• Eduardo García-Verdugo and
• Santiago V. Luis

Beilstein J. Org. Chem. 2011, 7, 1347–1359, doi:10.3762/bjoc.7.159

• mobile phase to deliver the reactants to the IL phase and to extract the products from there can be easily designed. This approach has been recently used to carry out the asymmetric hydrogenation of dimethyl itaconate. A chiral organometallic catalyst was immobilized on a IL phase absorbed onto a

A practical two-step procedure for the preparation of enantiopure pyridines: Multicomponent reactions of alkoxyallenes, nitriles and carboxylic acids followed by a cyclocondensation reaction

• Christian Eidamshaus,
• Roopender Kumar,
• Mrinal K. Bera and
• Hans-Ulrich Reissig

Beilstein J. Org. Chem. 2011, 7, 962–975, doi:10.3762/bjoc.7.108

• metal-catalyzed processes and for the construction of supramolecular architectures [13]. Pyridines with chiral side chains are widely employed as ligands in asymmetric transformations, for instance, in the asymmetric hydrogenation of olefins, in enantioselective additions of metal organyls to aldehydes

A two step synthesis of a key unit B precursor of cryptophycins by asymmetric hydrogenation

• Benedikt Sammet,
• Mathilde Brax and
• Norbert Sewald

Beilstein J. Org. Chem. 2011, 7, 243–245, doi:10.3762/bjoc.7.32

• yields from commercially available starting materials has been developed. The key step is an asymmetric hydrogenation using the commercially available [(COD)Rh-(R,R)-Et-DuPhos]BF4 catalyst. The synthetic route provides the advantage of less synthetic steps, proceeds with high yields and

• enantioselectivity, and avoids hazardous reaction conditions. Keywords: amino acid; asymmetric hydrogenation; cryptophycin; DuPhos; Introduction Cryptophycins are macrocyclic depsipeptides, which show very high cytotoxicity even against multidrug-resistant cell lines. They inhibit mitosis of eukaryotic cells by

• unit B precursor 4 (Scheme 1) from commercially available non-toxic starting materials based on an asymmetric hydrogenation approach to make the unit B precursor synthesis shorter and safer. In general, there is also a whole variety of possible stereoselective synthetic methods available to synthesize

Can we measure catalyst efficiency in asymmetric chemical reactions? A theoretical approach

• Shaimaa El-Fayyoumy,
• Matthew H. Todd and
• Christopher J. Richards

Beilstein J. Org. Chem. 2009, 5, No. 67, doi:10.3762/bjoc.5.67

• asymmetric hydrogenation, which gives a product of 79% ee, is employed in the industrial multi-tonne synthesis of (S)-metolachlor [3]. An instructive comparison may be made between an antibody capable of catalysing an intramolecular, asymmetric aldol reaction and proline, capable of catalysing the same

• extraordinary efficiency of ligated transition metal catalysts in asymmetric hydrogenation. An analysis of the unit cost of each catalyst reveals these to span a very wide range, with only the amino acid proline comparing favourably with the hydrogenation systems. The ACE formula permits a comparison between

Asymmetric reactions in continuous flow

• Xiao Yin Mak,
• Paola Laurino and
• Peter H. Seeberger

Beilstein J. Org. Chem. 2009, 5, No. 19, doi:10.3762/bjoc.5.19

• observed to be higher in the microreactor. A single-channel, falling film microreactor designed specifically for efficient gas-liquid phase contact was used to screen the asymmetric hydrogenation of (Z)-methyl acetamidocinnamate 4 and related substrates (Scheme 2) [13][14]. Seventeen chiral phosphines were

• alternative reaction medium to traditional organic solvents is attractive not only for environmental reasons, but also because of its high miscibility with gases, and its ease of removal from the product (simply by depressurization) [46]. In an early example of asymmetric hydrogenation in flow, ethyl pyruvate

• was reduced using a cinchonidine-modified Pt/Al2O3 catalyst in a fixed bed reactor in both supercritical carbon dioxide and ethane [47]. Poliakoff and co-workers have investigated the continuous asymmetric hydrogenation of dimethyl itaconate in scCO2 [48][49]. By using the catalyst [Rh(COD)2(nbd

Large- scale ruthenium- and enzyme- catalyzed dynamic kinetic resolution of (rac)-1-phenylethanol

• Krisztián Bogár,
• Belén Martín-Matute and
• Jan-E. Bäckvall

Beilstein J. Org. Chem. 2007, 3, No. 50, doi:10.1186/1860-5397-3-50

• natural products. [1][2][3][4] A few methods have been developed for the enantioselective synthesis of chiral alcohols including catalytic asymmetric hydrogenation [5][6][7][8][9][10][11][12][13][14] and enantioselective hydride addition [15][16] of prochiral ketones, asymmetric dialkylzinc addition to