Proton transfers in the Strecker reaction revealed by DFT calculations

• Shinichi Yamabe,
• Guixiang Zeng,
• Wei Guan and
• Shigeyoshi Sakaki

Beilstein J. Org. Chem. 2014, 10, 1765–1774, doi:10.3762/bjoc.10.184

• asymmetric Strecker reaction, in which an (S)-α-phenylethylamine was employed as the chiral auxiliary [4]. In this reaction, he obtained a chiral alanine with 95% optically activity; see Scheme 2. In 1996, Lipton et al. succeeded in a series of asymmetric Strecker reactions by employing a chiral catalyst, a

• afforded an initial product Ph-CH(NH2)-CN of configurational instability[5]. In the following, Sigman and Jacobsen used a parallel combinatorial library synthesis for the discovery and optimization of a chiral catalyst for the reaction of imines and HCN [6]. From then on, various catalytic asymmetric

• first asymmetric Strecker reaction [4]. The first asymmetric synthesis of α-aminonitirles via a chiral catalyst [5]. A reaction model composed of Me-CH=O, HCN, NH3 and (H2O)10 for geometry optimizations to trace elementary processes. Broken lines stand for hydrogen bonds. Possible pathways for the

Atherton–Todd reaction: mechanism, scope and applications

• Stéphanie S. Le Corre,
• Mathieu Berchel,
• Hélène Couthon-Gourvès,
• Jean-Pierre Haelters and
• Paul-Alain Jaffrès

Beilstein J. Org. Chem. 2014, 10, 1166–1196, doi:10.3762/bjoc.10.117

• expected phosphoramidate was jointly isolated with 5 to 10% of thiophosphoramidate resulting from a cyclization reaction. The chiral phosphoramidates (Scheme 32-ii and iii) were tested as a chiral catalyst for the nucleophilic addition of diethylzinc [107] on benzaldehyde or for the asymmetric borane

Silver and gold-catalyzed multicomponent reactions

• Giorgio Abbiati and
• Elisabetta Rossi

Beilstein J. Org. Chem. 2014, 10, 481–513, doi:10.3762/bjoc.10.46

• nonsymmetric ketones. Moreover, an optical active compound could be generated during the reaction process since a chiral catalyst (proline) is used in the reactions. However, enantioselectivity was not observed by chiral HPLC analysis, and 3-pentanone gives rise to a mixture of diastereoisomers. Following this

• dealing with the use of BINAP–AgClO4 as a chiral catalyst in the same two-component reaction [98]. Higher enantioselectivities were rarely observed with SbF6− being the weaker coordinating counter ion. An interesting application of silver catalysis in the allene chemistry field has been recently proposed

Exploration of an epoxidation–ring-opening strategy for the synthesis of lyconadin A and discovery of an unexpected Payne rearrangement

• Brad M. Loertscher,
• Yu Zhang and
• Steven L. Castle

Beilstein J. Org. Chem. 2013, 9, 1179–1184, doi:10.3762/bjoc.9.132

• believed that this compound could be prepared from alkene 6 in two consecutive epoxidation–ring-opening sequences involving vinyl nucleophiles. We anticipated that a chiral catalyst such as one of the ketones developed by Shi and co-workers [15][16][17][18] would control the stereochemistry of the

Enantioselective reduction of ketoimines promoted by easily available (S)-proline derivatives

• Martina Bonsignore,
• Maurizio Benaglia,
• Laura Raimondi,
• Manuel Orlandi and
• Giuseppe Celentano

Beilstein J. Org. Chem. 2013, 9, 633–640, doi:10.3762/bjoc.9.71

• studies were also performed in order to elucidate the origin of the stereoselection. Keywords: chiral prolines; imine reduction; Lewis bases; organocatalysis; trichlorosilane; Introduction The reaction with stoichiometric amounts of trichlorosilane in the presence of a chiral catalyst is a well

Efficient synthesis of β’-amino-α,β-unsaturated ketones

• Isabelle Abrunhosa-Thomas,
• Aurélie Plas,
• Nishanth Kandepedu,
• Pierre Chalard and
• Yves Troin

Beilstein J. Org. Chem. 2013, 9, 486–495, doi:10.3762/bjoc.9.52

• under different protocols in which the stereoselectivity of the reaction can be introduced through the use of a chiral catalyst [9][10] (Lewis acid, Brønsted acids, L-proline, Cinchona alkaloids derivatives, thioureas, etc.), or by the addition of chiral amines to α,β-unsaturated esters [11][12] or the

Reactions of salicylaldehyde and enolates or their equivalents: versatile synthetic routes to chromane derivatives

• Ishmael B. Masesane and
• Zelalem Yibralign Desta

Beilstein J. Org. Chem. 2012, 8, 2166–2175, doi:10.3762/bjoc.8.244

• 27. Although Shanti and co-workers used a chiral catalyst, no data was provided on the stereoselectivity of this reaction. In a study related to that of Shanti and co-workers, Yang and co-workers used chiral amine-thiourea catalyst 31 in a three-component enantioselective reaction of salicylaldehyde

Organocatalytic tandem Michael addition reactions: A powerful access to the enantioselective synthesis of functionalized chromenes, thiochromenes and 1,2-dihydroquinolines

• Chittaranjan Bhanja,
• Satyaban Jena,
• Sabita Nayak and
• Seetaram Mohapatra

Beilstein J. Org. Chem. 2012, 8, 1668–1694, doi:10.3762/bjoc.8.191

• %) (Scheme 31). In this cascade reaction, the installation of electron-withdrawing groups on the amino moiety of 2-aminobenzaldehydes is anticipated to increase the aniline N–H acidity, the abstraction of which by the tertiary amine leads to an aza-Michael reaction. The thiourea group in the chiral catalyst

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

• also be driven towards the branched aldehyde. In this case, the resulting compound has a stereogenic center and an enantioselective process can be developed using a chiral catalyst. An example was reported by Shibahara et al. [59]. For this purpose, a chiral catalyst based on polystyrene-supported (PS

Chiral gold(I) vs chiral silver complexes as catalysts for the enantioselective synthesis of the second generation GSK-hepatitis C virus inhibitor

• María Martín-Rodríguez,
• Carmen Nájera,
• José M. Sansano,
• Abel de Cózar and
• Fernando P. Cossío

Beilstein J. Org. Chem. 2011, 7, 988–996, doi:10.3762/bjoc.7.111

• results previously obtained for each chiral catalyst [25][26][28][29][30][33]. According to these results the combination of chiral phosphoramidite and silver(I) salt is much more appropriate than the analogous one made with gold(I) salts. Especially useful is the reaction of (Ra,R)-8/AgSbF6 catalytic

Recent advances in the gold-catalyzed additions to C–C multiple bonds

• He Huang,
• Yu Zhou and
• Hong Liu

Beilstein J. Org. Chem. 2011, 7, 897–936, doi:10.3762/bjoc.7.103

• the Brønsted acid is both a chiral catalyst for the asymmetric cycloaddition and assists to facilitate the gold complex catalyzed hydroamination. Muratore et al. have reported an interesting example of C–N bond formation for the construction of chiral nitrogen-containing fused heterocycles 400 [191

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

• sulfate. A completely different route to unit B precursor 8 (Scheme 2) is based on a phase transfer catalyst (PTC) mediated asymmetric alkylation. However, the required cinchonine derived chiral catalyst is not commercially available [9]. Results and Discussion We envisaged a two step synthesis for the

Kinetics and mechanism of vanadium catalysed asymmetric cyanohydrin synthesis in propylene carbonate

• Michael North and
• Marta Omedes-Pujol

Beilstein J. Org. Chem. 2010, 6, 1043–1055, doi:10.3762/bjoc.6.119

• and β-amino alcohols [2] (Scheme 1). Asymmetric cyanohydrin synthesis can be achieved by the use of a suitable chiral catalyst, and a wide range of catalysts have been found to catalyse this reaction including enzymes [3][4], organocatalysts [5][6] and metal-based catalysts [1]. All of the most

Mitomycins syntheses: a recent update

• Jean-Christophe Andrez

Beilstein J. Org. Chem. 2009, 5, No. 33, doi:10.3762/bjoc.5.33

• circumventing this regioselectivity issue by exploiting the enantioselective intramolecular C–H insertion of diazoester 144 into a meso pyrrolidine using chiral catalyst 145. Unfortunately the reaction displayed low enantio- and diastereoselectivity, with the major isomer 146 having an ee of only 51% (Scheme 40