Hierarchically assembled helicates as reaction platform – from stoichiometric Diels–Alder reactions to enamine catalysis

• David Van Craen,
• Jenny Begall,
• Johannes Großkurth,
• Leonard Himmel,
• Oliver Linnenberg,
• Elisabeth Isaak and
• Markus Albrecht

Beilstein J. Org. Chem. 2020, 16, 2338–2345, doi:10.3762/bjoc.16.195

• processes based on the principle to use self-assembled coordination platforms (or as in the present case mixtures thereof) to control stereoselective C–C bond-forming reactions. Stereoinduction usually relies on spatial proximity of the prochiral carbon atoms and a chiral information of, e.g., a chiral

NHC-catalyzed enantioselective synthesis of β-trifluoromethyl-β-hydroxyamides

• Alyn T. Davies,
• Mark D. Greenhalgh,
• Alexandra M. Z. Slawin and
• Andrew D. Smith

Beilstein J. Org. Chem. 2020, 16, 1572–1578, doi:10.3762/bjoc.16.129

• stereogenic trifluoromethyl centers is through enantioselective addition of enolates or their equivalents to prochiral trifluoromethyl ketones (Figure 1A). Within this area, a common catalytic approach has utilized aliphatic ketones as enolate equivalents using prolinamide, cinchona, or hybrid catalysts that

A review of asymmetric synthetic organic electrochemistry and electrocatalysis: concepts, applications, recent developments and future directions

• Munmun Ghosh,
• Valmik S. Shinde and
• Magnus Rueping

Beilstein J. Org. Chem. 2019, 15, 2710–2746, doi:10.3762/bjoc.15.264

• of a poly-ʟ-valine 6 coated graphite cathode for asymmetric electrochemical reductions in two consecutive reports. In the first communication, they carried out the asymmetric reduction of prochiral activated olefins 5 and 8, affording 7 and 9 with optical yields of 25% and 43%, respectively (Scheme 3

• ) [23]. In the second report, the same electrode was applied for the asymmetric reduction of prochiral carbonyl compounds 10a and 12a, oximes 14 and gem-dibromo compounds 16 (Scheme 4). Among all of these the highest optical yield (16.6%) was obtained in the reduction of gem-dibromide substrates 16 to

• catalyze the enantioselective hydrogenation of prochiral ketones 18. The prochiral ketones such as acetophenone, 1-tetralone and 1-indanone were reduced to their corresponding alcohols 20a, 20b and 20c, respectively, with moderate optical yields, with formation of (S) as major enantiomer (Scheme 5). After

Chiral terpene auxiliaries V: Synthesis of new chiral γ-hydroxyphosphine oxides derived from α-pinene

• Anna Kmieciak and
• Marek P. Krzemiński

Beilstein J. Org. Chem. 2019, 15, 2493–2499, doi:10.3762/bjoc.15.242

• ligands that were obtained from readily available natural (1S)-β-pinene and (1S)-α-pinene [18]. We applied these ligands for the formation of the ruthenium complexes, which were successfully used as catalysts in asymmetric transfer hydrogenation of prochiral ketones. In continuation of our studies on the

Self-assembled coordination thioether silver(I) macrocyclic complexes for homogeneous catalysis

• Zhen Cao,
• Aline Lacoudre,
• Cybille Rossy and
• Brigitte Bibal

Beilstein J. Org. Chem. 2019, 15, 2465–2472, doi:10.3762/bjoc.15.239

• . These silver(I) complexes adopted similar structures in solution and in the solid state. As each sulfur atom in the ligand is prochiral, macrocycles L2M2 were obtained as mixtures of diastereoisomers, depending on the configurations of the sulfur atoms coordinated to silver cations. The X-ray structures

• ; homogeneous catalysis; prochiral; silver complex; thioether ligand; Introduction Since the early advances in the late eighties [1][2][3][4][5][6][7][8][9][10], silver(I) catalysis has been widely exploited based on the versatile redox and soft Lewis acid properties of this coinage metal cation. Silver

• prochiral sulfur atom of the ligand becomes asymmetric by coordination to silver(I). In absence of any chiral source, the complexes were obtained either as nonchiral coordination products with a center or an axis of symmetry (1a and 1c, with (R,S)–1 ligands) or as a racemic mixture (1d, with (R,R)–1 or (S,S

Asymmetric synthesis of a high added value chiral amine using immobilized ω-transaminases

• Antonella Petri,
• Valeria Colonna and
• Oreste Piccolo

Beilstein J. Org. Chem. 2019, 15, 60–66, doi:10.3762/bjoc.15.6

• prochiral precursor 1-Boc-3-piperidone using immobilized ω-transaminases (TAs-IMB), isopropylamine as amine donor and pyridoxal-5’-phosphate (PLP) as cofactor is described. Compared to other methods, the present approach affords the target compound in just one step with high yield and high enantiomeric

• by using resolution of racemic mixtures, preparation from chiral precursors or asymmetric synthesis from prochiral compounds [20][21][22]. In contrast, only few examples have been published on the synthesis of this molecule through biotransformations [23][24]. In these procedures TAs are used in

Ruthenium-based olefin metathesis catalysts with monodentate unsymmetrical NHC ligands

• Veronica Paradiso,
• Chiara Costabile and
• Fabia Grisi

Beilstein J. Org. Chem. 2018, 14, 3122–3149, doi:10.3762/bjoc.14.292

•  31). The catalytic performances of 164 were tested in the asymmetric ring-closing metathesis (ARCM) of prochiral trienes 166, 168 and 170 (Scheme 15, Table 6) [52][54] achieving enantiomeric excesses (ee) that were generally lower with respect to those obtained with the C2-symmetrical analogue 165

Stereoselective total synthesis and structural revision of the diacetylenic diol natural products strongylodiols H and I

• Pamarthi Gangadhar,
• Sayini Ramakrishna,
• Ponneri Venkateswarlu and
• Pabbaraja Srihari

Beilstein J. Org. Chem. 2018, 14, 2313–2320, doi:10.3762/bjoc.14.206

• 25 and 25a was oxidized under Dess–Martin conditions to give the prochiral ene–yne–one 17 in 87% yield. The ketone 17 was then subjected to a stereoselective asymmetric reduction [23][29][30][31] in the presence of (S)-CBS as the catalyst to yield the chiral propargylic alcohol 25 with 92% ee (Scheme

• natural product as 9a which is the enantiomer of the proposed structure 9 (Figure 3). Further, to reconfirm the structural revision, we synthesized the other enantiomer of strongylodiol H. Towards this we proceeded for the stereoselective reduction of prochiral ketone 17 with (R)-CBS as the catalyst

Calix[6]arene-based atropoisomeric pseudo[2]rotaxanes

• Carmine Gaeta,
• Carmen Talotta and
• Placido Neri

Beilstein J. Org. Chem. 2018, 14, 2112–2124, doi:10.3762/bjoc.14.186

• threading a tertiary ammonium axles in a directional (non-flat) calixarene-wheel (II and II*, Figure 1) [17]. In this case the chirality is created by the directionality of the calixarene wheel in a cone conformation, which differentiates the two alkyl chains around the prochiral ammonium center. In 2010

D-Fructose-based spiro-fused PHOX ligands: synthesis and application in enantioselective allylic alkylation

• Michael R. Imrich,
• Jochen Kraft,
• Cäcilia Maichle-Mössmer and
• Thomas Ziegler

Beilstein J. Org. Chem. 2018, 14, 2082–2089, doi:10.3762/bjoc.14.182

• enantioselectivity [1][2]. Probably the most effective approach in stereoselective synthesis is enantioselective catalysis, because cheap prochiral starting materials can be converted into chiral enantiopure products and no undesirable side products are formed [3][4]. Therefore, the development of new ligands is

Recent advances in hypervalent iodine(III)-catalyzed functionalization of alkenes

• Xiang Li,
• Pinhong Chen and
• Guosheng Liu

Beilstein J. Org. Chem. 2018, 14, 1813–1825, doi:10.3762/bjoc.14.154

• environment at the iodine center. Mechanistically, the iodine(III) 16 is activated by triflic acid generating a free coordination site at the iodine(III) center [54]. The coordination of the alkene to the activated iodine(III) center generates the required prochiral face differentiation and the nucleophilic

Mechanochemical synthesis of small organic molecules

• Tapas Kumar Achar,
• Anima Bose and
• Prasenjit Mal

Beilstein J. Org. Chem. 2017, 13, 1907–1931, doi:10.3762/bjoc.13.186

• reaction under mechanomilling [67]. Asymmetric alkynylation of prochiral sp3 C–H bonds via CDC [68]. Fe(III)-catalyzed CDC coupling of 3-benzylindoles [69]. Mechanochemical synthesis of 3-vinylindoles and β,β-diindolylpropionates [70]. Mechanochemical C–N bond construction using anilines and arylboronic

Chiral phase-transfer catalysis in the asymmetric α-heterofunctionalization of prochiral nucleophiles

• Johannes Schörgenhumer,
• Maximilian Tiffner and
• Mario Waser

Beilstein J. Org. Chem. 2017, 13, 1753–1769, doi:10.3762/bjoc.13.170

• variety of different catalysts and their use for challenging applications have been reported over the last decades. Besides asymmetric C–C bond forming reactions the use of chiral phase-transfer catalysts for enantioselective α-heterofunctionalization reactions of prochiral nucleophiles became one of the

• major advantages of all these chiral cation-based phase-transfer catalysts (Q+ X−) is their unique potential to control the reactivity of a broad variety of different prochiral nucleophiles (i.e., enolates) via formation of chiral ion pairs, which can then undergo stereoselective α-functionalization

• reactions with different electrophiles (Scheme 1). A lot of different examples for such asymmetric α-functionalization reactions of prochiral nucleophiles under asymmetric chiral cation-based phase-transfer catalysis have been reported so far [9][10][11][12][13][14][15][16][17][18][19][20][21][22]. Besides

Aqueous semisynthesis of C-glycoside glycamines from agarose

• Juliana C. Cunico Dallagnol,
• Alexandre Orsato,
• Diogo R. B. Ducatti,
• Miguel D. Noseda,
• Maria Eugênia R. Duarte and
• Alan G. Gonçalves

Beilstein J. Org. Chem. 2017, 13, 1222–1229, doi:10.3762/bjoc.13.121

• , spectrum in red). Aside from the N-methyl chemical shifts, NMR signals are otherwise indistinguishable for both epimers. This result indicated that even with prochiral C-2 of 10 being surrounded by a covalently linked chiral environment, no internal asymmetric induction took place during the reduction. The

• intermediate (not shown), instead of with a prochiral enamine intermediate (such is the case of 10). Specific rotation values ([α]D) endorsed the above mentioned configuration aspects. Comparison of the 1H NMR assignments shown by 3, 7 and 8 indicated that the extra methyl appendices on amino group had impact

Phosphazene-catalyzed desymmetrization of cyclohexadienones by dithiane addition

• Matthew A. Horwitz,
• Elisabetta Massolo and
• Jeffrey S. Johnson

Beilstein J. Org. Chem. 2017, 13, 762–767, doi:10.3762/bjoc.13.75

• reduction of prochiral cyclohexadienones using copper hydride generated in situ [23]. Inspired by these advances, we sought to develop an alternative and complementary method invoking the dithiane moiety as an established and easily accessible glyoxylate anion surrogate [24][25][26][27][28][29]. This would

Highly chemo-, enantio-, and diastereoselective [4 + 2] cycloaddition of 5H-thiazol-4-ones with N-itaconimides

• Shuai Qiu,
• Choon-Hong Tan and
• Zhiyong Jiang

Beilstein J. Org. Chem. 2016, 12, 2293–2297, doi:10.3762/bjoc.12.222

• prochiral carbon centers can be considered to be one of the most efficient and expedient approach [1][2][3][4]. The development of novel S-containing substrates has therefore attracted the attention of chemists [1][2][3][4]. For example in 2013, Palomo and co-workers introduced 5H-thiazol-4-ones as a new

Enantioconvergent catalysis

• Justin T. Mohr,
• Jared T. Moore and
• Brian M. Stoltz

Beilstein J. Org. Chem. 2016, 12, 2038–2045, doi:10.3762/bjoc.12.192

• processes in which a racemic starting material is irreversibly transformed into an achiral intermediate that subsequently undergoes an enantioselective conversion to the product. Reports of this type are predominantly in the areas of prochiral enolates and prochiral metal π-allyl complexes [19][20][21

Conjugate addition–enantioselective protonation reactions

• James P. Phelan and
• Jonathan A. Ellman

Beilstein J. Org. Chem. 2016, 12, 1203–1228, doi:10.3762/bjoc.12.116

• researchers have developed methods for the stereoselective synthesis of tertiary carbon stereocenters. One aesthetically pleasing approach is the enantioselective protonation of prochiral enolates and enolate equivalents [1][2][3][4][5][6][7][8][9][10]. While an attractive strategy, the enantioselective

• -stereoselective step allows for the generation of a prochiral enolate intermediate that then undergoes enantioselective protonation (Figure 1). Two general strategies can be used when applying a conjugate addition–enantioselective protonation manifold. In the first strategy, a chiral enolate can be protonated by

1H-Imidazol-4(5H)-ones and thiazol-4(5H)-ones as emerging pronucleophiles in asymmetric catalysis

• Antonia Mielgo and
• Claudio Palomo

Beilstein J. Org. Chem. 2016, 12, 918–936, doi:10.3762/bjoc.12.90

• ] pronucleophiles to γ-substituted allenoates and/or alkynoates in the presence of a C2-symmetric chiral phosphine catalyst. Although γ-substituted allenes have been employed in many phosphine-mediated γ-additions, to date there was virtually no progress on the use of prochiral pronucleophiles in phosphine-mediated

The aminoindanol core as a key scaffold in bifunctional organocatalysts

• Isaac G. Sonsona,
• Eugenia Marqués-López and
• Raquel P. Herrera

Beilstein J. Org. Chem. 2016, 12, 505–523, doi:10.3762/bjoc.12.50

• by the catalyst ent-6 through hydrogen-bonding interactions in a bifunctional manner. Thus, the ternary complex formed in the transition state TS5 leads to an enantioselective Friedel–Crafts-type Michael addition by the attack of indole 2 to the electrophilic prochiral center on the nitroalkene 20 in

(Thio)urea-mediated synthesis of functionalized six-membered rings with multiple chiral centers

• Giorgos Koutoulogenis,
• Nikolaos Kaplaneris and
• Christoforos G. Kokotos

Beilstein J. Org. Chem. 2016, 12, 462–495, doi:10.3762/bjoc.12.48

• prochiral ketones 35 or 36, catalyzed by a primary amine-thiourea 37 developed by Jacobsen. The proposed pathway is based on desymmetrization of 35 or 36 by an intramolecular Michael addition of the corresponding enamines to an α,β-unsaturated ester, to yield bicyclic or spiro-bicyclic products 38 and 39

A novel and practical asymmetric synthesis of dapoxetine hydrochloride

• Yijun Zhu,
• Zhenren Liu,
• Hongyan Li,
• Deyong Ye and
• Weicheng Zhou

Beilstein J. Org. Chem. 2015, 11, 2641–2645, doi:10.3762/bjoc.11.283

• encompass asymmetric dihydroxylation of trans-methyl cinnamate or cinnamyl alcohol [6], chiral azetidin-2,3-dione [7], asymmetric C–H amination reactions of a prochiral sulfamate [8], oxazaborolidine reduction of 3-chloropropiophenone or ketone [9], and an imidazolidin-2-one chiral auxiliary mediated

Organocatalytic and enantioselective Michael reaction between α-nitroesters and nitroalkenes. Syn/anti-selectivity control using catalysts with the same absolute backbone chirality

• Jose I. Martínez,
• Uxue Uria,
• Maria Muñiz,
• Efraím Reyes,
• Luisa Carrillo and
• Jose L. Vicario

Beilstein J. Org. Chem. 2015, 11, 2577–2583, doi:10.3762/bjoc.11.277

• , in which the nitronate moiety exposes a different reactive prochiral face. These results are in good agreement with our previously reported work in which DFT calculations also showed that the difference in the steric bulk of the nitrogen substituents of the Brønsted basic site of the catalysts (the

A comprehensive study of olefin metathesis catalyzed by Ru-based catalysts

• Albert Poater and
• Luigi Cavallo

Beilstein J. Org. Chem. 2015, 11, 1767–1780, doi:10.3762/bjoc.11.192

• two prochiral faces of the C=C bond in 14–19, we always found that coordination takes places in the face that presents the two methyl groups pointing away from the NHC ligand. Of course, this results in reduced steric interactions with the NHC ligand. In the trans geometries, instead, the C=C double

The enantioselective synthesis of (S)-(+)-mianserin and (S)-(+)-epinastine

• Piotr Roszkowski,
• Jan. K. Maurin and
• Zbigniew Czarnocki

Beilstein J. Org. Chem. 2015, 11, 1509–1513, doi:10.3762/bjoc.11.164

• more active form [9]. In a key step in the enantioselective synthesis of mianserin and epinastine we applied the asymmetric reduction of the prochiral imine by asymmetric hydrogen transfer reaction (ATH) [10][11][12][13][14]. The proposed strategy could be used for the preparation of the title