Non-covalent organocatalyzed enantioselective cyclization reactions of α,β-unsaturated imines

• Sergio Torres-Oya and
• Mercedes Zurro

Beilstein J. Org. Chem. 2024, 20, 3221–3255, doi:10.3762/bjoc.20.268

• -heterocycles using various catalytic systems such as chiral metal catalysts, chiral Lewis acids or chiral organocatalysts. This review presents an overview of the recent advances in enantioselective cyclization reactions of 1-azadienes catalyzed by non-covalent organocatalysts. Keywords: α,β-unsaturated

• covered in this review are hydrogen-bond donors such as thioureas and squaramides, Brønsted bases such as tertiary amines, and Brønsted acids such as chiral phosphoric acids. As depicted in Figure 4, a bifunctional squaramide is able to activate both an α,β-unsaturated imine through hydrogen bonding with

• the squaramide moiety and a nucleophile through deprotonation as Brønsted base. On the other hand, a chiral phosphoric acid provides a confined chiral environment where the reactants are approached, activating both the azadiene by interaction with the acidic hydrogen and a dienophile bearing a

Ceratinadin G, a new psammaplysin derivative possessing a cyano group from a sponge of the genus Pseudoceratina

• Shin-ichiro Kurimoto,
• Kouta Inoue,
• Taito Ohno and
• Takaaki Kubota

Beilstein J. Org. Chem. 2024, 20, 3215–3220, doi:10.3762/bjoc.20.267

• of psammaplysin A remained ambiguous for approximately 30 years but was determined in 2015 by Kurtán, Garson, and co-workers through a comparison of experimental and calculated electronic circular dichroism data, as well as a method employing Trost's chiral anisotropic reagents [6]. More recently

Synthesis of extended fluorinated tripeptides based on the tetrahydropyridazine scaffold

• Thierry Milcent,
• Pascal Retailleau,
• Benoit Crousse and
• Sandrine Ongeri

Beilstein J. Org. Chem. 2024, 20, 3174–3181, doi:10.3762/bjoc.20.262

• strategy, the control of the stereoselectivity of the intramolecular aza-Michael addition could be envisaged with various chiral catalysts in further studies. These heterocyclic hydrazino acids, when incorporated into the peptidic structure, appear to confer an extended conformation. These interesting

Hypervalent iodine-mediated intramolecular alkene halocyclisation

• Charu Bansal,
• Oliver Ruggles,
• Albert C. Rowett and
• Alastair J. J. Lennox

Beilstein J. Org. Chem. 2024, 20, 3113–3133, doi:10.3762/bjoc.20.258

• formed. The use of a chiral aryl iodide was tested, which gave products with low enantiomeric excess. However, these preliminary trials represent the first example of a catalytic, enantioselective HVI-mediated fluorocyclisation. The authors proposed a mechanism (Scheme 4) for this reaction that involved

• from the styrenyl starting materials is stereoselective, giving the syn-diasteroisomer in high yields. A chiral iodoarene catalyst 16 was employed, along with a stoichiometric sacrificial oxidant, to give good to excellent levels of enantioselectivity. This elegant strategy led to a variety of β

• aminofluorination using BF3·Et2O with a chiral aryliodide 16 catalyst (Scheme 20) [44]. The study successfully obtained various chiral fluorinated oxazine products 38 with high enantioselectivity (up to >99% ee) and diastereoselectivity (up to >20:1 dr). Control experiments showed that using Py·9HF or Et3N·3HF as

Advances in the use of metal-free tetrapyrrolic macrocycles as catalysts

• Mandeep K. Chahal

Beilstein J. Org. Chem. 2024, 20, 3085–3112, doi:10.3762/bjoc.20.257

• enantiomeric excess (ee) up to 5.5% [70]. Related catalytic systems based on amphiphilic 5-(cyclic-secondary-amine)-10,15,20-tris(4-sulfonatophenyl)porphyrin macrocycles 58–61 act as switchable organocatalysts for Michael and aldol reactions in water [68][69]. The macrocycles 58–61 containing different chiral

• hypothesis that the reaction would work in acidic environment using catalysts insensitive to pH-induced aggregation. In the same aldol reaction, using of macrocycles 60 and 61 containing chiral secondary amine moieties provided not only good yields, but also good diastereoselectivities; chiral HPLC analysis

• organocatalysis can be summarized in the following statements: (1) using highly distorted nonplanar macrocyclic systems with an easy access to inner –NHs and basic imine moieties (by Senge, Hill, and co-workers [61][62][63]), (2) using monomeric and aggregated forms of achiral/chiral planar amphiphilic porphyrin

Enantioselective regiospecific addition of propargyltrichlorosilane to aldehydes catalyzed by biisoquinoline N,N’-dioxide

• Noble Brako,
• Sreerag Moorkkannur Narayanan,
• Amber Burns,
• Layla Auter,
• Valentino Cesiliano,
• Rajeev Prabhakar and
• Norito Takenaka

Beilstein J. Org. Chem. 2024, 20, 3069–3076, doi:10.3762/bjoc.20.255

• ; Introduction Enantioenriched α-allenic alcohols are an important class of chiral building blocks used for the chemical synthesis of biologically relevant molecules [1][2][3][4][5]. Their strength comes from the rich synthetic versatility [6][7][8][9] and biological relevance [10] of the allene functionality

• . Accordingly, the development of efficient access to optically active chiral α-allenic alcohols continues to be of significant interest in organic chemistry [11][12][13]. The asymmetric catalytic addition of allenylation reagents to aldehydes provides direct access to chiral α-allenic alcohols in an

• stable allenyltrichlorosilane that affords undesired homopropargylic alcohols [35][36] (Scheme 2b). Furthermore, Iseki [35] and Nakajima [36] evaluated only one chiral catalyst in their independent studies (i.e., no catalyst structure–reactivity and selectivity relationship study). In this context, we

Chemical structure metagenomics of microbial natural products: surveying nonribosomal peptides and beyond

• Thomas Ma and
• John Chu

Beilstein J. Org. Chem. 2024, 20, 3050–3060, doi:10.3762/bjoc.20.253

• ., the type of alkylmalonate it incorporates into a growing PK intermediate [61]. Furthermore, Xiang et al. reported recently that the stereochemistry of each new chiral center resulting from each alkylmalonate BB incorporation can be predicted based on the corresponding ketoreductase domain sequence [83

Cyclodextrin-based rotaxanes for polymer materials: challenge on simultaneous realization of inexpensive production and defined structures

• Yosuke Akae

Beilstein J. Org. Chem. 2024, 20, 3026–3049, doi:10.3762/bjoc.20.252

• from the chiral nature of the CD molecule, and its behavior fits well with the theoretical consideration. As comprehensively described [32], CD-based rotaxanes are typically synthesized by two methods: (1) the end-capping method (route a1, a2) in which the formation of a pseudorotaxane structure first

Advances in radical peroxidation with hydroperoxides

• Oleg V. Bityukov,
• Pavel Yu. Serdyuchenko,
• Andrey S. Kirillov,
• Gennady I. Nikishin,
• Vera A. Vil’ and
• Alexander O. Terent’ev

Beilstein J. Org. Chem. 2024, 20, 2959–3006, doi:10.3762/bjoc.20.249

• formation of peroxide 9. The enantioselective peroxidation of alkenes 10 with TBHP with the formation of the optically active products 11 was carried out in good yields and low ee by the use of in situ-generated chiral bisoxazoline–copper(I) complexes (Scheme 7) [43]. Studying the oxidation of α-pinene (12

• . The oxidation of benzyl alcohol 62 with TBHP results in aldehyde C, HAT from which by tert-butoxy radical A leads to the C-centered radical D. Subsequent recombination of radicals D and B provides the target product 63. An enantioselective peroxidation method of alkylaromatics with TBHP using chiral

4,6-Diaryl-5,5-difluoro-1,3-dioxanes as chiral dopants for liquid crystal compositions

• Maurice Médebielle,
• Peer Kirsch,
• Jérémy Merad,
• Carolina von Essen,
• Clemens Kühn and
• Andreas Ruhl

Beilstein J. Org. Chem. 2024, 20, 2940–2945, doi:10.3762/bjoc.20.246

• Darmstadt, Germany Institute of Materials Science, Technical University of Darmstadt, Peter-Grünberg-Str. 2, D-64287 Darmstadt, Germany 10.3762/bjoc.20.246 Abstract Two racemic anti-4,6-diphenyl-5,5-difluoro-1,3-dioxanes were prepared and the corresponding enantiomers were evaluated as potential new chiral

• dopants for liquid-crystal compositions. Keywords: chiral dopant; chirality; cholesteric phase; diols; fluorine; helical twisting power; liquid crystal; Introduction Liquid crystals for use in liquid crystal displays (LCDs) have become one of the most prominent application areas of fluoroorganic

• chemistry [1][2][3]. In particular, cholesteric, i.e., chiral nematic, liquid crystals (LCs) are attractive for many display applications due to their chiroptical characteristics as well as the selective reflection of light giving rise to Bragg interference colors [4]. Cholesteric LCs can be obtained either

Recent advances in transition-metal-free arylation reactions involving hypervalent iodine salts

• Ritu Mamgain,
• Kokila Sakthivel and
• Fateh V. Singh

Beilstein J. Org. Chem. 2024, 20, 2891–2920, doi:10.3762/bjoc.20.243

Access to optically active tetrafluoroethylenated amines based on [1,3]-proton shift reaction

• Yuta Kabumoto,
• Eiichiro Yoshimoto,
• Bing Xiaohuan,
• Masato Morita,
• Motohiro Yasui,
• Shigeyuki Yamada and
• Tsutomu Konno

Beilstein J. Org. Chem. 2024, 20, 2776–2783, doi:10.3762/bjoc.20.233

•  1a, 1, 2) [10][11][12], liquid crystals (Figure 1b, 3, 4) [13][14][15][16][17], fluorescence materials (Figure 1c, 5) [18][19], and so on, have been developed in recent years. In sharp contrast to the major development of such non-chiral tetrafluoroethylenated compounds, there have been only few

• reports on the preparation of chiral molecules possessing a tetrafluoroethylene unit on an asymmetric carbon center in a high optical purity, and to the best of our knowledge, only the following have been published so far (Scheme 1). As a highly enantioselective synthesis, there has been a pioneering work

• by Linclau et al. They have reported that the asymmetric Sharpless dihydroxylation of readily available (E)-5-bromo-4,4,5,5-tetrafluoro-2-penten-1-ol derivative 6 led to the corresponding chiral diols 7 with an excellent enantiomeric excess, 96% ee (reaction 1 in Scheme 1) [20][21]. It has also been

Copper-catalyzed yne-allylic substitutions: concept and recent developments

• Shuang Yang and
• Xinqiang Fang

Beilstein J. Org. Chem. 2024, 20, 2739–2775, doi:10.3762/bjoc.20.232

• 350100, China 10.3762/bjoc.20.232 Abstract The catalytic (asymmetric) allylation and propargylation have been established as powerful strategies allowing access to enantioenriched α-chiral alkenes and alkynes. In this context, combining allylic and propargylic substitutions offers new opportunities to

• ). Further control experiments and DFT calculations show that during the catalytic process, tertiary amine directly participates as a nucleophilic reagent to give the ammonium salt, which then releases dimethylaminium to provide the final product (Scheme 12). Chiral allylic sulfone compounds can be easily

• -, stereo-, and enantioselectivities, resulting in a series of chiral yne-allylic sulfone compounds with different substituents (Scheme 13, 14a–q). Due to the high steric hindrance of the γ-site, nucleophilic substitutions preferentially occur at the α-site. Through subsequent control experiments, they

5th International Symposium on Synthesis and Catalysis (ISySyCat2023)

• Anthony J. Burke and
• Elisabete P. Carreiro

Beilstein J. Org. Chem. 2024, 20, 2704–2707, doi:10.3762/bjoc.20.227

• easily recovered by precipitation using polar solvents. This catalyst proved to be excellent for the preparation of (S)-baclofen on a gram scale, furnishing the main chiral intermediate in high yield and enantioselectivity. Furthermore, the catalyst was recycled over five cycles while maintaining its

Computational design for enantioselective CO₂ capture: asymmetric frustrated Lewis pairs in epoxide transformations

• Maxime Ferrer,
• Iñigo Iribarren,
• Tim Renningholtz,
• Ibon Alkorta and
• Cristina Trujillo

Beilstein J. Org. Chem. 2024, 20, 2668–2681, doi:10.3762/bjoc.20.224

• into readily available substrates such as epoxides, resulting in the formation of polycarbonates or monomeric cyclic carbonates [22]. Depending on the substitution pattern in the epoxide, a chiral centre is present in the product. The insertion of CO2 into epoxides has been the subject of numerous

• an asymmetric FLP and consequently an asymmetric catalyst. The subsequent study explores the asymmetric insertion of CO2 into chiral PO catalysed by the proposed in silico designed catalyst. Computational Details During the benchmark to choose the best catalyst, the reported geometries were optimised

• results, we looked into the literature to explore examples of asymmetric FLPs. This exploration revealed three main types, namely, intramolecular chiral FLPs, intermolecular FLPs composed of a chiral acid and an achiral base, and intermolecular FLPs comprising an achiral acid and a chiral base [61][62

Applications of microscopy and small angle scattering techniques for the characterisation of supramolecular gels

• Connor R. M. MacDonald and
• Emily R. Draper

Beilstein J. Org. Chem. 2024, 20, 2608–2634, doi:10.3762/bjoc.20.220

A review of recent advances in electrochemical and photoelectrochemical late-stage functionalization classified by anodic oxidation, cathodic reduction, and paired electrolysis

• Nian Li,
• Ruzal Sitdikov,
• Ajit Prabhakar Kale,
• Joost Steverlynck,
• Bo Li and
• Magnus Rueping

Beilstein J. Org. Chem. 2024, 20, 2500–2566, doi:10.3762/bjoc.20.214

• product (Scheme 34). To date, only a few enantioselective reactions using metal catalysis and electrochemistry have been reported. Very recently, Ackermann and coworkers employed Co(OAc)2 as a catalyst and a salicyloxazoline derivative as a chiral ligand to achieve the electrochemical atroposelective C–H

• annulation of benzamides and allenes [47]. This method demonstrated excellent functional group tolerance, yielding a broad range of C–N axially chiral compounds with good yields and enantioselectivities. The practicality of this strategy was further demonstrated by a decagram-scale synthesis and the LSF of

• efficiently, enabling the LSF of benzodiazepine drugs such as diazepam, halazepam, and prazepam. Mechanistically, the Rh complex activates the C–H bond in phenylpyridine and assists in forming a bond with diphenylphosphine oxide, which, after anodic oxidation, yields the target product (Scheme 39). A chiral

Machine learning-guided strategies for reaction conditions design and optimization

• Lung-Yi Chen and
• Yi-Pei Li

Beilstein J. Org. Chem. 2024, 20, 2476–2492, doi:10.3762/bjoc.20.212

• are applicable to various substrates within the same reaction type [211][212][213][214][215]. For instance, the generality of chiral catalysts for asymmetric or enantioselective catalysis has been a longstanding interest in synthetic chemistry [216]. Angello et al. [53] applied uncertainty-minimizing

Synthesis and conformational analysis of pyran inter-halide analogues of ᴅ-talose

• Olivier Lessard,
• Mathilde Grosset-Magagne,
• Paul A. Johnson and
• Denis Giguère

Beilstein J. Org. Chem. 2024, 20, 2442–2454, doi:10.3762/bjoc.20.208

• chiral halides: F, Cl, Br, I) [19]. Only a handful of natural product syntheses have been reported [20][21], despite the promising biological activity of these unique inter-halides [22]. For our part, we recently reported the synthesis of contiguous inter-halide-bearing stereocenters using a Chiron

Facile preparation of fluorine-containing 2,3-epoxypropanoates and their epoxy ring-opening reactions with various nucleophiles

• Yutaro Miyashita,
• Sae Someya,
• Tomoko Kawasaki-Takasuka,
• Tomohiro Agou and
• Takashi Yamazaki

Beilstein J. Org. Chem. 2024, 20, 2421–2433, doi:10.3762/bjoc.20.206

• sequence from the corresponding chiral 4,4,4-trifluoro-3-hydroxybutyrate at low temperature [27][28][29][30], and 2) t-BuO2Li-mediated transformation of the enoates like 1g at −78 °C [31][32] and, to the best of our knowledge, no report has appeared on the convenient methods applicable to the larger scale

Evaluating the halogen bonding strength of a iodoloisoxazolium(III) salt

• Dominik L. Reinhard,
• Anna Schmidt,
• Marc Sons,
• Julian Wolf,
• Elric Engelage and
• Stefan M. Huber

Beilstein J. Org. Chem. 2024, 20, 2401–2407, doi:10.3762/bjoc.20.204

• iodoloisoxazolium for halogen-bonding activation and catalysis. Studies on the synthesis and application of chiral and/or bidentate dicationic derivatives are currently underway in our laboratory. Set of literature-known monocationic cyclic diaryliodonium(III) salts that were applied as XB donors (Z = OTf, BArF24

Asymmetric organocatalytic synthesis of chiral homoallylic amines

• Nikolay S. Kondratyev and
• Andrei V. Malkov

Beilstein J. Org. Chem. 2024, 20, 2349–2377, doi:10.3762/bjoc.20.201

• Nikolay S. Kondratyev Andrei V. Malkov Department of Chemistry, Loughborough University, Loughborough, LE11 3TU, UK Faculty of Science and Engineering, University of Wolverhampton, Wolverhampton, WV1 1LY, UK 10.3762/bjoc.20.201 Abstract In recent decades, the chiral allylation of imines emerged

• as a key methodology in the synthesis of alkaloids and natural products with 4-, 5- and 6-membered cyclic amine motifs. Initially reliant on stoichiometric reagents, synthetic chemists predominantly used N-substituted chiral imines, organometallic chiral reagents and achiral reagents with an

• equimolar chiral controller. However, recent years have witnessed the rise of asymmetric transition-metal catalysts and, importantly, organocatalytic allylation, reshaping the landscape of modern synthetic chemistry. This review explores the latest developments in the asymmetric allylation of imines

Stereoselective mechanochemical synthesis of thiomalonate Michael adducts via iminium catalysis by chiral primary amines

• Michał Błauciak,
• Dominika Andrzejczyk,
• Błażej Dziuk and
• Rafał Kowalczyk

Beilstein J. Org. Chem. 2024, 20, 2313–2322, doi:10.3762/bjoc.20.198

• significant advancement in mechanocatalysis. The stereoselective addition of bisthiomalonates 1–4 to cyclic enones and 4-chlorobenzylideneacetone proceeds stereoselectively under iminium activation conditions secured by chiral primary amines, in contrast to oxo-esters as observed in dibenzyl malonate addition

• hour compared to 24 or even 168 hours in solution-based reactions. It is noteworthy that this represents one of the early reports on the application of iminium catalysis using first-generation chiral amines under mechanochemical conditions, along with the utilization of easily enolizable thioesters as

• studies by Bolm [12][13], and Juaristi et al. [14]. have significantly advanced chiral secondary amine-catalyzed stereoselective reactions under ball milling conditions, representing a widely explored activation mode in mechanochemical-mediated transformations. However, reports on chiral primary iminium

Catalysing (organo-)catalysis: Trends in the application of machine learning to enantioselective organocatalysis

• Stefan P. Schmid,
• Leon Schlosser,
• Frank Glorius and
• Kjell Jorner

Beilstein J. Org. Chem. 2024, 20, 2280–2304, doi:10.3762/bjoc.20.196

• [96] investigated a bromocyclization catalysed by a chiral phosphoric acid (CPA) and a DABCOnium brominating reagent (Figure 6). The authors calculated transition state conformer ensembles for several flexible DABCOnium systems and performed energy decomposition analysis to separate the interactions

Natural resorcylic lactones derived from alternariol

• Joachim Podlech

Beilstein J. Org. Chem. 2024, 20, 2171–2207, doi:10.3762/bjoc.20.187

• structure of verrulactone A was later unambiguously confirmed by X-ray crystallographic analysis [160]. Chirality and absolute configurations remained unresolved, where it should be noted that even verrulactones A and B are axially chiral with an assumed significant racemization barrier. At least it has