Beyond symmetric self-assembly and effective molarity: unlocking functional enzyme mimics with robust organic cages

• Keith G. Andrews

Beilstein J. Org. Chem. 2025, 21, 421–443, doi:10.3762/bjoc.21.30

• constriction (ground-state destabilization) are also possible [140][168][169][170]. The metals can sometimes participate in redox catalysis [171], and may be stabilized by the cage structure [160][172][173][174]. The organic part of the MOC has also been levied as a hydrogen-bond donor to activate an

Quantifying the ability of the CF₂H group as a hydrogen bond donor

• Matthew E. Paolella,
• Daniel S. Honeycutt,
• Bradley M. Lipka,
• Jacob M. Goldberg and
• Fang Wang

Beilstein J. Org. Chem. 2025, 21, 189–199, doi:10.3762/bjoc.21.11

• group can act as a hydrogen bond donor, serving as a potential surrogate for OH or SH groups but with a weaker hydrogen bond donation ability. Here, we describe a series of CF2H group-containing moieties that facilitate hydrogen bond interactions. We survey hydrogen bond donation ability using several

• that, although the CF2H group mimics hydroxy or thiol groups, it is a generally less effective hydrogen bond donor. Given that the HB donation ability of a particular functional group usually increases with increasing Brønsted acidity [49] we chose to incorporate the CF2H group into the backbone of N

• method [19][20][47][48]. This convenient approach relies on comparing the 1H NMR chemical shift of a hydrogen bond donor in DMSO-d6 to that of it in CDCl3. The HB donor presumably interacts strongly with hydrogen-accepting DMSO [51], but barely with CDCl3, which has a weak hydrogen bond acceptance

Recent advances in organocatalytic atroposelective reactions

• Henrich Szabados and
• Radovan Šebesta

Beilstein J. Org. Chem. 2025, 21, 55–121, doi:10.3762/bjoc.21.6

• significantly high yields. The CPA organocatalyst activates quinones with an acceptor hydrogen bond while indole acts as hydrogen-bond donor. On the other hand, a hydroxy group of hydroxyindole becomes a hydrogen donor and the iminoquinone nitrogen represents an acceptor to the hydrogen from the CPA, resulting

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

• has become an essential structural motif in medicinal chemistry due to its hydrogen-bond donor capacity, its lipophilic character, and as a bioisostere for alcohol, thiol, or amine groups [16][17][18][19]. Thus, the contribution of fluorinated compounds to pharmaceuticals has been crucial for more

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

• concluded that both the presence of hydrogen-bond donor moieties (pyrrolic –NH groups) and a basic β-substituent are necessary to make the compound catalytically active. Further, authors have performed 1H NMR binding and kinetic studies and suggested that the reaction mechanism involves a simultaneous

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

• ] exploited the application of hydrogen-bond donor catalysis in asymmetric dearomative α-allylations of in situ-generated Ν-acylquinolinium salts 108 generated with 2,2,2-trichloroethyl chloroformate (TrocCl) (Scheme 22). Screening through a range of catalysts including the known squaramide and thiourea

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

• -type catalysts and more than one million double hydrogen bond donor catalysts. While this repository does not provide any reactivity data, it still comprises a valuable map of organocatalyst chemical space to aid in catalyst design. The creation of these larger datasets, both experimental and in silico

The Groebke–Blackburn–Bienaymé reaction in its maturity: innovation and improvements since its 21st birthday (2019–2023)

• Cristina Martini,
• Muhammad Idham Darussalam Mardjan and
• Andrea Basso

Beilstein J. Org. Chem. 2024, 20, 1839–1879, doi:10.3762/bjoc.20.162

• compounds. Dömling et al. [50] also reported the synthesis of N-edited guanine derivatives. Different drugs display the guanine motif, fundamental for its biological activity is a triad HBA–HBD–HBD (HBA = hydrogen bond acceptor, HBD = hydrogen bond donor) included in its structure. The authors propose a one

Bioinformatic prediction of the stereoselectivity of modular polyketide synthase: an update of the sequence motifs in ketoreductase domain

• Changjun Xiang,
• Shunyu Yao,
• Ruoyu Wang and
• Lihan Zhang

Beilstein J. Org. Chem. 2024, 20, 1476–1485, doi:10.3762/bjoc.20.131

• possessed Q at this residue. This substitution can be reasonable, as it serves as a hydrogen bond donor to activate the β-keto moiety of a substrate [31][32]. Additionally, the presence of K (4), which activates the catalytic tyrosine, was more conserved in C2-type KRs. In general, C2-KRs show similarity to

Switchable molecular tweezers: design and applications

• Pablo Msellem,
• Maksym Dekthiarenko,
• Nihal Hadj Seyd and
• Guillaume Vives

Beilstein J. Org. Chem. 2024, 20, 504–539, doi:10.3762/bjoc.20.45

• a parallel direction, as the bulky -OMe groups are located outside the tweezer’s cavity to avoid steric hindrance with each other. When protonated, the pyridinium group acts as a hydrogen-bond donor for the two methoxy groups and triggers the rotation of the respective benzene rings along with the

Green and sustainable approaches for the Friedel–Crafts reaction between aldehydes and indoles

• Periklis X. Kolagkis,
• Eirini M. Galathri and
• Christoforos G. Kokotos

Beilstein J. Org. Chem. 2024, 20, 379–426, doi:10.3762/bjoc.20.36

Mechanisms for radical reactions initiating from N-hydroxyphthalimide esters

• Carlos R. Azpilcueta-Nicolas and
• Jean-Philip Lumb

Beilstein J. Org. Chem. 2024, 20, 346–378, doi:10.3762/bjoc.20.35

• (Scheme 6A). Stern–Volmer analysis revealed that quenching of the photocatalyst’s excited state by the NHPI ester occurred only in presence of a hydrogen bond donor such as water (H2O) or methanol (MeOH). This supported the hypothesis that activation of NHPI esters towards photoinduced electron transfer

Using the phospha-Michael reaction for making phosphonium phenolate zwitterions

• Matthias R. Steiner,
• Max Schmallegger,
• Larissa Donner,
• Johann A. Hlina,
• Christoph Marschner,
• Judith Baumgartner and
• Christian Slugovc

Beilstein J. Org. Chem. 2024, 20, 41–51, doi:10.3762/bjoc.20.6

• primary adduct A (see Scheme 2) is too short-lived that an intramolecular hydrogen transfer toward 2a (C, in Scheme 2) is occurring [48]. Instead, in case of acrylonitrile another hydrogen bond donor, which is the solvent methanol [49], is necessary to trap intermediate A forming the ion pair D. Finally

• for the conversion of acrylamide, which is probably disturbed when the hydrogen bond donor solvent methanol is interacting with the amide group and/or the hydroxy group. Conclusion The conjugate addition of 2,4-di-tert-butyl-6-(diphenylphosphino)phenol to Michael acceptor molecules allows for a facile

Anion–π catalysis on carbon allotropes

• M. Ángeles Gutiérrez López,
• Mei-Ling Tan,
• Giacomo Renno,
• Augustina Jozeliūnaitė,
• J. Jonathan Nué-Martinez,
• Javier Lopez-Andarias,
• Naomi Sakai and
• Stefan Matile

Beilstein J. Org. Chem. 2023, 19, 1881–1894, doi:10.3762/bjoc.19.140

• control 12, a secondary Bingel amide in 13 caused a drop to A/D13/12 = 1.6. Similarly, low A/D14/12 = 1.5 for an ester in 14 supported that removal of the hydrogen-bond donor in 5 rather than steric constraints account for the decrease in anion–π catalysis. Elongation of the tether in the ester series 14

Trifluoromethylated hydrazones and acylhydrazones as potent nitrogen-containing fluorinated building blocks

• Zhang Dongxu

Beilstein J. Org. Chem. 2023, 19, 1741–1754, doi:10.3762/bjoc.19.127

• indispensable role in drug discovery and design since the hydrogen atom can act as lipophilic hydrogen-bond donor and act as a bioisostere for the alcohol moiety [81][82][83]. Thus, many effective difluoromethylation strategies have been developed in recent years. Difluoroacetohydrazonoyl bromides were chosen

Clauson–Kaas pyrrole synthesis using diverse catalysts: a transition from conventional to greener approach

• Dileep Kumar Singh and
• Rajesh Kumar

Beilstein J. Org. Chem. 2023, 19, 928–955, doi:10.3762/bjoc.19.71

• bond donating groups were investigated. Among these, the DES prepared by mixing quaternary ammonium salts choline chloride (ChCl) and the hydrogen-bond donor L-(+)-tartaric acid gives the best result. Moreover, L-(+)-tartaric acid–ChCl acts as both solvent and catalyst for pyrrole synthesis. This

Mechanochemical solid state synthesis of copper(I)/NHC complexes with K₃PO₄

• Ina Remy-Speckmann,
• Birte M. Zimmermann,
• Mahadeb Gorai,
• Martin Lerch and
• Johannes F. Teichert

Beilstein J. Org. Chem. 2023, 19, 440–447, doi:10.3762/bjoc.19.34

• inactive complexes (see Supporting Information File 1 for details). This also supports the notion that during catalytic ester hydrogenation, the guanidinium moiety acts as a hydrogen bond donor to the esters [48]. The formation of a CO2 adduct hinders the ability to form hydrogen bonds. Furthermore

Catalytic aza-Nazarov cyclization reactions to access α-methylene-γ-lactam heterocycles

• Bilge Banu Yagci,
• Selin Ezgi Donmez,
• Onur Şahin and
• Yunus Emre Türkmen

Beilstein J. Org. Chem. 2023, 19, 66–77, doi:10.3762/bjoc.19.6

• ). Finally, we investigated the activity of the achiral thiophosphoric triamide 13 as a triple hydrogen-bond donor [67]. With the use of 1.2 equiv of 13 at 23 °C, product 7b was isolated in 25% yield (Table 1, entry 16). Overall, while AgOTf still appeared to be the best reagent to be used in catalytic

Total synthesis of grayanane natural products

• Nicolas Fay,
• Rémi Blieck,
• Cyrille Kouklovsky and
• Aurélien de la Torre

Beilstein J. Org. Chem. 2022, 18, 1707–1719, doi:10.3762/bjoc.18.181

• optimization showed that chiral squaramide 47 developed by Jacobsen’s group significantly accelerated the Mukaiyama reaction compared to TMSOTf or TiCl4 thanks to chiral hydrogen bond-donor effect [35]. After Sakurai cyclization promoted by EtAlCl2, the desired product 48 was obtained with the required

Redox-active molecules as organocatalysts for selective oxidative transformations – an unperceived organocatalysis field

• Elena R. Lopat’eva,
• Igor B. Krylov,
• Dmitry A. Lapshin and
• Alexander O. Terent’ev

Beilstein J. Org. Chem. 2022, 18, 1672–1695, doi:10.3762/bjoc.18.179

• oxaziridinium organocatalysis was developed recently [138]. The advantage of this method is the compatibility with secondary alcohol groups, which are not oxidized and can be used as a directing moiety. The use of HFIP as a strong hydrogen bond donor solvent protecting alcohols from oxidation was considered as

N-Sulfinylpyrrolidine-containing ureas and thioureas as bifunctional organocatalysts

• Viera Poláčková,
• Dominika Krištofíková,
• Boglárka Némethová,
• Renata Górová,
• Mária Mečiarová and
• Radovan Šebesta

Beilstein J. Org. Chem. 2021, 17, 2629–2641, doi:10.3762/bjoc.17.176

• itself, in which the carboxylic function acts as an ancillary hydrogen-bond donor for the direction of one of the reagents [9]. Amines serve as basic units and nucleophilic components capable of carbonyl compounds activation via enamine or iminium ion formation [10][11]. In particular, pyrrolidine became

Halides as versatile anions in asymmetric anion-binding organocatalysis

• Lukas Schifferer,
• Martin Stinglhamer,
• Kirandeep Kaur and
• Olga García Macheño

Beilstein J. Org. Chem. 2021, 17, 2270–2286, doi:10.3762/bjoc.17.145

• studies revolved around hydrogen bond donor catalysts and their application in N-acyliminium ion reactions. At this point, the mechanistic proposal, albeit speculative, was based on the hypothesis that neutral chloroamide structures I were the reactive intermediates in the reaction. Under this premise, H

• complex or active nucleophiles. In 2014, Jacobsen et al. developed a highly enantioselective selenocyclization reaction of olefins 26, using the chiral squaramide 28 as a dual hydrogen bond donor (Scheme 6) [16]. Although early-stage enantio-enrichment during the introduction of selenium is hard to

• typical limiting factors of hydrogen bond donor catalysis, ranging from high catalyst loadings to high dilution, long reaction times and, in some cases, insufficient chirality transfer into the products. As a consequence, many efforts have been spent to overcome those limitations. Some of them rely on the

Thermodynamic and electrochemical study of tailor-made crown ethers for redox-switchable (pseudo)rotaxanes

• Henrik Hupatz,
• Marius Gaedke,
• Hendrik V. Schröder,
• Julia Beerhues,
• Arto Valkonen,
• Fabian Klautzsch,
• Sebastian Müller,
• Felix Witte,
• Kari Rissanen,
• Biprajit Sarkar and
• Christoph A. Schalley

Beilstein J. Org. Chem. 2020, 16, 2576–2588, doi:10.3762/bjoc.16.209

• form presumably a non-threaded complex with the reduced NDI crown ethers, where the charged ions are in closer proximity than in the pseudo[2]rotaxane. This assumption was further confirmed by the addition of the hydrogen bond donor (CH3)2NH2PF6 to a solution of the wheel NDIC8, which again leads to

Design, synthesis and application of carbazole macrocycles in anion sensors

• Alo Rüütel,
• Ville Yrjänä,
• Sandip A. Kadam,
• Indrek Saar,
• Mihkel Ilisson,
• Astrid Darnell,
• Kristjan Haav,
• Tõiv Haljasorg,
• Lauri Toom,
• Johan Bobacka and
• Ivo Leito

Beilstein J. Org. Chem. 2020, 16, 1901–1914, doi:10.3762/bjoc.16.157

• moiety fulfils several key design requirements. At least four hydrogen bonding sites (N–H groups) are available and positioned in a favourable geometry for carboxylates. Additional hydrogen-bond-donor (HBD) groups can be added with substituents. The solubility of such receptors can be tuned using

• out of the macrocycle plane. It was expected that these macrocycles will have lower affinity constants. MC002 was of sufficient size to accommodate smaller carboxylate ions. However, in the most stable computed structures the hydrogen-bond donor NH fragments directed towards the outside of the ring

1,2,3-Triazolium macrocycles in supramolecular chemistry

• Mastaneh Safarnejad Shad,
• Pulikkal Veettil Santhini and
• Wim Dehaen

Beilstein J. Org. Chem. 2019, 15, 2142–2155, doi:10.3762/bjoc.15.211

• selectivity of this receptor for chloride anion is due to the cavity size (see Figure 3) [37]. 2.2. Optical anion sensing by 1,2,3-triazolium macrocycles within porphyrin cages Various porphyrin-based host supramolecules containing hydrogen-bond donor groups such as integrated amide, urea, pyrrole, ammonium

• donors: The benefits of combining the triazolium motif with other hydrogen bond donor motifs has been explored by Sessler et al. and they have synthesized a pyrrole based tetra-1,2,3-triazolium macrocycle 10 (Figure 10) via the tetraalkylation of a triazole macrocycle originally prepared via click

• interactions in polar solvents. An important implication for receptor design has been revealed by combining various hydrogen bond donor motifs, particularly systems designed to recognize anions in highly polar organic media or aqueous environments by considering of different solvent dependence of the