Regio- and stereochemical stability induced by anomeric and gauche effects in difluorinated pyrrolidines

• Ana Flávia Candida Silva,
• Francisco A. Martins and
• Matheus P. Freitas

Beilstein J. Org. Chem. 2024, 20, 1572–1579, doi:10.3762/bjoc.20.140

• stereochemical behavior. Consequently, various molecular properties, such as polarity, viscosity, and intra- and intermolecular interactions, are impacted by the C‒F bond. These features underlie the important role of selective fluorination in pharmaceuticals and agrochemicals development [1]. For instance

Benzylic C(sp³)–H fluorination

• Alexander P. Atkins,
• Alice C. Dean and
• Alastair J. J. Lennox

Beilstein J. Org. Chem. 2024, 20, 1527–1547, doi:10.3762/bjoc.20.137

• preliminary electrochemical examples [93][101]. Middleton and co-workers described an alternating polarity approach for the fluorination of simple toluene derivatives in neat pyridine·HF (Figure 42) [102][103]. Poor conductivity necessitated the use of this waveform type. The benzylic fluorination was

Photoswitchable glycoligands targeting Pseudomonas aeruginosa LecA

• Yu Fan,
• Ahmed El Rhaz,
• Stéphane Maisonneuve,
• Emilie Gillon,
• Maha Fatthalla,
• Franck Le Bideau,
• Guillaume Laurent,
• Samir Messaoudi,
• Anne Imberty and
• Juan Xie

Beilstein J. Org. Chem. 2024, 20, 1486–1496, doi:10.3762/bjoc.20.132

• reversible light modulation of their activity since each isomer shows distinct structural and electronic properties [13]. Photoisomerization-induced conformational and polarity changes may allow to increase or decrease the interaction with the target protein or receptors, then modulate the drug potency on

Novel route to enhance the thermo-optical performance of bicyclic diene photoswitches for solar thermal batteries

• Akanksha Ashok Sangolkar,
• Rama Krishna Kadiyam and
• Ravinder Pawar

Beilstein J. Org. Chem. 2024, 20, 1053–1068, doi:10.3762/bjoc.20.93

• ) type-I is generated by increasing the unsaturated bridge length of the NBD/QC pair thus having a short saturated bridge, and (b) type-II designed by elongating the unsaturated bridge of the BOD/TCO pair thus have elongated saturated bridge, too. Further, the effect of the presence of different polarity

• solvation Knowledge of the best suitable environmental conditions for the photoswitching system is essential to achieve high performance in the real-life MOST devices. Therefore, attention has also been devoted to envisage the impact of different polarity solvents on the properties of the BBD-based

• photoswitching couples. Herein, the influence of solvation has been measured only for type-Ia, Ic, IIa, and IIc photoswitching couples. Initially, the geometries of the bicyclic dienes and photoproducts of the studied photoswitches were optimized in the presence of different polarity solvents at the M062X/6-311

Structure–property relationships in dicyanopyrazinoquinoxalines and their hydrogen-bonding-capable dihydropyrazinoquinoxalinedione derivatives

• Tural N. Akhmedov,
• Ajeet Kumar,
• Daken J. Starkenburg,
• Kyle J. Chesney,
• Khalil A. Abboud,
• Novruz G. Akhmedov,
• Jiangeng Xue and
• Ronald K. Castellano

Beilstein J. Org. Chem. 2024, 20, 1037–1052, doi:10.3762/bjoc.20.92

• (7c) in moderate yield. The condensation of 7c with 13 in the presence of 1,4-dioxane yielded poorly soluble 10. Unfortunately, several oxidation attempts to access target 7a failed presumably due to the insolubility of 10 even in high polarity solvents, listed in Table S3 (Supporting Information File

• and aromatic groups as strong donors in the backbone; the dione groups in the case of DPQDs diminish the acceptor properties of the aza π-system. It is worth mentioning that ICT is significantly influenced by solvent polarity and the comprehensive study of solvent effects is not within the scope of

(Bio)isosteres of ortho- and meta-substituted benzenes

• H. Erik Diepers and
• Johannes C. L. Walker

Beilstein J. Org. Chem. 2024, 20, 859–890, doi:10.3762/bjoc.20.78

• early drug discovery process. In many cases, the primary aim is the enhancement of biological activity, but in others, modulation of other critical properties such as aqueous solubility, metabolic stability, polarity, or lipophilicity is the target. In the latter cases, there is often a desire to retain

• activity, if not an improvement [1]. Often-used bioisosteres include the tetrazole group for a carboxylic acid [2][3][4][5] and fluorine atoms in place of hydrogens [6][7]. The inclusion of fluorine can alter the polarity of a molecule and can also be used to prevent epimerisation, as seen in

• partition coefficient (logP) as a measure of compound polarity, aqueous solubility (desired value: >200 μM [26]), and intrinsic clearance rate (CLint, lower indicates higher metabolic stability) as a measure of metabolic stability. Additional properties will be discussed if comparative values have been

Possible bi-stable structures of pyrenebutanoic acid-linked protein molecules adsorbed on graphene: theoretical study

• Yasuhiro Oishi,
• Motoharu Kitatani and
• Koichi Kusakabe

Beilstein J. Org. Chem. 2024, 20, 570–577, doi:10.3762/bjoc.20.49

• important. A selective hydration of the polar moiety while keeping the pyrene moiety stable can relatively strengthen the stability of conformation 2. Thus, as the polarity of the solvent increases, the probability of conformation 2 appearance is expected to increase. Mechanism of bi-stability in PASE on

• II. Thus, as the polarity of the solvent increases, the probability of the appearance of conformation II is expected to increase. Then, conditions of the temperature and the external pressure of gases have to be chosen properly, too. We need to keep the pyrene part stable in the whole procedures

• collected in a captured state in a solvent. The specimen is introduced onto a graphene substrate linked with a protein prepared as a sensor. Therefore, the rotational motion at the linker portion should be more active in a solution consisting of a solvent having higher polarity, and this will lead to an

Ligand effects, solvent cooperation, and large kinetic solvent deuterium isotope effects in gold(I)-catalyzed intramolecular alkene hydroamination

• Ruichen Lan,
• Brock Yager,
• Yoonsun Jee,
• Cynthia S. Day and
• Amanda C. Jones

Beilstein J. Org. Chem. 2024, 20, 479–496, doi:10.3762/bjoc.20.43

• (first order fit in alkene decay) between THF (ε = 7.6, polarity index = 4.0), methylene chloride (ε = 8.9, polarity index = 3.1), and methanol (ε = 32.7, polarity index = 5.1) despite the large differences in solvent polarity (Table 2, entries 3, 4, and 5; rates in THF and MeOH are only 1–2 times faster

• effect of MeOH co-solvent on the 1a → 3a transformation was due to its role as a hydrogen bonding donor (proton source), or due to its role as a hydrogen bonding acceptor (Lewis base) [44]. To this end, we examined the impact of different alcohols (varied acidity and polarity) and different non-protic

Pseudallenes A and B, new sulfur-containing ovalicin sesquiterpenoid derivatives with antimicrobial activity from the deep-sea cold seep sediment-derived fungus Pseudallescheria boydii CS-793

• Zhen Ying,
• Xiao-Ming Li,
• Sui-Qun Yang,
• Hong-Lei Li,
• Xin Li,
• Bin-Gui Wang and
• Ling-Hong Meng

Beilstein J. Org. Chem. 2024, 20, 470–478, doi:10.3762/bjoc.20.42

• concentrated under reduced pressure to give 123.6 g of an organic extract. The EtOAc extract was subjected to Si gel VLC (vacuum liquid chromatography) and fractionated using solvent mixtures of increasing polarity consisting of petroleum ether (PE) and EtOAc 20:1 to 1:1 and finally with CH2Cl2/MeOH 20:1 to 1

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

• reduction in the concentration of these cytokines, as well as, increased intestinal permeability and improved expression of tight junction proteins that control the polarity of cells when using DIM in Caco-2 human cells [3]. BIMs have also been linked with the therapy of various cancers with one of their

Photochromic derivatives of indigo: historical overview of development, challenges and applications

• Gökhan Kaplan,
• Zeynel Seferoğlu and
• Daria V. Berdnikova

Beilstein J. Org. Chem. 2024, 20, 228–242, doi:10.3762/bjoc.20.23

• + cations (500 equiv). At the same time, addition of TBA+ cations showed just a minimal impact on the stability of the Z-form comparable with the effect of counter anions and solvent polarity. In 2021, Tsubaki and co-workers synthesized bridged N,N′-dialkyl-substituted indigos 13 and studied their thermal

• the Z-isomers in comparison with the E-forms [62]. In 2018, Nagasawa and co-workers provided a detailed investigation of the influence of solvent polarity and intermolecular hydrogen bonding on the photoisomerization of N,N'-diacetylindigo (9a) by transient absorption spectroscopy [63]. In principle

• electron donors on the isomerization yields was negligible because of the Boc groups. A few years later, Koeppe and Schröder prepared several N,N'-di(Boc)indigo derivatives 17a–h in order to study the effect of substituents on photoisomerization in solvents of different polarity [53]. It was found that

Perspectives on push–pull chromophores derived from click-type [2 + 2] cycloaddition–retroelectrocyclization reactions of electron-rich alkynes and electron-deficient alkenes

• Michio Yamada

Beilstein J. Org. Chem. 2024, 20, 125–154, doi:10.3762/bjoc.20.13

• yield for the ring-formation process was modest at 5% (see Scheme 16) [121][122]. The macrocycle in 46 was observed to engage with the peptide segment in low-polarity solvents. In contrast, 1H NMR analysis suggested that the macrocycle disengaged from the peptide segment and relocated along the alkyl

• toluene. This phenomenon aligns with the notion that the TICT states experience stabilization with increasing solvent polarity. Conversely, in contrast to 68–70, and 71, a TCBD derivative 72 incorporating a tetraphenylethylene (TPE) moiety exhibited no emission in toluene, possibly due to the presence of

• shoulder emission at 612 nm. When the solvent was changed from toluene to benzonitrile and the polarity of the solvent increased, the emission at 612 nm remained almost unchanged, while the emission at 675 nm significantly quenched with a red shift of 35 nm. In the transient absorption spectra of 60 in

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

• Michael adduct of acrylamide, and 2h, the Michael adduct of 2-hydroxyethyl acrylate, show blue-shifted absorption maxima of 352 nm and 356 nm, respectively. Upon increasing the solvent polarity by using methanol instead of chloroform, a hypsochromic shift of the absorption maximum occurs (dotted lines in

1-Butyl-3-methylimidazolium tetrafluoroborate as suitable solvent for BF₃: the case of alkyne hydration. Chemistry vs electrochemistry

• Marta David,
• Elisa Galli,
• Richard C. D. Brown,
• Marta Feroci,
• Fabrizio Vetica and
• Martina Bortolami

Beilstein J. Org. Chem. 2023, 19, 1966–1981, doi:10.3762/bjoc.19.147

• pollutants. This also facilitates their recovery and recycling. Furthermore, they generally exhibit low flammability, high thermal and chemical stability, good thermal and electrical conductivity, together with the ability to solubilize organic and inorganic compounds of different polarity [78][79][80][81

Studying specificity in protein–glycosaminoglycan recognition with umbrella sampling

• Mateusz Marcisz,
• Sebastian Anila,
• Margrethe Gaardløs,
• Martin Zacharias and
• Sergey A. Samsonov

Beilstein J. Org. Chem. 2023, 19, 1933–1946, doi:10.3762/bjoc.19.144

• multipose character of GAG binding and the polarity of the binding poses of these periodic molecules. In the present work, all-atom MD simulations are conducted to study the dynamics of the protein–GAG complexes, and are complemented by free energy analysis. The free energy analysis of the protein–GAG

A novel recyclable organocatalyst for the gram-scale enantioselective synthesis of (S)-baclofen

• Gyula Dargó,
• Dóra Erdélyi,
• Balázs Molnár,
• Péter Kisszékelyi,
• Zsófia Garádi and
• József Kupai

Beilstein J. Org. Chem. 2023, 19, 1811–1824, doi:10.3762/bjoc.19.133

• homogeneous reaction. For example, by incorporating a lipophilic side chain [28] on the organocatalyst that does not interfere with its catalytic activity thanks to a linker between the catalyst and lipophilic units. In this way, a significant difference in polarity can be achieved between the catalyst and

• carry out the catalytic reaction homogeneously. The solubility of the lipophilic catalyst 2 was investigated in ten solvents with low polarity, including a new, bio-based polar aprotic solvent, MeSesamol [33]. The catalyst’s precipitation – which is necessary for its recycling – was tested by adding a

A deep-red fluorophore based on naphthothiadiazole as emitter with hybridized local and charge transfer and ambipolar transporting properties for electroluminescent devices

• Suangsiri Arunlimsawat,
• Patteera Funchien,
• Pongsakorn Chasing,
• Atthapon Saenubol,
• Taweesak Sudyoadsuk and
• Vinich Promarak

Beilstein J. Org. Chem. 2023, 19, 1664–1676, doi:10.3762/bjoc.19.122

• , the molecule contains both the intrinsic LE and CT excited states or demonstrates HLCT characteristics. Besides, the Stokes shifts between absorption and emission spectra were plotted as a function of solvent polarity function (Δf) corresponding to the Lipper–Mataga model which defines the

• interactions between the solvent and dipole moment of the chromophore (Figure 3b). The Lippert–Mataga plot showed two linear slopes indicating the presence of two different excited states in the molecule. In the high-polarity region, the excited-state dipole moment (μe) was 19.04 D, which was close to that of

• a typical CT molecule 4-(N,N-dimethylamino)benzonitrile (μe = 23 D) [55], suggesting a CT state-dominated character in high-polarity solvents. Besides, in the low-polarity region, the μe value was 5.49 D, which is slightly higher than the ground-state dipole moment (μg = 1.30 D) estimated using

Morpholine-mediated defluorinative cycloaddition of gem-difluoroalkenes and organic azides

• Tzu-Yu Huang,
• Mario Djugovski,
• Sweta Adhikari,
• Destinee L. Manning and
• Sudeshna Roy

Beilstein J. Org. Chem. 2023, 19, 1545–1554, doi:10.3762/bjoc.19.111

• process involves an attack of the organic azide nucleophile to the β-position of α-fluoronitroalkenes. The polarity of gem-difluoroalkenes is reversed in comparison to α-fluoronitroalkenes since the nucleophile attacks at the α-position of the gem-difluoroalkenes. A cycloaddition reaction between organic

Complexes of resorcin[4]arene with secondary amines: synthesis, solvent influence on “in-out” structure, and theoretical calculations of non-covalent interactions

• Waldemar Iwanek

Beilstein J. Org. Chem. 2023, 19, 1525–1536, doi:10.3762/bjoc.19.109

• amine, and the type of complex formed is influenced by the nature and polarity of the solvent. The stoichiometry and solvent-dependent structure of the “in-out” complexes formed were determined through NMR spectroscopy. Screening tests were carried out using the aISS-xTB2 method, while the final

• -methylpiperazine), the complexes with 1:1 stoichiometry were formed. For sec-amines with larger alkyl substituents (dipropylamine, diisopropylamine), complexes with 1:2 stoichiometry were formed. The structure of the complexes with 1:1 stoichiometry varies depending on the type and polarity of the solvent. In DMSO

Organic thermally activated delayed fluorescence material with strained benzoguanidine donor

• Alexander C. Brannan,
• Elvie F. P. Beaumont,
• Nguyen Le Phuoc,
• George F. S. Whitehead,
• Mikko Linnolahti and
• Alexander S. Romanov

Beilstein J. Org. Chem. 2023, 19, 1289–1298, doi:10.3762/bjoc.19.95

• experience a very weak solvatochromic effect with increasing solvent polarity from cyclohexane to dichloromethane. This indicates only minor change of the dipole moment upon vertical excitation from S0 (6.4 D) to S1 (7.2 D) excited states according to the TD-DFT theoretical calculations (Table S2, Supporting

Enabling artificial photosynthesis systems with molecular recycling: A review of photo- and electrochemical methods for regenerating organic sacrificial electron donors

• Grace A. Lowe

Beilstein J. Org. Chem. 2023, 19, 1198–1215, doi:10.3762/bjoc.19.88

• solvent polarity [24][25]. Hence, it is important when considering new reagents and catalysts to only compare potentials measured in conditions as close to the photocatalytic conditions as possible. For instance, quinones have 2 one-electron reductions in aprotic media and one two-electron reduction at a

Exploring the role of halogen bonding in iodonium ylides: insights into unexpected reactivity and reaction control

• Carlee A. Montgomery and
• Graham K. Murphy

Beilstein J. Org. Chem. 2023, 19, 1171–1190, doi:10.3762/bjoc.19.86

• negative electrostatic potential (VS,min) of the acceptor [46][48][51][52], but also by other factors [53][54][55][56][57] including hydrogen bonding [31][48], solvent polarity [47][58], the Lewis basicity of the acceptor [46][50] and by sterics [46]. As with any interatomic interaction, the energy of a

Photoredox catalysis harvesting multiple photon or electrochemical energies

• Mattia Lepori,
• Simon Schmid and
• Joshua P. Barham

Beilstein J. Org. Chem. 2023, 19, 1055–1145, doi:10.3762/bjoc.19.81

• standardization but also thanks to developments in technology (flow, alternating polarity) and understanding that fundamentally improve selectivity. Among these is its innovative merger with PRC (synthetic PEC) in a fashion that tackles the issues of both parent techniques and has risen to the forefront of

The effect of dark states on the intersystem crossing and thermally activated delayed fluorescence of naphthalimide-phenothiazine dyads

• Liyuan Cao,
• Xi Liu,
• Xue Zhang,
• Jianzhang Zhao,
• Fabiao Yu and
• Yan Wan

Beilstein J. Org. Chem. 2023, 19, 1028–1046, doi:10.3762/bjoc.19.79

• strongly quenched and red-shifted in polar solvents, as compared to that in CHX and HEX. The higher polarity solvents can stabilize the CS state, and the energy of CS state will decrease. As a result, the emission band will be red-shifted and the fluorescence intensity will be greatly reduced. The results

• that affects the fluorescence of these two dyads. Indeed, the highly solvent polarity dependent fluorescence emission intensity, and wavelength are different from the 4-amino NI derivatives, which are much less solvent polarity-dependent [59][61]. Since a TADF molecule is characterized by a stronger

• solvents with varying polarity (Table 2). For the dyads containing unoxidized PTZ, the ΦΔ is less than 20% in non-polar solvents, and ΦΔ becomes negligible in polar solvents. It should be noted that given the lowest transient species was not a 3LE state, instead a CS state, no formation of 1O2 should be

CO₂ complexation with cyclodextrins

• Cecilie Høgfeldt Jessen,
• Jesper Bendix,
• Theis Brock Nannestad,
• Heloisa Bordallo,
• Martin Jæger Pedersen,
• Christian Marcus Pedersen and
• Mikael Bols

Beilstein J. Org. Chem. 2023, 19, 1021–1027, doi:10.3762/bjoc.19.78

• were the following: β- (2) and γ-cyclodextrins (3) were also studied by Cramer, but gave no crystals although they might still bind CO2. Compound 4 (permethylated α-cyclodextrin) [16] is in terms of hydrogen bonding properties and polarity vastly different from 1 yet still water-soluble. Compounds 5