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

• generalizing the elucidated reaction mechanism to other [2 + 2] CA–RE reactions involving TCNE and TCNQ as electrophiles might be difficult. They emphasized the significance of considering a pre-equilibrium state of the charge-transfer complexes between the alkynes and alkenes and mentioned that the

Synthetic approach to 2-alkyl-4-quinolones and 2-alkyl-4-quinolone-3-carboxamides based on common β-keto amide precursors

• Yordanka Mollova-Sapundzhieva,
• Plamen Angelov,
• Danail Georgiev and
• Pavel Yanev

Beilstein J. Org. Chem. 2023, 19, 1804–1810, doi:10.3762/bjoc.19.132

• /E isomers in approximately 85:15 ratio. The same spectra in CDCl3 showed broad coalescent signals for the characteristic vinyl CH protons, which is indicative of a dynamic equilibrium between the isomers. For both types of nitro intermediates 3 and 6 the final ring-forming step required reduction of

Unprecedented synthesis of a 14-membered hexaazamacrocycle

• Anastasia A. Fesenko and
• Anatoly D. Shutalev

Beilstein J. Org. Chem. 2023, 19, 1728–1740, doi:10.3762/bjoc.19.126

• were extremely broadened. This can be explained by some equilibrium processes including internal rotation of the acetylamino group and/or exchange between C=N bond configurations. As the temperature increases, the width of the signals decreases, however, even at 100 °С, some signals remain broadened

Benzoimidazolium-derived dimeric and hydride n-dopants for organic electron-transport materials: impact of substitution on structures, electrochemistry, and reactivity

• Swagat K. Mohapatra,
• Khaled Al Kurdi,
• Samik Jhulki,
• Georgii Bogdanov,
• John Bacsa,
• Maxwell Conte,
• Tatiana V. Timofeeva,
• Seth R. Marder and
• Stephen Barlow

Beilstein J. Org. Chem. 2023, 19, 1651–1663, doi:10.3762/bjoc.19.121

• , whereby the dimer is in equilibrium with a small concentration of the corresponding odd-electron monomer, which can then rapidly react with an acceptor such as an organic semiconductor (SC) through an exergonic electron transfer (ET), has been observed for the reactions of several relatively weakly bonded

Radical chemistry in polymer science: an overview and recent advances

• Zixiao Wang,
• Feichen Cui,
• Yang Sui and
• Jiajun Yan

Beilstein J. Org. Chem. 2023, 19, 1580–1603, doi:10.3762/bjoc.19.116

• ATRP relies on the establishment of a reversible activation/deactivation equilibrium reaction between an alkyl halide or halide-like initiator (RX) and a radical species (R·) [43]. During the activation process, the organohalides quickly lose their terminal halogen atoms in the presence of the liganded

• amino acid sequence of mfp-1, mfp-3, and mfp-5 (Y: DOPA, K: lysine). B) Scheme showing examples of the adhesive and cohesive properties of catechol-containing proteins. R represents the remainder of the mfp’s. Scheme 3 redrawn from [10]. Activation–deactivation equilibrium in nitroxide-mediated

Cyclodextrins permeabilize DPPC liposome membranes: a focus on cholesterol content, cyclodextrin type, and concentration

• Ghenwa Nasr,
• Hélène Greige-Gerges,
• Sophie Fourmentin,
• Abdelhamid Elaissari and
• Nathalie Khreich

Beilstein J. Org. Chem. 2023, 19, 1570–1579, doi:10.3762/bjoc.19.115

• Information File 1). The instantaneous effect of CDs on other membranes was similarly obtained. This may be due to the rapid equilibrium that could be established at 10% CHOL between the membrane and the CD. In fact, CD can instantly interact with the liposome membrane constituents and the extraction of lipid

• -organized and the equilibrium between the CD and the membrane is established. Our result for 10% CHOL liposomes is in accordance with that of Hatzi et al. showing an instant calcein release from CHOL-free liposomes (PC and H-PC vesicles) exposed to CDs with no further leakage with time [12]. It is worthy to

• note, that the 10% CHOL membranes are less stable than the remaining formulations and evidenced the same SRB release pattern as CHOL-free liposomes [15]. Nonetheless, the rapid equilibrium between the CDs and the membrane cannot alone explain the reason behind the disappearance of the CDs effect with

Unraveling the role of prenyl side-chain interactions in stabilizing the secondary carbocation in the biosynthesis of variexenol B

• Moe Nakano,
• Rintaro Gemma and
• Hajime Sato

Beilstein J. Org. Chem. 2023, 19, 1503–1510, doi:10.3762/bjoc.19.107

• as the C–H–π interaction between the carbocation intermediate and the Phe residue of terpene cyclase in the biosynthesis of sesterfisherol [21], and the intricated rearrangement reaction mechanism promoted by the equilibrium state of the homoallyl cation and the cyclopropylcarbinyl cation in the

Application of N-heterocyclic carbene–Cu(I) complexes as catalysts in organic synthesis: a review

• Nosheen Beig,
• Varsha Goyal and
• Raj K. Bansal

Beilstein J. Org. Chem. 2023, 19, 1408–1442, doi:10.3762/bjoc.19.102

• the nitrogen atoms adjacent to the carbene center result in kinetic stabilization of the NHC suppressing its dimerization to the corresponding olefin (the Wanzlick equilibrium). On the other hand, thermodynamic stabilization results due to donation of lone pair(s) electrons of the adjacent nitrogen

Metal catalyst-free N-allylation/alkylation of imidazole and benzimidazole with Morita–Baylis–Hillman (MBH) alcohols and acetates

• Olfa Mhasni,
• Jalloul Bouajila and
• Farhat Rezgui

Beilstein J. Org. Chem. 2023, 19, 1251–1258, doi:10.3762/bjoc.19.93

• removal of water formed from the direct amination of alcohol 4a by azeotropic distillation shifted the position of the equilibrium in direction to the formation of the allylated imidazole 6a which was obtained in good 88% yield (Table 1, entry 6). The protocol was also successfully extended to the

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

• these ylides (e.g., 75), they surmised that the nitro group was best suited to blocking the proximal σ-hole, thereby preventing non-productive reaction pathways (e.g., thioamide arylation) from occurring. Takemoto and Kobayashi have theorized that an equilibrium should exist between Lewis-basic

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

• unlikely to be detected in ns-TA spectra due to its transient character (the lifetime of this state is short, its concentration is too low to be detected by ns-TA spectroscopy) [67][68]. The monoexponential decay kinetics indicate that the 3LE and 3CS state are in good equilibrium, i.e., the spin–vibronic

• native PTZ moiety, the T1 state density is delocalized on the NI and PTZ moieties. Since these two moieties have different T1 state energies (2.25 and 2.45 eV, respectively), the T1 state should be a 3CS state, not an equilibrium of 3PTZ/3NI state. In polar solvents (e.g., ACN), literally the same

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

• Table 1. As CO2 is in large excess high crystal yields can be obtained even though the CD cavity is only partially filled, because more CO2 is bound in solution as crystallization proceeds. When equilibrium is reached as in entries 1–3 (Table 1) the concentration of 1·CO2 is 0.04 M which must be the

The unique reactivity of 5,6-unsubstituted 1,4-dihydropyridine in the Huisgen 1,4-diploar cycloaddition and formal [2 + 2] cycloaddition

• Xiu-Yu Chen,
• Hui Zheng,
• Ying Han,
• Jing Sun and
• Chao-Guo Yan

Beilstein J. Org. Chem. 2023, 19, 982–990, doi:10.3762/bjoc.19.73

• ]naphthyridines 4. Because all reactions in this process are retro-equilibrium reactions, the most thermodynamically stable diastereomer is preferentially produced in the reaction. In the absence of isoquinoline, the 5,6-unsubstituted 1,4-dihydropyridine acts as an active enamine, which adds to dimethyl

Aromatic C–H bond functionalization through organocatalyzed asymmetric intermolecular aza-Friedel–Crafts reaction: a recent update

• Anup Biswas

Beilstein J. Org. Chem. 2023, 19, 956–981, doi:10.3762/bjoc.19.72

• Brønsted acid to generate (N-acyl)(propargyl)imine 90 as intermediate which added to the deprotonated phosphoric acid to form phosphate ester 91 as the next intermediate through an equilibrium process. Then, 1,2-addition by the C3 position of the heteroarene ring to the acylimine intermediate afforded the

First synthesis of acylated nitrocyclopropanes

• Kento Iwai,
• Rikiya Kamidate,
• Khimiya Wada,
• Haruyasu Asahara and
• Nagatoshi Nishiwaki

Beilstein J. Org. Chem. 2023, 19, 892–900, doi:10.3762/bjoc.19.67

• the graph. In addition, we confirmed that isolated cyclopropane 1e did not change upon treatment with (diacetoxyiodo)benzene and tetrabutylammonium iodide. These findings indicate that no equilibrium existed between cyclopropane 1e and dihydrofuran 8e, and that these products were competitively formed

Light-responsive rotaxane-based materials: inducing motion in the solid state

• Adrian Saura-Sanmartin

Beilstein J. Org. Chem. 2023, 19, 873–880, doi:10.3762/bjoc.19.64

• examples, a light input leads to the observation of motion into condensed phases, both at the level of intertwined components and in terms of macroscopic changes. Despite these promising results reported so far, there are some issues which should be overcome, such as the photostationary equilibrium of some

A fluorescent probe for detection of Hg²⁺ ions constructed by tetramethyl cucurbit[6]uril and 1,2-bis(4-pyridyl)ethene

• Xiaoqian Chen,
• Naqin Yang,
• Yue Ma,
• Xinan Yang and
• Peihua Ma

Beilstein J. Org. Chem. 2023, 19, 864–872, doi:10.3762/bjoc.19.63

• that TMeQ[6] and G form an inclusion complex with a host–guest ratio of 1:1 and the equilibrium association constant (Ka) was 2.494 × 104 M−1. The G@TMeQ[6] fluorescent probe can sensitively recognize Hg2+ ions by fluorescence enhancement. The linear range is 0.33 × 10−5–1.65 × 10−5 mol·L−1, R2

• ] (1.0 × 10−4 mol·L−1, 1.00 mL) was gradually added to the aqueous solution of G, and the exothermic isotherms (Figure S1 in Supporting Information File 1) and thermodynamic data (Table 1) were obtained. The equilibrium association constant (Ka) of G and TMeQ[6] is 2.494 × 104 M−1, ΔH = −88.43 kJ/mol

Eschenmoser coupling reactions starting from primary thioamides. When do they work and when not?

• Lukáš Marek,
• Jiří Váňa,
• Jan Svoboda and
• Jiří Hanusek

Beilstein J. Org. Chem. 2023, 19, 808–819, doi:10.3762/bjoc.19.61

• observed in both MeCN and DMF which was in equilibrium with the starting compounds in a ratio of approximately 1:2. The addition of a base or any thiophile always caused only the decomposition to a complex mixture of products in which no ECR product was detected. Next, we performed modification of the

A new oxidatively stable ligand for the chiral functionalization of amino acids in Ni(II)–Schiff base complexes

• Alena V. Dmitrieva,
• Oleg A. Levitskiy,
• Yuri K. Grishin and
• Tatiana V. Magdesieva

Beilstein J. Org. Chem. 2023, 19, 566–574, doi:10.3762/bjoc.19.41

• Michael acceptor. A number of thiols was taken as the model compounds. The reaction was performed under thermodynamic conditions reported in [41], to compare the thermodynamically controlled stereoselectivity of L7 and L1. The use of a 2 molar excess of K2CO3 induces the equilibrium between the isomers

Phenanthridine–pyrene conjugates as fluorescent probes for DNA/RNA and an inactive mutant of dipeptidyl peptidase enzyme

• Josipa Matić,
• Tana Tandarić,
• Marijana Radić Stojković,
• Filip Šupljika,
• Zrinka Karačić,
• Ana Tomašić Paić,
• Lucija Horvat,
• Robert Vianello and
• Lidija-Marija Tumir

Beilstein J. Org. Chem. 2023, 19, 550–565, doi:10.3762/bjoc.19.40

• studied compound. After mixing polynucleotides/protein with studied compounds it was observed that the equilibrium was reached in less than 120 seconds. Compounds Phen-Py-1 and Phen-Py-2 showed a decrease of their excimer fluorescence emission intensity upon time. Therefore, buffer solutions of compounds

Access to cyclopropanes with geminal trifluoromethyl and difluoromethylphosphonate groups

• Ita Hajdin,
• Romana Pajkert,
• Mira Keßler,
• Jianlin Han,
• Haibo Mei and
• Gerd-Volker Röschenthaler

Beilstein J. Org. Chem. 2023, 19, 541–549, doi:10.3762/bjoc.19.39

• then involved in the next catalytic cycle and thus removed from the equilibrium between Int4 and Pr + CuI. In addition, since TS2 is an early transition state and the potential is concomitantly very flat, only TS2_2 was found by means of regular optimization towards a first order saddle point. For the

Discrimination of β-cyclodextrin/hazelnut (Corylus avellana L.) oil/flavonoid glycoside and flavonolignan ternary complexes by Fourier-transform infrared spectroscopy coupled with principal component analysis

• Nicoleta G. Hădărugă,
• Gabriela Popescu,
• Dina Gligor (Pane),
• Cristina L. Mitroi,
• Sorin M. Stanciu and
• Daniel Ioan Hădărugă

Beilstein J. Org. Chem. 2023, 19, 380–398, doi:10.3762/bjoc.19.30

• for preparation. On the other hand, similar methods such as spray-drying do not provide intimate contact between the three types of components for a sufficient period of time to reach the association–dissociation equilibrium [1][27][67]. In this study, the recovery yields were in the range of 51.5

Recommendations for performing measurements of apparent equilibrium constants of enzyme-catalyzed reactions and for reporting the results of these measurements

• Robert N. Goldberg,
• Robert T. Giessmann,
• Peter J. Halling,
• Carsten Kettner and
• Hans V. Westerhoff

Beilstein J. Org. Chem. 2023, 19, 303–316, doi:10.3762/bjoc.19.26

• , Free University Amsterdam, The Netherlands School of Biological Sciences, Faculty of Biology, Medicine, and Health, University of Manchester, Manchester, UK 10.3762/bjoc.19.26 Abstract The measurement of values of apparent equilibrium constants K′ for enzyme-catalyzed reactions involve a substantial

• number of critical details, neglect of which could lead to systematic errors. Here, interferences, impurities in the substances used, and failure to achieve equilibrium are matters of substantial consequence. Careful reporting of results is of great importance if the results are to have archival value

• . Thus, attention must be paid to the identification of the substances, specification of the reaction(s), the conditions of reaction, the definition of the equilibrium constant(s) and standard states, the use of standard nomenclature, symbols, and units, and uncertainties. This document contains a

Improving the accuracy of ³¹P NMR chemical shift calculations by use of scaling methods

• William H. Hersh and
• Tsz-Yeung Chan

Beilstein J. Org. Chem. 2023, 19, 36–56, doi:10.3762/bjoc.19.4

• tetracoordinate phosphorus compounds that allows scaling of the readily accessible DFT chemical shifts. The present method follows established norms [15] of optimization of compound geometries in solution and weighting of the calculated chemical shifts on the basis of calculated equilibrium ratios in solutions of

Combining the best of both worlds: radical-based divergent total synthesis

• Kyriaki Gennaiou,
• Antonios Kelesidis,
• Maria Kourgiantaki and
• Alexandros L. Zografos

Beilstein J. Org. Chem. 2023, 19, 1–26, doi:10.3762/bjoc.19.1

• . Interestingly, irradiation at 365 nm even in the presence of photosensitizer and O2 failed to furnish (+)-jungermatrobrunin A (89), and 90 was obtained as the sole product, albeit in low yield (14%). Attempts to optimize the yield always afforded recovered 88, hinting at a potential equilibrium between 88 and