Introduction of peripheral nitrogen atoms to cyclo-meta-phenylenes

• Koki Ikemoto and
• Hiroyuki Isobe

Beilstein J. Org. Chem. 2024, 20, 1207–1212, doi:10.3762/bjoc.20.103

• equilibrium. These results show that the coordination chemistry associated with nitrogen dopants may well be controlled by the locations and directions of the nitrogen atoms. Conclusion Macrocycles with nitrogen atoms doped at the periphery were designed and synthesised, and their electronic properties were

Light on the sustainable preparation of aryl-cored dibromides

• Fabrizio Roncaglia,
• Alberto Ughetti,
• Nicola Porcelli,
• Biagio Anderlini,
• Andrea Severini and
• Luca Rigamonti

Beilstein J. Org. Chem. 2024, 20, 1076–1087, doi:10.3762/bjoc.20.95

• process. Therefore, various forms of oxidative halogenations have been reported over the years. For example, Ishii described the use of the NaBrO3–NaHSO3 couple to slowly generate Br2 through an aqueous redox equilibrium [39]. Few years later, Adimurthy et al. proposed an improved variant based on the

(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

• rate in rat liver microsomes (CLint), while apparent permeability (Papp) and equilibrium solubility are not significantly impacted by the isosteric replacement of the meta-benzene moiety. 1,3-Disubstituted cubanes In addition to their improved synthesis of 1,2-cubanes as ortho-benzene isosteres

Activity assays of NnlA homologs suggest the natural product N-nitroglycine is degraded by diverse bacteria

• Kara A. Strickland,
• Brenda Martinez Rodriguez,
• Ashley A. Holland,
• Shelby Wagner,
• Michelle Luna-Alva,
• David E. Graham and
• Jonathan D. Caranto

Beilstein J. Org. Chem. 2024, 20, 830–840, doi:10.3762/bjoc.20.75

• at nodes indicate Shimodaira–Hasegawa-like approximate likelihood ratio test (SH-aLRT) support (%) and ultrafast bootstrap support (%). NNG degradation by reduced NnlA. Acid–base equilibrium of 3-nitropropionate (3-NP) vs N-nitroglycine (NNG). Iron analyses of purified NnlA homologs. Nitrogen mass

Regioselective quinazoline C2 modifications through the azide–tetrazole tautomeric equilibrium

• Dāgs Dāvis Līpiņš,
• Andris Jeminejs,
• Una Ušacka,
• Anatoly Mishnev,
• Māris Turks and
• Irina Novosjolova

Beilstein J. Org. Chem. 2024, 20, 675–683, doi:10.3762/bjoc.20.61

• –tetrazole tautomeric equilibrium directs the nucleofugal sulfinate from the first step to replace chloride at the C2 position. This transformation is effective with quinazolines bearing electron-rich substituents. Therefore, the title transformations are demonstrated on the 6,7-dimethoxyquinazoline core

• : aromatic nucleophilic substitution; azide–tetrazole equilibrium; 4-azido-2-sulfonylquinazolines; quinazolines; sulfonyl group dance; Introduction The quinazoline core is a privileged structure with a wide range of applications. Quinazoline derivatives exhibit a broad spectrum of biological activities

• azide–tetrazole equilibrium of product 12a was initiated, revealing a singular form present in all solvents. Despite attempts to increase the amount of the azide form with the increase of the temperature in NMR experiments [27], no observable alteration in the tautomeric equilibrium was observed. FTIR

Palladium-catalyzed three-component radical-polar crossover carboamination of 1,3-dienes or allenes with diazo esters and amines

• Geng-Xin Liu,
• Xiao-Ting Jie,
• Ge-Jun Niu,
• Li-Sheng Yang,
• Xing-Lin Li,
• Jian Luo and
• Wen-Hao Hu

Beilstein J. Org. Chem. 2024, 20, 661–671, doi:10.3762/bjoc.20.59

• [32][33][34][35][36][37][59][60][61][62], upon the loss of dinitrogen. The radical I further adds to the terminal position of 1,3-butadiene (2a) to produce hybrid allylPd radical II, which would exist in equilibrium with π-allyl complex III. Following the classical Tsuji–Trost reaction mechanism, a

• , providing another type of hybrid allylPd radical IV. After the equilibrium shifting to the π-allyl complex V, the unsaturated γ-AA derivative 6 would be obtained with the nucleophilic attack of amine 3. The utility of this protocol was further highlighted by scale-up reactions and diverse derivatizations of

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

• also developed tweezers 35 with a semi-rigid 1,4-diphenyl-1,3-butadiyne spacer containing two urea units linked to the aromatic rings and Zn–porphyrin functional units (Figure 19b) [77]. The arms have a free rotation around the rigid diethylene backbone and thus the system is natively in equilibrium

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

• behaves accordingly here [66]. Specific gold–oxygen interactions are typically not invoked in mechanistic discussions, though a gold alcohol complex has been proposed in silyl enol ether protonation [67]. Equilibrium studies by Maier et al. indicate that methanol is more weakly coordinating than alkynes

Elucidating the glycan-binding specificity and structure of Cucumis melo agglutinin, a new R-type lectin

• Jon Lundstrøm,
• Emilie Gillon,
• Valérie Chazalet,
• Nicole Kerekes,
• Antonio Di Maio,
• Ten Feizi,
• Yan Liu,
• Annabelle Varrot and
• Daniel Bojar

Beilstein J. Org. Chem. 2024, 20, 306–320, doi:10.3762/bjoc.20.31

• 10 µL/min. Surfaces were regenerated with 30 s injections of 50 mM NaOH and 1 M NaCl. IC50 was measured using the response at equilibrium for each concentration of competitive sugar that were translated in percentage of inhibition, then plotted against the molar concentration of competitive sugar

• equilibrium, n = 2. Structural insights into the binding mechanism of CMA1. (a, b) Overall representation of the N-terminal domain of CMA1 in complex with (a) LacNAc (Galβ1-4GlcNAc) [29] or (b) GalNAc [30]. Trefoil repeats are colored differently, and cadmium ions are represented as red spheres. (c, d) Close

Synthesis of π-conjugated polycyclic compounds by late-stage extrusion of chalcogen fragments

• Aissam Okba,
• Pablo Simón Marqués,
• Kyohei Matsuo,
• Naoki Aratani,
• Hiroko Yamada,
• Gwénaël Rapenne and
• Claire Kammerer

Beilstein J. Org. Chem. 2024, 20, 287–305, doi:10.3762/bjoc.20.30

• , this class of compounds is prone to valence isomerization via 6π-electrocyclization leading to the formation of heteroatom-containing norcaradiene, and oxepine has been shown to exist in equilibrium with its valence isomer benzene oxide [37]. In contrast with the parent oxepine, which is isolable at

• room temperature, other group-16 heteropines suffer from thermal instability. Indeed, the low activation barrier for S, Se or Te cheletropic extrusion from the norcaradiene valence isomer, combined with the irreversibility of this process, shifts the tautomerization equilibrium and delivers benzene as

Substitution reactions in the acenaphthene analog of quino[7,8-h]quinoline and an unusual synthesis of the corresponding acenaphthylenes by tele-elimination

• Ekaterina V. Kolupaeva,
• Narek A. Dzhangiryan,
• Alexander F. Pozharskii,
• Oleg P. Demidov and
• Valery A. Ozeryanskii

Beilstein J. Org. Chem. 2024, 20, 243–253, doi:10.3762/bjoc.20.24

• equilibrium) under the action of an excess of nucleophiles as bases. Such dianions are characteristic of acenaphthene and have been repeatedly detected in subsequent transformations [18][19]. In our case, the CH-acidity of the CH2CH2 bridge should be even higher under the action of pyridine rings, and, if

Metal-catalyzed coupling/carbonylative cyclizations for accessing dibenzodiazepinones: an expedient route to clozapine and other drugs

• Amina Moutayakine and
• Anthony J. Burke

Beilstein J. Org. Chem. 2024, 20, 193–204, doi:10.3762/bjoc.20.19

• compound 5 into the keto form 4a by using TFA to shift the equilibrium towards the desired product, but this proved to be futile under these conditions, as only the iminol 5 structure was observed. Attempt at accessing dibenzodiazepinone via step-wise synthesis Due to the difficulty encountered in the one

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