Substituent effects in N-acetylated phenylazopyrazole photoswitches

• Radek Tovtik,
• Dennis Marzin,
• Pia Weigel,
• Stefano Crespi and
• Nadja A. Simeth

Beilstein J. Org. Chem. 2025, 21, 830–838, doi:10.3762/bjoc.21.66

• discovered that simple acylation of the pyrazole moiety leads to increased quantum yields of isomerization, long Z-isomer life-times, good spectral separation, and high photostability. Keywords: azobenzenes; azopyrazoles; photochromism; photoswitches; substituent effects; Introduction Organic photoswitches

• , we were interested to study the photoswitching properties of eleven novel N-acetylated analogous NAc-PAPs and the influence of substituent effects. Furthermore, we compared their photochromism with a set of 22 known N-methylated (NMe-) and unfunctionalized (NH-) PAPs in moderate to good yields (66–85

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

• ], which in many cases is the only way to understand pure substituent effects (e.g., on catalysis). To enable the validation of this process, experimentalists must collect data relevant to benchmarking computations: binding constants, kinetic barriers, crystal structures. In turn, this process will be

Tunable full-color dual-state (solution and solid) emission of push–pull molecules containing the 1-pyrindane moiety

• Anastasia I. Ershova,
• Sergey V. Fedoseev,
• Konstantin V. Lipin,
• Mikhail Yu. Ievlev,
• Oleg E. Nasakin and
• Oleg V. Ershov

Beilstein J. Org. Chem. 2024, 20, 3016–3025, doi:10.3762/bjoc.20.251

• even more pronounced for compound 1i than for 1c due to presence of the stronger electron-donating group. Then, the substituent effects on the spectral properties of stilbazoles 1a–i were studied in two different solvents: nonpolar toluene (Table 2) and highly polar DMSO (Table 3). The absorption

Regioselective alkylation of a versatile indazole: Electrophile scope and mechanistic insights from density functional theory calculations

• Pengcheng Lu,
• Luis Juarez,
• Paul A. Wiget,
• Weihe Zhang,
• Krishnan Raman and
• Pravin L. Kotian

Beilstein J. Org. Chem. 2024, 20, 1940–1954, doi:10.3762/bjoc.20.170

• employed as nucleophiles in chemical transformations, and a mixture of both N1- and N2-alkylated products is formed, depending on the reaction conditions, with little selectivity in regards to substituent effects [27][28][29][30][31][32][33]. Considering the importance of indazoles as a widely used

Kinetically stabilized 1,3-diarylisobenzofurans and the possibility of preparing large, persistent isoacenofurans with unusually small HOMO–LUMO gaps

• Qian Liu and
• Glen P. Miller

Beilstein J. Org. Chem. 2024, 20, 1099–1110, doi:10.3762/bjoc.20.97

• . We previously studied substituent effects in acenes and reported that several substituents promote photooxidative resistance in pentacenes [5] and larger acenes including heptacene [6] and nonacene [7]. One or more substituents that promote photooxidative resistance by quenching singlet oxygen could

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

• case of 1,3-cyclohexadiene 2e, the amine was expected to attack the π-allyl palladium from the exo side. Considering that substituent effects might affect the regioselectivity in this MCR, we further investigated the 1,4-/1,2-addition selectivity with 1-phenyl-substituted 1,3-dienes 2f–i. Interestingly

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

• undertaking a 1H NMR spectroscopic kinetic survey of solvent, ligand, and substituent effects on the general reaction 1 → 3 (with a variety of N-protecting groups), to supplement known qualitative observations. We found that, (1) electron-withdrawing phosphines accelerate hydroamination, (2) reactions are

• insignificant to significant. The reaction demonstrates features of being driven by both Lewis acidity of gold and proton transfer, instead of being localized to one of the two regimes. Furthermore, substituent effects (more reactive with more Lewis basic substrates) hint at gold carbonyl interactions being

Ferrocenoyl-adenines: substituent effects on regioselective acylation

• Mateja Toma,
• Gabrijel Zubčić,
• Jasmina Lapić,
• Senka Djaković,
• Davor Šakić and
• Valerije Vrček

Beilstein J. Org. Chem. 2022, 18, 1270–1277, doi:10.3762/bjoc.18.133

Electrochemical and spectroscopic properties of twisted dibenzo[g,p]chrysene derivatives

• Tomoya Imai,
• Ryuhei Akasaka,
• Naruhiro Yoshida,
• Toru Amaya and
• Tetsuo Iwasawa

Beilstein J. Org. Chem. 2022, 18, 963–971, doi:10.3762/bjoc.18.96

• -2), the Eox1 is lower by only 0.15 V than that of DBC. It has also been reported that the oxidation potential of MeO-DBC-3, in which the MeO groups are attached at both X and Y, is 0.06 V higher than that for MeO-DBC-1. These remarkable substituent effects are an interesting and important finding

Morita–Baylis–Hillman reaction of 3-formyl-9H-pyrido[3,4-b]indoles and fluorescence studies of the products

• Nisha Devi and
• Virender Singh

Beilstein J. Org. Chem. 2022, 18, 926–934, doi:10.3762/bjoc.18.92

• exhibit excellent fluorescence characteristics. Different parameters like contact time, concentration, solvent effects and substituent effects were examined for obtaining the optimal results. It was observed that the MBH derivatives exhibited excellent fluorescence characteristics at a concentration of 5

Iron-catalyzed domino coupling reactions of π-systems

• Austin Pounder and
• William Tam

Beilstein J. Org. Chem. 2021, 17, 2848–2893, doi:10.3762/bjoc.17.196

• reaction begins with a radical addition to the acrylamide 60 followed by subsequent radical cyclization with the aryl ring. A few substituent effects were noted, namely ortho-substituents on the aryl ring were detrimental to the reaction. Moreover, terminal alkenes preformed poorer than their 1,1

Regioselective N-alkylation of the 1H-indazole scaffold; ring substituent and N-alkylating reagent effects on regioisomeric distribution

• Ryan M. Alam and
• John J. Keating

Beilstein J. Org. Chem. 2021, 17, 1939–1951, doi:10.3762/bjoc.17.127

• . C-3 substituted indazole derivatives (12–24) employed to investigate C-3 substituent effects on indazole N-alkylation regioselectivity. Synthetic approaches to N-1 substituted indazole derivatives [12][13][14]. N-Alkylation of indazole 9 under Mitsunobu conditions shows a strong preference (ratio N

• , solvent, and temperature.a Indazole C-3 substituent effects. Effect of NaH and THF on N-1 regioselectivity.a Effect of indazole benzenoid ring substituents on N-1:N-2 regioselectivity.a Effect of 15-crown-5 on the regioselective N-alkylation of indazole 9, in the presence of NaH in THF.a Alkylating

Synthesis of (Z)-3-[amino(phenyl)methylidene]-1,3-dihydro-2H-indol-2-ones using an Eschenmoser coupling reaction

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

Beilstein J. Org. Chem. 2021, 17, 527–539, doi:10.3762/bjoc.17.47

• carbanion nucleophilicity and these two effects are opposing. The influence of the substituent effects, as quantified using Hammett’s substituent constants [35], on the yields can be represented graphically (Figure 2). Reaction of 1a–e with secondary thiobenzamides 3a–i Secondary thiobenzamides 3a–i also

Styryl-based new organic chromophores bearing free amino and azomethine groups: synthesis, photophysical, NLO, and thermal properties

• Anka Utama Putra,
• Deniz Çakmaz,
• Nurgül Seferoğlu,
• Alberto Barsella and
• Zeynel Seferoğlu

Beilstein J. Org. Chem. 2020, 16, 2282–2296, doi:10.3762/bjoc.16.189

• for 3 in DCM was 0.01 and that of 8 in PhMe was 0.11. Substituent effects The prepared Schiff bases exhibited greater red shifts than the styryl counterparts (3–7) in both, absorption and emission spectra. For instance, in DCM, dye 8 showed absorption and emission maxima at 546 and 636 nm, whereas the

Reactions of 3-aryl-1-(trifluoromethyl)prop-2-yn-1-iminium salts with 1,3-dienes and styrenes

• Thomas Schneider,
• Michael Keim,
• Bianca Seitz and
• Gerhard Maas

Beilstein J. Org. Chem. 2020, 16, 2064–2072, doi:10.3762/bjoc.16.173

• characteristics of the C‒F bond [6][7] are the basis for the electronic and steric properties of the CF3 group, such as a strong electron-withdrawing (−I) effect, the accumulation of negative charge density in a relatively small volume and the low polarizability of the fluoro atoms. These and other substituent

• effects can modulate the conformational, physicochemical and electronic properties of a molecule. Two major strategies exist to introduce a CF3 group into a target molecule: formation of a carbon‒ or heteroatom‒CF3 bond [8][9] and the use of preformed CF3-substituted building blocks. During our studies on

Exploring the scope of DBU-promoted amidations of 7-methoxycarbonylpterin

• Anna R. Bockman and
• Jeffrey M. Pruet

Beilstein J. Org. Chem. 2020, 16, 509–514, doi:10.3762/bjoc.16.46

• within the NMR tube with a large excess of the amine, the relative rate constants were determined for a representative set of amines (Table 3). These results further highlight the dramatic rate enhancement brought on by substituent effects. Glycine reacted most swiftly, as the carboxylate anion likely

A toolbox of molecular photoswitches to modulate the CXCR3 chemokine receptor with light

• Xavier Gómez-Santacana,
• Sabrina M. de Munnik,
• Tamara A. M. Mocking,
• Niels J. Hauwert,
• Shanliang Sun,
• Prashanna Vijayachandran,
• Iwan J. P. de Esch,
• Henry F. Vischer,
• Maikel Wijtmans and
• Rob Leurs

Beilstein J. Org. Chem. 2019, 15, 2509–2523, doi:10.3762/bjoc.15.244

• used to guide the design iterations. Investigations of positional and substituent effects reveal that halogen substituents on the ortho-position of the outer ring are preferred for conferring partial agonism on the cis form of the ligands. This effect could be expanded by an electron-donating group on

• -isomer, but it should be complemented with other strategies to further increase intrinsic activity. Substituent effects on the outer ring One of the postulated contributors to the CXCR3 agonism effect of parent biaryls such as 1d and 1e is the increased π-electron density of the aromatic rings [24]. A

• is an antagonist, while cis-5b shows only a weak activity (Table 2). Substituent effects on the central ring As shown, substitution of the outer ring with an ortho-bromine in conjunction with a Cl substituent on the central ring appeared to pave the way for efficacy photoswitching but there was still

Small anion-assisted electrochemical potential splitting in a new series of bistriarylamine derivatives: organic mixed valency across a urea bridge and zwitterionization

• Keishiro Tahara,
• Tetsufumi Nakakita,
• Alyona A. Starikova,
• Takashi Ikeda,
• Masaaki Abe and
• Jun-ichi Kikuchi

Beilstein J. Org. Chem. 2019, 15, 2277–2286, doi:10.3762/bjoc.15.220

• with that for 1b. This substituent effect on the oxidation potential is typical for the reported NAr3 system [53]. Because the electron-donating group of the NAr3 unit destabilizes the MV state, the potential splitting for 1a is 50 mV smaller than that for 1b (Figure 2, top). Similar substituent

• effects were previously reported for bis(NAr3) derivatives having π-conjugated bridges [8][9]. Judging from the long N···N distances (e.g., 13.16 Å for 1b+) in the DFT-optimized structure (Figure S5 in Supporting Information File 1), the through-space electrostatic interactions between the NAr3 units

Azologization and repurposing of a hetero-stilbene-based kinase inhibitor: towards the design of photoswitchable sirtuin inhibitors

• Christoph W. Grathwol,
• Nathalie Wössner,
• Sören Swyter,
• Adam C. Smith,
• Enrico Tapavicza,
• Robert K. Hofstetter,
• Anja Bodtke,
• Manfred Jung and
• Andreas Link

Beilstein J. Org. Chem. 2019, 15, 2170–2183, doi:10.3762/bjoc.15.214

• state, as envisioned. Possible reasons could be assigned to substituent effects as demonstrated by Simeth et al. [62]. As recently reported by Schehr et al., reducing agents like DTT, used to prevent enzyme oxidation in crystallization mixtures or in vitro assays, can reduce azo dyes to hydrazine

Click chemistry towards thermally reversible photochromic 4,5-bisthiazolyl-1,2,3-triazoles

• Chenxia Zhang,
• Kaori Morinaka,
• Mahmut Kose,
• Takashi Ubukata and
• Yasushi Yokoyama

Beilstein J. Org. Chem. 2019, 15, 2161–2169, doi:10.3762/bjoc.15.213

• the organic azide we used commercially available benzyl azide. Since 1,2-bis(5-methyl-2-phenylthiazol-4-yl)ethyne was used in our previous research [32][33][34], we employed bisthiazolylethynes as the foundation for the skeleton of the target compounds. In order to examine the substituent effects of

A golden opportunity: benzofuranone modifications of aurones and their influence on optical properties, toxicity, and potential as dyes

• Joza Schmitt and
• Scott T. Handy

Beilstein J. Org. Chem. 2019, 15, 1781–1785, doi:10.3762/bjoc.15.171

• expected due to the lack of direct conjugation with the carbonyl as well as the only modest electronic effects of alkyl, chlorine, and bromine. In general, the substituent effects are all fairly modest and result in fairly moderate changes in the extinction coefficient (although hydroxy substitution does

Homo- and hetero-difunctionalized β-cyclodextrins: Short direct synthesis in gram scale and analysis of regiochemistry

• Gábor Benkovics,
• Mihály Bálint,
• Éva Fenyvesi,
• Erzsébet Varga,
• Szabolcs Béni,
• Konstantina Yannakopoulou and
• Milo Malanga

Beilstein J. Org. Chem. 2019, 15, 710–720, doi:10.3762/bjoc.15.66

• to be converted to 6A,6X-tert-butylsulfenyl-β-CD, in which the carbon atoms C1, C4 and C6 of the glucopyranose rings initially bearing the cap, experience remarkable remote substituent effects detectable in the 13C NMR spectra [8]. This effect is the largest in the case of the AB-substituted

Unprecedented nucleophile-promoted 1,7-S or Se shift reactions under Pummerer reaction conditions of 4-alkenyl-3-sulfinylmethylpyrroles

• Takashi Go,
• Akane Morimatsu,
• Hiroaki Wasada,
• Genzoh Tanabe,
• Osamu Muraoka,
• Yoshiharu Sawada and
• Mitsuhiro Yoshimatsu

Beilstein J. Org. Chem. 2018, 14, 2722–2729, doi:10.3762/bjoc.14.250

• stepwise procedure succeeded to give 7-phenylselenodiol 10a in 91% yield. Next, we performed the Pummerer reaction of N-β-methallyl sulfoxide 5b in order to clarify the substituent effects on the N-alkenyl groups. Surprisingly, the reaction of 5b afforded the intramolecular cyclised pyrroloazepine 11b. The

Revisiting ring-degenerate rearrangements of 1-substituted-4-imino-1,2,3-triazoles

• James T. Fletcher,
• Matthew D. Hanson,
• Joseph A. Christensen and
• Eric M. Villa

Beilstein J. Org. Chem. 2018, 14, 2098–2105, doi:10.3762/bjoc.14.184

• investigation regarding the substituent effects of 4-imino-1,2,3-triazoles on this Dimroth rearrangement is therefore warranted, exemplary results of which are described herein. Results and Discussion The original study of L’abbé regarding this ring-degenerate rearrangement focused on the condensation of 1

• analyzed after 24 h. (While this time point was not necessarily adequate for reaching chemical equilibrium within each dynamic system, it was deemed sufficient to make informative observations regarding the relative influence of substituent effects on product distributions.) Direct, quantitative

• directly measuring complex mixtures of aldehyde and imine products resulting from a dynamic combination of condensation, rearrangement and hydrolysis reactions between 1-substituted-4-formyl-1,2,3-triazoles and aromatic amines, additional insight regarding substituent effects on this process was defined

A conformationally adaptive macrocycle: conformational complexity and host–guest chemistry of zorb[4]arene

• Liu-Pan Yang,
• Song-Bo Lu,
• Arto Valkonen,
• Fangfang Pan,
• Kari Rissanen and
• Wei Jiang

Beilstein J. Org. Chem. 2018, 14, 1570–1577, doi:10.3762/bjoc.14.134

• explained by invoking a solvent reorganization during the formation of 18+@ZB4 complex, which is common for reactions taking place in aqueous solution [41]. Conclusion In summary, we systematically studied the guest binding scope, electronic substituent effects and thermodynamic origin on the molecular