Red light excitation: illuminating photocatalysis in a new spectrum

• Lucas Fortier,
• Corentin Lefebvre and
• Norbert Hoffmann

Beilstein J. Org. Chem. 2025, 21, 296–326, doi:10.3762/bjoc.21.22

• thulium nanoparticles [26] and the use of a molybdenum-centered [27] and tungsten-centered complexes have been described in the literature [28]. The work by O. S. Wenger et al. introduces a system that mimics the Z-scheme of photosynthesis, utilizing a copper(I) bis(α-diimine) complex in combination with

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

• of the developed protocol was demonstrated on a gram-scale reaction, where the corresponding product 200 was obtained with an acceptable decrease of yield and enantioselectivity (65%, 94% ee). Mechanistically, a chemo- and regioselective nucleophilic addition followed by dehydration leads to diimine

Selectivity control towards CO versus H₂ for photo-driven CO₂ reduction with a novel Co(II) catalyst

• Lisa-Lou Gracia,
• Philip Henkel,
• Olaf Fuhr and
• Claudia Bizzarri

Beilstein J. Org. Chem. 2023, 19, 1766–1775, doi:10.3762/bjoc.19.129

• maintaining high selectivity for carbon products. Results and Discussion Synthesis and characterization of the new Co(II)-based catalyst The novel cobalt(II) complex 1 was synthesized in dry methanol (MeOH) by mixing in a 2:1 ratio, the chelating diimine ligand, 1-benzyl-4-(quinolin-2-yl)-1H-1,2,3-triazole

• (NCS)2(NN) complexes, where NN is a chelating diimine compound such as pyridyl-tetrazole [44], or a pyridine-oxazole [45]. The bond lengths are very similar when comparing the polymorphs 1a and 1b. Nevertheless, the bond angles vary significantly (see Table S2 in Supporting Information File 1

CuAAC-inspired synthesis of 1,2,3-triazole-bridged porphyrin conjugates: an overview

• Dileep Kumar Singh

Beilstein J. Org. Chem. 2023, 19, 349–379, doi:10.3762/bjoc.19.29

• 85 and porphyrin-psoralen conjugate 87 could be potential candidates for PDT applications. Recently, Charisiadis et al. [45] explored this modular click chemistry protocol for the synthesis of a noble metal-free meso-triazole cobalt porphyrin diimine-dioxime conjugate 91 by covalently connecting a

• zinc porphyrin sensitizer with a H2-evolving cobalt diimine dioxime catalyst. First, the Zn porphyrin 88b was coupled with the copper diiminedioxime complex 89 via the CuAAC click reaction to give porphyrin complex 90 in 74% yield (Scheme 18). Furthermore, a stable Co(III) complex was obtained by the

• ) CuSO4∙5H2O, sodium ascorbate, DMF/H2O (1:1), 80 °C, 32–168 h (iii) CHCl3, aq HCl (25%), 1 h (iv) MeI (120 equiv), DMF, rt, 36–72 h. Synthesis of meso-triazole-cobalt-porphyrin diimine-dioxime conjugate 91. Reactions conditions: (i) KOH, THF/MeOH/H2O, (ii) CuSO4·5H2O, sodium ascorbate, CH2Cl2/H2O/MeOH

Steroid diversification by multicomponent reactions

• Leslie Reguera,
• Cecilia I. Attorresi,
• Javier A. Ramírez and
• Daniel G. Rivera

Beilstein J. Org. Chem. 2019, 15, 1236–1256, doi:10.3762/bjoc.15.121

• groups like CH3 and OMe does only partially. Both steric and electronic effects can be explained from the reactivity of the diimine intermediate. An electron-withdrawing group promotes the nucleophilic attack of the ketoimine N by increasing the partially positive charge of the imine C. In general

• . Thus, cholanic dicarboxylic acids 73 and 74 were macrocyclized with a paraformaldehyde-derived diimine and two different aryl diisocyanides to furnish steroidal cages 75 and 76 in good yields considering the structural complexity created in a single synthetic operation. It is worth mentioning that due

Synthesis of (macro)heterocycles by consecutive/repetitive isocyanide-based multicomponent reactions

• Angélica de Fátima S. Barreto and
• Carlos Kleber Z. Andrade

Beilstein J. Org. Chem. 2019, 15, 906–930, doi:10.3762/bjoc.15.88

• , polyether, peptidic and steroidal tethers. Scheme 33 shows a template-driven approach to macrotricycles 170, which were obtained from preformed diimine 168 and addition of diacid 169 and diisocyanide 130 as building blocks. Conclusion Based on the many examples shown herein, one can conclude that the

Hypervalent organoiodine compounds: from reagents to valuable building blocks in synthesis

• Gwendal Grelier,
• Benjamin Darses and
• Philippe Dauban

Beilstein J. Org. Chem. 2018, 14, 1508–1528, doi:10.3762/bjoc.14.128

• copper(I) complex [Cu(MeCN)4]BF4. The reaction gives access to versatile building blocks while generating only N2 as side-product (Scheme 11a) [46]. Worth of mention is the use of a 1,2-diimine ligand 34 that is crucial to obtain good conversions. Compounds 31 resulting from the gem-addition of the

Solvent-free sonochemistry: Sonochemical organic synthesis in the absence of a liquid medium

• Deborah E. Crawford

Beilstein J. Org. Chem. 2017, 13, 1850–1856, doi:10.3762/bjoc.13.179

• order to overcome this problem, the particle size of both starting materials was reduced further to <200 µm and sonicated for 60 minutes, resulting in a dark red powder (Figure 5). 1H NMR spectroscopy showed that the reaction had fully converted to the desired product – the desired diimine, 1 (Figure 6

• . Reaction mixture before and after ultrasonic irradiation for 60 minutes. 1H NMR spectrum of diimine 1 in CDCl3/EtOD. 1H NMR spectrum of 1,3-indandione 2 in DMSO-d6. Reaction between o-vanillin and 1,2-phenylenediamine by ultrasonic irradiation for 60 minutes. Aldol reaction between ninhydrin and dimedone

Nitration of 5,11-dihydroindolo[3,2-b]carbazoles and synthetic applications of their nitro-substituted derivatives

• Roman A. Irgashev,
• Nikita A. Kazin,
• Gennady L. Rusinov and
• Valery N. Charushin

Beilstein J. Org. Chem. 2017, 13, 1396–1406, doi:10.3762/bjoc.13.136

• 6,12-dinitro-ICZs, giving the ICZ-quinone diimine A. Then the intermediate A is hydrolyzed under acidic conditions into ICZ-quinone B, which is reduced into 6,12-unsubstituted ICZ derivatives (Scheme 6). The suggested mechanism is only a hypothesis, which is based on a similar reduction of

NMR reaction monitoring in flow synthesis

• M. Victoria Gomez and
• Antonio de la Hoz

Beilstein J. Org. Chem. 2017, 13, 285–300, doi:10.3762/bjoc.13.31

• -phenylenediamine and isobutyraldehyde to form the diimine product and good results and reproducibility were obtained. The authors consider that this technology can be used to determine the mechanistic and kinetic aspects of reactions without a specialized flow probe and using different kinds of spectrometers with

Highly bulky and stable geometry-constrained iminopyridines: Synthesis, structure and application in Pd-catalyzed Suzuki coupling of aryl chlorides

• Yi Lai,
• Zhijian Zong,
• Yujie Tang,
• Weimin Mo,
• Nan Sun,
• Baoxiang Hu,
• Zhenlu Shen,
• Liqun Jin,
• Wen-hua Sun and
• Xinquan Hu

Beilstein J. Org. Chem. 2017, 13, 213–221, doi:10.3762/bjoc.13.24

• iminopyridylpalladium chlorides were developed. The steric environment adjacent to the nitrogen atom in the pyridine rings and diimine parts enhanced the thermal stability of the palladium species. Bulkier groups at the imino group stabilized the palladium species and the corresponding palladium chlorides showed high

• comprise symmetrical frameworks, such as bipyridine [44][45][46], biimidazole [47][48], and diimine [49][50][51][52][53]. Moreover iminopyridines were attractive for a more straightforward preparation, the condensation of pyridine-2-carboxaldehyde or ketone and the relevant primary amines. By this work a

• the nitrogen in pyridine rings and diimine parts enhanced the thermal stability of metal species, albeit under harsh conditions [65][66][67][68]. Therefore, Figure 1 schematically illustrates various substituents of iminopyridines constraining the geometrical influence around the palladium center. In

Benzothiadiazole oligoene fatty acids: fluorescent dyes with large Stokes shifts

• Lukas J. Patalag and
• Daniel B. Werz

Beilstein J. Org. Chem. 2016, 12, 2739–2747, doi:10.3762/bjoc.12.270

• the BTD headgroup one could regard the fluorogenic core as an oligoene with a geminal diimine acceptor group. Since oligoene absorptions are well-known we anticipated here to access a somehow red-shifted level of excitation energy. Indeed, a bathochromic shift of more than 60 nm relative to a

Catalytic Wittig and aza-Wittig reactions

• Zhiqi Lao and
• Patrick H. Toy

Beilstein J. Org. Chem. 2016, 12, 2577–2587, doi:10.3762/bjoc.12.253

• example of a catalytic aza-Wittig reaction as part of their research on phosphine oxide-catalyzed carbodiimide synthesis (Scheme 13) [30]. In their reaction they used phosphine oxide 40 as the catalyst in the reaction between diisocyanate 41 and benzaldehyde (42, 2 equivalents) to form diimine 43 and

Efficient synthetic protocols for the preparation of common N-heterocyclic carbene precursors

• Morgan Hans,
• Jan Lorkowski,
• Albert Demonceau and
• Lionel Delaude

Beilstein J. Org. Chem. 2015, 11, 2318–2325, doi:10.3762/bjoc.11.252

• ]. Furthermore, this last reagent does not lead to the formation of water, which can hydrolyze the starting diimine and has a deleterious influence on the reaction course. Thus, we adopted the experimental procedure carefully optimized by Hintermann to obtain IMes·HCl in ca. 85% yield (Scheme 5). We were also

• starting from widely available, acyclic reagents (Scheme 6). First, the condensation of glyoxal with two equivalents of mesitylamine afforded the corresponding diimine, as described above for the synthesis of IMes·HCl and IMes·HBF4 (cf. Scheme 5). Next, the diimine was reduced into a diamine with sodium

• ability to maintain the intermediate diimine in the required s-cis conformation [71]. Concentrated hydrochloric acid was added as the counterion source and the final imidazolium product was isolated in 50–60% yield. We further improved this procedure through the use of chlorotrimethylsilane as the

Selected synthetic strategies to cyclophanes

• Sambasivarao Kotha,
• Mukesh E. Shirbhate and
• Gopalkrushna T. Waghule

Beilstein J. Org. Chem. 2015, 11, 1274–1331, doi:10.3762/bjoc.11.142

• generate cyclophane derivative 193 containing an α-diimine functionality. Subsequently, the hydrogenation of 193 gave cyclophane 195. The removal of the template under hydrogenolytic conditions gave the macrocyclic compound 194 (Scheme 31). In continuation of earlier work [145], Kotha and co-workers have

Nonanebis(peroxoic acid): a stable peracid for oxidative bromination of aminoanthracene-9,10-dione

• Vilas Venunath Patil and
• Ganapati Subray Shankarling

Beilstein J. Org. Chem. 2014, 10, 921–928, doi:10.3762/bjoc.10.90

• was surmised that in the presence of oxidant these substrates form a diimine type product (similar to oxidative hair dye mechanism) [33], which makes the ring unreactive towards electrophilic substitution. Since Oxone and 50% hydrogen peroxide showed good results with substrate 1a, we have checked the

Substrate dependent reaction channels of the Wolff–Kishner reduction reaction: A theoretical study

• Shinichi Yamabe,
• Guixiang Zeng,
• Wei Guan and
• Shigeyoshi Sakaki

Beilstein J. Org. Chem. 2014, 10, 259–270, doi:10.3762/bjoc.10.21

• hydrazine (Me2C=N–NH2) was obtained. The channel involves two likely proton-transfer routes. However, it was found that the base-free reaction was unlikely at the N2 extrusion step from the isopropyl diimine intermediate (Me2C(H)–N=N–H). Two base-catalyzed reactions were investigated by models of the ketone

• , H2N–NH2 and OH−(H2O)7. Here, ketones are acetone and acetophenone. While routes of the ketone → hydrazone → diimine are similar, those from the diimines are different. From the isopropyl diimine, the N2 extrusion and the C–H bond formation takes place concomitantly. The concomitance leads to the

• propane product concertedly. From the (1-phenyl)ethyl substituted diimine, a carbanion intermediate is formed. The para carbon of the phenyl ring of the anion is subject to the protonation, which leads to a 3-ethylidene-1,4-cyclohexadiene intermediate. Its [1,5]-hydrogen migration gives the ethylbenzene

New syntheses of 5,6- and 7,8-diaminoquinolines

• Maroš Bella and
• Viktor Milata

Beilstein J. Org. Chem. 2013, 9, 2669–2674, doi:10.3762/bjoc.9.302

• hydrochloride 5 with diimine 7 [18][19] proceeded smoothly at room temperature affording pyridoquinoxaline 8 in high yield (Scheme 2). The same reaction sequence (chlorination and reductive deselenation) was applied to selenadiazolo[3,4-f]quinolone 9 (Scheme 3). The treatment of selenadiazoloquinolone 9 with

• ; N, 18.00. Pyrido[2,3-f]quinoxaline (8). Diimine 7 (113 mg, 0.51 mmol) was added to a stirred solution of hydrochloride 5 (100 mg, 0.51 mmol) in MeOH (8 mL) and stirring was continued at room temperature for 1.5 h. The volatiles were evaporated under reduced pressure and the residue was purified by

Micro-flow synthesis and structural analysis of sterically crowded diimine ligands with five aryl rings

• Shinichiro Fuse,
• Nobutake Tanabe,
• Akio Tannna,
• Yohei Konishi and
• Takashi Takahashi

Beilstein J. Org. Chem. 2013, 9, 2336–2343, doi:10.3762/bjoc.9.268

• , Yokohama 227-8502, Japan 10.3762/bjoc.9.268 Abstract Sterically crowded diimine ligands with five aryl rings were prepared in one step in good yields using a micro-flow technique. X-ray crystallographic analysis revealed the detailed structure of the bulky ligands. The nickel complexes prepared from the

• ligands exerted high polymerization activity in the ethylene homopolymerization and copolymerization of ethylene with polar monomers. Keywords: amidine formation; diimine; flow chemistry; polymerization; Introduction The design of a ligand is a key step in the development of new catalysts because the

• ligand framework influences the reactivity of the metal center. That is why sterically crowded and neutral-chelating diimine ligands have garnered a great deal of attention [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17]. In recent years, N-aryl 1,3,5-triazapenta-1,4-dienes 1 and 2 have been

True and masked three-coordinate T-shaped platinum(II) intermediates

• Manuel A. Ortuño,
• Salvador Conejero and
• Agustí Lledós

Beilstein J. Org. Chem. 2013, 9, 1352–1382, doi:10.3762/bjoc.9.153

• tetramethylethylenediamine (tmeda) [63]. X-ray crystallography of S6a·BArF and S6c·BArF verified the solvent coordination [64]. Diimine analogues, valuable in C–H bond-activation processes, have been extensively reported elsewhere (S7) [65][66][67][68][69][70][71][72]. Later, Tilset’s group prepared and characterized a set

Spin state switching in iron coordination compounds

• Philipp Gütlich,
• Ana B. Gaspar and
• Yann Garcia

Beilstein J. Org. Chem. 2013, 9, 342–391, doi:10.3762/bjoc.9.39

• compounds known possess an [N6] donor atom set, i.e., an [FeN6] chromophor with N-coordinated ligands of variable denticity. A few examples with other donor-atom sets, e.g., N4O2 [37][38][39][40], P4Cl2, have also been reported [41]. [FeN6] systems of iron(II) involve, for instance, [Fe(diimine)2(NCS)2

• ] complexes, among them the classical complexes with 1,10-phenanthroline (phen) and 2,2'-bipyridine (bipy) as bisdentate diimine ligands, which were among the first SCO compounds of iron(II) reported in the literature [14][15]. An example of [FeN6] complexes with trisdentate N-donor ligands is bis[hydro-tris

• (pyrazolyl-borato)]iron(II) [42][43] and related systems. Thermal SCO has been observed with [Fe(diimine)2(NCS)2] complexes employing a large variety of diimine ligands and also with iron(II) complexes containing derivatives of unidentate pyridine [44], bridging diimine and bis(unidentate) ligand components

Screening of ligands for the Ullmann synthesis of electron-rich diaryl ethers

• Nicola Otto and
• Till Opatz

Beilstein J. Org. Chem. 2012, 8, 1105–1111, doi:10.3762/bjoc.8.122

• L19 and L20 but also the N,O-chelating phosphonate ligand L21 showed a significant catalytic activity. From the group of diimine ligands, L28 [30] gave the best results. It should be noted that also in this class, structurally related ligands showed drastically different catalytic activities in the

Predicting the UV–vis spectra of oxazine dyes

• Scott Fleming,
• Andrew Mills and
• Tell Tuttle

Beilstein J. Org. Chem. 2011, 7, 432–441, doi:10.3762/bjoc.7.56

• ; oxazine; TD-DFT; UV–vis; Introduction Oxazine dyes are a subclass of quinone imines, which are all based upon the p-benzoquinone imine or -diimine scaffold. Other important subclasses within the quinone imines include, the azine dyes and thiazine dyes. The structural relationships described are

Reciprocal polyhedra and the Euler relationship: cage hydrocarbons, C_nH_n and closo-boranes [B_xH_x]²⁻

• Michael J. McGlinchey and
• Henning Hopf

Beilstein J. Org. Chem. 2011, 7, 222–233, doi:10.3762/bjoc.7.30

• was converted in several cyclization steps to the diol 51. Oxidation and condensation of the resulting ketoaldehyde then provided the mono ketone 52, which was photochemically ring-closed to the secododecahedrene 53. After diimine hydrogenation to 54 only one C–C bond in the nearly completed sphere