Multicomponent syntheses of pyrazoles via (3 + 2)-cyclocondensation and (3 + 2)-cycloaddition key steps

• Ignaz Betcke,
• Alissa C. Götzinger,
• Maryna M. Kornet and
• Thomas J. J. Müller

Beilstein J. Org. Chem. 2024, 20, 2024–2077, doi:10.3762/bjoc.20.178

• of IBX ensured the completion of the reaction sequence [96]. A notable advantage of this method is the ability to reuse the catalyst multiple times. In addition to Yb(PFO)3, zinc triflate can also serve as an effective catalyst for the synthesis of pyrazoles 65. It also catalyzes the oxidation of

1,2-Difluoroethylene (HFO-1132): synthesis and chemistry

• Liubov V. Sokolenko,
• Taras M. Sokolenko and
• Yurii L. Yagupolskii

Beilstein J. Org. Chem. 2024, 20, 1955–1966, doi:10.3762/bjoc.20.171

• -difluoroethylene was based on 1,2-dichloro-1,2-difluoroethane (HCFC-132) [48][49][50][51][52], prepared from 1,1,2,2-tetrachloro-1,2-difluoroethane (CFC-112) by reduction using lithium aluminum hydride [48][49][50][51] or photoreduction (Scheme 2) [51]. The resulting HCFC-132 reacted with zinc [47][49][52] or

Negishi-coupling-enabled synthesis of α-heteroaryl-α-amino acid building blocks for DNA-encoded chemical library applications

• Matteo Gasparetto,
• Balázs Fődi and
• Gellért Sipos

Beilstein J. Org. Chem. 2024, 20, 1922–1932, doi:10.3762/bjoc.20.168

• of ethyl 2-bromoacetate through a pre-activated zinc column (see page 11 in Supporting Information File 1) [44]. The Reformatsky reagent could be obtained in yields varying from 70 to 90% depending on the activation state of the column. The yield of the reaction was determined by titration with

• subsequent re-esterification was necessary to achieve the desired ketoester. Reduction of the oximes Oximes are commonly reduced to the corresponding amines using either palladium on activated carbon and hydrogen gas [65][66][67][68], or with zinc and a Brønsted acid as source of hydrogen [68][69]. Both

• methods were tested and after a brief optimization process, zinc dust and HCl in a mixture of EtOH/dioxane proved to be the best conditions in order to maximize the yield and limit the amino ester instability issues (see Table S6 in Supporting Information File 1). By slightly adjusting the reaction time

The Groebke–Blackburn–Bienaymé reaction in its maturity: innovation and improvements since its 21st birthday (2019–2023)

• Cristina Martini,
• Muhammad Idham Darussalam Mardjan and
• Andrea Basso

Beilstein J. Org. Chem. 2024, 20, 1839–1879, doi:10.3762/bjoc.20.162

New triazinephosphonate dopants for Nafion proton exchange membranes (PEM)

• Fátima C. Teixeira,
• António P. S. Teixeira and
• C. M. Rangel

Beilstein J. Org. Chem. 2024, 20, 1623–1634, doi:10.3762/bjoc.20.145

• phosphite in the presence of zinc(II) bromide allowed the formation of diethyl [hydroxy(4-hydroxyphenyl)methyl]phosphonate (11) and tetraethyl [(4-hydroxyphenyl)methylene]bis(phosphonate) (13), which were separated by column chromatography (Scheme 3). The synthesis of pure tetraethyl [(4-hydroxyphenyl

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

• congestion to the highly reactive 1,3-carbons on the furan ring. Thus, phthaloyl chloride was reacted with mesitylene or 1,3,5-triethylbenzene to produce the corresponding diketones 21 and 22. Each diketone was in turn reacted with zinc metal in glacial acetic acid [9] to afford the corresponding 1,3

• -diarylisobenzofurans 3 and 23. The latter reductions in the presence of zinc likely proceed through the corresponding ketols which are known to undergo ring closure in acidic solution [10][11]. These syntheses utilizing mesitylene or 1,3,5-triethylbenzene are considerably simpler than other approaches that would place

• -filled cuvette. Fluorescence spectra were measured on a FS5 spectrofluorometer (150 W CW Ozone-free xenon arc lamp) from Edinburgh Instruments. 1,3-Dimesitylisobenzofuran (3) To a round bottom flask was added 1,2-phenylenebis(mesitylmethanone) (21, 0.10 g, 0.27 mmol), zinc dust (0.70 g, 11 mmol) and 10

Enantioselective synthesis of β-aryl-γ-lactam derivatives via Heck–Matsuda desymmetrization of N-protected 2,5-dihydro-1H-pyrroles

• Arnaldo G. de Oliveira Jr.,
• Martí F. Wang,
• Rafaela C. Carmona,
• Danilo M. Lustosa,
• Sergei A. Gorbatov and
• Carlos R. D. Correia

Beilstein J. Org. Chem. 2024, 20, 940–949, doi:10.3762/bjoc.20.84

• the palladium source in combination with the pyrazinebisoxazoline ligand, (S)-PyraBox (L1), zinc carbonate as base, and methanol as solvent at 40 °C. These initial conditions furnished 2-methoxypyrrolidines arylated at the 4-position, compound 3, as Heck products as illustrated in Scheme 3. The

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

• reversibly reopened by the addition of TREN as a competitive ligand. The authors reported a slight luminescence quenching in the zinc-closed state with a decrease in the quantum yield from 0.27 to 0.21. However, Hg2+ presented a special behavior with the formation of a 2:1 complex, the closing of the

• tweezers 16 were then synthetized by Vives and co-workers using a 6,6”-substituted terpyridine this time bearing zinc(II)–salphen complexes [47]. The catalytic activity was evaluated in an acetyl transfer reaction between pyridinemethanol derivatives and anhydrides. For the ortho derivative, a rate

• bonding with the two protonated [9]aneN3 units and two water molecules coordinated to the zinc center. More recently, terpyridine was also used by Crassous and co-workers to create a chiroptic switch (Figure 10) [49]. They synthesized tweezers 18 bearing helicene moieties as functional groups. The two

Mechanisms for radical reactions initiating from N-hydroxyphthalimide esters

• Carlos R. Azpilcueta-Nicolas and
• Jean-Philip Lumb

Beilstein J. Org. Chem. 2024, 20, 346–378, doi:10.3762/bjoc.20.35

• reductant, which can be an organic reductant, such as tetrakis(N,N-dimethylamino)ethylene (TDAE) or Hantzsch ester (HE), or a metal such as zinc (Zn0) or manganese (Mn0). Upon fragmentation, radical species 12 is captured by the oxidative addition complex 125, giving rise to NiIII complex 126. The cross

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

• zinc acetate), or 5 mM CdCl2, and in the presence or not of 5 mM GalNAc. Cocrystals of CMA1-Nter in complex with LacNAc (Galβ1-4GlcNAc, Elicityl, #GLY008) were obtained by the addition of 5 mM LacNAc to the protein solution and incubation at room temperature for 30 min prior to crystallization. For

Catalytic multi-step domino and one-pot reactions

• Svetlana B. Tsogoeva

Beilstein J. Org. Chem. 2024, 20, 254–256, doi:10.3762/bjoc.20.25

• facile stereoselective tandem reaction based on the asymmetric conjugate addition of dialkylzinc reagents to unsaturated acylimidazoles, followed by trapping of the intermediate zinc enolate with carbocations [12]. A practical one-pot synthesis of fluorescent pyrazolo[3,4-b]pyridin-6-ones by reacting 5

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

• determined to be 2 and 58 ps, respectively. The observed longer lifetimes attributed to DEA substitution could be due to the larger distance and the Marcus inverted region [143] character, compared with the results obtained for OEF substitution. Guldi et al. synthesized zinc phthalocyanine (ZnPC) covalently

• CS-state formation for 60 depending on the solvent, was also observed for excitation at 458 nm corresponding to the ICT band. A series of multicomponent systems consisting of anilino-substituted TCBD or PCBD coupled with zinc porphyrins (ZnPs) were synthesized, and their photophysical properties were

Biphenylene-containing polycyclic conjugated compounds

• Cagatay Dengiz

Beilstein J. Org. Chem. 2023, 19, 1895–1911, doi:10.3762/bjoc.19.141

• (19) in the presence of activated zinc dust in THF (Scheme 4) [35]. By making minor adjustments to the reaction conditions, such as employing DMF as the solvent and raising the temperature to 100 °C, along with utilizing compound 20 as the starting material, Barton and his team achieved the synthesis

Tying a knot between crown ethers and porphyrins

• Maksym Matviyishyn and
• Bartosz Szyszko

Beilstein J. Org. Chem. 2023, 19, 1630–1650, doi:10.3762/bjoc.19.120

• appreciable effects. Furthermore, zinc(II) porphyrins 1-Zn and TriCP-Zn bound potassium cations forming dimeric assemblies 2, as demonstrated by the absorption and 1H NMR spectra. Although DCP-Zn and MCP-Zn were also capable of forming dimers, the highest stability and the largest level of attraction between

• macrocyclic entities attached to pyrrolic subunits, acted as a receptor for alkali and alkali earth metal cations. Incorporating zinc(II) and nickel(II) into the porphyrin cavity yielded 8-Zn and 8-Ni. Langford and co-workers developed an efficient method for synthesizing a series of porphyrin-appended crown

• sodium(I), zinc(II), magnesium(II), and barium(II) [106][107][108][109]. Association constants of the reported host–guest complexes showed similar values to those of diazacrown ethers [110][111]. Johnston and Gunter presented a crown ether-capped porphyrin receptor 10, which showed unexpected binding

N-Sulfenylsuccinimide/phthalimide: an alternative sulfenylating reagent in organic transformations

• Fatemeh Doraghi,
• Seyedeh Pegah Aledavoud,
• Mehdi Ghanbarlou,
• Bagher Larijani and
• Mohammad Mahdavi

Beilstein J. Org. Chem. 2023, 19, 1471–1502, doi:10.3762/bjoc.19.106

• as a sulfenylating source gave the target product in 93% yield. Knochel and co-workers found that copper acetate can catalyze the cross-coupling reaction between (hetero)aryl, alkyl and benzylic zinc halides 36 with N-thiophthalimides 14 (Scheme 18) [55]. Various metal catalysts, including CrCl2

α-(Aminomethyl)acrylates as acceptors in radical–polar crossover 1,4-additions of dialkylzincs: insights into enolate formation and trapping

• Angel Palillero-Cisneros,
• Paola G. Gordillo-Guerra,
• Fernando García-Alvarez,
• Olivier Jackowski,
• Franck Ferreira,
• Fabrice Chemla,
• Joel L. Terán and
• Alejandro Perez-Luna

Beilstein J. Org. Chem. 2023, 19, 1443–1451, doi:10.3762/bjoc.19.103

• that α-(aminomethyl)acrylates are suitable acceptors for 1,4-additions of dialkylzincs in aerobic conditions. The air-promoted radical–polar crossover process involves the 1,4-addition of an alkyl radical followed by homolytic substitution at the zinc atom of dialkylzinc. Coordination of the nitrogen

• atom to zinc enables this SH2 process which represents a rare example of alkylzinc-group transfer to a tertiary α-carbonyl radical. The zinc enolate thus formed readily undergoes β-fragmentation unless it is trapped by electrophiles in situ. Enolates of substrates having free N–H bonds undergo

• levels of chiral induction, paving the way to enantioenriched β2-amino acids and β2,2-amino acids. Keywords: β-amino acids; tandem reactions; radical–polar crossover; tert-butanesulfinamide; zinc radical transfer; Introduction Dialkylzinc reagents react in aerobic medium with a range of α,β-unsaturated

Synthesis of ether lipids: natural compounds and analogues

• Marco Antônio G. B. Gomes,
• Alicia Bauduin,
• Chloé Le Roux,
• Romain Fouinneteau,
• Wilfried Berthe,
• Mathieu Berchel,
• Hélène Couthon and
• Paul-Alain Jaffrès

Beilstein J. Org. Chem. 2023, 19, 1299–1369, doi:10.3762/bjoc.19.96

Unravelling a trichloroacetic acid-catalyzed cascade access to benzo[f]chromeno[2,3-h]quinoxalinoporphyrins

• Chandra Sekhar Tekuri,
• Pargat Singh and
• Mahendra Nath

Beilstein J. Org. Chem. 2023, 19, 1216–1224, doi:10.3762/bjoc.19.89

• ) porphyrins were transformed to the corresponding free base and zinc(II) benzo[f]chromeno[2,3-h]quinoxalinoporphyrins under standard demetallation and zinc insertion conditions. The absorption and emission properties of the obtained porphyrins were investigated by using UV–visible and fluorescence

• copper complexes of benzo[f]chromeno[2,3-h]quinoxalinoporphyrins 3–7 were converted to the corresponding free-base porphyrinoids 9–13 through a standard demetallation process using conc. H2SO4 in CHCl3 under cooling conditions (Scheme 1). On complexation with zinc by using Zn(OAc)2 in CHCl3/MeOH, free

• -base porphyrins 9, 10 and 13 afforded zinc(II) benzo[f]chromeno[2,3-h]quinoxalinoporphyrins 14–16 in good yields (Scheme 1). The proposed mechanistic pathway for the formation of copper(II) benzo[f]chromeno[2,3-h]quinoxalinoporphyrins 3–8 under one-pot operation is presented in Figure 1. At the

Clauson–Kaas pyrrole synthesis using diverse catalysts: a transition from conventional to greener approach

• Dileep Kumar Singh and
• Rajesh Kumar

Beilstein J. Org. Chem. 2023, 19, 928–955, doi:10.3762/bjoc.19.71

• method using a zinc catalyst. The synthesis of pyrrole derivatives 47 were achieved in moderate to excellent yields without using any co-catalyst, ligands or bases by stirring various aniline derivatives 46 with 2,5-dimethoxytetrahydrofuran (2) in the presence of 5 mol % of Zn(OTf)2 for 8 hours at 70 °C

• . Many zinc catalysts (Zn(OTf)2, Et2Zn, ZnI2, Zn powder, anhydrous ZnCl2, Zn(NO3)2⋅6H2O, ZnSO4⋅H2O, Zn(OAc)2⋅2H2O and ZnO), reaction temperature, time, and catalyst loading was screened for the optimization. After optimizations, 5 mol % Zn(OTf)2 as catalyst, reaction time for 8 h, and temperature of 70

• -substituted pyrroles 43. Synthesis of N-substituted pyrroles 45 by using Co catalyst Co/NGr-C@SiO2-L. Zinc-catalyzed synthesis of N-arylpyrroles 47. Silica sulfuric acid-catalyzed synthesis of pyrrole derivatives 49. Bismuth nitrate-catalyzed synthesis of pyrroles 51. L-(+)-tartaric acid-choline chloride

Asymmetric tandem conjugate addition and reaction with carbocations on acylimidazole Michael acceptors

• Brigita Mudráková,
• Renata Marcia de Figueiredo,
• Jean-Marc Campagne and
• Radovan Šebesta

Beilstein J. Org. Chem. 2023, 19, 881–888, doi:10.3762/bjoc.19.65

• 10.3762/bjoc.19.65 Abstract We present here a stereoselective tandem reaction based on the asymmetric conjugate addition of dialkylzinc reagents to unsaturated acylimidazoles followed by trapping of the intermediate zinc enolate with carbocations. The use of a chiral NHC ligand provides chiral zinc

• enolates in high enantiomeric purities. These enolates are reacted with highly electrophilic onium compounds to afford densely substituted acylimidazoles. DFT calculations helped to understand the reactivity of the zinc enolates derived from acylimidazoles and allowed their comparison with metal enolates

• the reaction temperature led to improved reaction outcomes (Supporting Information File 1, Table S1, entries 2 and 11). We have continued the evaluation of reaction conditions for improving the diastereoselectivity of the reaction. We have tested transmetallation of the in situ-generated zinc enolate

Pyridine C(sp²)–H bond functionalization under transition-metal and rare earth metal catalysis

• Haritha Sindhe,
• Malladi Mounika Reddy,
• Karthikeyan Rajkumar,
• Akshay Kamble,
• Amardeep Singh,
• Anand Kumar and
• Satyasheel Sharma

Beilstein J. Org. Chem. 2023, 19, 820–863, doi:10.3762/bjoc.19.62

Honeycomb reactor: a promising device for streamlining aerobic oxidation under continuous-flow conditions

• Masahiro Hosoya,
• Yusuke Saito and
• Yousuke Horiuchi

Beilstein J. Org. Chem. 2023, 19, 752–763, doi:10.3762/bjoc.19.55

• . From the viewpoint of application to pharmaceutical manufacturing, the residual amount of copper must be controlled according to ICH Q3D [41]. Iron and zinc have low toxicity and are not listed in ICH Q3D. In comparison with the initial reaction rate of 60 min, Fe(NO3)3/TEMPO in Table 1, entry 3 shows

Photocatalytic sequential C–H functionalization expediting acetoxymalonylation of imidazo heterocycles

• Deepak Singh,
• Shyamal Pramanik and
• Soumitra Maity

Beilstein J. Org. Chem. 2023, 19, 666–673, doi:10.3762/bjoc.19.48

• from academia and industry. Herein, we report a direct C-3 acetoxymalonylation of imidazo heterocycles using relay C–H functionalization enabled by organophotocatalysis starring zinc acetate in the triple role of an activator, ion scavenger as well as an acetylating reagent. The mechanistic

• investigation revealed a sequential sp2 and sp3 C–H activation, followed by functionalization driven by zinc acetate coupled with the photocatalyst PTH. A variety of imidazo[1,2-a]pyridines and related heterocycles were explored as substrates along with several active methylene reagents, all generating the

• degassed conditions with or without water only delivered a trace amount (<5%) of the desired products, indicating that aerial oxygen plays a crucial role in the second catalytic cycle for the conversion of 5 to 3a or 4a (Scheme 3C). To determine the role of zinc acetate, a standard reaction of 1a and 2a in

Enolates ambushed – asymmetric tandem conjugate addition and subsequent enolate trapping with conventional and less traditional electrophiles

• Péter Kisszékelyi and
• Radovan Šebesta

Beilstein J. Org. Chem. 2023, 19, 593–634, doi:10.3762/bjoc.19.44

• were successfully employed in asymmetric conjugate additions (ACA) [3][4][5][6][7][8][9], mainly organozinc [10], Grignard [11][12][13], trialkylaluminum [14], or organozirconium reagents [15]. Additions with these reagents lead to corresponding zinc, magnesium, aluminum, and zirconium enolates, which

• Following the seminal work of Feringa in 1997 [21], the tandem asymmetric organozinc conjugate addition followed by subsequent aldol reaction was scarcely applied in the last decade. Welker and Woodward studied the reaction of zinc enolates 2 with chiral acetals 3 (Scheme 2) [22]. The Lewis acid (TiCl4 or

• ) [34]. Encouraged by this, they have also attempted an intramolecular tandem conjugate addition/Michael reaction sequence, which has resulted in the expected cyclization product 30 in a diastereopure form (Scheme 7B). Zinc enolates readily react with allyl iodides 31 or the structurally similar Stork

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

• ) inactive enzyme mutant E451A was examined by fluorimetric titrations and ITC titrations and it was found that Phen-Py-1 binds to the protein with a high affinity (Table 3). This protein is a mono-zinc metalloexopeptidase and hydrolyses dipeptides from the N-termini of substrates that consist of at least