Using the phospha-Michael reaction for making phosphonium phenolate zwitterions

• Matthias R. Steiner,
• Max Schmallegger,
• Larissa Donner,
• Johann A. Hlina,
• Christoph Marschner,
• Judith Baumgartner and
• Christian Slugovc

Beilstein J. Org. Chem. 2024, 20, 41–51, doi:10.3762/bjoc.20.6

• primary adduct A (see Scheme 2) is too short-lived that an intramolecular hydrogen transfer toward 2a (C, in Scheme 2) is occurring [48]. Instead, in case of acrylonitrile another hydrogen bond donor, which is the solvent methanol [49], is necessary to trap intermediate A forming the ion pair D. Finally

• intramolecular proton transfer and the methanol-mediated proton transfer, can occur. It has been described that intermediate B is more stable with enolizable electron-withdrawing groups such as esters [50] when compared to, e.g., a nitrile [49]. Accordingly, the intermolecular proton transfer pathway should be

• more accessible with methyl acrylate than with acrylonitrile. The lower reactivity of acrylamide in chloroform compared to methyl acrylate is in accordance with its lower electrophilicity. The observed rate reduction in methanol suggests the importance of the intramolecular hydrogen transfer pathway

Synthesis of N-acyl carbazoles, phenoxazines and acridines from cyclic diaryliodonium salts

• Nils Clamor,
• Mattis Damrath,
• Thomas J. Kuczmera,
• Daniel Duvinage and
• Boris J. Nachtsheim

Beilstein J. Org. Chem. 2024, 20, 12–16, doi:10.3762/bjoc.20.2

• efficient method to synthesize N-acyl carbazoles from readily available iodolium salt and amides via a ring-opening/intramolecular coupling cascade (Scheme 1c) [20][21][22][23][24][25][26][27][28][29][30]. Our group recently explored principle synthetic pathways of hetero- and carbocyclic 5- and 6-membered

Aromatic systems with two and three pyridine-2,6-dicarbazolyl-3,5-dicarbonitrile fragments as electron-transporting organic semiconductors exhibiting long-lived emissions

• Karolis Leitonas,
• Brigita Vigante,
• Dmytro Volyniuk,
• Audrius Bucinskas,
• Pavels Dimitrijevs,
• Sindija Lapcinska,
• Pavel Arsenyan and
• Juozas Vidas Grazulevicius

Beilstein J. Org. Chem. 2023, 19, 1867–1880, doi:10.3762/bjoc.19.139

• -dicarbazolyl-3,5-dicarbonitrile. The compounds are synthesized by Sonogashira coupling reactions and characterized by steady-state and time-resolved luminescence spectroscopy. The compounds show efficient intramolecular charge transfer (ICT) from the donor to the acceptor. The photoluminescence (PL) spectra of

• compounds. In general, polyaromatic π-systems with pyridine-3,5-dicarbonitrile fragments demonstrate promising potential for use in organic electronic devices, such as OLEDs. Keywords: charge transport; intramolecular charge transfer; photophysical properties; pyridine-3,5-dicarbonitrile; Introduction The

• peaks of these low-energy absorption bands are collected in Table 1. A similar band was previously observed for REF [5]. On the basis of the results of the theoretical investigations, the low-energy absorption band of REF has been attributed to the intramolecular charge transfer (ICT) caused by electron

Controlling the reactivity of La@C₈₂ by reduction: reaction of the La@C₈₂ anion with alkyl halide with high regioselectivity

• Yutaka Maeda,
• Saeka Akita,
• Mitsuaki Suzuki,
• Michio Yamada,
• Takeshi Akasaka,
• Kaoru Kobayashi and
• Shigeru Nagase

Beilstein J. Org. Chem. 2023, 19, 1858–1866, doi:10.3762/bjoc.19.138

• metal atoms to the fullerene cage. Because of this intramolecular electron transfer, the characteristic properties of metallofullerenes, such as their redox potentials, are significantly different from those of empty fullerenes. For example, La@C82 has paramagnetic properties, and its formal electronic

Thienothiophene-based organic light-emitting diode: synthesis, photophysical properties and application

• Recep Isci and
• Turan Ozturk

Beilstein J. Org. Chem. 2023, 19, 1849–1857, doi:10.3762/bjoc.19.137

• (excitation at λmax), respectively, leading to a mega Stokes shift (>100 nm) of 109 nm, which could be explained to be due to a fast relaxation from the excited state to the ground state as a result of a powerful intramolecular energy transfer between the TPA and boron groups through the thieno[3,2-b

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

• aromatic nitro derivatives 3 and 6 proceeds through the corresponding hydroxylamines, capable of intramolecular cyclization to products 4 or 7. Fortunately, under Zn/AcOH reductive conditions this was resolved by extending the duration of the reaction to 18–24 h, providing enough time for compounds 4/7 to

Active-metal template clipping synthesis of novel [2]rotaxanes

• Cătălin C. Anghel,
• Teodor A. Cucuiet,
• Niculina D. Hădade and
• Ion Grosu

Beilstein J. Org. Chem. 2023, 19, 1776–1784, doi:10.3762/bjoc.19.130

• ]rotaxanes using both a [1 + 1] macrocyclization clipping reaction to obtain R1 and an intramolecular macrocyclization to access R2 (Scheme 2). In both cases formation of the [2]rotaxanes was observed by HRESI(+)-MS (Figure 3, top). Thus, the HRESI(+)-MS spectrum of R1 showed two characteristic peaks at m/z

• Information File 1). However, only [2]rotaxane R2 could be isolated as pure compound in 3% yield, after several purification operations by column chromatography. The improved results obtained in the intramolecular macrocyclization for the clipping reaction as compared to the [1 + 1] strategy are in line with

• active-metal template and clipping methods to yield the target interlocked molecules via [1 + 1] or intramolecular macrocyclizations, realized through CuAAC reactions catalyzed by axle-copper(I) N-heterocyclic carbene complexes. The [2]rotaxane obtained by [1 + 1] clipping (R1) could be only observed by

Effects of the aldehyde-derived ring substituent on the properties of two new bioinspired trimethoxybenzoylhydrazones: methyl vs nitro groups

• Dayanne Martins,
• Roberta Lamosa,
• Talis Uelisson da Silva,
• Carolina B. P. Ligiero,
• Sérgio de Paula Machado,
• Daphne S. Cukierman and
• Nicolás A. Rey

Beilstein J. Org. Chem. 2023, 19, 1713–1727, doi:10.3762/bjoc.19.125

• liquors and, in both cases, XRD confirmed the obtention of the (E)-isomer, in an anti-conformation. Computational calculations (gas and water phases) were performed in order to confirm some of the structural and vibrational aspects of the compounds. An important intramolecular H bond involving the

• different space groups. The methyl-containing hdz-CH3 crystallized in the monoclinic system, C2/c space group, while the nitro derivative hdz-NO2 belongs to the group, from the triclinic system. In both cases, a moderate to strong intramolecular H-bond involving the phenol oxygen O1 as H-donor and the

• -withdrawing nitro substituent in hdz-NO2 makes the intramolecular H-bond stronger. Regarding lattice organization, both structures exhibit stacked motifs. In hdz-CH3, the planes were organized by C–H···O non-conventional H-bonds comprising the methoxy groups (Figure 2B). In the columns, there are

Quinoxaline derivatives as attractive electron-transporting materials

• Zeeshan Abid,
• Liaqat Ali,
• Sughra Gulzar,
• Faiza Wahad,
• Raja Shahid Ashraf and
• Christian B. Nielsen

Beilstein J. Org. Chem. 2023, 19, 1694–1712, doi:10.3762/bjoc.19.124

• compounds exhibited good coplanarity through intramolecular interactions, narrow bandgaps, broad absorption in the NIR region and PCEs above 10% [32]. Ayub et al. decorated the central donor–acceptor–donor unit of Qx17 and Qx18 with five new terminal end groups, resulting in the Qx19 series, and predicted

Decarboxylative 1,3-dipolar cycloaddition of amino acids for the synthesis of heterocyclic compounds

• Xiaofeng Zhang,
• Xiaoming Ma and
• Wei Zhang

Beilstein J. Org. Chem. 2023, 19, 1677–1693, doi:10.3762/bjoc.19.123

• -aminoisobutyric acid, phenylglycine and valine with Ph or iPr groups could also be used for the synthesis of the monocycloaddition products for the post-condensation reactions. It is worth noting that in the one-pot synthesis involving an intramolecular click reaction, no Cu catalyst was used. A similar reaction

A deep-red fluorophore based on naphthothiadiazole as emitter with hybridized local and charge transfer and ambipolar transporting properties for electroluminescent devices

• Suangsiri Arunlimsawat,
• Patteera Funchien,
• Pongsakorn Chasing,
• Atthapon Saenubol,
• Taweesak Sudyoadsuk and
• Vinich Promarak

Beilstein J. Org. Chem. 2023, 19, 1664–1676, doi:10.3762/bjoc.19.122

• charge-transport properties, which could be done by selecting different D and A moieties [22][26][27][28]. In these fluorophores, the emission generally derives from intramolecular charge-transfer (CT) states at lower energy. Nonetheless, the formed CT state between D and A in such materials normally

• intramolecular charge-transfer (ICT) transition from carbazole donor to Nz acceptor, respectively. Such weak ICT absorption peak (ε = 17,000 M−1 cm−1) as compared to the π–π* absorption peak (ε = 95,300 M−1 cm−1) symbolizes a weak electronic coupling between the carbazole donor and the Nz acceptor parts because

• that both TPECNz is an AIE-active fluorophore, however, the AIE effect in TPECNz might not be as strong as for the standard AIE molecules, whose emissions are completely quenched in solutions and brightened by aggregate formation, as a result of the restriction of intramolecular motions (RIM) caused by

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

• binding different alkali and transition metal cations with intramolecular photoinduced electron transfer [48][80]. Further applications of crown ether-appended porphyrins acting as multitopic receptors, catalytically active species, and ligands were also investigated [81][82][83][84][85][86][87][88][89

• ether systems, where the catechol unit of the crown ether was fused to two β-pyrrolic positions of the porphyrin periphery. The systems presented intriguing intramolecular electron-transfer properties. Additionally, they were investigated as fluorescent sensors for various organic and metal cations [51

• planar to an octahedral. The water molecule and the hydroxide anion occupied ligand positions on both sides of the median central-core plane, hydrogen bonding to the flexible crown ether part of 16 (Scheme 6). The intramolecular flexibility of compound 16 allowed for tightening/loosening of the cleft

Synthesis of 7-azabicyclo[4.3.1]decane ring systems from tricarbonyl(tropone)iron via intramolecular Heck reactions

• Aaron H. Shoemaker,
• Elizabeth A. Foker,
• Elena P. Uttaro,
• Sarah K. Beitel and
• Daniel R. Griffith

Beilstein J. Org. Chem. 2023, 19, 1615–1619, doi:10.3762/bjoc.19.118

• accessed from tropone (via its η4-diene complex with Fe(CO)3) in a short sequence of steps: 1) nucleophilic amine addition and subsequent Boc-protection, 2) photochemical demetallation of the iron complex, and 3) an intramolecular Heck reaction. Minor modifications to the protocol enabled access to the

• ervitsine [10][11] (Figure 1). We reasoned that, with an appropriately functionalized amine side chain and properly disposed unsaturation on the seven-membered ring, an intramolecular Heck reaction could give rise to skeleton 4 in just a few steps from tricarbonyl(tropone)iron (Scheme 1). Herein, we report

• the same substitution pattern as substrate 7 tend to give poor yields in similar intramolecular Heck reactions [20]. Moreover, it was found that substrates on which the halide is cis to an additional methyl substituent (used to forge the ethylidene-substituted polycycle common to many alkaloids) often

C–H bond functionalization: recent discoveries and future directions

• Indranil Chatterjee

Beilstein J. Org. Chem. 2023, 19, 1568–1569, doi:10.3762/bjoc.19.114

• the abstraction of intramolecular hydrogen atoms. Radical chemistry is a viable alternative to the two-electron process, involving C–H bond functionalization in the absence of any ligand and using low-cost redox-active metals (Fe, Cu, Mn, etc.) rather than heavy metals (Rh, Ir, etc.). Although radical

Complexes of resorcin[4]arene with secondary amines: synthesis, solvent influence on “in-out” structure, and theoretical calculations of non-covalent interactions

• Waldemar Iwanek

Beilstein J. Org. Chem. 2023, 19, 1525–1536, doi:10.3762/bjoc.19.109

• hydrogen bond between the oxygen anion of the hydroxy group (which also forms a hydrogen bond with the amine molecule) and the adjacent hydroxy group in DMSO in the R[4]A (1.505 Å) molecule than the remaining intramolecular hydrogen bonds. In CHCl3, both the type and length of the hydrogen bond undergo

• a slight change in its conformation towards the boat conformation. The length of the hydrogen bond between the oxygen atom of the hydroxy group forming the hydrogen bond with pyrrolidine and the adjacent hydroxy group is 1.746 Å and is only slightly shorter than the other intramolecular hydrogen

• (PBE0-D4/def2-mTZVPP/CPCM(DMSO) structures of these complexes. The lengths of intermolecular hydrogen bonds between R[4]A and amines are marked in green, while the intramolecular hydrogen bonds between the oxygen anion and the hydrogen atom of the adjacent hydroxy group in R[4]A are marked in violet

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

• succeeded in synthesizing various diaryl(alkyl) sulfides 5 through the sulfenylation of unactivated arenes 4 with an electrophilic sulfur reagent in the presence of a palladium catalyst (Scheme 3) [45]. In the second phase, dibenzothiophene derivatives 6 were obtained via subsequent intramolecular arylation

• . Intramolecular nucleophilic addition of the phenoxy ring of 12 to the activated C–C triple bond afforded intermediate III, followed by deprotonation to deliver product 13 (Scheme 9). When substrate 12 had an OMe group on the phenoxy ring, ipso sulfenylcyclization, or sulfenylation of the phenoxy ring occurred

• of organic compounds, N-(alkyl/arylthio)phthalimides are also considered good candidates for this purpose. In 2017, Sahoo and co-workers established a method for intramolecular annulation of N-(arylthio)phthalimides 14 and N-(arylthio)succinimides 1 with alkynes 15 in the presence of AlCl3 as an

Cyclization of 1-aryl-4,4,4-trichlorobut-2-en-1-ones into 3-trichloromethylindan-1-ones in triflic acid

• Vladislav A. Sokolov,
• Andrei A. Golushko,
• Irina A. Boyarskaya and
• Aleksander V. Vasilyev

Beilstein J. Org. Chem. 2023, 19, 1460–1470, doi:10.3762/bjoc.19.105

• -enones) undergo intramolecular transformation into 3-trichloromethylindan-1-ones (CCl3-indanones) in Brønsted superacid CF3SO3H (triflic acid, TfOH) at 80 °C within 2–10 h in yields up to 92%. Protonation of the carbonyl oxygen of the starting CCl3-enones by TfOH affords the key reactive intermediates

• calculations, and to study their intramolecular cyclization in triflic acid into the synthetically and medicinally relevant (see recent reviews [12][13][14][15][16][17][18]) indan-1-ones. Results and Discussion The synthesis of 1-aryl-4,4,4-trichloro-3-hydroxybutan-1-ones (CCl3-hydroxy ketones) 1a–o was

• electron-donating substituents in the aromatic ring gave oligomeric materials. Presumably, in these cases, after dehydration and formation of the corresponding enone 2, the latter underwent subsequent cationic oligomerization. Next we studied the intramolecular cyclization of compounds 1 and 2 in TfOH. It

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

• wherein the intermediate enoxyl radical II arising from the addition step evolves via intramolecular addition to tethered alkenes [16][17] or alkynes [18]. We wondered if, in the absence of the pending radical acceptor, the presence of the β-nitrogen atom could nevertheless promote zinc enolate formation

Non-noble metal-catalyzed cross-dehydrogenation coupling (CDC) involving ether α-C(sp³)–H to construct C–C bonds

• Hui Yu and
• Feng Xu

Beilstein J. Org. Chem. 2023, 19, 1259–1288, doi:10.3762/bjoc.19.94

• copper is to activate the 1,3-dicarbonyl compounds through complexation that leads to a highly diastereoselective nucleophilic addition. Scheidt et al. reported an enantioselective Cu-catalyzed intramolecular cross-dehydrogenative coupling approach to substituted tetrahydropyrans with excellent yields

Acetaldehyde in the Enders triple cascade reaction via acetaldehyde dimethyl acetal

• Alessandro Brusa,
• Debora Iapadre,
• Maria Edith Casacchia,
• Alessio Carioscia,
• Giuliana Giorgianni,
• Giandomenico Magagnano,
• Fabio Pesciaioli and
• Armando Carlone

Beilstein J. Org. Chem. 2023, 19, 1243–1250, doi:10.3762/bjoc.19.92

• last step involves the enamine intermediate which drives an intramolecular aldol condensation to form the final product 5. In this elegant cascade process, catalyst 1 promotes three consecutive carbon–carbon bond forming steps generating four stereogenic centers with high diastereoselectivity and

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

• beginning of the reaction, copper(II) 2,3-diamino-5,10,15,20-tetraarylporphyrins 1 react with 2-hydroxynaphthalene-1,4-dione (2) in the presence of trichloroacetic acid to form an imine intermediate which on intramolecular cyclization affords a key benzo[f]quinoxalinoporphyrin intermediate 17. Further, a

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

• include nucleophile σ-hole selectivity, and how ylide structural modifications and intramolecular halogen bonding (e.g., the ortho-effect) can improve ylide stability or solubility, and alter reaction outcomes. Keywords: electron donor–acceptor complex; halogen bonding; σ-holes; iodonium ylides; ortho

• resulting in two different ligand coupling outcomes. While most of their reactions expel an iodoarene to produce functionalized β-dicarbonyl motifs, ligand coupling with the arene motif is also possible, such as in the (radio)fluorination of iodonium ylides. Finally, intramolecular σ-hole bonding offers the

• -hole bond is the non-covalent inter- or intramolecular interaction between the σ-hole of a group IV–VII atom with the electron-rich site of Lewis bases such as anions, hydrides, or even π electrons [24][30]. Halogen bonding is a subset of this bonding classification, represented by the generic bonding

Photoredox catalysis harvesting multiple photon or electrochemical energies

• Mattia Lepori,
• Simon Schmid and
• Joshua P. Barham

Beilstein J. Org. Chem. 2023, 19, 1055–1145, doi:10.3762/bjoc.19.81

• -BF4 as a suitable conPET catalyst. Following the conPET catalytic cycle, the Mes-Acr+ cation is excited and reductively quenched by DIPEA to yield the acridine radical Mes-Acr• (Figure 10C) [54]. Upon excitation to its twisted intramolecular charge-transfer (TICT) state, Mes-Acr• has an excited-state

• ][63][64]. Arylphosphonates 15 were obtained in a photo-Arbuzov reaction by trapping with trimethylphosphite in good to excellent yields (62–88%) (Figure 12B). Additionally, intramolecular trapping via dearomative hydroarylation gave access to spirocyclic cyclohexadienes bearing dihydrobenzofuran and

• excited state lifetimes [95][96], most reactions employing such photocatalysts require special reaction design (e.g., coordination of substrates as ligands to enable intramolecular metal to ligand charge transfer (MLCT)). Only recently have a few examples been reported that observed bimolecular quenching

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

• N atom of the PTZ unit [59][60]. Further, the NI-PTZ-F-O and NI-PTZ-Ph-O compounds adopt an orthogonal geometry, and the N atom in the PTZ unit is not in π-conjugation with NI moiety due to a conformational restriction [55]. Thus, it is not the ordinary intramolecular charge transfer (ICT) state

Synthesis of tetrahydrofuro[3,2-c]pyridines via Pictet–Spengler reaction

• Elena Y. Mendogralo and
• Maxim G. Uchuskin

Beilstein J. Org. Chem. 2023, 19, 991–997, doi:10.3762/bjoc.19.74

• the use of 3-substituted furans. For example, the intramolecular Friedel–Crafts alkylation reaction (Scheme 1a) of alcohols [9][10][11], alkenes [12] or acetylenes [13] affords the desired tetrahydrofuro[3,2-c]pyridines. A related method is based on a Au(I)-catalyzed domino sequence dearomatization

• /ipso-cyclization/Michael-type Friedel–Crafts alkylation (Scheme 1b) [14][15][16]. Unfortunately, approaches including the intramolecular alkylation of 3-substituted furans are underinvestigated as these substrates are usually hard to reach and the resulting benzyl carbocation is often prone to undergo