Recent advances in the application of isoindigo derivatives in materials chemistry

• Andrei V. Bogdanov and
• Vladimir F. Mironov

Beilstein J. Org. Chem. 2021, 17, 1533–1564, doi:10.3762/bjoc.17.111

• more attention of many research groups. In addition, the ease of modification, such as at the endocyclic nitrogen atom as aromatic fragment of isoindigo, makes it possible to fine-tune the electronic properties. These factors led to the beginning of many studies on isoindigo as a platform for the

• researchers in semiconductor materials has covered the field of organic electronics. The advantages of organic oligomeric and polymeric materials for applications in OFET and thin-film transistor (TFT) technologies are due to the ease of their directed chemical modification, mechanical flexibility, the

• a promising platform for creating materials for various purposes – from organic solar cells and transistors to materials for biomedical applications. The possibility of easy modification and easy accessibility of the starting reagents for the synthesis of polysubstituted isoindigo derivatives

Iodine-catalyzed electrophilic substitution of indoles: Synthesis of (un)symmetrical diindolylmethanes with a quaternary carbon center

• Thanigaimalai Pillaiyar,
• Masoud Sedaghati,
• Andhika B. Mahardhika,
• Lukas L. Wendt and
• Christa E. Müller

Beilstein J. Org. Chem. 2021, 17, 1464–1475, doi:10.3762/bjoc.17.102

• reaction with differently substitute indole derivatives 2. Substrate scope of the reaction of 1f–i with trifluoromethyl(indolyl)phenylmethanols 1: modification of the aryl group. Substrate scope of the reaction of 1j–l with trifluoromethyl(indolyl)phenylmethanols 1: modification of the trifluoromethyl

Total synthesis of ent-pavettamine

• Memory Zimuwandeyi,
• Manuel A. Fernandes,
• Amanda L. Rousseau and
• Moira L. Bode

Beilstein J. Org. Chem. 2021, 17, 1440–1446, doi:10.3762/bjoc.17.99

• developing a route for the synthesis of enantiomer 2 by modification of the established protocol used for the synthesis of 1. The plan was that the alternative strategy would lead to an improvement in the overall yield whilst eliminating some of the troublesome steps. Results and Discussion The synthetic

Fritsch–Buttenberg–Wiechell rearrangement of magnesium alkylidene carbenoids leading to the formation of alkynes

• Tsutomu Kimura,
• Koto Sekiguchi,
• Akane Ando and
• Aki Imafuji

Beilstein J. Org. Chem. 2021, 17, 1352–1359, doi:10.3762/bjoc.17.94

• homologation [3]. Much effort has been devoted to developing a procedure for the synthesis of alkynes from carbonyl compounds, and the Corey–Fuchs method, the Seyferth–Gilbert method, and the Ohira–Bestmann modification have been developed (Scheme 1) [4][5][6][7]. These methods consist of the Wittig or Horner

Icilio Guareschi and his amazing “1897 reaction”

• Gian Cesare Tron,
• Alberto Minassi,
• Giovanni Sorba,
• Mara Fausone and
• Giovanni Appendino

Beilstein J. Org. Chem. 2021, 17, 1335–1351, doi:10.3762/bjoc.17.93

• Guareschi imides, which, under the original protocol, is limited to ketones as the carbonyl component. When aldehydes are used, the adduct is aromatized to the corresponding 2-hydroxypyridone [50][51]. Finally, a modification of the type-IV Guareschi reaction that involves the condensation of two moles of

• cyanoacetamide (and not a cyanoacetic ester) with a carbonyl derivative (aldehyde or ketone) was further investigated by the British chemist Jocelyn Fred Thorpe (1872–1940), a decade after the original studies by Guareschi [52]. In Thorpe’s modification, the reaction takes place in the presence of a secondary

• amine, affording a 6-aminopyridone, which, after acidic treatment, is turned into the same β,β-disubstituted glutarate formed by hydrolysis of the pyridone from the type-IV Guareschi reaction. This modification of the type-IV Guareschi reaction is the “real” Guareschi–Thorpe reaction, which in many

Photoinduced post-modification of graphitic carbon nitride-embedded hydrogels: synthesis of 'hydrophobic hydrogels' and pore substructuring

• Cansu Esen and
• Baris Kumru

Beilstein J. Org. Chem. 2021, 17, 1323–1334, doi:10.3762/bjoc.17.92

• . Post-modifications of hydrogels propose an attractive platform so that a variety of fresh functions, which are not arising from initial monomers, could be accessible on a parental network. Photoinduced post-modification of hydrogels by embedding semiconductor nanosheets would be of high interest and

• manufacture functional soft materials will be of high interest in near future by the means of catalysis and agricultural delivery. Keywords: hydrophobic hydrogel; photoactive hydrogels; photomodification; pore modification; soft materials; Introduction Popularity of hydrogels arises from their structural

• -based applications [40][41]. Hydrogel post-modification via semiconductors induced by visible light would be an appealing haven. Herein, we demonstrate the photoactive g-CN nanosheet addition to hydrogels through embedding, which will be the anchoring point that grants an access to photoinduced post

A comprehensive review of flow chemistry techniques tailored to the flavours and fragrances industries

• Guido Gambacorta,
• James S. Sharley and
• Ian R. Baxendale

Beilstein J. Org. Chem. 2021, 17, 1181–1312, doi:10.3762/bjoc.17.90

Heterogeneous photocatalytic cyanomethylarylation of alkenes with acetonitrile: synthesis of diverse nitrogenous heterocyclic compounds

• Guanglong Pan,
• Qian Yang,
• Wentao Wang,
• Yurong Tang and
• Yunfei Cai

Beilstein J. Org. Chem. 2021, 17, 1171–1180, doi:10.3762/bjoc.17.89

• ), cyano (8h), and carbonyl (8i and 8j) substituted products with 70–82% yield, which provide opportunities for further modification. The ortho-substituted substrate 7k gave the corresponding product 8k in a comparable yield (69%). Also the substrate bearing a meta-substituent exhibited good reactivity

Recent advances in palladium-catalysed asymmetric 1,4–additions of arylboronic acids to conjugated enones and chromones

• Jan Bartáček,
• Jan Svoboda,
• Martin Kocúrik,
• Jaroslav Pochobradský,
• Alexander Čegan,
• Miloš Sedlák and
• Jiří Váňa

Beilstein J. Org. Chem. 2021, 17, 1048–1085, doi:10.3762/bjoc.17.84

• simple modification (temperature, catalyst loading) combined with the iterative addition of boronic acids (1 equiv immediately and 1 equiv after 3 hours) [49]. Following Stoltz's works [11][27][47][48][49][51][52], Stanley et al. published the first example for the formation of all-carbon quaternary

Prins cyclization-mediated stereoselective synthesis of tetrahydropyrans and dihydropyrans: an inspection of twenty years

• Asha Budakoti,
• Pradip Kumar Mondal,
• Prachi Verma and
• Jagadish Khamrai

Beilstein J. Org. Chem. 2021, 17, 932–963, doi:10.3762/bjoc.17.77

• selectivity and good to excellent yield [37]. The experimental modification under segment coupling gave entirely the 4-axial product. For example, treatment of 47 with SnBr4 produced axial and equatorial products 48a and 48b in a 9:79 ratio under typical segment coupling. This selectivity was further improved

• racemization through 2-oxonia-Cope allyl transfer. Partial racemization by reversible 2-oxonia-Cope rearrangement. Rychnovsky modification of the Prins cyclization. Synthesis of (−)-centrolobine and the C22–C26 unit of phorboxazole A. Axially selective Prins cyclization by Rychnovsky et al. Mechanism for the

Beyond ribose and phosphate: Selected nucleic acid modifications for structure–function investigations and therapeutic applications

• Christopher Liczner,
• Kieran Duke,
• Gabrielle Juneau,
• Martin Egli and
• Christopher J. Wilds

Beilstein J. Org. Chem. 2021, 17, 908–931, doi:10.3762/bjoc.17.76

• https://iimcb.genesilico.pl/modomics/ [2]. In DNA, base modifications are much more common than those in the backbone and play a central role in epigenetics, such as, for example, the ‘fifth base’ 5-methylcytosine (5mC) [3]. In the backbone, chemical modification appears to be limited to the

• backbone modification occurs in ribosomal RNA (rRNA) of both pro- and eukaryotes [6]. A very common natural modification that concerns the ribose moiety is 2'-O-methylation (2'-OMe). 2'-OMe nucleotides are scattered throughout all types of RNA, including mRNA, tRNA, rRNA, snRNA, snoRNA, miRNA and viral RNA

• [7][8][9]. Moreover, the modification occurs irrespective of the nature of the base and is therefore also referred to as Nm (N = A, C, G, 5mU, U, ψU, I, etc.) [10]. The specific role(s) an individual modification plays is often not known, but we can surmise involvements in transcription, translation

Synthetic reactions driven by electron-donor–acceptor (EDA) complexes

• Zhonglie Yang,
• Yutong Liu,
• Kun Cao,
• Xiaobin Zhang,
• Hezhong Jiang and
• Jiahong Li

Beilstein J. Org. Chem. 2021, 17, 771–799, doi:10.3762/bjoc.17.67

• synthesis of unnatural α-amino acids 129 and precise alkylation modification of peptides in the later stage (Scheme 45). Even in the presence of other amino acid residues, this protocol has excellent regio- and chemoselectivity, providing a sequence of novel corresponding dipeptides with good yield. The

Synthesis of β-triazolylenones via metal-free desulfonylative alkylation of N-tosyl-1,2,3-triazoles

• Soumyaranjan Pati,
• Renata G. Almeida,
• Eufrânio N. da Silva Júnior and
• Irishi N. N. Namboothiri

Beilstein J. Org. Chem. 2021, 17, 762–770, doi:10.3762/bjoc.17.66

• paved the way for further modification of the protocol (Scheme 1c). Direct functionalization of triazoles is an alternative strategy to access triazoles with the desired substitution pattern. However, such approaches are complicated by a low energy barrier between the N1 and N2 tautomers in solution

DNA with zwitterionic and negatively charged phosphate modifications: Formation of DNA triplexes, duplexes and cell uptake studies

• Yongdong Su,
• Maitsetseg Bayarjargal,
• Tracy K. Hale and
• Vyacheslav V. Filichev

Beilstein J. Org. Chem. 2021, 17, 749–761, doi:10.3762/bjoc.17.65

• provide either a zwitterionic phosphoramidate with N+ modification or a negatively charged phosphoramidate for Ts modification in the DNA sequence. The incorporation of these N+ and Ts modifications led to the formation of thermally stable parallel DNA triplexes, regardless of the number of modifications

• incorporated into the oligodeoxynucleotides (ONs). For both N+ and Ts-modified ONs, the antiparallel duplexes formed with complementary RNA were more stable than those formed with complementary DNA (except for ONs with modification in the middle of the sequence). Additionally, the incorporation of N

• responsible for the stabilisation of duplexes with N+ modification. N+ONs also demonstrated greater resistance to nuclease digestion by snake venom phosphodiesterase I than the corresponding Ts-ONs. Cell uptake studies showed that Ts-ONs can enter the nucleus of mouse fibroblast NIH3T3 cells without any

Simulating the enzymes of ganglioside biosynthesis with Glycologue

• Andrew G. McDonald and
• Gavin P. Davey

Beilstein J. Org. Chem. 2021, 17, 739–748, doi:10.3762/bjoc.17.64

• modification of monosaccharides, for example through sulfation, acetylation or phosphorylation, which follow the same pattern as decoration. Glycologue structure identifiers order branches by linkage position, writing the branch with the lowest linkage first, reading from right to left. Modifiers are written

• will also influence the kinetics [48][51]. Future extensions to this work will consider the effects of acetylation of sialic acid residues, since this modification reduces the negative charge of the carbohydrate, thus altering binding affinity, while an increased incidence of 9-O-acetylated GD3 is

Effective microwave-assisted approach to 1,2,3-triazolobenzodiazepinones via tandem Ugi reaction/catalyst-free intramolecular azide–alkyne cycloaddition

• Maryna O. Mazur,
• Oleksii S. Zhelavskyi,
• Eugene M. Zviagin,
• Svitlana V. Shishkina,
• Vladimir I. Musatov,
• Maksim A. Kolosov,
• Elena H. Shvets,
• Anna Yu. Andryushchenko and
• Valentyn A. Chebanov

Beilstein J. Org. Chem. 2021, 17, 678–687, doi:10.3762/bjoc.17.57

• cycloaddition approach to the synthesis of 1,2,3-triazolobenzodiazepinones. Results and Discussion The development of the tandem Ugi/Click reaction approach for 1,2,3-triazolobenzodiazepinone synthesis can be logically divided into two principal parts: modification and performing synthesis of Ugi-reaction

Synthesis, structural characterization, and optical properties of benzo[f]naphtho[2,3-b]phosphoindoles

• Mio Matsumura,
• Takahiro Teramoto,
• Masato Kawakubo,
• Masatoshi Kawahata,
• Yuki Murata,
• Kentaro Yamaguchi,
• Masanobu Uchiyama and
• Shuji Yasuike

Beilstein J. Org. Chem. 2021, 17, 671–677, doi:10.3762/bjoc.17.56

• ] with n-butyllithium in dry THF at −78 °C and subsequently with dichlorophenylphosphine resulted in ring closure, affording the desired product containing 6-phenyl-6H-benzo[f]naphtho[2,3-b]phosphoindole (2) in 52% yield via the 3,3′-dilithio-2,2′-binaphthyl intermediate. The chemical modification of the

• approximately 50 nm longer than that of our oxide 3 [16]. The fluorescence wavelength, including the maximum emission (λem), and the quantum yield depend on the nature of the P-modification. Phosphine oxide 3, cation 5, and boron complex 6 emitted blue fluorescence in the visible-light region, with λem at 395

• Information File 1. Parent compound 2 and borane complex 6 showed reversible reduction peaks (Ered = −1.25 and −1.26 V, respectively). Due to the increased electron–acceptor character of the phosphorus center, P-modification compounds 4 and 5 show a more positive oxidation potential than parent 2 [26

[2 + 1] Cycloaddition reactions of fullerene C₆₀ based on diazo compounds

• Yuliya N. Biglova

Beilstein J. Org. Chem. 2021, 17, 630–670, doi:10.3762/bjoc.17.55

• universe), the discovery in 1985 of its new allotropic modification, fullerene, has resulted in an avalanche-like expansion of studies in this area [1]. The exceptional physicochemical properties of the fullerene family and, above all, its main representative, C60, predetermine the broad practical interest

Synthesis and properties of oligonucleotides modified with an N-methylguanidine-bridged nucleic acid (GuNA[Me]) bearing adenine, guanine, or 5-methylcytosine nucleobases

• Naohiro Horie,
• Takao Yamaguchi,
• Shinji Kumagai and
• Satoshi Obika

Beilstein J. Org. Chem. 2021, 17, 622–629, doi:10.3762/bjoc.17.54

• data indicate that GuNA[Me] could be a useful modification for therapeutic antisense oligonucleotides. Keywords: artificial nucleic acid; duplex-forming ability; oligonucleotide synthesis; Introduction The efficacy and safety of therapeutic oligonucleotides can be controlled by chemical modifications

• ]. The modification of oligonucleotides with GuNA[H]-T improved the nuclease resistance, cell membrane permeability, and binding affinity toward complementary single-stranded DNAs (ssDNAs) and RNAs (ssRNAs). We also synthesized and evaluated a GuNA[H]-T analog bearing a methyl group in the guanidine

• spectra of ON2/ssRNA and ON2/ssDNA were found to be similar to those of the ON7/ssRNA and ON7/ssDNA duplexes, demonstrating that one modification with GuNA[Me] does not affect the whole duplex structures. Similar results were observed for ON4/ssRNA and ON4/ssDNA (Figure S15 in Supporting Information File

Valorisation of plastic waste via metal-catalysed depolymerisation

• Francesca Liguori,
• Carmen Moreno-Marrodán and
• Pierluigi Barbaro

Beilstein J. Org. Chem. 2021, 17, 589–621, doi:10.3762/bjoc.17.53

• to the action of chemical (acids, air, halogens, solvents) or physical agents (heat, light). For polymers, the properties involved are, for instance, tensile strength, colour or shape, the change of which is usually associated with a modification of the chemical composition (e.g., as a consequence of

Synthesis of N-perfluoroalkyl-3,4-disubstituted pyrroles by rhodium-catalyzed transannulation of N-fluoroalkyl-1,2,3-triazoles with terminal alkynes

• Olga Bakhanovich,
• Viktor Khutorianskyi,
• Vladimir Motornov and
• Petr Beier

Beilstein J. Org. Chem. 2021, 17, 504–510, doi:10.3762/bjoc.17.44

• , agrochemicals, and functional materials (polymers, dyes, films, etc.) (Figure 1) [1][2][3][4]. Numerous methods exist for pyrrole synthesis, including the classical and industrially important condensation approaches, such as the Hantzsch, Huisgen, and Paal–Knorr processes [5]. However, the direct modification

Deoxygenative C2-heteroarylation of quinoline N-oxides: facile access to α-triazolylquinolines

• Geetanjali S. Sontakke,
• Rahul K. Shukla and
• Chandra M. R. Volla

Beilstein J. Org. Chem. 2021, 17, 485–493, doi:10.3762/bjoc.17.42

• simplicity of the developed protocol. The current transformation was also found to be compatible for the late-stage modification of natural products. Keywords: amination; heteroarylation; quinoline N-oxides; regioselective; triazoles; Introduction Quinoline is a key heterocyclic moiety found in many

• transformation for late-stage modification of complex natural products was explored, and as shown in Scheme 4, the protocol was tested with various natural-product-derived triazoles. Novel C2-triazolyl products 4a–c were synthesized in good yield of 61–70% from triazoles derived from thymol, cholesterol and

• scaffolds. The late-stage modification of natural products is the salient feature of this current transformation. Experimental General procedure for the C2-selective synthesis of α-triazolylquinolines 3 To an oven-dried reaction tube equipped with a magnetic stirring bar were added quinoline N-oxide (1a, 29

Synthetic strategies of phosphonodepsipeptides

• Jiaxi Xu

Beilstein J. Org. Chem. 2021, 17, 461–484, doi:10.3762/bjoc.17.41

• ester 87 was then coupled with dibenzyl (S)-2-hydroxypentanedioate (88) using BOP as the activating agent to generate the γ-phosphonodepsidipeptide 89. After hydrazinolysis, acylation with arenecarbonyl chlorides or arenecarboxylic acids, and further modification, the γ-phosphonodepsidipeptide

• are derivatives of the new antimalarial drug fosmidomycin and inhibited the 1-deoxy-ᴅ-xylulose 5-phosphate reductoisomerase. The phosphonodepsipeptides 194 were synthesized as prodrugs with an increased activity after oral administration due to a chemical modification of the phosphonate moiety. For

¹⁹F NMR as a tool in chemical biology

• Diana Gimenez,
• Aoife Phelan,
• Cormac D. Murphy and
• Steven L. Cobb

Beilstein J. Org. Chem. 2021, 17, 293–318, doi:10.3762/bjoc.17.28

• receptor (β2AR) [29]. In this work conjugation of the CF3 group to an aromatic ring was shown to give rise to substantially improved 19F NMR chemical shift sensitivities over the more traditional thiol-specific trifluoromethyl tags (Figure 3b) [28]. In addition to chemical modification, novel methodologies

• are being investigated that enable the enzymatic post-translational modification of non-nucleophilic residues, such as glutamate [31]. As recently demonstrated by Kojima and co-workers, recombinant protein transglutaminase (TGase) could be used to catalyse the chemical replacement of the γ

• combined with the aforementioned chemical approaches based on cysteine and lysine modification. It is worth noting that for small proteins and peptides the chemical incorporation of the desired fluorinated amino acids using SPPS protocols still remains the method of choice, as it enables the site-specific

The preparation and properties of 1,1-difluorocyclopropane derivatives

• Kymbat S. Adekenova,
• Peter B. Wyatt and
• Sergazy M. Adekenov

Beilstein J. Org. Chem. 2021, 17, 245–272, doi:10.3762/bjoc.17.25

• addition, another modification was made in order to increase the speed of the reaction of sodium halodifluoroacetate and alkenes. This was achieved by the use of microwave irradiation in THF solution, which allowed the reactions to be completed within 5 minutes [31]. An application of this method to