Towards new NIR dyes for free radical photopolymerization processes

• Haifaa Mokbel,
• Guillaume Noirbent,
• Didier Gigmes,
• Frédéric Dumur and
• Jacques Lalevée

Beilstein J. Org. Chem. 2021, 17, 2067–2076, doi:10.3762/bjoc.17.133

• and safe near-infrared (NIR) light is still the subject of intense research efforts but remains a huge challenge due to the associated low photon energy (wavelength from 0.78 to 2.5 µm). In this study, a series of 17 NIR dyes mainly based on a well-established cyanine scaffold is proposed. Remarkably

• ) to generate initiating radicals. In this work, a large series of 17 NIR dyes mainly based on a well-established cyanine scaffold is proposed (Scheme 1). Markedly, eleven of them were never synthesized before. These NIR dyes are studied in three-component systems in combination with an iodonium salt

• ) λmax = 810 nm for CBPh2 and CI2; iii) λmax = 900 nm for CBPh3 and CI3; and iv) λmax = 780 nm for CBPh4 and CI4. However, the peripheral substituents in the cyanine scaffold play an important role in the absorption properties of some dyes, i.e., for CBPh3, CI3, and CI10 bearing a 1-hexyl-2-methylbenzo

Asymmetric organocatalyzed synthesis of coumarin derivatives

• Natália M. Moreira,
• Lorena S. R. Martelli and
• Arlene G. Corrêa

Beilstein J. Org. Chem. 2021, 17, 1952–1980, doi:10.3762/bjoc.17.128

• long-acting vitamin K antagonist (Figure 1) [8]. This scaffold has also been reported as anti-Alzheimer’s disease [9], such as the natural product decursinol, isolated from Angelica gigas [10]. In this sense, our research group has synthesized and evaluated a library of coumarin derivatives as

• -catalyzed cross-coupling reactions of coumarin derivatives [24]. Coumarins are a promising scaffold for design and development of bioactive agents, however it possesses a flat system [25]. One of the attractive benefits of introducing chirality in a drug candidate is that it leads to increased complexity to

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

• , T12 YN60, Ireland 10.3762/bjoc.17.127 Abstract The indazole scaffold represents a promising pharmacophore, commonly incorporated in a variety of therapeutic drugs. Although indazole-containing drugs are frequently marketed as the corresponding N-alkyl 1H- or 2H-indazole derivative, the efficient

• achieve regioselective indazole N-alkylation have exploited the noted difference in reactivity between the N-1 and N-2 atom of the indazole scaffold [15], as the 1H-indazole tautomer is typically considered to be more thermodynamically stable than the corresponding 2H-tautomer [16]. Using appropriate α

• trend in regioselectivity [24]. Our work sought to further explore the effect of C-3 substitution on N-alkylation selectivity control of the 1H-indazole scaffold. In view of these antecedents, it was envisioned that the development of a regioselective protocol for indazole N-1 alkylation would provide

On the application of 3d metals for C–H activation toward bioactive compounds: The key step for the synthesis of silver bullets

• Renato L. Carvalho,
• Amanda S. de Miranda,
• Mateus P. Nunes,
• Roberto S. Gomes,
• Guilherme A. M. Jardim and
• Eufrânio N. da Silva Júnior

Beilstein J. Org. Chem. 2021, 17, 1849–1938, doi:10.3762/bjoc.17.126

• was then converted to a 5,6-fused seco-prezizaane scaffold through an α-ketol rearrangement promoted by a strong base and after secondary alcohol protection with TBSCl, a Fe-catalyzed C–H activation reaction promoted a second lactonization to afford (+)-pseudoanisatin (Scheme 28B). In 2016, Chirik and

Cationic oligonucleotide derivatives and conjugates: A favorable approach for enhanced DNA and RNA targeting oligonucleotides

• Mathias B. Danielsen and
• Jesper Wengel

Beilstein J. Org. Chem. 2021, 17, 1828–1848, doi:10.3762/bjoc.17.125

• moieties attached to the sugar scaffold The sugar moiety of ONs has been extensively studied with respect to the significance of structure and configurations of substituents, and the resulting conformations of the furanose ring, on the properties of ONs (including ASOs). The great variation at which

• significant improvement in Tm was observed when the functionalizing groups were changed from ethylenediamine to either trimethylenediamine (monomer 42) or putrescine (monomer 43), demonstrating that the length between the cationic amino group and the sugar scaffold is important for the thermal stability

• combinations have been attached to the 2’-amino group with substantial success regarding duplex stability [92]. The 2’-amino-LNA scaffold has further been modified with amine-functionalized groups at the nucleoside level creating different nucleotide building blocks for ON synthesis, or at the ON level via

Sustainable manganese catalysis for late-stage C–H functionalization of bioactive structural motifs

• Jongwoo Son

Beilstein J. Org. Chem. 2021, 17, 1733–1751, doi:10.3762/bjoc.17.122

• [24]. This manganese porphyrin catalytic system was also effective in the direct site-selective fluorination of complex steroid scaffold 3, containing 28 unactivated C–H bonds. Based on the authors’ analysis of steric and electronic factors, it was suggested that the methylene units at C2 and C3 of

• , a natural product scaffold, was transformed into glycosylated tryptophan 31f. It is noteworthy that this manganese(I)-catalyzed glycoconjugation method avoids racemization. Furthermore, manganese-catalyzed allylative linchpin C–H glycosylation was investigated using structurally sophisticated

Chemical approaches to discover the full potential of peptide nucleic acids in biomedical applications

• Nikita Brodyagin,
• Martins Katkevics,
• Venubabu Kotikam,
• Christopher A. Ryan and
• Eriks Rozners

Beilstein J. Org. Chem. 2021, 17, 1641–1688, doi:10.3762/bjoc.17.116

2,4-Bis(arylethynyl)-9-chloro-5,6,7,8-tetrahydroacridines: synthesis and photophysical properties

• Najeh Tka,
• Mohamed Adnene Hadj Ayed,
• Mourad Ben Braiek,
• Mahjoub Jabli,
• Noureddine Chaaben,
• Kamel Alimi,
• Stefan Jopp and
• Peter Langer

Beilstein J. Org. Chem. 2021, 17, 1629–1640, doi:10.3762/bjoc.17.115

• appeared as a side product during the synthesis of anthracene [11] and became an abundant scaffold in medicinal chemistry [12][13][14]. Acridine derivatives have exhibited a range of biological activities [15][16][17][18][19][20] and have been particularly explored in chemotherapeutic protocols against

• ring, is another privileged scaffold which showed interesting biological activities [48][49][50][51][52][53][54]. As a typical example, 9-amino-1,2,3,4-tetrahydroacridine or tacrine was the first drug approved for the treatment of Alzheimer's disease [55][56][57]. Surprisingly, photophysical properties

A recent overview on the synthesis of 1,4,5-trisubstituted 1,2,3-triazoles

• Pezhman Shiri,
• Ali Mohammad Amani and
• Thomas Mayer-Gall

Beilstein J. Org. Chem. 2021, 17, 1600–1628, doi:10.3762/bjoc.17.114

• compounds with not only biological but also industrial significance [9][10][11]. It possesses a cyclic scaffold with carbon and three nitrogen elements in the ring [12][13][14][15]. An immense versatility of biological properties is possessed by 1,2,3‐triazole heterocyclic systems, and many strategies are

• one of the products was proved by NMR analysis and X-ray crystallography. A number of different substituents was introduced to the bromotriazole scaffold, where unsubstituted and electron-rich derivatives gave a good yield, while the presence of electron-withdrawing groups decreased the product yield

• achieved using dehydrogenative intramolecular cyclization of 4-substituted N-benzyltriazoles 163. A phenyl, alkyl, and CO2Me group, respectively, on the triazole scaffold was tolerated under the reaction conditions to form 4-substituted N-benzyltriazoles (Scheme 44). The substituted phenanthro[9,10-d

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

• ][103][104][105]. Thus, two polymers 56 were obtained in which isoindigo fragments are condensed on the indacenedione scaffold [102]. Despite the presence of an extended π-conjugation system, which determines the ambipolar properties of a transistor based on these polymers, the charge mobility values

Breaking paracyclophane: the unexpected formation of non-symmetric disubstituted nitro[2.2]metaparacyclophanes

• Suraj Patel,
• Tyson N. Dais,
• Paul G. Plieger and
• Gareth J. Rowlands

Beilstein J. Org. Chem. 2021, 17, 1518–1526, doi:10.3762/bjoc.17.109

• archetypal cyclophane, with a strong interaction between the two aromatic rings, but it is readily available, being a ‘dimer’ for the polymer parylene [6][7]. Over the last twenty years, there has been a resurgence in interest in this compound as a scaffold for the synthesis of asymmetric catalysts, energy

A straightforward conversion of 1,4-quinones into polycyclic pyrazoles via [3 + 2]-cycloaddition with fluorinated nitrile imines

• Greta Utecht-Jarzyńska,
• Karolina Nagła,
• Grzegorz Mlostoń,
• Heinz Heimgartner,
• Marcin Palusiak and
• Marcin Jasiński

Beilstein J. Org. Chem. 2021, 17, 1509–1517, doi:10.3762/bjoc.17.108

• naphthoquinone-derived products and low-intensity bands in the visible region (≈400 nm) for the anthraquinone series. Keywords: [3 + 2]-cycloadditions; fluorinated compounds; fused pyrazoles; N-heterocycles; nitrile imines; 1,4-quinones; Introduction The 1,4-quinone scaffold belongs to the most important

Co-crystallization of an organic solid and a tetraaryladamantane at room temperature

• Fabian Rami,
• Jan Nowak,
• Felix Krupp,
• Wolfgang Frey and
• Clemens Richert

Beilstein J. Org. Chem. 2021, 17, 1476–1480, doi:10.3762/bjoc.17.103

• and thermodynamic aspects. Kinetically, when crystallizing from a solvent, the solvent may be more likely to be encapsulated than the second solid-forming compound, as the solvent will be smaller and more abundant, making it the more likely molecule to be entrapped in cavities left by the scaffold

Double-headed nucleosides: Synthesis and applications

• Vineet Verma,
• Jyotirmoy Maity,
• Vipin K. Maikhuri,
• Ritika Sharma,
• Himal K. Ganguly and
• Ashok K. Prasad

Beilstein J. Org. Chem. 2021, 17, 1392–1439, doi:10.3762/bjoc.17.98

• complementary DNA strands were studied. The analysis of the melting temperature of the resulting duplex revealed that the synthesized double-headed nucleotide behaved as a compressed dinucleotide and combination of all natural nucleobases on compressed scaffold can form Watson–Crick base pairs with

Design, synthesis and photophysical properties of novel star-shaped truxene-based heterocycles utilizing ring-closing metathesis, Clauson–Kaas, Van Leusen and Ullmann-type reactions as key tools

• Shakeel Alvi and
• Rashid Ali

Beilstein J. Org. Chem. 2021, 17, 1374–1384, doi:10.3762/bjoc.17.96

• , superior solubility, improve morphological, optical, electrical and film-forming properties because of the involvement of extra dimensionality. Amongst them, the heptacyclic truxene scaffold possessing three overlapping fluorene units and its congeners are of archetypal interest due to their potential

• synthetic strategies and also novel truxene-based functional materials with unique properties. Bearing in mind the importance of the truxene framework, herein, we report diverse C3-symmetric heterocyclic systems possessing the truxene scaffold in their structures by means of cyclotrimerization, ring-closing

• -containing five-membered aromatic pyrrole scaffold will continue to play a significant role in the development of novel anionic receptors [33][34]. Therefore, as outlined in Scheme 2, our synthetic strategy towards the construction of the target pyrrole-based truxene derivative 6 initiated with the acid

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

• scaffold [4]. The Guareschi–Lustgarten reaction is at the basis of the pharmacopoeia assay of thymol (3) [5], and investigation on the color associated with the reaction eventually led to the discovery of the Reimer–Tiemann formylation of phenols [6]. Conversely, the third Guareschi eponymic reaction, the

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

Synthetic accesses to biguanide compounds

• Oleksandr Grytsai,
• Cyril Ronco and
• Rachid Benhida

Beilstein J. Org. Chem. 2021, 17, 1001–1040, doi:10.3762/bjoc.17.82

• for their synthesis, work-up, and purification. In this context, the aim of the next part of this review is to propose a generalized and comparative overview of the synthetic methods to access this particular scaffold. We chose to sort the synthetic routes by reaction types, from the most general and

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

• of the THP key scaffold and its application towards the total synthesis of natural products. Many advancements were also taking place in Prins cyclization methodologies over that period of time. This appraisal aims to bring together the work of many research groups in the area of the development of

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

• diseases. Oligonucleotides with alterations to their scaffold, prepared with modified nucleosides and solid-phase synthesis, have yielded molecules with interesting biophysical properties that bind to their targets and are tolerated by the cellular machinery to elicit a therapeutic outcome. Structural

• arguably the most radical alternative nucleic acid pairing system, peptide nucleic acid (PNA), the sugar-phosphate backbone is replaced by an amide-based, neutral and achiral scaffold that allows cross-pairing with both DNA and RNA as well as formation of double- and triple-stranded species [57]. Despite

• [148], and in the use of antisense oligonucleotides for splice modulation through the induction of Dmd exon-23 skipping in mice in vitro [149]. Recently, a lot of attention has been paid to modifying the LNA scaffold to incorporate various heteroatoms, modify the bicyclic framework, and to change the

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

• donor. Furthermore, due to the commercially available material and wide range of substrates, this approach has major significance for drug scaffold methodologies, providing useful strategy for the synthesis of spiropyrrolines. In 2019, Yu and colleagues [23] reported the utilization of

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

• the nuclear DNA, confirmed that the Ts-ON foci are present within the cytoplasm as shown in Figure 4. Discussion Chemical modification provides an effective and efficient way of obtaining therapeutic antigene/antisense agents based on the nucleic acid scaffold. To regulate transcription or translation

β-Lactamase inhibition profile of new amidine-substituted diazabicyclooctanes

• Zafar Iqbal,
• Lijuan Zhai,
• Yuanyu Gao,
• Dong Tang,
• Xueqin Ma,
• Jinbo Ji,
• Jian Sun,
• Jingwen Ji,
• Yuanbai Liu,
• Rui Jiang,
• Yangxiu Mu,
• Lili He,
• Haikang Yang and
• Zhixiang Yang

Beilstein J. Org. Chem. 2021, 17, 711–718, doi:10.3762/bjoc.17.60

• , Jinfeng District, Yinchuan, Ningxia 750002, P.R. China College of Pharmacy, Ningxia Medical University, Shengli Street, Xingqing District, Yinchuan, Ningxia 750004, P.R. China 10.3762/bjoc.17.60 Abstract The diazabicyclooctane (DBO) scaffold is the backbone of non-β-lactam-based second generation β

α,γ-Dioxygenated amides via tandem Brook rearrangement/radical oxygenation reactions and their application to syntheses of γ-lactams

• Mikhail K. Klychnikov,
• Radek Pohl,
• Ivana Císařová and
• Ullrich Jahn

Beilstein J. Org. Chem. 2021, 17, 688–704, doi:10.3762/bjoc.17.58

• γ-lactam scaffold [40][41][42][43][44]. The pyrrolidinone fragment is often synthesized by transition metal- [45][46][47][48][49][50] or Lewis acid-catalyzed cyclization reactions [51][52][53][54]. The Diels–Alder reaction can also be used for the preparation of functionalized γ-lactams in a single

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

• complex scaffold in just two steps. Unusually, the azide–alkyne cycloaddition for both terminal and non-terminal alkynes was effective under catalyst-free conditions while normally for non-terminal alkynes a ruthenium-based catalysis is required. Using the developed method, a library of 22 target