Methodologies for the synthesis of quaternary carbon centers via hydroalkylation of unactivated olefins: twenty years of advances

• Thiago S. Silva and
• Fernando Coelho

Beilstein J. Org. Chem. 2021, 17, 1565–1590, doi:10.3762/bjoc.17.112

• ]. This approach allowed the synthesis of alkylated benzofurans and benzothiophenes (Scheme 27). Investigations of the substrate scope revealed that both electron-donating and electron-withdrawing group substituents at the aromatic portions of the imine substrate could afford the aromatic heterocycle in

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

• significant effect of the structure of the substituent at the nitrogen atom of the heterocycle on the OSC efficiency was also shown [29][30]. Thus, fluorine-substituted polymers 18a,b in the composition with PC61BM showed a PCE of only 0.9–1.4%, while an OSC based on ethoxylated derivative 19a was

One-step synthesis of imidazoles from Asmic (anisylsulfanylmethyl isocyanide)

• Louis G. Mueller,
• Allen Chao,
• Embarek AlWedi and
• Fraser F. Fleming

Beilstein J. Org. Chem. 2021, 17, 1499–1502, doi:10.3762/bjoc.17.106

• a valuable route to mono- and disubstituted imidazoles. Keywords: Asmic; cyclization; imidazoles; isocyanides; nitriles; Introduction The imidazole core is the seventh most prevalent heterocycle among nitrogen-containing pharmaceuticals [1]. The privileged efficacy of imidazoles emanates from the

N-tert-Butanesulfinyl imines in the asymmetric synthesis of nitrogen-containing heterocycles

• Joseane A. Mendes,
• Paulo R. R. Costa,
• Miguel Yus,
• Francisco Foubelo and
• Camilla D. Buarque

Beilstein J. Org. Chem. 2021, 17, 1096–1140, doi:10.3762/bjoc.17.86

• ) to promote the complexation with the Grignard reagent. Products 147 and 149 were obtained in excellent yields and high diastereoselectivity and when 4-methylmorpholine (NMM) was used as additive, the heterocycle 151 was obtained in one pot addition–cyclization–deprotection of imine 150 (Scheme 40

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

• substituent at the arene ring produced predominantly symmetric THP product 26 over the desired trisubstituted heterocycle 23. The mechanism of the reaction was further investigated using enantioenriched homoallylic alcohol (S)-18 with 89% ee, which favored 2-oxonia-Cope rearrangement to give THP 23 only in 14

Menthyl esterification allows chiral resolution for the synthesis of artificial glutamate analogs

• Kenji Morokuma,
• Shuntaro Tsukamoto,
• Kyosuke Mori,
• Kei Miyako,
• Ryuichi Sakai,
• Raku Irie and
• Masato Oikawa

Beilstein J. Org. Chem. 2021, 17, 540–550, doi:10.3762/bjoc.17.48

• crystal are arising from the four contiguous single bonds between the heterocycle and the menthyl group. These take a stable extended conformation in the calculations and in the NMR experiment, whereas a rather folded conformation is taken in the crystals. Such a discrepancy is often observed and reported

CF₃-substituted carbocations: underexploited intermediates with great potential in modern synthetic chemistry

• Anthony J. Fernandes,
• Armen Panossian,
• Bastien Michelet,
• Agnès Martin-Mingot,
• Frédéric R. Leroux and
• Sébastien Thibaudeau

Beilstein J. Org. Chem. 2021, 17, 343–378, doi:10.3762/bjoc.17.32

• can be trapped by TMSCN to furnish α-(trifluoromethyl)-α-aminonitrile 183 in 40% yield. The iminium was also successfully trapped by a silyl enol ether, affording a mixture of ketone 184 and heterocycle 185 (Scheme 44). The trifluoromethyl-substituted derivatives 186a–c have then been exploited as a

Annulation of a 1,3-dithiole ring to a sterically hindered o-quinone core. Novel ditopic redox-active ligands

• Sergey V. Norkov,
• Anton V. Cherkasov,
• Andrey S. Shavyrin,
• Maxim V. Arsenyev,
• Viacheslav A. Kuropatov and
• Vladimir K. Cherkasov

Beilstein J. Org. Chem. 2021, 17, 273–282, doi:10.3762/bjoc.17.26

• -quinones. A study of their monoreduced semiquinone derivatives reveal that the spin density is delocalized across the whole molecule, including peripheral fragments. The first stable o-quinone derivative bearing an annulated thiete heterocycle has been isolated and characterized. Keywords: dioxolene

• of this species is the subject of further investigations. The bicyclic fragment in 7 is essentially flat (Figure S5 in Supporting Information File 1). The steric interactions between the tert-butyl groups and atoms of the fused heterocycle are weaker for the four-membered thiete ring than in the case

Regioselective synthesis of heterocyclic N-sulfonyl amidines from heteroaromatic thioamides and sulfonyl azides

• Vladimir Ilkin,
• Vera Berseneva,
• Tetyana Beryozkina,
• Tatiana Glukhareva,
• Lidia Dianova,
• Wim Dehaen,
• Eugenia Seliverstova and
• Vasiliy Bakulev

Beilstein J. Org. Chem. 2020, 16, 2937–2947, doi:10.3762/bjoc.16.243

• the heterocycle the N-sulfonyl amidines exist in either E- or Z-isomeric forms. Experimental X-ray diffraction study X-ray analyses were accomplished on an Xcalibur 3 diffractometer using the standard procedure (graphite-monochromated Mo Kα irradiation, ω-scanning with step 1o, T = 295(2) K (see

Using multiple self-sorting for switching functions in discrete multicomponent systems

• Amit Ghosh and
• Michael Schmittel

Beilstein J. Org. Chem. 2020, 16, 2831–2853, doi:10.3762/bjoc.16.233

• + + [Cu2(40)2]2+ + 2 × [Cu(42)]+ (= SelfSORT-II). With SelfSORT-I containing the heterocycle 42, a known organocatalyst, and SelfSORT-II holding the potential click catalyst [Cu(42)]+, it was speculated that both networked states could be catalytically active thus allowing the ON/OFF regulation of a dual

Access to highly substituted oxazoles by the reaction of α-azidochalcone with potassium thiocyanate

• Mysore Bhyrappa Harisha,
• Pandi Dhanalakshmi,
• Rajendran Suresh,
• Raju Ranjith Kumar and
• Shanmugam Muthusubramanian

Beilstein J. Org. Chem. 2020, 16, 2108–2118, doi:10.3762/bjoc.16.178

• ][41][42]. 2,4,5-Trisubstituted oxazoles are embedded in some natural products and pharmaceuticals with a broad range of biological activities prompting the development of efficient synthetic strategies for this useful heterocycle [43][44] (Figure 1). In the recent past, the readily accessible 2H

Regiodivergent synthesis of functionalized pyrimidines and imidazoles through phenacyl azides in deep eutectic solvents

• Paola Vitale,
• Luciana Cicco,
• Ilaria Cellamare,
• Filippo M. Perna,
• Antonio Salomone and
• Vito Capriati

Beilstein J. Org. Chem. 2020, 16, 1915–1923, doi:10.3762/bjoc.16.158

• between 180 °C and 240 °C [35]. The investigation of the thermal stability of phenacyl azides 2 led to the fortuitous discovery of the competitive formation of a different heterocycle. Indeed, while phenacyl azide (2a) was stable per se in a ChCl/Gly mixture after stirring at rt for 12 h, a new

When metal-catalyzed C–H functionalization meets visible-light photocatalysis

• Lucas Guillemard and
• Joanna Wencel-Delord

Beilstein J. Org. Chem. 2020, 16, 1754–1804, doi:10.3762/bjoc.16.147

• units (Figure 25) [87]. Interestingly, in this approach, the purine heterocycle acted as an inherent DG for the C–H activation step. The protocol provided a broad scope of products featuring good functional group tolerance, could be performed on a gram scale and occurred under mild conditions, essential

Tuneable access to indole, indolone, and cinnoline derivatives from a common 1,4-diketone Michael acceptor

• Dalel El-Marrouki,
• Sabrina Touchet,
• Abderrahmen Abdelli,
• Hédi M’Rabet,
• Mohamed Lotfi Efrit and
• Philippe C. Gros

Beilstein J. Org. Chem. 2020, 16, 1722–1731, doi:10.3762/bjoc.16.144

• -tetrahydrocinnoline) derivatives in moderate to excellent yields. Keywords: cinnoline; 1,4-diketone; indole; indolone; N-heterocycle; Introduction Nitrogen-containing heterocycles are widespread in plenty of molecules of interest, either in materials science, optics, electronics, or biology [1][2][3][4]. They are

Clickable azide-functionalized bromoarylaldehydes – synthesis and photophysical characterization

• Dominik Göbel,
• Marius Friedrich,
• Enno Lork and
• Boris J. Nachtsheim

Beilstein J. Org. Chem. 2020, 16, 1683–1692, doi:10.3762/bjoc.16.139

• fluorescence. This may be owing to the azide moiety, either as a functional group or as part of the triazole heterocycle. Similar observations were already made for luminescent materials [74][75]. Fluorene derivatives were subjected to photophysical measurements as well. UV–vis absorption spectra of

• CuAAC. Initial photophysical investigations of azide-functionalized bromocarbaldehydes and fluorenes revealed that the azide moiety and the triazole heterocycle efficiently quench phosphorescent transitions. Efforts of installing other functional groups suitable for covalent connections or modifications

Heterogeneous photocatalysis in flow chemical reactors

• Christopher G. Thomson,
• Ai-Lan Lee and
• Filipe Vilela

Beilstein J. Org. Chem. 2020, 16, 1495–1549, doi:10.3762/bjoc.16.125

• aromatic heterocycle substrates within 8–20 min, transformations that would require days in batch protocols (Scheme 1) [62]. Flow systems can be pressurised easily with back pressure regulators, enhancing the solubility of gaseous reagents in the reaction solvents [36][63]. Flow processes are also commonly

One-step route to tricyclic fused 1,2,3,4-tetrahydroisoquinoline systems via the Castagnoli–Cushman protocol

• Aleksandar Pashev,
• Nikola Burdzhiev and
• Elena Stanoeva

Beilstein J. Org. Chem. 2020, 16, 1456–1464, doi:10.3762/bjoc.16.121

• heterocycle is present in several alkaloids such as emetine (1) and related compounds, that exhibit biological activities such as glucosidase inhibition, anti-amoebic properties as well as activity against breast cancer cell lines [2]. Notable examples of synthetic compounds include the dipeptidyl peptidase

Highly selective Diels–Alder and Heck arylation reactions in a divergent synthesis of isoindolo- and pyrrolo-fused polycyclic indoles from 2-formylpyrrole

• Carlos H. Escalante,
• Eder I. Martínez-Mora,
• Carlos Espinoza-Hicks,
• Alejandro A. Camacho-Dávila,
• Fernando R. Ramos-Morales,
• Francisco Delgado and
• Joaquín Tamariz

Beilstein J. Org. Chem. 2020, 16, 1320–1334, doi:10.3762/bjoc.16.113

• that are known to have varied and robust pharmacological activity, such as isoborreverine (1) [12], mitomycin A (2) [13] and chlorizidine A (3) [14]. The indole moiety is incorporated into their structure, which is important because it is a seminal heterocycle that exhibits a wide range of biological

• nitrogen atom of the heterocycle. Since it is not clear what factors favor this relevant selectivity, the geometry and energy of the TSs were calculated for some of the diene–dienophile pairs depicted in Table 2 (vide infra). Cyclization via an intramolecular Heck arylation reaction Before attempting the

Photocatalysis with organic dyes: facile access to reactive intermediates for synthesis

• Stephanie G. E. Amos,
• Marion Garreau,
• Luca Buzzetti and
• Jerome Waser

Beilstein J. Org. Chem. 2020, 16, 1163–1187, doi:10.3762/bjoc.16.103

• transformation, the arene is first oxidized by the excited state of the photocatalyst, generating the arene radical cation I. The latter then undergoes a nucleophilic attack of the N-heterocycle, affording the radical adduct II. TEMPO and O2 act as oxidants for the formation of the final aromatic compound via

Synthesis and anticancer activity of bis(2-arylimidazo[1,2-a]pyridin-3-yl) selenides and diselenides: the copper-catalyzed tandem C–H selenation of 2-arylimidazo[1,2-a]pyridine with selenium

• Mio Matsumura,
• Tsutomu Takahashi,
• Hikari Yamauchi,
• Shunsuke Sakuma,
• Yukako Hayashi,
• Tadashi Hyodo,
• Tohru Obata,
• Kentaro Yamaguchi,
• Yasuyuki Fujiwara and
• Shuji Yasuike

Beilstein J. Org. Chem. 2020, 16, 1075–1083, doi:10.3762/bjoc.16.94

• of UVA-induced stress [17], and bis(2-alkylindol-3-yl) selenides III exhibit antitumor activity toward HT-1080 and MG-22A tumor cell lines [18]. The imidazo[1,2-a]pyridine ring is also an important aromatic heterocycle because its derivatives are biologically active and play an important role in

Copper-catalysed alkylation of heterocyclic acceptors with organometallic reagents

• Yafei Guo and
• Syuzanna R. Harutyunyan

Beilstein J. Org. Chem. 2020, 16, 1006–1021, doi:10.3762/bjoc.16.90

• , and Grignard reagents. Review Copper-catalysed C–C bond-forming reactions at the heterocycle The direct synthesis of chiral heterocyclic molecules from pyridine, quinolone, or indole derivatives is advantageous due to the abundance of such building blocks. Unfortunately, establishing catalytic

Recent advances in Cu-catalyzed C(sp³)–Si and C(sp³)–B bond formation

• Balaram S. Takale,
• Ruchita R. Thakore,
• Elham Etemadi-Davan and
• Bruce H. Lipshutz

Beilstein J. Org. Chem. 2020, 16, 691–737, doi:10.3762/bjoc.16.67

• group [68] used silicon-based Grignard reagents 189 to add to conjugated heteroaromatics 188, e.g., benzoxazole (as an extension to more commonly studies ketones, esters, imines, etc.), leading to products 190–194. The heterocycle played a crucial role, as in its absence, none of the expected product

Design and synthesis of diazine-based panobinostat analogues for HDAC8 inhibition

• Sivaraman Balasubramaniam,
• Sajith Vijayan,
• Liam V. Goldman,
• Xavier A. May,
• Kyra Dodson,
• Sweta Adhikari,
• Fatima Rivas,
• Davita L. Watkins and
• Shana V. Stoddard

Beilstein J. Org. Chem. 2020, 16, 628–637, doi:10.3762/bjoc.16.59

• analogues and subject them towards biological evaluation [16][17][18][19]. In addition, our envisioned dinitrogen heterocycle cores may have increased interactions in the binding pockets, and thus leading to a better therapeutic activity. Aiming to provide a strategy to address our global objective of

• nitrogen-containing heterocycle in the core ring structure would enhance the pharmacological properties while maintaining the level of HDAC8 inhibition. The targets TOI1–4 were synthesized from commercially available starting materials in moderate yields. The synthesized compounds displayed potent activity

A systematic review on silica-, carbon-, and magnetic materials-supported copper species as efficient heterogeneous nanocatalysts in “click” reactions

• Pezhman Shiri and
• Jasem Aboonajmi

Beilstein J. Org. Chem. 2020, 16, 551–586, doi:10.3762/bjoc.16.52

• employed in diverse organic reactions, including Suzuki reactions [64], Sonogashira reactions [65], transesterifications of triglycerides [66], hydrogenation reactions [67], N-heterocycle syntheses [68], cleavage of propargyl phenol ethers [69], etc. [70][71][72][73][74][75]. In this review article, we

Regio- and stereoselective synthesis of new ensembles of diversely functionalized 1,3-thiaselenol-2-ylmethyl selenides by a double rearrangement reaction

• Svetlana V. Amosova,
• Andrey A. Filippov,
• Nataliya A. Makhaeva,
• Alexander I. Albanov and
• Vladimir A. Potapov

Beilstein J. Org. Chem. 2020, 16, 515–523, doi:10.3762/bjoc.16.47

• 1 with potassium selenocyanate was studied in detail. We found that the reaction of thiaselenole 1 with KSeCN at room temperature afforded a five-membered heterocycle, selenocyanate 4, in a quantitative yield. This result was unusual since previously studied substitution reactions of thiaselenole 1

• proceeded already at 0 °C, and therefore we were not able to isolate compound 5 under these conditions. The formation of the six-membered heterocycle of 2,3-dihydro-1,4-thiaselenin-2-yl selenocyanate 5 was confirmed, inter alia, by the observation of two doublets corresponding to the olefinic protons of the

• SCH=CHSe group with 3J = 9.9 Hz in the 1H NMR spectrum (Table 1, entry 2). In the case of five-membered compounds 1 and 4, the coupling constant of the olefinic protons of the SCH=CHSe group would be 3JH,H = 6.3 Hz [32][40]. The SCHSe group of the heterocycle 5 was characterized by a doublet of