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

• intermediate in these reactions is supposed to be α-(trifluoromethyl)propargylium ion 133↔133’. Heteroatom-substituted α-(trifluoromethyl)carbenium ions The stabilization of carbenium ions through oxygen lone pair back-donation [35] is a common feature in organic synthesis [88][89][90]. In this context, Olah

Silver-catalyzed synthesis of β-fluorovinylphosphonates by phosphonofluorination of aromatic alkynes

• Yajing Zhang,
• Qingshan Tian,
• Guozhu Zhang and
• Dayong Zhang

Beilstein J. Org. Chem. 2020, 16, 3086–3092, doi:10.3762/bjoc.16.258

• . Among the strategies for constructing diverse alkenes containing two-heteroatom bonds, such as disulfonylation [14][15][16], heterohalogenation [17][18][19][20], bis(trifluoromethyl)thiolation [21], and phosphorylation [22], the direct heterodifunctionalization of alkynes using three-component reactions

Synthesis and characterization of S,N-heterotetracenes

• Astrid Vogt,
• Florian Henne,
• Christoph Wetzel,
• Elena Mena-Osteritz and
• Peter Bäuerle

Beilstein J. Org. Chem. 2020, 16, 2636–2644, doi:10.3762/bjoc.16.214

• systems. The various obtained heteroatom sequences ‘SSNS’ (SN4), ‘SNNS’ (SN4’’), and ‘NSSN’ (SN4’) allowed for evaluation of structure–property relationships relative to the sulfur analogue tetrathienoacene (‘SSSS’). In line with the results for the whole series of S,N-heteroacenes, we find that

• fused thiophene unit by a pyrrole ring. For TTA various synthetic methods have been developed and it has been broadly implemented as building block into materials for organic electronic devices [32][33]. We have disclosed the first SN4 derivative with the heteroatom sequence ‘SSNS’ in the context of

• the heteroatom sequence ‘NSSN’ (Scheme 5). The use of triphenyl phosphite as reducing agent gave a decreased yield of 24%. The N-alkylated derivative of hexacyclic SN4' 22 was prepared by Wong et al., who applied the Cadogan reaction to cyclize a dibrominated precursor similar to 21. Without isolation

Synthetic approaches to bowl-shaped π-conjugated sumanene and its congeners

• Shakeel Alvi and
• Rashid Ali

Beilstein J. Org. Chem. 2020, 16, 2212–2259, doi:10.3762/bjoc.16.186

• transfer systems, cation–π complexation, electron conductivity, optical properties and so on. Keeping the importance of this beautiful scaffold in mind, we compiled all the synthetic routes available for the construction of sumanene and its heteroatom derivatives including Mehta’s first unsuccessful effort

• molecules. Notably, it has been found that the introduction of heteroatom(s) in the periphery of these architectures generally decrease the depth of bowl, may be because of an increase in the carbon–heteroatom bond length. For this reason, these heterobuckybowls possess less strained energy due to shallower

Efficient [(NHC)Au(NTf₂)]-catalyzed hydrohydrazidation of terminal and internal alkynes

• Maximillian Heidrich and
• Herbert Plenio

Beilstein J. Org. Chem. 2020, 16, 2080–2086, doi:10.3762/bjoc.16.175

• ; Introduction Cationic gold complexes with weakly coordinating counterions (which are often considered to be solvent-separated ions) [1][2][3], render powerful catalysts for the transformation of organic substrates [4][5][6], specifically the reactions of alkynes with a variety of heteroatom nucleophiles

Reactions of 3-aryl-1-(trifluoromethyl)prop-2-yn-1-iminium salts with 1,3-dienes and styrenes

• Thomas Schneider,
• Michael Keim,
• Bianca Seitz and
• Gerhard Maas

Beilstein J. Org. Chem. 2020, 16, 2064–2072, doi:10.3762/bjoc.16.173

• effects can modulate the conformational, physicochemical and electronic properties of a molecule. Two major strategies exist to introduce a CF3 group into a target molecule: formation of a carbon‒ or heteroatom‒CF3 bond [8][9] and the use of preformed CF3-substituted building blocks. During our studies on

Isolation and structure determination of a tetrameric sulfonyl dilithio methandiide in solution based on crystal structure analysis and ⁶Li/¹³C NMR spectroscopic data

• Jürgen Vollhardt,
• Hans Jörg Lindner and
• Hans-Joachim Gais

Beilstein J. Org. Chem. 2020, 16, 2057–2063, doi:10.3762/bjoc.16.172

• ][36][37][38][39][40][41][42][43]. They generally showed intricate aggregates with complex C–Li and C–Li–heteroatom chains, containing doubly lithiated C atoms. However, as much as there is now knowledge of the structure of dilithio methandiides in the crystal, as little is known about the structure

• . Methandiides IIIa and carbanion IIIb have in contrast to 2a a further lithium atom coordinating and stabilizing heteroatom-substituent. Both methandiides are tetramers, featuring dilithiated dianionic carbon atoms with a coordination geometry, which strongly deviates from tetrahedral and O–Li, S–Li, and N–Li

Automated high-content imaging for cellular uptake, from the Schmuck cation to the latest cyclic oligochalcogenides

• Rémi Martinent,
• Javier López-Andarias,
• Dimitri Moreau,
• Yangyang Cheng,
• Naomi Sakai and
• Stefan Matile

Beilstein J. Org. Chem. 2020, 16, 2007–2016, doi:10.3762/bjoc.16.167

• ion-pair interaction. For example, the replacement of the pyrrole core to pyridine in 8 or to furan results in a much weaker binding because of the repulsion force between the lone pair on the heteroatom and the oxoanion. The superior oxoanion binding of the Schmuck cation makes GCP-based peptides

Selective preparation of tetrasubstituted fluoroalkenes by fluorine-directed oxetane ring-opening reactions

• Clément Q. Fontenelle,
• Thibault Thierry,
• Romain Laporte,
• Emmanuel Pfund and
• Thierry Lequeux

Beilstein J. Org. Chem. 2020, 16, 1936–1946, doi:10.3762/bjoc.16.160

• through an olefination reaction with benzothiazoyl sulfones (Scheme 1) [22]. With these fluoroalkylidene-oxetanes in hands, we studied the selectivity of ring-opening reactions with heteroatom nucleophiles in order to access tetrasubstituted fluoroalkenes. A control of the geometry of these reactions

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

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

• bipyridyl units have been designed to immobilise transition metal complexes through coordinate bonding for the oxidative coupling of amines [138]. [Ru(bpy)3]2+ units were synthesised with ethynyl groups para-substituted to the nitrogen heteroatom on four of the six pyridine rings. The ethynyl groups were

4-Hydroxy-3-methyl-2(1H)-quinolone, originally discovered from a Brassicaceae plant, produced by a soil bacterium of the genus Burkholderia sp.: determination of a preferred tautomer and antioxidant activity

• Dandan Li,
• Naoya Oku,
• Yukiko Shinozaki,
• Yoichi Kurokawa and
• Yasuhiro Igarashi

Beilstein J. Org. Chem. 2020, 16, 1489–1494, doi:10.3762/bjoc.16.124

• were revealed: a consecutive four aromatic methines (δC 129.8, 122.7, 121.2, 115.0; δH 7.85, 7.41, 7.23, 7.12), two heteroatom-substituted nonprotonated sp2 carbons (δC 164.0 and 157.4), three sp2 nonprotonated carbons (δC 137.4, 115.8, and 106.9), an allylic methyl group (δC 9.6/δH 1.98 s), and a

Photocatalyzed syntheses of phenanthrenes and their aza-analogues. A review

• Alessandra Del Tito,
• Havall Othman Abdulla,
• Davide Ravelli,
• Stefano Protti and
• Maurizio Fagnoni

Beilstein J. Org. Chem. 2020, 16, 1476–1488, doi:10.3762/bjoc.16.123

• ) finally yields the desired phenanthridine 4.4. Different radical sources R–X have been adopted to generate carbon or heteroatom-based radicals according to the general photocatalytic strategy gathered in Scheme 4, for their use in the construction of phenanthridine scaffolds. As an example, unsubstituted

• starting from alkylhydrazines [66]. However, a heteroatom-based radical may be used for the addition onto isonitriles as well. One such example dealt with the photoredox tandem phosphonylation/cyclization of diphenylphosphine oxides with 2-arylphenylisonitriles. Here, the sequential formation of C–P and C

An overview on disulfide-catalyzed and -cocatalyzed photoreactions

• Yeersen Patehebieke

Beilstein J. Org. Chem. 2020, 16, 1418–1435, doi:10.3762/bjoc.16.118

• successful substrates for this transformation. Although multiple olefins can be successful olefinic coupling partners for this reaction, electron-rich olefins bearing an α-heteroatom would be preferable for achieving a better enantioselectivity. In 1990, Singleton and co-workers reported disulfide-catalyzed

Activated carbon as catalyst support: precursors, preparation, modification and characterization

• Melanie Iwanow,
• Tobias Gärtner,
• Volker Sieber and
• Burkhard König

Beilstein J. Org. Chem. 2020, 16, 1188–1202, doi:10.3762/bjoc.16.104

• composition by CHNS/O: The elemental composition is determined for starting materials as well as for the resulting activated carbon materials. Thereby, the influence of the different preparation, activation and modification methods on the carbon or heteroatom content can be compared. Nowicki et al. found that

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

• reactive intermediates. After a short introduction on activation modes in photocatalysis, selected case studies where organic dyes have been exploited for generating carbon-centered radicals, charged open-shell species, and heteroatom-centered radicals will be covered. The last short section will be

• )) radicals are important reactive intermediates for the construction of C–C and C–heteroatom bonds [31]. Their addition onto unsaturated systems, such as olefins and arenes, is particularly efficient. Additionally, alkyl radicals can undergo translocations, abstracting atoms from different sites. Recently

• for the synthesis of the arylated heteroarenes 12.3 via an intermolecular process [79]. Alemán and co-workers used PHTH (OD16) for the synthesis of various heteroatom-containing bicycles 12.4 through a tethered electrophile approach [80]. For the second strategy, König and co-workers developed an

Recent applications of porphyrins as photocatalysts in organic synthesis: batch and continuous flow approaches

• Rodrigo Costa e Silva,
• Luely Oliveira da Silva,
• Aloisio de Andrade Bartolomeu,
• Timothy John Brocksom and
• Kleber Thiago de Oliveira

Beilstein J. Org. Chem. 2020, 16, 917–955, doi:10.3762/bjoc.16.83

• catalysts in both oxidative and reductive quenching. The use of porphyrins as a photosensitizer for singlet oxygen generation is presented in the second topic, which was subdivided into two sections: pericyclic reactions and heteroatom oxidations. The first section describes the use of singlet oxygen in

• pericyclic reactions with olefins and dienes, and the second deals with heteroatom oxidations carried out by singlet oxygen. Review Porphyrins as photoredox catalysts Porphyrins and metalloporphyrins have been extensively studied as photosensitizers in singlet oxygen generation, but underexploited as

• (bpy)3)]2+, [Ir(ppy)3], eosin Y, and 4CzTPN [12] (Figure 3). However, some porphyrin and metalloporphyrin derivatives possess adequate potentials to be applied as photoredox catalysts in C–C and C-heteroatom bond formations [10][22]. Furthermore, supramolecular porphyrin-containing molecules, such as

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

• )- and (E)-alkenes 311 afforded the (E)-alkene 312 as the major product. The targeted γ-borylated compounds (relative to the leaving group) were formed, each with high enantioselectivity, which can be used for further stereoselective C–C and C–X (X = heteroatom) bond formation. Catalytic Cu(NHC)-mediated

• addition (e.g., 351, 352). It was shown that the presence of a heteroatom plays a crucial role due to the otherwise non-selective, facile addition of Cu-Bpin to alkenes (Scheme 56) [103]. Based on previous studies on asymmetric 3-component carboboration of styrene derivatives [104] and 1,3-dienes [105

Synthesis of six-membered silacycles by borane-catalyzed double sila-Friedel–Crafts reaction

• Yafang Dong,
• Masahiko Sakai,
• Kazuto Fuji,
• Kohei Sekine and
• Yoichiro Kuninobu

Beilstein J. Org. Chem. 2020, 16, 409–414, doi:10.3762/bjoc.16.39

• ][6][7][8][9][10], and reagents [11][12][13][14]. Therefore, the development of new methods to construct silacyclic skeletons is highly desirable. These compounds are commonly synthesized upon the reaction of heteroatom-bridged dilithiated diaryl compounds, such as dilithiated diaryl ethers and

Architecture and synthesis of P,N-heterocyclic phosphine ligands

• Wisdom A. Munzeiwa,
• Bernard Omondi and
• Vincent O. Nyamori

Beilstein J. Org. Chem. 2020, 16, 362–383, doi:10.3762/bjoc.16.35

• occurs selectively on the end opposite to the phosphorus donor atom [48]. This is because the position trans to the heteroatom, with greater π-acceptor character, is more electrophilic than the one opposite the σ-donor atom [9]. One can modify this electronic imbalance by attaching vicinal heteroatoms

• from α-C–H bond activation in heterocycles The α-position to a heteroatom in a cyclic compound is activated because of the difference in electronegativity with carbon. This presents an opportunity to readily generate organometallic nucleophiles. Chelucci et al. [71] used this fact to synthesize the

Extension of the 5-alkynyluridine side chain via C–C-bond formation in modified organometallic nucleosides using the Nicholas reaction

• Renata Kaczmarek,
• Dariusz Korczyński,
• James R. Green and
• Roman Dembinski

Beilstein J. Org. Chem. 2020, 16, 1–8, doi:10.3762/bjoc.16.1

• -acetate hexacarbonyl dicobalt complexes and a Lewis or Brønsted acid. A range of heteroatom nucleophiles have been incorporated into alkyne dicobalt complexes by this chemistry [34][35][36][37][38][39][40]. However, reactions with carbon-based nucleophiles provide an opportunity to access the structurally

Chemical tuning of photoswitchable azobenzenes: a photopharmacological case study using nicotinic transmission

• Lorenzo Sansalone,
• Jun Zhao,
• Matthew T. Richers and
• Graham C. R. Ellis-Davies

Beilstein J. Org. Chem. 2019, 15, 2812–2821, doi:10.3762/bjoc.15.274

• biologically inert, irradiation with violet light effectively "uncaged" agonist activity, but in a photoreversible manner. Since the neurotransmitter acetylcholine has fully saturated heteroatom valences, our photoswitchable 4FABTA probe could be useful for physiological studies of this neurotransmitter

Iodine-mediated hydration of alkynes on keto-functionalized scaffolds: mechanistic insight and the regiospecific hydration of internal alkynes

• Zachary Lee,
• Brandon R. Jones,
• Nyochembeng Nkengbeza,
• Michael Phillips,
• Kayla Valentine,
• Alexis Stewart,
• Brandon Sellers,
• Nicholas Shuber and
• Karelle S. Aiken

Beilstein J. Org. Chem. 2019, 15, 2747–2752, doi:10.3762/bjoc.15.265

• hydration reaction of alkynes serves as a green alternative to metal-catalyzed procedures. Previous work has shown that this method works well with terminal alkynes on keto-functionalized scaffolds, including 1,3-dicarbonyls and their heteroatom analogues. It was hypothesized that the reaction proceeds

Synthesis of aryl-substituted thieno[3,2-b]thiophene derivatives and their use for N,S-heterotetracene construction

• Nadezhda S. Demina,
• Nikita A. Kazin,
• Nikolay A. Rasputin,
• Roman A. Irgashev and
• Gennady L. Rusinov

Beilstein J. Org. Chem. 2019, 15, 2678–2683, doi:10.3762/bjoc.15.261

• used to architect various ring-fused S-heteroacenes, which have been studied extensively [8][9][10] due to their better characteristics compared to heteroatom-free acenes. For instance, S-heteroacenes have a better oxidation stability due to lower-lying HOMO levels, as well as more efficient charge

A toolbox of molecular photoswitches to modulate the CXCR3 chemokine receptor with light

• Xavier Gómez-Santacana,
• Sabrina M. de Munnik,
• Tamara A. M. Mocking,
• Niels J. Hauwert,
• Shanliang Sun,
• Prashanna Vijayachandran,
• Iwan J. P. de Esch,
• Henry F. Vischer,
• Maikel Wijtmans and
• Rob Leurs

Beilstein J. Org. Chem. 2019, 15, 2509–2523, doi:10.3762/bjoc.15.244

• , Supporting Information File 1) and the photoisomerization are observed. When the substituent Y is a halogen atom, we observe a slight bathochromic shift of the π–π* band to higher wavelengths with increasing size of the heteroatom, from 323 nm for Y = H (3e) to 339 nm for Y = I (6e) (Table 3, Figure 4A