Et₃N/DMSO-supported one-pot synthesis of highly fluorescent β-carboline-linked benzothiophenones via sulfur insertion and estimation of the photophysical properties

• Dharmender Singh,
• Vipin Kumar and
• Virender Singh

Beilstein J. Org. Chem. 2020, 16, 1740–1753, doi:10.3762/bjoc.16.146

• -metal-free strategy is presented to access novel β-carboline-tethered benzothiophenone derivatives from 1(3)-formyl-β-carbolines using elemental sulfur activated by Et3N/DMSO. This expeditious catalyst-free reaction proceeds through the formation of β-carboline-based 2-nitrochalcones followed by an

• incorporation of sulfur to generate multifunctional β-carboline-linked benzothiophenones in good to excellent yields. The synthetic strategy could also be extended towards the synthesis of β-carboline-linked benzothiophenes. Moreover, the afforded products emerged as promising fluorophores and displayed

• excellent light-emitting properties with quantum yields (ΦF) up to 47%. Keywords: benzothiophene; β-carboline; metal-free; photophysical properties; sulfur insertion; Introduction The pyrido[3,4-b]indole moiety, commonly referred as β-carboline, is the core unit of about one quarter of all natural

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

• are highly desirable [16][17][34][35][36][37]. Two approaches are applied to achieve organic phosphors: (1) introduction of nonmetal heavy atoms, such as halogens (Br or I) or functionalities containing lone pairs, in particular carbonyl groups, nitrogen, sulfur, and phosphorus derivatives which

Pauson–Khand reaction of fluorinated compounds

• Jorge Escorihuela,
• Daniel M. Sedgwick,
• Alberto Llobat,
• Mercedes Medio-Simón,
• Pablo Barrio and
• Santos Fustero

Beilstein J. Org. Chem. 2020, 16, 1662–1682, doi:10.3762/bjoc.16.138

• synthesize trifluoromethylated nitrogen- and sulfur-based bicyclic compounds (Scheme 13) [53]. Using this methodology, the corresponding cyclopentenones 29 were isolated in generally good yields, except for sulfur-containing derivative 29c, due to the oxidation of the sulfide under the reaction conditions

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

• the corresponding substituted phenanthridine. The F3C· radical was formed by the Fukuzumi catalyst Mes-Acr+ photocatalyzed oxidation of the Langlois reagent [82]. Sulfur-centered radicals may be generated via the reduction of sulfonyl chlorides and in turn exploited to construct 6-(sulfonylmethyl

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

• Abstract The Castagnoli–Cushman reaction of 3,4-dihydroisoquinolines with glutaric anhydride, its oxygen and sulfur analogues was investigated as a one-step approach to the benzo[a]quinolizidine system and its heterocyclic analogs. An extension towards the pyrrolo[2,1-a]isoquinoline system was achieved

• for the construction of these heteropolycycles is of great significance to both organic and medicinal chemistry. The Castagnoli–Cushman reaction (CCR) between cyclic enolizable anhydrides (such as succinic (5) [9], glutaric (6) [10], and the corresponding oxygen (7) [11], sulfur (8) [11], and nitrogen

• substituted benzo[a]quinolizidinones and pyrrolo[2,1-a]isoquinolinones. This reaction also would allow the construction of bioisosteric oxygen and sulfur derivatives of the target heterocyclic framework. Results and Discussion Our synthetic strategy relied on the possibility to form ring C of the target ring

Recent synthesis of thietanes

• Jiaxi Xu

Beilstein J. Org. Chem. 2020, 16, 1357–1410, doi:10.3762/bjoc.16.116

• of sulfur-containing acyclic and heterocyclic compounds [10][11]. Several synthetic methods for thietanes have been developed and reviewed [12][13][14]. One traditional route is the intermolecular double substitution (cyclic thioetherification) of 1,3-dihaloalkanes, sulfonates of 3-haloalkan-1-ols

• as inhibitor of kinases, insecticides, and acaricides, its sulfur analogue, 6-amino-2-thiaspiro[3,3]heptane (28) was prepared from the cheap starting material 2,2-bis(bromomethyl)propane-1,3-diol (11). Compound 11 was converted into 3-(tert-butoxycarbonyl)-1,1-bis(hydroxymethyl)aminocyclobutane (25

• ) hydrogen chloride salt after the acidic deprotection [37] (Scheme 5). During recent decades, the cyclic thioetherification strategy was widely applied in the synthesis of thietane-based square sugurs (thietanoses), and sulfur-containing glycomimetics of furanoses and pyranoses [38]. The first thietanose

Ferrocenyl-substituted tetrahydrothiophenes via formal [3 + 2]-cycloaddition reactions of ferrocenyl thioketones with donor–acceptor cyclopropanes

• Grzegorz Mlostoń,
• Mateusz Kowalczyk,
• André U. Augustin,
• Peter G. Jones and
• Daniel B. Werz

Beilstein J. Org. Chem. 2020, 16, 1288–1295, doi:10.3762/bjoc.16.109

• thioketones; sulfur heterocycles; tetrahydrothiophenes; Introduction Functionalized tetrahydrothiophenes constitute an important group of five-membered sulfur heterocycles; many of them, both chiral and achiral, with biotin as the best-known representative, form the key motif in numerous compounds of great

• the formal [4 + 3]-cycloaddition [10] (Scheme 2). In a series of our recent publications, ferrocenyl/aryl and ferrocenyl/alkyl thioketones were demonstrated to be attractive substrates for the preparation of six- and five-membered sulfur heterocycles via [4 + 2]- and [3 + 2]-cycloadditions

• used with no special precautions. In general, ferrocene has been considered as an ‘exceptional compound’ [16][17] and in our hands ferrocenyl-functionalized sulfur heterocycles, e.g., thiiranes and 1,3-dithiolanes, have found applications for the synthesis of compounds relevant for medicinal [18] and

Oxime radicals: generation, properties and application in organic synthesis

• Igor B. Krylov,
• Stanislav A. Paveliev,
• Alexander S. Budnikov and
• Alexander O. Terent’ev

Beilstein J. Org. Chem. 2020, 16, 1234–1276, doi:10.3762/bjoc.16.107

• yield of 76. A radical mechanism was proposed in which the oxime moiety is oxidized by DDQ to the iminoxyl radical 77, which undergoes 1,5-HAT to give a C-centered radical 78 stabilized by a sulfur atom. 78 is oxidized by DDQ to a carbocation 79, followed by the closure of the oxathiazole ring (Scheme

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

• ]. Fourier transmission infrared spectroscopy (FTIR): Activated carbon consists mainly of carbon atoms, besides different heteroatoms such as oxygen, hydrogen, nitrogen and sulfur. Thus, different functional groups govern the surface of the activated carbons and FTIR provides information on these chemical

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

• -, nitrogen-, oxygen-, and sulfur-centered radicals, open-shell charged species, and sensitized organic compounds. Keywords: organic dyes; photocatalysis; photoredox catalysis; radicals; reactive intermediates; Review Introduction In the last decade, synthetic organic chemistry has experienced the

• tritiation of biologically relevant compounds using D2O and T2O as hydrogen isotope sources (Scheme 9) [60]. The SET oxidation of the thiol cocatalyst 9.2, triggered by the excited photocatalyst 4CzIPN (OD6), generates a sulfur-centered radical capable of driving the HAT process with the substrate 9.1. The

• . The precursors of choice encompass aryl diazonium salts, haloarenes, and sulfur(IV) or sulfur(VI) compounds (Scheme 10). Aryl radicals from aryl diazonium salts. Aryl diazonium salts are attractive substrates for accessing aryl radicals. Despite their intrinsic thermal instability and exothermic

The charge-assisted hydrogen-bonded organic framework (CAHOF) self-assembled from the conjugated acid of tetrakis(4-aminophenyl)methane and 2,6-naphthalenedisulfonate as a new class of recyclable Brønsted acid catalysts

• Svetlana A. Kuznetsova,
• Alexander S. Gak,
• Yulia V. Nelyubina,
• Vladimir A. Larionov,
• Han Li,
• Michael North,
• Vladimir P. Zhereb,
• Alexander F. Smol'yakov,
• Artem O. Dmitrienko,
• Michael G. Medvedev,
• Igor S. Gerasimov,
• Ashot S. Saghyan and
• Yuri N. Belokon

Beilstein J. Org. Chem. 2020, 16, 1124–1134, doi:10.3762/bjoc.16.99

• crystals (Figure 5) reached a plateau at 160 °C after 5.9% of the mass was removed as water. The plateau was maintained until 340 °C, when the sample underwent an endothermic decomposition. The decomposition produced sulfur dioxide, naphthalene, and aniline, according to the infrared spectra of the

A simple and easy to perform synthetic route to functionalized thienyl bicyclo[3.2.1]octadienes

• Dragana Vuk,
• Irena Škorić,
• Valentina Milašinović,
• Krešimir Molčanov and
• Željko Marinić

Beilstein J. Org. Chem. 2020, 16, 1092–1099, doi:10.3762/bjoc.16.96

• ' and 2', with different position of the sulfur in thiophene moiety, were selected. The compounds 1' and 2' were prepared according to the previously reported one-step photochemical methodology [15], and subjected to the Vilsmeier–Haack reaction (Scheme 2, Scheme 3), respectively. After chromatographic

Fluorinated phenylalanines: synthesis and pharmaceutical applications

• Laila F. Awad and
• Mohammed Salah Ayoup

Beilstein J. Org. Chem. 2020, 16, 1022–1050, doi:10.3762/bjoc.16.91

•  29). 2.4. Fluorodehydroxylation of β-hydroxyphenylalanine Alternatively, Kollonitach et al. prepared racemic 3-fluorophenylalanine (136) through the fluorodehydroxylation of 3-hydroxyphenylalanine (137) using sulfur tetrafluoride (SF4) in HF [67] (Scheme 30). 2.5. Ring opening of aziridine

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

• amides (Scheme 43) [93]. Singlet oxygen in heteroatom oxidations Singlet oxygen reacts readily with electron pairs of heteroatoms, such as sulfur, selenium, phosphorus, and nitrogen, due to their electrophilicity. The interaction between singlet oxygen and the heteroatom occurs in both physical and

• chemical quenching leading to the formation of covalent products [67]. Sulfur oxidation: One of the first examples reported for heteroatom oxidation by singlet oxygen was the oxidation of sulfides to sulfoxides [67]. Sulfoxides are important intermediates in organic synthesis, and with applications in

• medicine and pharmacology [94], justifying many studies on this topic. The accepted mechanism for sulfide oxidation to sulfoxide involves the chemical quenching of singlet oxygen by sulfur compounds which leads to the persulfoxide intermediate. From this intermediate, a variety of reaction pathways are

Cascade trifluoromethylthiolation and cyclization of N-[(3-aryl)propioloyl]indoles

• Ming-Xi Bi,
• Shuai Liu,
• Yangen Huang,
• Xiu-Hua Xu and
• Feng-Ling Qing

Beilstein J. Org. Chem. 2020, 16, 657–662, doi:10.3762/bjoc.16.62

• and agrochemical industries [3][4][5]. Traditional methods to access these compounds mainly include halogen–fluorine exchange of halomethyl sulfides and trifluoromethylation of sulfur-containing compounds [6][7][8]. Over the last decade, tremendous efforts have been triggered to develop methods for

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

• -, oxygen-, and sulfur-containing ligands were investigated soon after the disclosure of the auxiliary effect of ligands on copper-catalyzed alkyne–azide cycloaddition reactions [16][17]. Heterogeneous catalysts are safer than their homogeneous counterparts. They also offer some advantages, such as the ease

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

• ][24][25][26][27][28][29]. Among these is an elegant, highly effective approach that led to β-hydroxy, β-mercapto, and β-amino-substituted diorganyl diselenides and selenides. This was accomplished by the opening of three-membered oxygen-, sulfur- and nitrogen-containing heterocycles under the action

• which is more than one order of magnitude greater than the effect of the sulfur atom. This was established based on the determination of the absolute and relative rates of nucleophilic substitution of chlorine in 2,6-dichloro-9-selenabicyclo[3.3.1]nonane and 2,6-dichloro-9-thiabicyclo[3.3.1]nonane [36

• are important features of this approach. The obtained compounds represent novel ensembles of functionalized unsaturated five-membered heterocycles containing one sulfur atom and two selenium atoms of different nature (Schemes 8–11), which are valuable scaffolds for organic synthesis and medicinal

Controlling alkyne reactivity by means of a copper-catalyzed radical reaction system for the synthesis of functionalized quaternary carbons

• Goki Hirata,
• Yu Yamane,
• Naoya Tsubaki,
• Reina Hara and
• Takashi Nishikata

Beilstein J. Org. Chem. 2020, 16, 502–508, doi:10.3762/bjoc.16.45

• produce 3g and 3h, respectively. An arylalkyne 1 possessing an electron-withdrawing group (ester) yielded 3i without affecting the reactivity of 2. Sulfur functional groups tend to decrease the catalytic activity of copper salts, but thienyl-substituted alkyne 1 reacted with 2a to produce 3j in 48% yield

Recent developments in photoredox-catalyzed remote ortho and para C–H bond functionalizations

• Rafia Siddiqui and
• Rashid Ali

Beilstein J. Org. Chem. 2020, 16, 248–280, doi:10.3762/bjoc.16.26

• takes place for the generation of the S-centered radical 57. The reactive aryl radical 58 is obtained by the cyclization of the sulfur-based radical 57. Simultaneously, photocatalyst 11 is regenerated from Ru(I) photocatalyst 51 and Co(III) complex 56. Additionally, the Co(I) complex 54 and the cation

Synthesis, liquid crystalline behaviour and structure–property relationships of 1,3-bis(5-substituted-1,3,4-oxadiazol-2-yl)benzenes

• Afef Mabrouki,
• Malek Fouzai,
• Armand Soldera,
• Abdelkader Kriaa and
• Ahmed Hedhli

Beilstein J. Org. Chem. 2020, 16, 149–158, doi:10.3762/bjoc.16.17

• these latter do not adopt the same conformation, according to whether they carry a sulfur atom or not. Obviously, the inductive effects alone are inconsistent with the observed results. Hence, we considered the rigid-core (RC) and the terminal chains separately in order to identify a possible

• , (b”) side view; 2b, conformation C, (c) front view, (c’) top view, (c”) side view. Carbon atoms are shown in gray, hydrogen atoms in white, sulfur atoms in yellow, nitrogen atoms in blue, oxygen atoms in red and fluorine atoms in orange. Vector of dipole moment of compounds 4c, 4b and 2b. Plot of

Potent hemithioindigo-based antimitotics photocontrol the microtubule cytoskeleton in cellulo

• Alexander Sailer,
• Franziska Ermer,
• Yvonne Kraus,
• Rebekkah Bingham,
• Ferdinand H. Lutter,
• Julia Ahlfeld and
• Oliver Thorn-Seshold

Beilstein J. Org. Chem. 2020, 16, 125–134, doi:10.3762/bjoc.16.14

• reported that introducing electron-donating groups (methoxy, dimethylamino) in para-position to the thioindoxyl sulfur atom restored E-stability while maintaining red-shifted absorption maxima. This para-position was occupied by the key methoxy group in all our HITub designs. With scant information

• the sulfur atom, for maximal simplicity, we tested whether both substituents could be deleted simultaneously (HITub-4). This proved to be the strongest-performing compound of our studies, with the Z-isomer possessing an EC50 value of ca. 110 nM and a 4-fold difference of bioactivity between lit and

[1,3]/[1,4]-Sulfur atom migration in β-hydroxyalkylphosphine sulfides

• Katarzyna Włodarczyk,
• Piotr Borowski and
• Marek Stankevič

Beilstein J. Org. Chem. 2020, 16, 88–105, doi:10.3762/bjoc.16.11

• Marie Curie-Skłodowska Sq., 20-031 Lublin, Poland 10.3762/bjoc.16.11 Abstract β-Hydroxyalkylphosphine sulfides undergo [1,3]- or [1,4]-sulfur atom phosphorus-to-carbon migration in the presence of Lewis or Brønsted acids. The direction of sulfur atom migration depends on the type of acid used for the

• reaction. In the presence of a Brønsted acid, mainly [1,3]-rearrangement is observed, whereas a Lewis acid catalyzes the [1,4]-sulfur migration. To gain insight into the mechanism of these transformations, the stereochemistry of these rearrangements have been tested, along with the conduction of some

• control experiments and DFT calculations. Keywords: Brønsted and Lewis acids; DFT; mechanistic studies; rearrangement; stereochemistry; sulfur atom migration; Introduction Among all organic reactions, rearrangements are an exciting class of transformations where unusual or even unexpected products can

Microwave-assisted synthesis of 2-substituted 4,5,6,7-tetrahydro-1,3-thiazepines from 4-aminobutanol

• María C. Mollo,
• Natalia B. Kilimciler,
• Juan A. Bisceglia and
• Liliana R. Orelli

Beilstein J. Org. Chem. 2020, 16, 32–38, doi:10.3762/bjoc.16.5

• analogous effect was sometimes observed even in the sulfur analogues, as previously mentioned [32]. The differences between oxygen and sulfur regarding electronegativity and polarizability may explain the differential behaviour of the PPSE promoted ring closure of tetramethylenic amido and thioamido

• energy associated to the formation of a seven-membered heterocycle would favour the competitive ring closure leading to the five-membered ring (Scheme 2, reaction a), which would involve attack of the carboxamide nitrogen to the ω-carbon. On the other hand, the higher nucleophilicity of the sulfur in the

Palladium-catalyzed synthesis and nucleotide pyrophosphatase inhibition of benzo[4,5]furo[3,2-b]indoles

• Hoang Huy Do,
• Saif Ullah,
• Alexander Villinger,
• Joanna Lecka,
• Jean Sévigny,
• Peter Ehlers,
• Jamshed Iqbal and
• Peter Langer

Beilstein J. Org. Chem. 2019, 15, 2830–2839, doi:10.3762/bjoc.15.276

• , Asn245, Glu275, Tyr289, Leu239, Ser326, Thr205, His329 and Glu322 were involved in the hydrogen binding with suramin. One π–alkyl interaction was found with Pro288 and one metal interaction with zinc. Amino acid Tyr289 was connected with the sulfur atom as shown in Figure 5a. The hydrogen atoms of the

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

• transfer because of their tendency to π-stack, with non-bonded sulfur–sulfur interactions in the solid state, which results in large intermolecular orbital coupling of HOMOs and, as a consequence, enhanced carrier transport properties [10]. However, there is a problem of poor solubility of a number of S