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

• Supporting Information File 1). At the same time, the plane of the six-membered o-quinone ring is slightly distorted in order to weaken the steric strain effects of the tert-butyl groups and neighboring carbonyl oxygens/dithiole sulfur atoms. Such distortion is typical of sterically hindered o-quinones and

• intramolecular contacts with the sulfur atoms. The S(1)–O(2) distance (Figure S4 in Supporting Information File 1) is 2.560(2) Å, it is less than the sum of the van der Waals radii. A very similar geometry was previously observed in the case of the acetylacetonate unit attached to a 1,3-dithiole ring [31]. o

• bulky sulfur-containing group. The possible pathway for the following cyclization is the Michael addition of the sulfide atom to the central carbon of the acetylacetonate group [38][39][40][41]. The X-ray diffraction study as well as IR and NMR spectroscopy data reveal that in all synthesized compounds

Selective synthesis of α-organylthio esters and α-organylthio ketones from β-keto esters and sodium S-organyl sulfurothioates under basic conditions

• Jean C. Kazmierczak,
• Roberta Cargnelutti,
• Thiago Barcellos,
• Claudio C. Silveira and
• Ricardo F. Schumacher

Beilstein J. Org. Chem. 2021, 17, 234–244, doi:10.3762/bjoc.17.24

• rediscovered by many researchers as stable, nonhygroscopic, and moisture-resistant thiolating agents. Therefore, they have been actively studied as precursors for the preparation of diverse sulfur-containing compounds [1]. These recent findings include their use in direct sulfenylation reactions of electron

• sulfides by the acetamidosulfenylation of alkenes [12], among others [13][14][15]. Sulfur-containing compounds are important intermediates in organic synthesis, being able to act as an electrophile or nucleophile in many organic transformations [16][17][18]. Still, many of them are pharmacologically active

• ) and herbicidal applications (fluthiacet-methyl) [37][38]. In this sense, the development of efficient methodologies for the synthesis of sulfur-containing carbonyl compounds employing cheap, stable, nontoxic, easy-to-prepare, and easy-to-handle starting materials is crucial in contemporary organic

Decarboxylative trifluoromethylthiolation of pyridylacetates

• Ryouta Kawanishi,
• Kosuke Nakada and
• Kazutaka Shibatomi

Beilstein J. Org. Chem. 2021, 17, 229–233, doi:10.3762/bjoc.17.23

• mechanism for this reaction, as outlined in Scheme 5. An electrophilic sulfur atom of 6 approaches the nitrogen atom on the pyridine ring to promote decarboxylation via the formation of N-trifluoromethylthio-2-alkylidene-1,2-dihydropyridine intermediate I, which immediately isomerizes to afford 2 (Scheme 5

Exploring the possibility of using fluorine-involved non-conjugated electron-withdrawing groups for thermally activated delayed fluorescence emitters by TD-DFT calculation

• Dongyang Chen and
• Eli Zysman-Colman

Beilstein J. Org. Chem. 2021, 17, 210–223, doi:10.3762/bjoc.17.21

• also been attributed by Duan et al. to much higher SOCME values in a sulfur-containing emitter than in analogs without the sulfur atom present [37]. The |VSOC|2 values of 5CzBN and 5CzBP increased to 0.298 cm−2 and 0.267 cm−2, respectively, which are more than one hundred times higher than 2CzBN and

A sustainable strategy for the straightforward preparation of 2H-azirines and highly functionalized NH-aziridines from vinyl azides using a single solvent flow-batch approach

• Michael Andresini,
• Leonardo Degannaro and
• Renzo Luisi

Beilstein J. Org. Chem. 2021, 17, 203–209, doi:10.3762/bjoc.17.20

• olefins [13][14]. Aziridines are otherwise accessible from a variety of acyclic precursors [15][16][17], even stereoselectively [18][19][20], and through derivatization of 2H-azirines. The reactions using 2H-azirines as electrophiles proceed with several nitrogen, oxygen and sulfur nucleophiles, enabling

Deoxyfluorination of acyl fluorides to trifluoromethyl compounds by FLUOLEAD^®/Olah’s reagent under solvent-free conditions

• Yumeng Liang,
• Akihito Taya,
• Zhengyu Zhao,
• Norimichi Saito and
• Norio Shibata

Beilstein J. Org. Chem. 2020, 16, 3052–3058, doi:10.3762/bjoc.16.254

• carboxylic acids with sulfur tetrafluoride (SF4) at 120 to 150 °C in liquid hydrogen fluoride (HF) (Scheme 1c). Very recently, Mykhailiuk [28][29] improved the method to use SF4 for the deoxofluorination of carboxylic acids with or without HF in the gram scale (Scheme 1c). Although Mykhailiuk’s protocol is

• toxic sulfur tetrafluoride [32] and the explosive (diethylamino)sulfur trifluoride (DAST) [33]. Although the 2010 report by Umemoto provided a method for the deoxyfluorination of a wide variety of substrates, including alcohols, ketones, and even carboxylic acids to the mono-, di-, and trifluoromethyl

Metal-free nucleophilic trifluoromethylselenolation via an iodide-mediated umpolung reactivity of trifluoromethylselenotoluenesulfonate

• Kevin Grollier,
• Alexis Taponard,
• Arnaud De Zordo-Banliat,
• Emmanuel Magnier and
• Thierry Billard

Beilstein J. Org. Chem. 2020, 16, 3032–3037, doi:10.3762/bjoc.16.252

• ). Other solvents, which led also to satisfactory yields in the “sulfur series” were then tested. Acetonitrile did not improve the yield, however, a better one was obtained in THF (Table 1, entries 2 and 3). Interestingly, a shorter reaction time (4 h instead of 15 h) provided similar results (Table 1

• substitution. This is adequate with the observed results. Noteworthy, the supposed formation of I2 was strengthened by the appearance of a red-brown color of the reaction media which faded after the addition of sodium thiosulfate. As demonstrated in the sulfur series [49], the in situ formation of an alkyl

All-carbon [3 + 2] cycloaddition in natural product synthesis

• Zhuo Wang and
• Junyang Liu

Beilstein J. Org. Chem. 2020, 16, 3015–3031, doi:10.3762/bjoc.16.251

• take place. The use of noncyclic analogues did not give the cycloaddition product. It is suggested that the restricted rotational freedom of 151 and the related enforced conjugation of the sulfur lone pair may block certain undesired cation reactions. Cycloaddition product 154 was subjected to the

Controlled decomposition of SF₆ by electrochemical reduction

• Sébastien Bouvet,
• Bruce Pégot,
• Stéphane Sengmany,
• Erwan Le Gall,
• Eric Léonel,
• Anne-Marie Goncalves and
• Emmanuel Magnier

Beilstein J. Org. Chem. 2020, 16, 2948–2953, doi:10.3762/bjoc.16.244

• +/Fc. The exact number of electrons for the full consumption of sulfur hexafluoride was determined and this gas further quantitatively transformed into environmentally benign fluoride anion and sulfur by electrochemical reduction. Keywords: electroreduction; fluoride anion; redox potential; sulfur

• hexafluoride; Introduction Sulfur hexafluoride (SF6) is a fluorinated gas firstly identified in 1900 by Henry Moissan [1]. The strategy applied at industrial level to obtain SF6 uses sulfur in the presence of molecular fluorine. Sulfur hexafluoride possesses the particularity of being an inert gas both

• reactive, corrosive and toxic [12]. Recent and really impressive works were devoted to the decomposition of sulfur hexafluoride using stoichiometric or catalytic amounts of metals (Rh, Ni, Pt) [13][14][15][16]. Organic derivatives (phosphines or bipyridine) proved efficient tools for the selective

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

• synthesis of various types of sulfur containing heterocyclic compounds [43][44][45][46][47]. This gives some promise to the development of a general and efficient method for the synthesis of N-sulfonyl amidines of heteroaromatic acids based on the reaction of heterocyclic thioamides with higly electrophilic

• sulfonyl azides. With the purpose of the synthesis of heterocyclic N-sulfonyl amidines bearing various heteroatoms in the ring, namely nitrogen, sulfur and oxygen atoms, we have studied reactions of thioamides of 1,2,3-triazole-, isoxazole-, thiazolecarboxylic acids and 2,5-dithiocarbamoylpyridine with

• form can be explained by steric hindrance between the phenyl and the arylsulfonyl groups. Because of the observed evolution of nitrogen and sulfur in every reaction of heterocyclic thioamides and sulfonyl azides it is logic to propose the formation of a thiatriazole ring via [3 + 2] cycloaddition of

A novel and robust heterogeneous Cu catalyst using modified lignosulfonate as support for the synthesis of nitrogen-containing heterocycles

• Bingbing Lai,
• Meng Ye,
• Ping Liu,
• Minghao Li,
• Rongxian Bai and
• Yanlong Gu

Beilstein J. Org. Chem. 2020, 16, 2888–2902, doi:10.3762/bjoc.16.238

• acid-base titration and elemental analysis, respectively (Table 3). The results showed that the density of –SO3H determined by acid-base titration was much lower than that confirmed by elemental analysis, indicating that a portion of sulfur existed in the form of Cu complex and –SO3Na. Afterwards, the

Synthesis of purines and adenines containing the hexafluoroisopropyl group

• Viacheslav Petrov,
• Rebecca J. Dooley,
• Alexander A. Marchione,
• Elizabeth L. Diaz,
• Brittany S. Clem and
• William Marshall

Beilstein J. Org. Chem. 2020, 16, 2739–2748, doi:10.3762/bjoc.16.224

• equivalent of elemental sulfur (Scheme 1). A crude mixture of 2a and 2b (ratio 70:30) was isolated in 78% yield. Since the minor isomer 2b had a significantly higher solubility in hexane, washing of the crude mixture with hexane resulted in an enrichment of the major isomer 2a (ratio 2a/2b 95:5 after washing

• HFTA and imidazole. In this case, the reaction can proceed through the attack of a nitrogen atom of the imidazole ring at the carbon atom of the C=S bond, leading to the formation of the zwitterion B (Scheme 6). The transfer of a proton from the nitrogen atom to the sulfur atom leads to the formation

• of thiol C, which can lose sulfur, giving rise to the final product. Because of the unsymmetrical nature of substrate A, the attack on the C=S bond of HFTA proceeds by either nitrogen atom of the imidazole ring, resulting in the formation of two isomers for compounds 2–4 and 7. The highly selective

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

• . 250, 64293 Darmstadt, Germany 10.3762/bjoc.16.214 Abstract The synthesis and optoelectronic properties of novel S,N-heterotetracenes consisting of fused heterocyclic thiophene and pyrrole rings are presented. Tetracyclic and benzannulated derivatives with a varying number and sequence of sulfur and

• 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

• replacement of sulfur by nitrogen atoms in the tetra- and hexacyclic systems leads to a red-shift in absorption, a decrease in oxidation potential and energy gap. On the other hand, the replacement of a thiophene ring by benzene leads to the opposite effects. Keywords: Buchwald–Hartwig amination; Cadogan

Synthesis of 4-substituted azopyridine-functionalized Ni(II)-porphyrins as molecular spin switches

• Jannis Ludwig,
• Tobias Moje,
• Fynn Röhricht and
• Rainer Herges

Beilstein J. Org. Chem. 2020, 16, 2589–2597, doi:10.3762/bjoc.16.210

• that methoxy substitution (σ = −0.27) improved the spin switching efficiency in organic solvents to >98% in both directions [13]. However, the switching efficiency drops in protic solvents, particularly in water [3][14]. We now synthesized sulfur and carboxylic acid substituted record players aiming at

• porphyrin 22 and the disulfide 12, obviously because of catalyst poisoning by sulfur [32][33]. To circumvent these problems, protection groups were introduced. Protection with methyl 3-mercaptopropionate (15) [29] was successful, however, inhibition of the Suzuki reaction was observed. We assume an alkaline

Thermodynamic and electrochemical study of tailor-made crown ethers for redox-switchable (pseudo)rotaxanes

• Henrik Hupatz,
• Marius Gaedke,
• Hendrik V. Schröder,
• Julia Beerhues,
• Arto Valkonen,
• Fabian Klautzsch,
• Sebastian Müller,
• Felix Witte,
• Kari Rissanen,
• Biprajit Sarkar and
• Christoph A. Schalley

Beilstein J. Org. Chem. 2020, 16, 2576–2588, doi:10.3762/bjoc.16.209

• weaker hydrogen-bond-acceptor ability of the sulfur atoms incorporated in the TTFC8 crown ether ring [34][54]. NDIC8 also exhibits a comparably low binding energy, likely due to the increased ring size and the consequently weakened hydrogen-bonding pattern (Table 1, entry 11) [44]. However, NDIC8 and

• the binding data by ITC. The observed decrease of the binding energy with more sulfur atoms in the crown ether ring from DBC8 over TTFC8 to bisTTFC8 is consistent with a systematic study on thiacrown ethers [54]. Surprisingly, the increased Gibbs free binding energy ΔG0 for A1·BArF24 compared to A1

Synthesis of novel fluorinated building blocks via halofluorination and related reactions

• Attila Márió Remete,
• Tamás T. Novák,
• Melinda Nonn,
• Matti Haukka,
• Ferenc Fülöp and
• Loránd Kiss

Beilstein J. Org. Chem. 2020, 16, 2562–2575, doi:10.3762/bjoc.16.208

• transformation, and COOH→CF3 transformation), is also an important nucleophilic fluorination method [2][3][4][5][10][11][18]. The synthesis of fluorinated compounds via deoxyfluorination [21][22][23][24][25][26][27][28][29][30] or utilizing sulfur fluoride deoxyfluorinating reagents [31][32] is a highlighted

• topic. It is notable that halofluorination reactions applying sulfur fluoride deoxyfluorinating reagents as fluoride sources are practically unknown [33], but analogous reactions with α-fluoroamines (another class of deoxyfluorinating reagents) were reported [20]. As a result, our main aim was to

NMR Spectroscopy of supramolecular chemistry on protein surfaces

• Peter Bayer,
• Anja Matena and
• Christine Beuck

Beilstein J. Org. Chem. 2020, 16, 2505–2522, doi:10.3762/bjoc.16.203

• dispersion and more favorable relaxation properties compared to CH2 groups, so they are mostly used to observe the interactions of a protein with its binding partners. Especially methyl groups bound to a hetero atom like sulfur (in methionine) or nitrogen (e.g., in methylated lysine) have unique chemical

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

• section we will discuss the developments in heterosumanenes. 3.1 Synthesis of sulfur-doped sumanenes Although, the interest in the sumanene chemistry arise in 1993 when for the first time Mehta and co-workers reported the unsuccessful attempt towards the construction of this beautifully simple yet much

• treating the commercially available triphenylene derivative 152 with n-BuLi in the presence of tetramethylethylenediamine (TMEDA) to produce the hexalithiated intermediate which on further treatment with sulfur powder generated the compound 153 having 1,2-dithiin rings as well as one thiophene ring. Later

• sumanene-based trisulfone derivative 156 in the presence of hydrogen peroxide in AcOH as detailed in the Scheme 40. Liu et al. has revealed the functionalization of a sulfur-doped sumanene by means of perbromination followed by nucleophilic substitution as depicted in Scheme 41 [78]. They first performed

Photosensitized direct C–H fluorination and trifluoromethylation in organic synthesis

• Shahboz Yakubov and
• Joshua P. Barham

Beilstein J. Org. Chem. 2020, 16, 2151–2192, doi:10.3762/bjoc.16.183

• chemistry [175]. Despite the utility of (diethylamino)sulfur trifluoride (DAST) [176], morpholinosulfur trifluoride and tetrabutylammonium fluoride (TBAF) [4] as nucleophilic fluorine sources, the high reactivity of alternative electrophilic fluorine sources, such as fluoroxysulfates and hypofluorites [177

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

• form the oxazole ring and the sulfur end of the thiocyanate involves in the reaction resulting in the 2-aminothiazole ring. The mechanism for the formation of 4 may be similar to that suggested earlier [73]. Conclusion In conclusion, we have demonstrated selective routes for the synthesis of highly

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

• four-membered rings, while two lithium atoms, a sulfur atom, and three oxygen atoms form two six-membered rings. Because of the presence of C–Li and O–Li bonds in (2a)4·(THF)6, the dicarbanions are both C,C- and O,Li-dilithiated species. The C–Li, C–S, and O–Li bond lengths (Table 1) of the tetramer

• , electrostatic interaction with and charge polarization by the positively charged sulfur atom [56] and silicon atom [57], and negative nC–σ*SPh hyperconjugation [56][58]. The anions of (2a)4·(THF)6 and (2a)6·Li2O·(THF)6 adopt conformations around the carbon sulfur bond, which would allow for stabilization by

Synthesis of 3(2)-phosphonylated thiazolo[3,2-a]oxopyrimidines

• Ksenia I. Kaskevich,
• Anastasia A. Babushkina,
• Vladislav V. Gurzhiy,
• Dmitrij M. Egorov,
• Nataly I. Svintsitskaya and
• Albina V. Dogadina

Beilstein J. Org. Chem. 2020, 16, 1947–1954, doi:10.3762/bjoc.16.161

• -phosphonylated thiazolopyrimidine can be explained by the electron-withdrawing effect of the trifluoromethyl group in the starting 2-thiouracil. In contrast to 6-methyl- or 6-phenyl-2-thiouracil, where the nucleophilicity is localized on the sulfur atom, the presence of the electron-withdrawing CF3 group in 6

• sulfur atom [33][42][43][44][45][46]. Conclusion In conclusion, a series of phosphonylated thiazolo[3,2-a]oxopyrimidines was first synthesized by reacting unsubstituted and substituted 2-thiouracils with chloroethynylphosphonates. The main regularities of this reaction were revealed. In the case of 6

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

• ], (c) carbon–sulfur bond-forming reactions [9], (d) directed ortho-metalation and nucleophilic acyl substitution strategies [10], (e) Pd-catalyzed aminocarbonylation of aryl iodides, Suzuki–Miyaura and Sonogashira cross-coupling reactions [11][12][13], (f) Cu-catalyzed C–N coupling reactions [14], and

Natural dolomitic limestone-catalyzed synthesis of benzimidazoles, dihydropyrimidinones, and highly substituted pyridines under ultrasound irradiation

• Kumar Godugu,
• Venkata Divya Sri Yadala,
• Mohammad Khaja Mohinuddin Pinjari,
• Trivikram Reddy Gundala,
• Lakshmi Reddy Sanapareddy and
• Chinna Gangi Reddy Nallagondu

Beilstein J. Org. Chem. 2020, 16, 1881–1900, doi:10.3762/bjoc.16.156

• highly substituted pyridines when compared to the existing reported catalysts. Further, the expansion of the catalyst scope and the generality for the synthesis of other privileged nitrogen- and sulfur-based heterocycles is under progress in our laboratory. Experimental See Supporting Information File 1

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