Acid-catalyzed rearrangements in arenes: interconversions in the quaterphenyl series

• Sarah L. Skraba-Joiner,
• Carter J. Holt and
• Richard P. Johnson

Beilstein J. Org. Chem. 2019, 15, 2655–2663, doi:10.3762/bjoc.15.258

• through time-of-flight matrix assisted laser desorption ionization (MALDI–TOF–MS) mass spectrometry, using sulfur as a matrix. Suzuki–Miyaura coupling to form m,p’-quaterphenyl (13) [35]: 4-Biphenylboronic acid (0.18 g, 0.91 mmol) and 1 M K2CO3 (1.5 mL) were added to a 10 mL Pyrex microwave tube. 3

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

• ). When the group Y is OMe (6f), this shift is larger due to the higher EDG properties of MeO (λmax = 352 nm) and this is slightly increased with Y = OiPr (6g, λmax = 355 nm). The shift is highest for Y = NMe2 (6i, λmax = 387 nm). When the oxygen atom of 6f is replaced by a sulfur atom, the bathochromic

• shift of the π–π* band is also increased (6h, λmax = 373 nm, Table 3, Figure 4A). This high capacity of sulfur substituents to induce a bathochromic effect has already been reported in the azobenzene field [33]. The trans–cis photoisomerization for 3e, 4d, 6b and 6d–h in general gives a high percentage

Self-assembled coordination thioether silver(I) macrocyclic complexes for homogeneous catalysis

• Zhen Cao,
• Aline Lacoudre,
• Cybille Rossy and
• Brigitte Bibal

Beilstein J. Org. Chem. 2019, 15, 2465–2472, doi:10.3762/bjoc.15.239

• . These silver(I) complexes adopted similar structures in solution and in the solid state. As each sulfur atom in the ligand is prochiral, macrocycles L2M2 were obtained as mixtures of diastereoisomers, depending on the configurations of the sulfur atoms coordinated to silver cations. The X-ray structures

• silver(I) catalysts based on sulfur ligands were reported so far, although alkyl thioethers are soft σ-donor ligands such as crown thioethers that were largely developed as macrocyclic ligands for silver(I) [35][36][37][38][39][40][41][42][43]. Interestingly, depending on their design, these known silver

• prochiral sulfur atom of the ligand becomes asymmetric by coordination to silver(I). In absence of any chiral source, the complexes were obtained either as nonchiral coordination products with a center or an axis of symmetry (1a and 1c, with (R,S)–1 ligands) or as a racemic mixture (1d, with (R,R)–1 or (S,S

Current understanding and biotechnological application of the bacterial diterpene synthase CotB2

• Ronja Driller,
• Daniel Garbe,
• Norbert Mehlmer,
• Monika Fuchs,
• Keren Raz,
• Dan Thomas Major,
• Thomas Brück and
• Bernhard Loll

Beilstein J. Org. Chem. 2019, 15, 2355–2368, doi:10.3762/bjoc.15.228

• the structure of CotB2wt·Mg2+B·GGSDP are shown in gray. The GGSDP molecule is shown in black with the sulfur atom colored in yellow. The position of Mg2+B is identical in both structures. For clarity water molecules have been omitted. (B) View in panel A rotated by 30°. In addition to the motifs shown

Thermal stability of N-heterocycle-stabilized iodanes – a systematic investigation

• Andreas Boelke,
• Yulia A. Vlasenko,
• Mekhman S. Yusubov,
• Boris J. Nachtsheim and
• Pavel S. Postnikov

Beilstein J. Org. Chem. 2019, 15, 2311–2318, doi:10.3762/bjoc.15.223

• Supporting Information File 1) were observed at remarkable high Tpeak values (193.9–210.1 °C). Following these results, it has been intriguing to analyze the influence of the heteroatom in the heterocyclic moiety on the thermal decomposition process. The change of one nitrogen atom to sulfur as in thiazole

Recent advances in transition-metal-catalyzed incorporation of fluorine-containing groups

• Xiaowei Li,
• Xiaolin Shi,
• Xiangqian Li and
• Dayong Shi

Beilstein J. Org. Chem. 2019, 15, 2213–2270, doi:10.3762/bjoc.15.218

Synthesis and properties of sulfur-functionalized triarylmethylium, acridinium and triangulenium dyes

• Marco Santella,
• Eduardo Della Pia,
• Jakob Kryger Sørensen and
• Bo W. Laursen

Beilstein J. Org. Chem. 2019, 15, 2133–2141, doi:10.3762/bjoc.15.210

• functionalities were synthesized and their optical properties were studied. The sulfur functionalities were introduced by aromatic nucleophilic substitution of methoxy groups in triarylmethylium cations with ethanethiol followed by partial or full ring closure of the ortho positions with nitrogen or oxygen

• bridges leading to sulfur-functionalized acridinium, xanthenium or triangulenium dyes. For all the dye classes the sulfur functionalities are found to lead to intensely absorbing dyes in the visible range (470 to 515 nm), quite similar to known analogous dye systems with dialkylamino donor groups in place

• of the ethylthiol substituents. For the triangulenium derivatives significant fluorescence was observed (Φf = 0.1 to Φf = 0.3). Keywords: acridinium dyes; aromatic nucleophilic substitution; fluorescent dyes; sulfur-functionalized dyes; triangulenium dyes; triarylmethylium; Introduction The design

Friedel–Crafts approach to the one-pot synthesis of methoxy-substituted thioxanthylium salts

• Kenta Tanaka,
• Yuta Tanaka,
• Mami Kishimoto,
• Yujiro Hoshino and
• Kiyoshi Honda

Beilstein J. Org. Chem. 2019, 15, 2105–2112, doi:10.3762/bjoc.15.208

• hexafluorophosphoric acid (Scheme 1a and 1b) [3][4][9][10], oxidation of thioxanthene in the presence of PbO2 followed by dehydration by tetrafluoroboric acid [1], the reaction of 4,4’-bis(dimethylamino)diphenylmethane with sulfur in the presence of ZnCl2 [11], and the ring-closure reaction of diaryl sulfide in the

• sulfur were performed with a CHNOS Elemental Analyzer Vario ELIII Elemental (Elementar Co.). Column chromatography was carried out with Cicareagent silica gel 60 N (spherical, particle size 63–210 mm). Thin-layer chromatography (TLC) was carried out with Merck TLC plates with silica gel 60 F254. Unless

Synthesis of benzo[d]imidazo[2,1-b]benzoselenoazoles: Cs₂CO₃-mediated cyclization of 1-(2-bromoaryl)benzimidazoles with selenium

• Mio Matsumura,
• Yuki Kitamura,
• Arisa Yamauchi,
• Yoshitaka Kanazawa,
• Yuki Murata,
• Tadashi Hyodo,
• Kentaro Yamaguchi and
• Shuji Yasuike

Beilstein J. Org. Chem. 2019, 15, 2029–2035, doi:10.3762/bjoc.15.199

• reaction of 1a with sulfur or tellurium powder did not proceed, and the starting material 1a was recovered (Table 1, entries 17 and 18). The best result was obtained when 1a and Se powder were treated with Cs2CO3 in DMF under an argon atmosphere at 150 °C. The benzimidazo[2,1-b]benzoselenoazole product 2a

Synthesis and anion binding properties of phthalimide-containing corona[6]arenes

• Meng-Di Gu,
• Yao Lu and
• Mei-Xiang Wang

Beilstein J. Org. Chem. 2019, 15, 1976–1983, doi:10.3762/bjoc.15.193

• and electron-neutral organic guests [22][23][24][25][26][27][28][29][30][31]. In our previous study we have developed an efficient protocol to synthesize oxygen and sulfur-linked corona[m]arene[n]tetrazines from aromatic diol and dithiol derivatives and 3,6-dichlorotetrazine, respectively, in a simply

Installation of -SO₂F groups onto primary amides

• Jing Liu,
• Shi-Meng Wang,
• Njud S. Alharbi and
• Hua-Li Qin

Beilstein J. Org. Chem. 2019, 15, 1907–1912, doi:10.3762/bjoc.15.186

• Sciences, Faculty of Science, King Abdulaziz University, Jeddah, Saudi Arabia 10.3762/bjoc.15.186 Abstract A protocol of SO2F2-mediated installation of sulfonyl fluoride onto primary amides has been developed providing a new portal to sulfur(VI) fluoride exchange (SuFEx) click chemistry. The generated

• molecules contain pharmaceutically important amide and -SO2F moieties for application in the discovery of new therapeutics. Keywords: N-fluorosulfonyl amides; primary amides; sulfuryl fluoride (SO2F2); Introduction Sulfur(VI) fluoride exchange (SuFEx) is a new class of click chemistry developed by

Transient and intermediate carbocations in ruthenium tetroxide oxidation of saturated rings

• Manuel Pedrón,
• Laura Legnani,
• Maria-Assunta Chiacchio,
• Pierluigi Caramella,
• Tomás Tejero and
• Pedro Merino

Beilstein J. Org. Chem. 2019, 15, 1552–1562, doi:10.3762/bjoc.15.158

• tetrahydrofuran [45] have been experimentally reported as well as the oxidation of N-acylpyrrolidines to the corresponding lactams [46]. Admittedly, the oxidation of tetrahydrothiophene has been approached only computationally since in that case the sulfur atom would be more easily oxidized. Since the general

A novel three-component reaction between isocyanides, alcohols or thiols and elemental sulfur: a mild, catalyst-free approach towards O-thiocarbamates and dithiocarbamates

• András György Németh,
• György Miklós Keserű and
• Péter Ábrányi-Balogh

Beilstein J. Org. Chem. 2019, 15, 1523–1533, doi:10.3762/bjoc.15.155

• been developed between isocyanides, sulfur and alcohols or thiols under mild reaction conditions to afford O-thiocarbamates and dithiocarbamates in moderate to good yields. The one-pot reaction cascade involves the formation of an isothiocyanate intermediate, thus a catalyst-free synthesis of

• isothiocyanates, as valuable building blocks from isocyanides and sulfur is proposed, as well. The synthetic procedure suits the demand of a modern organic chemist, as it tolerates a wide range of functional groups, it is atom economic and easily scalable. Keywords: ditihiocarbamate; elemental sulfur

• afford isothiocyanate and harmless urea [63][64][65], but one should note that the instability of the nitrile oxides leads to many byproducts, turning this approach less attractive. The synthesis of isothiocyanates starting from isonitriles involves sulfur-containing reagents such as thallium

Fluorine-containing substituents: metabolism of the α,α-difluoroethyl thioether motif

• Andrea Rodil,
• Alexandra M. Z. Slawin,
• Nawaf Al-Maharik,
• Ren Tomita and
• David O’Hagan

Beilstein J. Org. Chem. 2019, 15, 1441–1447, doi:10.3762/bjoc.15.144

• -difluoroethyl thioether motif to explore further its potential as a substituent for bioactives discovery chemistry. Incubation of two aryl–SCF2CH3 ethers with the model yeast organism Cunninghamella elegans, indicates that the sulfur of the thioether is rapidly converted to the corresponding sulfoxide, and then

• methods developed for the synthesis of enantiomerically enriched aryl fluoroalkyl sulfoxides, however, this appears to be the first enzymatic approach [23][24][25]. Although the fungus was able to both oxidise the sulfur and demethylate the para-methoxy group of 4, there was no obvious presence of novel

Selenophene-containing heterotriacenes by a C–Se coupling/cyclization reaction

• Pierre-Olivier Schwartz,
• Sebastian Förtsch,
• Astrid Vogt,
• Elena Mena-Osteritz and
• Peter Bäuerle

Beilstein J. Org. Chem. 2019, 15, 1379–1393, doi:10.3762/bjoc.15.138

• -Wolff-Straße 13, 29699 Bomlitz, Germany 10.3762/bjoc.15.138 Abstract A new novel family of tricyclic sulfur and/or selenium-containing heterotriacenes 2–4 with an increasing number of selenium (Se) atoms is presented. The heterotriacene derivatives were synthesized in multistep synthetic routes and the

• heteroatoms such as nitrogen or sulfur represent encouraging alternatives to PAHs providing manageable electronic properties and increased chemical stability [4][5]. In this respect, series of heteroacenes consisting of fused five-membered heterocycles such as thienoacenes [6][7] or S,N-heteroacenes [8] were

• reinvestigated the synthesis of DTT 1 by using a Cu-catalyzed C–S cross-coupling reaction with potassium sulfide (K2S) as sulfur source [29]. The best results for this C–S ring-closure reaction were achieved by reacting 3,3’-diiodo-2,2’-bithiophene (5) [30] with the system K2S and copper iodide (CuI) as catalyst

Formation of an unexpected 3,3-diphenyl-3H-indazole through a facile intramolecular [2 + 3] cycloaddition of the diazo intermediate

• Andrew T. King,
• Hugh G. Hiscocks,
• Lidia Matesic,
• Mohan Bhadbhade,
• Roger Bishop and
• Alison T. Ung

Beilstein J. Org. Chem. 2019, 15, 1347–1354, doi:10.3762/bjoc.15.134

• -arylsulfonyl fluoride 3 was 95% intact in rat plasma after 120 min at 37 °C [5]. This indicated that the combination of electron-donating effects and steric hindrance of isopropyl groups provide greater stability to a sulfur–fluorine bond than groups that can only provide the steric hindrance in the molecule

• [6]. To further investigate the stability of 18F-sulfonyl fluorides, the sterically hindered compound 4 was selected with enough steric bulk in the 2,6-position. The initial chlorosulfonylation reaction was performed using 1,4-diazabicyclo[2.2.2]octane bis(sulfur dioxide) adduct (DABSO) as a source

• of sulfur dioxide. DABSO was selected as it would provide a facile method and is a safer alternative to sulfur dioxide gas [7][8][9][10]. The target molecule 4 was envisaged via the diazonium salt of 5 [11] and 6 and was a modification of the microfluidic flow reaction reported by Malet-Sanz et al

Host–guest interactions between p-sulfonatocalix[4]arene and p-sulfonatothiacalix[4]arene and group IA, IIA and f-block metal cations: a DFT/SMD study

• Valya K. Nikolova,
• Cristina V. Kirkova,
• Silvia E. Angelova and
• Todor M. Dudev

Beilstein J. Org. Chem. 2019, 15, 1321–1330, doi:10.3762/bjoc.15.131

• ., acetaldehyde – ethanal, CH3CHO) are required in condensation reactions with resorcinol and pyrogallol [1]. Thiacalixarenes are macrocycles (or cyclic oligomers) based on a condensation of the same phenol derivatives and sulfur [2]. They are characterized by a larger cavity size than the conventional

• calixarenes (with the same repeating units). The sulfur functionalities are stated to provide better metal complexation [3]. Unmodified calixarenes and thiacalixarenes are sparingly soluble, have chemical and thermal stability and act as host molecules as they possess cavities, but their inclusion properties

• tilted to one of the C[4]A walls (Figure 3). The optimization of Na+, Mg2+ and La3+-complexes with TC[4]A was initiated from the respective optimized [C[4]A−M](4−n)− geometry where the CH2 groups were replaced by sulfur atoms. The Rb+, Sr2+ and Lu3+ complexes with TC[4]A were modeled from the optimized

Synthesis of aryl cyclopropyl sulfides through copper-promoted S-cyclopropylation of thiophenols using cyclopropylboronic acid

• Emeline Benoit,
• Ahmed Fnaiche and
• Alexandre Gagnon

Beilstein J. Org. Chem. 2019, 15, 1162–1171, doi:10.3762/bjoc.15.113

• ). For instance, the proton alpha to the sulfur can be removed by a strong base such as butyllithium, resulting in the cyclopropyllithium species 2. This carbanion can then react with alkyl halides to provide the corresponding alkylated species 3 which can then be opened up by treatment with mercuric

Multicomponent reactions (MCRs): a useful access to the synthesis of benzo-fused γ-lactams

• Edorta Martínez de Marigorta,
• Jesús M. de Los Santos,
• Ana M. Ochoa de Retana,
• Javier Vicario and
• Francisco Palacios

Beilstein J. Org. Chem. 2019, 15, 1065–1085, doi:10.3762/bjoc.15.104

• . Nevertheless, most of the known multicomponent methods for the preparation of 2-oxindoles are based on the use of N-aryl amides as the main partner of the reagent pool. Wu et al. reacted N-(2-iodoaryl)acrylamides 113, DABCO·(SO2)2 (69, also known as DABSO) as a surrogate of sulfur dioxide and hydrazine 114 in

• hydrazine 114 and sulfur dioxide (Scheme 33). Rearrangement of the so-obtained intermediate 119, through radical 120, would provide oxindole 115. The same acrylamide 113 (R1 = H) has been recently used in another multicomponent synthesis along with CO (23) and benzodiazepine derivative 121 under palladium

• prepared by another type of three-component approach, in this case under copper catalysis (Scheme 35) [112]. The partners of the reaction are N-(arylsulfonyl)acrylamides 123, aryldiazonium tetrafluoroborates 68 and DABCO·(SO2)2 (69), as a source of sulfur dioxide. In this way, sulfonated oxindoles 124 are

Diaminoterephthalate–α-lipoic acid conjugates with fluorinated residues

• Leon Buschbeck,
• Aleksandra Markovic,
• Gunther Wittstock and
• Jens Christoffers

Beilstein J. Org. Chem. 2019, 15, 981–991, doi:10.3762/bjoc.15.96

• sulfur atoms (Table 2). The peak at 285.5 eV (SAM 3 and SAM 7) corresponds to the carbon atoms with a higher binding energy due to the bond to one more electronegative atom (C−O and C−N) [53]. Figure 2 and Figure 3 show further C 1s peaks lying at binding energies of 288.5 eV, 290.6 eV, and 292.6 eV (SAM

• ), which is expected from the molecular structure of compounds 3 and 7, may be caused by residual adsorbed water that also causes an O 1s component at 533.0–533.5 eV [57][58]. The main doublet in the S 2p spectra of both monolayers at 161.8 eV corresponds to sulfur bound to gold [59]. Although, S 2p

An efficient and concise access to 2-amino-4H-benzothiopyran-4-one derivatives

• Peng Li,
• Yongqi Wu,
• Tingting Zhang,
• Chen Ma,
• Ziyun Lin,
• Gang Li and
• Haihong Huang

Beilstein J. Org. Chem. 2019, 15, 703–709, doi:10.3762/bjoc.15.65

• -imidazolylbenzothiopyranones [10]. It is well known that the sulfide, sulfinyl and sulfonyl groups are generally used as the leaving group for the synthesis of 2-substituted 4H-chromen-4-ones [11][12][13][14][15][16][17][18][19][20][21][22]. Due to the higher electronegativity of the oxygen atom compared to the sulfur atom

Selectivity in multiple multicomponent reactions: types and synthetic applications

• Ouldouz Ghashghaei,
• Francesca Seghetti and
• Rodolfo Lavilla

Beilstein J. Org. Chem. 2019, 15, 521–534, doi:10.3762/bjoc.15.46

• connected through long linear alkyl chains. Representative examples include polymerizations using Biginelli [12], Passerini [13], Ugi [14], metal-catalyzed MCRs [15], and reactive combinations involving an alkyne-sulfonyl azide nucleophile [16] and sulfur, amines and isocyanides [17] (Scheme 3). An

• polymerizations; E) alkyne-sulfonylazide-alcohol interactions; F) sulfur-amine-isocyanide combination. Concept of multicomponent macrocyclization. Supramolecular structures out of MMCR macrocyclizations. Macrocyclization by MMCRs. A) Staudinger MCR; B) boronic-imine MCR. Selective Sequential MMCRs. A and B) MCRs

Design of indole- and MCR-based macrocycles as p53-MDM2 antagonists

• Constantinos G. Neochoritis,
• Maryam Kazemi Miraki,
• Eman M. M. Abdelraheem,
• Ewa Surmiak,
• Tryfon Zarganes-Tzitzikas,
• Beata Łabuzek,
• Tad A. Holak and
• Alexander Dömling

Beilstein J. Org. Chem. 2019, 15, 513–520, doi:10.3762/bjoc.15.45

• bear a heteroatom in the 4-position as oxygen or sulfur (Y = O, S, Scheme 2) were employed in order to enhance the diversity of our macrocycles [4]. Thus, in a parallel way, we readily synthesized 12 different amino acids which were subsequently subjected to the Ugi macrocyclization. After quite some

• -pocket as shown by our docking studies (Figure 1A,B, Figure S4 in Supporting Information File 1). Thus, extending our previous work [13], the Leu26 subpocket was probed by utilizing the different ring sizes and the different heteroatoms (oxygen or sulfur) of our macrocyclic library. In addition, the

• influence of the chlorine atom in the 6-position of the indole ring (Figure 1C) was examined. Macrocycles 2a–j consist of an oxygen linker whereas 2g–j bear also a chlorine atom in the 6-position in the indole ring. Macrocycles 2k–p incorporate both a sulfur linker and the chlorine on the indole ring

Synthesis and selected transformations of 2-unsubstituted 1-(adamantyloxy)imidazole 3-oxides: straightforward access to non-symmetric 1,3-dialkoxyimidazolium salts

• Grzegorz Mlostoń,
• Małgorzata Celeda,
• Katarzyna Urbaniak,
• Marcin Jasiński,
• Vladyslav Bakhonsky,
• Peter R. Schreiner and
• Heinz Heimgartner

Beilstein J. Org. Chem. 2019, 15, 497–505, doi:10.3762/bjoc.15.43

• . Deprotonation of the latter with triethylamine in the presence of elemental sulfur allows the in situ generation of the corresponding imidazol-2-ylidene, which traps elemental sulfur yielding a 1,3-dihydro-2H-imidazole-2-thione as the final product. Keywords: alkoxyamines; imidazole N-oxides; imidazolium salts

• ; nucleophilic carbenes; sulfur transfer reaction; Introduction Imidazole N-oxides constitute a practically valuable class of five-membered aromatic N-heterocycles [1][2][3][4][5]. The subclass of 2-unsubstituted imidazole N-oxides 1 with diverse substituents located at N(1), C(4), and C(5) is of special

• -aromatization of the imidazole ring. The same mechanism governs sulfur-transfer reactions with cycloaliphatic thioketones yielding the corresponding imidazole-2-thiones [13]. The isomerization of N-oxides 1 into the corresponding imidazol-2-ones can be easily performed by treatment with acetic anhydride at room

Aqueous olefin metathesis: recent developments and applications

• Valerio Sabatino and
• Thomas R. Ward

Beilstein J. Org. Chem. 2019, 15, 445–468, doi:10.3762/bjoc.15.39

• . Remakably, no conversion was observed in the absence of MgCl2, which prevents the non-productive binding of the amino acid side chains to ruthenium. The authors suggested that the positive effect of allyl sulfides may be due to the coordination of the sulfur atom to the ruthenium center, favoring the