Copper-promoted/copper-catalyzed trifluoromethylselenolation reactions

• Clément Ghiazza and
• Anis Tlili

Beilstein J. Org. Chem. 2020, 16, 305–316, doi:10.3762/bjoc.16.30

• form C(sp)–SeCF3 bonds (Scheme 3) [18]. Therein, Dess–Martin periodinane (DMP) was used as the oxidant and potassium fluoride as the base, and the reactions were performed at room temperature in DMF as the solvent. The desired compounds were obtained in moderate to very good yields. Both electron

• 2003. Therein, the association of the Ruppert–Prakash reagent with ammonium fluoride in the presence of a slight excess of Se allowed the facile synthesis of Me4NSeCF3 (Scheme 9) [26]. Today, Me4NSeCF3 is routinely used by several research groups. In the past five years, this stable and easy-to-handle

• tandem formation of C–Se and Se–fluoroalkyl bonds have emerged in the last five years. In 2014, Hor and Weng reported the trifluoromethylselenolation of (hetero)aryl iodides and alkyl bromides with the Ruppert–Prakash reagent, TMSCF3, elemental selenium, potassium fluoride, and silver carbonate under

The use of isoxazoline and isoxazole scaffolding in the design of novel thiourea and amide liquid-crystalline compounds

• Itamar L. Gonçalves,
• Rafaela R. da Rosa,
• Vera L. Eifler-Lima and
• Aloir A. Merlo

Beilstein J. Org. Chem. 2020, 16, 175–184, doi:10.3762/bjoc.16.20

• gravimetric analysis (TGA) due to the possibility of hydrogen fluoride release in the system and the damage caused to the TGA. Relative to the isoxazole series, the thermal stability of two amides and one thiourea was assessed by TGA. Amides were found to be more stable than thioureas, where both amides, 20

A photochemical determination of luminescence efficiency of upconverting nanoparticles

• Baptiste Amouroux,
• Clément Roux,
• Jean-Claude Micheau,
• Fabienne Gauffre and
• Christophe Coudret

Beilstein J. Org. Chem. 2019, 15, 2671–2677, doi:10.3762/bjoc.15.260

• ], drug uncaging [11] to photodynamic therapy [12] and optogenetics [13][14]. Inorganic lanthanide based-UCNPs are classically formulated as a mixed fluoride NaREF4. Here, RE stands for a cocktail of trivalent rare-earth metal ions containing mostly photophysically inert metals (Y, Gd) and a few percent

• File 1) [29]. Briefly, key points are: (i) the in situ preparation of metal oleate from their corresponding chloride, (ii) the introduction of the sodium and fluoride ions as two methanol solutions of respectively NaOH and NH4F via separate syringe pumps (according to Zhai et al. [30]) and, after

Arylisoquinoline-derived organoboron dyes with a triaryl skeleton show dual fluorescence

• Vânia F. Pais,
• Tristan Neumann,
• Ignacio Vayá,
• M. Consuelo Jiménez,
• Abel Ros and
• Uwe Pischel

Beilstein J. Org. Chem. 2019, 15, 2612–2622, doi:10.3762/bjoc.15.254

• of 0.2–0.4, reaching in some cases values as high as 0.5–0.6. Laser-flash photolysis provided evidence for the existence of excited triplet states. The dyes form fluoroboronate complexes with fluoride anions, leading to the observation of the quenching of the long-wavelength emission band and

• , boron with sp2 hybridization, such as in triarylboranes, offers the possibility to modulate fluorescence properties by the addition of Lewis bases (e.g., fluoride ions [27][28][29][30][31]) or by exploring the electron-accepting properties of the boron, including charge-transfer and photoinduced

• , we extended our previously reported arylisoquinoline-derived organoboron dye platform with an additional axially linked aryl residue (see structures 16–19 in Figure 1) in the expectation to modulate the fluorescence properties and fluoride response of these dyes. The additional aryl residues allow

Chemical synthesis of the pentasaccharide repeating unit of the O-specific polysaccharide from Escherichia coli O132 in the form of its 2-aminoethyl glycoside

• Debasish Pal and
• Balaram Mukhopadhyay

Beilstein J. Org. Chem. 2019, 15, 2563–2568, doi:10.3762/bjoc.15.249

• fluoride in THF [17] to give the 6-hydroxy compound 8 in 90% yield. It was then benzoylated using BzCl in pyridine [18] with a catalytic amount of DMAP to furnish the completely protected donor 9 in 90% yield. Glycosylation of donor 9 with disaccharide acceptor 5 through activation of the thioglycoside

Probing of local polarity in poly(methyl methacrylate) with the charge transfer transition in Nile red

• Aydan Yadigarli,
• Qimeng Song,
• Sergey I. Druzhinin and
• Holger Schönherr

Beilstein J. Org. Chem. 2019, 15, 2552–2562, doi:10.3762/bjoc.15.248

• ][66] might be caused by remaining traces of solvent from PMMA solution (toluene) [66] in close vicinity to NR molecules, similar to results for NR in poly(vinylidene fluoride) films cast from dimethyl sulfoxide [15]. This notion is supported by fluorescence maxima (λf) of NR in PMMA at the excitation

Ultrafast processes triggered by one- and two-photon excitation of a photochromic and luminescent hydrazone

• Alessandro Iagatti,
• Baihao Shao,
• Alberto Credi,
• Barbara Ventura,
• Ivan Aprahamian and
• Mariangela Di Donato

Beilstein J. Org. Chem. 2019, 15, 2438–2446, doi:10.3762/bjoc.15.236

• small portion of the fundamental laser output radiation on a 2 mm thick calcium fluoride window. Pump-probe delays were introduced by sending the probe beam through a motorized stage. Multichannel detection was achieved by sending the white light continuum after passing through the sample to a flat

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

• the transfer form of fluorine, there are three general strategies for constructing C–F bonds: nucleophilic, electrophilic and radical fluorination (Scheme 1) [22]. In nucleophilic fluorination reactions, the fluoride anion (F−) or a derivative thereof, such as tetrafluoroborate (BF4−), is the fluorine

• source and behaves as a nucleophile. The electrophile, such as an alkyl chain or an aryl ring with halides or sulfonates, reacts with the fluoride source (Scheme 1a). On the other hand, in the electrophilic fluorination, the nucleophile may be a carbon anion (e.g., Grignard reagent), a compound with

• that the allylic fluorination was achieved by an SN2-type attack of fluoride on an electrophilic Pd(II)-allyl intermediate. One year later, the same author extended this method to a highly regio- and enantioselective fluorination of acyclic allylic chlorides. Compared to the previous process, this

1,2,3-Triazolium macrocycles in supramolecular chemistry

• Mastaneh Safarnejad Shad,
• Pulikkal Veettil Santhini and
• Wim Dehaen

Beilstein J. Org. Chem. 2019, 15, 2142–2155, doi:10.3762/bjoc.15.211

• changes in the CDCl3 solution of anionic species (Figure 3). The receptor 1a has shown remarkable affinity toward fluoride ion with an association constant of 560 M−1 followed by Cl− > Br− > I− > CH3COO− with the affinity range of 5.6 × 102 to 6.0 × 101 M−1 but no binding was observed with the H2PO4− ion

• this receptor for binding strongly to the anionic species. Among all of the tested negatively-charged ions such as halides and oxoanions, receptor 9 recognizes iodide and bromide stronger than chloride, fluoride, acetate and sulfate in a 9:1 DMSO-d6/D2O solvent mixture. The highest displayed binding

A review of the total syntheses of triptolide

• Xiang Zhang,
• Zaozao Xiao and
• Hongtao Xu

Beilstein J. Org. Chem. 2019, 15, 1984–1995, doi:10.3762/bjoc.15.194

• mixture of 51 and 52, subsequent Pd/C-catalyzed hydrogenation and tetrabutylammonium fluoride (TBAF)-mediated desilylation yielding the desired tricyclic 54 (83% yield, 98% ee). Overall, the known intermediate 7-oxotriptophenlide 59 was obtained in an efficient, elegant and scalable way in 10 steps with

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

• ][15][16][17][18][19]. Among all the developed S(VI)–F species, sulfonyl fluoride (RSO2F) was specifically recognized as unique scaffold for covalent protein inhibitors and biological probes with the affinity-driven activation for forming covalent linkages with the amino acid residues of protein

Synthesis and biological evaluation of truncated derivatives of abyssomicin C as antibacterial agents

• Leticia Monjas,
• Peter Fodran,
• Johanna Kollback,
• Carlo Cassani,
• Thomas Olsson,
• Maja Genheden,
• D. G. Joakim Larsson and
• Carl-Johan Wallentin

Beilstein J. Org. Chem. 2019, 15, 1468–1474, doi:10.3762/bjoc.15.147

• ). Treatment of 18 and 19 with Hoveyda–Grubbs second generation catalyst in refluxing 1,2-dichloroethane afforded the ring-closing metathesis products 20 and 21 in 62% and 45% yield, respectively. Deprotection of the TBDMS group using tetrabutylammonium fluoride followed by final Dess–Martin oxidation gave the

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

• context, the potential for P450 oxidation at sulphur is the most obvious metabolic vulnerability, and also hydrolytic susceptibility to release fluoride. We chose to explore the metabolism of aryl α,α-difluoroethyl thioethers 4 and 5 by Cunninghamella elegans as representative compounds of this class

• was isolated by HPLC. This was identified as 4-acetoxyphenol (15). Aryl ether demethylation remains highly active, but unlike the α,α-difluoroethyl thioethers 4 and 5, the oxygen ether is vulnerable to hydrolytic fluoride release. Oxygen ether 14 is particularly labile, and the incubation proceeds to

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

• in acetonitrile at 140 °C in a Schlenck tube to give DTT 1 in 66% yield. In the same way, trimethylsilyl (TMS)-protected diiodobithiophene 6 [31] gave 2,6-bis(trimethylsilyl)dithienothiophene 7 [32] in 73% yield, which was subsequently deprotected by tetrabutylammonium fluoride (TBAF) to form target

• ), tetrabutylammonium fluoride, selenourea, and copper oxide nanoparticles were purchased from Sigma-Aldrich. n-Butyllithium in n-hexane (1.6 M) was purchased from Acros Organics, selenophene from TCI, 3-bromothiophene from Fluorochem, potassium thioacetate from Alfa Aesar, potassium sulfide from Caesar & Loretz, and

• with literature [32]. Dithieno[3,2-b:2',3'-d]thiophene (DTT, 1) prepared from 7. To a solution of 2,6-bis(trimethylsilyl)dithieno[3,2-b:2',3'-d]thiophene (7, 92 mg, 0.27 mmol) in THF (2 mL) a solution of tetrabutylammonium fluoride trihydrate (184 mg, 0.6 mmol) in 1 mL THF was added. The mixture was

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

• [4][5]. Stability and radiochemical improvements were investigated by Matesic et al. [5]. For instance, electron-donating 18F-arylsulfonyl fluoride 1 was >98% stable in the buffer at 3 h, while the electron-withdrawing compound 2 was only 8% stable [5] (Figure 1). The more sterically hindered 18F

• -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

Synthesis of dipolar molecular rotors as linkers for metal-organic frameworks

• Sebastian Hamer,
• Fynn Röhricht,
• Marius Jakoby,
• Ian A. Howard,
• Xianghui Zhang,
• Christian Näther and
• Rainer Herges

Beilstein J. Org. Chem. 2019, 15, 1331–1338, doi:10.3762/bjoc.15.132

• . We interpret these data as the lower limits of the rotational barriers in a MOF environment. Interactions with other linkers or neighbouring dipoles probably will increase the barriers. The dipole moments of the cyano-substituted rotors are considerably higher than those with fluoride substitution

• . The annelated thiadiazole ring is rather electron withdrawing and reduces the dipole moment in combination with fluoride substitution to almost zero. Compound 5 in relation to its size has an exceptionally high dipole moment of 10.1 D; thus being in the same range as 1,2-dicyano-4,5-diaminobenzene of

• acid 1 using cesium fluoride under a carbon dioxide atmosphere. Difluoro- and dicyanobenzothiadiazole compounds 2 and 3 Substituted benzothiadiazole derivatives are well studied in the literature and are of great interest in organic photovoltaics and electronics. As there are no reports of such

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

• temperatures [18]. In addition, an electron-withdrawing group (EWG) must be present on the aryl fluoride 16 for the SNAr reaction to proceed. Aryl cyclopropyl sulfides can also be accessed by the addition of thiophenols 14 to cyclopropenes 18 (Scheme 2c) [19][20] or to exo-methylenecyclopropanes 20 (Scheme 2d

Design of a double-decker coordination cage revisited to make new cages and exemplify ligand isomerism

• Sagarika Samantray,
• Sreenivasulu Bandi and
• Dillip K. Chand

Beilstein J. Org. Chem. 2019, 15, 1129–1140, doi:10.3762/bjoc.15.109

• compound 6a: (Δδ = 1.91, 1.01 and 1.69 ppm for Ha, Hb and Hf, respectively), and (iii) the two Br− encapsulated compound 7a: (Δδ = 2.24, 1.02 and 1.74 ppm for Ha, Hb and Hf, respectively) are in line with the expectation. Although fluoride (F–) could replace NO3– in 4a to afford complex 5a, the complex 5a

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

• also been prepared in situ and used for a three-component transition-metal-free synthesis of phthalimides 79 induced by fluoride (Scheme 23) [102]. The reaction makes use of 2-(trimethylsilyl)aryl triflates 77, isocyanides 42 and CO2 (78), and takes place in acetonitrile as solvent and without the need

• formed by a concerted pathway. Then the fluoride induced ring opening and subsequent cyclization of intermediate 84 would generate phthalimide 79. Although most multicomponent reactions leading to isoindolinones make use of benzoic acid derivatives as one of the starting components, in a few

SO₂F₂-mediated transformation of 2'-hydroxyacetophenones to benzo-oxetes

• Revathi Lekkala,
• Ravindar Lekkala,
• Balakrishna Moku,
• K. P. Rakesh and
• Hua-Li Qin

Beilstein J. Org. Chem. 2019, 15, 976–980, doi:10.3762/bjoc.15.95

• catalyst-free novel and efficient methodology for the challenging synthesis of benzo-oxetes from 2'-hydroxyacetophenones mediated by sulfuryl fluoride (SO2F2) gas has been realized. The combination of 2'-hydroxyacetophenones and SO2F2 furnishes synthetically challenging benzo-oxetanes in moderate to

• excellent yields. The highlight of this work is the design and synthesis of strained four-membered oxete rings. Keywords: benzo-oxetes; 2'-hydroxyacetophenones; sulfuryl fluoride; Introduction Oxetanes are versatile elements in drug discovery and synthesis [1][2], and represent important moieties in some

• nature has afforded opportunities for the discovery of new transformations. Previous reports on the synthesis of substituted oxetanes from ketones described the requirement of chiral reagents or catalysts [11][12][13][14][22][23][24]. Gaseous sulfuryl fluoride (SO2F2) widely has been utilized as a

Tuning the stability of alkoxyisopropyl protection groups

• Zehong Liang,
• Henna Koivikko,
• Mikko Oivanen and
• Petri Heinonen

Beilstein J. Org. Chem. 2019, 15, 746–751, doi:10.3762/bjoc.15.70

• conditions used to remove benzoyl protecting groups and toward tetrabutylammonium fluoride used to remove the tert-butyldimethylsilyl (TBS) protection. The products could be purified by silica gel column chromatography without degradation when 0.5% triethylamine was added to the eluent. Hydrolytic stability

The LANCA three-component reaction to highly substituted β-ketoenamides – versatile intermediates for the synthesis of functionalized pyridine, pyrimidine, oxazole and quinoxaline derivatives

• Tilman Lechel,
• Roopender Kumar,
• Mrinal K. Bera,
• Reinhold Zimmer and
• Hans-Ulrich Reissig

Beilstein J. Org. Chem. 2019, 15, 655–678, doi:10.3762/bjoc.15.61

• alternative to methoxyallene is the 2-(trimethylsilyl)ethoxy-substituted allene. The 2-(trimethylsilyl)ethyl substituent can be removed from the products either by fluoride or acid treatment under mild conditions. Again, there were no great differences in the performance of this component compared to

• purified and characterized or, for further transformations, the crude products are directly converted into the corresponding nonaflates by deprotonation with sodium hydride and treatment with 1-nonafluorobutanesulfonyl fluoride (NfF). Scheme 13 shows two examples, PM52 and PM54 that are ready for palladium

Cyclopropene derivatives of aminosugars for metabolic glycoengineering

• Jessica Hassenrück and
• Valentin Wittmann

Beilstein J. Org. Chem. 2019, 15, 584–601, doi:10.3762/bjoc.15.54

Conformational signature of Ishikawa´s reagent using NMR information from diastereotopic fluorines

• Laize A. F. Andrade,
• Lucas A. Zeoly,
• Rodrigo A. Cormanich and
• Matheus P. Freitas

Beilstein J. Org. Chem. 2019, 15, 506–512, doi:10.3762/bjoc.15.44

• incoming fluoride becomes magnetically more shielded than the fluorine not involved in such an interaction. Because the positioning of neighboring groups relative to the diastereotopic fluorines (NEt2 and CHFCF3 groups), the conformational preferences of Ishikawa´s reagent molecule may be influenced by the

• enhance the fluoride character of the fluorine involved in such interaction. Because of the negative charge on the fluorine in the resonance structure derived from the generalized anomeric effect, a shielding effect is expected for this fluorine. The 19F NMR assignment of the diastereotopic fluorines was

Convergent synthesis of the pentasaccharide repeating unit of the biofilms produced by Klebsiella pneumoniae

• Arin Gucchait,
• Angana Ghosh and
• Anup Kumar Misra

Beilstein J. Org. Chem. 2019, 15, 431–436, doi:10.3762/bjoc.15.37

• -azidoethyl 4,6-O-benzylidene-β-D-glucopyranoside (8) [18], prepared from D-glucose, was selectively O-allylated at the 3-hydroxy group by treatment with dibutyltin oxide followed by allyl bromide in the presence of cesium fluoride [19] via the formation of a stannylene acetal to give 2-azidoethyl 3-O-allyl