Synthesis of trifluoromethyl ketones by nucleophilic trifluoromethylation of esters under a fluoroform/KHMDS/triglyme system

• Yamato Fujihira,
• Yumeng Liang,
• Makoto Ono,
• Kazuki Hirano,
• Takumi Kagawa and
• Norio Shibata

Beilstein J. Org. Chem. 2021, 17, 431–438, doi:10.3762/bjoc.17.39

• some effect on the reaction (Table 2, entries 9–15, 63–87%). Besides, silicon-containing compound, trimethyl(phenyl)silane that is more sensitive to fluorine was screened, 79% yield were obtained in this test. To consider the frequency of these motifs in modern pharmaceutical drugs, these tests are

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

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

• tetrachloride produces an alkyoxy allylic carbocation (not shown). This carbocation is subjected to a regiospecific electrophilic substitution of allene 168 to generate a vinyl cation 172, which is stabilized by an adjacent carbon–silicon bond. The 1,2-shift of the silyl group in 172 produces an isomeric vinyl

Changed reactivity of secondary hydroxy groups in C8-modified adenosine – lessons learned from silylation

• Jennifer Frommer and
• Sabine Müller

Beilstein J. Org. Chem. 2020, 16, 2854–2861, doi:10.3762/bjoc.16.234

• neighboring silicon leads to silyl migration and consequently to an isomeric mixture, which can be separated by column chromatography [30]. However, this procedure does not secure high yields and the careful separation of a sufficient amount of the 2’-O-silyl isomers is rather time consuming. Additionally

Dirhamnolipid ester – formation of reverse wormlike micelles in a binary (primerless) system

• David Liese,
• Hans Henning Wenk,
• Xin Lu,
• Jochen Kleinen and
• Gebhard Haberhauer

Beilstein J. Org. Chem. 2020, 16, 2820–2830, doi:10.3762/bjoc.16.232

• camera. Atomic force microscopy Atomic force microscopy (AFM) images were performed in the tapping mode using a NanoDrive Controller with an Innova Scanning Probe Microscope (Veeco) and an N-type silicon cantilever (Olympus AC 16TS). The samples were prepared by drop-coating the solution (50 µM) on a

Dawn of a new era in industrial photochemistry: the scale-up of micro- and mesostructured photoreactors

• Emine Kayahan,
• Mathias Jacobs,
• Leen Braeken,
• Leen C.J. Thomassen,
• Simon Kuhn,
• Tom van Gerven and
• M. Enis Leblebici

Beilstein J. Org. Chem. 2020, 16, 2484–2504, doi:10.3762/bjoc.16.202

Naphthalene diimide bis-guanidinio-carbonyl-pyrrole as a pH-switchable threading DNA intercalator

• Poulami Jana,
• Filip Šupljika,
• Carsten Schmuck and
• Ivo Piantanida

Beilstein J. Org. Chem. 2020, 16, 2201–2211, doi:10.3762/bjoc.16.185

• silicon cantilevers (AC-160TS, Olympus) a NanoDrive controller with an Innova scanning probe microscope (Veeco, Germany, Mannheim) was used. The analysis of the AFM images was carried out by use of the Gwyddion (version 2.19) software. DLS experimental All measurements were carried out using a

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

• , 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

pH- and concentration-dependent supramolecular self-assembly of a naturally occurring octapeptide

• Goutam Ghosh and
• Gustavo Fernández

Beilstein J. Org. Chem. 2020, 16, 2017–2025, doi:10.3762/bjoc.16.168

• the desired pH values. AFM samples were prepared by drop-casting 10 μL of the respective sample onto a mica surface, followed by spin-coating at 1000 rpm, and then, the thin film was dried at room temperature for 24 h. After that, images were captured on a Multimode® 8 SPM System (AXS Bruker). Silicon

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

• high diastereoselectivity [56]. In contrast to previous silicon-based tethers, which reacted in low yields and resulted in unexpected byproducts, this transformation could be performed on a multigram scale and showed a wide substrate scope and functional group compatibility, as well as high

Photoredox-catalyzed silyldifluoromethylation of silyl enol ethers

• Vyacheslav I. Supranovich,
• Vitalij V. Levin and
• Alexander D. Dilman

Beilstein J. Org. Chem. 2020, 16, 1550–1553, doi:10.3762/bjoc.16.126

• carbon–bromine bond. Keywords: difluoroalkylation; organofluorine compounds; photocatalysis; radical addition; silicon reagents; Findings Fluorinated silicon reagents have found widespread use for the introduction of fluorinated fragments [1][2][3][4][5]. Typically, these reagents work under strongly

• product with concomitant production of TMSBr. Conclusion In summary, a method for the introduction of the silyldifluoromethyl group was described by the coupling of a readily available silicon reagent with silyl enol ethers. The reaction is promoted by light and involves the generation of a fluorinated

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

• material is drastically different for inorganic and organic semiconductors. High εr(ω) materials, such as silicon (εr(ω) = 12) or GaAs (εr(ω) = 13), effectively screen the Coulombic attraction between excitons to 10s of meV, allowing the charge carriers to easily dissociate at room temperature [109][110

• imitate light transmission through flesh, as this is relevant for photocatalyst applications in photodynamic therapy [197][198][199]. They reported that the NIR photons penetrated 293 times deeper into the polymerisation medium and enabled the reaction to be applicable on a multigram scale through silicon

Recent synthesis of thietanes

• Jiaxi Xu

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

• underwent a thermal rearrangement to generate tricyclic isobenzofurans 313 through the ring-cleavage of the thietanes. It was assumed that the rearrangement was assisted through participation of the oxygen lone-pair electrons [17] (Scheme 57). The silicon-containing phenyl triphenylsilyl thioketone (316

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

• F-1a phase) that were immediately put into silicon grease and cooled to 120 K at the diffractometer. The data collection revealed a triclinic P-1 phase, with the lattice parameters a = 13.416(7) Å, b = 13.887(7) Å, c = 22.730(12) Å, α = 88.564(8)°, β = 87.351(8)°, γ = 89.836(9)°, cell volume = 4229

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

• incorporating silicon or boron into new or existing drugs, in addition to their use as building blocks in cross-coupling reactions en route to various targets of both natural and unnatural origins. In this review, recent protocols relying on copper-catalyzed sp3 carbon–silicon and carbon–boron bond-forming

• functional groups into existing or new drugs. Examples include the incorporation of silicon bioisosteres that help increase lipophilicity, subsequently altering the existing metabolic pathway of a drug due to differences in its physicochemical properties [8]. On the other hand, the trigonal planar nature of

• boron can lead to dative bond formation with enzymes, and therefore increase binding affinity. As shown in Scheme 1, several silicon [9][10][11][12] and boron-containing [13][14][15][16] drugs have already entered the market, or are currently in the drug development pipeline. As the number of drugs

Regioselectively α- and β-alkynylated BODIPY dyes via gold(I)-catalyzed direct C–H functionalization and their photophysical properties

• Takahide Shimada,
• Shigeki Mori,
• Masatoshi Ishida and
• Hiroyuki Furuta

Beilstein J. Org. Chem. 2020, 16, 587–595, doi:10.3762/bjoc.16.53

• : triisopropylsilyl group; Mes: 2,4,6-trimethylphenyl group. Top and front views of the crystal structures of (a) 4a and (b) 6b with 50% thermal ellipsoid probabilities. The isopropyl groups on the silicon atom are omitted in the front view for clarity. Partial 1H NMR spectra of (a) 1a, (b) 3a, (c) 4a, (d) 5a, and (e

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

• applications that focused on the title catalysts in CuAAC reactions. Review Copper anchored on functionalized silica materials: efficient and recyclable catalysts for CuAAC reactions In recent years, silica or silicon dioxide nanomaterials have received much attention from researchers and industry and have

• been used in a wide spectrum of applications. Silica nanomaterials have the empirical formula SiO2 in which one silicon atom covalently links to four oxygen atoms, and most of the oxygen bond to two silicon atoms. Hence, their atoms are randomly oriented to produce amorphous structures. These materials

Copper-catalyzed enantioselective conjugate reduction of α,β-unsaturated esters with chiral phenol–carbene ligands

• Shohei Mimura,
• Sho Mizushima,
• Yohei Shimizu and
• Masaya Sawamura

Beilstein J. Org. Chem. 2020, 16, 537–543, doi:10.3762/bjoc.16.50

• compounds was examined. Because the separation of the product from silicon-based byproducts was troublesome, the isolated yields were lower than the yields determined by NMR spectroscopy (2a, 52%, Table 2, entry 1). When (E)-1a was used as the substrate, the opposite enantiomer (S)-2a was obtained in >99

• magnetic stirring bar. The vial was sealed with a teflon-coated silicon rubber septum. N,N-Dimethylacetamide (0.90 mL) was added to the vial, and then the mixture was stirred at room temperature for 5 min. Next, t-AmOH (16.3 μL, 0.15 mmol) was added, and the vial was taken out of the glove box. To the

Allylic cross-coupling using aromatic aldehydes as α-alkoxyalkyl anions

• Akihiro Yuasa,
• Kazunori Nagao and
• Hirohisa Ohmiya

Beilstein J. Org. Chem. 2020, 16, 185–189, doi:10.3762/bjoc.16.21

• stirring bar. The vial was sealed with a Teflon®-coated silicon rubber septum, and then the vial was evacuated and filled with nitrogen. Toluene (0.6 mL) was added to the vial, and then the mixture was stirred at 25 °C for 10 min. Next, PhMe2SiB(pin) (104.9 mg, 0.4 mmol) and benzaldehyde (1a, 42.4 mg, 0.4

• mmol) were added, and the mixture (mixture A) was stirred at 25 °C for 10 min. Meanwhile, Pd(OCOCF3)2 (2.0 mg, 0.006 mmol) and DPPF (3.3 mg, 0.006 mmol) were placed in another vial. This vial was sealed with a Teflon®-coated silicon rubber septum and then evacuated and filled with nitrogen. After

Efficient method for propargylation of aldehydes promoted by allenylboron compounds under microwave irradiation

• Jucleiton J. R. Freitas,
• Queila P. S. B. Freitas,
• Silvia R. C. P. Andrade,
• Juliano C. R. Freitas,
• Roberta A. Oliveira and
• Paulo H. Menezes

Beilstein J. Org. Chem. 2020, 16, 168–174, doi:10.3762/bjoc.16.19

• organometallic species of Cd [16], Ga [17], In [18], Ti [19], Al [20] and Bi [21] were described. However, the majority of these methods involve reagents that are difficult to prepare and to handle due to the sensitivity to air and moisture. The use of less reactive species based on tin [22][23][24], silicon [25

A new approach to silicon rhodamines by Suzuki–Miyaura coupling – scope and limitations

• Thines Kanagasundaram,
• Antje Timmermann,
• Carsten S. Kramer and
• Klaus Kopka

Beilstein J. Org. Chem. 2019, 15, 2569–2576, doi:10.3762/bjoc.15.250

• Cancer Consortium (DKTK), Heidelberg, Germany 10.3762/bjoc.15.250 Abstract Background: Silicon rhodamines are of particular interest because of their advantageous dye properties (fluorescence- and biostability, quantum efficiency, tolerance to photobleaching). Therefore, silicon rhodamines find frequent

• gave access to silicon rhodamines in poor to moderate yields, we wanted to improve these first valuable experimental results. Results: The preparation of the xanthene triflate was enhanced and several boron sources were screened to find the optimal coupling partner. After optimization of the palladium

• catalyst, different substituted boroxines were assessed to explore the scope of the Pd-catalyzed cross-coupling reaction. Conclusions: A number of silicon rhodamines were synthesized under the optimized conditions in up to 91% yield without the necessity of HPLC purification. Moreover, silicon rhodamines

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

• solvents were checked for the lack of fluorescence when excited with 450–600 nm. Polymer films with or without NR were prepared by spin-casting of 3 wt % polymer solutions in 1,2-dichloroethane, dichloromethane or chloroform on silicon wafers (for ellipsometry) and on 20 × 20 × 0.15 mm3 Metzler glass

Chiral terpene auxiliaries V: Synthesis of new chiral γ-hydroxyphosphine oxides derived from α-pinene

• Anna Kmieciak and
• Marek P. Krzemiński

Beilstein J. Org. Chem. 2019, 15, 2493–2499, doi:10.3762/bjoc.15.242

• phosphine with poly(methylhydrosiloxane) in the presence of titanium(IV) isopropoxide (Scheme 4). The work-up of the reaction mixture with 25% HF allowed to remove silicon and titanium impurities and purification of 23 by column chromatography on silica gel yielded the product in 62%. 4

Synthesis of a dihalogenated pyridinyl silicon rhodamine for mitochondrial imaging by a halogen dance rearrangement

• Jessica Matthias,
• Thines Kanagasundaram,
• Klaus Kopka and
• Carsten S. Kramer

Beilstein J. Org. Chem. 2019, 15, 2333–2343, doi:10.3762/bjoc.15.226

• .15.226 Abstract Background: Since their first synthesis, silicon xanthenes and the subsequently developed silicon rhodamines (SiR) gained a lot of attention as attractive fluorescence dyes offering a broad field of application. We aimed for the synthesis of a fluorinable pyridinyl silicon rhodamine for

• ; mitochondrial probe; near-infrared (NIR) dyes; one-pot reaction; silicon rhodamines; Introduction Since their first synthesis by Fu and co-workers in 2008 [1], silicon xanthenes and the subsequently developed silicon rhodamines (SiR) have drawn a lot of attention as attractive fluorescence dyes offering a

• features with their optical properties and control the latter by rational dye design [15][24][25][26]. These investigations led to new silicon rhodamine dyes with enhanced and fine-tuned properties (quantum yield, lifetime, brightness, absorption and emission maxima). A recent review compared the

Halide metathesis in overdrive: mechanochemical synthesis of a heterometallic group 1 allyl complex

• Ross F. Koby,
• Nicholas R. Rightmire,
• Nathan D. Schley,
• Timothy P. Hanusa and
• William W. Brennessel

Beilstein J. Org. Chem. 2019, 15, 1856–1863, doi:10.3762/bjoc.15.181

• distance of K+ to Me3SiH, chosen to represent somewhat more accurately the type of interactions occurring in [KCsA'2], is slightly shorter (3.14 Å) and stronger (30 kJ mol–1), probably a result of the lower electronegativity of silicon compared to carbon and the correspondingly more negative methyl groups