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

The cyclopropylcarbinyl route to γ-silyl carbocations

• Xavier Creary

Beilstein J. Org. Chem. 2019, 15, 1769–1780, doi:10.3762/bjoc.15.170

• ; rearrangement; silicon; Introduction Carbocations, positively charged trivalent carbon compounds and reactive intermediates, have continued to fascinate chemists since the early discoveries of tropylium [1][2] and trityl [3][4][5][6][7] salts. Many of the giants of organic chemistry during the last century

• incorporated into this paper is the trimethylsilyl-substituted carbocation [36][37][38][39][40][41][42][43][44]. We have been interested in long-range interactions of silicon with both carbene [45][46][47][48] and carbocation centers [49][50]. Along these lines, γ-trimethylsilyl cations of general type 11 have

• of the cation. These features suggest more facile nucleophilic attack should occur at silicon, favoring bicyclobutane formation. Also included in Table 3 are calculated bond lengths in the phosphoryl-substituted cation 74d, which also shows a very long Si–C bond. Preferred trimethylsilyl elimination

Functional panchromatic BODIPY dyes with near-infrared absorption: design, synthesis, characterization and use in dye-sensitized solar cells

• Quentin Huaulmé,
• Cyril Aumaitre,
• Outi Vilhelmiina Kontkanen,
• David Beljonne,
• Alexandra Sutter,
• Gilles Ulrich,
• Renaud Demadrille and
• Nicolas Leclerc

Beilstein J. Org. Chem. 2019, 15, 1758–1768, doi:10.3762/bjoc.15.169

• , a set of DSSCs were fabricated following a procedure reported previously [4]. The J(V) characteristics of the devices were recorded in dark and upon irradiation with a mask. For the measurements a solar simulator with AM 1.5G filter was used after calibration with a Silicon cell at 1000 W m−2. For a

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

• parent system, diselenolo[3,2-b:2’,3’-d]selenophene (DSS), is still unknown. Cheng et al. published a synthesis of various heterotriacenes including two selenophenes bridged with other elements such as silicon, germanium, nitrogen, and carbon [26]. Very recently, Wang et al. released selenophene-based

Synthesis of polydicyclopentadiene using the Cp₂TiCl₂/Et₂AlCl catalytic system and thin-layer oxidation of the polymer in air

• Zhargolma B. Bazarova,
• Ludmila S. Soroka,
• Alex A. Lyapkov,
• Мekhman S. Yusubov and
• Francis Verpoort

Beilstein J. Org. Chem. 2019, 15, 733–745, doi:10.3762/bjoc.15.69

• by a spectrophotometer Thermo Scientific Evolution 201 using a wavelength range from 200 to 900 nm. Infrared spectra of the polymer were registered applying an FTIR spectrometer Simeks FT-801 in the range from 500 to 4000 cm−1. A silicon plate with a diameter of 8 mm was applied to support the

• (thin layer on silicon) with respect to intensities of adsorption bands at 1410 and 700 cm−1. The distribution of oxygen concentration in the polymer layer: 1 – a layer of oxidized cross-linked polymer; 2 – a layer of non-oxidized polymer. Dependence of the ratio of adsorption bands at 1700 and 700 cm−1

• on the exposure time of the layer in air at ambient temperature. Infrared spectra (a) of products of cationic polymerization of DCPD, stabilized with an antioxidant, after 24 hours (curve 1) and 1030 hours (curve 2) after synthesis (thin layer on silicon wafer) and (b) the correlation of intensity

Synthesis of C₃-symmetric star-shaped molecules containing α-amino acids and dipeptides via Negishi coupling as a key step

• Sambasivarao Kotha and
• Saidulu Todeti

Beilstein J. Org. Chem. 2019, 15, 371–377, doi:10.3762/bjoc.15.33

• treated with silicon tetrachloride and ethanol (SiCl4/EtOH) at room temperature for 6 h to produce the iodonated trimerized product 9 in 71% yield (Scheme 2) [45][46]. Then, the organozinc reagent 7 was coupled with triiodo derivative 9 in the presence of tetrakis(triphenylphosphane)palladium(0) (Pd(PPh3

Application of olefin metathesis in the synthesis of functionalized polyhedral oligomeric silsesquioxanes (POSS) and POSS-containing polymeric materials

• Patrycja Żak and
• Cezary Pietraszuk

Beilstein J. Org. Chem. 2019, 15, 310–332, doi:10.3762/bjoc.15.28

• the properties and applications of the resulting materials. Vinylsilanes show a specific reactivity towards alkylidene ruthenium complexes because of a strong effect of the silyl group on the properties of the double bond. In general, the substituents at the silicon atom determine the regioselectivity

• of the process to a certain degree. The reactivity of vinylsilanes with different substituents at silicon towards alkylidene ruthenium complexes is illustrated in Scheme 1 [7]. According to Scheme 1a, as a result of the reaction of trialkoxy-, tris(trimethylsiloxy)-, trichloro- or dichloromethyl

• mild conditions, hydrogenolysis of the benzyl ester group to the carboxylic acid and hydrogenation of the C=C double bonds at the silicon atoms (Scheme 7). The ability of the obtained derivatives, in particular the carboxylic acids, to generate nanostructured materials through self-organization

Silanediol versus chlorosilanol: hydrolyses and hydrogen-bonding catalyses with fenchole-based silanes

• Falco Fox,
• Jörg M. Neudörfl and
• Bernd Goldfuss

Beilstein J. Org. Chem. 2019, 15, 167–186, doi:10.3762/bjoc.15.17

• phenyl groups at the silicon atom are converted by acids (e.g., TFA or TfOH) and following aqueous work-up into silanediols [2][4][7][8][9][10][11]. Another route employs dichlorosilanes, which hydrolyze directly with nucleophiles (e.g., water [12][13][14][15][16][17] or hydroxide [18][19][20][21][22

• Nucleophilic substitution at silicon is already discussed with SN2 mechanism, following a backside attack opposite of the leaving group, as well as a front side attack near the leaving group [62][63][64][65][66][67][68]. A backside attack at the silicon in dichlorosilane 7 and monochlorosilanol 8 is blocked by

• the backbone, making a consideration of the mechanism not necessary. A mechanism with a pentacoordination at the silicon is assumed for the hydrolyses of BIFOXSiCl2 (7) to BIFOXSiCl(OH) (8) as intermediate and BIFOXSI(OH)2 (9) as product [65][66][67]. Two pathways (front attack mechanism (front) or

Dispersion-mediated steering of organic adsorbates on a precovered silicon surface

• Lisa Pecher,
• Sebastian Schmidt and
• Ralf Tonner

Beilstein J. Org. Chem. 2018, 14, 2715–2721, doi:10.3762/bjoc.14.249

• theory; dispersion; organic/inorganic interfaces; Introduction The creation of organic/inorganic interfaces is one of the main endeavours in enhancing the application range of modern electronic devices for silicon-based technology [1][2]. One way to achieve this is covalent attachment of bifunctional

• organic molecules on bare silicon surfaces and subsequent reaction with a second molecule with both reactions being chemoselective (layer-by-layer, LbL, approach) [3][4][5]. To achieve an interface structure with predictable properties, it is important that the molecules used for the first layer show well

• minimization without symmetry constraints leads to a structure with a local C2 rotational axis resulting in symmetry-equivalent molecules 1 and 1′. Energies and Gibbs energies of adsorption were previously found to support the notion of strong covalent bonding for the [2 + 2] cycloaddition of 1 on the silicon

Design and synthesis of C₃-symmetric molecules bearing propellane moieties via cyclotrimerization and a ring-closing metathesis sequence

• Sambasivarao Kotha,
• Saidulu Todeti and
• Vikas R. Aswar

Beilstein J. Org. Chem. 2018, 14, 2537–2544, doi:10.3762/bjoc.14.230

• (9) in the presence of triethylamine (Et3N) in toluene at 140 °C to obtain the acetophenone derivative 10 in excellent yield (92%) [43]. Later, the acetophenone derivative 10 was subjected to trimerization reaction under ethanol/silicon tetrachloride (EtOH/SiCl4) conditions to deliver the trimerized

• ), silicon tetrachloride (SiCl4, 0.61 mL, 5.36 mmol) was added dropwise at 0 °C and the reaction mixture was stirred for 10–15 min at the same temperature. Later, the reaction mixture was stirred at room temperature for 20 h. After completion of the reaction (TLC monitoring), the reaction mixture was

Quinolines from the cyclocondensation of isatoic anhydride with ethyl acetoacetate: preparation of ethyl 4-hydroxy-2-methylquinoline-3-carboxylate and derivatives

• Nicholas G. Jentsch,
• Jared D. Hume,
• Emily B. Crull,
• Samer M. Beauti,
• Amy H. Pham,
• Julie A. Pigza,
• Jacques J. Kessl and
• Matthew G. Donahue

Beilstein J. Org. Chem. 2018, 14, 2529–2536, doi:10.3762/bjoc.14.229

• alkoxide G that undergoes a [1,4]-shift of the silicon group with concomitant ejection of cyanide anion to form acyl cyanide H [33]. As the reaction is run in the presence of ethanol, nucleophilic acyl substitution of cyanide H for the ethoxy group furnishes the ethyl ester 21 in one pot. We were therefore

Non-metal-templated approaches to bis(borane) derivatives of macrocyclic dibridgehead diphosphines via alkene metathesis

• Tobias Fiedler,
• Michał Barbasiewicz,
• Michael Stollenz and
• John A. Gladysz

Beilstein J. Org. Chem. 2018, 14, 2354–2365, doi:10.3762/bjoc.14.211

• somewhat higher overall yields, as analyzed elsewhere [1][2][3][4]. Setaka has developed a similar chemistry in which the phosphorus atoms are replaced by silicon and the metal fragment by p-phenylene (p-C6H4) or related aromatic moieties [14][15][16][17][18][19]. These types of compounds are viewed as

Tetrathiafulvalene – a redox-switchable building block to control motion in mechanically interlocked molecules

• Hendrik V. Schröder and
• Christoph A. Schalley

Beilstein J. Org. Chem. 2018, 14, 2163–2185, doi:10.3762/bjoc.14.190

• electrically operated without the need of chemical additives, if conducting solid supports are used. This also opens pathways towards the integration of switchable AMMs into the world of silicon-based chips and electronic circuits. A landmark in the field of molecular-scale electronic devices is the rotaxane

Natural and redesigned wasp venom peptides with selective antitumoral activity

• Marcelo D. T. Torres,
• Gislaine P. Andrade,
• Roseli H. Sato,
• Cibele N. Pedron,
• Tania M. Manieri,
• Giselle Cerchiaro,
• Anderson O. Ribeiro,
• Cesar de la Fuente-Nunez and
• Vani X. Oliveira Jr.

Beilstein J. Org. Chem. 2018, 14, 1693–1703, doi:10.3762/bjoc.14.144

• when compared to other analogs and was used here as a treated control) was performed using an Agilent Technologies 5500 AFM/SPM microscope that was in contact mode and a Nanosensors™ PPP-CONT probe (NanoSensors; PPP-Cont-20, PointProbe-Plus Silicon-SPM-Sensor). The material properties and dimensions of

Cobalt–metalloid alloys for electrochemical oxidation of 5-hydroxymethylfurfural as an alternative anode reaction in lieu of oxygen evolution during water splitting

• Jonas Weidner,
• Stefan Barwe,
• Kirill Sliozberg,
• Stefan Piontek,
• Justus Masa,
• Ulf-Peter Apfel and
• Wolfgang Schuhmann

Beilstein J. Org. Chem. 2018, 14, 1436–1445, doi:10.3762/bjoc.14.121

• Te), could likewise lead to an enhanced electrocatalysis for reactions other than the OER and the HER. To this end, alloys of cobalt with boron, silicon, phosphorus, arsenic and tellurium were screened for their electrocatalytic activity for HMF oxidation. A detailed synthetic procedure to afford

Hypervalent iodine-guided electrophilic substitution: para-selective substitution across aryl iodonium compounds with benzyl groups

• Cyrus Mowdawalla,
• Faiz Ahmed,
• Tian Li,
• Kiet Pham,
• Loma Dave,
• Grace Kim and
• I. F. Dempsey Hyatt

Beilstein J. Org. Chem. 2018, 14, 1039–1045, doi:10.3762/bjoc.14.91

• mechanism could be occurring with metalloid groups such as silicon and boron. Hypervalent iodine reagents such as Zefirov’s reagent, cyclic iodonium reagents, iodosobenzene/BF3, and PhI(OAc)2/BF3 or triflate-based activators were tested. A desirable facet of the reported reaction is that iodine(I) is

Cross-coupling of dissimilar ketone enolates via enolonium species to afford non-symmetrical 1,4-diketones

• Keshaba N. Parida,
• Gulab K. Pathe,
• Shimon Maksymenko and
• Alex M. Szpilman

Beilstein J. Org. Chem. 2018, 14, 992–997, doi:10.3762/bjoc.14.84

• [11] and Wirth [6][7][12] both circumvented the selectivity and reactivity problem by making use of a temporary silicon connection strategy to render the reaction intramolecular. In both cases, the two ketone enolates were coupled successively to dimethyldichlorosilane. Thomson achieved the cross

Continuous multistep synthesis of 2-(azidomethyl)oxazoles

• Thaís A. Rossa,
• Nícolas S. Suveges,
• Marcus M. Sá,
• David Cantillo and
• C. Oliver Kappe

Beilstein J. Org. Chem. 2018, 14, 506–514, doi:10.3762/bjoc.14.36

• in a silicon bath at 150 °C. The vinyl azide solution in acetone was introduced into the reactor by a syringe pump (Syrris) with variable flow rates (Table 4) to obtain different residence times. The system was pressurized using a back-pressure regulator (BPR, Upchurch) at 17 bar (250 psi). The

Syn-selective silicon Mukaiyama-type aldol reactions of (pentafluoro-λ⁶-sulfanyl)acetic acid esters with aldehydes

• Anna-Lena Dreier,
• Andrej V. Matsnev,
• Joseph S. Thrasher and
• Günter Haufe

Beilstein J. Org. Chem. 2018, 14, 373–380, doi:10.3762/bjoc.14.25

• . The selectivity of these reactions depends on the geometry of the intermediate enolates. Here, we have reacted octyl pentafluoro-λ6-sulfanylacetate with substituted benzaldehydes and acetaldehyde under the conditions of the silicon-mediated Mukaiyama aldol reaction. The transformations proceeded with

• rearrangement [31]. Under slightly modified conditions, this type of rearrangement was also successful for SF5-substituted acetic esters of cinnamyl alcohols [32]. Herein we describe our results [33] of highly syn-diastereoselective silicon Mukaiyama-type aldol reactions of SF5-acetic acid esters with different

• addition products. Thus, the minor products of the silicon Mukaiyama aldol reactions are the anti-isomers 3. On the other hand, the vicinal coupling constants of the major products were found between 8.5 Hz for the p-nitro derivative 2a to about 9.4 Hz for derivatives 2b–e with less electron-withdrawing