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

Recent advances on organic blue thermally activated delayed fluorescence (TADF) emitters for organic light-emitting diodes (OLEDs)

• Thanh-Tuân Bui,
• Fabrice Goubard,
• Malika Ibrahim-Ouali,
• Didier Gigmes and
• Frédéric Dumur

Beilstein J. Org. Chem. 2018, 14, 282–308, doi:10.3762/bjoc.14.18

• with the azasiline donor, OLEDs displaying the unprecedented EQE of 22.3% were obtained [46]. As specificity, azasiline is a 6-membered heterocycle comprising a silicon atom introduced instead of a carbon atom to enlarge the HOMO–LUMO gap and lower the HOMO level. Due to the sp3 hybridization of the

• silicon atom, two phenyl rings can be introduced on the silicon-bridged structure providing bulkiness and rigidity to the donor. Intermolecular interactions are thus efficiently prevented and the conformation disorder drastically reduced. When used as electron donor in T1, a ΔEST of 0.14 eV was determined

Fluorogenic PNA probes

• Tirayut Vilaivan

Beilstein J. Org. Chem. 2018, 14, 253–281, doi:10.3762/bjoc.14.17

• following standard surface-hybridization protocols. The use of the solid support assay format also allows detection of DNA directly from the fluorescence signal of the CPP bound to the solid support without requiring labeling on the PNA probe [126]. Polystyrene microbeads self-assembled on patterned silicon

Syntheses, structures, and stabilities of aliphatic and aromatic fluorous iodine(I) and iodine(III) compounds: the role of iodine Lewis basicity

• Tathagata Mukherjee,
• Soumik Biswas,
• Andreas Ehnbom,
• Subrata K. Ghosh,
• Ibrahim El-Zoghbi,
• Nattamai Bhuvanesh,
• Hassan S. Bazzi and
• John A. Gladysz

Beilstein J. Org. Chem. 2017, 13, 2486–2501, doi:10.3762/bjoc.13.246

• species have never been described in the literature. Silicon has been used as a locus for branching, as exemplified by a variety of highly fluorophilic compounds of the formula (RfnCH2CH2)3SiZ (see XI in Scheme 7, Z = 4-C6H5X [53][54]). However, these feature silicon–carbon and sp3 carbon–hydrogen bonds

Synthesis and photophysical properties of novel benzophospholo[3,2-b]indole derivatives

• Mio Matsumura,
• Mizuki Yamada,
• Atsuya Muranaka,
• Misae Kanai,
• Naoki Kakusawa,
• Daisuke Hashizume,
• Masanobu Uchiyama and
• Shuji Yasuike

Beilstein J. Org. Chem. 2017, 13, 2304–2309, doi:10.3762/bjoc.13.226

• -b]phosphole dioxides (Figure 1A) [25][26] and benzophosphole-fused tetracyclic heteroacenes, containing boron (B) [27][28][29], silicon (Si) [30], oxygen (O) [31], and sulfur (S) [32][33][34] (Figure 1B), were synthesized and their physical properties were studied. However, to the best of our

Phosphonic acid: preparation and applications

• Charlotte M. Sevrain,
• Mathieu Berchel,
• Hélène Couthon and
• Paul-Alain Jaffrès

Beilstein J. Org. Chem. 2017, 13, 2186–2213, doi:10.3762/bjoc.13.219

• step. As suggested in the initial works of McKenna, the mechanism occurs by an oxophilic substitution on the silicon atom whereas bromide acts as a leaving group to produce the intermediate I (Figure 14). This intermediate is then dealkylated following a similar path than that occurring with the

• the terminal oxygen doubly bonded to the phosphorus atom was indeed the nucleophilic atom that attacks the silicon atom [159]. Regarding the mechanism of this reaction, the oxophilic silylation involving the oxygen atom which is doubly bonded to the phosphorus atom, thus producing the intermediate I

Superstructures with cyclodextrins: Chemistry and applications IV

• Gerhard Wenz

Beilstein J. Org. Chem. 2017, 13, 2157–2159, doi:10.3762/bjoc.13.215

• Thematic Series in the article by Leclercq [19]. For example, β-CD was immobilized onto a silicon substrate and incubated with various bacteria. These bacteria could be captured nearly quantitatively at the surface and released again by competitive binding with free methylated β-CD [20]. The proteins

Synthesis of substituted Z-styrenes by Hiyama-type coupling of oxasilacycloalkenes: application to the synthesis of a 1-benzoxocane

• James R. Vyvyan,
• Courtney A. Engles,
• Scott L. Bray,
• Erik D. Wold,
• Christopher L. Porter and
• Mikhail O. Konev

Beilstein J. Org. Chem. 2017, 13, 2122–2127, doi:10.3762/bjoc.13.209

• ; palladium; silicon; Introduction The development of transition metal-catalyzed cross-coupling technologies over the last four decades revolutionized the synthetic chemistry. Indeed, the importance of Pd-catalyzed coupling was recognized with the 2010 Nobel Prize awarded to Heck, Negishi and Suzuki [1][2