Automated solid-phase peptide synthesis to obtain therapeutic peptides

• Veronika Mäde,
• Sylvia Els-Heindl and
• Annette G. Beck-Sickinger

Beilstein J. Org. Chem. 2014, 10, 1197–1212, doi:10.3762/bjoc.10.118

• styrene and cross-linked divinylbenzene [20]. At present, there are mainly three classes of solid carriers: traditional polystyrene (PS), polyethylene glycol (PEG)-functionalized PS (such as TentaGel-supports [47]) and pure PEG-based resins such as PEGA resin [48] and ChemMatrix [49]. Shelton et al

Novel indolin-2-one-substituted methanofullerenes bearing long n-alkyl chains: synthesis and application in bulk-heterojunction solar cells

• Irina P. Romanova,
• Andrei V. Bogdanov,
• Inessa A. Izdelieva,
• Vasily A. Trukhanov,
• Gulnara R. Shaikhutdinova,
• Dmitry G. Yakhvarov,
• Shamil K. Latypov,
• Vladimir F. Mironov,
• Vladimir A. Dyakov,
• Ilya V. Golovnin,
• Dmitry Yu. Paraschuk and
• Oleg G. Sinyashin

Beilstein J. Org. Chem. 2014, 10, 1121–1128, doi:10.3762/bjoc.10.111

• data of these compounds can be found in Supporting Information File 1. Materials, characterization and devices P3HT (Rieke Metals), PCBM (Solenne), poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate), PEDOT:PSS (Baytron P VP AI 4083, H.C. Stark) and 1,2-dichlorobenzene (DCB) were used as received

On the mechanism of photocatalytic reactions with eosin Y

• Michal Majek,
• Fabiana Filace and
• Axel Jacobi von Wangelin

Beilstein J. Org. Chem. 2014, 10, 981–989, doi:10.3762/bjoc.10.97

• mechanistic pathways. Our experiments (Scheme 6) afforded quantum yields of Φ > 1 for the heterobiaryl coupling [15] and the Heck-type olefination with styrene [16], respectively. This indicates that in addition to a photocatalytic path (Scheme 2, A) radical-chain propagation is operating under the reaction

N-Alkylated dinitrones from isosorbide as cross-linkers for unsaturated bio-based polyesters

• Oliver Goerz and
• Helmut Ritter

Beilstein J. Org. Chem. 2014, 10, 902–909, doi:10.3762/bjoc.10.88

• used. A set of columns packed with porous styrene–divinylbenzene–copolymer beads was used for the separation of the analytes (MZ Analysentechnik GmbH, 1 × guard column 100 Å, 3 × columns with 10.000, 1000 und 100 Å). The system was calibrated with polystyrene standards with a molecular range from 575 g

Continuous-flow Heck synthesis of 4-methoxybiphenyl and methyl 4-methoxycinnamate in supercritical carbon dioxide expanded solvent solutions

• Phei Li Lau,
• Ray W. K. Allen and
• Peter Styring

Beilstein J. Org. Chem. 2013, 9, 2886–2897, doi:10.3762/bjoc.9.325

• , 43500 Semenyih, Selangor Darul Shsan, Malaysia 10.3762/bjoc.9.325 Abstract The palladium metal catalysed Heck reaction of 4-iodoanisole with styrene or methyl acrylate has been studied in a continuous plug flow reactor (PFR) using supercritical carbon dioxide (scCO2) as the solvent, with THF and

• studied as a function of temperature, pressure and flow rate and in the case of the reaction with styrene compared against a standard, stirred autoclave reaction. Conversion was determined and, in the case of the reaction with styrene, the isomeric product distribution was monitored by GC. In the case of

• stable and highly active heterogeneous catalyst in the Heck reactions of styrene and halides, including iodides, chlorine substituents, and both activated and non-activated bromine [32]. It has been rationalised that the MgLaO support itself appears to act as a base, which in turn acted as an electron

3-Pyridinols and 5-pyrimidinols: Tailor-made for use in synergistic radical-trapping co-antioxidant systems

• Luca Valgimigli,
• Daniele Bartolomei,
• Riccardo Amorati,
• Evan Haidasz,
• Jason J. Hanthorn,
• Susheel J. Nara,
• Johan Brinkhorst and
• Derek A. Pratt

Beilstein J. Org. Chem. 2013, 9, 2781–2792, doi:10.3762/bjoc.9.313

• constants for the reactions of various pyridinols and pyrimidinols with peroxyl radicals (kinh) were measured by the well-established inhibited autoxidation of styrene (or cumene) in chlorobenzene at 303 K. These measurements also included experiments with three well-established phenolic antioxidants: 2,6

• sufficiently high O–H BDE to be regenerated by the co-antioxidant, co-AH (vide supra), which was selected among the conventional phenols 10–12. The autoxidation of an organic substrate (e.g. styrene) thermally initiated at a constant rate, Ri, by an azo-initiator will consume oxygen at a constant rate in the

• °C. Cumene (98%) and styrene (≥99%) were distilled under reduced pressure and percolated twice through silica and alumina prior to use. All solutions were prepared fresh immediately prior to use. Synthesis. Compounds 4a, 4b, 6a and 6b were prepared as described in [39]. Compounds 4c and 4d were

New developments in gold-catalyzed manipulation of inactivated alkenes

• Michel Chiarucci and
• Marco Bandini

Beilstein J. Org. Chem. 2013, 9, 2586–2614, doi:10.3762/bjoc.9.294

• , (i.e. styrene and gem-disubstituted olefins) to be efficiently employed (Scheme 39b) [85]. An innovative approach to the double functionalization of olefins was developed by Glorius and co-workers, very recently. The authors reported on the use of visible light-mediated photoredox catalysis to access

A one-pot synthesis of 3-trifluoromethyl-2-isoxazolines from trifluoromethyl aldoxime

• Raoni S. B. Gonçalves,
• Michael Dos Santos,
• Guillaume Bernadat,
• Danièle Bonnet-Delpon and
• Benoit Crousse

Beilstein J. Org. Chem. 2013, 9, 2387–2394, doi:10.3762/bjoc.9.275

• reacted with olefins (such as styrene, allyl derivatives, etc.) through a 1,3-dipolar cycloaddition to give the desired product. Therefore, the development of a straightforward and mild general procedure to access these valuable derivatives remains of great importance. In the present work, we describe a

Non-cross-linked polystyrene-supported 2-imidazolidinone chiral auxiliary: synthesis and application in asymmetric alkylation reactions

• Quynh Pham Bao Nguyen and
• Taek Hyeon Kim

Beilstein J. Org. Chem. 2013, 9, 2113–2119, doi:10.3762/bjoc.9.248

• functionalized 2-imidazolidinone-derived monomers 2 with styrene in a 1:1 ratio using AIBN as a radical initiator in THF (Scheme 1) [9]. After the precipitation in cold methanol, the expected polymer 3, which was soluble in THF, CH2Cl2, and DMF, was obtained in low yield (40%). Therefore, to save our 2

• solubility, several non-crosslinked chloromethylated polystyrenes 4 were simply synthesized according to reported procedures [6][8] in different feed ratios of 4-chloromethylstyrene and styrene of 1:1, 2:1, and 1:0 (Table 1). The NCPS 4a, 4b, and 4c were obtained in 46, 40, and 52% yield, respectively, and

• . Unexpectedly, racemization occurred under these cleavage conditions to produce the corresponding chiral alcohol and ester in 80% and 77% ee, respectively. Synthesis of NCPS-supported 2-imidazolidinone chiral auxiliary 3 through direct copolymerization of 2-imidazolidinone derived monomer 2 with styrene

Self-assembly of 2,3-dihydroxycholestane steroids into supramolecular organogels as a soft template for the in-situ generation of silicate nanomaterials

• Valeria C. Edelsztein,
• Andrea S. Mac Cormack,
• Matías Ciarlantini and
• Pablo H. Di Chenna

Beilstein J. Org. Chem. 2013, 9, 1826–1836, doi:10.3762/bjoc.9.213

• gelled by steroid 1, styrene and methyl acrylate offer great potential in the preparation of mesoporous polymers. We are currently exploring these materials and their potential applications. Experimental Materials Cholesterol (94%) was purchased from Sigma-Aldrich. n-Hexane, ethyl acetate

The application of a monolithic triphenylphosphine reagent for conducting Ramirez gem-dibromoolefination reactions in flow

• Kimberley A. Roper,
• Malcolm B. Berry and
• Steven V. Ley

Beilstein J. Org. Chem. 2013, 9, 1781–1790, doi:10.3762/bjoc.9.207

• precipitation polymerisation of the phosphine monomer 5 (Scheme 2). A polymerisation mixture of the triphenylphosphine monomer 5, cross-linking components divinylbenzene (6) and styrene (7) along with the porogen, 1-dodecanol (8), was heated to 50 °C until a homogeneous mixture was achieved. The initiator

• clearly viewed in a video previously released by our group [40], however the Ramirez monoliths employ a higher ratio of styrene to divinylbenzene. This results in a lower proportion of crosslinking within the monolith, allowing greater flexibility in the backbone of the polymer whilst still maintaining

Gallium-containing polymer brush film as efficient supported Lewis acid catalyst in a glass microreactor

• Rajesh Munirathinam,
• Roberto Ricciardi,
• Richard J. M. Egberink,
• Jurriaan Huskens,
• Michael Holtkamp,
• Herbert Wormeester,
• Uwe Karst and
• Willem Verboom

Beilstein J. Org. Chem. 2013, 9, 1698–1704, doi:10.3762/bjoc.9.194

• X-ray photoelectron spectroscopy (XPS). XPS revealed the presence of one gallium per 2–3 styrene sulfonate groups of the polymer brushes. The catalytic activity of the Lewis acid-functionalized brushes in a microreactor was demonstrated for the dehydration of oximes, using cinnamaldehyde oxime as a

• polymerization (ATRP) initiator was covalently anchored on silicon oxide substrates [20]. Then, a solution of styrene sulfonate in methanol/water (1:3) in the presence of 2-2’-bipyridyl and CuBr, was used to grow the PSS polymer brushes by means of ATRP. After activation of the polymer brushes with 1 M HCl, they

• brushes after anchoring of gallium was found to be C:O:S:Ga = 8:3.2:0.9:0.4, while no traces of chlorine were detected. From this, it was concluded that the polymer brushes contained on average one gallium per 2–3 styrene sulfonate groups. The thickness of the polymer brushes was determined by

Thermochemistry and photochemistry of spiroketals derived from indan-2-one: Stepwise processes versus coarctate fragmentations

• Götz Bucher,
• Gernot Heitmann and
• Rainer Herges

Beilstein J. Org. Chem. 2013, 9, 1668–1676, doi:10.3762/bjoc.9.191

• as 1:27. Figure 4 shows an infrared spectrum of the pyrolysis products. The organic products include formaldehyde (FA), acetaldehyde (AA), ethene (ET), o-xylylene (XY), benzocyclobutene (BC), styrene (ST), and indan-2-one (IN). Some peaks could not be assigned. The assignment of the pyrolysis

• diradical 9 [27]. The latter can then either undergo ring closure to form indan-2-one (IN), or decarbonylate to give o-xylylene (XY). The equilibrium of XY and benzocyclobutene (BC) is established in the literature [28], as well as the formation of styrene ST from BC [29]. An alternative mechanism, the

• ), ca. 40 °C (2), and ca. 60 °C (3). The argon used was of 99.999% purity. In pyrolysis experiments, the length of the pyrolysis zone was ca. 5 cm. Reference IR spectra of benzocyclobutene, styrene, indan-2-one, acetaldehyde, formaldehyde, ethene and propene in Ar matrices were independently measured

Anodic coupling of carboxylic acids to electron-rich double bonds: A surprising non-Kolbe pathway to lactones

• Robert J. Perkins,
• Hai-Chao Xu,
• John M. Campbell and
• Kevin D. Moeller

Beilstein J. Org. Chem. 2013, 9, 1630–1636, doi:10.3762/bjoc.9.186

• intramolecular electron-transfer to form the carboxy radical can occur, the difference in oxidation potentials suggests that the equilibrium would lie on the side of the oxidized olefin. Styrene substrates and additional insights With the ketene dithioacetal, vinyl sulfide, and enol ether substrates, it appeared

• clear that the initial oxidation was occurring at the olefin instead of at the carboxylate. We wondered how the reaction might change if the olefin had a higher oxidation potential. With this in mind, a series of carboxylic acid substituted styrene substrates were examined (Table 3). The first substrate

• studied was the simple styrene derivative 19a (R = H). Cyclic voltammetry suggested that in the presence of base the initial oxidation should occur at the carboxylate (Ep/2 = +1.38 in acetonitrile) since the Ep/2 value measured for substrate 19a under neutral conditions was +1.52 V versus Ag/AgCl. Several

Organotellurium-mediated living radical polymerization under photoirradiation by a low-intensity light-emitting diode

• Yasuyuki Nakamura and
• Shigeru Yamago

Beilstein J. Org. Chem. 2013, 9, 1607–1612, doi:10.3762/bjoc.9.183

• methacrylate (MMA) in the presence of ditelluride, but other typical conjugated monomers, namely, methyl acrylate and styrene, were also evaluated. TERP of these monomers proceeded efficiently in a controlled manner by adjusting the light intensity using ND filters. The results clearly demonstrate the

• = 166000, Mw/Mn = 1.15) were also prepared by changing the monomer/1 ratio under LED irradiation through a 50% transmittance ND filter (Table 2, runs 2 and 3). Next, the polymerization of styrene was examined at 90 °C, as the propagation rate constant of styrene is much lower than those of acrylates and

• efficient procedure for photoinduced TERP was developed by using a low energy (6 W) visible LED as the light source. Compared to previously employed photoinduced TERP by using a 60–500 W light source, the energy efficiency was significantly improved. As the TERP of MMA and styrene was best controlled in

Stability of SG1 nitroxide towards unprotected sugar and lithium salts: a preamble to cellulose modification by nitroxide-mediated graft polymerization

• Guillaume Moreira,
• Laurence Charles,
• Mohamed Major,
• Florence Vacandio,
• Yohann Guillaneuf,
• Catherine Lefay and
• Didier Gigmes

Beilstein J. Org. Chem. 2013, 9, 1589–1600, doi:10.3762/bjoc.9.181

• styrene polymerization mediated by this nitroxide. In the case of a polysaccharide, this degradation reaction could be detrimental to the success of the grafted polymerization. In particular, the stability of the acyclic β-phosphorylated nitroxide N-(2-methylpropyl)-N-(1-diethylphosphono-2,2

• the presence of unprotected glucose and lithium salts (LiBr and LiCl) in DMF or DMA by electron spin resonance (ESR). NMP of styrene was then performed with two SG1-based alkoxyamines (BlocBuilder MA alkoxyamine (BB)) and a cellobiose-BB alkoxyamine (called cello-SG1) with or without lithium salts

• of styrene derivatives. Another important property of TEMPO is that it is reduced by reducing sugars such as glucose [18]. The consumption of nitroxides by reducing agents such as a sugar or a polysaccharide is of prime importance when aiming at the synthesis of glycopolymers or the graft

Palladium(II)-catalyzed Heck reaction of aryl halides and arylboronic acids with olefins under mild conditions

• Tanveer Mahamadali Shaikh and
• Fung-E Hong

Beilstein J. Org. Chem. 2013, 9, 1578–1588, doi:10.3762/bjoc.9.180

• optimize the reaction conditions, a series of reactions under various combinations of bases, solvents and temperatures, employing complex 6 as precatalyst, was pursued. Bromobenzene (1a) and styrene (2a) were chosen as the model substrates in this coupling reaction and the results are presented in Table 1

• . Initially, the coupling was carried out by using 1 mol % loading of Pd-complex 6 as a precatalyst, with styrene (2a, 1 mmol), and bromobenzene (1a, 1 mmol) in DMSO (2 mL), and at ambient temperature in the presence of NaOH (1 equiv, Table 1, entry 1). The reaction did not give the coupled product 3a

• . Nevertheless, low yield (73%) of the product was obtained by reducing the reaction temperature to 50 °C. Thus, a substrate survey was conducted at 60 °C. The optimized reaction conditions were found to be the use of styrene (2a, 1 mmol), bromobenzene (1a, 1 mmol), K2CO3 (2 mmol), and precatalyst 6 (2 mol

Homolytic substitution at phosphorus for C–P bond formation in organic synthesis

• Hideki Yorimitsu

Beilstein J. Org. Chem. 2013, 9, 1269–1277, doi:10.3762/bjoc.9.143

• –carbon unsaturated bonds. Schumann reported the addition of diphenyl(triphenylstannyl)phosphine to allyl chloride, styrene, and phenylacetylene (Scheme 3) [22][23]. The addition is most likely to proceed via a radical process as the absence of AIBN leads to considerable decreases in yield. Mitchell then

The synthesis of well-defined poly(vinylbenzyl chloride)-grafted nanoparticles via RAFT polymerization

• John Moraes,
• Kohji Ohno,
• Guillaume Gody,
• Thomas Maschmeyer and
• Sébastien Perrier

Beilstein J. Org. Chem. 2013, 9, 1226–1234, doi:10.3762/bjoc.9.139

• particle surface and yields well-defined particles from a range of monomeric precursors [12]. While initial work focussed on common monomers such as styrene [13][14][15] and (meth)acrylates [14][15][16], several recent papers seek to extend this work to a greater variety of monomers [17][18][19][20][21][22

• .)) were determined by using a SEC system calibrated with narrow-molecular-weight poly(styrene) standards. Since this system results in Mn(Exp.) values relative to poly(styrene), these Mn(Exp.) were corrected by taking into account the difference in molecular weight between VBC and styrene (see Table 1

• % termination by disproportionation), assumed to be 1 in this case since poly(VBC) and poly(styrene) are considered to terminate primarily by combination). This is especially true in the case when high DPs are targeted (for instance 4,100) where the ratio of AIBN to PABTC is 5:1, which results in a substantial

Camera-enabled techniques for organic synthesis

• Steven V. Ley,
• Richard J. Ingham,
• Matthew O’Brien and
• Duncan L. Browne

Beilstein J. Org. Chem. 2013, 9, 1051–1072, doi:10.3762/bjoc.9.118

• directly in another synthetic step. For example, in a recent multistep flow synthesis of branched aldehydes from aryl iodides [98], an in-line aqueous extraction step following an ethylene-Heck reaction allowed the intermediate styrene products to be carried directly into a subsequent downstream

Carbolithiation of N-alkenyl ureas and N-alkenyl carbamates

• Julien Lefranc,
• Alberto Minassi and
• Jonathan Clayden

Beilstein J. Org. Chem. 2013, 9, 628–632, doi:10.3762/bjoc.9.70

• products that may be deprotected in situ to provide a new connective route to hindered amines. Keywords: carbamate; carbolithiation; carbometallation; organolithium; stereospecificity; styrene; urea; Introduction Enamines and N-acyl enamines are in general nucleophiles, reacting with electrophiles at the

A new intermediate in the Prins reaction

• Shinichi Yamabe,
• Takeshi Fukuda and
• Shoko Yamazaki

Beilstein J. Org. Chem. 2013, 9, 476–485, doi:10.3762/bjoc.9.51

• produced when pinene (a bicyclic monoterpene) was heated with paraformaldehyde. However, Prins performed the first rather comprehensive study of the reactions between formaldehyde and hydrocarbons with C=C double bonds [2][3]. These were styrene, pinene, camphene and anethole. As a catalyst, sulfuric acid

• , because the constituent atoms are only C, H and O in the original system, and it is a fundamental organic reaction. In this work, as the first attempt, reactions paths were traced by DFT calculations under Prins’ original conditions (styrene and formaldehyde in the acidic aqueous media). As an alkene

• , propene was also employed for comparison. From styrene, 4-phenyl-1,3-dioxane was obtained in 86% yield, and from propene 4-methyl-1,3-dioxane in 65% yield (based on H2C=O) [4]. The target of this work is to check whether the seemingly established mechanism shown in Scheme 5 holds for the two alkenes and

Inter- and intramolecular enantioselective carbolithiation reactions

• Asier Gómez-SanJuan,
• Nuria Sotomayor and
• Esther Lete

Beilstein J. Org. Chem. 2013, 9, 313–322, doi:10.3762/bjoc.9.36

• in different ways, to avoid this polymerization (Scheme 1). The first examples of intermolecular enantioselective carbolithiations of styrene derivatives were reported by Normant and Marek [9], taking advantage of the complex-induced proximity effect (CIPE). Thus, the addition of primary and

• alcohol (9) with the complex of butyllithium/diamine L2 in cumene at 0 °C, obtaining alcohol (R)-11 in 71% yield with 71% ee (Scheme 3). This is essentially opposite to the enantioselectivity obtained previously with (−)-sparteine L1 (82% yield, 83% ee in favor of (S)-11) [10]. Substituted styrene

• fully developed. On the other hand, the high reactivity of the organolithiums requires the use of stoichiometric amounts of the chiral ligand. Intermolecular carbolithiation. Carbolithiation of cinnamyl and dienyl derivatives. Carbolithiation of cinnamyl alcohol. Carbolithiation of styrene derivatives

Recent advances in transition-metal-catalyzed intermolecular carbomagnesiation and carbozincation

• Kei Murakami and
• Hideki Yorimitsu

Beilstein J. Org. Chem. 2013, 9, 278–302, doi:10.3762/bjoc.9.34

•  37). Although the cobalt-catalyzed allylzincation reactions of dialkylacetylenes resulted in low yield, the reactions of arylacetylenes provided various tri- or tetrasubstituted styrene derivatives (Scheme 38) [119][120]. Kambe reported a rare example of silver catalysis for carbomagnesiation

• compared with the reported carbomagnesiation reactions [124][125][126][127][128][129]. Hoveyda reported zirconium-catalyzed alkylmagnesiation reactions of styrene in 2001 by using primary or secondary alkyl tosylates as alkyl sources [130]. The reactions proceeded through zirconacyclopropane 4F as a key

New enzymatically polymerized copolymers from 4-tert-butylphenol and 4-ferrocenylphenol and their modification and inclusion complexes with β-cyclodextrin

• Adam Mondrzyk,
• Beate Mondrzik,
• Sabrina Gingter and
• Helmut Ritter

Beilstein J. Org. Chem. 2012, 8, 2118–2123, doi:10.3762/bjoc.8.238

• Kat.Nr. 202220602) as eluent and with a flow rate of 1 mL/min. The SEC system consists of a Gastorr BG 12 degasser (Schambeck), an Intelligent Pump AL-12 (FLOW), a S5200 sampler (Schambeck SFD) and a combination of columns (MZ Analysentechnik GmbH). The columns contain a styrene–divinylbenzene copolymer