Copper-catalyzed stereoselective conjugate addition of alkylboranes to alkynoates

• Takamichi Wakamatsu,
• Kazunori Nagao,
• Hirohisa Ohmiya and
• Masaya Sawamura

Beilstein J. Org. Chem. 2015, 11, 2444–2450, doi:10.3762/bjoc.11.265

• mode. The syn stereoselectivity was excellent regardless of the substrate structure, and a variety of functional groups were tolerated in both the alkylborane and the alkynoate. Results and Discussion Alkylborane 2a (0.275 mmol), which was obtained via hydroboration of styrene (1a) with the 9

• alkylboranes through in situ alkene hydroboration is an attractive feature of this protocol and various functional groups are tolerated in both the alkylborane and alkynoate substrates. Experimental The reaction shown in Scheme 1 was conducted in a similar manner as described before [15]. Styrene (1a, 33 μL

Recent developments in copper-catalyzed radical alkylations of electron-rich π-systems

• Kirk W. Shimkin and
• Donald A. Watson

Beilstein J. Org. Chem. 2015, 11, 2278–2288, doi:10.3762/bjoc.11.248

• for the reaction. These types of ligands in conjunction with copper catalysts are known to promote the formation of stabilized carbon-centered radicals [14]. In this reaction, the putative tertiary radical undergoes addition to a styrene derivative, creating a stabilized benzylic radical. Akin to

• -withdrawing groups including esters, ketones and nitro groups were tolerated in the alkyl bromide coupling partner (Scheme 10). In addition, the reaction shows excellent functional group compatibility with respect to the styrene coupling partner, tolerating ethers, nitriles, chlorides and amines. Notably

• radicals, these strategies have elegantly circumvented this problem and have expanded the scope of alkyl cross-coupling reactions. Nishikata has subsequently expanded the utility of this reaction manifold by elegant tailoring of the radical donor and acceptor [36]. If the styrene radical acceptor bears an

Evidencing an inner-sphere mechanism for NHC-Au(I)-catalyzed carbene-transfer reactions from ethyl diazoacetate

• Manuel R. Fructos,
• Juan Urbano,
• M. Mar Díaz-Requejo and
• Pedro J. Pérez

Beilstein J. Org. Chem. 2015, 11, 2254–2260, doi:10.3762/bjoc.11.245

• Abstract Kinetic experiments based on the measurement of nitrogen evolution in the reaction of ethyl diazoacetate (N2CHCO2Et, EDA) and styrene or methanol catalyzed by the [IPrAu]+ core (IPr = 1,3-bis(diisopropylphenyl)imidazole-2-ylidene) have provided evidence that the transfer of the carbene group

• CHCO2Et to the substrate (styrene or methanol) takes place in the coordination sphere of Au(I) by means of an inner-sphere mechanism, in contrast to the generally accepted proposal of outer-sphere mechanisms for Au(I)-catalyzed reactions. Keywords: carbene transfer; inner sphere; gold catalysis; O–H

• )phenyl)borate) as a halide scavenger, induced the incorporation of the :CHCO2Et group from N2CHCO2Et to styrene (Scheme 2a) or methanol (Scheme 2b), among others. With the former, in addition to the formation of the expected cyclopropanes, a second type of product was observed, derived from the

Beyond catalyst deactivation: cross-metathesis involving olefins containing N-heteroaromatics

• Kevin Lafaye,
• Cyril Bosset,
• Lionel Nicolas,
• Amandine Guérinot and
• Janine Cossy

Beilstein J. Org. Chem. 2015, 11, 2223–2241, doi:10.3762/bjoc.11.241

• , the addition of amino additives such as pyridine, morpholine, Et3N or DBU was shown to be detrimental to the G-HII-catalyzed dimerization of styrene (Table 2). Moderate to poor yields in stilbene 7’ were obtained and the value of the yields was correlated with the pKa of the couple ammonium/amine. An

• increased Brønsted basicity of the amine seemed to induce a faster deactivation of the catalyst. In addition, when the self-metathesis of styrene was performed in the presence of pyrrolidine, DBU or Et3N, olefin 22 was formed as the major product (Scheme 9). To explain these observations, a deactivation

• -induced decomposition of GII in RCM conditions. Deactivation of methylidene 2 in the presence of pyridine. Reaction of G-HII with various amines. Formation of olefin 22 from styrene. Hypothetic deactivation pathway of G-HII. RCM of dienic pyridinium salts. Synthesis of polycyclic scaffolds using RCM

Olefin metathesis in air

• Lorenzo Piola,
• Fady Nahra and
• Steven P. Nolan

Beilstein J. Org. Chem. 2015, 11, 2038–2056, doi:10.3762/bjoc.11.221

• reaction with styrene, avoiding the use of hazardous diazo compound 7 [82]. Towards the end of 2013, a report by Olszewski, Skowerski and co-workers showed how a variety of commercially available catalysts (Figure 12) could be employed in air with nondegassed ACS grade green solvents. Their results were in

Recent applications of ring-rearrangement metathesis in organic synthesis

• Sambasivarao Kotha,
• Milind Meshram,
• Priti Khedkar,
• Shaibal Banerjee and
• Deepak Deodhar

Beilstein J. Org. Chem. 2015, 11, 1833–1864, doi:10.3762/bjoc.11.199

• presence of n-BuLi provided styrylfuran 270 in 72% yield. The DA reaction of styrene derivative 270 with DMAD 129 at 40 °C yielded oxabridged compound 268. Another route to 268 involves a DA reaction of 265 with DMAD at 55 °C for longer reaction time (3 days) and sequential Wittig olefination. The spiro

• olefination to result the required oxabicyclo[3.2.1]octene derivative 338. Later, the RRM of the styrene derivative 338 with catalyst 2 delivered a highly-functionalized spiro-pyran derivative 339 in 48% yield (Scheme 74). The Dysiherbaine and acetogenin groups of natural products have been synthesized by the

Polythiophene and oligothiophene systems modified by TTF electroactive units for organic electronics

• Alexander L. Kanibolotsky,
• Neil J. Findlay and
• Peter J. Skabara

Beilstein J. Org. Chem. 2015, 11, 1749–1766, doi:10.3762/bjoc.11.191

• ) [5] and organic field effect transistors (OFETs) [6][7], whereas the PEDOT:poly(styrene sulfonate) salt (PEDOT:PSS) was originally investigated for antistatic applications but is now commercially available for its use as a hole-injecting/collecting material for organic light emitting diodes (OLEDs

Grubbs–Hoveyda type catalysts bearing a dicationic N-heterocyclic carbene for biphasic olefin metathesis reactions in ionic liquids

• Maximilian Koy,
• Hagen J. Altmann,
• Benjamin Autenrieth,
• Wolfgang Frey and
• Michael R. Buchmeiser

Beilstein J. Org. Chem. 2015, 11, 1632–1638, doi:10.3762/bjoc.11.178

• utmost interest. Recycling experiments carried out with M1 revealed that with the aid of 2-(2-PrO)-styrene, Ru-2 could be used in three consecutive cycles (Scheme 2). Over these three cycles, the number-average molecular weight, Mn, significantly decreased while PDIs increased from 2.1 to 3.0. Again, Ru

• on a Bruker Daltonics Microtof Q mass spectrometer at the Institute of Organic Chemistry at the University of Stuttgart. 1,3-Bis(2,6-dimethyl-4-dimethylaminophenyl)-4,5-dihydroimidazol-2-ylidene (1) [21], 2-(2-PrO)-styrene [23][24], M3 [26] and M4 [27] were prepared according to the literature. RuCl2

• via syringe in one portion and the reaction mixture was allowed to stir at 50 °C for 1.5 h. Then a solution of 2-(2-PrO)-styrene in anhydrous toluene (1 mL, 1 M) was added. The reaction mixture was stirred at 50 °C for 1 h. The two phases were allowed to separate. The organic phase was poured into

Robust bifunctional aluminium–salen catalysts for the preparation of cyclic carbonates from carbon dioxide and epoxides

• Yuri A. Rulev,
• Zalina Gugkaeva,
• Victor I. Maleev,
• Michael North and
• Yuri N. Belokon

Beilstein J. Org. Chem. 2015, 11, 1614–1623, doi:10.3762/bjoc.11.176

• diethylaluminium chloride (Scheme 3), affording complexes 1 and 2 in 96% and 91% yields respectively. These complexes could be used without any additional purification. Styrene oxide was used as a model substrate to test the catalytic efficiency of complexes 1 and 2 in the coupling reaction with carbon dioxide

• % conversion of styrene oxide to the corresponding cyclic carbonate after 24 hours, whereas complex 1 gave only 47% conversion under the same conditions (Table 1, entries 4 and 12). Increasing either the temperature of the reaction or the carbon dioxide pressure had positive effects on the catalytic

• that this catalyst was almost inactive in the reaction of styrene oxide with carbon dioxide (Table 1, entry 14). After addition of tetrabutylammonium iodide (5 mol %) as a cocatalyst, the conversion was increased to 80% (Table 1, entry 15), which was close to the performance of catalyst 2 (Table 1

Preparative semiconductor photoredox catalysis: An emerging theme in organic synthesis

• David W. Manley and
• John C. Walton

Beilstein J. Org. Chem. 2015, 11, 1570–1582, doi:10.3762/bjoc.11.173

• adducts 46 in high yields, but steric hindrance in branched thiols was deleterious. Alkenes with electron-releasing and electron-withdrawing substituents were tolerated. Interestingly, SCPC reactions also took place such that ethane and propanedithiols 47 coupled with two styrene molecules affording 1,2

Consequences of the electronic tuning of latent ruthenium-based olefin metathesis catalysts on their reactivity

• Karolina Żukowska,
• Eva Pump,
• Aleksandra E. Pazio,
• Krzysztof Woźniak,
• Luigi Cavallo and
• Christian Slugovc

Beilstein J. Org. Chem. 2015, 11, 1458–1468, doi:10.3762/bjoc.11.158

• corresponding polymer was characterized by a number average molecular weight (Mn) of 557.0 kg·mol−1 (polydispersity index, PDI = 1.9) as examined by size exclusion chromatography (SEC) in THF against poly(styrene) standards. Initiator 15 gave 93% monomer-conversion and the resulting polymer exhibited a Mn of

• responsible for an altered order of initiation behavior when polymerizations are conducted in bulk. Experimental Preparation of 14 and 15. Precursor complex 1 (0.5 mmol, 475 mg) and the respective styrene derivative (0.55 mmol) were put in a Schlenk tube under argon. Reagents were dissolved in anhydrous

Antioxidant potential of curcumin-related compounds studied by chemiluminescence kinetics, chain-breaking efficiencies, scavenging activity (ORAC) and DFT calculations

• Adriana K. Slavova-Kazakova,
• Silvia E. Angelova,
• Timur L. Veprintsev,
• Petko Denev,
• Davide Fabbri,
• Maria Antonietta Dettori,
• Maria Kratchanova,
• Vladimir V. Naumov,
• Aleksei V. Trofimov,
• Rostislav F. Vasil’ev,
• Giovanna Delogu and
• Vessela D. Kancheva

Beilstein J. Org. Chem. 2015, 11, 1398–1411, doi:10.3762/bjoc.11.151

• each other. Barclay et al. [18] studied the antioxidant mechanism of curcumin (1) and dehydrozingerone (2) (a half-curcumin molecule) in controlled regime of styrene oxidation in chlorobenzene. The authors observed that kA value of 1 is twice as high as that of 2. This result is in excellent agreement

Intermolecular addition reactions of N-alkyl-N-chlorosulfonamides to unsaturated compounds

• Gerold Heuger and
• Richard Göttlich

Beilstein J. Org. Chem. 2015, 11, 1226–1234, doi:10.3762/bjoc.11.136

• alkenes under copper(I) catalysis. In reactions of styrene derivatives with terminal double bonds the addition products were obtained in excellent yield and high regioselectivity. Lower yields are obtained in addition reactions to non-aromatic alkenes. The reaction most likely proceeds via a redox

• to higher or led in distinctly lower yields to the N-chloro compounds. We chose styrene as the model compound for the first addition reactions of N-chlorosulfonamide 2a and used the complex [(MeCN)4Cu]PF6 as catalyst (Scheme 2). However even after a prolonged reaction time of 24 hours no addition

• better results whilst rising the temperature to 75 °C and adding an excess of styrene increased the yield to 43%. Under these conditions the N-chlorosulfonamide 2a was completely consumed, undesired products were the sulfonamide 1a as well as oligostyrenes. The oligomerisation should be slowed down by

Hetero-Diels–Alder reactions of hetaryl and aryl thioketones with acetylenic dienophiles

• Grzegorz Mlostoń,
• Paulina Grzelak,
• Maciej Mikina,
• Anthony Linden and
• Heinz Heimgartner

Beilstein J. Org. Chem. 2015, 11, 576–582, doi:10.3762/bjoc.11.63

• reaction with dienophiles such as maleic anhydride, acrylonitrile, styrene, and α-chloroacrylonitrile [14][15]. In the latter case, the stabilization of the initially formed cycloadduct occurred via HCl elimination, whereas, in the other cases, the 1,3-hydrogen shift led to rearomatized products. In our

Photocatalytic nucleophilic addition of alcohols to styrenes in Markovnikov and anti-Markovnikov orientation

• Martin Weiser,
• Sergej Hermann,
• Alexander Penner and
• Hans-Achim Wagenknecht

Beilstein J. Org. Chem. 2015, 11, 568–575, doi:10.3762/bjoc.11.62

• ) and styrene (6) into the Markovnikov- and anti-Markovnikov-type products was selectively achieved with 1-(N,N-dimethylamino)pyrene (Py) and 1,7-dicyanoperylene-3,4:9,10-tetracarboxylic acid bisimide (PDI) as photoredox catalysts. The regioselectivity was controlled by the photocatalyst. For the

• -Markovnikov-type addition of cyanide to styrene [18]. Recently, we showed by a library of different chromophores that 1-(N,N-dimethylamino)pyrene (Py) can be applied as photocatalyst for the nucleophilic addition of methanol to styrene derivatives into the Markovnikov orientation [19]. Most recently, Nicewicz

• et al. published the hydrofunctionalization of alkenes to the anti-Markovnikov products by photoredox catalysis using 9-mesityl-10-methylacridinium [20][21]. Herein, we want to present our complementary approach to perform inter- and intramolecular nucleophilic additions of alcohols to styrene

Ruthenium-catalyzed C–H activation of thioxanthones

• Danny Wagner and
• Stefan Bräse

Beilstein J. Org. Chem. 2015, 11, 431–436, doi:10.3762/bjoc.11.49

• (styrene, vinyl/allyl ethers, perfluoroalkylethenes) failed since they polymerize during the reaction. Extension of the unsymmetrical heterocycle system 1b to the unsubstituted thioxanthone (1a) was also successful: Depending on the amount of alkene, mono- (Table 2, entry 3) or 1,8-disubstituted

Matsuda–Heck reaction with arenediazonium tosylates in water

• Ksenia V. Kutonova,
• Marina E. Trusova,
• Andrey V. Stankevich,
• Pavel S. Postnikov and
• Victor D. Filimonov

Beilstein J. Org. Chem. 2015, 11, 358–362, doi:10.3762/bjoc.11.41

• ]. In 2012, examples of the Matsuda–Heck arylation of styrene and acrylic acid esters with arenediazonium tetrafluoroborates in water and catalyzed with in situ formed Pd nanoparticles [5] or agarose-supported Pd nanoparticles [6] have been reported. Superparamagnetic Pd–ZnFe2O4 MNPs have been shown to

• be effective catalysts for the Matsuda–Heck arylation of styrene and ethyl acrylate in water [7]. It is noteworthy that these catalysts are not commercially available and must be synthesized from Pd(OAc)2. Roglands et al. prepared a range of tert-butyl cinnamates and stilbenes from arenediazonium

• bromide [20] under harsh conditions with modest yields. The synthesized 3-chloropropyl cinnamates 3ba, 3bb, 3bg were not reported before. Styrene (1c) is less reactive than acrylates in Heck-type reactions. Notwithstanding, a range of stilbenes was synthesized stereoselectively with good yields and purity

Switching the reaction pathways of electrochemically generated β-haloalkoxysulfonium ions – synthesis of halohydrins and epoxides

• Akihiro Shimizu,
• Ryutaro Hayashi,
• Yosuke Ashikari,
• Toshiki Nokami and
• Jun-ichi Yoshida

Beilstein J. Org. Chem. 2015, 11, 242–248, doi:10.3762/bjoc.11.27

• , Br and I were introduced to a primary carbon atom, whereas OH was introduced to a secondary carbon atom. In the case of styrene derivative 2d, Br and I were introduced to a secondary carbon, whereas OH was introduced to the benzyl carbon. DMSO seems to attack the more positively charged carbon of the

Properties of cationic monosubstituted tetraalkylammonium cyclodextrin derivatives – their stability, complexation ability in solution or when deposited on solid anionic surface

• Martin Popr,
• Sergey K. Filippov,
• Nikolai Matushkin,
• Juraj Dian and
• Jindřich Jindřich

Beilstein J. Org. Chem. 2015, 11, 192–199, doi:10.3762/bjoc.11.20

• polystyrene. It showed high deposition of cationic PEMPDA-β-CD, but also of the native β-CD. The results indicated that undesired inclusion of the styrene moieties in the CD cavity takes place, which blocks the cavity from further complexation of guest molecules from solution. At this point we replaced Dowex

Redox active dendronized polystyrenes equipped with peripheral triarylamines

• Toshiki Nokami,
• Naoki Musya,
• Tatsuya Morofuji,
• Keiji Takeda,
• Masahiro Takumi,
• Akihiro Shimizu and
• Jun-ichi Yoshida

Beilstein J. Org. Chem. 2014, 10, 3097–3103, doi:10.3762/bjoc.10.326

• dendronized polystyrene 8a was characterized using MALDI–TOF MS analysis. Six peak groups were observed, as shown in Figure 4. The peak occurring at 10,573 Da [M + Ag+] is derived from 11 dendritic substituents (815 Da × 11), 14 styrene units (103 Da × 11 + 104 Da × 3), and a butyl group (58 Da), which was

• derived from the initiator at the end of the polystyrene. The broader peaks seem to be attributable to two isotopes of the bromo groups (79 and 81 Da), and the small peak separation 101–103 Da is consistent with the molecular weight of styrene monomer (104 Da). The MS analysis indicated that 6 reacted

Superoxide chemistry revisited: synthesis of tetrachloro-substituted methylenenortricyclenes

• Basavaraj M. Budanur and
• Faiz Ahmed Khan

Beilstein J. Org. Chem. 2014, 10, 2531–2538, doi:10.3762/bjoc.10.264

• the series of DA adducts 3/4 from pentachloro-5-methylcyclopentadiene 1 and corresponding dienophiles 2 [38][39][40] by heating at 120–130 °C in a sealed tube. Styrene derivatives containing groups like methoxy, alkyl, naphthyl, and biphenyl (Table 1, entries 1–4, 6–9 ), methyl vinyl ketone (Table 1

• , entry 13) and cyclooctene (Table 1, entry 15) have furnished DA adducts in excellent yields and good diastereoselectivity ~4:1 (anti:syn) in 6–15 h. Some dienophiles such as p-nitrostyrene (Table 1, entry 5), 4-vinylpyridine (Table 1, entry 10), chlorinated styrene (Table 1, entry 12) and acrylonitrile

• , substituted styrene adducts were subjected to the reaction with KO2 (3 equiv) in DMSO and the results are summarized in Scheme 2. The substrates endowed with electron donating groups, for example anti-adduct 3b gave methylenenortricyclene 5b, whereas its syn-isomer 4b, after consumption of all the starting

Phosphinocyclodextrins as confining units for catalytic metal centres. Applications to carbon–carbon bond forming reactions

• Matthieu Jouffroy,
• Rafael Gramage-Doria,
• David Sémeril,
• Dominique Armspach,
• Dominique Matt,
• Werner Oberhauser and
• Loïc Toupet

Beilstein J. Org. Chem. 2014, 10, 2388–2405, doi:10.3762/bjoc.10.249

• -catalysed Mizoroki–Heck coupling reactions between aryl bromides and styrene on one hand, and the rhodium-catalysed asymmetric hydroformylation of styrene on the other hand. The inability of both chiral ligands to form standard bis(phosphine) complexes under catalytic conditions was established by high

• -pressure NMR studies and shown to have a deep impact on the two carbon–carbon bond forming reactions both in terms of activity and selectivity. For example, when used as ligands in the rhodium-catalysed hydroformylation of styrene, they lead to both high isoselectivity and high enantioselectivity. In the

• no other option, but to adopt a linear P–Rh–H arrangement (Figure 7), so that steric interactions between the carbonyl ligands and the cavity inner wall are reduced to the maximum. Hydroformylation of styrene The results of the above HP-NMR studies prompted us to investigate the properties of HUGPHOS

Relay cross metathesis reactions of vinylphosphonates

• Raj K. Malla,
• Jeremy N. Ridenour and
• Christopher D. Spilling

Beilstein J. Org. Chem. 2014, 10, 1933–1941, doi:10.3762/bjoc.10.201

• via ozonolysis to the aldehyde 6, a known intermediate [17][18] on route to (−)-centrolobine (8). An alternative approach could involve an alkene cross metathesis reaction between the vinylphosphonate and a styrene (5 to 7). Since substituted vinylphosphonates are reluctant to participate in cross

• readily engage in the metathesis reaction. Thus, reaction of the mono-allyl vinylphosphonate 21a with 5 equivalents of styrene using 10 mol % Grubbs second generation catalyst and 10 mol % CuI in refluxing CH2Cl2 for two hours gave tetrahydropyran 25 in 82% isolated yield (Scheme 7). Similarly, reaction

• ring closing metathesis (RCM) to generate the oxaphosphole 22 and a new metal alkylidene 34. The sequence is completed by reaction of the metal alkylidene 34 with the metathesis partner (styrene) to give the tetrahydropyran 25. The formation of the dimeric product 27 is probably the result of a

Facile synthesis of 1-alkoxy-1H-benzo- and 7-azabenzotriazoles from peptide coupling agents, mechanistic studies, and synthetic applications

• Mahesh K. Lakshman,
• Manish K. Singh,
• Mukesh Kumar,
• Raghu Ram Chamala,
• Vijayender R. Yedulla,
• Domenick Wagner,
• Evan Leung,
• Lijia Yang,
• Asha Matin and
• Sadia Ahmad

Beilstein J. Org. Chem. 2014, 10, 1919–1932, doi:10.3762/bjoc.10.200

• of 1° and 2° alcohols underwent reaction with Bt-OTs giving good to excellent yields of 1-alkoxy-1H-benzotriazoles. Some notable results are as follows. Despite the leaving group ability of BtO−, elimination to styrene does not appear to be a significant problem in the reactions with the isomeric

Supercritical carbon dioxide: a solvent like no other

• Jocelyn Peach and
• Julian Eastoe

Beilstein J. Org. Chem. 2014, 10, 1878–1895, doi:10.3762/bjoc.10.196

• factor of around 5 to 400 through the addition of fluoroacrylate and styrene copolymers at a range of polymer concentrations (1–5 w/w %) and styrene:fluoroacrylate molar ratios [100]. Cloud point pressures indicated that polymer solubility decreased with increased concentrations of styrene in the polymer

• chain, due to poor solvency of styrene in CO2. It was anticipated that π–π stacking between phenyl groups is a main contributor to the viscosity increase, through its provision of a fundamental intermolecular force needed to raise viscosity in a system. The optimum composition of polymers for viscosity

• enhancement in this study was 29 mol % styrene:71 mol % fluoroacrylate. Surfactant headgroups – counterion effects: An important area of investigation is salt addition and counterion exchange in surfactant headgroups. The effects of counterion exchange from Na+ to M2+ ions ( Mg2+, Ca2+, Co2+, Ni2+, Cu2+ and