Iridium-catalyzed intramolecular [4 + 2] cycloadditions of alkynyl halides

• Andrew Tigchelaar and
• William Tam

Beilstein J. Org. Chem. 2012, 8, 1765–1770, doi:10.3762/bjoc.8.201

• ). Deprotonation of 8 with sodium hydride, followed by trapping with propargyl bromide provided 9 in 60% yield, and a Mitsunobu reaction between 8 and sulfonamide 10 (prepared as per reference [47]) provided 11 in 74% yield. Bromination of 9 and 11 provided diene-tethered alkynyl halides 1c (57%) and 1e (83

• bromination conditions to provide 1g in 77% yield. Compounds 1a–1g were then subjected to the optimized cycloaddition conditions (Table 3). In general, the Ir-catalyzed [4 + 2] cycloadditions occurred smoothly for all substrates, forming bicyclic products 2 in good yield (75–94%) (Table 3), and in each case a

trans-2-(2,5-Dimethoxy-4-iodophenyl)cyclopropylamine and trans-2-(2,5-dimethoxy-4-bromophenyl)cyclopropylamine as potent agonists for the 5-HT₂ receptor family

• Adam Pigott,
• Stewart Frescas,
• John D. McCorvy,
• Xi-Ping Huang,
• Bryan L. Roth and
• David E. Nichols

Beilstein J. Org. Chem. 2012, 8, 1705–1709, doi:10.3762/bjoc.8.194

• precursor and subsequent bromination to provide both enantiomers of 5. Results and Discussion Racemic 4 and 5 were compared in radioligand competition assays against radiolabeled antagonists defined at the human 5-HT2A and 5-HT2C receptors and compared with racemic 1a and 1b. The results are shown in Table

• ester 7 followed by bromination of acid 9 using Br2-dioxane complex gave a good yield of bromo acid 10b. These acids were readily converted to their isocyanates using the Weinstock modification of the Curtius rearrangement [6]. Those isocyanates were heated with tert-butanol to afford the corresponding

• bromo compound 5 appeared somewhat more stable. We then followed a more efficient divergent approach to obtain the enantiomers of 5 that employed resolution of the cyclopropane carboxylic acid, followed by bromination, and then conversion to the cyclopropylamine (Scheme 3). We are aware that the use of

Stereoselective synthesis of trans-fused iridoid lactones and their identification in the parasitoid wasp Alloxysta victrix, Part I: Dihydronepetalactones

• Nicole Zimmermann,
• Robert Hilgraf,
• Lutz Lehmann,
• Daniel Ibarra and
• Wittko Francke

Beilstein J. Org. Chem. 2012, 8, 1246–1255, doi:10.3762/bjoc.8.140

• -pulegenic acid 10 via bromination, Favorskii rearrangement, and subsequent elimination (Scheme 1). Stereoselective addition of hydrochloric acid afforded the chloride 11, and subsequent elimination of hydrochloric acid gave a mixture of the methyl esters 12 and 13 (methyl trans-pulegenate) [20][21][22

On the bromination of the dihydroazulene/vinylheptafulvene photo-/thermoswitch

• Virginia Mazzanti,
• Martina Cacciarini,
• Søren L. Broman,
• Christian R. Parker,
• Magnus Schau-Magnussen,
• Andrew D. Bond and
• Mogens B. Nielsen

Beilstein J. Org. Chem. 2012, 8, 958–966, doi:10.3762/bjoc.8.108

• dihydroazulene (DHA)/vinylheptafulvene (VHF) system (with two cyano groups at C1) functions as a photo-/thermoswitch. Direct ionic bromination of DHA has previously furnished a regioselective route to a 7,8-dibromide, which by elimination was converted to a 7-bromo-substituted DHA. This compound has served as a

• central building block for functionalization of the DHA by palladium-catalyzed cross-coupling reactions. The current work explores another bromination protocol for achieving the isomeric 3-bromo-DHA and also explores the outcome of additional bromination of this compound as well as of the known 7-bromo

• -DHA. Results: Radical bromination on two different VHFs by using N-bromosuccinimide/benzoyl peroxide and light, followed by a ring-closure reaction generated the corresponding 3-bromo-DHAs, as confirmed in one case by X-ray crystallography. According to a 1H NMR spectroscopic study, the ring closure

Multistep organic synthesis of modular photosystems

• Naomi Sakai and
• Stefan Matile

Beilstein J. Org. Chem. 2012, 8, 897–904, doi:10.3762/bjoc.8.102

• . Bromination in the core with dibromocyanuric acid (31) afforded an intractable mixture containing the 2,6-dibromo NDA 32 together with lower and higher homologues [16]. However, pure product 33 could be readily isolated from this mixture after transformation of the NDAs into the core-substituted

meta-Oligoazobiphenyls – synthesis via site-selective Mills reaction and photochemical properties

• Raphael Reuter and
• Hermann A. Wegner

Beilstein J. Org. Chem. 2012, 8, 877–883, doi:10.3762/bjoc.8.99

• ) was oxidized with potassium permanganate in a 1:1 solvent mixture of pyridine/H2O, to the corresponding benzoic acid 5. The reaction proceeded with an acceptable yield of 66%. However, the resulting highly deactivated aromatic system 5 did not react even under harsh bromination conditions with NBS in

• concentrated sulfuric acid. Therefore, the reaction sequence was changed to bromination first, followed then by oxidation of the benzylic position. The bromination proceeded slowly, and after three days of stirring at 50 °C, only 53% of 2-nitro-4-tert-butyl-6-bromotoluene (7) was obtained. It turned out that

Regioselective chlorination and bromination of unprotected anilines under mild conditions using copper halides in ionic liquids

• Han Wang,
• Kun Wen,
• Nurbiya Nurahmat,
• Yan Shao,
• He Zhang,
• Chao Wei,
• Ya Li,
• Yongjia Shen and
• Zhihua Sun

Beilstein J. Org. Chem. 2012, 8, 744–748, doi:10.3762/bjoc.8.84

• Science, Shanghai, 201620, China 10.3762/bjoc.8.84 Abstract By using ionic liquids as solvents, the chlorination or bromination of unprotected anilines at the para-position can be achieved in high yields with copper halides under mild conditions, without the need for potentially hazardous operations such

• as supplementing oxygen or gaseous HCl. Keywords: halogenation; ionic liquids; oxydation; regioselectivity; solvent effects; Introduction Chlorination and bromination of aromatic rings are classical and widely performed transformations, which are useful in many multistep organic-synthesis

• procedures. Regioselectivity with electron-rich substrates such as aniline will predominantly produce para- and ortho-substitutions. However, chlorination or bromination of aniline derivatives is often performed with protected anilines. This increases both the cost of synthesis and the environmental impact

Synthesis of 2,6-disubstituted tetrahydroazulene derivatives

• Zakir Hussain,
• Henning Hopf,
• Khurshid Ayub and
• S. Holger Eichhorn

Beilstein J. Org. Chem. 2012, 8, 693–698, doi:10.3762/bjoc.8.77

• isomer. Formation of one major isomer under the given conditions could be explained through the hydrogen shifts of cycloheptatrienes by the so-called Berson–Willcott rearrangement [21]. We assume that bromination (Br2) and dehydrobromination (Et3N) of 4 resulted in the formation of an intermediate, which

Discovery of practical production processes for arylsulfur pentafluorides and their higher homologues, bis- and tris(sulfur pentafluorides): Beginning of a new era of “super-trifluoromethyl” arene chemistry and its industry

• Teruo Umemoto,
• Lloyd M. Garrick and
• Norimichi Saito

Beilstein J. Org. Chem. 2012, 8, 461–471, doi:10.3762/bjoc.8.53

• gaseous SF5Cl with acetylene, followed by bromination, dehydrobromination, and reduction with zinc, giving pentafluorosulfanylacetylene (HC≡CSF5), which was then reacted with butadiene, followed by an aromatization reaction at very high temperature, gave phenylsulfur pentafluoride [35]. Recently

Synthesis and mesomorphic properties of calamitic malonates and cyanoacetates tethered to 4-cyanobiphenyls

• Katharina C. Kress,
• Martin Kaller,
• Kirill V. Axenov,
• Stefan Tussetschläger and
• Sabine Laschat

Beilstein J. Org. Chem. 2012, 8, 371–378, doi:10.3762/bjoc.8.40

• . Starting from the corresponding diols 6a,b, 6-bromohexan-1-ol (7a) and 10-bromodecan-1-ol (7b) were obtained in moderate yields by bromination with aqueous HBr in toluene [35]. The bromides 7a,b were reacted with 4-cyano-1,1'-biphenol (8) in acetone in the presence of K2CO3 giving compounds 9a,b, bearing

Organic synthesis using (diacetoxyiodo)benzene (DIB): Unexpected and novel oxidation of 3-oxo-butanamides to 2,2-dihalo-N-phenylacetamides

• Wei-Bing Liu,
• Cui Chen,
• Qing Zhang and
• Zhi-Bo Zhu

Beilstein J. Org. Chem. 2012, 8, 344–348, doi:10.3762/bjoc.8.38

• (Scheme 2). To the best of our knowledge, there are several reports on chlorination and bromination reactions with PhI(OAc)2 and a halogen source such as TMSBr, lithium halide or pyridinium halide [32][33][34]. Also, there are several reports on the synthesis of difunctionalized acetamide derivatives [35

Dioxane dibromide mediated bromination of substituted coumarins under solvent-free conditions

• Subrata Kumar Chaudhuri,
• Sanchita Roy and
• Sanjay Bhar

Beilstein J. Org. Chem. 2012, 8, 323–329, doi:10.3762/bjoc.8.35

• /bjoc.8.35 Abstract An efficient solvent-free protocol for regioselective bromination of substituted coumarins has been developed by using dioxane dibromide as the solid brominating agent. The efficacy of the solvent-free protocol has been established. The effects of the electronic nature and location

• of the substituents on the outcome of the reaction have been rationalized with a proposed mechanism. Keywords: coumarins; solvent-free reaction; substituents; vinylic bromination; Introduction Brominated coumarins have immense synthetic, biological and industrial importance due to their occurance

• diseases [4]. Halocoumarins also exhibit insecticidal and fungicidal properties [5]. A few methods have been documented for regioselective bromination of coumarins, which include CuBr2/Al2O3 in bromobenzene under reflux [5], Br2 in glacial AcOH [6], Br2/Al2O3 under microwave irradiation [7], NBS in CHCl3

Synthesis of oleophilic electron-rich phenylhydrazines

• Aleksandra Jankowiak and
• Piotr Kaszyński

Beilstein J. Org. Chem. 2012, 8, 275–282, doi:10.3762/bjoc.8.29

• was prepared by acid-catalyzed amination of 1,2-dioctyloxybenzene (4) with BTCEAD in the presence of catalytic amounts of TfOH, according to a general literature procedure [23] (Scheme 1). The requisite bromobenzene 5a was prepared by bromination of 1,2-dioctyloxybenzene (4) [29] with CuBr2 in MeCN

• according to a literature method [30] (Scheme 4). This method is a convenient alternative to the alkylation of the less readily accessible 4-bromocatechol (7) [28]. 1-Bromo-3,4-didecylbenzene (5b) was obtained by bromination of 1,2-didecylbenzene (8) [31], obtained by the Kumada method [32], with Br2 in

• acetic anhydride (Scheme 5). Typically, the electrophilic bromination of 1,2-dialkylbenzenes results in 4,5-dibromo derivatives as the major products [33][34]. In contrast, the present method permits selective monobromination, although the bromo derivative 5b was isolated only in about 85% purity. The

Derivatives of phenyl tribromomethyl sulfone as novel compounds with potential pesticidal activity

• Krzysztof M. Borys,
• Maciej D. Korzyński and
• Zbigniew Ochal

Beilstein J. Org. Chem. 2012, 8, 259–265, doi:10.3762/bjoc.8.27

• ). Reaction of 4-chlorothiophenol (2) with sodium hydroxide and sodium chloroacetate (obtained in situ by neutralization of chloroacetic acid with NaOH solution) afforded 2-(4-chlorophenylthio)acetic acid (3). Oxidative bromination of 3 with sodium hypobromite gave sulfone 1 in moderate (57%) overall yield

• of 4-chlorothiophenol (2) with dimethyl sulfate, followed by treatment of the resulting product 5 with hydrogen peroxide and glacial acetic acid. Next, bromination of the methyl group of 4 was achieved by using either sodium hypobromite (Scheme 2, method B) or bromine chloride (Scheme 2, method C

• ), both of which have been extensively researched by us as halogenating agents. The overall yields of tribromomethyl sulfone 1 obtained by this pathway amounted to 86% and 85% (starting from 2) for the NaOBr and BrCl method of bromination, respectively. The next step in the functionalization of sulfone 1

Fifty years of oxacalix[3]arenes: A review

• Kevin Cottet,
• Paula M. Marcos and
• Peter J. Cragg

Beilstein J. Org. Chem. 2012, 8, 201–226, doi:10.3762/bjoc.8.22

• Scheme 2, the phenolic position of a monomeric precursor is protected with methyl chloromethyl ether (MOMCl). A different monomer is then protected with 2,2-dimethoxypropane, in the presence of TsOH. This links one methylol group to the phenol, leaving the second open to bromination with CBr4 and PPh3

• bromination of the methylol-terminated oxacalix[3]arene, employing PBr3, and coupling with 1,3,5-tris(methanethiol)benzene in the presence of Cs2CO3 in THF. 3.2.4 Upper-rim coordination chemistry: The functionalization of the upper rims of oxacalix[3]arenes has also been achieved through classical inorganic

Sexithiophenes as efficient luminescence quenchers of quantum dots

• Christopher R. Mason,
• Yang Li,
• Paul O’Brien,
• Neil J. Findlay and
• Peter J. Skabara

Beilstein J. Org. Chem. 2011, 7, 1722–1731, doi:10.3762/bjoc.7.202

• sexithiophenes 1a and 1b (Scheme 1) began in a similar fashion to our previously published methodology for the synthesis of compounds 2a and 2b [14]. After the formation of terthiophenes 3 [14], bromination with NBS under acidic conditions afforded the key intermediates 4a and 4b in high yields (97% and 88

Novel fatty acid methyl esters from the actinomycete Micromonospora aurantiaca

• Jeroen S. Dickschat,
• Hilke Bruns and
• Ramona Riclea

Beilstein J. Org. Chem. 2011, 7, 1697–1712, doi:10.3762/bjoc.7.200

• bromination of 2-methylpentan-1-ol (125) and subsequent Cu-catalysed 1,4-addition of the respective Grignard reagent to methyl acrylate, resulting in methyl 5-methyloctanoate (127, Scheme 4). Reduction to the aldehyde 129 via the alcohol 128, addition of methylmagnesium bromide, and bromination resulted in

Photochemical and thermal intramolecular 1,3-dipolar cycloaddition reactions of new o-stilbene-methylene-3-sydnones and their synthesis

• Kristina Butković,
• Željko Marinić,
• Krešimir Molčanov,
• Biserka Kojić-Prodić and
• Marija Šindler-Kulyk

Beilstein J. Org. Chem. 2011, 7, 1663–1670, doi:10.3762/bjoc.7.196

• -cyanotoluene (see Supporting Information File 1 for full experimental data). Bromination of o-cyanotoluene afforded 2-(bromomethyl)benzonitrile (4) [24], which was transformed to triphenylphosphonium salt 5 [25] followed by Wittig reaction with 4-methylbenzaldehyde to 2-(4-methylstyryl)benzonitrile (6a,b) [26

The application of a monolithic triphenylphosphine reagent for conducting Appel reactions in flow microreactors

• Kimberley A. Roper,
• Heiko Lange,
• Anastasios Polyzos,
• Malcolm B. Berry,
• Ian R. Baxendale and
• Steven V. Ley

Beilstein J. Org. Chem. 2011, 7, 1648–1655, doi:10.3762/bjoc.7.194

• purification. Keywords: Appel reaction; bromination; flow chemistry; solid-supported reagent; triphenylphosphine monolith; Introduction Flow chemistry is well-established as a useful addition to the toolbox of the modern research chemist, with advantages accrued through increased efficiency, reproducibility

• was then loaded with carbon tetrabromide to give the active species with which to perform the Appel bromination reaction. To achieve this, carbon tetrabromide in dichloromethane [46] was recirculated through the monolith for 16 hours at room temperature (Scheme 2), resulting in a colour change from

• monolith was placed in-line with the unloaded triphenylphosphine monolith in the recycling procedure with carbon tetrabromide. Bromination reactions in flow with the loaded triphenylphosphine monolith With the functionalised, active brominating monolith in hand, the transformation of an alcohol into the

Natural product biosyntheses in cyanobacteria: A treasure trove of unique enzymes

• Jan-Christoph Kehr,
• Douglas Gatte Picchi and
• Elke Dittmann

Beilstein J. Org. Chem. 2011, 7, 1622–1635, doi:10.3762/bjoc.7.191

• biosynthesis include a six-carbon carboxylic acid unit as starter moiety. In vitro studies revealed the activation of either hexanoic, hexenoic or hexynoic acids at the JamA enzyme, whereas bromination clearly succeeded thioester formation [43]. Curacin A Curacin A (9) was originally isolated from a Lyngbya

Structural conditions required for the bridge lithiation and substitution of a basic calix[4]arene

• Conrad Fischer,
• Wilhelm Seichter and
• Edwin Weber

Beilstein J. Org. Chem. 2011, 7, 1602–1608, doi:10.3762/bjoc.7.188

• decade two main preparative routes for the methylene-bridge substitution of p-tert-butyltetramethoxycalix[4]arene have been established: A protocol described by Biali et al. yields a stabilized methylene carbocation through bromination that is ready for electrophilic substitution under SN1 conditions [3

Functionalization of anthracene: A selective route to brominated 1,4-anthraquinones

• Kiymet Berkil Akar,
• Osman Cakmak,
• Orhan Büyükgüngör and
• Ertan Sahin

Beilstein J. Org. Chem. 2011, 7, 1036–1045, doi:10.3762/bjoc.7.118

• derivatives that are difficult to prepare by other routes. The studies also reveal the broad range of reactivity and selectivity of the stereoisomeric anthracene derivatives. Keywords: anthracene derivatives; anthracene-1,4-dione; aromatization; bromination; bromoanthracene; methoxyanthracene; silver-induced

• substitution; Introduction Our sustained interest in benzenoid aromatic compounds with high bromine content has led to the development of a regio- and stereoselective bromination method for aromatic compounds. Recently, we demonstrated the selective bromination of 9,10-dibromoanthracene (1) to give

Recent advances in the gold-catalyzed additions to C–C multiple bonds

• He Huang,
• Yu Zhou and
• Hong Liu

Beilstein J. Org. Chem. 2011, 7, 897–936, doi:10.3762/bjoc.7.103

• compatible with electrophilic fluorinating reagents. Furthermore, it is possible to couple the 6-endo-dig cyclization with iodination and bromination of the presumed vinyl–gold intermediate. However, attempted alkoxychlorination with N-chlorosuccinimide failed. Intermolecular hydroalkoxylation of non

Isotopic labelling studies for a gold-catalysed skeletal rearrangement of alkynyl aziridines

• Paul W. Davies,
• Nicolas Martin and
• Neil Spencer

Beilstein J. Org. Chem. 2011, 7, 839–846, doi:10.3762/bjoc.7.96

• stabilising B. The substrates were prepared by Sonogashira reaction between propargyl alcohol and the appropriately substituted iodobenzene substrate 22, 23 (Scheme 12). Functional group interconversion of the alcohols by bromination and substitution results in the sulfonium salts 28, 29 which were reacted

Synthesis of novel 5-alkyl/aryl/heteroaryl substituted diethyl 3,4-dihydro-2H-pyrrole-4,4-dicarboxylates by aziridine ring expansion of 2-[(aziridin-1-yl)-1-alkyl/aryl/heteroaryl-methylene]malonic acid diethyl esters

• Satish S. More,
• T. Krishna Mohan,
• Y. Sateesh Kumar,
• U. K. Syam Kumar and
• Navin B. Patel

Beilstein J. Org. Chem. 2011, 7, 831–838, doi:10.3762/bjoc.7.95

• quantitative yields, either by reduction with sodium borohydride, or by catalytic hydrogenation using platinum on carbon [33][34]. The pyrrolines can be aromatized either by a two step procedure (i) NBS bromination and (ii) dehydrohalogenation in basic medium [35][36][37], or by dehydrogenation with Pd/C [38