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

Syntheses and properties of thienyl-substituted dithienophenazines

• Annemarie Meyer,
• Eva Sigmund,
• Friedhelm Luppertz,
• Gregor Schnakenburg,
• Immanuel Gadaczek,
• Thomas Bredow,
• Stefan-S. Jester and
• Sigurd Höger

Beilstein J. Org. Chem. 2010, 6, 1180–1187, doi:10.3762/bjoc.6.135

• prepared first 3,3’-thenil (2) by metalation of 3-bromothiophene and reaction with dimethyl oxalate [19]. Subsequent oxidative intramolecular thiophene-thiophene coupling [20] with FeCl3 yielded 3 as a dark red (nearly black) solid. Bromination of 3 with bromine in acetic acid/chloroform gave 4 in nearly

• oxalyl chloride [23][24]. Bromination of 7 with NBS failed, however, the reaction with bromine under similar conditions as described for 4 afforded 8 in quantitative yields. Both routes towards the brominated bithiophene-diketones gave high overall yields and can be scaled up easily. Condensation of the

Conjugated polymers containing diketopyrrolopyrrole units in the main chain

• Bernd Tieke,
• A. Raman Rabindranath,
• Kai Zhang and
• Yu Zhu

Beilstein J. Org. Chem. 2010, 6, 830–845, doi:10.3762/bjoc.6.92

• arylamine. The bromination of aryl units is important for the subsequent palladium-catalyzed coupling reaction. If the aryl unit is thiophene, direct bromination with N-bromosuccinimide is possible to yield monomer M-3 [16]. For the preparation of conjugated DPP-based polymers, palladium-catalyzed

Addition of lithiated enol ethers to nitrones and subsequent Lewis acid induced cyclizations to enantiopure 3,6-dihydro-2H-pyrans – an approach to carbohydrate mimetics

• Fabian Pfrengle and
• Hans-Ulrich Reissig

Beilstein J. Org. Chem. 2010, 6, No. 75, doi:10.3762/bjoc.6.75

• dihydroxylation or bromination. Bicyclic enol ether 19 was oxidatively cleaved to provide the highly functionalized ten-membered ring lactone 20. The synthesized enantiopure aminopyrans 24, 26, 28 and 30 can be regarded as carbohydrate mimetics. Trimeric versions of 24 and 28 were constructed via their attachment

• -methylmorpholinoxide-system afforded α-hydroxyketone 9 via in situ hydrolysis of an initially formed hemiacetal. Bromination with NBS in MeCN/H2O led to α-bromoketone 10 and its desilylated derivative 11 as single diastereomers. We presume that the NBS attacks the enol ether moiety, as is also the case with the

• initially formed in the dihydroxylation was observed leading to an inseparable mixture of compounds 13 and 14. The TBS-protection group was completely removed during bromination of the enol ether moiety with the formation of compound 15 in good yield [20]. The internal enol ether moiety of the bicyclic

Anion receptors containing thiazine-1,1-dioxide heterocycles as hydrogen bond donors

• Hong-Bo Wang,
• James A. Wisner and
• Michael C. Jennings

Beilstein J. Org. Chem. 2010, 6, No. 50, doi:10.3762/bjoc.6.50

• ,α′-Dibromo-1,3-diacetylbenzene (5) and α,α′-dibromo-2,6-diacetylpyridine (6) are both simply generated by bromination of the corresponding diacylarenes. The reaction of either dibromide with α-mercaptoacetophenone in the presence of 2,6-lutidine yields dithioether intermediates 7 and 8. Oxidation of

Efficient and improved synthesis of Telmisartan

• A. Sanjeev Kumar,
• Samir Ghosh and
• G. N. Mehta

Beilstein J. Org. Chem. 2010, 6, No. 25, doi:10.3762/bjoc.6.25

• published procedures start from this compound. In designing an alternative synthesis of Telmisartan our goal was to minimize the use of expensive and hazardous metals, circumvent the bromination step, and increase the overall efficiency of the synthesis. This was accomplished by reversing the order of the

Solvent-free phase-vanishing reactions with PTFE (Teflon^®) as a phase screen

• Kevin Pels and
• Veljko Dragojlovic

Beilstein J. Org. Chem. 2009, 5, No. 75, doi:10.3762/bjoc.5.75

• purity. Keywords: bromination; phase-vanishing; PTFE; solvent-free; stilbene; Findings Phase-vanishing (PV) reactions are triphasic reactions, which involve a reagent, a liquid perfluoroalkane and a substrate [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16]. In a test tube, a liquid

• reacted to give a non-volatile product. We chose bromination reactions as a model system for the initial studies of solvent-free PV-PTFE reaction as bromine vapors are visible and the progress of a reaction could be easily monitored (Table 1). In the cource of bromination of cis-stilbene, shown in Figure

• with aqueous thiosulfate) (Figure 2d). Organic reactions on powdered solid substrates are known [22] and bromination of solid trans-stilbene under solvent-free PV-PTFE conditions worked well (Table 1, entry 6). Due to its lower reactivity, bromine vapors were present in the flask throughout the

Ring strain and total syntheses of modified macrocycles of the isoplagiochin type

• Andreas Speicher,
• Timo Backes,
• Kerstin Hesidens and
• Jürgen Kolz

Beilstein J. Org. Chem. 2009, 5, No. 71, doi:10.3762/bjoc.5.71

• benzylic alcohol 20 [28]. Protection as the THP acetal 21 was essential before preparing the boronic acid 22. Previously (see [15]), we reported on a synthesis of 22 starting with the bromination of 3-methoxybenzyl alcohol to 4-bromo-3-methoxybenzyl alcohol. In contrast to the original contribution [29

• ] bromination lead to the formation of 2-bromo-5-methoxybenzyl alcohol, exclusively. Second, the triflate 24 was obtained from vanillin (23) and was further dioxane-protected at the aldehyde function (to 25) and directly transformed into the arylboronate 26 using pinacolborane [30]. Suzuki coupling of the

Diastereoselective functionalisation of benzo-annulated bicyclic sultams: Application for the synthesis of cis-2,4-diarylpyrrolidines

• Susan Kelleher,
• Pierre-Yves Quesne and
• Paul Evans

Beilstein J. Org. Chem. 2009, 5, No. 69, doi:10.3762/bjoc.5.69

• product was 12. Although the yield for this process was low, the isolated product indicated that C11 underwent reduction, presumably prior to N–S bond cleavage. Based on a recent report from Paquette [20], the dibromination of 5a and 5b was subsequently considered. We felt that bromination of the double

• bromination process was carefully studied by a combination of NOE analysis, using the diagnostic 12a-CH2 signal, and X-ray crystallography which helped to substantiate the structures of the minor 1,2-trans-diastereoisomers 14a and 15a (see crystallographic data). Optimum conditions, forming 13a as the major

• this bromination reaction, a bromo-methanolysis reaction was carried out (Entry 5). Interestingly, regio- and diastereoselective formation of the cis-16a was observed in good yield. When 13a was taken up in methanol no conversion into 16a, via an SN1-type process, was observed. The use of THF as

Palladium- catalyzed cross coupling reactions of 4-bromo- 6H-1,2-oxazines

• Reinhold Zimmer,
• Elmar Schmidt,
• Michal Andrä,
• Marcel-Antoine Duhs,
• Igor Linder and
• Hans-Ulrich Reissig

Beilstein J. Org. Chem. 2009, 5, No. 44, doi:10.3762/bjoc.5.44

• .5.44 Abstract A number of 4-aryl- and 4-alkynyl-substituted 6H-1,2-oxazines 8 and 9 have been prepared in good yields via cross coupling reactions of halogenated precursors 2, which in turn are easily accessible by bromination of 6H-1,2-oxazines 1. Lewis-acid promoted reaction of 1,2-oxazine 9c with 1

• with triethylamine (Scheme 1). The 4-bromo-6H-1,2-oxazines were obtained in reasonable to good yields. The bromination of 3-phenyl-substituted 6H-1,2-oxazine 1a often resulted in a mixture of several brominated products which are easily separable by chromatography. Depending on the reaction scale and

• the amount of bromine used (1.5 to 3 equiv) by-products such as 3a, 4 and 5 could be isolated in varying yields. The unexpected formation of 4,5-dibromo-6H-1,2-oxazine 3a can obviously be rationalized by addition of bromine to 2a and elimination of HBr during the bromination reaction of 1a. The

Synthesis and Diels–Alder cycloaddition reaction of norbornadiene and benzonorbornadiene dimers

• Bilal Nişancı,
• Erdin Dalkılıç,
• Murat Güney and
• Arif Daştan

Beilstein J. Org. Chem. 2009, 5, No. 39, doi:10.3762/bjoc.5.39

• One of the starting materials, 2-bromobenzonorbornadiene 4 was synthesized using a procedure described in the literature [15][23] (Scheme 1). Photochemical bromination of benzonorbornadiene 2 with 1,2-dibromotetrachloroethane gave isomeric dibromides 3 in high yield. Dehydrobromination reaction of

Mitomycins syntheses: a recent update

• Jean-Christophe Andrez

Beilstein J. Org. Chem. 2009, 5, No. 33, doi:10.3762/bjoc.5.33

• activity [136]. Starting with the tricyclic ketone 181 [137][138] a low yielding bromination reaction was undertaken followed by an acetate displacement of the resulting α-bromoketone to give 182 (Scheme 50). The amine was introduced by formation of an oxime followed by catalytic hydrogenation in the

Enantiospecific synthesis of [2.2]paracyclophane- 4-thiol and derivatives

• Gareth J. Rowlands and
• Richard J. Seacome

Beilstein J. Org. Chem. 2009, 5, No. 9, doi:10.3762/bjoc.5.9

• success of this strategy was the resolution of the planar chirality of [2.2]paracyclophane by incorporation of the tert-butylsulfinyl moiety to give the diastereoisomers (Sp,RS)-5 and (Rp,RS)-5. Standard iron-catalysed bromination of 1 gave (±)-4-bromo[2.2]paracyclophane 3 in good yield [35][36]. Halogen

Highly brominated anthracenes as precursors for the convenient synthesis of 2,9,10-trisubstituted anthracene derivatives

• Osman Cakmak,
• Leyla Aydogan,
• Kiymet Berkil,
• Ilhami Gulcin and
• Orhan Buyukgungor

Beilstein J. Org. Chem. 2008, 4, No. 50, doi:10.3762/bjoc.4.50

• tribromide 12 was transformed to trimethoxy compound 13 and trinitrile 14 by copper-assisted nucleophilic substitution reactions. Keywords: anthracene derivative; bromination; bromoanthracene; cyanoanthracene; methoxyanthracene; Introduction Anthracene derivatives have been extensively investigated in many

• diode (OLED) were synthesized from the corresponding bromo derivatives by substitution [19][20][21][22][23]. Recently we succeeded in the bromination of anthracene to give hexabromides 3 and 4 which were used in the selective and specific preparation of anthracene oxides and anthracene derivatives

• ]. First, bromination of dibromide 2 was examined at 0 °C in CHCl3 by irradiation with a sun lamp (Table 1, entry 1). The reaction resulted in the formation of three diastereomers: 3, 4, and 5. After chromatography and fractional crystallization, hexabromides 3, 4, and 5 were isolated in yields of 73%, 8

Synthesis of 2,3,6,7-tetrabromoanthracene

• Christian Schäfer,
• Friederike Herrmann and
• Jochen Mattay

Beilstein J. Org. Chem. 2008, 4, No. 41, doi:10.3762/bjoc.4.41

• involving brominated anthracenes [7][8][9][10][11][12], mainly using anthraquinones for the bromination at an outer position, but a synthesis of 2,3,6,7-tetrabromoanthracene is missing. In this paper, we report a convenient four step synthesis of 2,3,6,7-tetrabromoanthracene via a twofold Bergman

Phase- vanishing halolactonization of neat substrates

• Nicole Windmon and
• Veljko Dragojlovic

Beilstein J. Org. Chem. 2008, 4, No. 29, doi:10.3762/bjoc.4.29

• done in a capped 20 mL vial. In the case of bromination of 4-pentenoic acid (1), under phase-vanishing conditions there was competing formation of 4,5-dibromopentenoic acid (3). Formation of the dibromo derivative as a minor product in the course of bromolactonization of 4-pentenoic acid has been