Efficient routes toward the synthesis of the D-rhamno-trisaccharide related to the A-band polysaccharide of Pseudomonas aeruginosa

• Aritra Chaudhury,
• Sajal K. Maity and
• Rina Ghosh

Beilstein J. Org. Chem. 2014, 10, 1488–1494, doi:10.3762/bjoc.10.153

• synthesis of monomeric D-rhamnose has been highly streamlined by Roy et al. in 2007 [26], and further improvement on this method was reported by Kiefel et al. in 2011 [27]. However, the deoxygenation protocol involving halogenation under Mitsunobu conditions was found to be inefficient when applied to

Rasta resin–triphenylphosphine oxides and their use as recyclable heterogeneous reagent precursors in halogenation reactions

• Xuanshu Xia and
• Patrick H. Toy

Beilstein J. Org. Chem. 2014, 10, 1397–1405, doi:10.3762/bjoc.10.143

• reagent precursors in a wide range of halogenation reactions. The rasta resin–triphenylphosphine oxides were reacted with either oxalyl chloride or oxalyl bromide to form the corresponding halophosphonium salts, and these in turn were reacted with alcohols, aldehydes, aziridines and epoxides to form

• halogenated products in high yields after simple purification. The polymer-supported triphenylphosphine oxides formed as a byproduct during these reactions could be recovered and reused numerous times with no appreciable decrease in reactivity. Keywords: Appel reaction; halogenation; organophosphorus

• reactions, such as those illustrated in Scheme 2: (1) the conversion of alcohols 4 to alkyl halides 5 (the Appel reaction), (2) the conversion of aldehydes 6 to 1,1-dihaloalkanes 7, (3) halogenation of aziridines 8 to form 2-haloamines 9, (4) halogenation of epoxides 10 to form 1,2-dihaloalkanes 11, (5) and

Stereoselective synthesis of carbocyclic analogues of the nucleoside Q precursor (PreQ₀)

• Sabin Llona-Minguez and
• Simon P. Mackay

Beilstein J. Org. Chem. 2014, 10, 1333–1338, doi:10.3762/bjoc.10.135

• ] (Figure 3). The resulting pivalamide 8 proved to be more soluble than 1 and the subsequent halogenation step was accomplished in the presence of a phase transfer catalyst, affording the desired chloro-intermediate 9 in fair yield. In our hands, nucleophilic aromatic substitution on 9 using amines of

Visible-light photoredox catalysis enabled bromination of phenols and alkenes

• Yating Zhao,
• Zhe Li,
• Chao Yang,
• Run Lin and
• Wujiong Xia

Beilstein J. Org. Chem. 2014, 10, 622–627, doi:10.3762/bjoc.10.53

• phenols. The typical approaches include direct electrophilic halogenation by using molecular bromine or N-bromosuccinimide (NBS) [6][7][8], organometallic catalyst-promoted bromination [9][10][11][12], and the oxidative bromination of phenols [13][14][15]. Nevertheless, most of the methods suffer from

An overview of the synthetic routes to the best selling drugs containing 6-membered heterocycles

• Marcus Baumann and
• Ian R. Baxendale

Beilstein J. Org. Chem. 2013, 9, 2265–2319, doi:10.3762/bjoc.9.265

α-Bromodiazoacetamides – a new class of diazo compounds for catalyst-free, ambient temperature intramolecular C–H insertion reactions

• Åsmund Kaupang and
• Tore Bonge-Hansen

Beilstein J. Org. Chem. 2013, 9, 1407–1413, doi:10.3762/bjoc.9.157

• cyclic amide side chains. Keywords: α-halo-β-lactam; diazo; halocarbonylcarbene; halogenation; thermolysis; Introduction Diazocarbonyl compounds are popular precursors for carbonylcarbenes and -carbenoids, the synthetic utility of which is thoroughly established through their successful employment in

• et al. reported the syntheses of an α-halodiazomethyl phosphonic acid dimethyl ester and an α-halodiazomethyl diphenyl phosphoxide, starting from the silver salts of the respective diazo compounds [10]. More recently, two novel protocols for the halogenation of diazoesters and -phosphonates have been

• the halogenation of diazoacetamides. We report herein the bromination of the diazoacetamides derived from a selection of cyclic secondary amines, using DBU and N-bromophthalimide (NBP), as well as an investigation of the ability of the carbenes/carbenoids derived from the resulting α

A new synthetic protocol for coumarin amino acid

• Xinyi Xu,
• Xiaosong Hu and
• Jiangyun Wang

Beilstein J. Org. Chem. 2013, 9, 254–259, doi:10.3762/bjoc.9.30

• , by using the Henderson–Hasselbalch equation. The halogenation of 1a at the 6-position decreases the pKa value, which makes compounds 1b and 1c good substitutes for 1a in fluorescent labeling and other investigations in biological systems. Screening for the synthetase/tRNA pair for 1b and 1c is under

Polar reactions of acyclic conjugated bisallenes

• Reiner Stamm and
• Henning Hopf

Beilstein J. Org. Chem. 2013, 9, 36–48, doi:10.3762/bjoc.9.5

• and epoxides, hydrohalogenation (HCl, HBr addition), halogenation (Br2 and I2 addition), and [2 + 2] cycloaddition with chlorosulfonyl isocyanate. The resulting adducts were fully characterized by spectroscopic and analytical methods; they constitute interesting substrates for further organic

• . Hydrohalogenation and halogenation of acyclic conjugated bisallenes Hydrohalogenation of 2 and 5 The addition of protic acids HX (with X usually being Cl and Br) to allenes has been studied quite carefully. The process usually takes place according to the Markovnikoff rule and often cannot be stopped at the

• postulate a butadienylallene intermediate, 51, again. Halogenation of 2, 3 and 11 Among the addition of halogens the addition of bromine and iodine to various allenes has been particularly well studied [28]. Whereas bromine is added to the more highly substituted double bond of simple monoallenes, iodine

Flow photochemistry: Old light through new windows

• Jonathan P. Knowles,
• Luke D. Elliott and
• Kevin I. Booker-Milburn

Beilstein J. Org. Chem. 2012, 8, 2025–2052, doi:10.3762/bjoc.8.229

• (UVC) and are particularly suited to carbonyl and arene photochemistry as well as halogenation chemistry. These lamps are also available with a range of phosphor coatings to emit both UVB and UVA radiation. They have found commercial use in medical, tanning and insect-attraction applications. These

Palladium-catalyzed dual C–H or N–H functionalization of unfunctionalized indole derivatives with alkenes and arenes

• Gianluigi Broggini,
• Egle M. Beccalli,
• Andrea Fasana and
• Silvia Gazzola

Beilstein J. Org. Chem. 2012, 8, 1730–1746, doi:10.3762/bjoc.8.198

• same couple PdCl2(MeCN)2/CuX2 as catalyst and oxidant, respectively. 2-Indolylallylcarboxamides 48 have been found to be suitable substrates to access variously substituted β-carbolinones 49 and 50 through alkenylation/halogenation or alkenylation/esterification processes selectively obtained by

• acetonitrile as the solvent, allowed the formation of the dihalogenated pyrazino[1,2-a]indole derivatives 52 by an unusual aminohalogenation/halogenation sequence (Scheme 30). The formation of the 3-haloderivatives XXI, ascribable solely to the action of the Cu(II) salt [84], and the cyclization of the π

• /carboxylation reaction. Plausible catalytic cycle for the cyclization/carboxylation of alkenylindoles, adapted from Liu et al. [81]. Intramolecular domino reactions of indolylallylamides through alkenylation/halogenation or alkenylation/esterification processes. Proposed mechanism for the alkenylation

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

• arylcyclopropane carboxylic acids from the corresponding cinnamic acids, followed by halogenation. Conversion of arylcyclopropane carboxylic acids 10a,b to the amines 4 and 5, and chemical resolution of 4 into its enantiomers. Chemical resolution of arylcyclopropane carboxylic acid 9 followed by bromination

Highly selective synthesis of (E)-alkenyl-(pentafluorosulfanyl)benzenes through Horner–Wadsworth–Emmons reaction

• George Iakobson and
• Petr Beier

Beilstein J. Org. Chem. 2012, 8, 1185–1190, doi:10.3762/bjoc.8.131

• nitrogen [18] nucleophiles, and the oxidative nucleophilic substitution with Grignard and alkyllithium reagents [19]. Reduction of the nitro group in 1 or 2 to (pentafluorosulfanyl)anilines followed by acylation, SEAr halogenation or diazotization (with follow-up reactions) has also been described [11][20

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

• 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

• or HCl gas. Thus, our new protocol offers a safer operational choice and reduced environmental impact when compared to direct chlorination in aqueous HCl, or halogenation of protected/masked anilines, which requires additional deprotection processes. Chlorination (or bromination) of unprotected

Aryl nitrile oxide cycloaddition reactions in the presence of pinacol boronic acid ester

• Sarah L. Harding,
• Sebastian M. Marcuccio and
• G. Paul Savage

Beilstein J. Org. Chem. 2012, 8, 606–612, doi:10.3762/bjoc.8.67

• halogenation–dehydrohalogenation process is most common, several methods involving direct oxidative dehydrogenation of aldoximes have been reported, including the use of lead tetraacetate [22][23], mercury(II) acetate [24], hypervalent iodine [25][26], and manganese(IV) oxide [27]. We were interested in

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

• compound is the key intermediate for all further transformations, we decided to check whether the use of bromine-substituted aromatic methylsulfone 4' would prove to offer higher yields in the halogenation/nitration sequence. Bromination of 4' with BrCl afforded tribromomethyl sulfone 1' in 90% yield

• of the obtained compounds exhibit fungicidal activity. Retrosynthetic analysis of the designed target molecules. Synthetic routes for 4-chlorophenyl tribromomethyl sulfone (1). Halogenation/nitration sequence for 4-halogenphenyl methyl sulfones 4 and 4'. SNAr transformations of sulfone 6. Preparation

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

• shown to introduce β-branching carboxyl units into a number of polyketide chains. Feeding studies for jamaicamides revealed the incorporation of an acetate unit at the corresponding position followed by dehydratisation, decarboxylation and halogenation [41]. Further interesting features of jamaicamide

• halogenation domain, although this could not be expected from the structure of curacin A. In vitro studies revealed that indeed cyclopropyl ring formation is preceded by a halogenation step (Figure 6B) [42]. The Cur ECH2 was found to catalyze the formation of a α,β-enoyl thioester, which is in contrast to the

Recent advances in direct C–H arylation: Methodology, selectivity and mechanism in oxazole series

• Cécile Verrier,
• Pierrik Lassalas,
• Laure Théveau,
• Guy Quéguiner,
• François Trécourt,
• Francis Marsais and
• Christophe Hoarau

Beilstein J. Org. Chem. 2011, 7, 1584–1601, doi:10.3762/bjoc.7.187

• regioselective functionalization. Ortho-lithiation by means of alkyllithium and lithium amides bases has been extensively developed as lithiated species display a high reactivity towards many electrophiles, leading to various substitutions (e.g., halogenation, carboxylation, acylation, hydroxymethylation

Development of the titanium–TADDOLate-catalyzed asymmetric fluorination of β-ketoesters

• Lukas Hintermann,
• Mauro Perseghini and
• Antonio Togni

Beilstein J. Org. Chem. 2011, 7, 1421–1435, doi:10.3762/bjoc.7.166

• substrate range of the catalytic fluorination and its extension to other activated carbonyl compounds [57]. Results and Discussion Lewis acid catalyzed halogenation of activated carbonyl compounds Overview Nonfunctionalized ketones are halogenated in the α-position by halogens and other electrophilic

• equilibirum mixture is halogenated quickly, leaving behind the keto tautomer [63]. Further halogenation is then limited by the rate of enolization. This effect forms the basis of Meyer’s famous enol-titration experiments for determining the degree of enolization in activated carbonyl compounds (Scheme 2a) [63

• should also result in catalysis of the overall electrophilic halogenation. As a working hypothesis, it was assumed that coordination of β-ketocarbonyl compounds to Lewis acidic metal centers should facilitate their transformation to a covalently coordinated enolate, which may be fluorinated at carbon

One-pot four-component synthesis of pyrimidyl and pyrazolyl substituted azulenes by glyoxylation–decarbonylative alkynylation–cyclocondensation sequences

• Charlotte F. Gers,
• Julia Rosellen,
• Eugen Merkul and
• Thomas J. J. Müller

Beilstein J. Org. Chem. 2011, 7, 1173–1181, doi:10.3762/bjoc.7.136

• , azulenes must be functionalized, either by halogenation or borylation, and some of these derivatives were found to be quite unstable [45][46]. To the best of our knowledge, no diversity-oriented multicomponent syntheses of azulenyl heterocycles have been reported so far. Here, we report the development of

Aromatic and heterocyclic perfluoroalkyl sulfides. Methods of preparation

• Vladimir N. Boiko

Beilstein J. Org. Chem. 2010, 6, 880–921, doi:10.3762/bjoc.6.88

• . The halogenation of SAlk-derivatives with subsequent replacement of the halogen atoms by fluorine. The introduction of SRF-moieties into aromatic compounds by both electrophilic and nucleophilic reagents. Various modes of perfluoroalkylation of organosulfur compounds including cationic, anionic

• groups. The reactions are more problematic however, for electron deficient substrates where competing halogenation, reduction and isomerization products often result from perfluoroalkylthiolation reactions. 3.2. Nucleophilic introduction of SRF groups Anionic salts of type RFS− M+ and their heavy metal

Recent advances in carbocupration of α-heterosubstituted alkynes

• Ahmad Basheer and
• Ilan Marek

Beilstein J. Org. Chem. 2010, 6, No. 77, doi:10.3762/bjoc.6.77

• adducts (Scheme 22). Hydrolysis, alkylation, acylation, halogenation and stannylation proceed stereoselectively to afford synthetically useful intermediates [56][57]. Under similar conditions, 1-substituted alkynylsilanes do not undergo the carbometalation reaction. Only when 1-substituted-2

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

• -hexyne provided alkynyl-substituted pyridine derivative 12 thus demonstrating the potential of this approach for the synthesis of pyridines. Keywords: alkyne; halogenation; 1,2-oxazines; palladium catalysis; pyridines; Introduction A broad range of synthetic applications demonstrates that 1,2-oxazine

• , we describe our results dealing with the halogenation of 6H-1,2-oxazines 1 and the use of the resulting products as precursors in palladium-catalyzed cross coupling reactions. Results and Discussion Not much is known about halogenated 6H-1,2-oxazines and only a few mostly inefficient procedures are

The use of silicon- based tethers for the Pauson- Khand reaction

• Adrian P. Dobbs,
• Ian J. Miller and
• Saša Martinović

Beilstein J. Org. Chem. 2007, 3, No. 21, doi:10.1186/1860-5397-3-21

• order to achieve this it was thought to form each of the 'arms' of the acetal in separate synthetic steps (Scheme 15). The first stage of the reaction was silyl ether formation. The alkyne 'arm' of the acetal was introduced first, as it was feared that during the next, halogenation step, halogenation of