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Search for "regioisomers" in Full Text gives 240 result(s) in Beilstein Journal of Organic Chemistry. Showing first 200.

Synthetic and semi-synthetic approaches to unprotected N-glycan oxazolines

  • Antony J. Fairbanks

Beilstein J. Org. Chem. 2018, 14, 416–429, doi:10.3762/bjoc.14.30

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  • partially purified by acetone precipitation and extraction with 60% methanol. The crude N-glycans were found to be a rather complex mixture of compounds, the four major components of which were identified as triantennary glycans with 2 or 3 sialic acids attached as regioisomers (i.e., both α(2–6)- and α(2–3
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Published 15 Feb 2018

5-Aminopyrazole as precursor in design and synthesis of fused pyrazoloazines

  • Ranjana Aggarwal and
  • Suresh Kumar

Beilstein J. Org. Chem. 2018, 14, 203–242, doi:10.3762/bjoc.14.15

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  • acetic acid (Scheme 1). In the same report the other regioisomers 6-trifluoromethylpyrazolo[3,4-b]pyridines 20 were obtained under multicomponent solvent-free conditions by the reaction of hydrazine 14, β-ketonitrile 15 and β-diketone 17 as an exclusive product. The structures of both the regioisomers
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Published 25 Jan 2018

Progress in copper-catalyzed trifluoromethylation

  • Guan-bao Li,
  • Chao Zhang,
  • Chun Song and
  • Yu-dao Ma

Beilstein J. Org. Chem. 2018, 14, 155–181, doi:10.3762/bjoc.14.11

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  • substituents and generate mixture of regioisomers in some cases. In 2012, the group of Qing [56] designed a copper-catalyzed oxidative trifluoromethylation of heteroarenes and electron-deficient arenes with TMSCF3 through direct C−H activation (Scheme 35). At first, the oxidative trifluoromethylation of 1,3,4
  • . These methods have often the drawback of generating mixtures of regioisomers. Future efforts will be focus on developing efficient and less expensive reagents, along with a better understanding of mechanisms, improving the regioselectivity and enantioselectivity in these trifluoromethylation processes
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Published 17 Jan 2018

Aminosugar-based immunomodulator lipid A: synthetic approaches

  • Alla Zamyatina

Beilstein J. Org. Chem. 2018, 14, 25–53, doi:10.3762/bjoc.14.3

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Published 04 Jan 2018

Recent applications of click chemistry for the functionalization of gold nanoparticles and their conversion to glyco-gold nanoparticles

  • Vivek Poonthiyil,
  • Thisbe K. Lindhorst,
  • Vladimir B. Golovko and
  • Antony J. Fairbanks

Beilstein J. Org. Chem. 2018, 14, 11–24, doi:10.3762/bjoc.14.2

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  • , and gives a mixture of 1,4- and 1,5-triazole regioisomers (Scheme 1) [39]. Interest in and applications of the AAC have surged over the past 15 or so years, since the introduction of Cu(I) catalysis, which led to significant improvements in both the regioselectivity and rates of the reaction [40][41
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Published 03 Jan 2018

Acid-catalyzed ring-opening reactions of a cyclopropanated 3-aza-2-oxabicyclo[2.2.1]hept-5-ene with alcohols

  • Katrina Tait,
  • Alysia Horvath,
  • Nicolas Blanchard and
  • William Tam

Beilstein J. Org. Chem. 2017, 13, 2888–2894, doi:10.3762/bjoc.13.281

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  • includes the reduction to form alkane 8 [3], oxidative cleavage of the C=C bond to form 9 [4], ring-opening metathesis to form functionalized alkenes 10 and 11 [4], dihydroxylation to form diol 12 [5], ruthenium-catalyzed [2 + 2] cycloaddition with unsymmetrical alkynes to form regioisomers 13 and 14 [6
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Published 27 Dec 2017

CF3SO2X (X = Na, Cl) as reagents for trifluoromethylation, trifluoromethylsulfenyl-, -sulfinyl- and -sulfonylation and chlorination. Part 2: Use of CF3SO2Cl

  • Hélène Chachignon,
  • Hélène Guyon and
  • Dominique Cahard

Beilstein J. Org. Chem. 2017, 13, 2800–2818, doi:10.3762/bjoc.13.273

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  • additional desulfonylation step (Scheme 6) [13]. Both electron-withdrawing and electron-donating groups on para-position of the aryl ring were tolerated, and provided comparable yields. On the other hand, the presence of a substituent in meta-position led to the formation of two regioisomers. As for ortho
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Published 19 Dec 2017

CF3SO2X (X = Na, Cl) as reagents for trifluoromethylation, trifluoromethylsulfenyl-, -sulfinyl- and -sulfonylation. Part 1: Use of CF3SO2Na

  • Hélène Guyon,
  • Hélène Chachignon and
  • Dominique Cahard

Beilstein J. Org. Chem. 2017, 13, 2764–2799, doi:10.3762/bjoc.13.272

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  • failed to give the expected product. With a substituent at the meta-position of the aniline ring, a mixture of regioisomers was obtained. Various alkenes with substituents (R3) were investigated and the oxindoles were obtained in moderate to high yields (Scheme 24). Simultaneously, Lei and co-workers
  • -substituted phenyl rings produced mixtures of regioisomers. Under these metal-free conditions, it was proposed that the CF3 radical was formed uniquely by reaction of CF3SO2Na with K2S2O8. N-Arylacrylamides could also react with CF3SO2Na under metal-free conditions by replacing tert-butyl hydroperoxide or the
  • arenes and heteroarenes: In 1991, Langlois and co-workers reported the first trifluoromethylation of aromatic compounds with sodium trifluoromethanesulfinate under oxidative conditions (Scheme 34) [16]. The scope was quite narrow with electron-rich aromatics and mixtures of regioisomers were often
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Published 19 Dec 2017

An efficient synthesis of 1,6-anhydro-N-acetylmuramic acid from N-acetylglucosamine

  • Matthew B. Calvert,
  • Christoph Mayer and
  • Alexander Titz

Beilstein J. Org. Chem. 2017, 13, 2631–2636, doi:10.3762/bjoc.13.261

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  • regioisomers, out of which the desired anhydroMurNAc derivative 1 could only be isolated in trace quantities from the mixture with isomers 5–11 (Scheme 2). A selective protection of the 4-OH position of 4 has been reported, and as such this tritylation was carried out, delivering 12 in 74% yield [12]. The
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Published 11 Dec 2017

Electrophilic trifluoromethylselenolation of terminal alkynes with Se-(trifluoromethyl) 4-methylbenzenesulfonoselenoate

  • Clément Ghiazza,
  • Anis Tlili and
  • Thierry Billard

Beilstein J. Org. Chem. 2017, 13, 2626–2630, doi:10.3762/bjoc.13.260

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  • . Further, a high regioselectivity is observed but, surprisingly, the anti-Markovnikov regioisomers were obtained. The stereochemistry and regiochemistry were confirmed thanks to the X-ray structure of compound 3a (Figure 1). From a mechanistic point of view, the reaction starts certainly with the
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Published 07 Dec 2017

Regioselective decarboxylative addition of malonic acid and its mono(thio)esters to 4-trifluoromethylpyrimidin-2(1H)-ones

  • Sergii V. Melnykov,
  • Andrii S. Pataman,
  • Yurii V. Dmytriv,
  • Svitlana V. Shishkina,
  • Mykhailo V. Vovk and
  • Volodymyr A. Sukach

Beilstein J. Org. Chem. 2017, 13, 2617–2625, doi:10.3762/bjoc.13.259

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  • Michael-type regioisomer 5a (Table 1, entry 1). The reaction course and the ratio of the regioisomers formed were conveniently monitored by 19F NMR spectroscopy. Acid 4a precipitated in pure form on evaporating toluene and treating the residue with diluted hydrochloric acid. Performing the reaction in a
  • it under optimal conditions using toluene or DMSO as solvent and TEA (1 equiv) as catalyst (Table 2). The alkyl substituent at the nitrogen atom of the substrate had no significant effect on the reaction course. In all cases, both regioisomers, 4b–i and 5b–i, were isolated in modest to high yields
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Published 07 Dec 2017

15N-Labelling and structure determination of adamantylated azolo-azines in solution

  • Sergey L. Deev,
  • Alexander S. Paramonov,
  • Tatyana S. Shestakova,
  • Igor A. Khalymbadzha,
  • Oleg N. Chupakhin,
  • Julia O. Subbotina,
  • Oleg S. Eltsov,
  • Pavel A. Slepukhin,
  • Vladimir L. Rusinov,
  • Alexander S. Arseniev and
  • Zakhar O. Shenkarev

Beilstein J. Org. Chem. 2017, 13, 2535–2548, doi:10.3762/bjoc.13.250

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  • spectroscopy. For monocyclic derivatives of azoles, the structures of N-alkylated regioisomers can be determined using 2D H-(C)-N multiple bond correlation (HCNMBC) experiments [22][23] using natural isotopic abundance. These experiments rely on the magnetization transfer through 13C-15N J-coupling constants
  • ]pyrimidin-7-one and the N-adamantylation of the obtained compounds. The combined analysis of the JCN and JHN couplings permitted the straightforward determination of the adamantylation sites in these azolo-azines, even when a mixture of regioisomers is formed. Results Synthesis. Derivatives of 1,2,4
  • adamantyl cation generated from 1-adamantanol in acidic medium [34][35][36][37]. The adamantylation of 13-15N2 led to N2- and N1-regioisomers (15a-15N2 and 15b-15N2, respectively, Scheme 1). Interestingly, according to the possible resonance structures, compound 15a-15N2 should represent a mesoionic
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Published 29 Nov 2017

Synthesis and supramolecular properties of regioisomers of mononaphthylallyl derivatives of γ-cyclodextrin

  • Markéta Bláhová,
  • Sergey K. Filippov,
  • Lubomír Kováčik,
  • Jiří Horský,
  • Simona Hybelbauerová,
  • Zdenka Syrová,
  • Tomáš Křížek and
  • Jindřich Jindřich

Beilstein J. Org. Chem. 2017, 13, 2509–2520, doi:10.3762/bjoc.13.248

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  • a cross-metathesis between previously described regioisomers of mono-O-allyl derivatives of γ-CD and 2-vinylnaphthalene which gives yields of about 16–25% (2–5% starting from γ-CD). To increase the overall yields, we have developed another method, based on a direct alkylation of γ-CD with 3
  • supramolecular polymers [9] multifunctional molecules are assembled in a regular manner. To avoid branching, monosubstituted CDs are required for a linear supramolecular polymer of CDs with guest groups attached. Monosubstituted derivatives of CDs [10] include three regioisomers, namely 2I-O-, 3I-O-, and 6I-O
  • -substituted ones. To separate pure regioisomers from their mixture is tricky. Their direct regioselective synthesis is possible, although not easy, because hydroxy groups at different positions of CD have different properties; the hydroxy group at position 6 is the most nucleophilic and basic one, the hydroxy
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Published 27 Nov 2017

Fluorination of some highly functionalized cycloalkanes: chemoselectivity and substrate dependence

  • Attila Márió Remete,
  • Melinda Nonn,
  • Santos Fustero,
  • Matti Haukka,
  • Ferenc Fülöp and
  • Loránd Kiss

Beilstein J. Org. Chem. 2017, 13, 2364–2371, doi:10.3762/bjoc.13.233

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  • -amino ester stereo- and regioisomers, derived from unsaturated cyclic β-amino acids is described. The nucleophilic fluorinations involving hydroxy–fluorine exchange of some highly functionalized alicyclic diol derivatives have been carried out in view of selective fluorination, investigating substrate
  • , cispentacin) are relevant antifungal agents [19]. Therefore we have selected some five and six-membered alicyclic dihydroxylated β-amino ester stereo- and regioisomers as model compounds [23][24][25][26], derived from cyclopentene or cyclohexene β-amino acids. These were used in order to evaluate their
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Published 06 Nov 2017

Solvent-free copper-catalyzed click chemistry for the synthesis of N-heterocyclic hybrids based on quinoline and 1,2,3-triazole

  • Martina Tireli,
  • Silvija Maračić,
  • Stipe Lukin,
  • Marina Juribašić Kulcsár,
  • Dijana Žilić,
  • Mario Cetina,
  • Ivan Halasz,
  • Silvana Raić-Malić and
  • Krunoslav Užarević

Beilstein J. Org. Chem. 2017, 13, 2352–2363, doi:10.3762/bjoc.13.232

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  • it increases reaction rates and yields and directs the azide–alkyne cycloaddition exclusively towards 1,4-substituted regioisomers, whereas the non-catalyzed process results in a non-stoichiometric mixture of 1,4- and 1,5-regioisomers. Even though CuAAC reactions are efficiently performed in solution
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Published 06 Nov 2017

Homologated amino acids with three vicinal fluorines positioned along the backbone: development of a stereoselective synthesis

  • Raju Cheerlavancha,
  • Ahmed Ahmed,
  • Yun Cheuk Leung,
  • Aggie Lawer,
  • Qing-Quan Liu,
  • Marina Cagnes,
  • Hee-Chan Jang,
  • Xiang-Guo Hu and
  • Luke Hunter

Beilstein J. Org. Chem. 2017, 13, 2316–2325, doi:10.3762/bjoc.13.228

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  • it was found that the inclusion of the additive TMS-morpholine [36][37] was also required to ensure a high diastereoisomeric excess of 38a. The epoxide 38a was then ring-opened using Et3N·3HF to deliver the difluorodiol 39a as a mixture of regioisomers. This mixture subsequently converged during the
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Published 01 Nov 2017

Curcuminoid–BF2 complexes: Synthesis, fluorescence and optimization of BF2 group cleavage

  • Henning Weiss,
  • Jeannine Reichel,
  • Helmar Görls,
  • Kilian Rolf Anton Schneider,
  • Mathias Micheel,
  • Michael Pröhl,
  • Michael Gottschaldt,
  • Benjamin Dietzek and
  • Wolfgang Weigand

Beilstein J. Org. Chem. 2017, 13, 2264–2272, doi:10.3762/bjoc.13.223

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  • increasing electron density of the aromatic system, the emission intensity in the low-energy regime of the spectrum increases. It is also noteworthy, that regarding 2a and 2f, which are regioisomers, the second fluorescence band is more intense for 2f than for 2a. For the complexes containing a brominated
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Published 26 Oct 2017

Conjugated nitrosoalkenes as Michael acceptors in carbon–carbon bond forming reactions: a review and perspective

  • Yaroslav D. Boyko,
  • Valentin S. Dorokhov,
  • Alexey Yu. Sukhorukov and
  • Sema L. Ioffe

Beilstein J. Org. Chem. 2017, 13, 2214–2234, doi:10.3762/bjoc.13.220

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  • demonstrated that the reaction of highly electron-rich aromatics with nitrosoalkenes NSA14 affords the corresponding α-aryl-substituted oximes 66 in low to moderate yields as mixtures of regioisomers [44] (Scheme 22). Nitrosoalkenes were generated from the corresponding α-halooximes 65 upon treatment with
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Published 23 Oct 2017

Synthesis of benzannelated sultams by intramolecular Pd-catalyzed arylation of tertiary sulfonamides

  • Valentin A. Rassadin,
  • Mirko Scholz,
  • Anastasiia A. Klochkova,
  • Armin de Meijere and
  • Victor V. Sokolov

Beilstein J. Org. Chem. 2017, 13, 1932–1939, doi:10.3762/bjoc.13.187

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  • latter transformation was a rhodium octanoate-catalyzed intramolecular carbenoid insertion into an ortho CAr–H bond (Scheme 1) [21][22], which proceeded with good yields in most cases. However, with non-equivalent aryl ortho-positions in the starting diazo compounds, mixtures of regioisomers – virtually
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Published 12 Sep 2017

Accessing simply-substituted 4-hydroxytetrahydroisoquinolines via Pomeranz–Fritsch–Bobbitt reaction with non-activated and moderately-activated systems

  • Marco Mottinelli,
  • Mathew P. Leese and
  • Barry V. L. Potter

Beilstein J. Org. Chem. 2017, 13, 1871–1878, doi:10.3762/bjoc.13.182

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  • - and the ortho-position to the substituent, as expected, the para-position predominated and the 7-substituted THIQs (e.g., 10e–g, Scheme 4) were obtained as the major product. Nevertheless, it was possible to isolate a usable amount of the 5-substituted THIQ 14e. The ratio of the two regioisomers
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Published 06 Sep 2017

1-Imidoalkylphosphonium salts with modulated Cα–P+ bond strength: synthesis and application as new active α-imidoalkylating agents

  • Jakub Adamek,
  • Roman Mazurkiewicz,
  • Anna Węgrzyk and
  • Karol Erfurt

Beilstein J. Org. Chem. 2017, 13, 1446–1455, doi:10.3762/bjoc.13.142

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  •  3). The imidoalkylation of anisole and toluene gave the expected products as mixtures of ortho and para isomers in molar ratios ranging from 1.4:1.0 to 1.0:4.0 (Table 3). It seems that the steric congestion is the main factor governing the molar ratio of the regioisomers. Thus an excess of ortho
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Published 24 Jul 2017

Switchable highly regioselective synthesis of 3,4-dihydroquinoxalin-2(1H)ones from o-phenylenediamines and aroylpyruvates

  • Juraj Dobiaš,
  • Marek Ondruš,
  • Gabriela Addová and
  • Andrej Boháč

Beilstein J. Org. Chem. 2017, 13, 1350–1360, doi:10.3762/bjoc.13.132

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  • acid) which we studied. Six regioisomeric 3,4-dihydroquinoxalin-2(1H)-one pairs were selectively prepared and characterised. Based on our experiences, a simplified methodology for determining the structure of the regioisomers was proposed. We developed two general and highly selective methodologies
  • when choosing the most optimal reaction conditions for the synthesis of the desired 3,4-dihydroquinoxalin-2(1H)-one regioisomers with the best selectivity. The demonstrated methodologies in this article may also be applied to differently substituted 3,4-dihydroquinoxalin-2(1H)-ones in general, which
  • monosubstituted o-phenylenediamines 11. In this case the amino groups usually have different reactivity and thus produce a mixture of regioisomeric products. If both regioisomers are needed, one can separate them [21]. Separation can be difficult to such an extent that some of the Cu(II) chelators were
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Published 10 Jul 2017

Synthesis of novel 13α-estrone derivatives by Sonogashira coupling as potential 17β-HSD1 inhibitors

  • Ildikó Bacsa,
  • Rebeka Jójárt,
  • János Wölfling,
  • Gyula Schneider,
  • Bianka Edina Herman,
  • Mihály Szécsi and
  • Erzsébet Mernyák

Beilstein J. Org. Chem. 2017, 13, 1303–1309, doi:10.3762/bjoc.13.126

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  • 10.3762/bjoc.13.126 Abstract Novel 13α-estrone derivatives were synthesized by Sonogashira coupling. Transformations of 2- or 4-iodo regioisomers of 13α-estrone and its 3-methyl ether were carried out under different conditions in a microwave reactor. The 2-iodo isomers were reacted with para-substituted
  • compounds. All the halogenated 3-hydroxy and the 4-substituted regioisomers of 3-methyl ethers displayed substantial inhibitory activity against the 17β-hydroxysteroid dehydrogenase type 1 enzyme (17β-HSD1). Certain derivatives displayed a similar or more pronounced effect than those of their parent
  • -catalyzed C–C coupling reactions. Some Sonogashira couplings on estrane, but not on the 13α-estrane core have been performed at C-2, -3, -11, -16 and -17. To the best of our knowledge, 4-coupled regioisomers have not been synthesized to date [19]. Couplings of steroidal alkynes with small molecular halides
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Published 30 Jun 2017

Regioselective (thio)carbamoylation of 2,7-di-tert-butylpyrene at the 1-position with iso(thio)cyanates

  • Anna Wrona-Piotrowicz,
  • Marzena Witalewska,
  • Janusz Zakrzewski and
  • Anna Makal

Beilstein J. Org. Chem. 2017, 13, 1032–1038, doi:10.3762/bjoc.13.102

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  • min, 1,8-bis-carbothioamide 4, containing ≈20% of other regioisomers (9%) and nitrile 5 (7%) were isolated by column chromatography besides the expected 3o (78%). The amounts of 4 and 5 significantly increased along with the reaction time (Table 1). The highest yield of 4 (33%) was found after 6 h
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Published 29 May 2017

Metal-free hydroarylation of the side chain carbon–carbon double bond of 5-(2-arylethenyl)-3-aryl-1,2,4-oxadiazoles in triflic acid

  • Anna S. Zalivatskaya,
  • Dmitry S. Ryabukhin,
  • Marina V. Tarasenko,
  • Alexander Yu. Ivanov,
  • Irina A. Boyarskaya,
  • Elena V. Grinenko,
  • Ludmila V. Osetrova,
  • Eugeniy R. Kofanov and
  • Aleksander V. Vasilyev

Beilstein J. Org. Chem. 2017, 13, 883–894, doi:10.3762/bjoc.13.89

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  • , entry 7), chlorobenzene (2b + 2c, Table 2, entry 6 and 2q + 2r, entry 21), and toluene (2u + 2v, Table 2, entry 24). The exact structures of these regioisomers were determined on the basis of multiplet signals of the aromatic protons in the 1H NMR spectra. The observation of regioisomeric products
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Published 11 May 2017
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