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Search for "Brønsted acid" in Full Text gives 153 result(s) in Beilstein Journal of Organic Chemistry.

Aqueous olefin metathesis: recent developments and applications

  • Valerio Sabatino and
  • Thomas R. Ward

Beilstein J. Org. Chem. 2019, 15, 445–468, doi:10.3762/bjoc.15.39

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  • , the presence of a Brønsted acid led to the protonation of one phosphine ligand rather than reacting with the ruthenium alkylidene moiety. Scavenging of the trialkylphosphine moiety resulted in a more active complex capable of initiating the ROMP of 2,3-difunctionalized norbornadienes and 7-oxo
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Published 14 Feb 2019

A tutorial review of stereoretentive olefin metathesis based on ruthenium dithiolate catalysts

  • Daniel S. Müller,
  • Olivier Baslé and
  • Marc Mauduit

Beilstein J. Org. Chem. 2018, 14, 2999–3010, doi:10.3762/bjoc.14.279

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  • styrene 32 the protonation and loss of the catechothiolate ligand by Brønsted acid 34 is a faster process leading to catalyst degradation. It should be noted that stereoretentive CM and RCM with (E)-2-butene (E-25) as capping reagent were also reported, however, these reactions required a significantly
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Published 07 Dec 2018

MoO3 on zeolites MCM-22, MCM-56 and 2D-MFI as catalysts for 1-octene metathesis

  • Hynek Balcar,
  • Martin Kubů,
  • Naděžda Žilková and
  • Mariya Shamzhy

Beilstein J. Org. Chem. 2018, 14, 2931–2939, doi:10.3762/bjoc.14.272

Graphical Abstract
  • various strength. MCM-22(28) and MCM-56(13) exhibited the highest concentrations of acid sites (both Brønsted and Lewis) in accord with their highest Al concentrations. The acid sites concentrations of MCM-22(70) and 2D-MFI(26) were lower and close to each other. The Brønsted acid site concentration of
  • HZSM-5(25) was as high as that of MCM-22(28), however, its Lewis acid site concentration was significantly lower. After supporting Mo compounds the concentrations of Brønsted acid sites decreased significantly which may indicate that MoOx species reacted predominantly with Brønsted acid sites of the
  • been already described [6] and it assumed that most of Mo active species in zeolite-based catalysts are formed by reacting molybdenum oxide with Si-O(H)-Al groups [12][27]. Similarly, Lim et al. showed recently [28], that Brønsted acid sites improve dispersion of molybdenum oxide on the surface
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Published 27 Nov 2018
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  • adsorption showed some peaks at 1646, 1626, 1549 and 1476 cm−1. The peaks at 1646, 1626, and 1549 cm−1 could be due to the vibration of pyridinium (PyH+) species, corresponding to the existence of Brønsted acid sites on the s-MWCNTs 137. The peak at 1476 cm−1 was also labeled to the coordination of electron
  • pair in the nitrogen orbital of pyridine to Brønsted acid sites. No IR signal relating to the Lewis acid sites was detected at 1455 cm−1, as well. Finally, the s-MWCNTs 137 were used in the esterification of palm fatty acid distillate (PFAD) with methanol. The esterification of palm fatty acid with
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Published 01 Nov 2018

β-Hydroxy sulfides and their syntheses

  • Mokgethwa B. Marakalala,
  • Edwin M. Mmutlane and
  • Henok H. Kinfe

Beilstein J. Org. Chem. 2018, 14, 1668–1692, doi:10.3762/bjoc.14.143

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  • their corresponding analogs (Brønsted acid p-TsOH and Lewis base n-Bu3P, respectively) as shown in Scheme 2 [21]. In comparison to the reaction carried out under the same reaction conditions but in aqueous or organic media, it was found that the solvent-free reactions provided the β-hydroxy sulfides in
  • atmosphere [50]. Product yields ranged from 18 to 96%, but in moderate enantioselectivities of 20–64% ee (Scheme 16). Sun and co-workers reported the use of BINOL-based Brønsted acid catalysts such as TRIP 60 for the asymmetric thiolysis of meso-epoxides with benzothiazoles 62 as nucleophiles as shown in
  • sulfide syntheses by ring opening of epoxides under different Lewis and Brønsted acid and base catalysts. n-Bu3P-catalyzed thiolysis of epoxides and aziridines to provide the corresponding β-hydroxy and β-amino sulfides. Zinc(II) chloride-mediated thiolysis of epoxides. Thiolysis of epoxides and one-pot
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Published 05 Jul 2018

Glycosylation reactions mediated by hypervalent iodine: application to the synthesis of nucleosides and carbohydrates

  • Yuichi Yoshimura,
  • Hideaki Wakamatsu,
  • Yoshihiro Natori,
  • Yukako Saito and
  • Noriaki Minakawa

Beilstein J. Org. Chem. 2018, 14, 1595–1618, doi:10.3762/bjoc.14.137

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  • (OTf)2, Yb(OTf)3) and a Brønsted acid (TfOH) were proven useful as activators, by which the reaction finished in a short time and gave the products with high stereoselectivity [79]. Recently, the reaction was revisited by Kajimoto et al., who sought a glycosylation reaction that could be applied to
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Published 28 Jun 2018

Recent applications of chiral calixarenes in asymmetric catalysis

  • Mustafa Durmaz,
  • Erkan Halay and
  • Selahattin Bozkurt

Beilstein J. Org. Chem. 2018, 14, 1389–1412, doi:10.3762/bjoc.14.117

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  • methyl ester 120 in four steps (Scheme 39) [73]. The organocatalytic properties of this inherently chiral calixarene Brønsted acid was firstly examined in the aza-Diels–Alder reaction of imines bearing electron-withdrawing or electron-donating substituents 122 with Danishefsky’s diene (123, Scheme 40
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Published 08 Jun 2018

Fluorocyclisation via I(I)/I(III) catalysis: a concise route to fluorinated oxazolines

  • Felix Scheidt,
  • Christian Thiehoff,
  • Gülay Yilmaz,
  • Stephanie Meyer,
  • Constantin G. Daniliuc,
  • Gerald Kehr and
  • Ryan Gilmour

Beilstein J. Org. Chem. 2018, 14, 1021–1027, doi:10.3762/bjoc.14.88

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  • fluorooxygenation of readily accessible N-allylcarboxamides via an I(I)/I(III) manifold to generate 2-oxazolines containing a fluoromethyl group. Catalysis is conditional on the oxidation competence of Selectfluor®, whilst HF serves as both a fluoride source and Brønsted acid activator. The C(sp3)–F bond of the
  • likelihood that HF also functions as a Brønsted acid activator in catalysis. Employing an amine/HF ratio of 1:4.5, product formation was observed (Table 1, entry 1, 46%). Reducing this ratio to 1:3 had a detrimental effect on catalysis efficiency, generating the product in <5% yield (Table 1, entry 2
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Published 09 May 2018

AuBr3-catalyzed azidation of per-O-acetylated and per-O-benzoylated sugars

  • Jayashree Rajput,
  • Srinivas Hotha and
  • Madhuri Vangala

Beilstein J. Org. Chem. 2018, 14, 682–687, doi:10.3762/bjoc.14.56

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  • of the anomeric acetate carbonyl oxygen, probably the Brønsted acid, HBr, generated from AuBr3 and water present in the reaction medium is also participating in the catalytic cycle. Also no reaction was observed when peracetylated galactose and 3 equiv of trimethylsilyl azide were stirred at room
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Published 22 Mar 2018

Mannich base-connected syntheses mediated by ortho-quinone methides

  • Petra Barta,
  • Ferenc Fülöp and
  • István Szatmári

Beilstein J. Org. Chem. 2018, 14, 560–575, doi:10.3762/bjoc.14.43

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  • -amidoalkyl-2-naphthols carried out in the presence of Lewis and Brønsted acid catalysts. As depicted in Table 1, entries 13–38, the applicability of p-toluenesulfonic acid (p-TSA) [27], montmorillonite K10 [30], Indion-130 [31], iodine (I2) [32], potassium dodecatungstocobaltate (K5CoW12O40·3H2O) [33
  • indole polyheterocycles 49 and 50 in good yields with 90–99% ee. One of the latest publications around this topic has been reported by Deb et al. [86][87]. Various 2-(aminoalkyl)phenols or 1-(aminoalkyl)naphthols 51 were reacted with indoles under Brønsted acid catalysis resulting in 3-(α,α-diarylmethyl
  • aminonaphthols and cyclic amines. Brønsted acid-catalysed reaction between aza-o-QMs and 2- or 3-substituted indoles. Formation of 3-(α,α-diarylmethyl)indoles 52 in different synthetic pathways. Alkylation of o-QMs with N-, O- or S-nucleophiles. Formation of DNA linkers and o-QM mediated polymers. Comparison of
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Published 06 Mar 2018

Synthesis and stability of strongly acidic benzamide derivatives

  • Frederik Diness,
  • Niels J. Bjerrum and
  • Mikael Begtrup

Beilstein J. Org. Chem. 2018, 14, 523–530, doi:10.3762/bjoc.14.38

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  • p-toluenesulfonic acid (5) which is commonly used as a soluble organic acid catalyst in chemical reactions. Remarkably, neither the N-triflylbenzamides nor the N,N’-bis(triflyl)benzimidamides have been studied as Brønsted acid catalysts. Their chemical stability including compatibility with
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Published 27 Feb 2018

One-pot preparation of 4-aryl-3-bromocoumarins from 4-aryl-2-propynoic acids with diaryliodonium salts, TBAB, and Na2S2O8

  • Teppei Sasaki,
  • Katsuhiko Moriyama and
  • Hideo Togo

Beilstein J. Org. Chem. 2018, 14, 345–353, doi:10.3762/bjoc.14.22

Graphical Abstract
  • -vinylphenols at 110 °C [19], the FeCl3-catalyzed areneselenyl-cyclization of aryl 2-alkynoates with ArSeSeAr at rt [20], and the Rh-catalyzed annulation of arylthiocarbamates with alkynes/AgOTf/Cu(OAc)2 at 120 °C [21]. As examples of the transition-metal-free construction of the coumarin skeleton, the Brønsted
  • acid-catalyzed reaction of phenols and propynoic acids [22] and the (−)-riboflavin-catalyzed photochemical reaction of cinnamic acids [23] were reported recently. Moreover, the use of radical cyclization for the construction of the coumarin skeleton has become widespread. Examples include the radical
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Published 05 Feb 2018

Novel amide-functionalized chloramphenicol base bifunctional organocatalysts for enantioselective alcoholysis of meso-cyclic anhydrides

  • Lingjun Xu,
  • Shuwen Han,
  • Linjie Yan,
  • Haifeng Wang,
  • Haihui Peng and
  • Fener Chen

Beilstein J. Org. Chem. 2018, 14, 309–317, doi:10.3762/bjoc.14.19

Graphical Abstract
  • ][20] and valine [21] etc. [22][23][24][25][26][27][28][29], while fully synthetic catalysts are rare, only involving Brønsted acid/base catalysts [30], cyclohexanediamine catalysts [31][32], and diphenylethylenediamine catalysts [33][34]. Significant progress in our laboratory has been made in the
  • desired bifunctional Brønsted acid/base reactivity for enantioselective desymmetrization of anhydrides [48][49]. Results and Discussion A series of new chloramphenicol based-amide bifunctional catalysts 7a–q (Scheme 1) were synthesized from the appropriate optically pure (1R,2R)-diamine 6, prepared via
  • anhydride 8a was carried out in various conditions with 10 equivalents of methanol. Resultingly, this novel Brønsted acid/base catalysts 7a–q proved to be sufficiently active and gave the monoester product with high yield and superior enantioselectivity, suggesting the unique reactivity of this amide-based
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Published 31 Jan 2018

Regiodivergent condensation of 5-alkoxycarbonyl-1H-pyrrol-2,3-diones with cyclic ketazinones en route to spirocyclic scaffolds

  • Alexey Yu. Dubovtsev,
  • Maksim V. Dmitriev,
  • Аndrey N. Maslivets and
  • Michael Rubin

Beilstein J. Org. Chem. 2017, 13, 2179–2185, doi:10.3762/bjoc.13.218

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  • tertiary amines), while the use of stronger bases (hydroxides or alkoxides) caused decomposition of the base-sensitive 1H-pyrrole-2,3-dione moiety 9. An attempt to perform the reaction in the presence of catalytic amounts of Brønsted acid (TsOH) also did not provide the spirocyclic products. Instead
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Published 19 Oct 2017

New bio-nanocomposites based on iron oxides and polysaccharides applied to oxidation and alkylation reactions

  • Daily Rodríguez-Padrón,
  • Alina M. Balu,
  • Antonio A. Romero and
  • Rafael Luque

Beilstein J. Org. Chem. 2017, 13, 1982–1993, doi:10.3762/bjoc.13.194

Graphical Abstract
  • pulses. Pyridine, due to low steric hindrance, adsorbs nonspecifically in both types of centers, while dimethylpyridine adsorbs specifically on Brønsted acid centers, due to the high steric hindrance of the methyl groups [54]. It is noticeable that the TiO2-Fe2O3-PS4 catalyst possesses both Lewis and
  • Brønsted acid sites with a more marked Lewis acidity. The Fe2O3-PS4-MNP material presents instead only Lewis acid sites, while the Fe2O3-PS4 does not show appreciable acidity to be quantized (Table 2). Acidity measurements from both methodologies (PY DRIFT, PY and DMPY pulse chromatography titration data
  • ) were generally in good agreement, supporting the validity of our assumption on DMPY adsorbing selectively on Brønsted acid sites. Inductively coupled plasma–mass spectrometry (ICP–MS) The elemental composition of the TiO2-Fe2O3-PS4 material was determined by ICP–MS. The content of iron and titanium was
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Published 21 Sep 2017

Synthesis of new pyrrolidine-based organocatalysts and study of their use in the asymmetric Michael addition of aldehydes to nitroolefins

  • Alejandro Castán,
  • Ramón Badorrey,
  • José A. Gálvez and
  • María D. Díaz-de-Villegas

Beilstein J. Org. Chem. 2017, 13, 612–619, doi:10.3762/bjoc.13.59

Graphical Abstract
  • reaction conditions [21]. For example, in secondary amine-catalysed asymmetric reactions a Brønsted acid additive was found to accelerate the formation of the enamine intermediate and thus to improve not only the reactivity but also the diastereoselectivity and enantioselectivity [22][23]. On the other
  • hand, the presence of thiourea additives could activate nitroalkenes when used as substrates by double hydrogen bonding, which lead to improved reactivities [24]. Based on these findings, we decided to explore the effect of a Brønsted acid or an achiral thiourea as additive on the reaction between
  • possibility of accelerating the formation of the enamine intermediate and simultaneously activating the nitroalkene by using a combination of organocatalyst OC4, a Brønsted acid and an achiral thiourea. Thus the reaction was repeated in the presence of a combination of benzoic acid and N,N'-diphenylthiourea
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Published 27 Mar 2017

Brønsted acid-mediated cyclization–dehydrosulfonylation/reduction sequences: An easy access to pyrazinoisoquinolines and pyridopyrazines

  • Ramana Sreenivasa Rao and
  • Chinnasamy Ramaraj Ramanathan

Beilstein J. Org. Chem. 2017, 13, 428–440, doi:10.3762/bjoc.13.46

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  • strategy using a Brønsted acid. Subsequent dehydrosulfonylation reactions of the ene-diamides, in a one pot manner, smoothly transformed them to substituted pyrazinones. A concise synthesis of praziquantel (1) has also been achieved through this method. Keywords: Brønsted acid; piperazine-2,6-diones
  • corresponding products. Further, these 4-benzenesulfonylpiperazine-2,6-diones were subjected to an imide carbonyl group activation strategy, to develop a practical approach to synthesize pyrazinoisoquinoline and pyridopyrazines via Brønsted acid assisted 6-exo-trig cyclization of arylethylpiperazine-2,6-diones
  • Brønsted acid [32]. Sulfonamides also participate in amide hydrolysis with external nucleophiles such as phosphide anions [33] or phenyldimethylsilyllithium [34]. The combinations of thiophenol/K2CO3 [35] or NaOH/MeOH [36] are also known to hydrolyse sulfonamides. These methods lead to the formation of the
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Published 07 Mar 2017

Synthesis of structurally diverse 3,4-dihydropyrimidin-2(1H)-ones via sequential Biginelli and Passerini reactions

  • Andreas C. Boukis,
  • Baptiste Monney and
  • Michael A. R. Meier

Beilstein J. Org. Chem. 2017, 13, 54–62, doi:10.3762/bjoc.13.7

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  • , aldehyde 1 is activated by a Lewis- or a Brønsted acid. In the next step, urea/thiourea 2 can serve as a nucleophile and react with the activated carbonyl carbon to form a heminal species. However, under acidic conditions heminals can eliminate water and form an N-acyliminium cation 3. This reactive cation
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Published 09 Jan 2017

New approaches to organocatalysis based on C–H and C–X bonding for electrophilic substrate activation

  • Pavel Nagorny and
  • Zhankui Sun

Beilstein J. Org. Chem. 2016, 12, 2834–2848, doi:10.3762/bjoc.12.283

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  • reactive complex with the LUMO. These results are further backed up by control experiments demonstrating that catalytic quantities of hydroiodic acid were less effective in promoting this reaction than molecular iodine, and hidden Brønsted acid catalysis is unlikely to be operational in these studies. In
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Published 23 Dec 2016

cis-Diastereoselective synthesis of chroman-fused tetralins as B-ring-modified analogues of brazilin

  • Dimpee Gogoi,
  • Runjun Devi,
  • Pallab Pahari,
  • Bipul Sarma and
  • Sajal Kumar Das

Beilstein J. Org. Chem. 2016, 12, 2816–2822, doi:10.3762/bjoc.12.280

Graphical Abstract
  • cyclization make this methodology highly practical for the use in organic synthesis. Recently, we have reported the synthesis of diverse trans-4-arylchroman-3-ols via Brønsted acid catalysed regio- and stereoselective IFCEA cyclization of 2-(aryloxymethyl)-3-aryloxiranes [22][23]. The use of IFCEA cyclization
  • Friedel–Crafts cyclization (Scheme 2, upper panel) and the products are relevant in the field of natural product-like molecules, because the synthesized molecules are close analogs of a natural product (brazilin). Moreover, the use of TsOH·H2O as an easily-accesible Brønsted acid catalyst with low loading
  • convenient Brønsted acid-catalyzed, metal-free, stereoselective synthesis of 6a,7,8,12b-tetrahydro-6H-naphtho[2,1-c]chromen-6a-ols as B-ring-modified analogues of brazilin using starting materials derived from inexpensive 1-tetralone and phenol derivatives. Our worries concerning the formation cis–trans
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Published 21 Dec 2016

Diels–Alder reactions in confined spaces: the influence of catalyst structure and the nature of active sites for the retro-Diels–Alder reaction

  • Ángel Cantín,
  • M. Victoria Gomez and
  • Antonio de la Hoz

Beilstein J. Org. Chem. 2016, 12, 2181–2188, doi:10.3762/bjoc.12.208

Graphical Abstract
  • effect within the pore and diffusion limitations are discussed. Introduction of Lewis or Brønsted acid sites on the walls of the zeolite strongly increases the reaction rate. However, contrary to what occurs with mesoporous molecular sieves (MCM-41), Beta zeolite does not catalyse the retro-Diels–Alder
  • terephthalate that is used for the large-scale manufacture of plastic bottles among others. The authors do not find transport limitations within the zeolite framework to the rate of the reaction [27]. Interestingly, when Brønsted acid containing zeolites (Al-β) are used as catalyst, there is a decrease in the
  • Lewis and Brønsted acid sites in the conversion (a) and selectivity (b) of the DAR. Effect of pore size in the conversion (a) and selectivity (b) of the DAR. Comparison of conversion (a) and selectivity (b) of the DAR catalysed by Al-Beta zeolite and MCM-41. Comparison of conversion (a) and selectivity
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Published 13 Oct 2016

Synergistic chiral iminium and palladium catalysis: Highly regio- and enantioselective [3 + 2] annulation reaction of 2-vinylcyclopropanes with enals

  • Haipan Zhu,
  • Peile Du,
  • Jianjun Li,
  • Ziyang Liao,
  • Guohua Liu,
  • Hao Li and
  • Wei Wang

Beilstein J. Org. Chem. 2016, 12, 1340–1347, doi:10.3762/bjoc.12.127

Graphical Abstract
  • synthesis by offering power for improving reaction efficiency and/or realizing impossible processes [46][47][48][49][50][51][52][53][54][55]. Recently, we developed an enantioselective addition of aldehydes to vinylpyridines and vinylarenes catalyzed by synergistic catalysis of iminium catalyst and Brønsted
  • acid [56]. Herein we wish to disclose the first synergistic catalytic enantioselective [3 + 2] annulation reaction between 2-vinylcyclopropanes and enals via 1,4-addition (Scheme 1, reaction 2). The process proceeds highly regio- and enantioselectively with C=C bonds in enals. Notably, a synergistic
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Published 29 Jun 2016

Efficient syntheses of climate relevant isoprene nitrates and (1R,5S)-(−)-myrtenol nitrate

  • Sean P. Bew,
  • Glyn D. Hiatt-Gipson,
  • Graham P. Mills and
  • Claire E. Reeves

Beilstein J. Org. Chem. 2016, 12, 1081–1095, doi:10.3762/bjoc.12.103

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  • convenient and cheap Brønsted acid, transformed a range of epoxides [20] into the corresponding nitrato alcohols. Shepson substituted ethylene oxide for commercially available isoprene epoxide and generated eight stereo- and structurally isomeric IPNs. Within this mixture 3° nitrate rac-7, 1° nitrate rac-8
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Published 27 May 2016

A practical way to synthesize chiral fluoro-containing polyhydro-2H-chromenes from monoterpenoids

  • Oksana S. Mikhalchenko,
  • Dina V. Korchagina,
  • Konstantin P. Volcho and
  • Nariman F. Salakhutdinov

Beilstein J. Org. Chem. 2016, 12, 648–653, doi:10.3762/bjoc.12.64

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  • strong Brønsted acid and may be presented as H+(BF3·OH)− [27][28]. Based on these data, it may be supposed that in the case of a 5-fold excess of water relative to BF3·Et2O, the reaction medium may contain both BF3·H2O and products of the partial hydrolysis of BF3·Et2O that may act both as catalysts and
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Published 06 Apr 2016

The aminoindanol core as a key scaffold in bifunctional organocatalysts

  • Isaac G. Sonsona,
  • Eugenia Marqués-López and
  • Raquel P. Herrera

Beilstein J. Org. Chem. 2016, 12, 505–523, doi:10.3762/bjoc.12.50

Graphical Abstract
  • chiral thiourea organocatalyst and a Brønsted acid (AH) could provide better results in terms of reactivity and enantioselectivity. Thus, in 2011, they published an article where it was proved that the synergic system between the thiourea ent-4 and mandelic acid led to the final products 5 with a
  • external Brønsted acid. Proposed transition state TS7 for the Friedel–Crafts reaction of indole and α,β-unsaturated acyl phosphonates catalyzed by ent-4. Possible transition states TS8 and TS9 in the asymmetric addition of indoles 2 to the β,γ-unsaturated α-ketoesters 26 catalyzed by ent-4. Transition
  • catalyzed by thiourea ent-4 in the presence of D-mandelic acid as a Brønsted acid additive. Friedel–Crafts alkylation of indoles catalyzed by the chiral thioamide 6. Scalable tandem C2/C3-annulation of indoles, catalyzed by the thioamide ent-6. Plausible tandem process mechanism for the sequential, double
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Published 14 Mar 2016
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