Search results

Search for "Lewis base" in Full Text gives 71 result(s) in Beilstein Journal of Organic Chemistry.

Direct C(sp3)–H allylation of 2-alkylpyridines with Morita–Baylis–Hillman carbonates via a tandem nucleophilic substitution/aza-Cope rearrangement

  • Siyu Wang,
  • Lianyou Zheng,
  • Shutao Wang,
  • Shulin Ning,
  • Zhuoqi Zhang and
  • Jinbao Xiang

Beilstein J. Org. Chem. 2021, 17, 2505–2510, doi:10.3762/bjoc.17.167

Graphical Abstract
  • acetamides and acetates catalyzed synergistically by a metal acyclic iridium complex and a chiral Cu(I) complex [19]. Besides transition-metal-catalyzed allylic substitution reactions, Lewis-base-catalyzed allylic functionalizations using Morita−Baylis−Hillman (MBH) adducts as electrophilic allylic
  • synergistic catalyzed allylic alkylation between electron-deficient 2-ethyl benzoxazoles and MBH carbonates by the combination of a Lewis base and a metal salt [24]. In their studies, although pyridine derivatives were also applicable in the reaction, the presence of a strong electron-withdrawing NO2 group
PDF
Album
Supp Info
Letter
Published 01 Oct 2021

Halides as versatile anions in asymmetric anion-binding organocatalysis

  • Lukas Schifferer,
  • Martin Stinglhamer,
  • Kirandeep Kaur and
  • Olga García Macheño

Beilstein J. Org. Chem. 2021, 17, 2270–2286, doi:10.3762/bjoc.17.145

Graphical Abstract
  • development of an enantioselective aza-Sakurai cyclization (Scheme 12) [70]. In this transformation, a chiral thiourea catalyst 58 with a dibenzothiophene functionality serves as a dual H-bond donor and Lewis base to facilitate the cyclization of hydroxylactams 56. Thus, indolizine and quinolidizine
  • frameworks 57 were accessed in excellent yields up to 93% and enantioselectivities up to 94% ee. Increased aromaticity proved again to be essential for achieving high enantioselectivities. Additionally, Lewis base activation of the allylsilane substrates through the thiourea sulfur atom is proposed to be
  • , and c) asymmetric Mannich synthesis of α-amino esters. Thiourea-catalyzed enantioselective polycyclization reaction of hydroxylactams 51 through cation–π interaction. Enantioselective aza-Sakurai cyclization of hydroxylactams 56 implicating additional cation–π and Lewis base activation
PDF
Album
Review
Published 01 Sep 2021

Catalyzed and uncatalyzed procedures for the syntheses of isomeric covalent multi-indolyl hetero non-metallides: an account

  • Ranadeep Talukdar

Beilstein J. Org. Chem. 2021, 17, 2102–2122, doi:10.3762/bjoc.17.137

Graphical Abstract
  • synthesized the similar compound 40, using a catalytic Lewis acid Zn(NTf2)2 and stoichiometric Lewis base γ-picoline combination in n-butyronitrile as solvent (Scheme 7c) [61]. This electron-donating solvent and toluene in the former reaction acted as stabilizers to the electron-deficient silicon species in
PDF
Album
Review
Published 19 Aug 2021

Electron-rich triarylphosphines as nucleophilic catalysts for oxa-Michael reactions

  • Susanne M. Fischer,
  • Simon Renner,
  • A. Daniel Boese and
  • Christian Slugovc

Beilstein J. Org. Chem. 2021, 17, 1689–1697, doi:10.3762/bjoc.17.117

Graphical Abstract
  • aromatic rings with methoxy groups increases the pKa value from 1.31 (TPP) to 4.20 (TMTPP) (Figure 1). Methyl cation affinities (MCA) which can be used as descriptors for the nucleophilicity of a compound were calculated by Lindner et al. who suggested TMTPP (651.0 kJ/mol) to be a stronger Lewis base than
PDF
Album
Supp Info
Full Research Paper
Published 21 Jul 2021

Methodologies for the synthesis of quaternary carbon centers via hydroalkylation of unactivated olefins: twenty years of advances

  • Thiago S. Silva and
  • Fernando Coelho

Beilstein J. Org. Chem. 2021, 17, 1565–1590, doi:10.3762/bjoc.17.112

Graphical Abstract
  • diastereoselectivity in the synthesis of bicyclic compounds (dr > 20:1, Scheme 19, 37d, 37e, and 37g). Substrates containing Lewis base moieties (Scheme 19, 36k) were tolerated in the reported reaction conditions, thereby representing a synthetic gain over other olefin isomerization methodologies. An important feature
PDF
Album
Review
Published 07 Jul 2021

Metal-free glycosylation with glycosyl fluorides in liquid SO2

  • Krista Gulbe,
  • Jevgeņija Lugiņina,
  • Edijs Jansons,
  • Artis Kinens and
  • Māris Turks

Beilstein J. Org. Chem. 2021, 17, 964–976, doi:10.3762/bjoc.17.78

Graphical Abstract
  • –base (HSAB) theory the fluoride leaving group is considered to be a hard Lewis base [12][13]. Consequently, a series of fluoride-activating systems containing hard Lewis acidic centers have been published following the first report [7][14][15][16][17]. Among these promoters Sn(II) species (SnCl2–AgX, X
  • does not depend on the configuration of the anomeric center of the glycosyl donor. This observation points to the formation of a solvent-separated ion pair (SSIP) between the oxocarbenium ion and a counteranion, for example, fluorosulfite. At the same time, according to the Lewis base properties
PDF
Album
Supp Info
Full Research Paper
Published 29 Apr 2021

Synthetic reactions driven by electron-donor–acceptor (EDA) complexes

  • Zhonglie Yang,
  • Yutong Liu,
  • Kun Cao,
  • Xiaobin Zhang,
  • Hezhong Jiang and
  • Jiahong Li

Beilstein J. Org. Chem. 2021, 17, 771–799, doi:10.3762/bjoc.17.67

Graphical Abstract
  • spectroscopy shows that phosphono radicals could proceed throughout the reaction. A halogen bond (XB) is a noncovalent interaction formed between a halogen atom and a neutral or negatively charged Lewis base. It is a kind of weak intermolecular interaction analogous to a hydrogen bond and basically can be
PDF
Album
Review
Published 06 Apr 2021

Reactions of 3-aryl-1-(trifluoromethyl)prop-2-yn-1-iminium salts with 1,3-dienes and styrenes

  • Thomas Schneider,
  • Michael Keim,
  • Bianca Seitz and
  • Gerhard Maas

Beilstein J. Org. Chem. 2020, 16, 2064–2072, doi:10.3762/bjoc.16.173

Graphical Abstract
  • reaction of trifluoroacetaldehyde hemiaminals with enolizable carbonyl compounds in the presence of a strong base [23], the reaction of aldiminium salts with (trifluoromethyl)trimethylsilane/Lewis base [24], and the preparation of secondary α-(trifluoromethyl)propargylamines from imines CF3CH=NR and
PDF
Album
Supp Info
Full Research Paper
Published 24 Aug 2020

Fluorohydration of alkynes via I(I)/I(III) catalysis

  • Jessica Neufeld,
  • Constantin G. Daniliuc and
  • Ryan Gilmour

Beilstein J. Org. Chem. 2020, 16, 1627–1635, doi:10.3762/bjoc.16.135

Graphical Abstract
  • Lewis base upon ligand exchange (Figure 5) [56]. This working hypothesis may also rationalise the deletion experiment (10), the recalcitrance of acetyl derivatives, and the striking reactivity disparity between amides (12/13) and the phthalimide derivative 16. Finally, to investigate the fate of water
PDF
Album
Supp Info
Full Research Paper
Published 10 Jul 2020

Heterogeneous photocatalysis in flow chemical reactors

  • Christopher G. Thomson,
  • Ai-Lan Lee and
  • Filipe Vilela

Beilstein J. Org. Chem. 2020, 16, 1495–1549, doi:10.3762/bjoc.16.125

Graphical Abstract
PDF
Album
Review
Published 26 Jun 2020

Synthesis, liquid crystalline behaviour and structure–property relationships of 1,3-bis(5-substituted-1,3,4-oxadiazol-2-yl)benzenes

  • Afef Mabrouki,
  • Malek Fouzai,
  • Armand Soldera,
  • Abdelkader Kriaa and
  • Ahmed Hedhli

Beilstein J. Org. Chem. 2020, 16, 149–158, doi:10.3762/bjoc.16.17

Graphical Abstract
  • electron D–A concept may be regarded as Lewis base–Lewis acid type or charge-transfer. Based upon the above considerations, we could attribute the close proximity of fluorinated chains in conformation B to a throw space electron D–A intramolecular interaction between the perfluoroalkyl chains (electron
PDF
Album
Supp Info
Full Research Paper
Published 31 Jan 2020

Fluorinated azobenzenes as supramolecular halogen-bonding building blocks

  • Esther Nieland,
  • Oliver Weingart and
  • Bernd M. Schmidt

Beilstein J. Org. Chem. 2019, 15, 2013–2019, doi:10.3762/bjoc.15.197

Graphical Abstract
  • noncovalent interaction between a polarized halogen atom (the halogen bond donor) and a Lewis base (the halogen bond acceptor) [1][2]. A prominent example regarding the origin of halogen bonding can be found in inorganic solid-state chemistry. The structurally diverse group of polyiodides, with its rich
PDF
Album
Supp Info
Letter
Published 23 Aug 2019

Synthesis of polydicyclopentadiene using the Cp2TiCl2/Et2AlCl catalytic system and thin-layer oxidation of the polymer in air

  • Zhargolma B. Bazarova,
  • Ludmila S. Soroka,
  • Alex A. Lyapkov,
  • Мekhman S. Yusubov and
  • Francis Verpoort

Beilstein J. Org. Chem. 2019, 15, 733–745, doi:10.3762/bjoc.15.69

Graphical Abstract
  • , which reacts with R-olefin and a Lewis base to form stable crystalline titanacyclobutanes. Both titanium carbene and titanacycles are ROMP catalysts (Scheme 4). PDCPD polymers were obtained by precipitation in ethanol, dried and characterized by FTIR, NMR, and GPC. Figure 6 displays a typical infrared
PDF
Album
Full Research Paper
Published 20 Mar 2019

Sigmatropic rearrangements of cyclopropenylcarbinol derivatives. Access to diversely substituted alkylidenecyclopropanes

  • Guillaume Ernouf,
  • Jean-Louis Brayer,
  • Christophe Meyer and
  • Janine Cossy

Beilstein J. Org. Chem. 2019, 15, 333–350, doi:10.3762/bjoc.15.29

Graphical Abstract
  • diastereoselectivity. However, the sigmatropic rearrangement of the highly hindered di(tert-butyl)phosphinite 6j and tetra(isopropyl) phosphorodiamidite 6k did not occur (Scheme 7) [37]. The mechanism proposed by Rubin et al. involves a reversible addition of the Lewis base (DBU) on the cyclopropene double bond at C2
  • ’ would then be obtained and would eventually produce the diastereomeric phosphine oxides 7 and 7’. Computational studies indicated that the facial selectivity of the initial attack of the Lewis base (DBU) was not responsible for the observed diastereocontrol because of the low difference between the
  • )-1f. Selective reduction of phosphine oxide (E)-3f. Attempted thermal [2,3]-sigmatropic rearrangement of phosphinite 6a. Computed activation barriers and free enthalpies. [2,3]-Sigmatropic rearrangement of phosphinites 6a–j. Proposed mechanism for the Lewis base-catalyzed rearrangement of phosphinites
PDF
Album
Review
Published 05 Feb 2019

DABCO- and DBU-promoted one-pot reaction of N-sulfonyl ketimines with Morita–Baylis–Hillman carbonates: a sequential approach to (2-hydroxyaryl)nicotinate derivatives

  • Soumitra Guin,
  • Raman Gupta,
  • Debashis Majee and
  • Sampak Samanta

Beilstein J. Org. Chem. 2018, 14, 2771–2778, doi:10.3762/bjoc.14.254

Graphical Abstract
  • on the above experimental results as well as our previous report on DABCO-catalyzed reactions of cyclic sulfamidate imines with MBH carbonates of isatins [75], a plausible mechanism is presented and depicted in Scheme 2. For the first step, the nucleophilic Lewis base DABCO reacts with 2a in an SN2
PDF
Album
Supp Info
Full Research Paper
Published 02 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

Graphical Abstract
  • 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
PDF
Album
Review
Published 05 Jul 2018

An air-stable bisboron complex: a practical bidentate Lewis acid catalyst

  • Longcheng Hong,
  • Sebastian Ahles,
  • Andreas H. Heindl,
  • Gastelle Tiétcha,
  • Andrey Petrov,
  • Zhenpin Lu,
  • Christian Logemann and
  • Hermann A. Wegner

Beilstein J. Org. Chem. 2018, 14, 618–625, doi:10.3762/bjoc.14.48

Graphical Abstract
  • attributed to the free vacant p-orbital of the boron atom leading to further transformations, such as decomposition via radicals (O2), reactions with nucleophiles (H2O) as well as the formations of adducts. From this perspective, a suitable Lewis base may form a Lewis complex and subsequently occupy the p
  • -dihydroboranthrene (A, 8.0 mg, 0.0392 mmol, 1.00 equiv) and Lewis base (for monodentate: 0.0784 mmol, 2.00 equiv; for bidentate: 0.0392 mmol, 1.00 equiv) were dissolved in 0.5 mL CDCl3 in an NMR tube (in case of 3,6-dimethylpyridazine, THF-d8 was used as solvent). The NMR tube was sealed and kept for 4 h and then
PDF
Album
Supp Info
Full Research Paper
Published 13 Mar 2018

Nucleophilic fluoroalkylation/cyclization route to fluorinated phthalides

  • Masanori Inaba,
  • Tatsuya Sakai,
  • Shun Shinada,
  • Tsuyuka Sugiishi,
  • Yuta Nishina,
  • Norio Shibata and
  • Hideki Amii

Beilstein J. Org. Chem. 2018, 14, 182–186, doi:10.3762/bjoc.14.12

Graphical Abstract
  • work-up under acidic conditions, 3-(trifluoromethyl)-1(3H)-isobenzofuranone (1a) was obtained in 99% NMR yield (95% isolated yield) (Table 1, entry 1). As a good alternative activator of CF3–SiMe3, the use of a Lewis base such as triethylamine [22][23] worked well for the synthesis of 3
PDF
Album
Supp Info
Full Research Paper
Published 19 Jan 2018

Syntheses, structures, and stabilities of aliphatic and aromatic fluorous iodine(I) and iodine(III) compounds: the role of iodine Lewis basicity

  • Tathagata Mukherjee,
  • Soumik Biswas,
  • Andreas Ehnbom,
  • Subrata K. Ghosh,
  • Ibrahim El-Zoghbi,
  • Nattamai Bhuvanesh,
  • Hassan S. Bazzi and
  • John A. Gladysz

Beilstein J. Org. Chem. 2017, 13, 2486–2501, doi:10.3762/bjoc.13.246

Graphical Abstract
  • related ethereal phase tags or "ponytails" [40][41]. Accordingly, oligomeric fluorous ethers that terminate in CH2OH groups, CF3CF2CF2O(CF(CF3)CF2O)xCF(CF3)CH2OH, are commercially available. These are abbreviated RfOxCH2OH, and the ethereal oxygen atoms have essentially no Lewis base character. In some
PDF
Album
Supp Info
Full Research Paper
Published 23 Nov 2017

Main group mechanochemistry

  • Agota A. Gečiauskaitė and
  • Felipe García

Beilstein J. Org. Chem. 2017, 13, 2068–2077, doi:10.3762/bjoc.13.204

Graphical Abstract
  • ) directly from germanium metal or germanium dioxide (GeO2) was recently reported [87]. Milling of germanium powder or GeO2 with quinone or catechol, respectively, in the presence of a Lewis base under LAG conditions, produced a series of germanium complexes (see Scheme 5). These complexes are inherently
PDF
Album
Review
Published 05 Oct 2017

Strategies toward protecting group-free glycosylation through selective activation of the anomeric center

  • A. Michael Downey and
  • Michal Hocek

Beilstein J. Org. Chem. 2017, 13, 1239–1279, doi:10.3762/bjoc.13.123

Graphical Abstract
  • in one (very low yielding) or in four steps from D-mannose in a straightforward manner (Scheme 13a). In the proposed mechanism (Scheme 13b), the anomeric oxygen self-displaces the bromide (hard Lewis base, soft Lewis base pairing) at the 4-position to form a THF ring. The ring oxygen then displaces
  • fashion [58][59]. Therefore, they postulated that by using the correct divalent cation and suitable Lewis acid/Lewis base pairing, the necessary transition-state organization to favor glycosylation of a glycosyl fluoride would outcompete hydrolysis in the aqueous medium. This would lead to a simple non
PDF
Album
Review
Published 27 Jun 2017

Development of chiral metal amides as highly reactive catalysts for asymmetric [3 + 2] cycloadditions

  • Yasuhiro Yamashita,
  • Susumu Yoshimoto,
  • Mark J. Dutton and
  • Shū Kobayashi

Beilstein J. Org. Chem. 2016, 12, 1447–1452, doi:10.3762/bjoc.12.140

Graphical Abstract
  • of chiral Lewis acid/Brønsted base-catalyst systems have been developed; however, decreasing the catalyst loading is sometimes problematic either because of the low reactivity of catalysts or because the catalyst activity can be reduced through Lewis acid–Lewis base interaction between catalysts and
PDF
Album
Letter
Published 13 Jul 2016

Synthesis of 2,1-benzisoxazole-3(1H)-ones by base-mediated photochemical N–O bond-forming cyclization of 2-azidobenzoic acids

  • Daria Yu. Dzhons and
  • Andrei V. Budruev

Beilstein J. Org. Chem. 2016, 12, 874–881, doi:10.3762/bjoc.12.86

Graphical Abstract
  • an intermediate singlet nitrene. Possibly, similar to the benzofuroxan and 3-amino-6-nitro-2,1-benzisoxazole formation, the carboxylate group of A (Lewis base) donates an electron lone pair to the electron-deficient singlet nitrene fragment of A (Lewis acid) with formation of the N–O bond in 2
PDF
Album
Supp Info
Full Research Paper
Published 04 May 2016

Surprisingly facile CO2 insertion into cobalt alkoxide bonds: A theoretical investigation

  • Willem K. Offermans,
  • Claudia Bizzarri,
  • Walter Leitner and
  • Thomas E. Müller

Beilstein J. Org. Chem. 2015, 11, 1340–1351, doi:10.3762/bjoc.11.144

Graphical Abstract
  • the cobalt–carbonate bond is stronger than the cobalt–alkoxide bond. Since the alkoxide is a stronger Lewis base than the carbonate, we calculated an increase in bond strength between the carbonate unit and cobalt center with respect to the cobalt(III)–alkoxide bond, depending on the nucleophilicity
  • electrophile, it requires a strong Lewis base in order for CO2 to react [54]. Addition of CO2 to the activated epoxide then occurs with a very low activation barrier [55]. In contrast, it has been generally believed up to now that, in the catalysed reaction of CO2 and epoxides, both reactants need to be
PDF
Album
Supp Info
Full Research Paper
Published 31 Jul 2015

Diastereoselective and enantioselective conjugate addition reactions utilizing α,β-unsaturated amides and lactams

  • Katherine M. Byrd

Beilstein J. Org. Chem. 2015, 11, 530–562, doi:10.3762/bjoc.11.60

Graphical Abstract
  • /hard Brønsted base/hard Lewis base cooperative catalysis system, a strategy that has been used in other reactions [193][194][195][196] (Scheme 22). In the case of the reaction above, the alkynylide was generated from [Cu(CH3CN)4]PF6, (R)-3,5-iPr-4-Me2N-MeOBIPHEP, and Li(OC6H4-p-OMe) [197][198]. The
  • hard Lewis base in this reaction was bisphosphine oxide 95, which was added to enhance the Brønsted basicity of Li(OC6H4-p-OMe) by coordinating to the lithium counterion. The authors were able to obtain the 1,4-addition products in high yields and enantioselectivities when they used various aryl
  • acetylides. Also, this methodology was expanded to various alkyl acetylides. In order to obtain high enantioselectivities, they varied the copper source, ligand and the hard Lewis base (Scheme 23). The authors demonstrated the utility of this reaction by applying it towards the synthesis of a potent GPR40
PDF
Album
Review
Published 23 Apr 2015
Other Beilstein-Institut Open Science Activities