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Search for "deprotonation" in Full Text gives 552 result(s) in Beilstein Journal of Organic Chemistry. Showing first 200.

Synthesis and late stage modifications of Cyl derivatives

  • Phil Servatius and
  • Uli Kazmaier

Beilstein J. Org. Chem. 2022, 18, 174–181, doi:10.3762/bjoc.18.19

Graphical Abstract
  • , epimerization is prevented through deprotonation of amide NH bonds, as argued by Seebach for Li enolates [53][54]. Nevertheless, isoleucine was prone to epimerize under the reaction conditions due to its vicinity to proline and therewith lack of the “protecting” NH group. Since no full conversion was observed
  • , entry 1). Since the reaction seemed to stop after 30–40% conversion, it was speculated that the ester enolate chelate complex formation was incomplete due to consumption of the base. For instance, deprotonation of tyrosine residues in benzyl position has been observed previously in the derivatization of
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Published 04 Feb 2022

Ready access to 7,8-dihydroindolo[2,3-d][1]benzazepine-6(5H)-one scaffold and analogues via early-stage Fischer ring-closure reaction

  • Irina Kuznetcova,
  • Felix Bacher,
  • Daniel Vegh,
  • Hsiang-Yu Chuang and
  • Vladimir B. Arion

Beilstein J. Org. Chem. 2022, 18, 143–151, doi:10.3762/bjoc.18.15

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  • % yield. This is most likely due to the strongly basic conditions (NaH) needed for the attachment of the ethoxymethyl protecting group, which might lead to deprotonation at the CH2 group (C7) followed by the formation of undesired side products. Being disappointed by the inefficiency of this route with at
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Published 26 Jan 2022

Chemoselective N-acylation of indoles using thioesters as acyl source

  • Tianri Du,
  • Xiangmu Wei,
  • Honghong Xu,
  • Xin Zhang,
  • Ruiru Fang,
  • Zheng Yuan,
  • Zhi Liang and
  • Yahui Li

Beilstein J. Org. Chem. 2022, 18, 89–94, doi:10.3762/bjoc.18.9

Graphical Abstract
  • acid (4) (Scheme 4, reaction 4). A plausible reaction mechanism has been proposed based on the results of the control experiments. As shown in Scheme 5, the reaction starts with a base-promoted deprotonation of indole forming intermediate A. In the next step nucleophilic substitution between
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Published 10 Jan 2022

The enzyme mechanism of patchoulol synthase

  • Houchao Xu,
  • Bernd Goldfuss,
  • Gregor Schnakenburg and
  • Jeroen S. Dickschat

Beilstein J. Org. Chem. 2022, 18, 13–24, doi:10.3762/bjoc.18.2

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  • alternative biosynthetic mechanism that also starts with a cyclisation of FPP to A (Scheme 2A) [10], but then a subsequent deprotonation to 8, an important neutral intermediate in the biosynthesis of many sesquiterpenes [11], is assumed. A reprotonation-induced cyclisation leads to E that is again
  • (Scheme 2B). According to the FPP biosynthesis as established by Cornforth and co-workers, these reactions should proceed with full retainment of all labellings [12]. For isolated 3 a loss of one of the three 3H atoms was reported that is explainable by the deprotonation step from E to 6 [10], but
  • reported, which was explained by an unusual intramolecular deuterium transfer. Herein, the deuteron is released from (2-2H)-J in the deprotonation step to 5 (or other enzyme products losing the same hydrogen in the terminal deprotonation). Deprotonation of (2-2H)-H was suggested to produce the unknown
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Published 03 Jan 2022

Stepwise PEG synthesis featuring deprotection and coupling in one pot

  • Logan Mikesell,
  • Dhananjani N. A. M. Eriyagama,
  • Yipeng Yin,
  • Bao-Yuan Lu and
  • Shiyue Fang

Beilstein J. Org. Chem. 2021, 17, 2976–2982, doi:10.3762/bjoc.17.207

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  • – deprotection, deprotonation and coupling – in two pots. Here, we report a more convenient approach for PEG synthesis featuring the use of a base-labile protecting group such as the phenethyl group. Using this approach, each elongation of PEG can be achieved in two steps – deprotection and coupling – in only
  • one pot. The deprotonation step, and the isolation and purification of the intermediate product after deprotection using existing approaches are no longer needed when the one-pot approach is used. Because the stepwise PEG synthesis usually requires multiple PEG elongation cycles, the new PEG synthesis
  • reaction to carry out the deprotonation and Williamson ether formation reactions under basic conditions (Scheme 1) [15][16][18][23][25]. It is remarkable that the method has evolved to such a sophistication that the synthesis of (PEG)16 was achieved in nine steps without any chromatography [18][27
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Published 28 Dec 2021

DABCO-promoted photocatalytic C–H functionalization of aldehydes

  • Bruno Maia da Silva Santos,
  • Mariana dos Santos Dupim,
  • Cauê Paula de Souza,
  • Thiago Messias Cardozo and
  • Fernanda Gadini Finelli

Beilstein J. Org. Chem. 2021, 17, 2959–2967, doi:10.3762/bjoc.17.205

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  • is reduced by the photocatalyst (PC−) after coordination to aryl bromide, promoting the turnover of organometallic and photoredox cycles. DABCO is regenerated via deprotonation by an inorganic base. We also investigated the mechanism operating when the reaction is performed in the absence of bicyclic
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Published 21 Dec 2021

Iron-catalyzed domino coupling reactions of π-systems

  • Austin Pounder and
  • William Tam

Beilstein J. Org. Chem. 2021, 17, 2848–2893, doi:10.3762/bjoc.17.196

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  • observed. The efficiency of the reaction seems to be dependent on the deprotonation of the α-position of the olefinic malonate species. The authors noted decarbonylated products were obtained when cyclohexane carboxaldehyde and pivaldehyde were applied, consistent with the stability of the generated acyl
  • radical intermediate 137. Subsequently, intramolecular cyclization of 137 generates radical intermediate 138 which then successively undergoes a SET of Fe(III) and deprotonation by t-BuO− to give the annulated product 133a and regenerates the Fe(II) active catalyst. In 2014, the Loh group reported an
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Published 07 Dec 2021

α-Ketol and α-iminol rearrangements in synthetic organic and biosynthetic reactions

  • Scott Benz and
  • Andrew S. Murkin

Beilstein J. Org. Chem. 2021, 17, 2570–2584, doi:10.3762/bjoc.17.172

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  • similarity in reaction, 1-deoxy-ᴅ-xylulose-5-phosphate reductoisomerase (DXR) instead uses a retro-aldol/aldol sequence to accomplish its rearrangement of 68 to 69. c) The secondary metabolite aurachin C (71) is oxidized by the FAD-dependent monooxygenase AuaG to epoxide 72, which upon deprotonation by an
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Published 15 Oct 2021

Visible-light-mediated copper photocatalysis for organic syntheses

  • Yajing Zhang,
  • Qian Wang,
  • Zongsheng Yan,
  • Donglai Ma and
  • Yuguang Zheng

Beilstein J. Org. Chem. 2021, 17, 2520–2542, doi:10.3762/bjoc.17.169

Graphical Abstract
  • cation I and a CuI species. This process regenerated CuII in the presence of molecular oxygen. The deprotonation of the nitrogen radical cation produces an α–amino radical II, which was further oxidized to the iminium ion III to which the copper alkynylide added forming the desired product (Scheme 17
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Published 12 Oct 2021

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

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  • allylic functionalization of 2-alkylazaarenes. Due to the high pKa value of alkyl azaarenes, the functionalization of benzylic C(sp3)–H was challengeable and pre-activation of the benzylic proton with suitable Lewis acids was often required prior to deprotonation of the alkyl chain by a stoichiometric
  • MBH-derived allyl bromides (Scheme 1d) [30]. This reaction was assumed to involve the deprotonation of the initially formed 2-methylpyridinium salt by base to generate an N-allyl enamine intermediate, which undergoes a 3-aza-Cope rearrangement to give the allyl-substituted products. To the best of our
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Published 01 Oct 2021

Recent advances in the tandem annulation of 1,3-enynes to functionalized pyridine and pyrrole derivatives

  • Yi Liu,
  • Puying Luo,
  • Yang Fu,
  • Tianxin Hao,
  • Xuan Liu,
  • Qiuping Ding and
  • Yiyuan Peng

Beilstein J. Org. Chem. 2021, 17, 2462–2476, doi:10.3762/bjoc.17.163

Graphical Abstract
  • intramolecular nucleophilic attack by azide and the following deprotonation by a fluoride anion provide the final product 8 (Scheme 5). The derivatization of sulfonated aminonicotinates 8 could easily be achieved. Desulfonylation of aminonicotinate 8b proceeded smoothly in the presence of triflic acid (2.0 equiv
  • generate intermediate 20. Then, the intramolecular nucleophilic attack by azide and the following deprotonation give the final product 18 or 19, respectively. 5‑Selenyl- and 5-sulfenyl-substituted nicotinates can carry out versatile transformations, which have potential application in pharmaceutical
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Published 22 Sep 2021

Targeting active site residues and structural anchoring positions in terpene synthases

  • Anwei Hou and
  • Jeroen S. Dickschat

Beilstein J. Org. Chem. 2021, 17, 2441–2449, doi:10.3762/bjoc.17.161

Graphical Abstract
  • attack at (R)-A to form (R)-9, while the distance to the cation in (S)-A is too large, preventing its attack to form (S)-9. In contrast, the formation of 8 only requires deprotonation that seems to be possible for both intermediates (R)- and (S)-A, explaining why compound 8 is nearly racemic. As the
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Published 17 Sep 2021

Strategies for the synthesis of brevipolides

  • Yudhi D. Kurniawan and
  • A'liyatur Rosyidah

Beilstein J. Org. Chem. 2021, 17, 2399–2416, doi:10.3762/bjoc.17.157

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  • anti-addition of the sulfoxonium ylide to 52. Hou highlighted that the good diastereoselectivity control for the sulfoxonium ylide addition to acyclic α,β-unsaturated substrates such as 52 observed in their work represented the first example in literature. Hereupon, deprotonation of 53 over LiHMDS
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Published 14 Sep 2021

Advances in mercury(II)-salt-mediated cyclization reactions of unsaturated bonds

  • Sumana Mandal,
  • Raju D. Chaudhari and
  • Goutam Biswas

Beilstein J. Org. Chem. 2021, 17, 2348–2376, doi:10.3762/bjoc.17.153

Graphical Abstract
  • derivative 127. The plausible mechanism for the formation of compound 127 proceeded consecutively with π-complex formation, Friedel–Crafts type addition, deprotonation, and finally protonation of alcohol for the elimination of water to get the final product [92]. A Hg(OTf)2-mediated cyclization was utilized
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Published 09 Sep 2021

Base-free enantioselective SN2 alkylation of 2-oxindoles via bifunctional phase-transfer catalysis

  • Mili Litvajova,
  • Emiliano Sorrentino,
  • Brendan Twamley and
  • Stephen J. Connon

Beilstein J. Org. Chem. 2021, 17, 2287–2294, doi:10.3762/bjoc.17.146

Graphical Abstract
  • to the ability of squaramides to bind anionic species more strongly than ureas. The moderate enantiocontrol observed thus far prompted us to posit that the nitrogen atom on the quinoline moiety of the catalyst could participate to the deprotonation of 5a, therefore, leading to less selective
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Published 02 Sep 2021

Photoredox catalysis in nickel-catalyzed C–H functionalization

  • Lusina Mantry,
  • Rajaram Maayuri,
  • Vikash Kumar and
  • Parthasarathy Gandeepan

Beilstein J. Org. Chem. 2021, 17, 2209–2259, doi:10.3762/bjoc.17.143

Graphical Abstract
  • were found to be suitable to achieve the transformation in satisfactory yields under visible light irradiation (Scheme 2). The authors hypothesized that the key α-nitrogen carbon-centered radical 5 could be generated via a photoredox-driven N-phenyl oxidation and α-C–H deprotonation sequence from
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Published 31 Aug 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
  • receptor potential channels such as TRPM-7 [35]. In 2015, Murakami synthesized the novel indole C-2 borinic acid derivative 3 by reacting N-methylindole (1) with triisopropyl borate (2) in a strongly basic medium (Scheme 1). The product formation proceeds through the indole C-2 deprotonation mechanism [36
  • excess of the indole reactant. It is seen that in the presence of a base the C-2 deprotonation becomes very fast in 9 (for regaining aromaticity) so the boron at the initial C-3-borylated intermediate 8 (formed via SEAr) cannot migrate fast enough, leading to a C-3 borylation product 10a (unlike Pd) [38
  • ][39][40]. Here the absence of the base resulted in a slow or no C-2 deprotonation of 9, which in turn forces the boron to migrate to C-2 from C-3 (8, Scheme 2b) to result in the C-2 borylation (10b). Amines Bis(indolyl)amines have recently become important as organic electroluminescent materials [41
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Published 19 Aug 2021

Preparation of mono-substituted malonic acid half oxyesters (SMAHOs)

  • Tania Xavier,
  • Sylvie Condon,
  • Christophe Pichon,
  • Erwan Le Gall and
  • Marc Presset

Beilstein J. Org. Chem. 2021, 17, 2085–2094, doi:10.3762/bjoc.17.135

Graphical Abstract
  • affords the advantage of being based on commercially available malonates. We thus envisioned to achieve the alkylation step by deprotonation of a malonate with NaH followed by treatment with a halogenated compound. As our first attempts revealed a strong influence of the stoichiometry and the nature of
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Published 18 Aug 2021

Recent advances in the syntheses of anthracene derivatives

  • Giovanni S. Baviera and
  • Paulo M. Donate

Beilstein J. Org. Chem. 2021, 17, 2028–2050, doi:10.3762/bjoc.17.131

Graphical Abstract
  • -bifunctional organomagnesium alkoxide reagent 107, which converted esters into di- and monofunctionalized anthracenes (Scheme 25) [59]. They prepared this reagent by deprotonation–magnesiation of compound 106. Then, the treatment of aromatic esters with 107 produced dialkoxide 108, which could be easily
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Published 10 Aug 2021

Regioselective N-alkylation of the 1H-indazole scaffold; ring substituent and N-alkylating reagent effects on regioisomeric distribution

  • Ryan M. Alam and
  • John J. Keating

Beilstein J. Org. Chem. 2021, 17, 1939–1951, doi:10.3762/bjoc.17.127

Graphical Abstract
  • -1 alkylation of the exemplar methyl ester 9 and other appropriately C-3 substituted indazoles (19, or 21–24) (under conditions A, Table 1, entry 22) involves the initial irreversible deprotonation of the indazole in the presence of NaH to initially give indazolyl salt 65 which is in equilibrium with
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Published 02 Aug 2021

On the application of 3d metals for C–H activation toward bioactive compounds: The key step for the synthesis of silver bullets

  • Renato L. Carvalho,
  • Amanda S. de Miranda,
  • Mateus P. Nunes,
  • Roberto S. Gomes,
  • Guilherme A. M. Jardim and
  • Eufrânio N. da Silva Júnior

Beilstein J. Org. Chem. 2021, 17, 1849–1938, doi:10.3762/bjoc.17.126

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Published 30 Jul 2021

Sustainable manganese catalysis for late-stage C–H functionalization of bioactive structural motifs

  • Jongwoo Son

Beilstein J. Org. Chem. 2021, 17, 1733–1751, doi:10.3762/bjoc.17.122

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  • ). Manganaelectro-catalyzed late-stage azidation of bioactive molecules. Mn-catalyzed late-stage amination of bioactive molecules. a3 Å MS were used. Protonation with HBF4⋅OEt2 (1.1 equiv) in dichloromethane before amination, then deprotonation with 1 M NaOH in dichloromethane after amination. b3.0 equiv of PhI
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Published 26 Jul 2021

A recent overview on the synthesis of 1,4,5-trisubstituted 1,2,3-triazoles

  • Pezhman Shiri,
  • Ali Mohammad Amani and
  • Thomas Mayer-Gall

Beilstein J. Org. Chem. 2021, 17, 1600–1628, doi:10.3762/bjoc.17.114

Graphical Abstract
  • corresponding triazole products in moderate yield (Scheme 8) [42]. The authors proposed a reaction mechanism in which the β-thioenaminone 18 tolerates deprotonation to afford anionic intermediate 21 through the tautomer 20 in the presence of a base. In the next step, the nucleophilic addition of 21 to the azide
  • . Later, carboxylate-ligand-assisted C–H bond activation takes place through a concerted metalation–deprotonation transformation to produce the next intermediate. Finally, the corresponding product 142 is formed by a reductive elimination process, along with the regeneration of the active catalytic
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Published 13 Jul 2021

Copper-mediated oxidative C−H/N−H activations with alkynes by removable hydrazides

  • Feng Xiong,
  • Bo Li,
  • Chenrui Yang,
  • Liang Zou,
  • Wenbo Ma,
  • Linghui Gu,
  • Ruhuai Mei and
  • Lutz Ackermann

Beilstein J. Org. Chem. 2021, 17, 1591–1599, doi:10.3762/bjoc.17.113

Graphical Abstract
  • in terms of a concerted metalation deprotonation (CMD) mechanism [50]. Interestingly, electron-rich alkyne 2f displayed a higher reactivity in the copper-promoted C−H activations as compared to the electron-poor analog 2h (Scheme 4b). A significant H/D scrambling was not detected in the ortho
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Published 08 Jul 2021

One-step synthesis of imidazoles from Asmic (anisylsulfanylmethyl isocyanide)

  • Louis G. Mueller,
  • Allen Chao,
  • Embarek AlWedi and
  • Fraser F. Fleming

Beilstein J. Org. Chem. 2021, 17, 1499–1502, doi:10.3762/bjoc.17.106

Graphical Abstract
  • contain an adjacent electron withdrawing group (1, R1 = EWG) [13]. Installation of an electron withdrawing group adjacent to an isocyanide facilitates the deprotonation but creates weak nucleophiles 2 that are insufficiently nucleophilic to react with nitriles [14]. Described below is the use of Asmic
  • , anisylsulfanylmethylisocyanide (5) [15], whose deprotonation affords a potent nucleophile that reacts directly with nitriles to provide an efficient, general approach to an array of imidazoles; Asmic is a crystalline, virtually odorless isocyanide with the advantage over related methods [16][17] in being readily prepared in
  • fewer steps on at least 20 g scale [18], applicable for the synthesis of several heterocycles [19][20], and able to generate imidazoles from a broad array of nitrile and imidate electrophiles. Results and Discussion Exploratory deprotonation of Asmic (5) with BuLi followed by addition of butyronitrile
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Published 24 Jun 2021
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