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Search for "leaving group" in Full Text gives 251 result(s) in Beilstein Journal of Organic Chemistry. Showing first 200.

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

Graphical Abstract
  • products [3][4][5][6][7][8][9][10][11][12]. Most of the α-amidoalkylating reagents possess the structure of α-functionalized N-alkylamides 1, where Z = OH, OR, OCOR, Cl, Br, I, NHCOR, SO2Ar, 1-benzotriazolyl or PPh3+ X− and acts as a nucleofugal leaving group (Scheme 1) [3][8][9][10][13][14][15][16][17][18
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Published 24 Jul 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
  • by participation of the C2–OH group to release 1,3-dimethylimidazolidin-2-one (DMI), the anomeric leaving group. The epoxide is then opened by the nucleophile when added to the reaction mixture. In pathway C the α-DMC complex is displaced directly by the added nucleophile to liberate DMI, once again
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Published 27 Jun 2017

Synthesis of tetrasubstituted pyrazoles containing pyridinyl substituents

  • Josef Jansa,
  • Ramona Schmidt,
  • Ashenafi Damtew Mamuye,
  • Laura Castoldi,
  • Alexander Roller,
  • Vittorio Pace and
  • Wolfgang Holzer

Beilstein J. Org. Chem. 2017, 13, 895–902, doi:10.3762/bjoc.13.90

Graphical Abstract
  • [3,4-a]quinolizin-6-ium structure 12 was established, which was confirmed by single crystal X-ray structure analysis (see Supporting Information File 1), proving also iodide as the corresponding anion [39] which acts as a leaving group in the coupling reaction and also could origin from the CuI co
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Published 12 May 2017

DMAP-assisted sulfonylation as an efficient step for the methylation of primary amine motifs on solid support

  • Johnny N. Naoum,
  • Koushik Chandra,
  • Dorit Shemesh,
  • R. Benny Gerber,
  • Chaim Gilon and
  • Mattan Hurevich

Beilstein J. Org. Chem. 2017, 13, 806–816, doi:10.3762/bjoc.13.81

Graphical Abstract
  • effective reagent compared to the other additives used. DMAP is used as a catalyst in acylation reactions as it acts via a nucleophilic addition mechanism [34][37][40]. In nucleophilic catalysed acylation, the mechanism involves a step in which the DMAP replaces the leaving group on the carbonyl group
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Published 03 May 2017

Decarboxylative and dehydrative coupling of dienoic acids and pentadienyl alcohols to form 1,3,6,8-tetraenes

  • Ghina’a I. Abu Deiab,
  • Mohammed H. Al-Huniti,
  • I. F. Dempsey Hyatt,
  • Emma E. Nagy,
  • Kristen E. Gettys,
  • Sommayah S. Sayed,
  • Christine M. Joliat,
  • Paige E. Daniel,
  • Rupa M. Vummalaneni,
  • Andrew T. Morehead Jr,
  • Andrew L. Sargent and
  • Mitchell P. Croatt

Beilstein J. Org. Chem. 2017, 13, 384–392, doi:10.3762/bjoc.13.41

Graphical Abstract
  • and coupling this to a substrate with a benzylic or allylic leaving group [19][20]. Typical Pd(0)-catalyzed decarboxylative coupling reactions utilize an allylic or benzylic ester with either an anion-stabilizing group adjacent to the carboxyl group (i.e., carbonyl [19][21][22], nitrile [23][24][25
  • accessible alcohol for a leaving group. This reaction was advanced to be possible in a two-component fashion, allowing for the conversion of dienoic acids and pentadienyl alcohols into 1,3,6,8-tetraenes with the only stoichiometric byproducts being water and carbon dioxide. These reactions currently require
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Published 28 Feb 2017

Polyketide stereocontrol: a study in chemical biology

  • Kira J. Weissman

Beilstein J. Org. Chem. 2017, 13, 348–371, doi:10.3762/bjoc.13.39

Graphical Abstract
  • based on the crystal structure of the DEBS DH [92], in which the conserved His acts as a general base to deprotonate at C-2, while an Asp residue serves as a general acid to stabilize the C-3 hydroxy leaving group. However, only the His has been shown by site-directed mutagenesis to be essential [111
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Published 24 Feb 2017

Continuous N-alkylation reactions of amino alcohols using γ-Al2O3 and supercritical CO2: unexpected formation of cyclic ureas and urethanes by reaction with CO2

  • Emilia S. Streng,
  • Darren S. Lee,
  • Michael W. George and
  • Martyn Poliakoff

Beilstein J. Org. Chem. 2017, 13, 329–337, doi:10.3762/bjoc.13.36

Graphical Abstract
  • does not contain a “CO2 unit” that can serve as a leaving group. This was indeed the case as, at 250 °C, 85% selectivity, 70% yield for 16 was observed when the reaction was run in scCO2 (Scheme 3a). In the absence of CO2 as a solvent the formation of imidazolidinone 16 was not observed. When the
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Published 21 Feb 2017

Regiochemistry of cyclocondensation reactions in the synthesis of polyazaheterocycles

  • Patrick T. Campos,
  • Leticia V. Rodrigues,
  • Andrei L. Belladona,
  • Caroline R. Bender,
  • Juliana S. Bitencurt,
  • Fernanda A. Rosa,
  • Davi F. Back,
  • Helio G. Bonacorso,
  • Nilo Zanatta,
  • Clarissa P. Frizzo and
  • Marcos A. P. Martins

Beilstein J. Org. Chem. 2017, 13, 257–266, doi:10.3762/bjoc.13.29

Graphical Abstract
  • , followed by aromatization finally generates product 5 (Scheme 1). The trichloromethyl (CCl3) substituent as a leaving group in β-alkoxyvinyl trichloromethyl ketones has been previously used by us for the synthesis of similar heterocycles [27][28]. Products 5–7 are considered to be very attractive building
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Published 10 Feb 2017

Silyl-protective groups influencing the reactivity and selectivity in glycosylations

  • Mikael Bols and
  • Christian Marcus Pedersen

Beilstein J. Org. Chem. 2017, 13, 93–105, doi:10.3762/bjoc.13.12

Graphical Abstract
  • considerable reactivity difference between α- and β-thioglucosides was observed with the α-anomer consistently being more reactive. This suggested that the exact alignment of the leaving group is important for the reactivity, but a similar difference was not observed for other superarmed glycosyl donors
  • and with N-phenyltrifluoroacetimidate as the leaving group [57][58]. A somewhat similar influence has been observed with the much less steric demanding 4,6-O-benzylidene protective group [59]. A related stereoselectivity is induced by the DTBS group in arabinofuranosylations. Boons and collaborators
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Published 16 Jan 2017

Nucleophilic displacement reactions of 5′-derivatised nucleosides in a vibration ball mill

  • Olga Eguaogie,
  • Patrick F. Conlon,
  • Francesco Ravalico,
  • Jamie S. T. Sweet,
  • Thomas B. Elder,
  • Louis P. Conway,
  • Marc E. Lennon,
  • David R. W. Hodgson and
  • Joseph S. Vyle

Beilstein J. Org. Chem. 2017, 13, 87–92, doi:10.3762/bjoc.13.11

Graphical Abstract
  • and nucleoside substrate (e.g., the leaving group [11] or nucleobase protection [12]) are therefore often required. We anticipated that some of these issues could be ameliorated through mechanochemical mixing of reactants and substrates, with diverse solubility profiles, using minimal or no added
  • -dependency also observed with KSeCN under Finkelstein conditions [38]. Finally, our approach also offers the convenience of employing tosylate and halide precursors rather than relying on the esoteric tresylate leaving group system. Model reactions of 5′-chloro-5′-deoxyadenosine (1a) with 4
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Published 13 Jan 2017

O-Alkylated heavy atom carbohydrate probes for protein X-ray crystallography: Studies towards the synthesis of methyl 2-O-methyl-L-selenofucopyranoside

  • Roman Sommer,
  • Dirk Hauck,
  • Annabelle Varrot,
  • Anne Imberty,
  • Markus Künzler and
  • Alexander Titz

Beilstein J. Org. Chem. 2016, 12, 2828–2833, doi:10.3762/bjoc.12.282

Graphical Abstract
  • derivatives are nowadays used as powerful tools in organic chemistry [6]. Synthetic selenoglycosides are versatile synthons in glycosylation reactions as glycosyl donors for the synthesis of glycosides and oligosaccharides, where their aglycon acts as a leaving group [7][8][9]. They can be selectively
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Published 22 Dec 2016

Selective synthesis of thioethers in the presence of a transition-metal-free solid Lewis acid

  • Federica Santoro,
  • Matteo Mariani,
  • Federica Zaccheria,
  • Rinaldo Psaro and
  • Nicoletta Ravasio

Beilstein J. Org. Chem. 2016, 12, 2627–2635, doi:10.3762/bjoc.12.259

Graphical Abstract
  • the green chemistry point of view would be the direct substitution of alcohols (that are also available at low cost) with thiols. In this case the only byproduct will be water. However, due to the lack of a good leaving group the use of an acid catalyst is mandatory. Both Brønsted and Lewis acids can
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Published 06 Dec 2016

Facile synthesis of a 3-deazaadenosine phosphoramidite for RNA solid-phase synthesis

  • Elisabeth Mairhofer,
  • Elisabeth Fuchs and
  • Ronald Micura

Beilstein J. Org. Chem. 2016, 12, 2556–2562, doi:10.3762/bjoc.12.250

Graphical Abstract
  • plays a dominant role in catalysis [3][4][5]. Also for the pistol ribozyme, evidence exists that an adenine-N3 in the active site is significant for the cleavage activity, most likely by 5’-O-leaving group stabilization through proton shuttling [6][7]. Another example for a specific role of an adenine
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Published 28 Nov 2016

Et3B-mediated and palladium-catalyzed direct allylation of β-dicarbonyl compounds with Morita–Baylis–Hillman alcohols

  • Ahlem Abidi,
  • Yosra Oueslati and
  • Farhat Rezgui

Beilstein J. Org. Chem. 2016, 12, 2402–2409, doi:10.3762/bjoc.12.234

Graphical Abstract
  • reaction, is a non-toxic byproduct. However, the poor ability of the hydroxy moiety, as a leaving group, has limited the use of the allyl alcohols as substrates. Correlatively, some efforts have been made in this direction by the use of transition metals such as copper [6], nickel [7], ruthenium (I, II) [8
  • to catalyze these reactions by coordination with the hydroxy moiety, thereby increasing its leaving group ability [23][24][25][26][27][28]. Recently, Tamaru and co-workers have intensively investigated the use of triethylborane as an additive with either Pd(PPh3)4 or Pd(OAc)2 as catalysts for the
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Published 15 Nov 2016

Efficient mechanochemical synthesis of regioselective persubstituted cyclodextrins

  • Laszlo Jicsinszky,
  • Marina Caporaso,
  • Katia Martina,
  • Emanuela Calcio Gaudino and
  • Giancarlo Cravotto

Beilstein J. Org. Chem. 2016, 12, 2364–2371, doi:10.3762/bjoc.12.230

Graphical Abstract
  • , which is an important component of DNA sequencing equipment [4]. p-Toluenesulfonyl (Ts) esters are still an irreplaceable leaving group for carbohydrates as well. The Ts → azide exchange in Ts-β-CD is effective in both solution and under high-energy ball milling (HEBM) conditions, whereas it is
  • /halogen molar ratios did not change such extent (Table 1). This can be explained satisfactorily by the complexation of the leaving group which might have high affinity to the CD cavity [3][25][26] preventing its departure from the reaction centres resulting in steric blocking. While the halogen → azide
  • optimized the prepared compounds were enough pure to record correct NMR spectra to identify the substitution location and completeness. Although in the monosubstituted case usually less reagent/leaving group molar ratios were found [22], in the majority of per-substitutions higher reagent/CD molar ratio was
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Published 10 Nov 2016

Rearrangements of organic peroxides and related processes

  • Ivan A. Yaremenko,
  • Vera A. Vil’,
  • Dmitry V. Demchuk and
  • Alexander O. Terent’ev

Beilstein J. Org. Chem. 2016, 12, 1647–1748, doi:10.3762/bjoc.12.162

Graphical Abstract
  • a good leaving group. The Criegee rearrangement was discovered in 1944 in the reaction of decaline ethylperoxoate 127 that rearranged into isomeric ester ketal 128 (Scheme 39) [291]. The mechanism of the Criegee rearrangement was studied using 2-alkoxy-2-propyl per-4-nitrobenzoates [292]. It was
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Published 03 Aug 2016

Flow carbonylation of sterically hindered ortho-substituted iodoarenes

  • Carl J. Mallia,
  • Gary C. Walter and
  • Ian R. Baxendale

Beilstein J. Org. Chem. 2016, 12, 1503–1511, doi:10.3762/bjoc.12.147

Graphical Abstract
  • yields of the array were obtained for compounds 29 and 30, demonstrating the importance of sterics and electronics adjacent to the leaving group. In both cases, the carbon monoxide insertion is assumed to be slow as both axial positions of the aryl complex would be hindered, meaning the competing proton
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Published 19 Jul 2016

The hydrolysis of geminal ethers: a kinetic appraisal of orthoesters and ketals

  • Sonia L. Repetto,
  • James F. Costello,
  • Craig P. Butts,
  • Joseph K. W. Lam and
  • Norman M. Ratcliffe

Beilstein J. Org. Chem. 2016, 12, 1467–1475, doi:10.3762/bjoc.12.143

Graphical Abstract
  • former affords a leaving group covalently tethered to a cation which renders the overall rate apparently slow, perhaps through a favoured re-cyclisation. It is noteworthy that the hydroxonium catalytic coefficient for the hydrolysis – albeit measured in water – of a similar yet acyclic ketal (i.e., 2,2
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Published 15 Jul 2016

Mutagenic activity of quaternary ammonium salt derivatives of carbohydrates

  • Barbara Dmochowska,
  • Karol Sikora,
  • Anna Woziwodzka,
  • Jacek Piosik and
  • Beata Podgórska

Beilstein J. Org. Chem. 2016, 12, 1434–1439, doi:10.3762/bjoc.12.138

Graphical Abstract
  • methanol, an alternative route involving the reaction of 6-bromohexyl D-glucopyranoside (2′ [32] or 3′) with tertiary amines (trimethylamine in ethanol and with pyridine) was applied; the yields were of 90–94%. Shifting the pyranose leaving group (halogen) by six carbon atoms from C1 makes it easier to
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Published 12 Jul 2016

Unconventional application of the Mitsunobu reaction: Selective flavonolignan dehydration yielding hydnocarpins

  • Guozheng Huang,
  • Simon Schramm,
  • Jörg Heilmann,
  • David Biedermann,
  • Vladimír Křen and
  • Michael Decker

Beilstein J. Org. Chem. 2016, 12, 662–669, doi:10.3762/bjoc.12.66

Graphical Abstract
  • Mitsunobu reaction represents a powerful method to convert primary and secondary alcohols into ester but also into various derivatives. The mechanism is well described and includes the formation of the triphenylphosphine–DIAD adduct, which then activates the alcohol making it a good leaving group
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Published 08 Apr 2016

Studies on the synthesis of peptides containing dehydrovaline and dehydroisoleucine based on copper-mediated enamide formation

  • Franziska Gille and
  • Andreas Kirschning

Beilstein J. Org. Chem. 2016, 12, 564–570, doi:10.3762/bjoc.12.55

Graphical Abstract
  • typically this is achieved by elimination when a leaving group occupies the β-position [2]. Especially peptides containing dehydroalanine as found in argyrin (2) can be prepared from a precursor that contains a selenide substituent in the β-position [3]. Peptides that bear the doubly branched dehydroamino
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Published 22 Mar 2016

(Thio)urea-mediated synthesis of functionalized six-membered rings with multiple chiral centers

  • Giorgos Koutoulogenis,
  • Nikolaos Kaplaneris and
  • Christoforos G. Kokotos

Beilstein J. Org. Chem. 2016, 12, 462–495, doi:10.3762/bjoc.12.48

Graphical Abstract
  • values the nature of R3 is very important. The better the leaving group R3 is, the higher the values of the ee. It is mentioned that the ee in this reaction is up to 96%, and the recommended R3 group to be used is 3,4,5-trifluorobenzyl. The use of the bifunctional amine-thiourea catalyst 27, into a
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Published 10 Mar 2016

Recent advances in N-heterocyclic carbene (NHC)-catalysed benzoin reactions

  • Rajeev S. Menon,
  • Akkattu T. Biju and
  • Vijay Nair

Beilstein J. Org. Chem. 2016, 12, 444–461, doi:10.3762/bjoc.12.47

Graphical Abstract
  • nucleophile and then as a leaving group in cyanide-catalysed benzoin reactions [8]. Analogously, Breslow invoked the generation of a nucleophilic thiazolylidene species 1 via deprotonation of the thiazolium salt by base. The ylide 1 may also be represented as its resonance structure 1’ (carbene). Nucleophilic
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Published 09 Mar 2016

Dynamic behavior of rearranging carbocations – implications for terpene biosynthesis

  • Stephanie R. Hare and
  • Dean J. Tantillo

Beilstein J. Org. Chem. 2016, 12, 377–390, doi:10.3762/bjoc.12.41

Graphical Abstract
  • solvolysis of syn- and anti-norborn-2-en-7-ylmethyl-X diastereomers (Is and Ia, Figure 6; X is a leaving group) both led to the same two products, but in different ratios, despite sharing a common intermediate (in different conformations; V, Figure 6) [59]. The major product generated from the solvolysis of
  • magnitude varied with leaving group identity) was ascribed to a “memory effect”. Put simply, product ratios were skewed from what would be expected by simply comparing activation barriers, because the reacting molecule “remembers” the conformation from which it came; this is a hallmark of dynamic matching
  • in order to make the products; consequently, dynamics trajectories were initiated from the regions of these TSSs (using a lower level of theory so that 250 trajectories from each transition state could be obtained in a reasonable amount of time; the influence of the leaving group on dynamical
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Published 29 Feb 2016

Enabling technologies and green processes in cyclodextrin chemistry

  • Giancarlo Cravotto,
  • Marina Caporaso,
  • Laszlo Jicsinszky and
  • Katia Martina

Beilstein J. Org. Chem. 2016, 12, 278–294, doi:10.3762/bjoc.12.30

Graphical Abstract
  • molecule and reagent or between host and guest in cases 1) and, usually, 2), reaction type 3) requires a CD derivative that bears a good leaving group and the complexation phenomenon can be disadvantageous here. While type 1) can eliminate usually the less problematic solvents only, the application of BM
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Published 15 Feb 2016
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