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21 article(s) from Slawin, Alexandra M Z

NHC-catalyzed enantioselective synthesis of β-trifluoromethyl-β-hydroxyamides

Alyn T. Davies,
Mark D. Greenhalgh,
Alexandra M. Z. Slawin and
Andrew D. Smith

Letter
Published 30 Jun 2020

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1. Graphical Abstract
2. Figure 1: Organocatalytic enantioselective aldol approaches using trifluoroacetophenone derivatives.
  
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3. Figure 2: NHC-catalyzed approaches to β-lactones using trifluoroacetophenone derivatives.
  
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4. Scheme 1: Reaction scope with respect to the nucleophile. ^aIsolated yield of the product in >95:5 dr. ^bDeterm...
  
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5. Scheme 2: Reaction scope with respect to the trifluoroacetophenone derivative and α-aroyloxyaldehyde. ^aIsolat...
  
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6. Scheme 3: Proposed mechanism.
  
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Beilstein J. Org. Chem. 2020, 16, 1572–1578, doi:10.3762/bjoc.16.129

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Synthesis of organic liquid crystals containing selectively fluorinated cyclopropanes

Zeguo Fang,
Nawaf Al-Maharik,
Peer Kirsch,
Matthias Bremer,
Alexandra M. Z. Slawin and
David O’Hagan

Full Research Paper
Published 14 Apr 2020

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1. Graphical Abstract
2. Figure 1: Examples of liquid crystal candidates with negative values for dielectric anisotropy (Δε) [6-10].
  
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3. Figure 2: Synthetic candidate LC targets 8–11.
  
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4. Scheme 1: Synthesis of 8. Reagents and conditions: a) TMSCF₃, NaI, THF, reflux, 55% [13,14].
  
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5. Scheme 2: Synthesis of 9. Reagents and conditions: a) NBS, HF·Py, DCM; b) t-BuOK, DCM, 42% in two steps [15]; c) ...
  
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6. Scheme 3: Synthesis of compound 10. Reagents and conditions: a) NaBH₄, MeOH, rt, 45%; b) C₄H₉OCH=CH₂, Pd(TFA)₂...
  
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7. Scheme 4: Synthesis of compounds 11. Reagents and conditions: a) PPh₃CH₃Br, t-BuOK, diethyl ether, 0 °C to rt...
  
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8. Figure 3: Theory study exploring the relative energies for different conformers of 11a.
  
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Beilstein J. Org. Chem. 2020, 16, 674–680, doi:10.3762/bjoc.16.65

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Aerobic synthesis of N-sulfonylamidines mediated by N-heterocyclic carbene copper(I) catalysts

Faïma Lazreg,
Marie Vasseur,
Alexandra M. Z. Slawin and
Catherine S. J. Cazin

Full Research Paper
Published 24 Mar 2020

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1. Graphical Abstract
2. Scheme 1: Formation of sulfonyltriazoles and sulfonamidines.
  
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3. Figure 1: Catalytic systems used in this study.
  
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4. Scheme 2: Synthetic access to complexes 4–6 [30].
  
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5. Scheme 3: Variation of sulfonylazides. Reaction conditions: phenylacetylene (0.5 mmol), sulfonyl azide (0.6 m...
  
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6. Scheme 4: Variation of alkynes. Reaction conditions: alkyne (0.5 mmol), tosyl azide (0.6 mmol), diisopropylam...
  
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7. Scheme 5: Variation of the amine substrate. Reaction conditions: phenylacetylene (0.5 mmol), tosyl azide (0.6...
  
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8. Scheme 6: Reactivity of “non-sulfonyl” azide [33]. Reaction conditions: phenylacetylene (0.5 mmol), benzyl azide ...
  
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9. Scheme 7: Reactivity of diphenylphosphoryl azide. Reaction conditions: phenylacetylene (0.5 mmol), diphenylph...
  
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10. Scheme 8: Proposed mechanism for the formation of sulfonamidine.
  
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11. Scheme 9: Stoichiometric reaction between 6 and 8.
  
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12. Scheme 10: Synthesis of copper-acetylide intermediate A via [Cu(Cl)(Triaz)].
  
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13. Scheme 11: Catalytic reaction involving copper-acetylide complex A.
  
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Beilstein J. Org. Chem. 2020, 16, 482–491, doi:10.3762/bjoc.16.43

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Fluorine-containing substituents: metabolism of the α,α-difluoroethyl thioether motif

Andrea Rodil,
Alexandra M. Z. Slawin,
Nawaf Al-Maharik,
Ren Tomita and
David O’Hagan

Full Research Paper
Published 28 Jun 2019

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1. Graphical Abstract
2. Figure 1: Structures of trifluoromethyl sulfonyl ether bioactives.
  
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3. Figure 2: Comparison of log P values of comparative aryl thioether motifs [18].
  
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4. Figure 3: α,α-Difluoroethyl thioether substrates for metabolism studies.
  
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5. Scheme 1: Fluorometabolites 6–8 isolated after incubation of 4 with C. elegans. Ratios are the average of thr...
  
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6. Scheme 2: Putative pathways for (α,α-difluoroethyl)(4-methoxyphenyl)sulfane (4) metabolism.
  
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7. Scheme 3: C. elegans incubation of 5. Ratios are the average of three incubations.
  
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8. Scheme 4: Incubation (four times) of oxygen ether 14 with C. elegans, gave 4-acetoxyphenol (15) as the major ...
  
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Beilstein J. Org. Chem. 2019, 15, 1441–1447, doi:10.3762/bjoc.15.144

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Fluorinated cyclohexanes: Synthesis of amine building blocks of the all-cis 2,3,5,6-tetrafluorocyclohexylamine motif

Tetiana Bykova,
Nawaf Al-Maharik,
Alexandra M. Z. Slawin and
David O'Hagan

Full Research Paper
Published 19 Apr 2017

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1. Graphical Abstract
2. Figure 1: The derivatives of all-cis-2,3,5,6-tetrafluorocyclohexane.
  
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3. Scheme 1: Reagents and conditions: a) Li (2.5 equiv), NH₃, t-BuOH (1 equiv), MeI (2 equiv), 3 h, −78 °C, 18 h...
  
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4. Scheme 2: Reagents and conditions: a) Et₃N·3HF (8 equiv), 18 h, 140 °C; b) Tf₂O (4 equiv), pyridine, 1 h, 0 °...
  
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5. Scheme 3: Reagents and conditions: a) Et₃N·3HF (8 equiv), 18 h, 140 °C; b) Tf₂O (4 equiv), pyridine, 1 h, 0 °...
  
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6. Scheme 4: Reagents and conditions: a) terephthaloyl chloride (1 equiv), Et₃N (4 equiv), DMAP (20 mol %), DCM,...
  
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7. Figure 2: X-ray structures and crystal packing of compounds 13, 14 and 15.
  
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Beilstein J. Org. Chem. 2017, 13, 728–733, doi:10.3762/bjoc.13.72

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Organofluorine chemistry: Difluoromethylene motifs spaced 1,3 to each other imparts facial polarity to a cyclohexane ring

Mathew J. Jones,
Ricardo Callejo,
Alexandra M. Z. Slawin,
Michael Bühl and
David O'Hagan

Full Research Paper
Published 22 Dec 2016

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1. Graphical Abstract
2. Figure 1: Selected fluorinated polar alicyclic scaffolds.
  
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3. Scheme 1: Retrosynthetic plan to the preparation of 1,1,3,3-tetrafluorocyclohexane structures.
  
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4. Scheme 2: Preparation of starting materials 5c and 6a–c.
  
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5. Scheme 3: Deoxofluorination of diketones 5. Reagents and conditions: a) DAST, DCM, rt, overnight, 4a (traces)...
  
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6. Scheme 4: Fluorodesulfurisation of bis-dithianes 6. Reagents and conditions: a) NIS, HF·Py, DCM, −78 °C to rt...
  
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7. Figure 2: X-ray structure of compound 4c. The image shows two molecules stacked with the non-fluorine face po...
  
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8. Figure 3: ¹H NMR spectra of 4c. A) shows the spectrum in [²H₈]-toluene, and B) shows the spectrum in chlorofo...
  
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9. Figure 4: Electrostatic potential map for 4c calculated at the B3LYP/6-311G(d,p) level for an optimised struc...
  
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Beilstein J. Org. Chem. 2016, 12, 2823–2827, doi:10.3762/bjoc.12.281

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Selectively fluorinated cyclohexane building blocks: Derivatives of carbonylated all-cis-3-phenyl-1,2,4,5-tetrafluorocyclohexane

Mohammed Salah Ayoup,
David B. Cordes,
Alexandra M. Z. Slawin and
David O'Hagan

Full Research Paper
Published 21 Dec 2015

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1. Graphical Abstract
2. Figure 1: All cis-hexafluoro- 1 and tetrafluorocyclohexanes 2 and 3 result in facially polarised ring motifs ...
  
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3. Scheme 1: Preparation of benzoic acids 11–13; i. HIO₄·2H₂O (50%), AcOH, H₂SO₄, I₂, H₂O, 70 °C 24 h, 92%.; ii....
  
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4. Scheme 2: Synthesis of benzaldehyde derivatives 14 and 15: i. Pd(PPh₃)₄, Bu₃SnH, THF, CO (1 atm), 50 °C, 2–3 ...
  
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5. Figure 2: X-ray structure of aldehyde 15. CCDC number 1432193.
  
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6. Scheme 3: Olefination reactions of 15 and the X-ray structure of 17 (CCDC number 1432194): i. Zn, TiCl₄, THF,...
  
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7. Scheme 4: Reactions from aldehyde 15: i. NaBH₄, THF, 20 °C, 1 h, 98%.; ii. HI (57%), CHCl₃, 30 h, 95%; iii. Bu...
  
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8. Scheme 5: Reactions of benzyl azide 21; i. 24, Cu(OAc)₂, Na ascorbate, t-BuOH, H₂O, 20 °C, 16 h, 72%; ii. HCl...
  
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9. Scheme 6: Reactions of aldehyde 14: i. NaBH₄, THF, rt, 1 h, 98%.; ii. HI (57%), CHCl₃, 30 h, 94%; iii. Bu₄NN₃...
  
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Beilstein J. Org. Chem. 2015, 11, 2671–2676, doi:10.3762/bjoc.11.287

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Ruthenium indenylidene “1^st generation” olefin metathesis catalysts containing triisopropyl phosphite

Stefano Guidone,
Fady Nahra,
Alexandra M. Z. Slawin and
Catherine S. J. Cazin

Full Research Paper
Published 01 Sep 2015

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1. Graphical Abstract
2. Figure 1: Examples of ruthenium complexes used in olefin metathesis reactions.
  
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3. Scheme 1: Synthesis of the mixed phosphine/phosphite complex 1.
  
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4. Figure 2: Molecular structure of mixed phosphine/phosphite complex 1. Hydrogen atoms are omitted for clarity.
  
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5. Scheme 2: Synthesis of the bis-phosphite complex 2.
  
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6. Figure 3: Molecular structure of 2 and the ylide 3. Hydrogen atoms and solvent molecules are omitted for clar...
  
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7. Figure 4: Reaction profiles of mixed phosphine/phosphite 1 and phosphine-based Ind-I in the RCM of 4 (lines a...
  
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Beilstein J. Org. Chem. 2015, 11, 1520–1527, doi:10.3762/bjoc.11.166

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Pyridine-promoted dediazoniation of aryldiazonium tetrafluoroborates: Application to the synthesis of SF₅-substituted phenylboronic esters and iodobenzenes

George Iakobson,
Junyi Du,
Alexandra M. Z. Slawin and
Petr Beier

Full Research Paper
Published 26 Aug 2015

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1. Graphical Abstract
2. Scheme 1: Borylation of aryldiazonium tetrafluoroborates 3. Reaction conditions: 3 (1 mmol), B₂pin₂ (1 mmol),...
  
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3. Scheme 2: Proposed reaction mechanism.
  
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4. Scheme 3: Reaction of diazonium salt 3i under borylation conditions.
  
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5. Scheme 4: Suzuki–Miyaura reaction of boronates 2a and 2b with aryl iodides. Reaction conditions: 2 (1 mmol), ...
  
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6. Scheme 5: Syntesis of boronic acid 8b and trifluoroborates 9. Reaction conditions for the synthesis of 8b: 2 ...
  
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7. Scheme 6: Iodination of aryldiazonium tetrafluoroborates 3. Reaction conditions: 3 (1 mmol), I₂ (1.1 mmol), p...
  
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Beilstein J. Org. Chem. 2015, 11, 1494–1502, doi:10.3762/bjoc.11.162

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The difluoromethylene (CF₂) group in aliphatic chains: Synthesis and conformational preference of palmitic acids and nonadecane containing CF₂ groups

Yi Wang,
Ricardo Callejo,
Alexandra M. Z. Slawin and
David O’Hagan

Full Research Paper
Published 06 Jan 2014

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1. Graphical Abstract
2. Figure 1: The CF₂ group in 1c accelerates RCM reactions relative to CHF (1d) and CH₂ (1e) and with a similar ...
  
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3. Figure 2: X-ray structures of a) 1,1,4,4- (3) b) 1,1,7,7- (4) and c) 1,1,6,6- (5) tetrafluorocyclododecanes. ...
  
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4. Figure 3: Synthesis targets: Palmitic acid analogues 6a–c.
  
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5. Scheme 1: Synthesis route to 8,8-difluorohexadecanoic acid (6a).
  
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6. Scheme 2: The synthesis of palmitic acid analogues 6b and 6c.
  
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7. Figure 4: DSC traces for the three palmitic acid analogues 6a–c.
  
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8. Figure 5: The X-ray crystal structures of 8,8-difluorohexadecanoic acid (6a).
  
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9. Figure 6: The X-ray structure of 8,8,11,11-tetrafluorohexadecanoic acid (6c).
  
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10. Scheme 3: Synthesis route to the tetrafluorinated alkane 27.
  
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11. Figure 7: The X-ray structure of 8,8,11,11-tetrafluorononadecane (27).
  
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12. Figure 8: Conformational interconversion of 1,4-di-CF₂ motif.
  
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Beilstein J. Org. Chem. 2014, 10, 18–25, doi:10.3762/bjoc.10.4

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Synthesis, characterization and luminescence studies of gold(I)–NHC amide complexes

Adrián Gómez-Suárez,
David J. Nelson,
David G. Thompson,
David B. Cordes,
Duncan Graham,
Alexandra M. Z. Slawin and
Steven P. Nolan

Full Research Paper
Published 28 Oct 2013

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1. Graphical Abstract
2. Scheme 1: Straightforward synthesis of organogold complexes via deprotonation reactions, using 1.
  
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3. Scheme 2: Scope of the reaction between 1 and several (hetero)aromatic amines. Reaction conditions: 1 (1 equi...
  
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4. Figure 1: X-ray crystal structures of complexes 2, 3, 7, 8, 10, 11 and 12. Hydrogen atoms are omitted for cla...
  
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5. Figure 2: Selected examples of gold–NHC amide complexes under UV light (λ = 366 nm).
  
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6. Figure 3: Excitation (blue) and emission (pink) data for complex 3, bearing a 2-pyridine ligand (see inset).
  
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7. Figure 4: (a) LUMO, (b) HOMO and (c) HOMO-1 of complex 3.
  
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Beilstein J. Org. Chem. 2013, 9, 2216–2223, doi:10.3762/bjoc.9.260

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Extending the utility of [Pd(NHC)(cinnamyl)Cl] precatalysts: Direct arylation of heterocycles

Anthony R. Martin,
Anthony Chartoire,
Alexandra M. Z. Slawin and
Steven P. Nolan

Full Research Paper
Published 27 Sep 2012

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1. Graphical Abstract
2. Figure 1: [Pd(NHC)(cin)Cl] catalysts examined in direct arylation.
  
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3. Scheme 1: Synthesis of [Pd(IPr*^Tol)(cin)Cl] (4).
  
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4. Figure 2: Molecular structure of 4. H atoms were omitted for clarity. Selected bond lengths (Å) and angles (°...
  
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5. Figure 3: Previously reported catalytic systems in the direct arylation of benzothiophene (6).
  
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Beilstein J. Org. Chem. 2012, 8, 1637–1643, doi:10.3762/bjoc.8.187

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The preferred conformation of erythro- and threo-1,2-difluorocyclododecanes

Yi Wang,
Peer Kirsch,
Tomas Lebl,
Alexandra M. Z. Slawin and
David O'Hagan

Full Research Paper
Published 10 Aug 2012

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1. Graphical Abstract
2. Figure 1: The Dunitz and Shearer structure of cyclododecane (1) [1,2]. There are four endo hydrogens above and fou...
  
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3. Figure 2: Crystal structures of (a) 1,1,4,4- (b) 1,1,7,7- and (c) 1,1,6,6-tetrafluorocyclododecanes (2–4) , i...
  
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4. Figure 3: Erythro- and threo-1,2-difluorocyclododecanes (5a and 5b).
  
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5. Scheme 1: Synthetic routes to erythro- (5a) and threo-1,2-difluorocyclododecane (5b).
  
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6. Figure 4: X-ray crystal structure of threo-1,2-difluorocyclododecane (5b) showing corner angles and represent...
  
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7. Figure 5: Variable-temperature ¹⁹F{¹H} NMR of erythro- (5a) and threo-1,2-difluorocyclododecane (5b).
  
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8. Figure 6: Calculated relative energies of the conformations of the erythro (5a) and threo (5b) stereoisomers ...
  
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Beilstein J. Org. Chem. 2012, 8, 1271–1278, doi:10.3762/bjoc.8.143

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The role of silver additives in gold-mediated C–H functionalisation

Scott R. Patrick,
Ine I. F. Boogaerts,
Sylvain Gaillard,
Alexandra M. Z. Slawin and
Steven P. Nolan

Full Research Paper
Published 01 Jul 2011

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1. Graphical Abstract
2. Scheme 1: Silver-free C–H functionalisation using [Au(OH)(IPr)].
  
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3. Scheme 2: C–H functionalisation of 2 using gold-phosphine complexes and a silver additive.
  
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4. Figure 1: X-ray structure of [Au(OPiv)(IPr)] 3. Thermal ellipsoids are shown at the 50% probability level. H ...
  
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5. Scheme 3: Carboxylation of 2 using 1 and Ag₂O.
  
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Beilstein J. Org. Chem. 2011, 7, 892–896, doi:10.3762/bjoc.7.102

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Single enantiomer synthesis of α-(trifluoromethyl)-β-lactam

Václav Jurčík,
Alexandra M. Z. Slawin and
David O'Hagan

Full Research Paper
Published 06 Jun 2011

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1. Graphical Abstract
2. Figure 1: Enantiomers of α-(trifluoromethyl)-β-lactam (1).
  
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3. Scheme 1: Synthetic route involving a diastereoisomeric separation to α-(trifluoromethyl)-β-lactam ((S)-1) fr...
  
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4. Figure 2: X-ray structures of (a) β-lactam (S)-1 and (b) (αR,3R)-5c. (a) Determination of the absolute stereo...
  
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5. Scheme 2: Synthesis of stereoisomers 5c. The stereochemistry of the major isomer (αR,3R)-5c was solved by X-r...
  
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Beilstein J. Org. Chem. 2011, 7, 759–766, doi:10.3762/bjoc.7.86

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Backbone tuning in indenylidene–ruthenium complexes bearing an unsaturated N-heterocyclic carbene

César A. Urbina-Blanco,
Xavier Bantreil,
Hervé Clavier,
Alexandra M. Z. Slawin and
Steven P. Nolan

Full Research Paper
Published 23 Nov 2010

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1. Graphical Abstract
2. Figure 1: Representative olefin metathesis catalysts.
  
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3. Figure 2: Highly active olefin metathesis catalysts bearing NHC with backbone substitution.
  
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4. Scheme 1: Synthesis of the free NHCs.
  
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5. Scheme 2: Synthesis of [RhCl(CO)₂(NHC)] complexes.
  
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6. Scheme 3: Synthesis of [RuCl₂(NHC)(PCy₃)(Ind)] complexes.
  
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Beilstein J. Org. Chem. 2010, 6, 1120–1126, doi:10.3762/bjoc.6.128

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Prins fluorination cyclisations: Preparation of 4-fluoro-pyran and -piperidine heterocycles

Guillaume G. Launay,
Alexandra M. Z. Slawin and
David O'Hagan

Full Research Paper
Published 26 Apr 2010

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1. Graphical Abstract
2. Scheme 1: The C–F bond forming Prins reaction leading to 4-fluoropyrans [10].
  
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3. Figure 1: X-ray crystal structure of syn-5a.
  
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4. Scheme 2: Ring opening hydrogenation of an oxa-Prins product.
  
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5. Figure 2: X-ray crystal structure of the major bicyclic tetrahydropyran diastereoisomer 9b.
  
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6. Scheme 3: Reaction using (E)-11a and (Z)-11b hex-3-en-1-ols with 4-nitrobenzaldehyde to generate 4-fluorotetr...
  
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7. Figure 3: X-ray crystal structure of the minor anti-piperidine product 14d.
  
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Beilstein J. Org. Chem. 2010, 6, No. 41, doi:10.3762/bjoc.6.41

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Three step synthesis of single diastereoisomers of the vicinal trifluoro motif

Vincent A. Brunet,
Alexandra M. Z. Slawin and
David O'Hagan

Full Research Paper
Published 05 Nov 2009

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1. Graphical Abstract
2. Scheme 1: Previous six step route to the vicinal all-syn-trifluoro motif.
  
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3. Scheme 2: Novel three step successive fluorination strategy from α,β-epoxy alcohols to different diastereoiso...
  
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4. Scheme 3: Synthesis approach to the requisite α,β-epoxy alcohols 6b and 7b.
  
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5. Figure 1: X-ray structure (CCDC 750307) and stereochemistry of α,β-epoxy alcohol 7b.
  
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6. Figure 2: X-ray structure (CCDC 750306) and stereochemistry of α,β-epoxy alcohol 7a.
  
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7. Scheme 4: Three step sequential fluorination from α,β-epoxy alcohols to eg. the vicinyltrifluoro tosylate 11.
  
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8. Scheme 5: Unexpected cyclisation of 9b to furan 14 with HF·pyridine. An X-ray structure of 14 (CCDC 750309) r...
  
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9. Scheme 6: Epoxide ring opening of 9b with 3HF·Et₃N required forcing conditions. The structure and stereochemi...
  
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10. Scheme 7: Three step sequential fluorination from α,β-epoxy alcohol 7b to vicinal trifluoro tosylate 17b.
  
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11. Scheme 8: Epoxide ring opening with 3HF∙Et₃N and synthesis of the all-syn vicinal trifluoro tosylate 17a.
  
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Beilstein J. Org. Chem. 2009, 5, No. 61, doi:10.3762/bjoc.5.61

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Synthesis of phosphonate and phostone analogues of ribose-1-phosphates

Pitak Nasomjai,
David O'Hagan and
Alexandra M. Z. Slawin

Full Research Paper
Published 27 Jul 2009

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1. Graphical Abstract
2. Scheme 1: Biosynthetic pathway from fluoride ion to fluoroacetate 1 and 4-fluorothreonine 2 in S. cattleya [2].
  
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3. Figure 1: Synthesized phosphonates 8 and 9 and cyclic phostones 10 and 11.
  
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4. Scheme 2: Synthetic route A. Reagents and conditions: a) acetone, concd H₂SO₄ (cat.), 6 h, 86%; b) Deoxo-fluo...
  
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5. Scheme 3: Synthetic route B. Reagents and conditions: a) acetone, concd H₂SO₄ (cat.), 4 h, 90%; b) TrCl, pyri...
  
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6. Figure 2: X-Ray crystal structure of cyclohexylammonium salt 8a.
  
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Beilstein J. Org. Chem. 2009, 5, No. 37, doi:10.3762/bjoc.5.37

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The vicinal difluoro motif: The synthesis and conformation of erythro- and threo- diastereoisomers of 1,2-difluorodiphenylethanes, 2,3-difluorosuccinic acids and their derivatives

David O'Hagan,
Henry S. Rzepa,
Martin Schüler and
Alexandra M. Z. Slawin

Full Research Paper
Published 02 Oct 2006

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1. Graphical Abstract
2. Scheme 1: Synthesis of vicinal dimethyl difluorosuccinates. The conversion of the tartrates 1 with SF₄ and HF ...
  
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3. Scheme 2: Schlosser's route to vicinal erythro- or threo- difluoro alkanes 5 [13].
  
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4. Scheme 3: Halofluorination of electron-rich alkenes with in situ fluoride displacement generates vicinal difl...
  
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5. Scheme 4: Bromofluorination of stilbene [19].
  
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6. Scheme 5: Treatment of anti-14 with base generated the E-fluorostilbene 15 by an anti elimination mechanism.
  
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7. Scheme 6: Hypothesis for the predominent retention of configuration during fluoride substitution via phenoniu...
  
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8. Scheme 7: Proposed C-C bond rotation during the preparation of 14 from cis-stilbene.
  
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9. Figure 1: Crystal structure of erythro-13.
  
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10. Figure 2: X-ray structure of threo-13.
  
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11. Figure 3: Expanded regions of the second order AA'XX' spin systems in the ¹H-NMR (left) and ¹⁹F-NMR spectra (...
  
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12. Figure 4: NMR coupling constants and calculated relative energies (kcalmol^-1) of the staggered conformers of ...
  
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13. Scheme 8: Synthesis of erythro-19 via ozonolysis of erythro-13.
  
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14. Figure 5: X-ray structure of erythro-19.
  
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15. Figure 6: X-ray structure of threo-19.
  
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16. Scheme 9: Strategy for the preparation of diastereoisomers of erythro- and threo- 20.
  
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17. Figure 7: NMR (CDCl₃, RT) coupling constants of erythro- and threo- 2,3-difluoro-3-phenylpropionates 21.
  
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18. Figure 8: Newman projections showing the staggered conformations of erythro- and threo- 21.
  
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19. Figure 9: X-ray structure of methyl threo- 21.
  
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20. Figure 10: The preferred conformation of α-fluoroamides has the C-F and amide carbonyl anti-planar [29,30].
  
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21. Scheme 10: The synthesis of stereoisomers of erythro- and threo- 22. These isomers could be separated by chrom...
  
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22. Figure 11: X-ray structure of erythro-22.
  
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23. Figure 12: Crystal packing of erythro-22 clearly indicating intermolecular hydrogen bonding.
  
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24. Figure 13: X-ray structure of threo-22.
  
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25. Figure 14: The conformations of erythro- and threo- 23 are very different as a consequence of each conformatio...
  
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26. Figure 15: ³J_HF and ³J_HH coupling constants for the erythro (yellow) and threo (blue) diastereoisomers of the ...
  
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27. Figure 16: Newman projections of the three staggered conformations of the erythro and threo stereoisomers of t...
  
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28. Figure 17: The average coupling constant with no conformational bias. The limiting coupling constants J_g = 8 H...
  
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29. Figure 18: The observed ³J_HF coupling constants are an average over the rotational isomers.
  
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Supp. Info

Graphical Abstract

Beilstein J. Org. Chem. 2006, 2, No. 19, doi:10.1186/1860-5397-2-19

Full Text

Stereoselective α-fluoroamide and α-fluoro- γ-lactone synthesis by an asymmetric zwitterionic aza-Claisen rearrangement

Kenny Tenza,
Julian S. Northen,
David O'Hagan and
Alexandra M. Z. Slawin

Full Research Paper
Published 17 Oct 2005

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1. Graphical Abstract
2. Scheme 1: Reagents: i N₃CH₂C(O)F, AlMe₃
  
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3. Scheme 2: Reagents: i KF, DMF, 73%; ii NaOH, EtOH then aqHCl, 44%; iii (CO)₂Cl₂, 90%.
  
  Jump to Scheme 2
4. Scheme 3: Reagents: i iPr₂EtN, Yb(OTf)₃, 9, DCM, 92%; ii I₂, THF/ H₂O, Na₂S₂O₃, 82%.
  
  Jump to Scheme 3
5. Scheme 4: Reagents i. I₂, THF/H₂O.
  
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6. Scheme 5: Reagents: (a) I₂, THF/H₂O, Na₂S₂O₃.
  
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7. Scheme 6: Reagents: i iPr₂EtN, Yb(OTf)₃, 9 or PhCHFCOCl, DCM, 92%.
  
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8. Scheme 7: Reagents: i. LiAlH₄, THF, 99%; ii. HCl-Et₂O.
  
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9. Figure 1: ORTEP drawing of (2S, 2'S)-28 showing two crystallographically independent molecules within the uni...
  
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10. Scheme 8: Reagents: (a) I₂, THF/H₂O, Na₂S₂O₃.
  
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Graphical Abstract

Beilstein J. Org. Chem. 2005, 1, No. 13, doi:10.1186/1860-5397-1-13

Full Text

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