New reactive intermediates in organic chemistry

Editor: Prof. Götz Bucher
University of Glasgow

Research into reactive intermediates has historically been part of the work involved in product studies. In order to characterize a reactive intermediate, it had to be trapped. Using internal quenchers (molecular clocks) providing well-defined competing reactions, product studies can even yield accurate values for intermolecular quenching reactions of reactive intermediates. More recent techniques to characterise reactive intermediates include matrix isolation spectroscopy, laser flash photolysis, or specialised mass-spectrometric techniques.

New reactive intermediates in organic chemistry

Götz Bucher

Editorial
Published 26 Mar 2013

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Beilstein J. Org. Chem. 2013, 9, 613–614, doi:10.3762/bjoc.9.67

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Presence or absence of a novel charge-transfer complex in the base-catalyzed hydrolysis of N-ethylbenzamide or ethyl benzoate

Shinichi Yamabe,
Wei Guan and
Shigeyoshi Sakaki

Full Research Paper
Published 29 Jan 2013

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1. Graphical Abstract
2. Scheme 1: A scheme of the base-catalyzed amide hydrolysis involving a zwitterion suggested by analyses of sol...
  
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3. Scheme 2: Two processes suggested by a proton-inventory NMR study [25].
  
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4. Scheme 3: Hydrolysis of the ester (saponification) and the amide adopted in this work. These are assigned as ...
  
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5. Scheme 4: A reaction model including the water cluster.
  
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6. Figure 1: A minimal model of the OH⁻ nucleophilic addition to the substrate, Ph–C(=O)–X–Et. Three ((a), (b) a...
  
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7. Figure 2: Geometries and B3LYP/6-31(+)G(d) activation energies of TS1(es) in the reaction between ethyl benzo...
  
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8. Figure 3: Geometries and activation energies of TS1(am) in the reaction between N-ethylbenzamide and OH^-(H₂O)_n...
  
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9. Figure 4: Reaction paths of the ester n = 16 hydrolysis, starting from the boxed reactant-like complex toward...
  
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10. Scheme 5: A possibility that the neutral tetrahedral intermediate is the stock of concentrations for the irre...
  
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11. Figure 5: Reaction paths of the amide n = 16 hydrolysis. XYZ coordinates in VII.d (Supporting Information File 1).
  
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12. Figure 6: Changes of B3LYP/6-311++G(d,p) SCRF = PCM//B3LYP/6-31(+)G(d) Et + ZPE and (Gibbs free energies) of ...
  
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13. Figure 7: The effect of the counter ion Na⁺ on TS1(es). When the position of Na⁺ is near the nucleophile OH⁻ ...
  
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14. Figure 8: Changes of Et + ZPE and (Gibbs free energies) of the amide hydrolysis in Figure 5 and Figure S4 (Supporting Information File 1). Energie...
  
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15. Scheme 6: Summary of the present calculations.
  
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16. Figure 9: Central parts of the geometries of TS1(es) and TS1(am) of n = 32, which are taken from Figure 2 and Figure 3, respe...
  
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Beilstein J. Org. Chem. 2013, 9, 185–196, doi:10.3762/bjoc.9.22

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Caryolene-forming carbocation rearrangements

Quynh Nhu N. Nguyen and
Dean J. Tantillo

Full Research Paper
Published 13 Feb 2013

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1. Graphical Abstract
2. Figure 1: Caryol-1(11)-en-10-ol (1) and similar sesquiterpenoids. Note that a different atom numbering was us...
  
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3. Scheme 1: Initially proposed mechanism for caryolene (caryol-1(11)-en-10-ol, 1) formation. Atom numbers for f...
  
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4. Figure 2: Computed (top) and experimental (bottom, underlined italics) [2] ¹H and ¹³C chemical shifts for 1 (low...
  
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5. Figure 3: Computed minima and transition-state structure involved in the single-step conversion of A to C. Re...
  
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6. Figure 4: IRC from TS-AC toward C. Relative energies were calculated at the B3LYP/6-31+G(d,p) level.
  
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7. Scheme 2: Alternative mechanisms for caryolene formation.
  
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8. Figure 5: Computed pathway for the conversion of C to E. Relative energies shown (kcal/mol) were calculated a...
  
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9. Figure 6: IRC from TS-GE toward E. Relative energies were calculated at the B3LYP/6-31+G(d,p) level. Selected...
  
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10. Figure 7: Computed pathway for the conversion of C to E in the presence of ammonia. Relative energies shown (...
  
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11. Figure 8: Predicted energetics for the conversion of A to E in the absence (blue) and presence (auburn) of am...
  
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Beilstein J. Org. Chem. 2013, 9, 323–331, doi:10.3762/bjoc.9.37

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Electron and hydrogen self-exchange of free radicals of sterically hindered tertiary aliphatic amines investigated by photo-CIDNP

Martin Goez,
Isabell Frisch and
Ingo Sartorius

Full Research Paper
Published 26 Feb 2013

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1. Graphical Abstract
2. Scheme 1: Mechanism explaining the CIDNP effects in sensitized hydrogen abstractions from tertiary aliphatic ...
  
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3. Figure 1: Time-resolved CIDNP in sensitized (sensitizers xanthone (XA), benzophenone (BP), or anthraquinone (...
  
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4. Figure 2: Influence of the laser intensity E on the observed exchange-rate constant k_ex (DABCO) (main plot) a...
  
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5. Scheme 2: Pathways from the free radicals to the product.
  
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6. Figure 3: Time-resolved CIDNP signals of the 18 equivalent β protons (d, 0.98 ppm) of triisopropylamine (TIPA...
  
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7. Figure 4: Eyring plots for the self-exchange rate constants k_ex (TIPA) of triisopropylamine (TIPA) sensitized...
  
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Graphical Abstract

Beilstein J. Org. Chem. 2013, 9, 437–446, doi:10.3762/bjoc.9.46

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A new intermediate in the Prins reaction

Shinichi Yamabe,
Takeshi Fukuda and
Shoko Yamazaki

Full Research Paper
Published 05 Mar 2013

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1. Graphical Abstract
2. Scheme 1: A general scheme of the Prins reaction.
  
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3. Scheme 2: An example of the Prins reaction [4]. The product yields (%) are based on formaldehyde.
  
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4. Scheme 3: An equilibrium in the hydrolysis of the product, 1,3-dioxane.
  
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5. Scheme 4: Formation of the acetate of an allylic alcohol by Prins reaction [5].
  
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6. Scheme 5: A reaction mechanism involving the carbonium-ion intermediate X.
  
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7. Scheme 6: A reaction model composed of RHC=CH₂, (H₂C=O)₂ and H₃O⁺(H₂O)₁₃ to obtain the path of step 2 (Scheme 5). H₃O⁺...
  
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8. Figure 1: Geometries of the precursor and the transition states (TSs) of the Prins reaction of propene with (...
  
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9. Figure 2: Energy changes (in kcal/mol) of the propene Prins reaction calculated by B3LYP/6-311+G(d,p) SCRF=(P...
  
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10. Figure 3: Geometries of the transition states (TSs) of the Prins reaction of styrene + (formaldehyde)₂ + H₃O⁺...
  
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11. Figure 4: Energy changes (in kcal/mol) of the styrene Prins reaction calculated by B3LYP/6-311+G(d,p) SCRF = ...
  
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12. Figure 5: TS1(Ph) geometries of n = 20 and n = 30 in the reacting system of styrene + H₃O⁺(H₂O)_n + (H₂C=O)₂ c...
  
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13. Scheme 7: Summary of the present calculated results. The ether in the box is the new intermediate found in th...
  
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Beilstein J. Org. Chem. 2013, 9, 476–485, doi:10.3762/bjoc.9.51

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A computational study of base-catalyzed reactions of cyclic 1,2-diones: cyclobutane-1,2-dione

Nargis Sultana and
Walter M. F. Fabian

Full Research Paper
Published 21 Mar 2013

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1. Graphical Abstract
2. Scheme 1: Reactions of 1,2-dicarbonyl compounds with base.
  
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3. Scheme 2: Reactions of cyclic 1,2-diones with base.
  
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4. Scheme 3: Possible intermediates, transition structures, and products considered for the reaction of cyclobut...
  
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5. Figure 1: CEPA-1/def2-QZVPP calculated reaction paths for the reaction of 1·(H₂O)₂ + [OH(H₂O)₄]^–.
  
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6. Figure 2: M06-2X/6-31+G(d,p) calculated structures of stationary points along the benzilic acid type rearrang...
  
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7. Scheme 4: Reaction sequence calculated for an extended conformation of Int2.
  
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8. Figure 3: Calculated structure of transition state TS3a. Distances are given in angstrom (Å), angles in degre...
  
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9. Figure 4: Calculated structures of pertinent stationary points along path C. Distances are given in angstroms...
  
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10. Scheme 5: Actual path C obtained by the calculations (as in Scheme 3, Int1, TS4, Int4, and TS5 are hydrated by six wa...
  
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Beilstein J. Org. Chem. 2013, 9, 594–601, doi:10.3762/bjoc.9.64

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Kinetics and mechanism of the anilinolysis of aryl phenyl isothiocyanophosphates in acetonitrile

Hasi Rani Barai and
Hai Whang Lee

Full Research Paper
Published 26 Mar 2013

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1. Graphical Abstract
2. Scheme 1: Reactions of Y-aryl phenyl isothiocyanophosphates (1a–e) with XC₆H₄NH₂(D)₂ in MeCN at 55.0 °C.
  
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3. Figure 1: Brönsted plots with X [log k_H versus pK_a(X)] of the reactions of Y-aryl phenyl isothiocyanophosphat...
  
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4. Figure 2: Plots of ρ_X versus σ_Y and ρ_Y versus σ_X of the reactions of Y-aryl phenyl isothiocyanophosphates wit...
  
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5. Scheme 2: Backside attack involving in-line-type TSb and frontside attack involving a hydrogen-bonded, four-c...
  
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6. Scheme 3: Backside attack involving a hydrogen-bonded, four-center-type TSb-H.
  
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Beilstein J. Org. Chem. 2013, 9, 615–620, doi:10.3762/bjoc.9.68

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Photoionisation of the tropyl radical

Kathrin H. Fischer,
Patrick Hemberger,
Andras Bodi and
Ingo Fischer

Full Research Paper
Published 09 Apr 2013

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1. Graphical Abstract
2. Figure 1: Structure of the tropyl radical 1, its cation 2 and the precursor bitropyl 3.
  
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3. Figure 2: Mass spectra of bitropyl without pyrolysis at 7.8 and 8.7 eV (top and centre trace) and with pyroly...
  
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4. Figure 3: Threshold photoelectron spectrum of tropyl (black line). The Franck–Condon simulation (red line) is...
  
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5. Figure 4: TPE spectrum of tropyl (solid line) and cyclopentadienyl (m/z = 65, dashed line) in the 7–13 eV pho...
  
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6. Figure 5: The shape of the C₅H₅⁺ peak in the mass spectrum changes with photon energy. While the peak is symm...
  
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Beilstein J. Org. Chem. 2013, 9, 681–688, doi:10.3762/bjoc.9.77

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High-spin intermediates of the photolysis of 2,4,6-triazido-3-chloro-5-fluoropyridine

Sergei V. Chapyshev,
Denis V. Korchagin,
Patrik Neuhaus and
Wolfram Sander

Full Research Paper
Published 16 Apr 2013

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1. Graphical Abstract
2. Scheme 1: Examples of selective photolysis of the azido groups.
  
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3. Scheme 2: Possible photoproducts of triazide 11.
  
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4. Figure 1: EPR spectra: (a) simulated spectrum for a mixture of five nitrenes with (i) S = 1, g = 2.003, D_T = ...
  
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5. Figure 2: UB3LYP/6-311G*+BLYP/EPRII calculated orientations of the tensors D^SS and D^SO in nitrenes 15–18. The...
  
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6. Figure 3: Mulliken spin populations on the nitrene units and parameters D_T^SS in cm⁻¹ of triplet nitrenes 12–14...
  
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7. Scheme 3: Initial stages of the photolysis of triazide 11.
  
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8. Figure 4: UB3LYP/6-311+G* orbital density in the LUMO of triazide 11 and CIS/6-311+G* orbital density in the ...
  
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Beilstein J. Org. Chem. 2013, 9, 733–742, doi:10.3762/bjoc.9.83

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3-Pyridylnitrene, 2- and 4-pyrimidinylcarbenes, 3-quinolylnitrenes, and 4-quinazolinylcarbenes. Interconversion, ring expansion to diazacycloheptatetraenes, ring opening to nitrile ylides, and ring contraction to cyanopyrroles and cyanoindoles

Curt Wentrup,
Nguyen Mong Lan,
Adelheid Lukosch,
Pawel Bednarek and
David Kvaskoff

Full Research Paper
Published 17 Apr 2013

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1. Graphical Abstract
2. Scheme 1: 4-Pyridylnitrene–2-pyrazinylcarbene interconversion.
  
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3. Scheme 2: Ring expansion and ring contraction in 2-pyridylnitrene (4).
  
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4. Scheme 3: Ring opening and ring expansion in 3-pyridylnitrene (10).
  
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5. Scheme 4: Ring opening and ring contraction in 3-pyridylnitrene (10) and diazacycloheptatetraene 16.
  
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6. Figure 1: Energy profile for the ring opening and ring contraction in 3-pyridylnitrene 10 and 1,6-diazacycloh...
  
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7. Scheme 5: Potential direct ring contraction in 3-pyridylnitrene (10).
  
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8. Scheme 6: Ring contraction by ring opening to nitrile ylide 11.
  
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9. Scheme 7: Generation of pyrimidinyldiazomethanes and pyrimidinylcarbenes.
  
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10. Scheme 8: Formation of cyanopyrroles by FVT of tetrazolylpyrimidines.
  
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11. Scheme 9: Rearrangements of pyrimidinylcarbenes to cyanopyrroles via nitrile ylides 31 and 37.
  
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12. Scheme 10: Rearrangements of phenyl(dimethylpyrimidinyl)carbene.
  
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13. Scheme 11: Photolysis of 3-azido-2-phenylquinoline.
  
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14. Figure 2: IR difference spectra from the photolysis of 3-azido-2-phenylquinoline (44) in Ar matrix. (a) Calcu...
  
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15. Figure 3: UV–vis spectra from the sequential photolysis of 3-azido-2-phenylquinoline (44) in Ar matrix at 310...
  
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16. Scheme 12: Preparative FVT of 3-azido-2-phenylquinoline.
  
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17. Scheme 13: FVT of 2-phenyl-4-quinazolinylcarbene precursors.
  
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Beilstein J. Org. Chem. 2013, 9, 743–753, doi:10.3762/bjoc.9.84

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4-Pyridylnitrene and 2-pyrazinylcarbene

Curt Wentrup,
Ales Reisinger and
David Kvaskoff

Full Research Paper
Published 17 Apr 2013

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1. Graphical Abstract
2. Scheme 1: Phenylnitrene–2-pyridylcarbene rearrangement.
  
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3. Scheme 2: Type I and type II ring opening and ring expansion in 3- and 2-pyridylnitrenes, respectively.
  
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4. Scheme 3: FVT reactions of 4-azidopyridine (18), 2-(5-tetrazolyl)pyrazine (23) and triazolo[1,5-a]pyrazine (24...
  
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5. Figure 1: Difference-IR spectrum of 2-diazomethylpyrazine (22) (positive peaks) in Ar matrix at 7 K, obtained...
  
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6. Figure 2: Ar matrix IR-difference spectra showing the products of broadband UV photolysis of 4-azidopyridine (...
  
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7. Figure 3: Top: calculated IR spectrum of 20 at the B3LYP/6-31G* level (wavenumbers scaled by 0.9613): ν’ (rel...
  
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8. Figure 4: Bottom: IR spectrum from the matrix photolysis of azide 18 after the azide has been depleted comple...
  
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9. Scheme 4: Photolysis reactions of azide 18 and triazole 24 in Ar matrix.
  
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Beilstein J. Org. Chem. 2013, 9, 754–760, doi:10.3762/bjoc.9.85

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Ring opening of 2-aza-3-borabicyclo[2.2.0]hex-5-ene, the Dewar form of 1,2-dihydro-1,2-azaborine: stepwise versus concerted mechanisms

Holger F. Bettinger and
Otto Hauler

Full Research Paper
Published 18 Apr 2013

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1. Graphical Abstract
2. Scheme 1: Isomerisation of bicyclo[2.2.0]hexa-1,3-diene, Dewar benzene (1), to benzene (2) and of 2-aza-3-bor...
  
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3. Figure 1: Geometries of 3 and 4 computed at the CCSD(T)/TZ2P and CASSCF(6,6)/6-31G* (in parentheses) levels o...
  
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4. Figure 2: Geometries of TS1 and TS2 computed at the CASSCF(6,6)/6-31G* level of theory. C1–N, N–B, C4–B, and ...
  
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5. Figure 3: Geometries of MIN1, TS3, TS4 and MIN2, TS5, TS6 computed at the CCSD(T)/TZ2P level of theory. C1–N,...
  
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6. Figure 4: Geometries of DIM1, COM1, and TS7 computed at the SCS-RIMP2/def2-TZVP level of theory. Distances ar...
  
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Beilstein J. Org. Chem. 2013, 9, 761–766, doi:10.3762/bjoc.9.86

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Utilizing the σ-complex stability for quantifying reactivity in nucleophilic substitution of aromatic fluorides

Magnus Liljenberg,
Tore Brinck,
Tobias Rein and
Mats Svensson

Full Research Paper
Published 23 Apr 2013

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1. Graphical Abstract
2. Figure 1: The structures investigated in the amination of heterocyclic and carbocyclic derivatives (series A ...
  
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3. Figure 2: –log k as a function of SS in water for series A and B.
  
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4. Figure 3: The structures investigated in the methoxylation of polychlorofluorobenzene derivatives (series C) ...
  
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5. Figure 4: −log k as a function of SS in methanol for series C.
  
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6. Figure 5: Optimized geometries, relative energies, and imaginary frequencies for the transition states and th...
  
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Beilstein J. Org. Chem. 2013, 9, 791–799, doi:10.3762/bjoc.9.90

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Spectroscopic characterization of photoaccumulated radical anions: a litmus test to evaluate the efficiency of photoinduced electron transfer (PET) processes

Maurizio Fagnoni,
Stefano Protti,
Davide Ravelli and
Angelo Albini

Full Research Paper
Published 24 Apr 2013

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1. Graphical Abstract
2. Scheme 1: Photoinduced electron transfer as an access to radical chemistry.
  
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3. Figure 1: Reduction potential (versus SCE) of the ground and excited state of acceptors and oxidation potenti...
  
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4. Figure 2: UV-monitoring of: (a) a 2 × 10⁻⁴ M solution of TCB in the presence of Bu₄Sn (10⁻² M) and (b) a 1.5 ...
  
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5. Figure 3: Absorption spectra of a freeze–pump–thaw deoxygenated MeCN solution irradiated at 313 nm of (a) 1,2...
  
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6. Scheme 2: Mechanistic scheme.
  
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7. Figure 4: Thermodynamics of the redox processes discussed (solid arrows represent exergonic electron donation...
  
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Beilstein J. Org. Chem. 2013, 9, 800–808, doi:10.3762/bjoc.9.91

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Substituent effect on the energy barrier for σ-bond formation from π-single-bonded species, singlet 2,2-dialkoxycyclopentane-1,3-diyls

Jianhuai Ye,
Yoshihisa Fujiwara and
Manabu Abe

Full Research Paper
Published 14 May 2013

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1. Graphical Abstract
2. Figure 1: Localized singlet diradicals.
  
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3. Scheme 1: Alkoxy group effect on the lifetime of π-single-bonded species DR.
  
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4. Scheme 2: Generation of singlet diradicals DRc–g and their reactivity in the photochemical denitrogenation of ...
  
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5. Scheme 3: Synthesis of azoalkanes AZc–f and AZg.
  
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6. Figure 2: (a) Absorption spectrum of the singlet diradical DRe in a MTHF matrix at 80 K; (b) transient absorp...
  
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Beilstein J. Org. Chem. 2013, 9, 925–933, doi:10.3762/bjoc.9.106

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An aniline dication-like transition state in the Bamberger rearrangement

Shinichi Yamabe,
Guixiang Zeng,
Wei Guan and
Shigeyoshi Sakaki

Full Research Paper
Published 03 Jun 2013

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1. Graphical Abstract
2. Scheme 1: The Bamberger rearrangement. In the square bracket, the apparent exchange of H and OH is shown.
  
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3. Scheme 2: The reaction occurs through the intermolecular rearrangement, on the basis that treatment of 1 in H₂...
  
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4. Scheme 3: A reaction of N-ethyl-N-phenylhydroxylamine, which demonstrates that the Bamberger rearrangement do...
  
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5. Scheme 4: A mechanism involving the nitrenium-ion intermediate 7. 8a is equal to 6.
  
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6. Scheme 5: A reaction scheme of the OH rearrangement containing one proton. Int is an intermediate. Species, 1...
  
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7. Figure 1: Geometric changes in the reaction of model II, (HO)HN–C₆H₅ + H₃O⁺(H₂O)₁₄ → H₃N⁺–C₆H₄–OH + (H₂O)₁₅.
  
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8. Figure 2: An assumed reaction system composed of Ph–NHOH and H₃O⁺(H₂O)₁₄. The green area represents the react...
  
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9. Figure 3: Energy changes (in kcal/mol) of Δ(E+ZPE) by B3LYP/6-311+G(d,p) SCRF = PCM//B3LYP/6-31G(d) and by [B...
  
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10. Scheme 6: A trans-type bond interchange was assumed. But, the reaction path could not be obtained. The group ...
  
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11. Scheme 7: An alternative model for the OH [1,5]-rearrangement in the dication system.
  
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12. Figure 4: Geometric changes in the reaction of model III, (HO)HN–C₆H₅ + (H₃O⁺)₂(H₂O)₁₃ → H₃N⁺–C₆H₄–OH + (H₃O⁺...
  
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13. Figure 5: Energy changes (in kcal/mol) of model III. The corresponding geometries are shown in Figure 4. The apparent...
  
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14. Figure 6: TS2(IV) and TS2(IV, [1,3]-shift) in the reaction (model IV), Ph–NH(OH) + (H₃O⁺)₂(H₂O)₂₄ → HO–C₆H₄–NH...
  
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15. Figure 7: TS2(V) and TS2(V, [1,3]-shift) in the reaction (model V), Ph–NH(OH) + (H₃O⁺)₂(H₂O)₁₃ + Cl⁻ → o- and ...
  
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16. Scheme 8: A mechanism of the Bamberger rearrangement based on the present results. 1, 2, 2H⁺, 5 and 9 are def...
  
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Beilstein J. Org. Chem. 2013, 9, 1073–1082, doi:10.3762/bjoc.9.119

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True and masked three-coordinate T-shaped platinum(II) intermediates

Manuel A. Ortuño,
Salvador Conejero and
Agustí Lledós

Review
Published 09 Jul 2013

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1. Graphical Abstract
2. Figure 1: Qualitative orbital diagram for a d⁸ metal in ML₄ square-planar and ML₃ T-shaped complexes.
  
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3. Figure 2: Walsh diagram for the d-block of a d⁸ ML₃ complex upon bending of one L–M–L angle.
  
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4. Figure 3: Neutral Y-shaped Pt complex Y1 [15]. Angles are given in degrees.
  
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5. Figure 4: General classification of T-shaped Pt(II) structures according to the fourth coordination site.
  
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6. Figure 5: Hydride, boryl and borylene true T-shaped Pt(II) complexes.
  
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7. Figure 6: NHC-based true T-shaped Pt(II) complexes.
  
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8. Figure 7: Phosphine-based agostic T-shaped Pt(II) complexes. Compounds in brackets correspond with hydrido–al...
  
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9. Figure 8: Phenylpyridine and NHC-based agostic T-shaped Pt(II) complexes.
  
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10. Figure 9: Counteranion coordination in T-shaped Pt(II) complexes.
  
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11. Figure 10: Phosphine-based solvento Pt(II) complexes.
  
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12. Figure 11: Nitrogen-based solvento Pt(II) complexes.
  
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13. Figure 12: Pincer-based solvento Pt(II) complexes.
  
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14. Figure 13: Structure of the QM/MM optimized cisplatin–protein adduct [94].
  
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15. Figure 14: NMR coupling constants used for the characterization of three-coordinate Pt(II) species.
  
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16. Figure 15: The chemical formula of the complexes discussed in Table 2.
  
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17. Scheme 1: Halogen abstraction from 1.
  
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18. Scheme 2: Halogen abstraction from 2 forming the dicationic complex T3 [22].
  
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19. Scheme 3: Hydrogenation of complexes A5a and A5b [39].
  
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20. Scheme 4: Hydrogenation of complexes 3 and A5c [40].
  
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21. Scheme 5: Intermolecular C–H bond activation from T5a [28].
  
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22. Scheme 6: Protonation of complexes 4 [35,36].
  
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23. Scheme 7: Cyclometalation of 5 [43].
  
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24. Scheme 8: Protonation of 6.
  
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25. Scheme 9: Reductive elimination of ethane from 7.
  
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26. Scheme 10: Reductive elimination of methane from six-coordinate Pt(IV) complexes.
  
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27. Scheme 11: Proposed dissociative mechanism for the fluxional motion of dmphen in [Pt(Me)(dmphen)(PR₃)]⁺ comple...
  
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28. Figure 16: Feasible interactions for unsaturated intermediates 11b (left) and 12b (right) during fluxional mot...
  
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29. Scheme 12: Halogen abstraction from 13a,b and subsequent cyclometalation to yield complexes A5a,b [39].
  
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30. Scheme 13: Proposed mechanism for the acid-catalyzed cyclometalation of 14 via intermediate 15 [41].
  
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31. Scheme 14: Proposed mechanism for the formation of 19 [102].
  
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32. Scheme 15: Cyclometalation of 20 via thioether dissociation [117].
  
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33. Figure 17: Gibbs energy profile (in chloroform solvent) for the cyclometalation of 23 [120].
  
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34. Scheme 16: Coordination of tmtu to 29 and subsequent C–H bond activation via three-coordinate species 31 and 32...
  
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35. Scheme 17: Cyclometalation process of NHC-based Pt(II) complexes [28,44].
  
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36. Scheme 18: Cyclometalation process of complex A9 [43].
  
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37. Scheme 19: “Rollover” reaction of 38 and subsequent oligomerization [123].
  
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38. Scheme 20: Proposed mechanism for the formation of cyclometalated species 44 [124].
  
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39. Scheme 21: Self-assembling process of 45 by “rollover” reaction [126].
  
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40. Scheme 22: “Rollover” reaction of A9. Energies (solvent) in kcal mol⁻¹ [127].
  
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41. Scheme 23: Proposed mechanisms for the “rollover” cyclometalation of 52 in gas-phase ion-molecule reactions [128].
  
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42. Scheme 24: β-H elimination and 1,2-insertion equilibrium involving A1d and the subsequent generation of 57 [35].
  
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43. Scheme 25: Proposed mechanism for thermolysis of 7b and 7c in benzene-d₆ and cyclohexane-d₁₂ solvents [101].
  
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44. Scheme 26: β-H elimination process of A11a [28].
  
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45. Scheme 27: Intermolecular C–H bond activation from 62 [95].
  
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46. Scheme 28: Reductive elimination of methane from 65 followed by CD₃CN coordination or C–D bond-activation proc...
  
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47. Figure 18: DFT-optimized structures describing the κ² (69, left) and κ³ (69’, right) coordination modes of [Pt...
  
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48. Scheme 29: Intermolecular arene C–H bond activation from NHC-based complexes [28].
  
  Jump to Scheme 29
49. Figure 19: Energy profiles (in benzene solvent) for the benzene C–H bond activation from A11a, A11b, T5a and T...
  
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50. Scheme 30: Intermolecular arene C–H bond activation from PNP-based complex 71 [12].
  
  Jump to Scheme 30
51. Scheme 31: Intermolecular C–H bond-activation by gas-phase ion-molecule reactions of 74 [7,142].
  
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52. Scheme 32: Dihydrogen activation through complexes A5a, A5b [39], A5c [40] and S1a [54].
  
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53. Scheme 33: Dihydrogen activation through complexes A7 and 16 [41]. For a: see Scheme 13.
  
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54. Scheme 34: Br₂ and I₂ bond activations through complexes A11a and T5a [143].
  
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55. Scheme 35: Detection and isolation of the Pt(III) complex 81a [143].
  
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56. Scheme 36: Cl₂ bond activation through complexes 82 and 83 [144].
  
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57. Scheme 37: cis–trans Isomerization mechanism of the solvento Pt(II) complexes S5 [2,61].
  
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58. Figure 20: Energy profiles for the isomerization of complexes [Pt(R)(PMe₃)₂(NCMe)]⁺ where R means Me (85a, red...
  
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59. Figure 21: DFT-optimized structure of intermediate 86 [62]. Bond distances in angstrom and angles in degrees.
  
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60. Scheme 38: Proposed dissociative ligand-substitution mechanism of cis-[Pt(R)₂S₂] complexes (87) [117].
  
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61. Scheme 39: Proposed mechanisms for the ligand substitution of the dinuclear species 91 [146].
  
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Graphical Abstract

Beilstein J. Org. Chem. 2013, 9, 1352–1382, doi:10.3762/bjoc.9.153

Full Text

Electron self-exchange activation parameters of diethyl sulfide and tetrahydrothiophene

Martin Goez and
Martin Vogtherr

Full Research Paper
Published 19 Jul 2013

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1. Graphical Abstract
2. Figure 1: Time-resolved CIDNP measurements on a sample of 5 × 10⁻³ M DES in acetonitrile-d₃ sensitized by 2 ×...
  
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3. Figure 2: Eyring plots of the self-exchange rate constants k_ex for DES (open circles and broken line; linear ...
  
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Graphical Abstract

Beilstein J. Org. Chem. 2013, 9, 1448–1454, doi:10.3762/bjoc.9.164

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Isolation and X-ray characterization of palladium–N complexes in the guanylation of aromatic amines. Mechanistic implications

Abdessamad Grirrane,
Hermenegildo Garcia and
Eleuterio Álvarez

Full Research Paper
Published 22 Jul 2013

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1. Graphical Abstract
2. Scheme 1: Isolation of trans-dichlorobis(4-iodoanilino-ĸN)palladium(II) and trans-dichlorobis[1,3-diisopropyl...
  
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3. Scheme 2: Isolation of trans-dichlorobis[1,3-diisopropyl-2-(aryl)guanidino-ĸN(aryl)]palladium(II) complexes (...
  
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4. Figure 1: (Top) ORTEP view of the centrosymmetric molecule 4a. (Bottom) Crystal packing detail of 4a viewed a...
  
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5. Figure 2: (Left) ORTEP representation of 4b. (Right) Crystal packing detail of 4b viewed along the a-axis sho...
  
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6. Figure 3: (Left) ORTEP representation of 4c. (Right) Crystal-packing detail of 4c viewed along the a-axis sho...
  
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7. Scheme 3: Guanylation reactions of anilines 1a–c by N,N’-diisopropylcarbodiimide (2) catalyzed by Pd(II) salt....
  
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8. Figure 4: (Left) ORTEP representation of 5a. (Right) Crystal packing details of 5a viewed along the a-axis sh...
  
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9. Scheme 4: Possible mechanisms for the C–N coupling catalyzed by PdCl₂(NCMe)₂ in homogeneous phase.
  
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Graphical Abstract

Beilstein J. Org. Chem. 2013, 9, 1455–1462, doi:10.3762/bjoc.9.165

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Thermochemistry and photochemistry of spiroketals derived from indan-2-one: Stepwise processes versus coarctate fragmentations

Götz Bucher,
Gernot Heitmann and
Rainer Herges

Full Research Paper
Published 15 Aug 2013

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1. Graphical Abstract
2. Figure 1: Formal, topological approach to derive coarctate reactions from pericyclic reactions; p, q: number ...
  
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3. Figure 2: Stereochemistry of coarctate reactions derived from a Hückel (top) and a Möbius band (bottom). The ...
  
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4. Scheme 1: Coarctate fragmentation of the spiroozonide derived from methylenecyclopropane.
  
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5. Scheme 2: Photochemically and thermally allowed coarctate fragmentations of spiroketals.
  
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6. Scheme 3: Precursors used in this study.
  
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7. Figure 3: Difference infrared spectrum, showing the changes in the IR spectrum after photolysis (λ_exc = 254 n...
  
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8. Figure 4: Infrared spectrum obtained upon FVP of 1 at T = 1143 K and trapping the pyrolysate in solid argon a...
  
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9. Figure 5: Infrared spectrum obtained upon FVP of 2 at T = 963 K and trapping the pyrolysate in solid argon at ...
  
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10. Figure 6: Infrared spectrum obtained upon FVP of 3 at T = 1043 K and trapping the pyrolysate in solid argon a...
  
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11. Scheme 4: Possible fragmentation pathways in the FVP of 1.
  
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12. Scheme 5: Possible fragmentation pathways in the FVP of 2.
  
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13. Scheme 6: Possible fragmentation pathways in the FVP of 3.
  
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Graphical Abstract

Beilstein J. Org. Chem. 2013, 9, 1668–1676, doi:10.3762/bjoc.9.191

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