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Search for "dynamic NMR" in Full Text gives 15 result(s) in Beilstein Journal of Organic Chemistry.
Synthesis of purines and adenines containing the hexafluoroisopropyl group
- Viacheslav Petrov,
- Rebecca J. Dooley,
- Alexander A. Marchione,
- Elizabeth L. Diaz,
- Brittany S. Clem and
- William Marshall
Beilstein J. Org. Chem. 2020, 16, 2739–2748, doi:10.3762/bjoc.16.224
- group in compounds 5a and 6a (see Table 2) because of the presence in the β-position relative to the CH(CF3)2 unit of the amino group, which is substantially bigger than a hydrogen atom. Dynamic NMR spectroscopy The broadening of resonances corresponding to the hexafluoroisopropyl moieties in the 19F
- referenced to internal tetramethylsilane or trichlorofluoromethane. The spectra were acquired at 298 K. Dynamic NMR experiments The dynamics of rotamer interconversion were studied on a Bruker AVIIIHD spectrometer with a 9.4 T magnetic field, equipped with a 10 mm F{H} probe suitable for high- and low
Graphical Abstract
Scheme 1: Reaction of purine (2) with tetrakis(trifluoromethyl)-1,3-dithietane (1).
Figure 1: Crystal structure of 2a, with the thermal ellipsoids drawn at 30% probability.
Scheme 2: Reaction of 4-azabenzimidazole (3) with tetrakis(trifluoromethyl)-1,3-dithietane (1).
Scheme 3: Reaction of 5-azabenzimidazole (4) with 1.
Scheme 4: Reaction of adenine (5) and 2-fluoroadenine (6) with tetrakis(trifluoromethyl)-1,3-dithietane (1).
Scheme 5: Reaction of theophylline (7) with tetrakis(trifluoromethyl)-1,3-dithietane (1).
Figure 2: Crystal structure of 7a, with the thermal ellipsoids drawn at 30% probability.
Scheme 6: Probable mechanism of the reaction of tetrakis(trifluoromethyl)-1,3-dithietane (1) with compounds 2–...
Figure 3: Top: 19F NMR spectra of 3a acquired over a sample temperature range of 223–373 K. Left: Fitted plot...
Figure 4: DFT-optimized structures of the two rotamers of 3a. Left: Lower-energy rotamer. Right: Higher-energ...
Strong hyperconjugative interactions limit solvent and substituent influence on conformational equilibrium: the case of cis-2-halocyclohexylamines
- Camila B. Francisco,
- Cleverton S. Fernandes,
- Ulisses Z. de Melo,
- Roberto Rittner,
- Gisele F. Gauze and
- Ernani A. Basso
Beilstein J. Org. Chem. 2019, 15, 818–829, doi:10.3762/bjoc.15.79
- -iodocyclohexylamine (I) by dynamic NMR and theoretical calculations. The experimental data pointed to an equilibrium strongly shifted toward the ea conformer (equatorial amine group and axial halogen), with populations greater than 90% for F, Cl and Br in both dichloromethane-d2 and methanol-d4. Theoretical
- preference for the ea conformer in cis-2-halocyclohexylamines, being strong enough to restrain the shift in the equilibrium due to other factors such as steric repulsion or solvent effects. Keywords: conformational equilibrium; cyclohexane derivatives; dynamic NMR; hyperconjugation; principal component
- group and equatorial halogen) and ea (equatorial amine group and axial halogen) conformers (Figure 1) by dynamic NMR (DNMR) and theoretical calculations. Results and Discussion Experimental conformational population Low-temperature NMR experiments allow the identification of the individual conformers
Graphical Abstract
Figure 1: Conformations of cis-2-halocyclohexylamines, where X = F, Cl, Br and I.
Figure 2: Variable-temperature 1H NMR spectra (500.13 MHz) for cis-2-chlorocyclohexylamine in dichloromethane-...
Figure 3: Potential energy surfaces (PESs) for cis-2-halocyclohexylamines for the C2–C1–N–H dihedral angle ro...
Figure 4: Populations of rotamers a, gX e gH in ae (top) and ea (bottom) conformers of cis-2-halocyclohexylam...
Figure 5: Nitrogen lone pair in rotamers gX (ae) and a (ea) oriented towards the halogen, making these rotame...
Figure 6: PCA for 22 variables corresponding to the hyperconjugative interactions for all rotamers in ae and ...
Figure 7: Sum of bonding (donor) and antibonding (acceptor) orbitals interactions of C1–H, C2–X and C3–Hax bo...
Figure 8: Orbitals overlap of σC1–H → σ*C2–X (left) and σC3–Hax → σ*C2–X (right) hyperconjugations in ea conf...
One hundred years of benzotropone chemistry
- Arif Dastan,
- Haydar Kilic and
- Nurullah Saracoglu
Beilstein J. Org. Chem. 2018, 14, 1120–1180, doi:10.3762/bjoc.14.98
Graphical Abstract
Scheme 1: Tropone (1), tropolone (2) and their resonance structures.
Figure 1: Natural products containing a tropone nucleus.
Figure 2: Possible isomers 11–13 of benzotropone.
Scheme 2: Synthesis of benzotropones 11 and 12.
Scheme 3: Oxidation products of benzotropylium fluoroborate (16).
Scheme 4: Oxidation of 7-bromo-5H-benzo[7]annulene (22).
Scheme 5: Synthesis of 4,5-benzotropone (11) using o-phthalaldehyde (27).
Scheme 6: Synthesis of 4,5-benzotropone (11) starting from oxobenzonorbornadiene 31.
Scheme 7: Acid-catalyzed cleavage of oxo-bridge of 34.
Scheme 8: Synthesis of 4,5-benzotropone (11) from o-xylylene dibromide (38).
Scheme 9: Synthesis of 4,5-benzotropone (11) via the carbene adduct 41.
Scheme 10: Heck coupling strategy for the synthesis of 11.
Scheme 11: Synthesis of benzofulvalenes via carbonyl group of 4,5-benzotropone (11).
Figure 3: Some cycloheptatrienylium cations.
Scheme 12: Synthesis of condensation product 63 and its subsequent oxidative cyclization products.
Figure 4: A novel series of benzo[7]annulenes prepared from 4,5-benzotropone (11).
Scheme 13: Preparation of substituted benzo[7]annulene 72 using the Mukaiyama-Michael reaction.
Figure 5: Possible benzo[7]annulenylidenes 73–75.
Scheme 14: Thermal and photochemical decomposition of 7-diazo-7H-benzo[7]annulene (76) and the trapping of int...
Scheme 15: Synthesis of benzoheptafulvalene 86.
Scheme 16: Synthesis of 7-(diphenylmethylene)-7H-benzo[7]annulene (89).
Scheme 17: Reaction of 4,5-benzotropone (11) with dimethyl diazomethane.
Scheme 18: Synthesis of dihydrobenzomethoxyazocine 103.
Scheme 19: Synthesis and reducibility of benzo-homo-2-methoxyazocines.
Scheme 20: Synthesis of 4,5-benzohomotropones 104 and 115 from 4,5-benzotropones 11 and 113.
Scheme 21: A catalytic deuterogenation of 4,5-benzotropone (11) and synthesis of 5-monosubstituted benzo[7]ann...
Scheme 22: Synthesis of methyl benzo[7]annulenes 131 and 132.
Scheme 23: Ambident reactivity of halobenzo[7]annulenylium cations 133a/b.
Scheme 24: Preparation of benzo[7]annulenylidene–iron complexes 147.
Scheme 25: Synthesis of 1-ethynylbenzotropone (150) and the etheric compound 152 from 4,5-benzotropone (11) wi...
Scheme 26: Thermal decomposition of 4,5-benzotropone (11).
Scheme 27: Reaction of 4,5-benzotropone (11) with 1,2-ethanediol and 1,2-ethanedithiol.
Scheme 28: Conversions of 1-benzosuberone (162) to 2,3-benzotropone (12).
Scheme 29: Synthesis strategies for 2,3-bezotropone (12) using 1-benzosuberones.
Scheme 30: Oxidation-based synthesis of 2,3-benzotropone (12) via 1-benzosuberone (162).
Scheme 31: Synthesis of 2,3-benzotropone (12) from α-tetralone (171) via ring-expansion.
Scheme 32: Preparation of 2,3-benzotropone (12) by using of benzotropolone 174.
Figure 6: Benzoheptafulvenes as condensation products of 2,3-benzotropone (12).
Scheme 33: Conversion of 2,3-benzotropone (12) to tosylhydrazone salt 182 and gem-dichloride 187.
Figure 7: Benzohomoazocines 191–193 and benzoazocines 194–197.
Scheme 34: From 2,3-benzotropone (12) to carbonium ions 198–201.
Scheme 35: Cycloaddition reactions of 2,3-benzotropone (12).
Scheme 36: Reaction of 2,3-benzotropone (12) with various reagents and compounds.
Figure 8: 3,4-Benzotropone (13) and its resonance structure.
Scheme 37: Synthesis of 6,7-benzobicyclo[3.2.0]hepta-3,6-dien-2-one (230).
Figure 9: Photolysis and thermolysis products of 230.
Figure 10: Benzotropolones and their tautomeric structures.
Scheme 38: Synthesis strategies of 4,5-benzotropolone (238).
Scheme 39: Synthesis protocol for 2-hydroxy-4,5-benzotropone (238) using oxazole-benzo[7]annulene 247.
Figure 11: Some quinoxaline and pyrazine derivatives 254–256 prepared from 4,5-benzotropolone (238).
Scheme 40: Nitration product of 4,5-benzotropolone (238) and its isomerization to 1-nitro-naphthoic acid (259)....
Scheme 41: Synthesis protocol for 6-hydroxy-2,3-benzotropone (239) from benzosuberone (162).
Scheme 42: Various reactions via 6-hydroxy-2,3-benzotropone (239).
Scheme 43: Photoreaction of 6-hydroxy-2,3-benzotropone (239).
Scheme 44: Synthesis of 7-hydroxy-2,3-benzotropone (241) from benzosuberone (162).
Scheme 45: Synthesis strategy for 7-hydroxy-2,3-benzotropone (241) from ketone 276.
Scheme 46: Synthesis of 7-hydroxy-2,3-benzotropone (241) from β-naphthoquinone (280).
Scheme 47: Synthesis of 7-hydroxy-2,3-benzotropone (241) from bicyclic endoperoxide 213.
Scheme 48: Synthesis of 7-hydroxy-2,3-benzotropone (241) by ring-closing metathesis.
Figure 12: Various monosubstitution products 289–291 of 7-hydroxy-2,3-benzotropone (241).
Scheme 49: Reaction of 7-hydroxy-2,3-benzotropone (241) with various reagents.
Scheme 50: Synthesis of 4-hydroxy-2,3-benzotropones 174 and 304 from diketones 300/301.
Scheme 51: Catalytic hydrogenation of diketones 300 and 174.
Scheme 52: Synthesis of halo-benzotropones from alkoxy-naphthalenes 306, 307 and 310.
Figure 13: Unexpected byproducts 313–315 during synthesis of chlorobenzotropone 309.
Figure 14: Some halobenzotropones and their cycloadducts.
Scheme 53: Multisep synthesis of 2-chlorobenzotropone 309.
Scheme 54: A multistep synthesis of 2-bromo-benzotropone 26.
Scheme 55: A multistep synthesis of bromo-2,3-benzotropones 311 and 316.
Scheme 56: Oxidation reactions of 8-bromo-5H-benzo[7]annulene (329) with some oxidants.
Scheme 57: Synthesis of 2-bromo-4,5-benzotropone (26).
Scheme 58: Synthesis of 6-chloro-2,3-benzotropone (335) using LiCl and proposed intermediate 336.
Scheme 59: Reaction of 7-bromo-2,3-benzotropone (316) with methylamine.
Scheme 60: Reactions of bromo-2,3-benzotropones 26 and 311 with dimethylamine.
Scheme 61: Reactions of bromobenzotropones 311 and 26 with NaOMe.
Scheme 62: Reactions of bromobenzotropones 26 and 312 with t-BuOK in the presence of DPIBF.
Scheme 63: Cobalt-catalyzed reductive cross-couplings of 7-bromo-2,3-benzotropone (316) with cyclic α-bromo en...
Figure 15: Cycloadduct 357 and its di-π-methane rearrangement product 358.
Scheme 64: Catalytic hydrogenation of 2-chloro-4,5-benzotropone (311).
Scheme 65: Synthesis of dibromo-benzotropones from benzotropones.
Scheme 66: Bromination/dehydrobromination of benzosuberone (162).
Scheme 67: Some transformations of isomeric dibromo-benzotropones 261A/B.
Scheme 68: Transformations of benzotropolone 239B to halobenzotropolones 369–371.
Figure 16: Bromobenzotropolones 372–376 and 290 prepared via bromination/dehydrobromination strategy.
Scheme 69: Synthesis of some halobenzotropolones 289, 377 and 378.
Figure 17: Bromo-chloro-derivatives 379–381 prepared via chlorination.
Scheme 70: Synthesis of 7-iodo-3,4-benzotropolone (382).
Scheme 71: Hydrogenation of bromobenzotropolones 369 and 370.
Scheme 72: Debromination reactions of mono- and dibromides 290 and 375.
Figure 18: Nitratation and oxidation products of some halobenzotropolenes.
Scheme 73: Azo-coupling reactions of some halobenzotropolones 294, 375 and 378.
Figure 19: Four possible isomers of dibenzotropones 396–399.
Figure 20: Resonance structures of tribenzotropone (400).
Scheme 74: Two synthetic pathways for tribenzotropone (400).
Scheme 75: Synthesis of tribenzotropone (400) from dibenzotropone 399.
Scheme 76: Synthesis of tribenzotropone (400) from 9,10-phenanthraquinone (406).
Scheme 77: Synthesis of tribenzotropone (400) from trifluoromethyl-substituted arene 411.
Figure 21: Dibenzosuberone (414).
Figure 22: Reduction products 415 and 416 of tribenzotropone (400).
Figure 23: Structures of tribenzotropone dimethyl ketal 417 and 4-phenylfluorenone (412) and proposed intermed...
Figure 24: Structures of benzylidene- and methylene-9H-tribenzo[a,c,e][7]annulenes 419 and 420 and chiral phos...
Figure 25: Structures of tetracyclic alcohol 422, p-quinone methide 423 and cation 424.
Figure 26: Structures of host molecules 425–427.
Scheme 78: Synthesis of non-helical overcrowded derivatives syn/anti-431.
Figure 27: Hexabenzooctalene 432.
Figure 28: Structures of possible eight isomers 433–440 of naphthotropone.
Scheme 79: Synthesis of naphthotropone 437 starting from 1-phenylcycloheptene (441).
Scheme 80: Synthesis of 10-hydroxy-11H-cyclohepta[a]naphthalen-11-one (448) from diester 445.
Scheme 81: Synthesis of naphthotropone 433.
Scheme 82: Synthesis of naphthotropones 433 and 434 via cycloaddition reaction.
Scheme 83: Synthesis of naphthotropone 434 starting from 452.
Figure 29: Structures of tricarbonyl(tropone)irons 458, and possible cycloadducts 459.
Scheme 84: Synthesis of naphthotropone 436.
Scheme 85: Synthesis of precursor 465 for naphthotropone 435.
Scheme 86: Generation of naphthotropone 435 from 465.
Figure 30: Structures of tropylium cations 469 and 470.
Figure 31: Structures of tropylium ions 471+.BF4−, 472+.BF4−, and 473+.BF4−.
Scheme 87: Synthesis of tropylium ions 471+.BF4− and 479+.ClO4−.
Scheme 88: Synthesis of 1- and 2-methylanthracene (481 and 482) via carbene–carbene rearrangement.
Figure 32: Trapping products 488–490.
Scheme 89: Generation and chemistry of a naphthoannelated cycloheptatrienylidene-cycloheptatetraene intermedia...
Scheme 90: Proposed intermediates and reaction pathways for adduct 498.
Scheme 91: Exited-state intramolecular proton transfer of 505.
Figure 33: Benzoditropones 506 and 507.
Scheme 92: Synthesis of benzoditropone 506e.
Scheme 93: Synthetic approaches for dibenzotropone 507 via tropone (1).
Scheme 94: Formation mechanisms of benzoditropone 507 and 516 via 515.
Scheme 95: Synthesis of benzoditropones 525 and 526 from pyromellitic dianhydride (527).
Figure 34: Possible three benzocyclobutatropones 534–536.
Scheme 96: Synthesis of benzocyclobutatropones 534 and 539.
Scheme 97: Synthesis attempts for benzocyclobutatropone 545.
Scheme 98: Generation and trapping of symmetric benzocyclobutatropone 536.
Scheme 99: Synthesis of chloro-benzocyclobutatropone 552 and proposed mechanism of fluorenone derivatives.
Scheme 100: Synthesis of tropolone analogue 559.
Scheme 101: Synthesis of tropolones 561 and 562.
Figure 35: o/p-Tropoquinone rings (563 and 564) and benzotropoquinones (565–567).
Scheme 102: Synthesis of benzotropoquinone 566.
Scheme 103: Synthesis of benzotropoquinone 567 via a Diels–Alder reaction.
Figure 36: Products 575–577 through 1,2,3-benzotropoquinone hydrate 569.
Scheme 104: Structures 578–582 prepared from tropoquinone 567.
Figure 37: Two possible structures 583 and 584 for dibenzotropoquinone, and precursor compound 585 for 583.
Scheme 105: Synthesis of saddle-shaped ketone 592 using dibenzotropoquinone 584.
One-pot three-component route for the synthesis of S-trifluoromethyl dithiocarbamates using Togni’s reagent
- Azim Ziyaei Halimehjani,
- Martin Dračínský and
- Petr Beier
Beilstein J. Org. Chem. 2017, 13, 2502–2508, doi:10.3762/bjoc.13.247
- DFT calculations. Figure 1 depicts variable temperature 1H NMR spectra of compound 4c. The coalescence of the methyl signals can be observed at 308 K, whereas the coalescence of the CH2 signals would require an even higher temperature than 328 K. Complete lineshape analysis approach (dynamic NMR, dNMR
Graphical Abstract
Scheme 1: Synthetic routes for the preparation of trifluoromethyl dithiocarbamates.
Scheme 2: Synthesis of S-trifluoromethyl dithiocarbamates. Isolated yields are given in parentheses.
Scheme 3: Formation of benzyl isothiocyanate in a reaction with benzylamine.
Figure 1: Variable temperature 1H NMR spectra of compound 4c (CH2 region on the left and CH3 region on the ri...
Figure 2: The Eyring plot obtained for the rotation around the N–C bond in compound 4c.
Figure 3: The optimized structure of compound 4b (left) and the transition state structure for the rotation a...
Correction: Synthesis, dynamic NMR characterization and XRD studies of novel N,N’-substituted piperazines for bioorthogonal labeling
- Constantin Mamat,
- Marc Pretze,
- Matthew Gott and
- Martin Köckerling
Beilstein J. Org. Chem. 2017, 13, 301–302, doi:10.3762/bjoc.13.32
- : building blocks; coalescence; dynamic NMR; labeling; Staudinger ligation; In the original article an incorrect caption for Figure 1 was given. The assignment of the solvents to the capital letters was not correct. The correct caption of Figure 1 is: 1H NMR spectra of compound 3a measured in five different
Figure 1: 1H NMR spectra of compound 3a measured in five different solvents: (A) acetonitrile-d3, (B) methano...
Synthesis, dynamic NMR characterization and XRD studies of novel N,N’-substituted piperazines for bioorthogonal labeling
- Constantin Mamat,
- Marc Pretze,
- Matthew Gott and
- Martin Köckerling
Beilstein J. Org. Chem. 2016, 12, 2478–2489, doi:10.3762/bjoc.12.242
- applicability of these compounds as possible 18F-building blocks, two biomolecules were modified and chosen for conjugation either using the Huisgen-click reaction or the traceless Staudinger ligation. Keywords: building blocks; coalescence; dynamic NMR; labeling; Staudinger ligation; Introduction The
- 5a serve as starting material (precursor) whereas fluorine compounds 4b and 5b function as appendant reference compounds to analyze the prospective 18F-containing compounds. The reaction pathway for all piperazines is illustrated in Scheme 1. Dynamic NMR studies During the full characterization of
Graphical Abstract
Scheme 1: Preparation of the nitro derivatives 4a and 5a and the fluorine-containing compounds 4b and 5b. Rea...
Figure 1: 1H NMR spectra of compound 3a measured in five different solvents: (A) CDCl3, (B) DMSO-d6, (C) acet...
Figure 2: HSQC and H,H-COSY (small spectrum) of compound 3a measured in CDCl3 at 25 °C. The independent coupl...
Figure 3: Illustration of the general partial double bond character of an amide bond and the limited isomeriz...
Figure 4: Temperature-dependent 1H NMR spectra of 3a measured in DMSO-d6 (aliphatic region of the piperazine ...
Figure 5: Molecular structure of compound 3a (ORTEP plot with 50% probability level).
Figure 6: Molecular structure of compound 4b (ORTEP plot with 50% probability level).
Figure 7: Superimposition fit of the two conformers, which exist in the ratio of 1:1 in the solid state struc...
Scheme 2: Peptide labeling using the Huisgen-click reaction and building block 4b. Reagents and conditions: a...
Scheme 3: The traceless Staudinger ligation to yield compound 9. Reagents and conditions: a) acetonitrile/wat...
Scheme 4: Preparation of the radiolabeling building blocks [18F]4b and [18F]5b. Reagents and conditions: a) K[...
Figure 8: Radio-TLC (eluent: ethanol) of [18F]5b (Rf = 0.50; reaction mixture).
Figure 9: (Radio)HPLC of 5a (tR = 7.7 min, UV trace, red), 5b (tR = 6.7 min, UV trace: blue) and [18F]5b (tR ...
First chemoenzymatic stereodivergent synthesis of both enantiomers of promethazine and ethopropazine
- Paweł Borowiecki,
- Daniel Paprocki and
- Maciej Dranka
Beilstein J. Org. Chem. 2014, 10, 3038–3055, doi:10.3762/bjoc.10.322
- due to the following facts: (i) It has been empirically confirmed by Latypov et al. [76] (as a result of dynamic NMR studies) that a final prevalent conformation in the CDA-substrate system in the case of MPA esters of secondary alcohols renders the sp rotamer, in which the methoxy group, the Cα
Graphical Abstract
Scheme 1: Chemoenzymatic synthesis of enantioenriched enantiomers of promethazine 9 and ethopropazine 10. Rea...
Figure 1: Dependence of optical purities (% ee) of (R)-(−)-6a (red curve, ■) and (S)-(+)-5 (blue curve, ▲) on...
Scheme 2: Assignment of the stereochemistry of enantiopure alcohol (+)-5 resulting from derivatization with (R...
Figure 2: Description of substituents for determination of the absolute configuration of (+)-5 and ΔδRS value...
Figure 3: 1H NMR (CDCl3, 400 MHz) spectra of the (R)-MPA 11 (red colored line) and (S)-MPA and 12 (blue color...
Figure 4: An ORTEP plot of (S)-(+)-1-(10H-phenothiazin-10-yl)propan-2-ol (S)-(+)-5. The following crystal str...
Scheme 3: Amination of optically active bromo derivatives (R)-(+)-8 or (S)-(−)-8 in toluene.
Scheme 4: Amination of optically active bromo derivatives (R)-(+)-8 or (S)-(−)-8 in methanol.
Scheme 5: The proposed reaction mechanism for amination of optically active (S)-(−)-8 in methanol.
An experimental and theoretical NMR study of NH-benzimidazoles in solution and in the solid state: proton transfer and tautomerism
- Carla I. Nieto,
- Pilar Cabildo,
- M. Ángeles García,
- Rosa M. Claramunt,
- Ibon Alkorta and
- José Elguero
Beilstein J. Org. Chem. 2014, 10, 1620–1629, doi:10.3762/bjoc.10.168
- four NH-benzimidazoles: 1 and 3 yielded average signals in DMSO-d6 and only in HMPA-d18 the prototropic exchange was slow, on the other hand 2 and 4 behaved as if the tautomerism was blocked in DMSO-d6. In the case of 1 a dynamic NMR (DNMR) study in HMPA-d18 was performed (Figure 6). The relevant data
Graphical Abstract
Figure 1: The five studied compounds.
Figure 2: Trimers A (left) and B (right) of 1.
Figure 3: The tautomerism of 1H-benzimidazole.
Figure 4: The 13C CPMAS NMR spectrum of 3.
Figure 5: The two independent molecules of 3 drawn with the Mercury program [26].
Figure 6: The evolution of the spectrum of 1 with temperature in HMPA-d18.
Thermodynamically stable [4 + 2] cycloadducts of lanthanum-encapsulated endohedral metallofullerenes
- Yuta Takano,
- Yuki Nagashima,
- M. Ángeles Herranz,
- Nazario Martín and
- Takeshi Akasaka
Beilstein J. Org. Chem. 2014, 10, 714–721, doi:10.3762/bjoc.10.65
- spectroscopic methods such as MALDI–TOF mass, optical absorption, and NMR spectroscopy. The [4 + 2] adducts of La2@C80 (3a,b, and 4a,b) and La@C82 (5b), respectively, retain diamagnetic and paramagnetic properties, as confirmed by EPR spectroscopy. Dynamic NMR measurements of 4a at various temperatures
- metallofullerene derivatives for the use in material science. Keywords: carbon nanomaterials; dynamic NMR; endofullerenes; La2@C80; La@C82; sultine; Introduction Endohedral metallofullerenes (EMFs) are a family of nanocarbons, which encapsulated one or more metal atoms inside a hollow carbon cage [1][2][3][4
Graphical Abstract
Scheme 1: Synthesis of [4 + 2] adducts of La2@C80.
Figure 1: HPLC profiles of the reaction solutions (black) before and (red) after the reaction of La2@C80 and ...
Figure 2: MALDI–TOF mass (negative mode) spectra of (a) 3b and (b) 4b, using 1,1,4,4-tetraphenyl-1,3-butadien...
Figure 3: UV–vis/near-IR absorption spectra of 3b and 4b recorded by the diode array detector of the HPLC app...
Figure 4: MALDI–TOF mass spectrum (negative mode) of the reaction mixture from La2@C80 and 1a, using 1,1,4,4-...
Figure 5: 1H NMR spectra of (a) the mixture of 3a and 4a in C2D2Cl4 at 248 K, and (b) isolated 4a at 230 K, r...
Figure 6: HPLC profiles of the mixture of 3a and 4a, (a) after heating in refluxing 1,2-dichlorobenzene and (...
Figure 7: HPLC profiles of the reaction mixture of 3b and 4b, (black) before and (red) after heating in reflu...
Figure 8: UV–vis/near-IR absorption spectra of 3b and 4a in toluene.
Figure 9: Temperature-dependent 1H NMR spectra of 4a in C2D2Cl4 (left) at 300 MHz, and (right) at 500 MHz for...
Scheme 2: Synthesis of [4 + 2] adducts of La@C82.
Figure 10: HPLC profiles of the reaction mixture for 5b. Conditions: column, Buckyprep (Ø 4.6 mm × 250 mm); el...
Figure 11: MALDI–TOF mass spectra (negative mode) of 5b, using 1,1,4,4-tetraphenyl-1,3-butadiene as matrix.
Figure 12: Vis–near-IR spectra of 5b, 6 and La@C82 in CS2.
Figure 13: 1H NMR spectrum of [5b]− in acetone-d6/CS2 (3/1 = v/v) at 223 K.
Figure 14: 13C NMR spectrum of [5b]− in acetone-d6/CS2 (3/1 = v/v).
Figure 15: HPLC profiles for comparison of the thermal stabilities of (a) 5b and (b) 6 at 30 °C. Conditions: c...
Chromatographically separable rotamers of an unhindered amide
- Mario Geffe,
- Lars Andernach,
- Oliver Trapp and
- Till Opatz
Beilstein J. Org. Chem. 2014, 10, 701–706, doi:10.3762/bjoc.10.63
- pure form by crystallization. While Rice and Brossi focused on the optical and crystallographic properties of these compounds, Szántay et al. gave a first estimate of the activation energy of the interconversion of these two rotamers based on dynamic NMR spectroscopy at variable temperature. They
- deduced a value of 94 kJ/mol from a coalescence temperature of 170 °C but did not provide crucial data such as the spectrometer frequency required for the calculation. Sulima et al. reported a rotational barrier of 92 kJ/mol for 1-bromo-N-formyl-4-hydroxy-3-methoxymorphinan-6-one based on dynamic NMR
- quantitatively by refluxing 3 in ethyl formate (Scheme 1). Dynamic NMR (DNMR) measurements (400 MHz) on a sample of 4 in DMSO-d6 at temperatures ranging from 20 °C to 150 °C, the upper limit for technical reasons, showed no signs of beginning coalescence of the formyl proton resonances even at the highest
Graphical Abstract
Scheme 1: Synthesis of formamide 4. Reagents and conditions: a) KHMDS, THF, −78 °C; then: NaBH4, MeOH, 63%. b...
Figure 1: Equilibration of the Z-rotamer of 4 at 293 K.
Figure 2: Equilibration of the E-rotamer of 4 at 293 K.
Figure 3: Elution profiles obtained by temperature-dependent DHPLC measurements of 4.
Figure 4: Eyring plot obtained by temperature dependent DHPLC measurements of 4.
Figure 5:
Potential energy surface scan graph for the dihedral angle O–C–N–C1 (![[Graphic 2]](/bjoc/content/inline/1860-5397-10-63-i3.png?max-width=637&scale=1.18182)
) in 4 (BP-D3/def2-SVP).
Figure 6: Energy differences and geometries for E- and Z-4 and both transition states (TS1 and TS2) in hexane...
Structure of 1,5-benzodiazepinones in the solid state and in solution: Effect of the fluorination in the six-membered ring
- Marta Pérez-Torralba,
- Rosa M. Claramunt,
- M. Ángeles García,
- Concepción López,
- M. Carmen Torralba,
- M. Rosario Torres,
- Ibon Alkorta and
- José Elguero
Beilstein J. Org. Chem. 2013, 9, 2156–2167, doi:10.3762/bjoc.9.253
- studies at the B3LYP/6-311++G(d,p) level were carried out on these compounds and on four non-fluorinated derivatives, allowing to calculate geometries, tautomeric energies and ring-inversion barriers, that were compared with the experimental results obtained by static and dynamic NMR in solution and in
Graphical Abstract
Figure 1: The six 1,5-benzodiazepinones discussed in this paper together with clobazam.
Scheme 1: Synthesis of compounds 1 and 2.
Figure 2: The X-ray structures of 3a (TUPSAZ), 5a (EFARUA). In TUPSAZ there is a disordered water molecule.
Figure 3: ORTEP plot (30% probability) of 1, showing the X-ray labeling of the asymmetric unit.
Figure 4: View of the zigzag chain formed in 1, showing the H-bond and F–F interactions.
Figure 5: ORTEP plot (20% probability) of 2, showing the X-ray labeling of the asymmetric unit.
Figure 6: Packing of 2 showing the F–F contacts along the chain (orange) and the π–π interactions that form t...
Figure 7: The different tautomers in the 1H and 1-methyl series.
Figure 8: 2-Methoxy-4-methyl-3H-1,5-benzodiazepine (7).
Figure 9: 1H–19F coupling constant values either through-bond or through-space.
Figure 10: The optimized geometry of the TS of 2a inversion.
Figure 11: Equations used to transform absolute shieldings into chemical shifts [38,39].
The chemistry of bisallenes
- Henning Hopf and
- Georgios Markopoulos
Beilstein J. Org. Chem. 2012, 8, 1936–1998, doi:10.3762/bjoc.8.225
Graphical Abstract
Figure 1: Loschmidt’s structure proposal for benzene (1) (Scheme 181 from [3]) and the corresponding modern stru...
Figure 2: The first isolated bisallenes.
Figure 3: Carbon skeletons of selected bisallenes discussed in this review.
Scheme 1: The preparation of 1,2,4,5-hexatetraene (2).
Scheme 2: The preparation of a conjugated bisallene by the DMS-protocol.
Scheme 3: Preparation of the 3-deuterio- and 3,4-dideuterio derivatives of 24.
Scheme 4: A versatile method to prepare alkylated conjugated bisallenes and other allenes.
Scheme 5: A preparation of 3,4-dimethyl-1,2,4,5-hexatetraene (38).
Scheme 6: A (C6 + 0)-approach to 1,2,4,5-hexatetraene (2).
Scheme 7: The preparation of a fully alkylated bisallenes from a 2,4-hexadiyne-1,6-diol diacetate.
Scheme 8: The preparation of the first phenyl-substituted conjugated bisallenes 3 and 4.
Scheme 9: Selective hydrogenation of [5]cumulenes to conjugated bisallenes: another (C6 + 0)-route.
Scheme 10: Aryl-substituted conjugated bisallenes by a (C3 + C3)-approach.
Scheme 11: Hexaphenyl-1,2,4,5-hexatetraene (59) by a (C3 + C3)-approach.
Scheme 12: An allenation route to conjugated bisallenes.
Scheme 13: The preparation of 3,4-difunctionalized conjugated bisallenes.
Scheme 14: Problems during the preparation of sulfur-substituted conjugated bisallenes.
Scheme 15: The preparation of 3,4-dibromo bisallenes.
Scheme 16: Generation of allenolates by an oxy-Cope rearrangement.
Scheme 17: A linear trimerization of alkynes to conjugated bisallenes: a (C2 + C2 + C2)-protocol.
Scheme 18: Preparation of a TMS-substituted conjugated bisallene by a C3-dimerization route.
Scheme 19: A bis(trimethylsilyl)bisallene by a C3-coupling protocol.
Scheme 20: The rearrangement of highly substituted benzene derivatives into their conjugated bisallenic isomer...
Scheme 21: From fully substituted benzene derivatives to fully substituted bisallenes.
Scheme 22: From a bicyclopropenyl to a conjugated bisallene derivative.
Scheme 23: The conversion of a bismethylenecyclobutene into a conjugated bisallene.
Scheme 24: The preparation of monofunctionalized bisallenes.
Scheme 25: Preparation of bisallene diols and their cyclization to dihydrofurans.
Scheme 26: A 3,4-difunctionalized conjugated bisallene by a C3-coupling process.
Scheme 27: Preparation of a bisallenic diketone by a coupling reaction.
Scheme 28: Sulfur and selenium-substituted bisallenes by a [2.3]sigmatropic rearrangement.
Scheme 29: The biallenylation of azetidinones.
Scheme 30: The preparation of a fully ferrocenylated conjugated bisallene.
Scheme 31: The first isomerization of a 1,5-hexadiyne to a 1,2,4,5-hexatetraene.
Scheme 32: The preparation of alkynyl-substituted bisallenes by a C3-dimerization protocol.
Scheme 33: Preparation of another completely ferrocenylated bisallene.
Scheme 34: The cyclization of 1,5-hexadiyne (129) to 3,4-bismethylenecyclobutene (130) via 1,2,4,5-hexatetraen...
Scheme 35: Stereochemistry of the thermal cyclization of bisallenes to bismethylenecyclobutenes.
Scheme 36: Bisallene→bismethylenecyclobutene ring closures in the solid state.
Scheme 37: A bisallene cyclization/dimerization reaction.
Scheme 38: A selection of Diels–Alder additions of 1,2,4,5-hexatetraene with various double-bond dienophiles.
Scheme 39: The stereochemistry of the [2 + 4] cycloaddition to conjugated bisallenes.
Scheme 40: Preparation of azetidinone derivatives from conjugated bisallenes.
Scheme 41: Cycloaddition of heterodienophiles to a conjugated bisallene.
Scheme 42: Addition of triple-bond dienophiles to conjugated bisallenes.
Scheme 43: Sulfur dioxide addition to conjugated bisallenes.
Scheme 44: The addition of a germylene to a conjugated bisallene.
Scheme 45: Trapping of conjugated bisallenes with phosphinidenes.
Scheme 46: The cyclopropanantion of 1,2,4,5-hexatetraene (2).
Scheme 47: Photochemical reactions involving conjugated bisallenes.
Scheme 48: Base-catalyzed isomerizations of conjugated bisallenes.
Scheme 49: Ionic additions to a conjugated bisallene.
Scheme 50: Oxidation reactions of a conjugated bisallene.
Scheme 51: The mechanism of oxidation of the bisallene 24.
Scheme 52: CuCl-catalyzed cyclization of 1,2,4,5-hexatetraene (2).
Scheme 53: The conversion of conjugated bisallenes into cyclopentenones.
Scheme 54: Oligomerization of a conjugated bisallene by nickel catalysts.
Scheme 55: Generation of 1,2,5,6-heptatetraene (229) as a reaction intermediate.
Scheme 56: The preparation of a stable derivative of 1,2,5,6-heptatetraene.
Scheme 57: A bisallene with a carbonyl group as a spacer element.
Scheme 58: The first preparation of 1,2,6,7-octatetraene (242).
Scheme 59: Preparation of 1,2,6,7-octatetraenes by (C4 + C4)-coupling of enynes.
Scheme 60: Preparation of 1,2,6,7-octatetraenes by (C4 + C4)-coupling of homoallenyl bromides.
Scheme 61: Preparation of 1,2,6,7-octatetraenes by alkylation of propargylic substrates.
Scheme 62: Preparation of two highly functionalized 1,2,6,7-octatetraenes.
Scheme 63: Preparation of several higher α,ω-bisallenes.
Scheme 64: Preparation of different alkyl derivatives of α,ω-bisallenes.
Scheme 65: The preparation of functionalized 1,2,7,8-nonatetraene derivatives.
Scheme 66: Preparation of functionalized α,ω-bisallenes.
Scheme 67: The preparation of an α,ω-bisallene by direct homologation of an α,ω-bisalkyne.
Scheme 68: The gas-phase pyrolysis of 4,4-dimethyl-1,2,5,6-heptatetraene (237).
Scheme 69: Gas-phase pyrolysis of 1,2,6,7-octatetraene (242).
Scheme 70: The cyclopropanation of 1,2,6,7-octatetraene (242).
Scheme 71: Intramolecular cyclization of 1,2,6,7-octatetraene derivatives.
Scheme 72: The gas-phase pyrolysis of 1,2,7,8-nonatetraene (265) and 1,2,8,9-decatetraene (266).
Scheme 73: Rh-catalyzed cyclization of a functionalized 1,2,7,8-nonatetraene.
Scheme 74: A triple cyclization involving two different allenic substrates.
Scheme 75: Bicyclization of keto derivatives of 1,2,7,8-nonatetraene.
Scheme 76: The preparation of complex organic compounds from functionalized bisallenes.
Scheme 77: Cycloisomerization of an α,ω-bisallene containing a C9 tether.
Scheme 78: Organoborane polymers from α,ω-bisallenes.
Scheme 79: Preparation of trans- (337) and cis-1,2,4,6,7-octapentaene (341).
Scheme 80: The preparation of 4-methylene-1,2,5,6-heptatetraene (349).
Scheme 81: The preparation of acetylenic bisallenes.
Scheme 82: The preparation of derivatives of hydrocarbon 351.
Scheme 83: The construction of macrocyclic alleno-acetylenes.
Scheme 84: Preparation and reactions of 4,5-bismethylene-1,2,6,7-octatetraene (365).
Scheme 85: Preparation of 1,2-bis(propadienyl)benzene (370).
Scheme 86: The preparation of 1,4-bis(propadienyl)benzene (376).
Scheme 87: The preparation of aromatic and heteroaromatic bisallenes by metal-mediated coupling reactions.
Scheme 88: Double cyclization of an aromatic bisallene.
Scheme 89: Preparation of an allenic [15]paracyclophane by a ring-closing metathesis reaction of an aromatic α...
Scheme 90: Preparation of a macrocyclic ring system containing 1,4-bis(propadienyl)benzene units.
Scheme 91: Preparation of copolymers from 1,4-bis(propadienyl)benzene (376).
Scheme 92: A boration/copolymerization sequence of an aromatic bisallene and an aromatic bisacetylene.
Scheme 93: Formation of a layered aromatic bisallene.
Figure 4: The first members of the semicyclic bisallene series.
Scheme 94: Preparation of the first bis(vinylidene)cyclobutane derivative.
Scheme 95: Dimerization of strain-activated cumulenes to bis(vinylidene)cyclobutanes.
Scheme 96: Photodimerization of two fully substituted butatrienes in the solid state.
Scheme 97: Preparation of the two parent bis(vinylidene)cyclobutanes.
Scheme 98: The preparation of 1,3-bis(vinylidene)cyclopentane and its thermal isomerization.
Scheme 99: The preparation of the isomeric bis(vinylidene)cyclohexanes.
Scheme 100: Bi- and tricyclic conjugated bisallenes.
Scheme 101: A selection of polycyclic bisallenes.
Scheme 102: The first endocyclic bisallenes.
Figure 5: The stereochemistry of 1,2,6,7-cyclodecatetraene.
Scheme 103: The preparation of several endocyclic bisallenes.
Scheme 104: Synthesis of diastereomeric derivatives of 1,2,6,7-cyclodecatetraene.
Scheme 105: Preparation of a derivative of 1,2,8,9-cyclotetradecatetraene.
Scheme 106: The preparation of keto derivatives of cyclic bisallenes.
Scheme 107: The preparation of cyclic biscumulenic ring systems.
Scheme 108: Cyclic bisallenes in natural- and non-natural-product chemistry.
Scheme 109: The preparation of iron carbonyl complexes from cyclic bisallenes.
Figure 6: A selection of unknown exocyclic bisallenes that should have interesting chemical properties.
Scheme 110: The thermal isomerization of 1,2-diethynylcyclopropanes and -cyclobutanes.
Scheme 111: Intermediate generation of a cyclooctapentaene.
Scheme 112: Attempted preparation of a cyclodecahexaene.
Scheme 113: The thermal isomerization of 1,5,9-cyclododecatriyne (511) into [6]radialene (514).
Scheme 114: An isomerization involving a diketone derived from a conjugated bisallene.
Scheme 115: Typical reaction modes of heteroorganic bisallenes.
Scheme 116: Generation and thermal behavior of acyclic hetero-organic bisallenes.
Scheme 117: Generation of bis(propadienyl)thioether.
Scheme 118: The preparation of a bisallenic sulfone and its thermal isomerization.
Scheme 119: Bromination of the bisallenic sulfone 535.
Scheme 120: Metalation/hydrolysis of the bisallenic sulfone 535.
Scheme 121: Aromatic compounds from hetero bisallenes.
Scheme 122: Isomerization/cyclization of bispropargylic ethers.
Scheme 123: The preparation of novel aromatic systems by base-catalyzed isomerization of bispropargyl ethers.
Scheme 124: The isomerization of bisacetylenic thioethers to bicyclic thiophenes.
Scheme 125: Aromatization of macrocyclic bispropargylic sulfides.
Scheme 126: Preparation of ansa-compounds from macrocyclic bispropargyl thioethers.
Scheme 127: Alternate route for cyclization of a heterorganic bisallene.
Scheme 128: Multiple isomerization/cyclization of “double” bispropargylic thioethers.
Scheme 129: Preparation of a bisallenyl disulfide and its subsequent bicyclization.
Scheme 130: Thermal cyclization of a bisallenyl thiosulfonate.
Scheme 131: Some reactions of heteroorganic bisallenes with two sulfur atoms.
Scheme 132: Further methods for the preparation of heteroorganic bisallenes.
Scheme 133: Cyclization reactions of heteroorganic bisallenes.
Scheme 134: Thermal cycloadditions of bisallenic tertiary amines.
Scheme 135: Cyclization of a bisallenic tertiary amine in the presence of a transition-metal catalyst.
Scheme 136: A Pauson–Khand reaction of a bisallenic ether.
Scheme 137: Formation of a 2:1adduct from two allenic substrates.
Scheme 138: A ring-forming silastannylation of a bisallenic tertiary amine.
Scheme 139: A three-component cyclization involving a heterorganic bisallene.
Scheme 140: Atom-economic construction of a complex organic framework from a heterorganic α,ω-bisallene.
On the mechanism of action of gated molecular baskets: The synchronicity of the revolving motion of gates and in/out trafficking of guests
- Keith Hermann,
- Stephen Rieth,
- Hashem A. Taha,
- Bao-Yu Wang,
- Christopher M. Hadad and
- Jovica D. Badjić
Beilstein J. Org. Chem. 2012, 8, 90–99, doi:10.3762/bjoc.8.9
- the basket: Specifically, the greater the affinity of the guest for occupying the basket, the less effective the gates are in “sweeping” the guest as the gates undergo their revolving motion. Keywords: dynamic NMR; host–guest chemistry; linear free-energy relationships; molecular encapsulation
- ΔG‡rac (i.e., opening and closing, see below in Figure 6) reveals a systematic disparity (ΔG° + ΔG‡rac + ΔG‡sterics ≠ ΔG‡out, see below in Figure 7). In order to address this conundrum, we have employed methods of experimental (dynamic NMR) and computational chemistry (steered molecular dynamics, SMD
- rise to two enantiomeric conformers 1A and 1B (Figure 7A). The interconversion kinetics of the 1A/B racemization can be followed by dynamic NMR spectroscopy in which a singlet corresponding to Ha/Hb nuclei at high temperatures is seen to split into two doublets at low temperatures. In particular, the
Graphical Abstract
Figure 1: Chemical structure of gated molecular basket 1 and 1,1,1-trichloroethane (2). Electrostatic potenti...
Figure 2: (Left): 1H NMR spectra (400 MHZ, CD2Cl2) of 1 (0.67 mM) obtained upon incremental addition of 1,1,1...
Figure 3: Chemically equivalent CH3 protons (black) in 1,1,1-trichloroethane (2) alter their magnetic environ...
Figure 4: Nonlinear least-squares fitting (SigmaPlot) of magnetization rate constants k*in (2-D EXSY, 250.0 ±...
Figure 5: (A): Nonlinear least-squares fitting of 1H NMR signal intensities (Iin/out) of [CH3CCl3]in/out as f...
Figure 6: (A) Four different trajectories were used for examining the departure of CH3CCl3 guest from basket 1...
Figure 7: (A) The interconversion of conformational enantiomers 1A and 1B, having anticlockwise and clockwise...
Figure 8: The departure of CH3CCl3 from 1A–CH3CCl3 gives rise to the less stable 1–CD2Cl2, which upon entrapm...
Figure 9: (A): Kinetic and thermodynamic parameters [13,14] characterizing the departure of isosteric guests 3–7 fro...
(Pseudo)amide-linked oligosaccharide mimetics: molecular recognition and supramolecular properties
- José L. Jiménez Blanco,
- Fernando Ortega-Caballero,
- Carmen Ortiz Mellet and
- José M. García Fernández
Beilstein J. Org. Chem. 2010, 6, No. 20, doi:10.3762/bjoc.6.20
- points are incorporated by inserting building blocks bearing orthogonal amine functionalities at specific locations in the chain [86]. Conformational studies by dynamic NMR spectroscopy of β-(1→3)- and β-(1→6)-linked diglucosylthioureas (e.g. 41) detected the presence of Z,Z and Z,E conformers at the N
Graphical Abstract
Figure 1: Schematic representation of sugar aminoacids (SAAs) and (pseudo)amide oligosaccharide mimetics.
Figure 2: Natural SAAs structures and natural nucleosidic antibiotics.
Scheme 1: Synthetic route to the target amide-linked sialooligomers. (a) Fmoc-Cl, NaHCO3, H2O, dioxane, 0 °C....
Figure 3: The general structure of glycoamino acids and their corresponding oligomers.
Figure 4: Conformational analysis of the β(1→2)-amide-linked glucooligomer 9.
Figure 5: Short oligomeric chains of C-glycosyl D-arabino THF amino acid oligomers.
Figure 6: (A) Stereoview of the minimized structure of compound 16 (produced by a 500 ps simulation) that mos...
Figure 7: Structures of linear oxetane-β- and δ-SAA homo-oligomers 19–20.
Figure 8: 10-Membered ring H-bonds in compound 21 consistent with NMR and modelling investigations.
Figure 9: General structure of carbopeptoid-oligonucleotide conjugates.
Figure 10: Protected derivatives of 2,6-diamino-2,6-dideoxy-β-D-glucopyranosyl carboxylic acid 22 and 23.
Figure 11: Cyclic homo-oligomers containing glucopyranoid-SAAs.
Scheme 2: Strategy for solid-phase synthesis of cyclic trimers and tetramers containing pyranoid δ-SAAs.
Figure 12: Cyclic tetramers of L-rhamno- and D-gulo-configured oxetane-SAAs.
Figure 13: Aminoglycosidic antibiotics of the glycocinnamoylspermidine family.
Scheme 3: Synthesis of (thio)trehazoline, via triflate, from β-hydroxy(thio)urea.
Figure 14: Approaches to access pseudoamide-type oligosaccharide mimics.
Figure 15: Calystegine B2 analogues 38 and 39 with urea-linked disaccharide structure.
Figure 16: Rotameric equilibrium shift of 40 by formation of a bidentate hydrogen bond.
Figure 17: Nucleotide analogues with thiourea and S-methylisothiouronium linkers.
Scheme 4: Retrosynthetic approach to synthesize thiourea-linked glycooligomers.
Figure 18: Rotameric equilibria for β-(1→6)-thiourea-linked glucodimer 41.
Figure 19: Schematic representation of (a) cyclodextrin (CDs) and (b) cyclotrehalan (CTs) family members.
Scheme 5: Synthesis of guanidine-linked pseudodisaccharides via carbodiimide.
Figure 20: β(1→6)-Guanidine-linked pseudodi- and pseudotrisaccharides 47 and 48.
Scheme 6: Synthesis of N-benzylguanidine-linked CT2 50.
Figure 21: Structure of RNG and DNG.
Figure 22: Preparation of Fmoc-guanidinium derivatives.
Figure 23: Structures of the homo-oligomeric RNG derivatives 51–55.
Figure 24: Phosphoramidite building block 56.
Figure 25: Structures of DNGs 57–65.
Figure 26: Structure of the phosphoramidite building block 66.
[3.3]Dithia-bridged cyclophanes featuring a thienothiophene ring: synthesis, structures and conformational analysis
- Sabir H. Mashraqui,
- Yogesh Sanghvikar,
- Shailesh Ghadhigaonkar,
- Sukeerthi Kumar,
- Auke Meetsma and
- Elise Trân Huu Dâu
Beilstein J. Org. Chem. 2009, 5, No. 74, doi:10.3762/bjoc.5.74
- ]dithia-bridged cyclophanes; dynamic NMR analysis; thieno[2,3-b]thiophene; X-ray crystal structure; Introduction The synthesis, molecular structures and conformational dynamics of short-bridged cyclophanes continue to engage interest in supramolecular chemistry [1][2][3][4]. The study of the
Graphical Abstract
Figure 1: Conformationally flexible 3, 4-bridged dithia-thienothiophenophanes.
Scheme 1: Synthetic scheme for compounds 7, 9 and 11.
Figure 2: ORTEP plot of the crystal structure of 11. Important parameters: Bond length (Å) : C8–C9 = 1.492, C...
Scheme 2: Computed three most stable conformations of 11 and their calculated energies.
