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Search for "Schiff base" in Full Text gives 84 result(s) in Beilstein Journal of Organic Chemistry.
Stereoselective synthesis and transformation of pinane-based 2-amino-1,3-diols
- Ákos Bajtel,
- Mounir Raji,
- Matti Haukka,
- Ferenc Fülöp and
- Zsolt Szakonyi
Beilstein J. Org. Chem. 2021, 17, 983–990, doi:10.3762/bjoc.17.80
- (LAH) reduction of both 9 and 12 gave the same N-methylaminodiol 14 with modest yield (Scheme 3). Subsequently, compound 13 was reacted with benzaldehyde. In this process, the Schiff' base 15A was generated in situ. Our efforts to reduce it with sodium borohydride failed, since we did not observe the
- tautomeric mixture containing condensed oxazolidine 15E as the main component. Additional minor components included the other condensed oxazolidine (15D), spiro compounds 15B and 15C as well as the Schiff’ base 15A existing in a ratio of 15A/15B/15C/15D/15E = 4:<1:4:12:79 (Scheme 4) [39][40]. The structures
Graphical Abstract
Figure 1: Biologically active 2-amino-1,3-diols.
Scheme 1: Stereoselective synthesis of the pinane-fused oxazolidin-2-one 9.
Figure 2: NOESY experiments and X-ray structure elucidation of oxazolidin-2-one 9.
Scheme 2: Stereoselective synthesis of the pinane spiro-fused oxazolidin-2-one 12.
Scheme 3: Parallel synthesis of 2-amino-1,3-diols.
Scheme 4: Synthesis of N-benzyl-2-amino-1,3-diol 16.
Scheme 5: Synthesis of 2-amino-1,3-diols.
Figure 3: NOESY experiments and X-ray structure proofment of the structure of oxazolidine 17.
Scheme 6: Synthesis of 2-phenyliminooxazolidines.
Figure 4: Proposed pathway for the ring–ring tautomerism.
Chiral isothiourea-catalyzed kinetic resolution of 4-hydroxy[2.2]paracyclophane
- David Weinzierl and
- Mario Waser
Beilstein J. Org. Chem. 2021, 17, 800–804, doi:10.3762/bjoc.17.68
- access 2 in an enantioenriched fashion have been developed. One commonly used method relies on the resolution of 4-formyl[2.2]paracyclophane via formation of a chiral Schiff base first, followed by a subsequent Dakin-type oxidation to alcohol 2 [18]. Alternatively, the direct resolution of rac-2 via
Graphical Abstract
Scheme 1: Overview about established methods to access enantioenriched 2 and the herein investigated kinetic ...
Scheme 2: Use of alternative acylating agents 4 for the kinetic resolution of rac-2.
Styryl-based new organic chromophores bearing free amino and azomethine groups: synthesis, photophysical, NLO, and thermal properties
- Anka Utama Putra,
- Deniz Çakmaz,
- Nurgül Seferoğlu,
- Alberto Barsella and
- Zeynel Seferoğlu
Beilstein J. Org. Chem. 2020, 16, 2282–2296, doi:10.3762/bjoc.16.189
- Optics and Nanophotonics, IPCMS, UMR CNRS, 7504, 67034 Strasbourg Cedex 2, France 10.3762/bjoc.16.189 Abstract Herein we report the synthesis and characterization of a new series of styryl-based push-pull dyes containing a free amino group and their Schiff base derivatives. The dyes include the
- dyes bearing the julolidine donor as 1430 × 10−48 esu (for free amino derivative) and 1950 × 10−48 esu (for Schiff base derivative), respectively. The structural and electronic properties of the dyes as well as their NLO properties were further studied using DFT calculations. The thermal stabilities of
- all dyes were evaluated by thermogravimetric analysis (TGA). The TGA data showed that all dyes were thermally stable up to 250 °C. Keywords: DFT calculations; NLO; pH sensitive dyes; Schiff base; solvent effect; styryl dyes; Introduction Push-pull organic molecules are a class of organic dyes
Graphical Abstract
Scheme 1: Synthetic pathways of dyes 3–7 and Schiff base analogs 8–12.
Figure 1: The optimized geometry of dyes 3 and 8.
Figure 2: Absorption spectra of dyes 3 (a, left) and 8 (b, right). Inset: Color of dyes 3 and 8 in the given ...
Figure 3: Emission spectra of dyes 3 (a, left) and 8 (b, right). Inset: Color of dyes 3 and 8 in the indicate...
Figure 4: Red shift phenomena with changing substituents in absorption (a, left) and emission (b, right) spec...
Figure 5: Absorption (a, left) and emission (b, right) change of dye 12 upon addition of 15 equiv of TBAOH an...
Figure 6: Photographs of dye 12 (left, ambient light), without, after the addition of 15 equiv of TBAOH (midd...
Figure 7: Absorption (a, left) and emission (b, right) change of 8 in Britton–Robinson buffer solutions at di...
Figure 8: Photographs of dye 8 in Britton–Robinson buffer solutions at different pH values.
Figure 9: Sigmoid function obtained from dye 8 UV–vis absorption spectra during pH investigation.
Figure 10: TGA curves of all synthetized dyes.
Microwave-assisted efficient one-pot synthesis of N2-(tetrazol-5-yl)-6-aryl/heteroaryl-5,6-dihydro-1,3,5-triazine-2,4-diamines
- Moustafa Sherief Moustafa,
- Ramadan Ahmed Mekheimer,
- Saleh Mohammed Al-Mousawi,
- Mohamed Abd-Elmonem,
- Hesham El-Zorba,
- Afaf Mohamed Abdel Hameed,
- Tahany Mahmoud Mohamed and
- Kamal Usef Sadek
Beilstein J. Org. Chem. 2020, 16, 1706–1712, doi:10.3762/bjoc.16.142
- cyanoguanidine 5 to the formed Schiff’s base (route c). Product 4 was the sole isolable product as under reflux in pyridine as base, compound 8 well undergoes a Dimroth rearrangement forming the more thermodynamically stable product 4 [33]. We established route c, as the formation of the Schiff base is more
Graphical Abstract
Scheme 1: Previously reported methods for the synthesis of 1,3,5-triazine-2,4-diamine derivatives.
Scheme 2: One-pot synthesis of N2-(tetrazol-5-yl)-6-aryl/heteroaryl-5,6-dihydro-1,3,5-triazine-2,4-diamines 4a...
Figure 1: ORTEP diagram of compound 4i.
Scheme 3: Plausible different routes to account for the formation of products 4.
Copper catalysis with redox-active ligands
- Agnideep Das,
- Yufeng Ren,
- Cheriehan Hessin and
- Marine Desage-El Murr
Beilstein J. Org. Chem. 2020, 16, 858–870, doi:10.3762/bjoc.16.77
- reports on copper complexes of the redox-active Schiff-base isatin bearing various functional groups (Scheme 4) [19]. The main feature of these ligands is their ability to form four distinct and well-defined types of complexes depending on the reaction conditions (i.e., the number of equivalents of metal
Graphical Abstract
Scheme 1: Copper complexes with amidophenolate type benzoxazole ligands for alcohol oxidations.
Scheme 2: Copper-catalyzed aerobic oxidation of alcohols and representative substrate scope.
Scheme 3: Introduction of H-bonding network in the ligand coordination sphere.
Scheme 4: Well-defined isatin copper complexes.
Scheme 5: Catalyst control in the biomimetic phenol ortho-oxidation.
Scheme 6: Structural diversity accessible by direct functionalization.
Scheme 7: Copper-catalyzed trifluoromethylation of heteroaromatics with redox-active iminosemiquinone ligands....
Scheme 8: Reversal of helical chirality upon redox stimuli and enantioselective Michael addition with a redox...
Scheme 9: Interaction of guanidine-copper catalyst with oxygen and representative coupling products. a4 mol %...
Scheme 10: Access to 1,2-oxy-aminoarenes by copper-catalyzed phenol–amine coupling.
Scheme 11: Copper-catalyzed aziridination through molecular spin catalysis with redox-active iminosemiquinone ...
Scheme 12: Nitrogen-group and carbon-group transfer in copper-catalyzed aziridination and cyclopropanation thr...
A systematic review on silica-, carbon-, and magnetic materials-supported copper species as efficient heterogeneous nanocatalysts in “click” reactions
- Pezhman Shiri and
- Jasem Aboonajmi
Beilstein J. Org. Chem. 2020, 16, 551–586, doi:10.3762/bjoc.16.52
- ligand was attached on reversed-phase 3-aminopropyl-functionalized silica gel (APSi) in dichloromethane as a solvent. The complexation reaction of the resulting Schiff base, named iminopropyl-functionalized silica gel (IPSi), with [Cu(CH3CN)4]PF6 and CuSO4 produced Cu(I)@IPSi (1a) and Cu(II)@IPSi (1b
Graphical Abstract
Scheme 1: Chemical structure of the catalysts 1a and 1b and their catalytic application in CuAAC reactions.
Scheme 2: Synthetic route to the catalyst 11 and its catalytic application in CuAAC reactions.
Scheme 3: Synthetic route of dendrons, illustrated using G2-AMP 23.
Scheme 4: The catalytic application of CuYAu–Gx-AAA–SBA-15 in a CuAAC reaction.
Scheme 5: Synthetic route to the catalyst 36.
Scheme 6: Application of the catalyst 36 in CuAAC reactions.
Scheme 7: The synthetic route to the catalyst 45 and catalytic application of 45 in “click” reactions.
Scheme 8: Synthetic route to the catalyst 48 and catalytic application of 48 in “click” reactions.
Scheme 9: Synthetic route to the catalyst 58 and catalytic application of 58 in “click” reactions.
Scheme 10: Synthetic route to the catalyst 64 and catalytic application of 64 in “click” reactions.
Scheme 11: Chemical structure of the catalyst 68 and catalytic application of 68 in “click” reactions.
Scheme 12: Chemical structure of the catalyst 69 and catalytic application of 69 in “click” reactions.
Scheme 13: Synthetic route to, and chemical structure of the catalyst 74.
Scheme 14: Application of the cayalyst 74 in “click” reactions.
Scheme 15: Synthetic route to, and chemical structure of the catalyst 78 and catalytic application of 78 in “c...
Scheme 16: Synthetic route to the catalyst 85.
Scheme 17: Application of the catalyst 85 in “click” reactions.
Scheme 18: Synthetic route to the catalyst 87 and catalytic application of 87 in “click” reactions.
Scheme 19: Chemical structure of the catalyst 88 and catalytic application of 88 in “click” reactions.
Scheme 20: Synthetic route to the catalyst 90 and catalytic application of 90 in “click” reactions.
Scheme 21: Synthetic route to the catalyst 96 and catalytic application of 96 in “click” reactions.
Scheme 22: Synthetic route to the catalyst 100 and catalytic application of 100 in “click” reactions.
Scheme 23: Synthetic route to the catalyst 102 and catalytic application of 23 in “click” reactions.
Scheme 24: Synthetic route to the catalysts 108–111.
Scheme 25: Catalytic application of 108–111 in “click” reactions.
Scheme 26: Synthetic route to the catalyst 121 and catalytic application of 121 in “click” reactions.
Scheme 27: Synthetic route to 125 and application of 125 in “click” reactions.
Scheme 28: Synthetic route to the catalyst 131 and catalytic application of 131 in “click” reactions.
Scheme 29: Synthetic route to the catalyst 136.
Scheme 30: Application of the catalyst 136 in “click” reactions.
Scheme 31: Synthetic route to the catalyst 141 and catalytic application of 141 in “click” reactions.
Scheme 32: Synthetic route to the catalyst 144 and catalytic application of 144 in “click” reactions.
Scheme 33: Synthetic route to the catalyst 149 and catalytic application of 149 in “click” reactions.
Scheme 34: Synthetic route to the catalyst 153 and catalytic application of 153 in “click” reactions.
Scheme 35: Synthetic route to the catalyst 155 and catalytic application of 155 in “click” reactions.
Scheme 36: Synthetic route to the catalyst 157 and catalytic application of 157 in “click” reactions.
Scheme 37: Synthetic route to the catalyst 162.
Scheme 38: Application of the catalyst 162 in “click” reactions.
Scheme 39: Synthetic route to the catalyst 167 and catalytic application of 167 in “click” reactions.
Scheme 40: Synthetic route to the catalyst 169 and catalytic application of 169 in “click” reactions.
Scheme 41: Synthetic route to the catalyst 172.
Scheme 42: Application of the catalyst 172 in “click” reactions.
Architecture and synthesis of P,N-heterocyclic phosphine ligands
- Wisdom A. Munzeiwa,
- Bernard Omondi and
- Vincent O. Nyamori
Beilstein J. Org. Chem. 2020, 16, 362–383, doi:10.3762/bjoc.16.35
- ][112]. Phosphines with amine functional groups can easily undergo Mannich condensation reactions. Ferrocene-based Schiff base ligands containing pyridine-n-yl ring (n = 2, 3, 4) (Scheme 27) were synthesized by Hu et al. [113] through the Mannich condensation of ferrocenylphosphine amine 142 and the
Graphical Abstract
Scheme 1: Synthesis of pyridylphosphine ligands.
Figure 1: Pyridylphosphine ligands.
Scheme 2: Synthesis of piperidyl- and oxazinylphosphine ligands.
Scheme 3: Synthesis of linear multi-chelate pyridylphosphine ligands.
Scheme 4: Synthesis of chiral acetal pyridylphosphine ligands.
Scheme 5: Synthesis of diphenylphosphine-substituted triazine ligands.
Scheme 6: Synthesis of (pyridine-2-ylmethyl)phosphine ligands.
Scheme 7: Synthesis of diphosphine pyrrole ligands.
Scheme 8: Synthesis of 4,5-diazafluorenylphosphine ligands.
Scheme 9: Synthesis of thioether-containing pyridyldiphosphine ligands starting from ethylene sulfide and dip...
Scheme 10: Synthesis of monoterpene-derived phosphine pyridine ligands.
Scheme 11: Synthesis of N-phenylphosphine-substituted imidazole ligands.
Scheme 12: Synthesis of triazol-4-ylphosphine ligands.
Scheme 13: Synthesis of phosphanyltriazolopyridines and product selectivity depending on the substituents’ eff...
Scheme 14: Synthesis of PTA-phosphine ligands.
Scheme 15: Synthesis of isomeric phosphine dipyrazole ligands by varying the reaction temperature.
Scheme 16: Synthesis of N-tethered phosphine imidazolium ligands (route A) and diphosphine imidazolium ligands...
Scheme 17: Synthesis of {1-[2-(pyridin-2-yl)- (R = CH) and {1-[2-(pyrazin-2-yl)quinazolin-4-yl]naphthalen-2-yl...
Scheme 18: Synthesis of oxazolylindolylphosphine ligands 102.
Scheme 19: Synthesis of pyrrolylphosphine ligands.
Scheme 20: Synthesis of phosphine guanidinium ligands.
Scheme 21: Synthesis of a polydentate aminophosphine ligand.
Scheme 22: Synthesis of quinolylphosphine ligands.
Scheme 23: Synthesis of N-(triazolylmethyl)phosphanamine ligands.
Figure 2: Triazolylphosphanamine ligands synthesized by Wassenaar’s method [22].
Scheme 24: Synthesis of oxazaphosphorines.
Scheme 25: Synthesis of paracyclophane pyridylphosphine ligands.
Scheme 26: Synthesis of triazolylphosphine ligands.
Figure 3: Click-phosphine ligands.
Scheme 27: Ferrocenyl pyridylphosphine imine ligands.
Scheme 28: Synthesis of phosphinooxazolines (PHOX).
Scheme 29: Synthesis of ferrocenylphosphine oxazoles.
Recent advances on the transition-metal-catalyzed synthesis of imidazopyridines: an updated coverage
- Gagandeep Kour Reen,
- Ashok Kumar and
- Pratibha Sharma
Beilstein J. Org. Chem. 2019, 15, 1612–1704, doi:10.3762/bjoc.15.165
- might be due to the formation of Cu(II)-mediated propargylamine 68 from the alkyne and Schiff base-copper complex that was cyclized and aromatized to form the target compound 67 (Scheme 24). Kumar et al. have described a Cu(OTf)2-catalyzed three-component reaction for the synthesis of imidazo[1,2-a
Graphical Abstract
Figure 1: Various drugs having IP nucleus.
Figure 2: Participation percentage of various TMs for the syntheses of IPs.
Scheme 1: CuI–NaHSO4·SiO2-catalyzed synthesis of imidazo[1,2-a]pyridines.
Scheme 2: Experimental examination of reaction conditions.
Scheme 3: One-pot tandem reaction for the synthesis of 2-haloimidazopyridines.
Scheme 4: Mechanistic scheme for the synthesis of 2-haloimidazopyridine.
Scheme 5: Copper-MOF-catalyzed three-component reaction (3-CR) for imidazo[1,2-a]pyridines.
Scheme 6: Mechanism for copper-MOF-driven synthesis.
Scheme 7: Heterogeneous synthesis via titania-supported CuCl2.
Scheme 8: Mechanism involving oxidative C–H functionalization.
Scheme 9: Heterogeneous synthesis of IPs.
Scheme 10: One-pot regiospecific synthesis of imidazo[1,2-a]pyridines.
Scheme 11: Vinyl azide as an unprecedented substrate for imidazo[1,2-a]pyridines.
Scheme 12: Radical pathway.
Scheme 13: Cu(I)-catalyzed transannulation approach for imidazo[1,5-a]pyridines.
Scheme 14: Plausible radical pathway for the synthesis of imidazo[1,5-a]pyridines.
Scheme 15: A solvent-free domino reaction for imidazo[1,2-a]pyridines.
Scheme 16: Cu-NPs-mediated synthesis of imidazo[1,2-a]pyridines.
Scheme 17: CuI-catalyzed synthesis of isoxazolylimidazo[1,2-a]pyridines.
Scheme 18: Functionalization of 4-bromo derivative via Sonogashira coupling reaction.
Scheme 19: A plausible reaction pathway.
Scheme 20: Cu(I)-catalyzed intramolecular oxidative C–H amidation reaction.
Scheme 21: One-pot synthetic reaction for imidazo[1,2-a]pyridine.
Scheme 22: Plausible reaction mechanism.
Scheme 23: Cu(OAc)2-promoted synthesis of imidazo[1,2-a]pyridines.
Scheme 24: Mechanism for aminomethylation/cycloisomerization of propiolates with imines.
Scheme 25: Three-component synthesis of imidazo[1,2-a]pyridines.
Figure 3: Scope of pyridin-2(1H)-ones and acetophenones.
Scheme 26: CuO NPS-promoted A3 coupling reaction.
Scheme 27: Cu(II)-catalyzed C–N bond formation reaction.
Scheme 28: Mechanism involving Chan–Lam/Ullmann coupling.
Scheme 29: Synthesis of formyl-substituted imidazo[1,2-a]pyridines.
Scheme 30: A tandem sp3 C–H amination reaction.
Scheme 31: Probable mechanistic approach.
Scheme 32: Dual catalytic system for imidazo[1,2-a]pyridines.
Scheme 33: Tentative mechanism.
Scheme 34: CuO/CuAl2O4/ᴅ-glucose-promoted 3-CCR.
Scheme 35: A tandem CuOx/OMS-2-based synthetic strategy.
Figure 4: Biomimetic catalytic oxidation in the presence of electron-transfer mediators (ETMs).
Scheme 36: Control experiment.
Scheme 37: Copper-catalyzed C(sp3)–H aminatin reaction.
Scheme 38: Reaction of secondary amines.
Scheme 39: Probable mechanistic pathway.
Scheme 40: Coupling reaction of α-azidoketones.
Scheme 41: Probable pathway.
Scheme 42: Probable mechanism with free energy calculations.
Scheme 43: MCR for cyanated IP synthesis.
Scheme 44: Substrate scope for the reaction.
Scheme 45: Reaction mechanism.
Scheme 46: Probable mechanistic pathway for Cu/ZnAl2O4-catalyzed reaction.
Scheme 47: Copper-catalyzed double oxidative C–H amination reaction.
Scheme 48: Application towards different coupling reactions.
Scheme 49: Reaction mechanism.
Scheme 50: Condensation–cyclization approach for the synthesis of 1,3-diarylated imidazo[1,5-a]pyridines.
Scheme 51: Optimized reaction conditions.
Scheme 52: One-pot 2-CR.
Scheme 53: One-pot 3-CR without the isolation of chalcone.
Scheme 54: Copper–Pybox-catalyzed cyclization reaction.
Scheme 55: Mechanistic pathway catalyzed by Cu–Pybox complex.
Scheme 56: Cu(II)-promoted C(sp3)-H amination reaction.
Scheme 57: Wider substrate applicability for the reaction.
Scheme 58: Plausible reaction mechanism.
Scheme 59: CuI assisted C–N cross-coupling reaction.
Scheme 60: Probable reaction mechanism involving sp3 C–H amination.
Scheme 61: One-pot MCR-catalyzed by CoFe2O4/CNT-Cu.
Scheme 62: Mechanistic pathway.
Scheme 63: Synthetic scheme for 3-nitroimidazo[1,2-a]pyridines.
Scheme 64: Plausible mechanism for CuBr-catalyzed reaction.
Scheme 65: Regioselective synthesis of halo-substituted imidazo[1,2-a]pyridines.
Scheme 66: Synthesis of 2-phenylimidazo[1,2-a]pyridines.
Scheme 67: Synthesis of diarylated compounds.
Scheme 68: CuBr2-mediated one-pot two-component oxidative coupling reaction.
Scheme 69: Decarboxylative cyclization route to synthesize 1,3-diarylimidazo[1,5-a]pyridines.
Scheme 70: Mechanistic pathway.
Scheme 71: C–H functionalization reaction of enamines to produce diversified heterocycles.
Scheme 72: A plausible mechanism.
Scheme 73: CuI-promoted aerobic oxidative cyclization reaction of ketoxime acetates and pyridines.
Scheme 74: CuI-catalyzed pathway for the formation of imidazo[1,2-a]pyridine.
Scheme 75: Mechanistic pathway.
Scheme 76: Mechanistic rationale for the synthesis of products.
Scheme 77: Copper-catalyzed synthesis of vinyloxy-IP.
Scheme 78: Regioselective product formation with propiolates.
Scheme 79: Proposed mechanism for vinyloxy-IP formation.
Scheme 80: Regioselective synthesis of 3-hetero-substituted imidazo[1,2-a]pyridines with different reaction su...
Scheme 81: Mechanistic pathway.
Scheme 82: CuI-mediated synthesis of 3-formylimidazo[1,2-a]pyridines.
Scheme 83: Radical pathway for 3-formylated IP synthesis.
Scheme 84: Pd-catalyzed urea-cyclization reaction for IPs.
Scheme 85: Pd-catalyzed one-pot-tandem amination and intramolecular amidation reaction.
Figure 5: Scope of aniline nucleophiles.
Scheme 86: Pd–Cu-catalyzed Sonogashira coupling reaction.
Scheme 87: One-pot amide coupling reaction for the synthesis of imidazo[4,5-b]pyridines.
Scheme 88: Urea cyclization reaction for the synthesis of two series of pyridines.
Scheme 89: Amidation reaction for the synthesis of imidazo[4,5-b]pyridines.
Figure 6: Amide scope.
Scheme 90: Pd NPs-catalyzed 3-component reaction for the synthesis of 2,3-diarylated IPs.
Scheme 91: Plausible mechanistic pathway for Pd NPs-catalyzed MCR.
Scheme 92: Synthesis of chromenoannulated imidazo[1,2-a]pyridines.
Scheme 93: Mechanism for the synthesis of chromeno-annulated IPs.
Scheme 94: Zinc oxide NRs-catalyzed synthesis of imidazo[1,2-a]azines/diazines.
Scheme 95: Zinc oxide-catalyzed isocyanide based GBB reaction.
Scheme 96: Reaction pathway for ZnO-catalyzed GBB reaction.
Scheme 97: Mechanistic pathway.
Scheme 98: ZnO NRs-catalyzed MCR for the synthesis of imidazo[1,2-a]azines.
Scheme 99: Ugi type GBB three-component reaction.
Scheme 100: Magnetic NPs-catalyzed synthesis of imidazo[1,2-a]pyridines.
Scheme 101: Regioselective synthesis of 2-alkoxyimidazo[1,2-a]pyridines catalyzed by Fe-SBA-15.
Scheme 102: Plausible mechanistic pathway for the synthesis of 2-alkoxyimidazopyridine.
Scheme 103: Iron-catalyzed synthetic approach.
Scheme 104: Iron-catalyzed aminooxygenation reaction.
Scheme 105: Mechanistic pathway.
Scheme 106: Rh(III)-catalyzed double C–H activation of 2-substituted imidazoles and alkynes.
Scheme 107: Plausible reaction mechanism.
Scheme 108: Rh(III)-catalyzed non-aromatic C(sp2)–H bond activation–functionalization for the synthesis of imid...
Scheme 109: Reactivity and selectivity of different substrates.
Scheme 110: Rh-catalyzed direct C–H alkynylation by Li et al.
Scheme 111: Suggested radical mechanism.
Scheme 112: Scandium(III)triflate-catalyzed one-pot reaction and its mechanism for the synthesis of benzimidazo...
Scheme 113: RuCl3-assisted Ugi-type Groebke–Blackburn condensation reaction.
Scheme 114: C-3 aroylation via Ru-catalyzed two-component reaction.
Scheme 115: Regioselective synthetic mechanism.
Scheme 116: La(III)-catalyzed one-pot GBB reaction.
Scheme 117: Mechanistic approach for the synthesis of imidazo[1,2-a]pyridines.
Scheme 118: Synthesis of imidazo[1,2-a]pyridine using LaMnO3 NPs under neat conditions.
Scheme 119: Mechanistic approach.
Scheme 120: One-pot 3-CR for regioselective synthesis of 2-alkoxy-3-arylimidazo[1,2-a]pyridines.
Scheme 121: Formation of two possible products under optimization of the catalysts.
Scheme 122: Mechanistic strategy for NiFe2O4-catalyzed reaction.
Scheme 123: Two-component reaction for synthesizing imidazodipyridiniums.
Scheme 124: Mechanistic scheme for the synthesis of imidazodipyridiniums.
Scheme 125: CuI-catalyzed arylation of imidazo[1,2-a]pyridines.
Scheme 126: Mechanism for arylation reaction.
Scheme 127: Cupric acetate-catalyzed double carbonylation approach.
Scheme 128: Radical mechanism for double carbonylation of IP.
Scheme 129: C–S bond formation reaction catalyzed by cupric acetate.
Scheme 130: Cupric acetate-catalyzed C-3 formylation approach.
Scheme 131: Control experiments for signifying the role of DMSO and oxygen.
Scheme 132: Mechanism pathway.
Scheme 133: Copper bromide-catalyzed CDC reaction.
Scheme 134: Extension of the substrate scope.
Scheme 135: Plausible radical pathway.
Scheme 136: Transannulation reaction for the synthesis of imidazo[1,5-a]pyridines.
Scheme 137: Plausible reaction pathway for denitrogenative transannulation.
Scheme 138: Cupric acetate-catalyzed C-3 carbonylation reaction.
Scheme 139: Plausible mechanism for regioselective C-3 carbonylation.
Scheme 140: Alkynylation reaction at C-2 of 3H-imidazo[4,5-b]pyridines.
Scheme 141: Two-way mechanism for C-2 alkynylation of 3H-imidazo[4,5-b]pyridines.
Scheme 142: Palladium-catalyzed SCCR approach.
Scheme 143: Palladium-catalyzed Suzuki coupling reaction.
Scheme 144: Reaction mechanism.
Scheme 145: A phosphine free palladium-catalyzed synthesis of C-3 arylated imidazopyridines.
Scheme 146: Palladium-mediated Buchwald–Hartwig cross-coupling reaction.
Figure 7: Structure of the ligands optimized.
Scheme 147: Palladium acetate-catalyzed direct arylation of imidazo[1,2-a]pyridines.
Scheme 148: Palladium acetate-catalyzed mechanistic pathway.
Scheme 149: Palladium acetate-catalyzed regioselective arylation reported by Liu and Zhan.
Scheme 150: Mechanism for selective C-3 arylation of IP.
Scheme 151: Pd(II)-catalyzed alkenylation reaction with styrenes.
Scheme 152: Pd(II)-catalyzed alkenylation reaction with acrylates.
Scheme 153: A two way mechanism.
Scheme 154: Double C–H activation reaction catalyzed by Pd(OAc)2.
Scheme 155: Probable mechanism.
Scheme 156: Palladium-catalyzed decarboxylative coupling.
Scheme 157: Mechanistic cycle for decarboxylative arylation reaction.
Scheme 158: Ligand-free approach for arylation of imidazo[1,2-a]pyridine-3-carboxylic acids.
Scheme 159: Mechanism for ligandless arylation reaction.
Scheme 160: NHC-Pd(II) complex assisted arylation reaction.
Scheme 161: C-3 arylation of imidazo[1,2-a]pyridines with aryl bromides catalyzed by Pd(OAc)2.
Scheme 162: Pd(II)-catalyzed C-3 arylations with aryl tosylates and mesylates.
Scheme 163: CDC reaction for the synthesis of imidazo[1,2-a]pyridines.
Scheme 164: Plausible reaction mechanism for Pd(OAc)2-catalyzed synthesis of imidazo[1,2-a]pyridines.
Scheme 165: Pd-catalyzed C–H amination reaction.
Scheme 166: Mechanism for C–H amination reaction.
Scheme 167: One-pot synthesis for 3,6-di- or 2,3,6-tri(hetero)arylimidazo[1,2-a]pyridines.
Scheme 168: C–H/C–H cross-coupling reaction of IPs and azoles catalyzed by Pd(II).
Scheme 169: Mechanistic cycle.
Scheme 170: Rh-catalyzed C–H arylation reaction.
Scheme 171: Mechanistic pathway for C–H arylation of imidazo[1,2-a]pyridine.
Scheme 172: Rh(III)-catalyzed double C–H activation of 2-phenylimidazo[1,2-a]pyridines and alkynes.
Scheme 173: Rh(III)-catalyzed mechanistic pathway.
Scheme 174: Rh(III)-mediated oxidative coupling reaction.
Scheme 175: Reactions showing functionalization of the product obtained by the group of Kotla.
Scheme 176: Mechanism for Rh(III)-catalyzed oxidative coupling reaction.
Scheme 177: Rh(III)-catalyzed C–H activation reaction.
Scheme 178: Mechanistic cycle.
Scheme 179: Annulation reactions of 2-arylimidazo[1,2-a]pyridines and alkynes.
Scheme 180: Two-way reaction mechanism for annulations reaction.
Scheme 181: [RuCl2(p-cymene)]2-catalyzed C–C bond formation reaction.
Scheme 182: Reported reaction mechanism.
Scheme 183: Fe(III) catalyzed C-3 formylation approach.
Scheme 184: SET mechanism-catalyzed by Fe(III).
Scheme 185: Ni(dpp)Cl2-catalyzed KTC coupling.
Scheme 186: Pd-catalyzed SM coupling.
Scheme 187: Vanadium-catalyzed coupling of IP and NMO.
Scheme 188: Mechanistic cycle.
Scheme 189: Selective C3/C5–H bond functionalizations by mono and bimetallic systems.
Scheme 190: rGO-Ni@Pd-catalyzed C–H bond arylation of imidazo[1,2-a]pyridine.
Scheme 191: Mechanistic pathway for heterogeneously catalyzed arylation reaction.
Scheme 192: Zinc triflate-catalyzed coupling reaction of substituted propargyl alcohols.
Mechanochemical synthesis of hyper-crosslinked polymers: influences on their pore structure and adsorption behaviour for organic vapors
- Sven Grätz,
- Sebastian Zink,
- Hanna Kraffczyk,
- Marcus Rose and
- Lars Borchardt
Beilstein J. Org. Chem. 2019, 15, 1154–1161, doi:10.3762/bjoc.15.112
- -Crafts alkylations [5], cross-coupling reactions [6] and cyclotrimerizations [7], to amine-based chemistry with Schiff base reactions [8], imidisation, and amidisation reactions [9]. In the recent past, a strong focus was also set on the development of HCPs (hyper-crosslinked polymers) [10]. Typically
Graphical Abstract
Figure 1: A: Mechanochemical polymerization of BCMBP (4,4’-bis(chloromethyl)-1,1’-biphenyl) towards the porou...
Figure 2: A: IR spectra of the monomer BCMBP and NG-HCP showing a decrease of the C–Cl vibration after the re...
Figure 3: A: Evolution of pressure in the course of the reaction measured by the GTM system. The addition of ...
Figure 4: The correlation between the liquids’ boiling point and the SSA of the polymer. In general, a lower ...
Figure 5: Physisorption isotherms of benzene vapour at different temperatures on HCP synthesised classically ...
Figure 6: Physisorption isotherms of cyclohexane on mechanochemically synthesised HCP at temperatures 288, 29...
Synthesis of a novel category of pseudo-peptides using an Ugi three-component reaction of levulinic acid as bifunctional substrate, amines, and amino acid-based isocyanides
- Maryam Khalesi,
- Azim Ziyaei Halimehjani and
- Jürgen Martens
Beilstein J. Org. Chem. 2019, 15, 852–857, doi:10.3762/bjoc.15.82
- component that leads to the formation of an imine intermediate A. The formed Schiff base is in equilibrium with its iminium cation B as a result of an intramolecular proton exchange with the carboxylic acid moiety which activates the iminium ion for the nucleophilic addition of isocyanide. Consequently, the
Graphical Abstract
Scheme 1: Synthesis of amino acid-based isocyanides starting from α-amino acids.
Scheme 2: Synthesis of pseudo-peptides using levulinic acid, isocyanide esters and amines.
Figure 1: Synthesis of functionalized 5-membered lactams using Ugi reaction. aIsolated yield for mixture of d...
Scheme 3: Proposed mechanism for Ugi-4C-3CR.
Figure 2: ORTEP representation of compound (R*,S*)-4a with thermal ellipsoids at 50% probability. Opposite en...
Design, synthesis and spectroscopic properties of crown ether-capped dibenzotetraaza[14]annulenes
- Krzysztof M. Zwoliński and
- Julita Eilmes
Beilstein J. Org. Chem. 2019, 15, 617–622, doi:10.3762/bjoc.15.57
- -ATR, 1H and 13C NMR spectroscopy and elemental analysis. Keywords: crown ether; dibenzotetraaza[14]annulene; DBTAA; macrocycle; Schiff base; Introduction The design and synthesis of novel polycyclic receptor architecture is of fundamental importance, since model recognition studies contribute to
- ], respectively. The family of dibenzotetraaza[14]annulenes (abbreviated hereafter as DBTAAs) belong to a class of quadridentate Schiff base macrocycles that display exceptional stability toward light, oxygen and water [14]. Thanks to basic similarities in their structure and physicochemical properties, DBTAAs
Graphical Abstract
Figure 1: Timeline for the structure evolution of crown-capped DBTAAs (created on the basis of references [24-28]).
Scheme 1: Synthesis of the crown-capped DBTAA receptors 3a and 3b. Reagents and conditions: i) Et3N, CH3CN, r...
Figure 2: 1H NMR spectra (298 K, CDCl3) of: a) crown ether-capped receptor 3b and b) it’s corresponding paren...
Revisiting ring-degenerate rearrangements of 1-substituted-4-imino-1,2,3-triazoles
- James T. Fletcher,
- Matthew D. Hanson,
- Joseph A. Christensen and
- Eric M. Villa
Beilstein J. Org. Chem. 2018, 14, 2098–2105, doi:10.3762/bjoc.14.184
- cations, and have impacted fields that include bioimaging [26][27] and chemosensing [28][29]. Surprisingly, the reported examples partnering 1,2,3-triazole and imine N-donor groups are limited [30][31][32], despite the ubiquity of such Schiff base subunits in coordination chemistry. 4-Iminotriazole
Graphical Abstract
Figure 1: Conversion of 1-substituted-4-formyltriazole analogs via ring-degenerate rearrangement of 1-substit...
Figure 2: ORTEP structure of 2cc’. Thermal ellipsoids shown at 25% probability.
Figure 3: 1H NMR aromatic region of a product mixture compared with reference imine analogs. Singlets appeari...
Figure 4: Rearrangement reaction progress of 1a leading to irreversible formation of a colorimetric self-indi...
A switchable [2]rotaxane with two active alkenyl groups
- Xiu-Li Zheng,
- Rong-Rong Tao,
- Rui-Rui Gu,
- Wen-Zhi Wang and
- Da-Hui Qu
Beilstein J. Org. Chem. 2018, 14, 2074–2081, doi:10.3762/bjoc.14.181
- [36] were synthesized according to the previous literature. The key intermediate compound 5, containing a prior DBA recognition station and possessing alkynyl and ethylenic groups at two terminals respectively, was prepared from aldehyde 1 and amine 2. A “Schiff base” reaction was introduced at first
Graphical Abstract
Scheme 1: Chemical structures and acid-base stimuli responsiveness of target [2]rotaxane R1 and deprotonated ...
Scheme 2: Syntheses of key intermediates 5, 8 and target [2]rotaxane R1.
Figure 1: Partial 1H NMR spectra (400 MHz, CDCl3, 298 K). (a) Compound 5, (b) target [2]rotaxane R1, (c) azid...
Figure 2: Partial 1H NMR spectra (400 MHz, CDCl3, 298 K). (a) [2]Rotaxane R1, (b) deprotonation by the additi...
Figure 3: Partial 2D ROESY NMR spectra (500 MHz, CDCl3, 298 K). (a) [2]Rotaxane R1, (b) deprotonation with ad...
Coordination-driven self-assembly vs dynamic covalent chemistry: versatile methods for the synthesis of molecular metallarectangles
- Li-Li Ma,
- Jia-Qin Han,
- Wei-Guo Jia and
- Ying-Feng Han
Beilstein J. Org. Chem. 2018, 14, 2027–2034, doi:10.3762/bjoc.14.178
- group. The geometries of the metallarectangles 3a and 3b were expected to be similar, as they comprise two oxalate-bridged half-sandwich rhodium fragments linked by two Schiff-base ligands L1 or L2, giving the desired tetranuclear metallarectangles. In order to test the possibility of using dynamic
Graphical Abstract
Scheme 1: Synthesis of half-sandwich rhodium metallarectangles via three different methods. Method A: coordin...
Figure 1: Partial 1H NMR spectra (400 MHz, DMSO-d6, ppm) of (a) L1; (b) the sample of metallarectagle 3a obta...
Figure 2: Partial 1H NMR spectra (400 MHz, DMSO-d6, ppm) of (a) L2; (b) a sample of metallarectangle 3b obtai...
Figure 3: Calculated (bottom) and experimental (top) ESI-MS spectra of the tetracationic half-sandwich rhodiu...
Figure 4: Optimized structures of the charged metallarectangles 3a (top) and 3b (bottom), optimized with the ...
Synthesis of diamido-bridged bis-pillar[5]arenes and tris-pillar[5]arenes for construction of unique [1]rotaxanes and bis-[1]rotaxanes
- Ying Han,
- Li-Ming Xu,
- Cui-Yun Nie,
- Shuo Jiang,
- Jing Sun and
- Chao-Guo Yan
Beilstein J. Org. Chem. 2018, 14, 1660–1667, doi:10.3762/bjoc.14.142
- ][55][56][57]. Recently, we have successfully constructed a couple of pseudo[1]rotaxane and [1]rotaxane both in solution and in solid state developed by using mono-functionalized pillar[5]arene Schiff base, urea and pyridylimine derivatives [58][59][60][61][62][63]. In continuation of our effort on the
Graphical Abstract
Scheme 1: Synthesis of pillar[5]arene mono(oxyalkoxy)benzoic acids 3a–c.
Figure 1: single crystal structure of pillar[5]arene 2a.
Figure 2: Single crystal structure of pillar[5]arene 2f.
Scheme 2: Synthesis of diamido-bridged bis-pillar[5]arenes 5a–d.
Figure 3: The 2D NOSEY spectrum of bis-pillar[5]arene 5d.
Scheme 3: Synthesis of pillar[5]arene di(oxyalkoxy)benzoic acid 8.
Figure 4: Single crystal structure of pillar[5]arene 7.
Scheme 4: Synthesis of diamido-bridged tris-pillar[5]arenes 9a–d.
Figure 5: The 2D NOSEY spectra of tris-pillar[5]arene 9d.
Recent applications of chiral calixarenes in asymmetric catalysis
- Mustafa Durmaz,
- Erkan Halay and
- Selahattin Bozkurt
Beilstein J. Org. Chem. 2018, 14, 1389–1412, doi:10.3762/bjoc.14.117
- asymmetric alkylation of tert-butyl glycinate benzophenone Schiff base 3 with alkyl halides 4 in a toluene–50% KOH biphasic system (Scheme 1). The corresponding α-alkyl-α-amino acid derivatives 5 were obtained in excellent yields with very low enantioselectivities (up to 9%). This is the first example of
Graphical Abstract
Figure 1: Inherently chiral calix[4]arene-based phase-transfer catalysts.
Scheme 1: Asymmetric alkylations of 3 catalyzed by (±)-1 and (±)-2 under phase-transfer conditions.
Scheme 2: Synthesis of chiral calix[4]arene-based phase-transfer catalyst 7 and structure of O’Donnell’s N-be...
Scheme 3: Asymmetric alkylation of glycine derivative 3 catalyzed by calixarene-based phase-transfer catalyst ...
Figure 2: Calix[4]arene-amides used as phase-transfer catalysts.
Scheme 4: Phase-transfer alkylation of 3 catalyzed by calixarene-triamide 12.
Scheme 5: Synthesis of inherently chiral calix[4]arenes 20a/20b substituted at the lower rim. Reaction condit...
Scheme 6: Asymmetric Henry reaction between 21 and 22 catalyzed by 20a/20b.
Figure 3: Proposed transition state model of asymmetric Henry reaction.
Scheme 7: Synthesis of enantiomerically pure phosphinoferrocenyl-substituted calixarene ligands 27–29.
Scheme 8: Asymmetric coupling reaction of aryl boronates and aryl halides in the presence of calixarene mono ...
Scheme 9: Asymmetric allylic alkylation in the presence of calix[4]arene ligand (S,S)-29.
Figure 4: Structure of inherently chiral oxazoline calix[4]arenes applied in the palladium-catalyzed Tsuji–Tr...
Scheme 10: Asymmetric Tsuji–Trost reaction in the presence of calix[4]arene ligands 36–39.
Figure 5: BINOL-derived calix[4]arene-diphosphite ligands.
Scheme 11: Asymmetric hydrogenation of 41a and 41b catalyzed by in situ-generated catalysts comprised of [Rh(C...
Figure 6: Inherently chiral calix[4]arene 43 containing a diarylmethanol structure.
Scheme 12: Asymmetric Michael addition reaction of 44 with 45 catalyzed by 43.
Figure 7: Calix[4]arene-based chiral primary amine–thiourea catalysts.
Scheme 13: Asymmetric Michael addition of 48 with 49 catalyzed by 47a and 47b.
Scheme 14: Enantioselective Michael addition of 51 to 52 catalyzed by calix[4]arene thioureas.
Scheme 15: Synthesis of calix[4]arene-based tertiary amine–thioureas 54–56.
Scheme 16: Asymmetric Michael addition of 34 and 57 to nitroalkenes 49 catalyzed by 54b.
Scheme 17: Synthesis of p-tert-butylcalix[4]arene bis-squaramide derivative 64.
Scheme 18: Asymmetric Michael addition catalyzed by 64.
Scheme 19: Synthesis of chiral p-tert-butylphenol analogue 68.
Figure 8: Novel prolinamide organocatalysts based on the calix[4]arene scaffold.
Scheme 20: Asymmetric aldol reactions of 72 with 70 and 71 catalyzed by 69b.
Scheme 21: Synthesis of p-tert-butylcalix[4]arene-based chiral organocatalysts 75 and 78 derived from L-prolin...
Scheme 22: Synthesis of upper rim-functionalized calix[4]arene-based L-proline derivative 83.
Scheme 23: Synthesis and proposed structure of Calix-Pro-MN (86).
Figure 9: Calix[4]arene-based L-proline catalysts containing ester, amide and acid units.
Scheme 24: Synthesis of calix[4]arene-based prolinamide 92.
Scheme 25: Calixarene-based catalysts for the aldol reaction of 21 with 70.
Scheme 26: Asymmetric aldol reactions of 72 with cyclic ketones catalyzed by calix[4]arene-based chiral organo...
Figure 10: A proposed structure for catalyst 92 in H2O.
Scheme 27: Synthetic route for organocatalyst 98.
Scheme 28: Asymmetric aldol reactions catalyzed by 99.
Figure 11: Proposed catalytic environment for catalyst 99 in the presence of water.
Scheme 29: Asymmetric aldol reactions between 94 and 72 catalyzed by 55a.
Scheme 30: Enantioselective Biginelli reactions catalyzed by 69f.
Scheme 31: Synthesis of calix[4]arene–(salen) complexes.
Scheme 32: Enantioselective epoxidation of 108 catalyzed by 107a/107b.
Scheme 33: Synthesis of inherently chiral calix[4]arene catalysts 111 and 112.
Scheme 34: Enantioselective MPV reduction.
Scheme 35: Synthesis of chiral calix[4]arene ligands 116a–c.
Scheme 36: Asymmetric MPV reduction with chiral calix[4]arene ligands.
Scheme 37: Chiral AlIII–calixarene complexes bearing distally positioned chiral substituents.
Scheme 38: Asymmetric MPV reduction in the presence of chiral calix[4]arene diphosphites.
Scheme 39: Synthesis of enantiomerically pure inherently chiral calix[4]arene phosphonic acid.
Scheme 40: Asymmetric aza-Diels–Alder reactions catalyzed by (cR,pR)-121.
Scheme 41: Asymmetric ring opening of epoxides catalyzed by (cR,pR)-121.
Mannich base-connected syntheses mediated by ortho-quinone methides
- Petra Barta,
- Ferenc Fülöp and
- István Szatmári
Beilstein J. Org. Chem. 2018, 14, 560–575, doi:10.3762/bjoc.14.43
- and the aldehyde yields a Schiff base and then the latter reacts with 2-naphthol in the second nucleophilic addition step. The other theory assumes the formation of an ortho-quinone methide (o-QM) intermediate by the reaction of 2-naphthol and benzaldehyde. Re-aromatization, the driving force of the
Graphical Abstract
Scheme 1: Formation of amidoalkylnaphthols 4 via o-QM intermediate 3.
Scheme 2: Asymmetric syntheses of triarylmethanes starting from diarylmethylamines.
Scheme 3: Proposed mechanism for the formation of 2,2-dialkyl-3-dialkylamino-2,3-dihydro-1H-naphtho[2,1-b]pyr...
Scheme 4: Cycloadditions of isoflavonoid-derived o-QMs and various dienophiles.
Scheme 5: [4 + 2] Cycloaddition reactions between aminonaphthols and cyclic amines.
Scheme 6: Brønsted acid-catalysed reaction between aza-o-QMs and 2- or 3-substituted indoles.
Scheme 7: Formation of 3-(α,α-diarylmethyl)indoles 52 in different synthetic pathways.
Scheme 8: Alkylation of o-QMs with N-, O- or S-nucleophiles.
Scheme 9: Formation of DNA linkers and o-QM mediated polymers.
5-Aminopyrazole as precursor in design and synthesis of fused pyrazoloazines
- Ranjana Aggarwal and
- Suresh Kumar
Beilstein J. Org. Chem. 2018, 14, 203–242, doi:10.3762/bjoc.14.15
- provided pyrazolooxazinones 191 which converted to 5-aminopyrazolo[3,4-d]pyrimidine 192 by reaction with hydrazine hydrate in n-butanol. Further treatment of 192 with aromatic aldehydes provided the corresponding Schiff base 193. Singla et al. [131] reported the synthesis of pyrazolo[3,4-d]pyrimidinyl-4
Graphical Abstract
Figure 1: Selected examples of drugs with fused pyrazole rings.
Figure 2: Typical structures of some fused pyrazoloazines from 5-aminopyrazoles.
Scheme 1: Regiospecific synthesis of 4 and 6-trifluoromethyl-1H-pyrazolo[3,4-b]pyridines.
Scheme 2: Synthesis of pyrazolo[3,4-b]pyridine-6-carboxylates.
Scheme 3: Synthesis of 1,4,6-triaryl-1H-pyrazolo[3,4-b]pyridines with ionic liquid .
Scheme 4: Synthesis of coumarin-based isomeric tetracyclic pyrazolo[3,4-b]pyridines.
Scheme 5: Synthesis of 6-substituted pyrazolo[3,4-b]pyridines under Heck conditions.
Scheme 6: Microwave-assisted palladium-catalyzed synthesis of pyrazolo[3,4-b]pyridines.
Scheme 7: Acid-catalyzed synthesis of pyrazolo[3,4-b]pyridines via enaminones.
Scheme 8: Synthesis of pyrazolo[3,4-b]pyridines via aza-Diels–Alder reaction.
Scheme 9: Synthesis of macrocyclane fused pyrazolo[3,4-b]pyridine derivatives.
Scheme 10: Three-component synthesis of 4,7-dihydro-1H-pyrazolo[3,4-b]pyridine derivatives.
Scheme 11: Ultrasonicated synthesis of spiro[indoline-3,4'-pyrazolo[3,4-b]pyridine]-2,6'(1'H)-diones.
Scheme 12: Synthesis of spiro[indoline-3,4'-pyrazolo[3,4-b]pyridine] derivatives under conventional heating co...
Scheme 13: Nanoparticle-catalyzed synthesis of pyrazolo[3,4-b]pyridine-spiroindolinones.
Scheme 14: Microwave-assisted multicomponent synthesis of spiropyrazolo[3,4-b]pyridines.
Scheme 15: Unexpected synthesis of naphthoic acid-substituted pyrazolo[3,4-b]pyridines.
Scheme 16: Multicomponent synthesis of variously substituted pyrazolo[3,4-b]pyridine derivatives.
Scheme 17: Three-component synthesis of 4,7-dihydropyrazolo[3,4-b]pyridines and pyrazolo[3,4-b]pyridines.
Scheme 18: Synthesis of pyrazolo[3,4-b]pyridine-5-spirocycloalkanediones.
Scheme 19: Ultrasound-mediated three-component synthesis of pyrazolo[3,4-b]pyridines.
Scheme 20: Multicomponent synthesis of 4-aryl-3-methyl-1-phenyl-4,6,8,9-tetrahydropyrazolo [3,4-b]thiopyrano[4...
Scheme 21: Synthesis of 2,3-dihydrochromeno[4,3-d]pyrazolo[3,4-b]pyridine-1,6-diones.
Scheme 22: FeCl3-catalyzed synthesis of o-hydroxyphenylpyrazolo[3,4-b]pyridine derivatives.
Scheme 23: Ionic liquid-mediated synthesis of pyrazolo[3,4-b]pyridines.
Scheme 24: Microwave-assisted synthesis of pyrazolo[3,4-b]pyridines.
Scheme 25: Multicomponent synthesis of pyrazolo[3,4-b]pyridine-5-carbonitriles.
Scheme 26: Unusual domino synthesis of 4,7-dihydropyrazolo[3,4-b]pyridine-5-nitriles.
Scheme 27: Synthesis of 4,5,6,7-tetrahydro-4H-pyrazolo[3,4-b]pyridines under conventional heating and ultrasou...
Scheme 28: L-Proline-catalyzed synthesis of of pyrazolo[3,4-b]pyridine.
Scheme 29: Microwave-assisted synthesis of 5-aminoarylpyrazolo[3,4-b]pyridines.
Scheme 30: Microwave-assisted multi-component synthesis of pyrazolo[3,4-e]indolizines.
Scheme 31: Synthesis of fluoropropynyl and fluoroalkyl substituted pyrazolo[1,5-a]pyrimidine.
Scheme 32: Acid-catalyzed synthesis of pyrazolo[1,5-a]pyrimidine derivatives.
Scheme 33: Chemoselective and regiospecific synthesis of 2-(3-methylpyrazol-1’-yl)-5-methylpyrazolo[1,5-a]pyri...
Scheme 34: Regioselective synthesis of 7-trifluoromethylpyrazolo[1,5-a]pyrimidines.
Scheme 35: Microwave-assisted synthesis of 7-trifluoromethylpyrazolo[1,5-a]pyrimidine carboxylates.
Scheme 36: Microwave and ultrasound-assisted synthesis of 7-trifluoromethylpyrazolo[1,5-a]pyrimidines.
Scheme 37: Base-catalyzed unprecedented synthesis of pyrazolo[1,5-a]pyrimidines via C–C bond cleavage.
Scheme 38: Synthesis of aminobenzothiazole/piperazine linked pyrazolo[1,5-a]pyrimidines.
Scheme 39: Synthesis of aminoalkylpyrazolo[1,5-a]pyrimidine-7-amines.
Scheme 40: Synthesis of pyrazolo[1,5-a]pyrimidines from condensation of 5-aminopyrazole 126 and ethyl acetoace...
Scheme 41: Synthesis of 7-aminopyrazolo[1,5-a]pyrimidines.
Scheme 42: Unexpected synthesis of 7-aminopyrazolo[1,5-a]pyrimidines under solvent free and solvent-mediated c...
Scheme 43: Synthesis of N-(4-aminophenyl)-7-aryloxypyrazolo[1,5-a]pyrimidin-5-amines.
Scheme 44: Base-catalyzed synthesis of 5,7-diarylpyrazolo[1,5-a]pyrimidines.
Scheme 45: Synthesis of 6,7-dihydropyrazolo[1,5-a]pyrimidines in PEG-400.
Scheme 46: Synthesis of 7-heteroarylpyrazolo[1,5-a]pyrimidine-3-carboxamides.
Scheme 47: Synthesis of 7-heteroarylpyrazolo[1,5-a]pyrimidine derivatives under conventional heating and micro...
Scheme 48: Synthesis of N-aroylpyrazolo[1,5-a]pyrimidine-5-amines.
Scheme 49: Regioselective synthesis of ethyl pyrazolo[1,5-a]pyrimidine-7-carboxylate.
Scheme 50: Sodium methoxide-catalyzed synthesis of 3-cyano-6,7-diarylpyrazolo[1,5-a]pyrimidines.
Scheme 51: Synthesis of various pyrazolo[3,4-d]pyrimidine derivatives.
Scheme 52: Synthesis of hydrazinopyrazolo[3,4-d]pyrimidine derivatives.
Scheme 53: Synthesis of N-arylidinepyrazolo[3,4-d]pyrimidin-5-amines.
Scheme 54: Synthesis of pyrazolo[3,4-d]pyrimidinyl-4-amines.
Scheme 55: Iodine-catalyzed synthesis of pyrazolo[3,4-d]pyrimidinones.
Scheme 56: Synthesis of ethyl 6-amino-2H-pyrazolo[3,4-d]pyrimidine-4-carboxylate.
Scheme 57: Synthesis of 4-substituted-(3,6-dihydropyran-4-yl)-1H-pyrazolo[3,4-d]pyrimidines.
Scheme 58: Synthesis of 1-(2,4-dichlorophenyl)pyrazolo[3,4-d]pyrimidin-4-yl carboxamides.
Scheme 59: Synthesis of 5-(1,3,4-thidiazol-2-yl)pyrazolo[3,4-d]pyrimidine.
Scheme 60: One pot POCl3-catalyzed synthesis of 1-arylpyrazolo[3,4-d]pyrimidin-4-ones.
Scheme 61: Synthesis of 4-amino-N1,C3-dialkylpyrazolo[3,4-d]pyrimidines under Suzuki conditions.
Scheme 62: Microwave-assisted synthesis of pyrazolo[3,4-b]pyrazines.
Scheme 63: Synthesis and derivatization of pyrazolo[3,4-b]pyrazine-5-carbonitriles.
Scheme 64: Synthesis of 2-thioxo-pyrazolo[1,5-a][1,3,5]triazin-4-ones.
Scheme 65: Synthesis of 2,3-dihydropyrazolo[1,5-a][1,3,5]triazin-4(1H)-one.
Scheme 66: Synthesis of pyrazolo[1,5-a][1,3,5]triazine-8-carboxylic acid ethyl ester.
Scheme 67: Microwave-assisted synthesis of 4,7-dihetarylpyrazolo[1,5-a][1,3,5]triazines.
Scheme 68: Alternative synthetic route to 4,7-diheteroarylpyrazolo[1,5-a][1,3,5]triazines.
Scheme 69: Synthesis of 4-aryl-2-ethylthio-7-methylpyrazolo[1,5-a][1,3,5]triazines.
Scheme 70: Microwave-assisted synthesis of 4-aminopyrazolo[1,5-a][1,3,5]triazine.
Scheme 71: Synthesis of pyrazolo[3,4-d][1,2,3]triazines from pyrazol-5-yl diazonium salts.
Scheme 72: Synthesis of 2,5-dihydropyrazolo[3,4-e][1,2,4]triazines.
Scheme 73: Synthesis of pyrazolo[5,1-c][1,2,4]triazines via diazopyrazolylenaminones.
Scheme 74: Synthesis of pyrazolo[5,1-c][1,2,4]triazines in presence of sodium acetate.
Scheme 75: Synthesis of various 7-diazopyrazolo[5,1-c][1,2,4]triazine derivatives.
Scheme 76: One pot synthesis of pyrazolo[5,1-c][1,2,4]triazines.
Scheme 77: Synthesis of 4-amino-3,7,8-trinitropyrazolo-[5,1-c][1,2,4]triazines.
Scheme 78: Synthesis of tricyclic pyrazolo[5,1-c][1,2,4]triazines by azocoupling reaction.
The use of 4,4,4-trifluorothreonine to stabilize extended peptide structures and mimic β-strands
- Yaochun Xu,
- Isabelle Correia,
- Tap Ha-Duong,
- Nadjib Kihal,
- Jean-Louis Soulier,
- Julia Kaffy,
- Benoît Crousse,
- Olivier Lequin and
- Sandrine Ongeri
Beilstein J. Org. Chem. 2017, 13, 2842–2853, doi:10.3762/bjoc.13.276
- followed a general procedure to access to (2S,3S)-CF3-threonine through an aldol reaction of CF3CHO with the Ni(II) complex of the chiral Schiff base of glycine which was introduced by Belokon et al. [23][24]. The chiral auxiliary (S)-N-(2-benzoylphenyl)-1-benzylpyrrolidine-2-carboxamide (11) was obtained
- conditions gave the nickel Schiff base complex 12 in 71% yield as red crystals. The nucleophilic glycine equivalent 12 went through the aldol reaction with trifluoroacetaldehyde to give complex 13 in moderate yield (66%). Further hydrolysis of complex 13 led to the recovery of the chiral auxiliary 11 and
- obtained through the aldol reaction of trifluoroacetaldehyde with the Ni(II) complex of the chiral Schiff base of glycine. The conformational analysis of these pentapeptides was conducted by the combined use of NMR spectroscopy and molecular dynamics simulations. NMR conformational studies showed that the
Graphical Abstract
Figure 1: A) Natural threonine and its trifluoromethyl analogues sawhorse projections. B) Structure of Boc-pr...
Scheme 1: Synthesis of (2S,3R)-Boc-CF3-Thr(Bzl) 9.
Scheme 2: Synthesis of (2S,3S)-Boc-CF3-Thr 14.
Scheme 3: Synthesis of pentapeptides 1a–4a and 1b–4b.
Figure 2: Probability distribution of the peptide conformations as a function of end-to-end distance (defined...
Figure 3: Probability distribution of the peptide dihedral angles ψ for the three central residues Val2 (blac...
Figure 4: Effects of compounds 1–4 on Aβ1-42 fibrillization assessed by ThT-fluorescence spectroscopy at 10:1...
Solvent-free copper-catalyzed click chemistry for the synthesis of N-heterocyclic hybrids based on quinoline and 1,2,3-triazole
- Martina Tireli,
- Silvija Maračić,
- Stipe Lukin,
- Marina Juribašić Kulcsár,
- Dijana Žilić,
- Mario Cetina,
- Ivan Halasz,
- Silvana Raić-Malić and
- Krunoslav Užarević
Beilstein J. Org. Chem. 2017, 13, 2352–2363, doi:10.3762/bjoc.13.232
- -aminobiphenyl (1) with ethyl 4,4,4-trifluoro-3-oxobutanoate in polyphosphoric acid (PPA) followed by the cyclization of the Schiff base intermediate afforded the 2-(trifluoromethyl)-6-phenylquinolone 3 (Scheme 1). O-Alkynylquinoline derivative 4 required for the click synthesis of target triazoles was obtained
Graphical Abstract
Scheme 1: Synthetic procedures for preparation of p-halogen-substituted and non-substituted phenyl-1,2,3-tria...
Figure 1: Experimental Raman spectra of the alkyne 4 and triazole products 5–8. Bands attributed to the vibra...
Figure 2: In situ Raman monitoring of a) mechanochemical formation of triazole 5 using copper(II) acetate mon...
Figure 3: a) In situ Raman monitoring for mechanochemical synthesis of 5 using brass balls and PMMA reaction ...
Figure 4: ESR spectra of samples obtained after milling by methods 2a (black), 2b (red) and 2c (blue). The in...
Figure 5: X-ray structure of the triazole compounds. (a) Molecular structure of 5, with the atom-numbering sc...
Synthesis of benzannelated sultams by intramolecular Pd-catalyzed arylation of tertiary sulfonamides
- Valentin A. Rassadin,
- Mirko Scholz,
- Anastasiia A. Klochkova,
- Armin de Meijere and
- Victor V. Sokolov
Beilstein J. Org. Chem. 2017, 13, 1932–1939, doi:10.3762/bjoc.13.187
- -quinodimethane intermediate 14 then, by [1,5]-hydrogen shift gives the ortho-benzylaniline-derived Schiff base 15, which undergoes cyclization to give the indoline derivative 16, and this by subsequent elimination of SO2 and protonation yields 17. The latter, like many indolines [46][47][48] probably is
Graphical Abstract
Scheme 1: A previous and a new approach to arene-annelated sultams.
Scheme 2: Pd-catalyzed cyclization of (2-iodophenyl)sulfonamides 3 and 5.
Scheme 3: Preparation of 4-methoxybenzyl-protected methyl 2-(N-o-iodoarylsulfamoyl)acetates 8. Reagents and c...
Scheme 4: Synthesis of arene-annelated sultams 10 by Pd-catalyzed intramolecular arylation of a C–H acidic me...
Figure 1: Structure of methyl 5-chloro-1-(4-methoxybenzyl)-1,3-dihydrobenzo[c]isothiazole-3-carboxylate-2,2-d...
Scheme 5: Palladium-catalyzed transformation of N-(2-iodophenyl)-N-(4-methoxybenzyl-benzylsulfonamide 12. Ar ...
Scheme 6: Palladium-catalyzed intramolecular arylation to yield a benzannelated six-membered sultam 21. Ar = ...
Scheme 7: An attempted and a successful removal of the PMB group from the sultam 10a.
Figure 2: Structure of methyl 1-(4-methoxybenzyl)-3-(nitrooxy)-1,3-dihydrobenzo[c]isothiazole-3-carboxylate-2...
Solvent-free sonochemistry: Sonochemical organic synthesis in the absence of a liquid medium
- Deborah E. Crawford
Beilstein J. Org. Chem. 2017, 13, 1850–1856, doi:10.3762/bjoc.13.179
- of employing sonochemistry. Conclusion In conclusion, the first examples of ultrasound induced solvent-free condensation reactions are reported, forming a Schiff base 1 (which has significant applications in catalysis) and a 1,3-indandione 2. It was concluded that one of the key parameters in these
Graphical Abstract
Figure 1: Typical laboratory employed planetary ball mill and ultrasonic bath.
Scheme 1: Reaction between o-vanillin and 1,2-phenylenediamine by ultrasonic irradiation for 60 minutes.
Figure 2: o-Vanillin in its flake form and 1,2-phenylenediamine in its bead form.
Figure 3: Clear separation of the reagents observed, with orange coated beads of 1,2-phenylenediamine residin...
Figure 4: Chemical structures of the products obtained from the reaction between o-vanillin and 1,2-phenylene...
Figure 5: Reaction mixture before and after ultrasonic irradiation for 60 minutes.
Figure 6: 1H NMR spectrum of diimine 1 in CDCl3/EtOD.
Scheme 2: Aldol reaction between ninhydrin and dimedone to form 2.
Figure 7: 1H NMR spectrum of 1,3-indandione 2 in DMSO-d6.
New tricks of well-known aminoazoles in isocyanide-based multicomponent reactions and antibacterial activity of the compounds synthesized
- Maryna V. Murlykina,
- Maryna N. Kornet,
- Sergey M. Desenko,
- Svetlana V. Shishkina,
- Oleg V. Shishkin,
- Aleksander A. Brazhko,
- Vladimir I. Musatov,
- Erik V. Van der Eycken and
- Valentin A. Chebanov
Beilstein J. Org. Chem. 2017, 13, 1050–1063, doi:10.3762/bjoc.13.104
- temperature for 24 h (method A) resulting in the formation of imidazopyrazoles 4a–m (Table 1, entries 1–13). This condensation was also carried out in TFE or MeOH with addition of HClO4 (10 mol %), but a significant amount of Schiff base 5 (Table 1) was observed in this case. The reaction involving aldehydes
Graphical Abstract
Scheme 1: Aminoazoles in GBB-3CR and Ugi-4CR.
Scheme 2: Reactivity of 5-amino-N-aryl-1H-pyrazole-4-carboxamide and 3-amino-5-methylisoxazole in GBB-3CR and...
Figure 1: Alternative structures A and B for compounds 4 and 6.
Figure 2: Selected data of HSQC and HMBC experiments for compound 4a.
Figure 3: Molecular structure of 3-(tert-butylamino)-2-(4-chlorophenyl)-N-(4-fluorophenyl)-1H-imidazo[1,2-b]p...
Figure 4: Selected data of NOE and HSQC experiments for compound 9d.
Figure 5: Molecular structure of N-(2-(tert-butylamino)-1-(4-chlorophenyl)-2-oxoethyl)-N-(5-methylisoxazol-3-...
Investigation of the action of poly(ADP-ribose)-synthesising enzymes on NAD+ analogues
- Sarah Wallrodt,
- Edward L. Simpson and
- Andreas Marx
Beilstein J. Org. Chem. 2017, 13, 495–501, doi:10.3762/bjoc.13.49
- experiments is summarised in Table 1. For illustration, Figure 3 shows the processing of derivative 1 by all the four ARTDs tested. Of note, it was previously reported [21] that the incubation of proteins with NAD+ analogues may result in non-enzymatic Schiff base formation of ADP-riboses with lysine residues
Graphical Abstract
Figure 1: NAD+ is used as a substrate by ARTDs to form MARylated and PARylated proteins. Depicted are alkyne-...
Figure 2: Workflow of the ADP-ribosylation assay. The protein of interest (POI) is ADP-ribosylated by the res...
Figure 3: SDS PAGE analysis of ADP-ribosylation of histone H1.2 with ARTD1, ARTD2, ARTD5 and ARTD6 using NAD+...
Figure 4: SDS PAGE analysis of ADP-ribosylation of histone H1.2 with ARTD2, ARTD5 and ARTD 6 using NAD+ analo...
Spectral and DFT studies of anion bound organic receptors: Time dependent studies and logic gate applications
- Srikala Pangannaya,
- Neethu Padinchare Purayil,
- Shweta Dabhi,
- Venu Mankad,
- Prafulla K. Jha,
- Satyam Shinde and
- Darshak R. Trivedi
Beilstein J. Org. Chem. 2017, 13, 222–238, doi:10.3762/bjoc.13.25
- ELEMENTOR Micro analysis system, varioMICRO CUBE CHNS. Synthesis of receptors R1 and R2: Receptors R1 and R2 were synthesized through a Schiff base condensation reaction of the corresponding aromatic aldehyde and amine (Scheme 5). Synthesis of (E)-5-(((2-hydroxynaphthalen-1-yl)methylene)amino
Graphical Abstract
Figure 1: Color change observed for R1 (4.5 × 10−5 Min DMSO) in the presence of 1 equiv of different anions (...
Figure 2: Color change observed for R2 (4.5 × 10−5 M in DMSO) in the presence of 1 equiv of different anions ...
Figure 3: UV–vis titration spectra of receptor R1 (4.5 × 10−5 M in DMSO) obtained by the incremental addition...
Figure 4: UV–vis titration spectra of receptor R1 (4.5 × 10−5 M in DMSO) obtained by the incremental addition...
Figure 5: B–H plot of the R1–F− complex at a selected wavelength of 477 nm.
Figure 6: B–H plot of the R1–AcO− complex at a selected wavelength of 492 nm.
Figure 7: UV–vis titration spectra of receptor R2 (4.5 × 10−5 M in DMSO) obtained by the incremental addition...
Figure 8: UV–vis titration spectra of receptor R2 (4.5 × 10–5 M in DMSO) obtained by the incremental addition...
Figure 9: B–H plot of the R2–F− complex at a selected wavelength of 560 nm.
Figure 10: B–H plot of the R2–AcO− complex at a selected wavelength of 560 nm.
Figure 11: Color change of receptor R1 upon the addition of NaF and mouthwash.
Figure 12: Color change of receptor R2 upon the addition of NaF and mouthwash.
Figure 13: Time dependent plot of first order rate equation to determine the rate constant from the UV–vis spe...
Figure 14: Time dependent plot of first order rate equation to determine the rate constant from the UV–vis spe...
Figure 15: 1H NMR titration spectra of R1 upon incremental addition of AcO− ion.
Figure 16: 1H NMR titration spectra of R2 upon incremental addition of AcO− ion.
Figure 17: Optimized structure of receptor R1; (a) HOMO, (b) LUMO.
Figure 18: Optimized structure of the receptor R2; (a) HOMO, (b) LUMO.
Figure 19: Optimized structure of the R1-F− complex; (a) HOMO, (b) LUMO.
Figure 20: Optimized structure of the R1-AcO− complex; (a) HOMO, (b) LUMO.
Figure 21: Optimized structure of the R2-F− complex; (a) HOMO, (b) LUMO.
Figure 22: Optimized structure of the R2-AcO− complex; (a) HOMO, (b) LUMO.
Scheme 1: Proposed binding mechanism of R1 with fluoride ion.
Scheme 2: Proposed binding mechanism of R1 with acetate ion.
Scheme 3: Possible binding mechanism of R2 with acetate ion.
Scheme 4: Proposed binding mechanism of R2 with fluoride ion.
Figure 23: Logic circuit for the “INHIBIT” gate of receptor R1.
Scheme 5: General scheme for the synthesis of receptors R1 and R2.
