Search for "Knoevenagel" in Full Text gives 103 result(s) in Beilstein Journal of Organic Chemistry.
Beilstein J. Org. Chem. 2021, 17, 977–982, doi:10.3762/bjoc.17.79
Graphical Abstract
Figure 1: Biologically relevant 2-oxydibenzofuran-containing structures 1–6.
Figure 2: Representative bioactive structures containing benzofuro-fused pyridine analogues 7–9.
Scheme 1: Strategy for metal-free access to benzofuropyridine 13.
Scheme 2: Electrophilic aromatic substitution of 6-hydroxybenzofuro[2,3-b]pyridine (13).
Scheme 3: Synthesis of isomeric oxazole-fused derivatives.
Scheme 4: Fused derivatives from 16.
Beilstein J. Org. Chem. 2021, 17, 819–865, doi:10.3762/bjoc.17.71
Graphical Abstract
Figure 1: Marketed drugs with acridine moiety.
Scheme 1: Synthesis of 4-arylacridinediones.
Scheme 2: Proposed mechanism for acridinedione synthesis.
Scheme 3: Synthesis of tetrahydrodibenzoacridinones.
Scheme 4: Synthesis of naphthoacridines.
Scheme 5: Plausible mechanism for naphthoacridines.
Figure 2: Benzoazepines based potent molecules.
Scheme 6: Synthesis of azepinone.
Scheme 7: Proposed mechanism for azepinone formation.
Scheme 8: Synthesis of benzoazulenen-1-one derivatives.
Scheme 9: Proposed mechanism for benzoazulene-1-one synthesis.
Figure 3: Indole-containing pharmacologically active molecules.
Scheme 10: Synthesis of functionalized indoles.
Scheme 11: Plausible mechanism for the synthesis of functionalized indoles.
Scheme 12: Synthesis of spirooxindoles.
Scheme 13: Synthesis of substituted spirooxindoles.
Scheme 14: Plausible mechanism for the synthesis of substituted spirooxindoles.
Scheme 15: Synthesis of pyrrolidinyl spirooxindoles.
Scheme 16: Proposed mechanism for pyrrolidinyl spirooxindoles.
Figure 4: Pyran-containing biologically active molecules.
Scheme 17: Synthesis of functionalized benzopyrans.
Scheme 18: Plausible mechanism for synthesis of benzopyran.
Scheme 19: Synthesis of indoline-spiro-fused pyran derivatives.
Scheme 20: Proposed mechanism for indoline-spiro-fused pyran.
Scheme 21: Synthesis of substituted naphthopyrans.
Figure 5: Marketed drugs with pyrrole ring.
Scheme 22: Synthesis of tetra-substituted pyrroles.
Scheme 23: Mechanism for silica-supported PPA-SiO2-catalyzed pyrrole synthesis.
Scheme 24: Synthesis of pyrrolo[1,10]-phenanthrolines.
Scheme 25: Proposed mechanism for pyrrolo[1,10]-phenanthrolines.
Figure 6: Marketed drugs and molecules containing pyrimidine and pyrimidinones skeletons.
Scheme 26: MWA-MCR pyrimidinone synthesis.
Scheme 27: Two proposed mechanisms for pyrimidinone synthesis.
Scheme 28: MWA multicomponent synthesis of dihydropyrimidinones.
Scheme 29: Proposed mechanism for dihydropyrimidinones.
Figure 7: Biologically active fused pyrimidines.
Scheme 30: MWA- MCR for the synthesis of pyrrolo[2,3-d]pyrimidines.
Scheme 31: Proposed mechanism for pyrrolo[2,3-d]pyrimidines.
Scheme 32: Synthesis of substituted pyrrolo[2,3-d]pyrimidine-2,4-diones.
Scheme 33: Probable pathway for pyrrolo[2,3-d]pyrimidine-2,4-diones.
Scheme 34: Synthesis of pyridopyrimidines.
Scheme 35: Plausible mechanism for the synthesis of pyridopyrimidines.
Scheme 36: Synthesis of dihydropyridopyrimidine and dihydropyrazolopyridine.
Scheme 37: Proposed mechanism for the formation of dihydropyridopyrimidine.
Scheme 38: Synthesis of thiopyrano[4,3-d]pyrimidines.
Scheme 39: Plausible mechanism for the synthesis of thiopyrano[4,3-d]pyrimidines.
Scheme 40: Synthesis of decorated imidazopyrimidines.
Scheme 41: Proposed mechanism for imidazopyrimidine synthesis.
Figure 8: Pharmacologically active molecules containing purine bases.
Scheme 42: Synthesis of aza-adenines.
Scheme 43: Synthesis of 5-aza-7-deazapurines.
Scheme 44: Proposed mechanism for deazapurines synthesis.
Figure 9: Biologically active molecules containing pyridine moiety.
Scheme 45: Synthesis of steroidal pyridines.
Scheme 46: Proposed mechanism for steroidal pyridine.
Scheme 47: Synthesis of N-alkylated 2-pyridones.
Scheme 48: Two possible mechanisms for pyridone synthesis.
Scheme 49: Synthesis of pyridone derivatives.
Scheme 50: Postulated mechanism for synthesis of pyridone.
Figure 10: Biologically active fused pyridines.
Scheme 51: Benzimidazole-imidazo[1,2-a]pyridines synthesis.
Scheme 52: Mechanism for the synthesis of benzimidazole-imidazo[1,2-a]pyridines.
Scheme 53: Synthesis of pyrazolo[3,4-b]pyridine-5-spirocycloalkanedione derivatives.
Scheme 54: Proposed mechanism for spiro-pyridines.
Scheme 55: Functionalized macrocyclane-fused pyrazolo[3,4-b]pyridine derivatives.
Scheme 56: Mechanism postulated for macrocyclane-fused pyrazolo[3,4-b]pyridine.
Scheme 57: Generation of pyrazolo[3,4-b]pyridines.
Scheme 58: Proposed mechanism for the synthesis of pyrazolo[3,4-b]pyridines.
Scheme 59: Proposed mechanism for the synthesis of azepinoindole.
Figure 11: Pharmaceutically important molecules with quinoline moiety.
Scheme 60: Povarov-mediated quinoline synthesis.
Scheme 61: Proposed mechanism for Povarov reaction.
Scheme 62: Synthesis of pyrazoloquinoline.
Scheme 63: Plausible mechanism for pyrazoloquinoline synthesis.
Figure 12: Quinazolinones as pharmacologically significant scaffolds.
Scheme 64: Four-component reaction for dihydroquinazolinone.
Scheme 65: Proposed mechanism for dihydroquinazolinones.
Scheme 66: Synthesis purine quinazolinone and PI3K-δ inhibitor.
Scheme 67: Synthesis of fused benzothiazolo/benzoimidazoloquinazolinones.
Scheme 68: Proposed mechanism for fused benzothiazolo/benzoimidazoloquinazolinones.
Scheme 69: On-water reaction for synthesis of thiazoloquinazolinone.
Scheme 70: Proposed mechanism for the thiazoloquinazolinone synthesis.
Scheme 71: β-Cyclodextrin-mediated synthesis of indoloquinazolinediones.
Scheme 72: Proposed mechanism for synthesis of indoloquinazolinediones.
Figure 13: Triazoles-containing marketted drugs and pharmacologically active molecules.
Scheme 73: Cu(I) DAPTA-catalyzed 1,2,3-triazole formation.
Scheme 74: Mechanism for Cu(I) DAPTA-catalyzed triazole formation.
Scheme 75: Synthesis of β-hydroxy-1,2,3-triazole.
Scheme 76: Proposed mechanism for synthesis of β-hydroxy-1,2,3-triazoles.
Scheme 77: Synthesis of bis-1,2,4-triazoles.
Scheme 78: Proposed mechanism for bis-1,2,4-triazoles synthesis.
Figure 14: Thiazole containing drugs.
Scheme 79: Synthesis of a substituted thiazole ring.
Scheme 80: Synthesis of pyrazolothiazoles.
Figure 15: Chromene containing drugs.
Scheme 81: Magnetic nanocatalyst-mediated aminochromene synthesis.
Scheme 82: Proposed mechanism for the synthesis of chromenes.
Beilstein J. Org. Chem. 2020, 16, 2831–2853, doi:10.3762/bjoc.16.233
Graphical Abstract
Figure 1: Some selected self-sorting outcomes and their qualitative and quantitative assessment.
Figure 2: Illustration of an integrative vs a non-integrative self-sorting.
Figure 3: The pH-driven four-component 2-fold completive self-sorting based on host–guest chemistry.
Figure 4: (a) The monomers 5 and 6 and their H-bonding array. (b) The hydrogen-bonded octameric and tetrameri...
Figure 5: (a) Two new Zn4L6-type cages. (b) The encapsulation of C70 induced distinct reconstitutions within ...
Figure 6: The formation of octahedral cages (a) [Co6(10')4]12+ and (b) [Co6(11')4]12+. (c) The 2-fold complet...
Figure 7: Exchange of Ag+ for Au+ ions in poly-NHC ligand-based organometallic assemblies.
Figure 8: The reversible interconversion between the three-component rectangle [Cu4(16)2(17)2]4+ and the four...
Figure 9: a) Chemical structure of the monomer 20 with its quadruple hydrogen-bonding array and a metal-affin...
Figure 10: Communication between the nanoswitch 21 and the supramolecular assemblies [Cu4(22)2(24)2]4+ or [Cu6(...
Figure 11: (a) The chemical structures and cartoon representations of the switch 25, the decks 26 and 27, and ...
Figure 12: Double self-sorting leads to a catalytic machinery in SelfSORT-II, in which the 46 kHz-nanorotor ac...
Figure 13: ON/OFF control of a networked catalytic catch–release system.
Figure 14: A multicomponent information system for the reversible reconfiguration of switchable dual catalysis....
Figure 15: a) The chemically fueled cascaded ion translocation, monitored by distinct emission colors. b) Work...
Figure 16: Cyclic metallosupramolecular transformations.
Figure 17: Fully reversible multiple-state rearrangement of metallosupramolecular architectures depending upon...
Figure 18: The selective encapsulation and sequential release of guests in a self-sorted mixture of three tetr...
Figure 19: Two catalytic reactions are alternately controlled by a toggle nanoswitch.
Figure 20: A biped walking along a tetrahedral track and unfolding its catalytic action. Adapted with permissi...
Figure 21: A three state supramolecular AND logic gate.
Figure 22: Four-component nanorotor and its catalytic activity. Adapted with permission from (Biswas, P. K.; S...
Beilstein J. Org. Chem. 2020, 16, 2636–2644, doi:10.3762/bjoc.16.214
Graphical Abstract
Figure 1: Heteroacenes: tetrathienoacene (TTA), S,N-heteroacenes SN4, SN4', and SN4''.
Scheme 1: Synthesis of fused S,N-heterotetracene SN4 9 starting from thieno[3,2-b]thiophene (1).
Scheme 2: Synthesis of parent H-SN4 13 via the azide route.
Scheme 3: Synthesis of tetracyclic H-SN4 13 via the Cadogan route.
Scheme 4: Synthesis of tetracyclic indole derivative 19 via the Cadogan route.
Scheme 5: Synthesis of hexacyclic heteroacene SN4' 22 via the Cadogan route.
Scheme 6: Synthesis of heterotetracene SN4'' 33 via the azide and Buchwald–Hartwig amination route.
Figure 2: UV–vis absorption spectra of TTA, Hex-SN4 9, Pr-SN4'' 33 and fluorescence spectrum of 33 in THF at ...
Figure 3: Energy diagram of the frontier molecular orbitals of heterotetracenes TTA, 9, 13, 19, 22, and 33, a...
Beilstein J. Org. Chem. 2020, 16, 1881–1900, doi:10.3762/bjoc.16.156
Graphical Abstract
Figure 1: The benzimidazoles I–IV, dihydropyrimidinones/-thiones V–VIII, and 2-amino-4-aryl-3,5-dicarbonitril...
Scheme 1: NDL-catalyzed synthesis of i) 1,2-disubstituted benzimidazoles 3, ii) dihydropyrimidinones/-thiones ...
Figure 2: XRD pattern of the NDL catalyst.
Figure 3: FTIR spectrum of the NDL catalyst.
Figure 4: Raman spectrum of the NDL catalyst.
Figure 5: SEM images of the NDL catalyst.
Figure 6: EDAX analysis of the NDL catalyst.
Scheme 2: Unexpected formation of the bisimine I, 3h, from o-phenylenediamine (1) and salicylaldehyde (2h).
Figure 7: 1H NMR spectrum of 2,2'-((1E,1'E)-(1,2-phenylenebis(azanylylidene))bis (methanylylidene))diphenol (...
Figure 8: XRD pattern of a) the fresh NDL catalyst; b) the recovered NDL catalyst after the 7th cycle of the ...
Beilstein J. Org. Chem. 2020, 16, 1495–1549, doi:10.3762/bjoc.16.125
Graphical Abstract
Figure 1: A) Bar chart of the publications per year for the topics “Photocatalysis” (49,662 instances) and “P...
Figure 2: A) Professor Giacomo Ciamician and Dr. Paolo Silber on their roof laboratory at the University of B...
Scheme 1: PRC trifluoromethylation of N-methylpyrrole (1) using hazardous gaseous CF3I safely in a flow react...
Figure 3: A) Unit cells of the three most common crystal structures of TiO2: rutile, brookite, and anatase. R...
Figure 4: Illustration of the key semiconductor photocatalysis events: 1) A photon with a frequency exceeding...
Figure 5: Photocatalytic splitting of water by oxygen vacancies on a TiO2(110) surface. Reprinted with permis...
Figure 6: Proposed adsorption modes of A) benzene, B) chlorobenzene, C) toluene, D) phenol, E) anisole, and F...
Figure 7: Structures of the sulfonate-containing organic dyes RB5 (3) and MX-5B (4) and the adsorption isothe...
Figure 8: Idealised triclinic unit cell of a g-C3N4 type polymer, displaying possible hopping transport scena...
Figure 9: Idealised structure of a perfect g-C3N4 sheet. The central unit highlighted in red represents one t...
Figure 10: Timeline of the key processes of charge transport following the photoexcitation of g-C3N4, leading ...
Scheme 2: Photocatalytic bifunctionalisation of heteroarenes using mpg-C3N4, with the selected examples 5 and ...
Figure 11: A) Structure of four linear conjugated polymer photocatalysts for hydrogen evolution, displaying th...
Figure 12: Graphical representation of the common methods used to immobilise molecular photocatalysts (PC) ont...
Figure 13: Wireless light emitter-supported TiO2 (TiO2@WLE) HPCat spheres powered by resonant inductive coupli...
Figure 14: Graphical representation of zinc–perylene diimide (Zn-PDI) supramolecular assembly photocatalysis v...
Scheme 3: Upconversion of NIR photons to the UV frequency by NaYF4:Yb,Tm nanocrystals sequentially coated wit...
Figure 15: Types of reactors employed in heterogeneous photocatalysis in flow. A) Fixed bed reactors and the s...
Figure 16: Electrochemical potential of common semiconductor, transition metal, and organic dye-based photocat...
Scheme 4: Possible mechanisms of an immobilised molecular photoredox catalyst by oxidative or reductive quenc...
Scheme 5: Scheme of the CMB-C3N4 photocatalytic decarboxylative fluorination of aryloxyacetic acids, with the...
Scheme 6: Scheme of the g-C3N4 photocatalytic desilylative coupling reaction in flow and proposed mechanism [208].
Scheme 7: Proposed mechanism of the radical cyclisation of unsaturated alkyl 2-bromo-1,3-dicarbonyl compounds...
Scheme 8: N-alkylation of benzylamine and schematic of the TiO2-coated microfluidic device [213].
Scheme 9: Proposed mechanism of the Pt@TiO2 photocatalytic deaminitive cyclisation of ʟ-lysine (23) to ʟ-pipe...
Scheme 10: A) Proposed mechanism for the photocatalytic oxidation of phenylboronic acid (24). B) Photos and SE...
Scheme 11: Proposed mechanism for the DA-CMP3 photocatalytic aza-Henry reaction performed in a continuous flow...
Scheme 12: Proposed mechanism for the formation of the cyclic product 32 by TiO2-NC HPCats in a slurry flow re...
Scheme 13: Reaction scheme for the photocatalytic synthesis of homo and hetero disulfides in flow and scope of...
Scheme 14: Reaction scheme for the MoOx/TiO2 HPCat oxidation of cyclohexane (34) to benzene. The graph shows t...
Scheme 15: Proposed mechanism of the TiO2 HPC heteroarene C–H functionalisation via aryl radicals generated fr...
Scheme 16: Scheme of the oxidative coupling of benzylamines with the HOTT-HATN HPCat and selected examples of ...
Scheme 17: Photocatalysis oxidation of benzyl alcohol (40) to benzaldehyde (41) in a microflow reactor coated ...
Figure 17: Mechanisms of Dexter and Forster energy transfer.
Scheme 18: Continuous flow process for the isomerisation of alkenes with an ionic liquid-immobilised photocata...
Scheme 19: Singlet oxygen synthetic step in the total synthesis of canataxpropellane [265].
Scheme 20: Scheme and proposed mechanism of the singlet oxygen photosensitisation by CMP_X HPCats, with the st...
Scheme 21: Structures of CMP HPCat materials applied by Vilela and co-workers for the singlet oxygen photosens...
Scheme 22: Polyvinylchloride resin-supported TDCPP photosensitisers applied for singlet oxygen photosensitisat...
Scheme 23: Structure of the ionically immobilised TPP photosensitiser on amberlyst-15 ion exchange resins (TPP...
Scheme 24: Photosensitised singlet oxygen oxidation of citronellol (46) in scCO2, with automatic phase separat...
Scheme 25: Schematic of PS-Est-BDP-Cl2 being applied for singlet oxygen photosensitisation in flow. A) Pseudo-...
Scheme 26: Reaction scheme of the singlet oxygen oxidation of furoic acid (54) using a 3D-printed microfluidic...
Figure 18: A) Photocatalytic bactericidal mechanism by ROS oxidative cleavage of membrane lipids (R = H, amino...
Figure 19: A) Suggested mechanisms for the aqueous pollutant degradation by TiO2 in a slurry flow reactor [284-287]. B)...
Figure 20: Schematic of the flow system used for the degradation of aqueous oxytetracycline (56) solutions [215]. M...
Scheme 27: Degradation of a salicylic acid (57) solution by a coupled solar photoelectro-Fenton (SPEF) process...
Figure 21: A) Schematic flow diagram using the TiO2-coated NETmix microfluidic device for an efficient mass tr...
Beilstein J. Org. Chem. 2020, 16, 1320–1334, doi:10.3762/bjoc.16.113
Graphical Abstract
Figure 1: Fused aza-hetero polycyclic frames and natural pyrrolizine- and isoindole-containing alkaloids.
Scheme 1: Synthetic approaches for the preparation of pyrrolo-fused aza-hetero polycyclic frames.
Scheme 2: Preparation of 1,2-substituted pyrroles 8a–f and 8i,j.
Scheme 3: Diels–Alder cycloadditions of pyrroles 8a–j and 16a–b with maleimides 7b–c.
Figure 2: Structures of 9m (a) and 10m (b) as determined by single-crystal X-ray diffraction crystallography ...
Scheme 4: Pd(0)-catalyzed intramolecular Heck cross-coupling reaction of 2-vinylpyrroles 8c,d and 8g.
Scheme 5: Synthesis of 2-vinylpyrroles 8k,l and their Pd(0)-catalyzed intramolecular Heck cross-coupling to p...
Scheme 6: Diastereoselective Diels–Alder reaction of pyrrolo[2,1-a]isoindole 18a with 7c.
Scheme 7: Synthetic approach to the fused aza-heterocyclic pentacycle 12.
Figure 3: M06-2X/6-31+G(d,p) Optimized geometry for each of the SCs (a and d), TSs (b and e) and ADs (c and f...
Figure 4: M06-2X/6-31+G(d,p) Optimized geometry for each of the TSs of the Diels–Alder reactions of dienes 8b...
Figure 5: M06-2X/6-31+G(d,p) Optimized geometry of the endo SCs (a) and TSs (b) for the Diels–Alder reaction ...
Beilstein J. Org. Chem. 2020, 16, 1022–1050, doi:10.3762/bjoc.16.91
Graphical Abstract
Figure 1: Categories I–V of fluorinated phenylalanines.
Scheme 1: Synthesis of fluorinated phenylalanines via Jackson’s method.
Scheme 2: Synthesis of all-cis-tetrafluorocyclohexylphenylalanines.
Scheme 3: Synthesis of ʟ-4-[sulfono(difluoromethyl)]phenylalanine (nPt: neopentyl, TCE: trichloroethyl).
Scheme 4: Synthesis of ʟ-4-[sulfono(difluoromethyl)]phenylalanine derivatives 17.
Scheme 5: Synthesis of fluorinated Phe analogues from Cbz-protected aminomalonates.
Scheme 6: Synthesis of tetrafluorophenylalanine analogues via the 3-methyl-4-imidazolidinone auxiliary 25.
Scheme 7: Synthesis of tetrafluoro-Phe derivatives via chiral auxiliary 31.
Scheme 8: Synthesis of 2,5-difluoro-Phe and 2,4,5-trifluoro-Phe via Schöllkopf reagent 34.
Scheme 9: Synthesis of 2-fluoro- and 2,6-difluoro Fmoc-Phe derivatives starting from chiral auxiliary 39.
Scheme 10: Synthesis of 2-[18F]FPhe via chiral auxiliary 43.
Scheme 11: Synthesis of FPhe 49a via photooxidative cyanation.
Scheme 12: Synthesis of FPhe derivatives via Erlenmeyer azalactone synthesis.
Scheme 13: Synthesis of (R)- and (S)-2,5-difluoro Phe via the azalactone method.
Scheme 14: Synthesis of 3-bromo-4-fluoro-(S)-Phe (65).
Scheme 15: Synthesis of [18F]FPhe via radiofluorination of phenylalanine with [18F]F2 or [18F]AcOF.
Scheme 16: Synthesis of 4-borono-2-[18F]FPhe.
Scheme 17: Synthesis of protected 4-[18F]FPhe via arylstannane derivatives.
Scheme 18: Synthesis of FPhe derivatives via intermediate imine formation.
Scheme 19: Synthesis of FPhe derivatives via Knoevenagel condensation.
Scheme 20: Synthesis of FPhe derivatives 88a,b from aspartic acid derivatives.
Scheme 21: Synthesis of 2-(2-fluoroethyl)phenylalanine derivatives 93 and 95.
Scheme 22: Synthesis of FPhe derivatives via Zn2+ complexes.
Scheme 23: Synthesis of FPhe derivatives via Ni2+ complexes.
Scheme 24: Synthesis of 3,4,5-trifluorophenylalanine hydrochloride (109).
Scheme 25: Synthesis of FPhe derivatives via phenylalanine aminomutase (PAM).
Scheme 26: Synthesis of (R)-2,5-difluorophenylalanine 115.
Scheme 27: Synthesis of β-fluorophenylalanine via 2-amino-1,3-diol derivatives.
Scheme 28: Synthesis of β-fluorophenylalanine derivatives via the oxazolidinone chiral auxiliary 122.
Scheme 29: Synthesis of β-fluorophenylalanine from pyruvate hemiketal 130.
Scheme 30: Synthesis of β-fluorophenylalanine (136) via fluorination of β-hydroxyphenylalanine (137).
Scheme 31: Synthesis of β-fluorophenylalanine from aziridine derivatives.
Scheme 32: Synthesis of β-fluorophenylalanine 136 via direct fluorination of pyruvate esters.
Scheme 33: Synthesis of β-fluorophenylalanine via fluorination of ethyl 3-phenylpyruvate enol using DAST.
Scheme 34: Synthesis of β-fluorophenylalanine derivatives using photosensitizer TCB.
Scheme 35: Synthesis of β-fluorophenylalanine derivatives using Selectflour and dibenzosuberenone.
Scheme 36: Synthesis of protected β-fluorophenylalanine via aziridinium intermediate 150.
Scheme 37: Synthesis of β-fluorophenylalanine derivatives via fluorination of α-hydroxy-β-aminophenylalanine d...
Scheme 38: Synthesis of β-fluorophenylalanine derivatives from α- or β-hydroxy esters 152a and 155.
Scheme 39: Synthesis of a series of β-fluoro-Phe derivatives via Pd-catalyzed direct fluorination of β-methyle...
Scheme 40: Synthesis of series of β-fluorinated Phe derivatives using quinoline-based ligand 162 in the Pd-cat...
Scheme 41: Synthesis of β,β-difluorophenylalanine derivatives from 2,2-difluoroacetaldehyde derivatives 164a,b....
Scheme 42: Synthesis of β,β-difluorophenylalanine derivatives via an imine chiral auxiliary.
Scheme 43: Synthesis of α-fluorophenylalanine derivatives via direct fluorination of protected Phe 174.
Figure 2: Structures of PET radiotracers of 18FPhe derivatives.
Figure 3: Structures of melfufen (179) and melphalan (180) anticancer drugs.
Figure 4: Structure of gastrazole (JB95008, 181), a CCK2 receptor antagonist.
Figure 5: Dual CCK1/CCK2 antagonist 182.
Figure 6: Structure of sitagliptin (183), an antidiabetic drug.
Figure 7: Structure of retaglpitin (184) and antidiabetic drug.
Figure 8: Structure of evogliptin (185), an antidiabetic drug.
Figure 9: Structure of LY2497282 (186) a DPP-4 inhibitor for the treatment of type II diabetes.
Figure 10: Structure of ulimorelin (187).
Figure 11: Structure of GLP1R (188).
Figure 12: Structures of Nav1.7 blockers 189 and 190.
Beilstein J. Org. Chem. 2020, 16, 904–916, doi:10.3762/bjoc.16.82
Graphical Abstract
Scheme 1: Photo- or cation-induced ring-opening reaction of spirooxazine 1aSO; Mn+ = Pb2+, La3+, Eu3+, Tb3+ [17].
Scheme 2: Synthesis of the spirooxazine–quinolizinium conjugates 3a and 3b.
Figure 1: Colors of the solutions resulting from the addition of metal ions (c = 50 µM) to derivative 3a (c =...
Figure 2: Spectrophotometric titration of 3a (A) and 3b (B) (c = 20 µM) with Cu(BF4)2 (c = 2.44 mM) in MeCN. ...
Figure 3: Absorption (A) and fluorescence spectrum (B) of 3a in MeCN (c = 5 µM) in the absence (black) and in...
Figure 4: Emission colors of solutions resulting from the addition of metal ions (c = 50 µM) to derivative 3a...
Scheme 3: Cu2+-induced formation of the oxazole derivatives 4a and 4b.
Figure 5: 1H NMR spectra (600 MHz, 6.4–9.4 ppm) of 3a (c = 2.0 mM) in the absence (A) and in the presence (B–...
Figure 6: Spectral changes of 3a (c = 20 µM) upon the addition of Cu2+ (A) and Fe3+ (B) (cM+ = 60 µM) in MeCN...
Scheme 4: Proposed mechanism for the formation of the oxazole derivatives 4a and 4b (cf. Scheme 3); Mn+ = Cu2+, Fe3+,...
Beilstein J. Org. Chem. 2020, 16, 190–199, doi:10.3762/bjoc.16.22
Graphical Abstract
Scheme 1: Synthesis of 4-(2-fluorophenyl)-7-methoxycoumarin (6).
Figure 1: 1H NMR spectra for the “aromatic” region of coumarin 6; comparison of 1H spectrum and 1H-{19F} spec...
Figure 2: 13C NMR spectra for coumarin 5 and 6; showing the splitting of the signal corresponding to C5.
Figure 3: 19F,1H-HOESY NMR spectrum for coumarin 6 illustrating two through-space interactions.
Figure 4: Superposition of single-crystal X-ray structure (red) and DFT-optimized structure (green); RMSD 0.3...
Figure 5: DFT-optimized structure for coumarin (6).
Figure 6: Plots of relative energy (black trace, no units), interatomic distance F–H5 (red trace, Å), interat...
Figure 7: Short contacts within the single-crystal X-ray structure of coumarin 6.
Beilstein J. Org. Chem. 2019, 15, 2774–2781, doi:10.3762/bjoc.15.269
Graphical Abstract
Scheme 1: Conventional method of synthesis of thiazolidine-2,4-dione derivatives.
Scheme 2: [2 + 2 + 2] Cyclotrimerization of N-methylthiazolidinedione.
Scheme 3: Unexpected product 5b obtained in the attempted NH-protection of thiazolidinedione with (Boc)2O.
Figure 1: Comparison of 13C NMR values of 9 and 5b.
Scheme 4: [2 + 2 + 2] Cyclotrimerization of dipropargylthiazolidinediones with propargyl halides.
Scheme 5: Formation of sultine 13 from compound 8b followed by DA reaction.
Scheme 6: Dipropargylation of 2,4-thiazolidinedione derivatives.
Scheme 7: [2 + 2 + 2] Cycloaddition in the presence of Wilkinson’s catalyst.
Scheme 8: N-Ester derivative 18 hydrolysis to N-acid derivative 22.
Scheme 9: Synthesis of triazolo derivative 24 via click reaction.
Beilstein J. Org. Chem. 2019, 15, 1872–1889, doi:10.3762/bjoc.15.183
Graphical Abstract
Figure 1: Some di- and mono-styryl dyes previously reported as fluorescent “light-up” probes for G4-DNA and R...
Figure 2: Design of a library of di- and mono-styryl dyes. Counter-ions are omitted for the sake of clarity.
Scheme 1: A, B) General synthesis of A) distyryl and B) mono-styryl dyes via Knoevenagel condensation route. ...
Scheme 2: Synthesis of I3–5 and I15.
Figure 3: Representative absorption spectra of distyryl dyes: A) 1d, B) 1ð, C) 1f, D) 1u, E) 10a and F) 12a i...
Figure 4: Representative absorption spectra of the distyryl dyes (c = 10 µM in MeOH) demonstrating the influe...
Figure 5: Heat map of the relative emission intensity enhancement (I/I0) of styryl dyes and thioflavin T (ThT...
Figure 6: Analysis of the light-up response matrix of the dyes. The average light-up factor of each dye with ...
Figure 7: PC1 vs PC2 plot obtained from the principal component analysis of the light-up data matrix for all ...
Figure 8: Dual-dye conformational analysis of an extended panel of 33 DNA oligonucleotides. This is performed...
Figure 9: Selected probes featuring high fluorimetric response towards G4 structures.
Figure 10: Photographs of solutions of A) distyryl dyes 1p and 1u; B) mono-styryl dyes 17a and 18a, in the abs...
Beilstein J. Org. Chem. 2019, 15, 1781–1785, doi:10.3762/bjoc.15.171
Graphical Abstract
Figure 1: Aurone ring system and numbering.
Figure 2: Aurone syntheses.
Figure 3: UV–vis spectral comparisons in acetonitrile.
Figure 4: Fabric dying and photobleaching. The top two sets show dyed fabric strips with premordant, simultan...
Beilstein J. Org. Chem. 2019, 15, 1758–1768, doi:10.3762/bjoc.15.169
Graphical Abstract
Figure 1: Molecular structures of the two target compounds BOD-TTPA-alk and BOD-TTPA, and the chemical struct...
Figure 2: a) Geometrical optimization of four representative BODIPY-based materials for DSSCs application. b)...
Figure 3: Predicted absorption spectra of the four dyes.
Figure 4: Synthetic scheme of the selected materials. a) hydroxylamine hydrochloride, NaHCO3, DMSO, 60 °C the...
Figure 5: a) Absorption spectra of compounds BOD-TTPA-alk and BOD-TTPA (THF, ≈10−6 M, 25 °C). b) Absorbance s...
Figure 6: J(V) curves of the best performing DSSCs devices sensitized with compounds BOD-TTPA-alk (blue trace...
Figure 7: Photovoltaic parameters evolution with the increasing concentration of tBP in the electrolyte.
Beilstein J. Org. Chem. 2019, 15, 1612–1704, doi:10.3762/bjoc.15.165
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.
Beilstein J. Org. Chem. 2019, 15, 1236–1256, doi:10.3762/bjoc.15.121
Graphical Abstract
Figure 1: Structures of natural steroids of A) animal and B) plant origin.
Scheme 1: Synthesis of a steroidal β-lactam by Ugi reaction of a cholanic aldehyde [14].
Scheme 2: Synthetic route to steroidal 2,5-diketopiperazines based on a diastereoselective Ugi-4CR with an an...
Scheme 3: Multicomponent synthesis of a heterocycle–steroid hybrid using a ketosteroid as carbonyl component [18]....
Scheme 4: Synthesis of peptidomimetic–steroid hybrids using the Ugi-4CR with spirostanic amines and carboxyli...
Scheme 5: Synthesis of azasteroids using the Ugi-4CR with androstanic and pregnanic carboxylic acids [22].
Figure 2: Ugi-4CR-derived library of androstanic azasteroids with diverse substitution patterns at the phenyl...
Scheme 6: Synthesis of 4-azacholestanes by an intramolecular Ugi-4C-3R [26].
Scheme 7: Synthesis of amino acid–steroid hybrid by multiple Ugi-4CR using steroidal isocyanides [29].
Scheme 8: Synthesis of ecdysteroid derivatives by Ugi-4CR using a steroidal isocyanide [30].
Scheme 9: Stereoselective multicomponent synthesis of a steroid–tetrahydropyridine hybrid using a chiral bifu...
Scheme 10: Pd(II)-catalyzed three-component reaction with an alkynyl seco-cholestane [34].
Scheme 11: Multicomponent synthesis of steroid–thiazole hybrids from a steroidal ketone [36].
Scheme 12: Synthesis of cholanic pseudo-peptide derivatives by novel MCRs based on the reactivity of ynamide [37,38].
Scheme 13: Synthesis of steroid-fused pyrimidines and pyrimidones using the Biginelli-3CR [39,42,43].
Scheme 14: Synthesis of steroidal pyridopyrimidines by a reaction sequence comprising a 4CR followed by a post...
Scheme 15: Synthesis of steroid-fused pyrimidines by MCR of 2-hydroxymethylene-3-ketosteroids [46].
Scheme 16: Synthesis of steroid-fused naphthoquinolines by the Kozlov–Wang MCR using ketosteroids [50,51].
Scheme 17: Conjugation of steroids to carbohydrates and peptides by the Ugi-4CR [62,63].
Scheme 18: Solid-phase multicomponent conjugation of peptides to steroids by the Ugi-4CR [64].
Scheme 19: Solid-phase multicomponent conjugation of peptides to steroids by the Petasis-3CR [68].
Scheme 20: Synthesis of steroidal macrobicycles (cages) by multiple multicomponent macrocyclizations based on ...
Scheme 21: One-pot synthesis of steroidal cages by double Ugi-4CR-based macrocyclizations [76].
Beilstein J. Org. Chem. 2019, 15, 1141–1148, doi:10.3762/bjoc.15.110
Graphical Abstract
Scheme 1: Catalyzed mechanochemical Knoevenagel condensation of fluorobenzaldehydes and malonodinitrile. The ...
Figure 1: Comparison of XRPD pattern of malonodinitrile (2) and (p-fluorobenzylidene) malonodinitrile (3a). T...
Figure 2: a) XRPD pattern of (p-fluorobenzylidene)malonodinitrile (3a) direct after the synthesis with differ...
Figure 3: Mass spectra of the different products of 3a. Red: peak off the molecular ion [M + H]+ of piperidin...
Figure 4: a) In situ XRPD pattern of the mechanochemical Knoevenagel condensation of 1a and 2 with 2 µL catal...
Figure 5: Comparison of XRPD patterns of both polymorphs of the product 3a. Red: triclinic polymorph t3a. Blu...
Figure 6: Results of multivariate data analysis of Raman spectra for 30 Hz milling experiments. Principal com...
Beilstein J. Org. Chem. 2019, 15, 1032–1045, doi:10.3762/bjoc.15.101
Graphical Abstract
Figure 1: 2-Aminoimidazole alkaloids from marine sponges.
Figure 2: The Knoevenagel–Michael adduct [24] and expected products.
Scheme 1: The three component condensation of imidazo[1,2-a]pyridine, aldehydes and Meldrum’s acid described ...
Figure 3: Molecular structure of 1-([1,1'-biphenyl]-4-yl)-5-oxo-7-phenyl-6,7-dihydro-5H-pyrrolo[1,2-c]imidazo...
Scheme 2: Two forms of cation 9i.
Figure 4: Molecular structure of 3-(2-amino-4-phenyl-1H-imidazol-5-yl)-3-(p-tolyl)propanoic acid 11b accordin...
Scheme 3: Three forms of the compound 11b in the crystal phase.
Scheme 4: Synthesis of the mixture of compounds 13 and 14.
Figure 5: Molecular structure of aminoimidazo[1,2-c]pyrrole 16a according to X-ray diffraction data. Thermal ...
Scheme 5: Resonance structures of 16a.
Figure 6: 3,3’-Spirooxindole alkaloids.
Figure 7: Molecular structure of aminoimidazo[1,2-c]pyrrole 19a according to X-ray diffraction data. Thermal ...
Scheme 6: Resonance structures of 19a.
Beilstein J. Org. Chem. 2018, 14, 3078–3087, doi:10.3762/bjoc.14.287
Graphical Abstract
Figure 1: Biologically relevant imidazo[1,2-a]pyridines and chromenes.
Scheme 1: Domino formation of imidazopyridines and current work.
Scheme 2: Scope of the reaction between N-(cyanomethyl)pyridinium chloride, o-hydroxybenzaldehydes, and nitro...
Scheme 3: Scope of the reaction of o-hydroxybenzaldehydes with N-(cyanomethyl)pyridinium chloride and indoles...
Scheme 4: Scope of the nucleophiles in the reaction of o-hydroxyarylaldehydes with N-(cyanomethyl)pyridinium ...
Scheme 5: N-(Cyanomethyl)thieno[2,3-c]pyridinium chloride (15) and 6-(cyanomethyl)-1-methyl-1H-pyrrolo[2,3-c]...
Figure 2: General view of the molecule 7b in the crystal state (CCDC 1849215). Anisotropic displacement param...
Scheme 6: The presumed mechanism for the formation of target chromenoimidazopyridines (reaction 1) and additi...
Beilstein J. Org. Chem. 2018, 14, 2907–2915, doi:10.3762/bjoc.14.269
Graphical Abstract
Figure 1: Examples of biologically important cycloalkyl-fused pyridines.
Scheme 1: Synthesis of 3-oxopropanenitriles 3.
Scheme 2: Proposed mechanism for the formation of 7f.
Scheme 3: Synthesis of indole–cyclododeca[b]pyridine-3-carbonitriles 7 and 14.
Figure 2: Axial chirality due to restricted C–C bond rotation (representative cases).
Figure 3: ORTEP diagram of 12r.
Scheme 4: Synthesis of indole–cycloalkyl[b]pyridine-3-carbonitrile hybrids 15–18.
Figure 4: ORTEP diagram of 16f.
Beilstein J. Org. Chem. 2018, 14, 2853–2860, doi:10.3762/bjoc.14.264
Graphical Abstract
Scheme 1: Malonate-based retrosynthesis of α-amino esters.
Scheme 2: Some side products and synthesis of α-amino ester 10.
Scheme 3: Syntheses of α-amino esters 22, 24, 26, 28 and 33.
Scheme 4: Syntheses of α-amino esters 38, 41 and 46a,b.
Scheme 5: Syntheses of α-amino esters 53 and 58.
Beilstein J. Org. Chem. 2018, 14, 2745–2770, doi:10.3762/bjoc.14.253
Graphical Abstract
Figure 1: Different types of sulfonated materials as acid catalysts.
Scheme 1: Synthetic route of 3-methyl-1-sulfo-1H-imidazolium metal chloride ILs and their catalytic applicati...
Scheme 2: Synthetic route of 1,3-disulfo-1H-imidazolium transition metal chloride ILs and their catalytic app...
Scheme 3: Synthetic route of 1,3-disulfoimidazolium carboxylate ILs and their catalytic applications in the s...
Scheme 4: Synthetic route of [BiPy](HSO3)2Cl2 and [Dsim]HSO4 ILs and their catalytic applications for the syn...
Scheme 5: The catalytic applications of (C4(DABCO-SO3H)2·4Cl) IL for the synthesis of spiro-isatin derivative...
Scheme 6: The catalytic applications of (C4(DABCO-SO3H)2·4Cl) IL for the synthesis of bis 2-amino-4H-pyran de...
Scheme 7: The synthetic route of N,N-disulfo-1,1,3,3-tetramethylguanidinium carboxylate ILs and their catalyt...
Scheme 8: The catalytic application of 1-methyl-3-sulfo-1H-imidazolium tetrachloroferrate IL in the synthesis...
Scheme 9: The synthetic route of 3-sulfo-1H-imidazolopyrimidinium hydrogen sulfate IL and its catalytic appli...
Scheme 10: The results for the synthesis of bis(indolyl)methanes and di(bis(indolyl)methyl)benzenes in the pre...
Scheme 11: The catalytic applications of 1-(1-sulfoalkyl)-3-methylimidazolium chloride acidic ILs for the hydr...
Scheme 12: The synthetic route of immobilized 1,4-diazabicyclo[2.2.2]octanesulfonic acid chloride on SiO2 and ...
Scheme 13: The catalytic application of a silica-bonded sulfoimidazolium chloride for the synthesis of 12-aryl...
Scheme 14: The synthetic route of the SBA-15-Ph-SO3H and its catalytic applications for the synthesis of 2H-in...
Scheme 15: The synthetic route for heteropolyanion-based ionic liquids immobilized on mesoporous silica SBA-15...
Scheme 16: Some mechanism aspects of SSA catalyst for the protection of amine derivatives.
Scheme 17: The synthetic route for MWCNT-SO3H and its catalytic application for the synthesis of N-substituted...
Scheme 18: The sulfonic acid-functionalized polymers (P-SO3H) covalently grafted on multi-walled carbon nanotu...
Scheme 19: The transesterification reaction in the presence of S-MWCNTs.
Scheme 20: The synthetic route for the new hypercrosslinked supermicroporous polymer via the Friedel–Crafts al...
Scheme 21: The synthetic route for a new microporous copolymer via the Friedel–Crafts alkylation reaction of t...
Scheme 22: The synthetic route for sulfonated polynaphthalene and its catalytic application for the amidoalkyl...
Scheme 23: The synthetic route of the acidic carbon material and its catalytic application in the etherificatio...
Scheme 24: The synthetic route of the acidic carbon materials and their catalytic applications for the esterif...
Scheme 25: The sulfonated MWCNTs.
Scheme 26: The sulfonated nanoscaled diamond powder for the dehydration of D-xylose into furfural.
Scheme 27: The synthetic route and catalytic application of the GR-SO3H.
Beilstein J. Org. Chem. 2018, 14, 2689–2697, doi:10.3762/bjoc.14.246
Graphical Abstract
Scheme 1: Two-step reaction towards triazolochromene 5a and obtained oxidized side product 6.
Scheme 2: Reaction pathways leading to the different regioisomers.
Figure 1: Scope with respect to various salicylaldehydes 1a–f, nitroalkenes 2a–d and organic azides 4a–g. aRe...
Scheme 3: Synthesis of bis-chromenotriazole 5p.
Figure 2: Generality of products obtained via the two-pot mechanochemical procedure, varying the salicylaldeh...
Scheme 4: Scale-up of the one-pot three-component reaction and two-step ball milling procedure.
Scheme 5: Postfunctional transformations of triazolochromenes.
Beilstein J. Org. Chem. 2018, 14, 2572–2579, doi:10.3762/bjoc.14.234
Graphical Abstract
Scheme 1: Synthesis of 2-quinolones 2 through intramolecular Friedel–Crafts hydroarylation of N-aryl propargy...
Scheme 2: Strategy towards 2-quinolones 8 bearing a branched substituent on the nitrogen atom.
Figure 1: Scope of the protocol.
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.