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Search for "multicomponent coupling" in Full Text gives 13 result(s) in Beilstein Journal of Organic Chemistry.
N-tert-Butanesulfinyl imines in the asymmetric synthesis of nitrogen-containing heterocycles
- Joseane A. Mendes,
- Paulo R. R. Costa,
- Miguel Yus,
- Francisco Foubelo and
- Camilla D. Buarque
Beilstein J. Org. Chem. 2021, 17, 1096–1140, doi:10.3762/bjoc.17.86
- addition of HMPA and imine 14 in the multicomponent coupling. When the bulky TBS group was used, and HMPA was added to the reaction mixture before the imine 14, aziridines 36 were formed. The addition of lithium metaloenamine took place through and open transition state to the Re face of the imine (RS)-14
Graphical Abstract
Scheme 1: General strategy for the enantioselective synthesis of N-containing heterocycles from N-tert-butane...
Scheme 2: Methodologies for condensation of aldehydes and ketones with tert-butanesulfinamides (1).
Scheme 3: Transition models for cis-aziridines and trans-aziridines.
Scheme 4: Mechanism for the reduction of N-tert-butanesulfinyl imines.
Scheme 5: Transition models for the addition of organomagnesium and organolithium compounds to N-tert-butanes...
Scheme 6: Synthesis of 2,2-dibromoaziridines 15 from aldimines 14 and bromoform, and proposed non-chelation-c...
Scheme 7: Diastereoselective synthesis of aziridines from tert-butanesulfinyl imines.
Scheme 8: Synthesis of vinylaziridines 22 from aldimines 14 and 1,3-dibromopropene 23, and proposed chelation...
Scheme 9: Synthesis of vinylaziridines 27 from aldimines 14 and α-bromoesters 26, and proposed transition sta...
Scheme 10: Synthesis of 2-chloroaziridines 28 from aldimines 14 and dichloromethane, and proposed transition s...
Scheme 11: Synthesis of cis-vinylaziridines 30 and 31 from aldimines 14 and bromomethylbutenolide 29.
Scheme 12: Synthesis of 2-chloro-2-aroylaziridines 36 and 32 from aldimines 14, arylnitriles 34, and silyldich...
Scheme 13: Synthesis of trifluoromethylaziridines 39 and proposed transition state of the aziridination.
Scheme 14: Synthesis of aziridines 42 and proposed state transition.
Scheme 15: Synthesis of 1-substituted 2-azaspiro[3.3]heptanes, 1-phenyl-2-azaspiro[3.4]octane and 1-phenyl-2-a...
Scheme 16: Synthesis of 1-substituted 2,6-diazaspiro[3.3]heptanes 48 from chiral imines 14 and 1-Boc-azetidine...
Scheme 17: Synthesis of β-lactams 52 from chiral imines 14 and dimethyl malonate (49).
Scheme 18: Synthesis of spiro-β-lactam 57 from chiral (RS)-N-tert-butanesulfinyl isatin ketimine 53 and ethyl ...
Scheme 19: Synthesis of β-lactam 60, a precursor of (−)-batzelladine D (61) and (−)-13-epi-batzelladine D (62)...
Scheme 20: Rhodium-catalyzed asymmetric synthesis of 3-substituted pyrrolidines 66 from chiral imine (RS)-63 a...
Scheme 21: Asymmetric synthesis of 1,3-disubstituted isoindolines 69 and 70 from chiral imine 67.
Scheme 22: Asymmetric synthesis of cis-2,5-disubstituted pyrrolidines 73 from chiral imine (RS)-71.
Scheme 23: Asymmetric synthesis of 3-hydroxy-5-substituted pyrrolidin-2-ones 77 from chiral imine (RS)-74.
Scheme 24: Asymmetric synthesis of 4-hydroxy-5-substituted pyrrolidin-2-ones 80 from chiral imines 79.
Scheme 25: Asymmetric synthesis of 3-pyrrolines 82 from chiral imines 14 and ethyl 4-bromocrotonate (81).
Scheme 26: Asymmetric synthesis of γ-amino esters 84, and tetramic acid derivative 86 from chiral imines (RS)-...
Scheme 27: Asymmetric synthesis of α-methylene-γ-butyrolactams 90 from chiral imines (Z,SS)-87 and ethyl 2-bro...
Scheme 28: Asymmetric synthesis of methylenepyrrolidines 92 from chiral imines (RS)-14 and 2-(trimethysilylmet...
Scheme 29: Synthesis of dibenzoazaspirodecanes from cyclic N-tert-butanesulfinyl imines.
Scheme 30: Stereoselective synthesis of cyclopenta[c]proline derivatives 103 from β,γ-unsaturated α-amino acid...
Scheme 31: Stereoselective synthesis of alkaloids (−)-angustureine (107) and (−)-cuspareine (108).
Scheme 32: Stereoselective synthesis of alkaloids (−)-pelletierine (112) and (+)-coniine (117).
Scheme 33: Synthesis of piperidine alkaloids (+)-dihydropinidine (122a), (+)-isosolenopsin (122b) and (+)-isos...
Scheme 34: Stereoselective synthesis of the alkaloids(+)-sedamine (125) from chiral imine (SS)-119.
Scheme 35: Stereoselective synthesis of trans-5-hydroxy-6-substituted-2-piperidinones 127 and 129 from chiral ...
Scheme 36: Stereoselective synthesis of trans-5-hydroxy-6-substituted ethanone-2-piperidinones 132 from chiral...
Scheme 37: Stereoselective synthesis of trans-3-benzyl-5-hydroxy-6-substituted-2-piperidinones 136 from chiral...
Scheme 38: Stereoselective synthesis of trans-5-hydroxy-6-substituted 2-piperidinones 139 from chiral imine 138...
Scheme 39: Stereoselective synthesis of ʟ-hydroxypipecolic acid 145 from chiral imine 144.
Scheme 40: Synthesis of 1-substituted isoquinolones 147, 149 and 151.
Scheme 41: Stereoselective synthesis of 3-substituted dihydrobenzo[de]isoquinolinones 154.
Scheme 42: Enantioselective synthesis of alkaloids (S)-1-benzyl-6,7-dimethoxy-1,2,3,4-tetrahydroisoquinoline (...
Scheme 43: Enantioselective synthesis of alkaloids (−)-cermizine B (171) and (+)-serratezomine E (172) develop...
Scheme 44: Stereoselective synthesis of (+)-isosolepnosin (177) and (+)-solepnosin (178) from homoallylamine d...
Scheme 45: Stereoselective synthesis of tetrahydroquinoline derivatives 184, 185 and 187 from chiral imines (RS...
Scheme 46: Stereoselective synthesis of pyridobenzofuran and pyridoindole derivatives 193 from homopropargylam...
Scheme 47: Stereoselective synthesis of 2-substituted 1,2,5,6-tetrahydropyridines 196 from chiral imines (RS)-...
Scheme 48: Stereoselective synthesis of 2-substituted trans-2,6-disubstituted piperidine 199 from chiral imine...
Scheme 49: Stereoselective synthesis of cis-2,6-disubstituted piperidines 200, and alkaloid (+)-241D, from chi...
Scheme 50: Stereoselective synthesis of 6-substituted piperidines-2,5-diones 206 and 1,7-diazaspiro[4.5]decane...
Scheme 51: Stereoselective synthesis of spirocyclic oxindoles 210 from chiral imines (RS)-53.
Scheme 52: Stereoselective synthesis of azaspiro compound 213 from chiral imine 211.
Scheme 53: Stereoselective synthesis of tetrahydroisoquinoline derivatives from chiral imines (RS)-214.
Scheme 54: Stereoselective synthesis of (−)-crispine A 223 from chiral imine (RS)-214.
Scheme 55: Synthesis of (−)-harmicine (228) using tert-butanesulfinamide through haloamide cyclization.
Scheme 56: Stereoselective synthesis of tetraponerines T1–T8.
Scheme 57: Stereoselective synthesis of phenanthroindolizidines 246a and (−)-tylophorine (246b), and phenanthr...
Scheme 58: Stereoselective synthesis of indoline, tetrahydroquinoline and tetrahydrobenzazepine derivatives 253...
Scheme 59: Stereoselective synthesis of (+)-epohelmin A (258) and (+)-epohelmin B (260) from aldimine (RS)-79.
Scheme 60: Stereoselective synthesis of (−)-epiquinamide (266) from chiral aldimine (SS)-261.
Scheme 61: Synthesis synthesis of (–)-hippodamine (273) and (+)-epi-hippodamine (272) using chiral sulfinyl am...
Scheme 62: Stereoselective synthesis of (+)-grandisine D (279) and (+)-amabiline (283).
Scheme 63: Stereoselective synthesis of (−)-epiquinamide (266) and (+)-swaisonine (291) from aldimine (SS)-126....
Scheme 64: Stereoselective synthesis of (+)-C(9a)-epi-epiquinamide (294).
Scheme 65: Stereoselective synthesis of (+)-lasubine II (298) from chiral aldimine (SS)-109.
Scheme 66: Stereoselective synthesis of (−)-epimyrtine (300a) and (−)-lasubine II (ent-302) from β-amino keton...
Scheme 67: Stereoselective synthesis of (−)-tabersonine (310), (−)-vincadifformine (311), and (−)-aspidospermi...
Scheme 68: Stereoselective synthesis of (+)-epohelmin A (258) and (+)-epohelmin B (260) from aldehyde 313 and ...
Scheme 69: Total synthesis of (+)-lysergic acid (323) from N-tert-butanesulfinamide (RS)-1.
Combination of multicomponent KA2 and Pauson–Khand reactions: short synthesis of spirocyclic pyrrolocyclopentenones
- Riccardo Innocenti,
- Elena Lenci,
- Gloria Menchi and
- Andrea Trabocchi
Beilstein J. Org. Chem. 2020, 16, 200–211, doi:10.3762/bjoc.16.23
- . Following our interest to DOS as a synthetic strategy for the generation of molecular scaffolds according to a couple/pair approach [45][46][47], we reasoned to combine the copper-catalyzed ketone–amine–alkyne (KA2) multicomponent coupling reaction [48] with the Pauson–Khand cycloaddition as the pairing
- components in the outcome of the multicomponent coupling reaction. Similarly, the use of piperidone as the ketone component proved to work only when the amino group was protected as Boc, whereas the N-methyl derivative did not proceed to the coupling product (Table 1, entries 10 and 9, respectively). Indeed
Graphical Abstract
Figure 1: Chemical structure of representative approved drugs containing a spirocyclic moiety.
Scheme 1: Synthetic strategies for accessing pyrrolocyclopentenone derivatives, including the novel couple/pa...
Scheme 2: Couple/pair approach using combined KA2 and Pauson–Khand multicomponent reactions.
Scheme 3: Follow-up chemistry on compound 5 taking advantage of the enone chemistry. Reaction conditions. (i)...
Figure 2: Top: Selected NOE contacts from NOESY 1D spectra of compound 36; bottom: low energy conformer of 36...
Figure 3: PCA plot resulting from the correlation between PC1 vs PC2, showing the positioning in the chemical...
Figure 4: PMI plot showing the skeletal diversity of compounds 3–39 (blue diamonds) with respect to the refer...
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
- , and multicomponent coupling reactions [92][93]. Review Multicomponent reactions for the synthesis of imidazopyridines One of the major challenges in organic synthesis is the creation of diverse and complex molecules from simple and readily available substrates. MCRs constitute one of the most
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.
Three-component coupling of aryl iodides, allenes, and aldehydes catalyzed by a Co/Cr-hybrid catalyst
- Kimihiro Komeyama,
- Shunsuke Sakiyama,
- Kento Iwashita,
- Itaru Osaka and
- Ken Takaki
Beilstein J. Org. Chem. 2018, 14, 1413–1420, doi:10.3762/bjoc.14.118
- substituted secondary alcohols, as demonstrated in the Nozaki–Hiyama–Kishi (NHK) reaction (Scheme 2) [4][5][6][7][8][9]. Although the catalyst combination allows the use of organic halides as carbon nucleophiles, a multicomponent coupling reaction using a similar catalyst combination has had limited success
Graphical Abstract
Scheme 1: Nucleophilic and π-electrophilic characters of organometallics depending on the central metals.
Scheme 2: Ni/Cr or Co/Cr-catalyzed NHK reaction.
Scheme 3: Functionalization of alkynes via carbocobaltation.
Scheme 4: Cyclization/borylation of alkynyl iodoarenes using the Co/Cr catalyst.
Scheme 5: Three-component coupling of aryl iodides, arenes, and aldehydes using Co/Cr catalyst (this work).
Scheme 6: Screening of aldehydes in the Co/Cr-catalyzed three-component coupling reaction. All yields are det...
Scheme 7: Screening of aryl iodides in the Co/Cr-catalyzed three-component coupling reaction. All yields are ...
Scheme 8: Screening of allenes in the Co/Cr-catalyzed three-component coupling reaction. All yields are deter...
Scheme 9: Reversed diastereoselectivity using allenyl ethers 5 and 6. a4-chlorobenzaldehyde was used instead ...
Scheme 10: Stoichiometric reaction of phenylchromium(II or III) reagents (reaction 1) and the three-component ...
Scheme 11: The origin of the diastereoselectivity in the present three-component coupling.
Scheme 12: Plausible reaction mechanism of the three-component coupling.
Methyl isocyanide as a convertible functional group for the synthesis of spirocyclic oxindole γ-lactams via post-Ugi-4CR/transamidation/cyclization in a one-pot, three-step sequence
- Amarendar Reddy Maddirala and
- Peter R. Andreana
Beilstein J. Org. Chem. 2018, 14, 875–883, doi:10.3762/bjoc.14.74
- carbon centers under basic conditions providing molecular diversity and a small library of spirocyclic oxindoles. Keywords: convertible isocyanides; lactams; molecular diversity; oxindoles; transamidation; Introduction The Ugi-multicomponent coupling reaction [1][2], followed by post-modification
Graphical Abstract
Scheme 1: Previously reported post-Ugi-4CR methods for the synthesis of 2-oxindoles and spirocyclic 2-oxindol...
Scheme 2: Post-Ugi-4CR/transamidation/cyclization sequence.
Scheme 3: Base-promoted intramolecular 5-endo-dig cyclization.
Figure 1: ORTEP diagram of compound 7a.
Figure 2: Readily and synthetically accessible starting materials.
Scheme 4: Reaction scope with varying combinations of substrates.
Scheme 5: Synthesis of 5-chloro-1'-phenylspiro[indoline-3,2'-pyrrolidine]-2,5'-dione (8a).
Figure 3: Small molecule library of spiro[indoline-3,2'-pyrrolidine]-2,5'-dione analogs.
Scheme 6: Method applicability for the one-pot synthesis of 5-HT6 receptor antagonist 8j [53].
A new paradigm for designing ring construction strategies for green organic synthesis: implications for the discovery of multicomponent reactions to build molecules containing a single ring
- John Andraos
Beilstein J. Org. Chem. 2016, 12, 2420–2442, doi:10.3762/bjoc.12.236
- rings. This will lead directly to the total number of possible multicomponent coupling assemblages or fragmentations of a given ring skeleton. The second is the enumeration of those partitions in a systematic manner so that a list of unique combinations for each type of ring partition can be obtained
Graphical Abstract
Figure 1: Possible two-component couplings for various monocyclic rings frequently encountered in organic mol...
Figure 2: Possible three-component couplings for various monocyclic rings frequently encountered in organic m...
Figure 3: Possible four-component couplings for various monocyclic rings frequently encountered in organic mo...
Figure 4: Permutations of two-component coupling patterns for synthesizing the cyclohexanone ring. Synthesis ...
Figure 5: Permutations of two-component coupling patterns for synthesizing the cyclohexanone ring overlayed w...
Scheme 1: Conjectured syntheses of cyclohexanone via [5 + 1] strategies.
Scheme 2: Conjectured syntheses of cyclohexanone via [4 + 2] strategies.
Scheme 3: Conjectured syntheses of cyclohexanone via [3 + 3] strategies.
Figure 6: Permutations of three-component coupling patterns for synthesizing the cyclohexanone ring. Synthesi...
Figure 7: Permutations of three-component coupling patterns for synthesizing the pyrazole ring via [2 + 2 + 1...
Scheme 4: Literature method for constructing the pyrazole ring via the A4 [2 + 2 + 1] strategy.
Scheme 5: Literature methods for constructing the pyrazole ring via the A5 [2 + 2 + 1] strategy.
Scheme 6: Literature methods for constructing the pyrazole ring via the A1 [2 + 2 + 1] strategy.
Scheme 7: Literature methods for constructing the pyrazole ring via the B4 [3 + 1 + 1] strategy.
Figure 8: Intrinsic green performance of documented pyrazole syntheses according to [2 + 2 + 1] and [3 + 1 + ...
Scheme 8: Conjectured reactions for constructing the pyrazole ring via the A2 and A3 [2 + 2 + 1] strategies.
Scheme 9: Conjectured reactions for constructing the pyrazole ring via the B1, B2, B3, and B4 [3 + 1 + 1] str...
Figure 9: Permutations of three-component coupling patterns for synthesizing the Biginelli ring adduct. Synth...
Scheme 10: Reported syntheses of the Biginelli adduct via the traditional [3 + 2 + 1] mapping strategy.
Scheme 11: Reported syntheses of the Biginelli adduct via new [3 + 2 + 1] mapping strategies.
Scheme 12: Reported syntheses of the Biginelli adduct via a new [2 + 2 + 1 + 1] mapping strategy.
Scheme 13: Conjectured syntheses of the Biginelli adduct via new [2 + 2 + 2] mapping strategies.
Scheme 14: Conjectured syntheses of the Biginelli adduct via new [3 + 2 + 1] mapping strategies.
Figure 10: Intrinsic green performance of documented Biginelli adduct syntheses according to [3 + 2 + 1] three...
Figure 11: Intrinsic green performance of newly conjectured Biginelli adduct syntheses according to [4 + 1 + 1...
Application of heterocyclic aldehydes as components in Ugi–Smiles couplings
- Katelynn M. Mason,
- Michael S. Meyers,
- Abbie M. Fox and
- Sarah B. Luesse
Beilstein J. Org. Chem. 2016, 12, 2032–2037, doi:10.3762/bjoc.12.191
- also a competent component for Ugi–Smiles adduct formation. Keywords: Diels–Alder cycloaddition; epoxyisoindoline; multicomponent coupling reaction; tandem reaction; Ugi–Smiles coupling; Introduction Synthetic methods to efficiently prepare libraries of biologically-relevant compounds are in demand
- and have inspired the development of new multicomponent coupling reactions. Isocyanide-based multicomponent couplings [1], led by the foundational Ugi four-component coupling [2][3], have been used extensively for the synthesis of natural products and the preparation of diverse heterocyclic scaffolds
- nitrogen-containing heterocyclic systems [11][12][13]. Multicomponent coupling reactions (MCRs) have been combined with IMDA approaches to efficiently increase molecular complexity [14] and prepare complex molecular scaffolds for the synthesis of natural products [15][16]. While the Ugi–Smiles condensation
Graphical Abstract
Scheme 1: N-Arylepoxyisoindolines via tandem Ugi–Smiles/IMDA reaction.
Scheme 2: Reaction monitoring by 1H NMR for production of 1b.
Scheme 3: Use of a thienyl-substituted aldehyde for Ugi–Smiles couplings.
Synthesis of α-amino amidines through molecular iodine-catalyzed three-component coupling of isocyanides, aldehydes and amines
- Praveen Reddy Adiyala,
- D. Chandrasekhar,
- Jeevak Sopanrao Kapure,
- Chada Narsimha Reddy and
- Ram Awatar Maurya
Beilstein J. Org. Chem. 2014, 10, 2065–2070, doi:10.3762/bjoc.10.214
- methods provide amidines in acceptable yields, they suffer from limitations such as limited structural diversity of the final products. Since multicomponent reactions (MCRs) are expected to provide a rich structural diversity, much attention was paid on the development of multicomponent-coupling
Graphical Abstract
Figure 1: Synthesis of diamides, α-amino amides [13,14] and α-amino amidines [15-19] through Ugi and related MCRs.
Figure 2: Synthesis of imidazolopyridines 7a–d through a three-component coupling reaction of substituted ben...
Figure 3: A plausible reaction mechanism for the iodine-catalyzed α-amino amidine synthesis.
Silver and gold-catalyzed multicomponent reactions
- Giorgio Abbiati and
- Elisabetta Rossi
Beilstein J. Org. Chem. 2014, 10, 481–513, doi:10.3762/bjoc.10.46
- ions, generated from the condensation of amines and aldehydes, represents the most convenient method to access propargylamines [4]. Although numerous examples of the A3-coupling reaction have been reported, there are still many challenges and opportunities for this multicomponent coupling reaction. The
Graphical Abstract
Scheme 1: General reaction mechanism for Ag(I)-catalyzed A3-coupling reactions.
Scheme 2: A3-coupling reaction catalyzed by polystyrene-supported NHC–silver halides.
Figure 1: Various NHC–Ag(I) complexes used as catalysts for A3-coupling.
Scheme 3: Proposed reaction mechanism for NHC–AgCl catalyzed A3-coupling reactions.
Scheme 4: Liu’s synthesis of pyrrole-2-carboxaldehydes 4.
Scheme 5: Proposed reaction mechanism for Liu’s synthesis of pyrrole-2-carboxaldehydes 4.
Scheme 6: Gold-catalyzed synthesis of propargylamines 1.
Scheme 7: A3-coupling catalyzed by phosphinamidic Au(III) metallacycle 6.
Scheme 8: Gold-catalyzed KA2-coupling.
Scheme 9: A3-coupling applied to aldehyde-containing oligosaccharides 8.
Scheme 10: A3-MCR for the preparation of propargylamine-substituted indoles 9.
Scheme 11: A3-coupling interceded synthesis of furans 12.
Scheme 12: A3/KA2-coupling mediated synthesis of functionalized dihydropyrazoles 13 and polycyclic dihydropyra...
Scheme 13: Au(I)-catalyzed entry to cyclic carbamimidates 17 via an A3-coupling-type approach.
Scheme 14: Proposed reaction mechanism for the Au(I)-catalyzed synthesis of cyclic carbamimidates 17.
Figure 2: Chiral trans-1-diphenylphosphino-2-aminocyclohexane–Au(I) complex 20.
Scheme 15: A3-coupling-type synthesis of oxazoles 21 catalyzed by Au(III)–salen complex.
Scheme 16: Proposed reaction mechanism for the synthesis of oxazoles 21.
Scheme 17: Synthesis of propargyl ethyl ethers 24 by an A3-coupling-type reaction.
Scheme 18: General mechanism of Ag(I)-catalyzed MCRs of 2-alkynylbenzaldehydes, amines and nucleophiles.
Scheme 19: General synthetic pathway to 1,3-disubstituted-1,2-dihydroisoquinolines.
Scheme 20: Synthesis of 1,3-disubstituted-1,2-dihydroisoquinolines 29.
Scheme 21: Synthesis of 1,3-disubstituted-1,2-dihydroisoquinolines 35 and 36.
Scheme 22: Rh(II)/Ag(I) co-catalyzed synthesis of 1,3-disubstituted-1,2-dihydroisoquinolines 40.
Scheme 23: General synthetic pathway to 2-amino-1,2-dihydroquinolines.
Scheme 24: Synthesis of 2-amino-1,2-dihydroquinolines 47.
Scheme 25: Synthesis of tricyclic H-pyrazolo[5,1-a]isoquinoline 48.
Scheme 26: Synthesis of tricyclic H-pyrazolo[5,1-a]isoquinolines 48.
Scheme 27: Cu(II)/Ag(I) catalyzed synthesis of H-pyrazolo[5,1-a]isoquinolines 48.
Scheme 28: Synthesis of 2-aminopyrazolo[5,1-a]isoquinolines 53.
Scheme 29: Synthesis of 1-(isoquinolin-1-yl)guanidines 55.
Scheme 30: Ag(I)/Cu(I) catalyzed synthesis of 2-amino-H-pyrazolo[5,1-a]isoquinolines 58.
Scheme 31: Ag(I)/Ni(II) co-catalyzed synthesis of 3,4-dihydro-1H-pyridazino[6,1-a]isoquinoline-1,1-dicarboxyla...
Scheme 32: Ag(I) promoted activation of the α-carbon atom of the isocyanide group.
Scheme 33: Synthesis of dihydroimidazoles 65.
Scheme 34: Synthesis of oxazoles 68.
Scheme 35: Stereoselective synthesis of chiral butenolides 71.
Scheme 36: Proposed reaction mechanism for the synthesis of butenolides 71.
Scheme 37: Stereoselective three-component approach to pirrolidines 77 by means of a chiral auxiliary.
Scheme 38: Stereoselective three-component approach to pyrrolidines 81 and 82 by means of a chiral catalyst.
Scheme 39: Synthesis of substituted five-membered carbocyles 86.
Scheme 40: Synthesis of regioisomeric arylnaphthalene lactones.
Scheme 41: Enantioselective synthesis of spiroacetals 96 by Fañanás and Rodríguez [105].
Scheme 42: Enantioselective synthesis of spiroacetals 101 by Gong [106].
Scheme 43: Synthesis of polyfunctionalized fused bicyclic ketals 103 and bridged tricyclic ketals 104.
Scheme 44: Proposed reaction mechanism for the synthesis of ketals 103 and 104.
Scheme 45: Synthesis of β-alkoxyketones 108.
Scheme 46: Synthesis of N-methyl-1,4-dihydropyridines 112.
Scheme 47: Synthesis of tetrahydrocarbazoles 115–117.
Scheme 48: Plausible reaction mechanism for the synthesis of tetrahydrocarbazoles 115–117.
Scheme 49: Carboamination, carboalkoxylation and carbolactonization of terminal alkenes.
Scheme 50: Oxyarylation of alkenes with arylboronic acids and Selectfluor as reoxidant.
Scheme 51: Proposed reaction mechanism for oxyarylation of alkenes.
Scheme 52: Oxyarylation of alkenes with arylsilanes and Selectfluor as reoxidant.
Scheme 53: Oxyarylation of alkenes with arylsilanes and IBA as reoxidant.
An overview of the synthetic routes to the best selling drugs containing 6-membered heterocycles
- Marcus Baumann and
- Ian R. Baxendale
Beilstein J. Org. Chem. 2013, 9, 2265–2319, doi:10.3762/bjoc.9.265
Graphical Abstract
Scheme 1: Scaled industrial processes for the synthesis of simple pyridines.
Scheme 2: Synthesis of nicotinic acid from 2-methyl-5-ethylpyridine (1.11).
Scheme 3: Synthesis of 3-picoline and nicotinic acid.
Scheme 4: Synthesis of 3-picoline from 2-methylglutarodinitrile 1.19.
Scheme 5: Picoline-based synthesis of clarinex (no yields reported).
Scheme 6: Mode of action of proton-pump inhibitors and structures of the API’s.
Scheme 7: Hantzsch-like route towards the pyridine rings in common proton pump inhibitors.
Figure 1: Structures of rosiglitazone (1.40) and pioglitazone (1.41).
Scheme 8: Synthesis of rosiglitazone.
Scheme 9: Syntheses of 2-pyridones.
Scheme 10: Synthesis and mechanism of 2-pyrone from malic acid.
Scheme 11: Polymer-assisted synthesis of rosiglitazone.
Scheme 12: Synthesis of pioglitazone.
Scheme 13: Meerwein arylation reaction towards pioglitazone.
Scheme 14: Route towards pioglitazone utilising tyrosine.
Scheme 15: Route towards pioglitazone via Darzens ester formation.
Scheme 16: Syntheses of the thiazolidinedione moiety.
Scheme 17: Synthesis of etoricoxib utilising Negishi and Stille cross-coupling reactions.
Scheme 18: Synthesis of etoricoxib via vinamidinium condensation.
Figure 2: Structures of nalidixic acid, levofloxacin and moxifloxacin.
Scheme 19: Synthesis of moxifloxacin.
Scheme 20: Synthesis of (S,S)-2,8-diazabicyclo[4.3.0]nonane 1.105.
Scheme 21: Synthesis of levofloxacin.
Scheme 22: Alternative approach to the levofloxacin core 1.125.
Figure 3: Structures of nifedipine, amlodipine and clevidipine.
Scheme 23: Mg3N2-mediated synthesis of nifedipine.
Scheme 24: Synthesis of rac-amlodipine as besylate salt.
Scheme 25: Aza Diels–Alder approach towards amlodipine.
Scheme 26: Routes towards clevidipine.
Figure 4: Examples of piperidine containing drugs.
Figure 5: Discovery of tiagabine based on early leads.
Scheme 27: Synthetic sequences to tiagabine.
Figure 6: Structures of solifenacin (2.57) and muscarine (2.58).
Scheme 28: Enantioselective synthesis of solifenacin.
Figure 7: Structures of DPP-4 inhibitors of the gliptin-type.
Scheme 29: Formation of inactive diketopiperazines from cis-rotameric precursors.
Figure 8: Co-crystal structure of carmegliptin bound in the human DPP-4 active site (PDB 3kwf).
Scheme 30: Improved route to carmegliptin.
Figure 9: Structures of lamivudine and zidovudine.
Scheme 31: Typical routes accessing uracil, thymine and cytosine.
Scheme 32: Coupling between pyrimidones and riboses via the Vorbrüggen nucleosidation.
Scheme 33: Synthesis of lamivudine.
Scheme 34: Synthesis of raltegravir.
Scheme 35: Mechanistic studies on the formation of 3.22.
Figure 10: Structures of selected pyrimidine containing drugs.
Scheme 36: General preparation of pyrimidines and dihydropyrimidones.
Scheme 37: Synthesis of imatinib.
Scheme 38: Flow synthesis of imatinib.
Scheme 39: Syntheses of erlotinib.
Scheme 40: Synthesis of erlotinib proceeding via Dimroth rearrangement.
Scheme 41: Synthesis of lapatinib.
Scheme 42: Synthesis of rosuvastatin.
Scheme 43: Alternative preparation of the key aldehyde towards rosuvastatin.
Figure 11: Structure comparison between nicotinic acetylcholine receptor agonists.
Scheme 44: Syntheses of varenicline and its key building block 4.5.
Scheme 45: Synthetic access to eszopiclone and brimonidine via quinoxaline intermediates.
Figure 12: Bortezomib bound in an active site of the yeast 20S proteasome ([114], pdb 2F16).
Scheme 46: Asymmetric synthesis of bortezomib.
Figure 13: Structures of some prominent piperazine containing drugs.
Figure 14: Structural comparison between the core of aplaviroc (4.35) and a type-1 β-turn (4.36).
Scheme 47: Examplary synthesis of an aplaviroc analogue via the Ugi-MCR.
Scheme 48: Syntheses of azelastine (5.1).
Figure 15: Structures of captopril, enalapril and cilazapril.
Scheme 49: Synthesis of cilazapril.
Figure 16: Structures of lamotrigine, ceftriaxone and azapropazone.
Scheme 50: Synthesis of lamotrigine.
Scheme 51: Alternative synthesis of lamotrigine (no yields reported).
Figure 17: Structural comparison between imiquimod and the related adenosine nucleoside.
Scheme 52: Conventional synthesis of imiquimod (no yields reported).
Scheme 53: Synthesis of imiquimod.
Scheme 54: Synthesis of imiquimod via tetrazole formation (not all yields reported).
Figure 18: Structures of various anti HIV-medications.
Scheme 55: Synthesis of abacavir.
Figure 19: Structures of diazepam compared to modern replacements.
Scheme 56: Synthesis of ocinaplon.
Scheme 57: Access to zaleplon and indiplon.
Scheme 58: Different routes towards the required N-methylpyrazole 6.65 of sildenafil.
Scheme 59: Polymer-supported reagents in the synthesis of key aminopyrazole 6.72.
Scheme 60: Early synthetic route to sildenafil.
Scheme 61: Convergent preparations of sildenafil.
Figure 20: Comparison of the structures of sildenafil, tadalafil and vardenafil.
Scheme 62: Short route to imidazotriazinones.
Scheme 63: Alternative route towards vardenafils core imidazotriazinone (6.95).
Scheme 64: Bayer’s approach to the vardenafil core.
Scheme 65: Large scale synthesis of vardenafil.
Scheme 66: Mode of action of temozolomide (6.105) as methylating agent.
Scheme 67: Different routes to temozolomide.
Scheme 68: Safer route towards temozolomide.
Figure 21: Some unreported heterocyclic scaffolds in top market drugs.
Alternaric acid: formal synthesis and related studies
- Michael C. Slade and
- Jeffrey S. Johnson
Beilstein J. Org. Chem. 2013, 9, 166–172, doi:10.3762/bjoc.9.19
- complex molecule synthesis. Keywords: formal synthesis; multicomponent coupling; natural products; silyl glyoxylates; Introduction The rapid development of molecular complexity from simple starting materials is an important goal in modern synthetic organic chemistry. In this context, streamlined one-pot
Graphical Abstract
Scheme 1: (A) Silyl glyoxylates as versatile reagents for three-component coupling reactions: representative ...
Scheme 2: Potential applications of silyl glyoxylate couplings and precedent synthetic intermediates toward t...
Scheme 3: Three-component coupling with a vinyl nucleophile and elaboration to Ichihara’s aldehyde.
Scheme 4: Modified Julia olefination as a step-efficient alternative endgame strategy.
Scheme 5: Three-component coupling with an allyl nucleophile and demonstration of successful ruthenium-cataly...
Scheme 6: Approaches considered to address the stereochemical issue.
Scheme 7: Use of a dithiane moiety to excert stereochemical control in the three-component coupling reaction ...
Scheme 8: Synthesis of a vinyl iodide for nucleophile generation and its use in a three-component coupling re...
Asymmetric synthesis of quaternary aryl amino acid derivatives via a three-component aryne coupling reaction
- Elizabeth P. Jones,
- Peter Jones,
- Andrew J. P. White and
- Anthony G. M. Barrett
Beilstein J. Org. Chem. 2011, 7, 1570–1576, doi:10.3762/bjoc.7.185
- ][4][5][6]. We are particularly interested in the use of arynes in multicomponent coupling reactions, in which the resultant aryl carbanion following nucleophilic attack is allowed to react with a further electrophile, providing ortho-disubstituted, functionalized aromatic products in a one-pot
Graphical Abstract
Scheme 1: 3-Component coupling reactions of arynes. E+ = electrophile.
Scheme 2: Aryne mediated α-arylation of amino acids. DMG = directed metallation group. BHT = 2,6-di-tert-buty...
Scheme 3: Proposed mechanism of α-arylation.
Scheme 4: Proposed extension of the methodology to synthesize quaternary adducts.
Scheme 5: Formation of α-methyl, α-aryl Schöllkopf adduct.
Figure 1: NOESY correlation observed for 6a.
Figure 2: X-ray crystal structure of 6b.
Figure 3: Transition state analysis to explain the lack of diastereoselectivity at C-2.
Scheme 6: Formation of quaternary adducts.
Scheme 7: Hydrolysis of quaternary adducts.
Scheme 8: Hydrolysis to amino acids.
Scheme 9: Hydrolysis of analogue 6j.
Scheme 10: Epimerization at C-3 of 6g.
PEG-embedded KBr3: A recyclable catalyst for multicomponent coupling reaction for the efficient synthesis of functionalized piperidines
- Sanny Verma,
- Suman L. Jain and
- Bir Sain
Beilstein J. Org. Chem. 2011, 7, 1334–1341, doi:10.3762/bjoc.7.157
- . Keywords: heterocycles; metal free synthesis; multicomponent coupling; piperidine; recyclable catalyst; Introduction Multicomponent reactions [1][2][3][4][5], involving the one-pot reaction of three or more components to produce valuable compounds, have been recognized as one of the important tools to
Graphical Abstract
Scheme 1: Synthesis of [K+PEG]Br3−.
Scheme 2: Synthesis of functionalized piperidines.
Figure 1: X-ray structure showing the anti orientation of the phenyl rings at C2 and C6.
Scheme 3: A plausible mechanism for the formation of piperidines.
