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Search for "oxygen heterocycles" in Full Text gives 11 result(s) in Beilstein Journal of Organic Chemistry.
Domino reactions of chromones with activated carbonyl compounds
- Peter Langer
Beilstein J. Org. Chem. 2024, 20, 1256–1269, doi:10.3762/bjoc.20.108
- phosphoranes were less studied in my group. Chromones are oxygen heterocycles which are of pharmacological interest and represent versatile synthetic building blocks which can undergo various types of domino reactions [24][25][26][27][28]. In 2001, Nehad N. R. Saleh in my group developed a new synthesis of
Graphical Abstract
Scheme 1: Structures of carbonyl compounds 1, 2, 3, and 4, dianion 7, phosphorane 8 and synthesis of 1,3-bis(...
Scheme 2: Structures of chromones with different substituents located at carbon C-3 and atom numbering scheme...
Scheme 3: Synthesis of 17. Conditions: i, DBU (1.3 equiv), THF, 20 °C, 12 h.
Scheme 4: Synthesis of 18a–ac. Conditions: i, 1) 9a–j, Me3SiOTf (1.3 equiv), 20 °C, 1 h; 2) 6a–h (1.3 equiv),...
Scheme 5: Synthesis of 19a–d. Conditions: i, DBU (1.3 equiv), THF, 20 °C, 12 h.
Scheme 6: Synthesis of 20a–ag. Conditions: i, 1) 10a–i, Me3SiOTf (0.3 equiv), 20 °C, 10 min; 2) 6a–h (1.3 equ...
Scheme 7: Synthesis of 21a–g. Conditions: i, DBU (1.3 equiv), dioxane, 20 °C, 12 h.
Scheme 8: Synthesis of 22a,b. Conditions: i, DBU (1.3 equiv), dioxane, 20 °C, 12 h.
Scheme 9: Synthesis of 23a–j. Conditions: i, 1) 11a–c, Me3SiOTf (0.3 equiv), 20 °C, 1 h; 2) 6a–h (1.3 equiv),...
Scheme 10: Synthesis of 24a–w. Conditions: i, 1) 13a–c, Me3SiOTf (0.3 equiv), 20 °C, 1 h; 2) 6a–r (1.3 equiv),...
Scheme 11: Synthesis of 25a–f. Conditions: i, DBU (1.3 equiv), dioxane, 20 °C, 12 h.
Scheme 12: Synthesis of 26a–e. Conditions: i, DBU (1.3 equiv), dioxane, 20 °C, 12 h.
Scheme 13: Synthesis of 27a–c. Conditions: i, DBU (1.3 equiv), dioxane, 20 °C, 12 h.
Scheme 14: Synthesis of 28a–c. Conditions: i, DBU (1.3 equiv), dioxane, 20 °C, 12 h.
Scheme 15: Synthesis of 29a–n and 30. Conditions: i, DBU (1.3 equiv), dioxane, 20 °C, 12 h; ii, 1) KOH, MeOH; ...
Scheme 16: Synthesis of 32a,b. Conditions: i, 1) 31, Me3SiOTf (2.0 equiv), 20 °C, 1 h; 2) 6a,b (3.0 equiv), CH2...
Scheme 17: Synthesis of 33. Conditions: i, DBU (1.3 equiv), THF, 20 °C, 12 h.
Scheme 18: Synthesis of 35a–x. Conditions: i, DBU (1.3 equiv), 1,4-dioxane, 20 °C, 12 h.
Scheme 19: Synthesis of 36a–f. Conditions: i, 1) DBU (1.3 equiv), 1,4-dioxane, 20 °C, 12 h; 2) I2 (2 equiv), D...
Scheme 20: Synthesis of 37a,b. Conditions: i, 1) DBU (1.3 equiv), 1,4-dioxane, 20 °C, 12 h; 2) I2 (2 equiv), D...
Scheme 21: Synthesis of 39a–i. Conditions: i, method A: DBU (1.3 equiv), 1,4-dioxane, 20 °C; method B: K2CO3 (...
Scheme 22: Synthesis of 40. Conditions: i, piperidine, MeOH, CHCl3, reflux, 3 h.
Scheme 23: Synthesis of 41a–am. Conditions: i, Me3SiOTf, CH2Cl2, 20 °C, 12 h, then: HCl (10%); ii, NEt3, EtOH ...
Scheme 24: Synthesis of 43a–aa and 44a–ac. Conditions: i, Me3SiOTf, CH2Cl2, 20 °C, 12 h, then: HCl (10%); ii, ...
Prins cyclization-mediated stereoselective synthesis of tetrahydropyrans and dihydropyrans: an inspection of twenty years
- Asha Budakoti,
- Pradip Kumar Mondal,
- Prachi Verma and
- Jagadish Khamrai
Beilstein J. Org. Chem. 2021, 17, 932–963, doi:10.3762/bjoc.17.77
- ; Prins cyclization; stereoselective; tetrahydropyran; Introduction 6-Membered saturated oxygen heterocycles, known as tetrahydropyran (THP), are recognized as privileged scaffolds, present in a variety of biologically important natural products, such as polyether antibiotics, marine toxins, pheromones
Graphical Abstract
Scheme 1: General strategy for the synthesis of THPs.
Scheme 2: Developments towards the Prins cyclization.
Scheme 3: General stereochemical outcome of the Prins cyclization.
Scheme 4: Regioselectivity in the Prins cyclization.
Scheme 5: Mechanism of the oxonia-Cope reaction in the Prins cyclization.
Scheme 6: Cyclization of electron-deficient enantioenriched alcohol 27.
Scheme 7: Partial racemization through 2-oxonia-Cope allyl transfer.
Scheme 8: Partial racemization by reversible 2-oxonia-Cope rearrangement.
Scheme 9: Rychnovsky modification of the Prins cyclization.
Scheme 10: Synthesis of (−)-centrolobine and the C22–C26 unit of phorboxazole A.
Scheme 11: Axially selective Prins cyclization by Rychnovsky et al.
Scheme 12: Mechanism for the axially selectivity Prins cyclization.
Scheme 13: Mukaiyama aldol–Prins cyclization reaction.
Scheme 14: Application of the aldol–Prins reaction.
Scheme 15: Hart and Bennet's acid-promoted Prins cyclization.
Scheme 16: Tetrahydropyran core of polycarvernoside A as well as (−)-clavoslide A and D.
Scheme 17: Scheidt and co-workers’ route to tetrahydropyran-4-one.
Scheme 18: Mechanism for the Lewis acid-catalyzed synthesis of tetrahydropyran-4-one.
Scheme 19: Hoveyda and co-workers’ strategy for 2,6-disubstituted 4-methylenetetrahydropyran.
Scheme 20: Funk and Cossey’s ene-carbamates strategy.
Scheme 21: Yadav and Kumar’s cyclopropane strategy for THP synthesis.
Scheme 22: 2-Arylcylopropylmethanolin in centrolobine synthesis.
Scheme 23: Yadav and co-workers’ strategy for the synthesis of THP.
Scheme 24: Yadav and co-workers’ Prins–Ritter reaction sequence for 4-amidotetrahydropyran.
Scheme 25: Yadav and co-workers’ strategy to prelactones B, C, and V.
Scheme 26: Yadav and co-workers’ strategy for the synthesis of (±)-centrolobine.
Scheme 27: Loh and co-workers’ strategy for the synthesis of zampanolide and dactylolide.
Scheme 28: Loh and Chan’s strategy for THP synthesis.
Scheme 29: Prins cyclization of cyclohexanecarboxaldehyde.
Scheme 30: Prins cyclization of methyl ricinoleate (127) and benzaldehyde (88).
Scheme 31: AlCl3-catalyzed cyclization of homoallylic alcohol 129 and aldehyde 130.
Scheme 32: Martín and co-workers’ stereoselective approach for the synthesis of highly substituted tetrahydrop...
Scheme 33: Ene-IMSC strategy by Marko and Leroy for the synthesis of tetrahydropyran.
Scheme 34: Marko and Leroy’s strategy for the synthesis of tetrahydropyrans 146.
Scheme 35: Sakurai dimerization/macrolactonization reaction for the synthesis of cyanolide A.
Scheme 36: Hoye and Hu’s synthesis of (−)-dactyloide by intramolecular Sakurai cyclization.
Scheme 37: Minehan and co-workers’ strategy for the synthesis of THPs 157.
Scheme 38: Yu and co-workers’ allylic transfer strategy for the construction of tetrahydropyran 161.
Scheme 39: Reactivity enhancement in intramolecular Prins cyclization.
Scheme 40: Floreancig and co-workers’ Prins cyclization strategy to (+)-dactyloide.
Scheme 41: Panek and Huang’s DHP synthesis from crotylsilanes: a general strategy.
Scheme 42: Panek and Huang’s DHP synthesis from syn-crotylsilanes.
Scheme 43: Panek and Huang’s DHP synthesis from anti-crotylsilanes.
Scheme 44: Roush and co-workers’ [4 + 2]-annulation strategy for DHP synthesis [82].
Scheme 45: TMSOTf-promoted annulation reaction.
Scheme 46: Dobb and co-workers’ synthesis of DHP.
Scheme 47: BiBr3-promoted tandem silyl-Prins reaction by Hinkle et al.
Scheme 48: Substrate scope of Hinkle and co-workers’ strategy.
Scheme 49: Cho and co-workers’ strategy for 2,6 disubstituted 3,4-dimethylene-THP.
Scheme 50: Furman and co-workers’ THP synthesis from propargylsilane.
Scheme 51: THP synthesis from silyl enol ethers.
Scheme 52: Rychnovsky and co-workers’ strategy for THP synthesis from hydroxy-substituted silyl enol ethers.
Scheme 53: Li and co-workers’ germinal bissilyl Prins cyclization strategy to (−)-exiguolide.
Scheme 54: Xu and co-workers’ hydroiodination strategy for THP.
Scheme 55: Wang and co-workers’ strategy for tetrahydropyran synthesis.
Scheme 56: FeCl3-catalyzed synthesis of DHP from alkynylsilane alcohol.
Scheme 57: Martín, Padrón, and co-workers’ proposed mechanism of alkynylsilane Prins cyclization for the synth...
Scheme 58: Marko and co-workers’ synthesis of 2,6-anti-configured tetrahydropyran.
Scheme 59: Loh and co-workers’ strategy for 2,6-syn-tetrahydropyrans.
Scheme 60: Loh and co-workers’ strategy for anti-THP synthesis.
Scheme 61: Cha and co-workers’ strategy for trans-2,6-tetrahydropyran.
Scheme 62: Mechanism proposed by Cha et al.
Scheme 63: TiCl4-mediated cyclization to trans-THP.
Scheme 64: Feng and co-workers’ FeCl3-catalyzed Prins cyclization strategy to 4-hydroxy-substituted THP.
Scheme 65: Selectivity profile of the Prins cyclization under participation of an iron ligand.
Scheme 66: Sequential reactions involving Prins cyclization.
Scheme 67: Banerjee and co-workers’ strategy of Prins cyclization from cyclopropane carbaldehydes and propargy...
Scheme 68: Mullen and Gagné's (R)-[(tolBINAP)Pt(NC6F5)2][SbF6]2-catalyzed asymmetric Prins cyclization strateg...
Scheme 69: Yu and co-workers’ DDQ-catalyzed asymmetric Prins cyclization strategy to trisubstituted THPs.
Scheme 70: Lalli and Weghe’s chiral-Brønsted-acid- and achiral-Lewis-acid-promoted asymmetric Prins cyclizatio...
Scheme 71: List and co-workers’ iIDP Brønsted acid-promoted asymmetric Prins cyclization strategy.
Scheme 72: Zhou and co-workers’ strategy for chiral phosphoric acid (CPA)-catalyzed cascade Prins cyclization.
Scheme 73: List and co-workers’ approach for asymmetric Prins cyclization using chiral imidodiphosphoric acid ...
Recent applications of porphyrins as photocatalysts in organic synthesis: batch and continuous flow approaches
- Rodrigo Costa e Silva,
- Luely Oliveira da Silva,
- Aloisio de Andrade Bartolomeu,
- Timothy John Brocksom and
- Kleber Thiago de Oliveira
Beilstein J. Org. Chem. 2020, 16, 917–955, doi:10.3762/bjoc.16.83
- involves energy transfer to surrounding molecules, such as molecular oxygen, heterocycles and other relevant molecules [15][16][17]. The excited states of porphyrins are also both potent oxidants and reductants when compared to the ground state. This phenomenon can be measured by the comparison of the
Graphical Abstract
Figure 1: Chemical structures of the porphyrinoids and their absorption spectra: in bold are highlighted the ...
Figure 2: Photophysical and photochemical processes (Por = porphyrin). Adapted from [12,18].
Figure 3: Main dual photocatalysts and their oxidative/reductive excited state potentials, including porphyri...
Scheme 1: Photoredox alkylation of aldehydes with diazo acetates using porphyrins and a Ru complex. aUsing a ...
Scheme 2: Proposed mechanism for the alkylation of aldehydes with diazo acetates in the presence of TPP.
Scheme 3: Arylation of heteroarenes with aryldiazonium salts using TPFPP as photocatalyst, and corresponding ...
Scheme 4: A) Scope with different aryldiazonium salts and enol acetates. B) Photocatalytic cycles and compari...
Scheme 5: Photoarylation of isopropenyl acetate A) Comparison between batch and continuous-flow approaches an...
Scheme 6: Dehalogenation induced by red light using thiaporphyrin (STPP).
Scheme 7: Applications of NiTPP as both photoreductant and photooxidant.
Scheme 8: Proposed mechanism for obtaining tetrahydroquinolines by reductive quenching.
Scheme 9: Selenylation and thiolation of anilines.
Scheme 10: NiTPP as photoredox catalyst in oxidative and reductive quenching, in comparison with other photoca...
Scheme 11: C–O bond cleavage of 1-phenylethanol using a cobalt porphyrin (CoTMPP) under visible light.
Scheme 12: Hydration of terminal alkynes by RhIII(TSPP) under visible light irradiation.
Scheme 13: Regioselective photocatalytic hydro-defluorination of perfluoroarenes by RhIII(TSPP).
Scheme 14: Formation of 2-methyl-2,3-dihydrobenzofuran by intramolecular hydro-functionalization of allylpheno...
Scheme 15: Photocatalytic oxidative hydroxylation of arylboronic acids using UNLPF-12 as heterogeneous photoca...
Scheme 16: Photocatalytic oxidative hydroxylation of arylboronic acids using MOF-525 as heterogeneous photocat...
Scheme 17: Preparation of the heterogeneous photocatalyst CNH.
Scheme 18: Photoinduced sulfonation of alkenes with sulfinic acid using CNH as photocatalyst.
Scheme 19: Sulfonic acid scope of the sulfonation reactions.
Scheme 20: Regioselective sulfonation reaction of arimistane.
Scheme 21: Synthesis of quinazolin-4-(3H)-ones.
Scheme 22: Selective photooxidation of aromatic benzyl alcohols to benzaldehydes using Pt/PCN-224(Zn).
Scheme 23: Photooxidation of benzaldehydes to benzoic acids using Pt or Pd porphyrins.
Scheme 24: Photocatalytic reduction of various nitroaromatics using a Ni-MOF.
Scheme 25: Photoinduced cycloadditions of CO2 with epoxides by MOF1.
Figure 4: Electronic configurations of the species of oxygen. Adapted from [66].
Scheme 26: TPP-photocatalyzed generation of 1O2 and its application in organic synthesis. Adapted from [67-69].
Scheme 27: Pericyclic reactions involving singlet oxygen and their mechanisms. Adapted from [67].
Scheme 28: First scaled up ascaridole preparation from α-terpinene.
Scheme 29: Antimalarial drug synthesis using an endoperoxidation approach.
Scheme 30: Photooxygenation of colchicine.
Scheme 31: Synthesis of (−)-pinocarvone from abundant (+)-α-pinene.
Scheme 32: Seeberger’s semi-synthesis of artemisinin.
Scheme 33: Synthesis of artemisinin using TPP and supercritical CO2.
Scheme 34: Synthesis of artemisinin using chlorophyll a.
Scheme 35: Quercitol stereoisomer preparation.
Scheme 36: Photocatalyzed preparation of naphthoquinones.
Scheme 37: Continuous endoperoxidation of conjugated dienes and subsequent rearrangements leading to oxidized ...
Scheme 38: The Opatz group total synthesis of (–)-oxycodone.
Scheme 39: Biomimetic syntheses of rhodonoids A, B, E, and F.
Scheme 40: α-Photooxygenation of chiral aldehydes.
Scheme 41: Asymmetric photooxidation of indanone β-keto esters by singlet oxygen using PTC as a chiral inducer...
Scheme 42: Asymmetric photooxidation of both β-keto esters and β-keto amides by singlet oxygen using PTC-2 as ...
Scheme 43: Bifunctional photo-organocatalyst used for the asymmetric oxidation of β-keto esters and β-keto ami...
Scheme 44: Mechanism of singlet oxygen oxidation of sulfides to sulfoxides.
Scheme 45: Controlled oxidation of sulfides to sulfoxides using protonated porphyrins as photocatalysts. aIsol...
Scheme 46: Photochemical oxidation of sulfides to sulfoxides using PdTPFPP as photocatalyst.
Scheme 47: Controlled oxidation of sulfides to sulfoxides using SnPor@PAF as a photosensitizer.
Scheme 48: Syntheses of 2D-PdPor-COF and 3D-Pd-COF.
Scheme 49: Photocatalytic oxidation of A) thioanisole to methyl phenyl sulfoxide and B) various aryl sulfides,...
Scheme 50: General mechanism for oxidation of amines to imines.
Scheme 51: Oxidation of secondary amines to imines.
Scheme 52: Oxidation of secondary amines using Pd-TPFPP as photocatalyst.
Scheme 53: Oxidative amine coupling using UNLPF-12 as heterogeneous photocatalyst.
Scheme 54: Synthesis of Por-COF-1 and Por-COF-2.
Scheme 55: Photocatalytic oxidation of amines to imines by Por-COF-2.
Scheme 56: Photocyanation of primary amines.
Scheme 57: Synthesis of ᴅ,ʟ-tert-leucine hydrochloride.
Scheme 58: Photocyanation of catharanthine and 16-O-acetylvindoline using TPP.
Scheme 59: Photochemical α-functionalization of N-aryltetrahydroisoquinolines using Pd-TPFPP as photocatalyst.
Scheme 60: Ugi-type reaction with 1,2,3,4-tetrahydroisoquinoline using molecular oxygen and TPP.
Scheme 61: Ugi-type reaction with dibenzylamines using molecular oxygen and TPP.
Scheme 62: Mannich-type reaction of tertiary amines using PdTPFPP as photocatalyst.
Scheme 63: Oxidative Mannich reaction using UNLPF-12 as heterogeneous photocatalyst.
Scheme 64: Transformation of amines to α-cyanoepoxides and the proposed mechanism.
Regiodivergent condensation of 5-alkoxycarbonyl-1H-pyrrol-2,3-diones with cyclic ketazinones en route to spirocyclic scaffolds
- Alexey Yu. Dubovtsev,
- Maksim V. Dmitriev,
- Аndrey N. Maslivets and
- Michael Rubin
Beilstein J. Org. Chem. 2017, 13, 2179–2185, doi:10.3762/bjoc.13.218
- between two alternative directions affording derivatives of partially hydrogenated indole or benzofurane. The control of this regioselectivity is efficiently governed by steric effects at the hydrazone moiety of the ketazinone reagent. Keywords: nitrogen heterocycles; oxygen heterocycles; pyrrolediones
Graphical Abstract
Scheme 1: Spirocyclization of enamines with 5-methoxycarbonyl-1H-pyrrolediones.
Scheme 2: Non-catalyzed spirocyclization of enoles (vinylogous carbonates and carbamates) with 5-methoxycarbo...
Scheme 3: Acid-catalyzed spirocyclization of enoles (vinylogous carboxylates) with 5-alkoxycarbonyl-1H-pyrrol...
Figure 1: ORTEP drawing of compound 12ab (CCDC 1546062) showing 50% probability amplitude displacement ellips...
Scheme 4: Formation of mono-imines and mono-hydrazones of 1,3-cyclohexanediones and tautomeric equilibrium be...
Scheme 5: Spirocyclizations involving non-bulky ketazinones 17 and 5-alkoxycarbonyl-1H-pyrrolediones 9.
Figure 2: ORTEP drawing of compound 21ab (CCDC 1546063) showing 50% probability amplitude displacement ellips...
Figure 3: ORTEP drawing of compound 22a (CCDC 1546065) showing 50% probability amplitude displacement ellipso...
Scheme 6: Spirocyclizations involving bulky ketazinones 22 and 5-alkoxycarbonyl-1H-pyrrolediones 9.
Figure 4: ORTEP drawing of compound 23aa (CCDC 1546064) showing 50% probability amplitude displacement ellips...
Biosynthesis of oxygen and nitrogen-containing heterocycles in polyketides
- Franziska Hemmerling and
- Frank Hahn
Beilstein J. Org. Chem. 2016, 12, 1512–1550, doi:10.3762/bjoc.12.148
- [4]. Oxygen heterocycles are mainly found in carbohydrates, polyketides, peptides and terpenoids. Nitrogen heterocycles are part of peptides and alkaloids. Both can of course also occur in the respective hybrid natural products. Sulphur-containing heterocycles are present in few polyketides and more
- (f in Scheme 2). The oxidative cyclisation after C–H activation of alkyl carbons is known for the formation of furan rings 21 (g in Scheme 2). 1.1 Pyrans 1.1.1 oxa-Michael addition: The oxa-Michael addition on an α,β-unsaturated thioester intermediate leads to oxygen heterocycles along with the
- chapter, we will focus on two examples in which one pyran ring is formed. Both characteristically deviate from the typical polyether-specific interplay between one epoxidase and one or a few epoxide hydrolases that collaboratively set up multiple oxygen heterocycles. Pseudomonic acid A. Mupirocin is a
Graphical Abstract
Scheme 1: Schematic description of the cyclisation reaction catalysed by TE domains. In most cases, the nucle...
Scheme 2: Mechanisms for the formation of oxygen heterocycles. The degree of substitution can differ from tha...
Scheme 3: Pyran-ring formation in pederin (24) biosynthesis. Incubation of recombinant PedPS7 with substrate ...
Scheme 4: The domain AmbDH3 from ambruticin biosynthesis catalyses the dehydration of 25 and subsequent cycli...
Scheme 5: SalBIII catalyses dehydration of 29 and subsequent cyclisation to tetrahydropyran 30 [18].
Figure 1: All pyranonaphtoquinones contain either the naphtha[2,3-c]pyran-5,10-dione (32) or the regioisomeri...
Scheme 6: Pyran-ring formation in actinorhodin (34) biosynthesis. DNPA: 4-dihydro-9-hydroxy-1-methyl-10-oxo-3H...
Scheme 7: Pyran formation in granaticin (36) biosynthesis. DNPA: 4-dihydro-9-hydroxy-1-methyl-10-oxo-3H-napht...
Scheme 8: Pyran formation in alnumycin (37) biosynthesis. Adapted from [21].
Scheme 9: Biosynthesis of pseudomonic acid A (61). The pyran ring is initially formed in 57 after dehydrogena...
Scheme 10: Epoxidation–cyclisation leads to the formation of the tetrahydropyran ring in the western part of t...
Scheme 11: a) Nonactin (70) is formed from heterodimers of (−)(+)-dimeric nonactic acid and (+)(−)-dimeric non...
Figure 2: Pamamycins (73) are macrodiolide antibiotics containing three tetrahydrofuran moieties, which are a...
Scheme 12: A PS domain homolog in oocydin A (76) biosynthesis is proposed to catalyse furan formation via an o...
Scheme 13: Mechanism of oxidation–furan cyclisation by AurH, which converts (+)-deoxyaureothin (77) into (+)-a...
Scheme 14: Leupyrrin A2 (80) and the proposed biosynthesis of its furylidene moiety [69,70].
Scheme 15: Asperfuranone (93) biosynthesis, adapted from [75].
Figure 3: The four major aflatoxins produced by Aspergilli are the types B1, B2, G1 and G2 (94–97). In the di...
Scheme 16: Overview on aflatoxin B1 (94) biosynthesis. HOMST = 11-hydroxy-O-methylsterigmatocystin [78,79,82-106].
Scheme 17: A zipper mechanism leads to the formation of oxygen heterocycles in monensin biosynthesis [109-111].
Scheme 18: Formation of the 2,6-dioxabicyclo[3.2.1]octane (DBO) ring system in aurovertin B (118) biosynthesis ...
Figure 4: Structures of the epoxide-containing polyketides epothilone A (119) and oleandomycin (120) [123-125].
Scheme 19: Structures of phoslactomycin B (121) (a) and jerangolid A (122) (b). The heterocycle-forming steps ...
Scheme 20: a) Structures of rhizoxin (130) and cycloheximide (131). Model for the formation of δ-lactones (b) ...
Scheme 21: EncM catalyses a dual oxidation sequence and following processing of the highly reactive intermedia...
Figure 5: Mesomeric structures of tetronates [138,139].
Figure 6: Structures of tetronates for which gene clusters have been sequenced. The tetronate moiety is shown...
Scheme 22: Conserved steps for formation and processing in several 3-acyl-tetronate biosynthetic pathways were...
Scheme 23: In versipelostatin A (153) biosynthesis, VstJ is a candidate enzyme for catalysing the [4 + 2] cycl...
Scheme 24: a) Structures of some thiotetronate antibiotics. b) Biosynthesis of thiolactomycin (165) as propose...
Scheme 25: Aureusidine synthase (AS) catalyses phenolic oxidation and conjugate addition of chalcones leading ...
Scheme 26: a) Oxidative cyclisation is a key step in the biosynthesis of spirobenzofuranes 189, 192 and 193. b...
Scheme 27: A bicyclisation mechanism forms a β-lactone and a pyrrolidinone and removes the precursor from the ...
Scheme 28: Spontaneous cyclisation leads to off-loading of ebelactone A (201) from the PKS machinery [163].
Scheme 29: Mechanisms for the formation of nitrogen heterocycles.
Scheme 30: Biosynthesis of highly substituted α-pyridinones. a) Feeding experiments confirmed the polyketide o...
Scheme 31: Acridone synthase (ACS) catalyses the formation of 1,3-dihydroxy-N-methylacridone (224) by condensa...
Scheme 32: A Dieckmann condensation leads to the formation of a 3-acyl-4-hydroxypyridin-2-one 227 and removes ...
Scheme 33: a) Biosynthesis of the pyridinone tenellin (234). b) A radical mechanism was proposed for the ring-...
Scheme 34: a) Oxazole-containing PKS–NRPS-derived natural products oxazolomycin (244) and conglobatin (245). b...
Scheme 35: Structure of tetramic acids 251 (a) and major tautomers of 3-acyltetramic acids 252a–d (b). Adapted...
Scheme 36: Equisetin biosynthesis. R*: terminal reductive domain. Adapted from [202].
Scheme 37: a) Polyketides for which a similar biosynthetic logic was suggested. b) Pseurotin A (256) biosynthe...
Figure 7: Representative examples of PTMs with varying ring sizes and oxidation patterns [205,206].
Scheme 38: Ikarugamycin biosynthesis. Adapted from [209-211].
Scheme 39: Tetramate formation in pyrroindomycin aglycone (279) biosynthesis [213-215].
Scheme 40: Dieckmann cyclases catalyse tetramate or 2-pyridone formation in the biosynthesis of, for example, ...
Enantioselective additions of copper acetylides to cyclic iminium and oxocarbenium ions
- Jixin Liu,
- Srimoyee Dasgupta and
- Mary P. Watson
Beilstein J. Org. Chem. 2015, 11, 2696–2706, doi:10.3762/bjoc.11.290
- ; enantioselectivity; iminium ion; oxocarbenium ion; Introduction Nitrogen and oxygen heterocycles with α-stereogenic centers represent important classes of biologicially active compounds [1][2][3][4][5][6][7]. Enantioselective addition of chiral nucleophiles to imines, iminium ions, carbonyls, or oxocarbenium ions
Graphical Abstract
Figure 1: Chiral ligands utilized in copper-catalyzed alkynylations of cyclic iminium and oxocarbenium ions.
Scheme 1: Li’s alkynylation of acyclic N-arylimines.
Scheme 2: Knochel’s alkynylation of acyclic N-alkylenamines.
Scheme 3: Li’s CDC of tetrahydroisoquinolines and alkynes.
Scheme 4: Li’s alkynylation of N-aryldihydroisoquinolinium ions.
Scheme 5: Schreiber’s alkynylation of N-alkylisoquinolinium ions.
Scheme 6: Ma’s alkynylation of pyridium ions.
Scheme 7: Arndtsen’s alkynylation of cyclic iminium ions.
Scheme 8: Maruoka’s alkynylation of azomethine imines.
Scheme 9: Su’s CDC of tetrahydroisoquinolines and alkynes under ball milling conditions.
Scheme 10: Ma’s A3-coupling.
Scheme 11: Li’s CDC reaction using photoredox catalysis.
Scheme 12: Liu’s CDC reaction of N-carbamoyltetrahydroisoquinolines. T+BF4– = 2,2,6,6-tetramethylpiperidine N-...
Scheme 13: Aponick’s alkynylation of N-carbomoylquinolinium ions using StackPhos as ligand.
Scheme 14: Carreira’s enantioselective, catalytic alkynylation of aldehydes.
Scheme 15: Watson’s alkynylation of isochroman oxocarbenium ions.
Scheme 16: Watson’s alkynylation of chromene oxocarbenium ions.
Scheme 17: Watson’s alkynylation to set diaryl tetrasubstituted stereocenters.
Regio- and stereoselective oxidation of unactivated C–H bonds with Rhodococcus rhodochrous
- Elaine O’Reilly,
- Suzanne J. Aitken,
- Gideon Grogan,
- Paul P. Kelly,
- Nicholas J. Turner and
- Sabine L. Flitsch
Beilstein J. Org. Chem. 2012, 8, 496–500, doi:10.3762/bjoc.8.56
- us to challenge this organism with a variety of novel heterocyclic substrates. Substrates based on oxygen heterocycles were thought to be particularly interesting since, upon deprotection, they would yield polyfunctionalised molecules that represent valuable chiral intermediates. A number of p
Graphical Abstract
Scheme 1: Regioselective hydroxylation of Cbz-piperidine by Rhodococcus rhodochrous resting cells.
Scheme 2: Results from the incubation of THP ether derivatives with Rhodococcus rhodochrous showing the isola...
Scheme 3: Influence of substrate structure and linker length on the regioselectivity of hydroxylation.
Scheme 4: Regioselective hydroxylation following incubation of THF ether derivatives with Rhodococcus rhodoch...
Novel fatty acid methyl esters from the actinomycete Micromonospora aurantiaca
- Jeroen S. Dickschat,
- Hilke Bruns and
- Ramona Riclea
Beilstein J. Org. Chem. 2011, 7, 1697–1712, doi:10.3762/bjoc.7.200
- , alcohols, aldehydes, acyloins, nitrogen and oxygen heterocycles, aromatic compounds, and terpenoids. Carboxylic acids were dominating, and this class was composed of the branched isobutyric acid (49), isovaleric acid (50), and 2-methylbutyric acid (51) as the main compounds, with minor amounts of 5
Graphical Abstract
Scheme 1: Fatty acid biosynthesis.
Figure 1: Volatile methyl esters from bacteria.
Figure 2: Compounds found in the headspace extracts of M. aurantiaca.
Figure 3: Total ion chromatograms of the headspace extract from M. aurantiaca (A), and expansions of the tota...
Figure 4: FAMEs identified in the headspace extracts from M. aurantiaca.
Figure 5: Mass spectra of (A) methyl dodecanoate (83), (B) methyl 2-methyldodecanoate (10), (C) methyl 4-meth...
Scheme 2: McLafferty fragmentation of FAMEs.
Figure 6: The functional group increment FG(n)FAME, HP-5 MS.
Scheme 3: Synthesis of FAMEs identified from M. aurantiaca.
Scheme 4: Synthesis of the γ- and (ω−3)-methyl branched FAME 114.
Figure 7: Mass spectra of tentatively identified methyl 4,8-dimethyldodecanoate (115) and methyl 8-ethyl-4-me...
Recent advances in the gold-catalyzed additions to C–C multiple bonds
- He Huang,
- Yu Zhou and
- Hong Liu
Beilstein J. Org. Chem. 2011, 7, 897–936, doi:10.3762/bjoc.7.103
- attractive approach to the synthesis of functionalized ethers and ketones. In particular, the intramolecular addition of oxygen nucleophile to C–C multiple bonds has become a very effective tool in the synthesis of oxygen heterocycles from readily available starting materials [11]. 2.1 Alcohols, phenols and
- tetrasaccharide 74, which demonstrated its versatility and efficacy. Another study [43] showed that 1,6-anhydro sugars 76 and 78 could be synthesized by utilizing salient features of gold-catalyzed glycosidations. 2.2 Aldehydes and ketones as nucleophiles Different oxygen heterocycles can be obtained from the
Graphical Abstract
Scheme 1: Gold-catalyzed addition of alcohols.
Scheme 2: Gold-catalyzed cycloaddition of alcohols.
Scheme 3: Ionic liquids as the solvent in gold-catalyzed cycloaddition.
Scheme 4: Gold-catalyzed cycloaddition of diynes.
Scheme 5: Gold(I) chloride catalyzed cycloisomerization of 2-alkynyl-1,5-diols.
Scheme 6: Gold-catalyzed cycloaddition of glycols and dihydroxy compounds.
Scheme 7: Gold-catalyzed ring-opening of cyclopropenes.
Scheme 8: Gold-catalyzed intermolecular hydroalkoxylation of alkynes. PR3 = 41–45.
Scheme 9: Gold-catalyzed intramolecular 6-endo-dig cyclization of β-hydroxy-α,α-difluoroynones.
Scheme 10: Gold-catalyzed intermolecular hydroalkoxylation of non-activated olefins.
Scheme 11: Preparation of unsymmetrical ethers from alcohols.
Scheme 12: Expedient synthesis of dihydrofuran-3-ones.
Scheme 13: Catalytic approach to functionalized divinyl ketones.
Scheme 14: Gold-catalyzed glycosylation.
Scheme 15: Gold-catalyzed cycloaddition of aldehydes and ketones.
Scheme 16: Gold-catalyzed annulations of 2-(ynol)aryl aldehydes and o-alkynyl benzaldehydes.
Scheme 17: Gold-catalyzed addition of carboxylates.
Scheme 18: Dual-catalyzed rearrangement reaction of allenoates.
Scheme 19: Meyer–Schuster rearrangement of propargylic alcohols.
Scheme 20: Propargylic alcohol rearrangements.
Scheme 21: Gold-catalyzed synthesis of imines and amine alkylation.
Scheme 22: Hydroamination of allenes and allenamides.
Scheme 23: Gold-catalyzed inter- and intramolecular amination of alkynes and alkenes.
Scheme 24: Gold-catalyzed cycloisomerization of O-propioloyl oximes and β-allenylhydrazones.
Scheme 25: Intra- and intermolecular amination with ureas.
Scheme 26: Gold-catalyzed cyclization of ortho-alkynyl-N-sulfonylanilines and but-3-yn-1-amines.
Scheme 27: Gold-catalyzed piperidine ring synthesis.
Scheme 28: Ring expansion of alkylnyl cyclopropanes.
Scheme 29: Gold-catalyzed annulations of N-propargyl-β-enaminones and azomethine imines.
Scheme 30: Gold(I)-catalyzed cycloisomerization of aziridines.
Scheme 31: AuCl3/AgSbF6-catalyzed intramolecular amination of 2-(tosylamino)phenylprop-1-en-3-ols.
Scheme 32: Gold-catalyzed cyclization via a 7-endo-dig pathway.
Scheme 33: Gold-catalyzed synthesis of fused xanthines.
Scheme 34: Gold-catalyzed synthesis of amides and isoquinolines.
Scheme 35: Gold-catalyzed oxidative cross-coupling reactions of propargylic acetates.
Scheme 36: Gold-catalyzed nucleophilic addition to allenamides.
Scheme 37: Gold-catalyzed direct carbon–carbon bond coupling reactions.
Scheme 38: Gold-catalyzed C−H functionalization of indole/pyrrole heterocycles and non-activated arenes.
Scheme 39: Gold-catalyzed cycloisomerization of cyclic compounds.
Scheme 40: Gold-catalyzed cycloaddition of 1-aryl-1-allen-6-enes and propargyl acetates.
Scheme 41: Gold(I)-catalyzed cycloaddition with ligand-controlled regiochemistry.
Scheme 42: Gold(I)-catalyzed cycloaddition of dienes and enynes.
Scheme 43: Gold-catalyzed intramolecular cycloaddition of 3-alkoxy-1,5-enynes and 2,2-dipropargylmalonates.
Scheme 44: Gold-catalyzed intramolecular cycloaddition of 1,5-allenynes.
Scheme 45: Gold(I)-catalyzed cycloaddition of indoles.
Scheme 46: Gold-catalyzed annulation reactions.
Scheme 47: Gold–carbenoid induced cleavage of a sp3-hybridized C−H bond.
Scheme 48: Furan- and indole-based cascade reactions.
Scheme 49: Tandem process using aromatic alkynes.
Scheme 50: Gold-catalyzed cycloaddition of 1,3-dien-5-ynes.
Scheme 51: Gold-catalyzed cascade cyclization of diynes, propargylic esters, and 1,3-enynyl ketones.
Scheme 52: Tandem reaction of β-phenoxyimino ketones and alkynyl oxime ethers.
Scheme 53: Gold-catalyzed tandem cyclization of enynes, 2-(tosylamino)phenylprop-1-yn-3-ols, and allenoates.
Scheme 54: Cyclization of 2,4-dien-6-yne carboxylic acids.
Scheme 55: Gold(I)-catalyzed tandem cyclization approach to tetracyclic indolines.
Scheme 56: Gold-catalyzed tandem reactions of alkynes.
Scheme 57: Aminoarylation and oxyarylation of alkenes.
Scheme 58: Cycloaddition of 2-ethynylnitrobenzene with various alkenes.
Scheme 59: Gold-catalyzed tandem reactions of allenoates and alkynes.
Scheme 60: Gold-catalyzed asymmetric synthesis of 2,3-dihydropyrroles.
Scheme 61: Chiral [NHC–Au(I)]-catalyzed cyclization of enyne.
Scheme 62: Gold-catalyzed hydroaminations and hydroalkoxylations.
Scheme 63: Gold(I)-catalyzed asymmetric hydroalkoxylation of 1,3-dihydroxymethyl-2-alkynylbenzene chromium com...
Scheme 64: Gold-catalyzed synthesis of julolidine derivatives.
Scheme 65: Gold-catalyzed the synthesis of chiral fused heterocycles.
Scheme 66: Gold-catalyzed asymmetric reactions with 3,5-(t-Bu)2-4-MeO-MeOBIPHEP.
Scheme 67: Gold-catalyzed cyclization of o-(alkynyl) styrenes.
Scheme 68: Asymmetric gold(I)-catalyzed redox-neutral domino reactions of enynes.
Scheme 69: Gold(I)-catalyzed enantioselective polyene cyclization reaction.
Scheme 70: Gold(I)-catalyzed enantioselective synthesis of benzopyrans.
Scheme 71: Gold(I)-catalyzed enantioselective ring expansion of allenylcyclopropanols.
A comparative study of the Au-catalyzed cyclization of hydroxy-substituted allylic alcohols and ethers
- Berenger Biannic,
- Thomas Ghebreghiorgis and
- Aaron Aponick
Beilstein J. Org. Chem. 2011, 7, 802–807, doi:10.3762/bjoc.7.91
- corresponding ethers. Additionally, it is reported that Reaxa QuadraPureTM MPA is an efficient scavenging reagent that halts the reaction progress. Keywords: allylic alcohol; allylic ether; Au-catalyzed; SN2'; tetrahydropyran; Introduction Saturated oxygen heterocycles are found in a wide variety of
Graphical Abstract
Scheme 1: Au-catalyzed cyclization reactions of monoallylic diols.
Scheme 2: Reaction conditions for the preparation of 8.
Figure 1: QuadraPureTM MPA.
Figure 2:
Quenching experiments using 9. ![[Graphic 1]](/bjoc/content/inline/1860-5397-7-91-i3.png?max-width=637&scale=0.59091)
= quenched after 1 min; ![[Graphic 2]](/bjoc/content/inline/1860-5397-7-91-i4.png?max-width=637&scale=0.709092)
= quenched after 3 min; ![[Graphic 3]](/bjoc/content/inline/1860-5397-7-91-i5.png?max-width=637&scale=0.709092)
= quenched after ...
Figure 3: Reaction progress in cis- and trans-diols. Conditions: 5 mol % Au[P(t-Bu)2(o-biphenyl)]SbF6, CH2Cl2...
Figure 4: Reaction progress in cis- and trans-methyl ethers. Conditions: 5 mol % Au[P(t-Bu)2(o-biphenyl)]SbF6...
Figure 5: A comparison of commonly used protecting groups. Conditions: 5 mol % Au[P(t-Bu)2(o-biphenyl)]SbF6, ...
Figure 6: Comparison of 1° and 2° allylic ethers. Conditions: 5 mol % Au[P(t-Bu)2(o-biphenyl)]SbF6, CH2Cl2, M...
Methods for the synthesis of polyhydroxylated piperidines by diastereoselective dihydroxylation: Exploitation in the two-directional synthesis of aza-C-linked disaccharide derivatives
- Andrew Kennedy,
- Adam Nelson and
- Alexis Perry
Beilstein J. Org. Chem. 2005, 1, No. 2, doi:10.1186/1860-5397-1-2
- which saturated polyhydroxylated nitrogen and oxygen heterocycles are linked by an all-carbon tether. The saturated oxygen heterocycle has the potential to mimic the departing sugar in a glycosidase-catalysed reaction and aza-C-linked disaccharide mimetics may, therefore, be more potent inhibitors of
Graphical Abstract
Scheme 1:
Scheme 2:
Scheme 3:
Figure 1: Diastereoselective substitution of the N,O acetal 12
Scheme 4:
Figure 2: Diastereoselective Luche reduction of piperidinones
Scheme 5:
Figure 3: Diastereoselective dihydroxylation of unsaturated piperidines
Figure 4: Diagnostic nOe observations for the piperidine 22A
Figure 5: Diagnostic nOe observations for the piperidines 22C and 22D
Scheme 6:
Figure 6: Stereoselectivity of two-directional Luche reductions
Scheme 7:
Scheme 8:
Figure 7: Two-directional functionalisation by diastereoselective dihydroxylation
