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Search for "singlet oxygen" in Full Text gives 68 result(s) in Beilstein Journal of Organic Chemistry.
The chemical behavior of terminally tert-butylated polyolefins
- Dagmar Klein,
- Henning Hopf,
- Peter G. Jones,
- Ina Dix and
- Ralf Hänel
Beilstein J. Org. Chem. 2015, 11, 1246–1258, doi:10.3762/bjoc.11.139
- has been investigated by many authors [18][19][20]. In most cases this photooxidation involves singlet oxygen that is generated from triplet oxygen by irradiation in the presence of a sensitizer such as chlorophyll. Since the above experiment was carried out in the absence of a sensitizer, the
Graphical Abstract
Scheme 1: The polyenes 2 stabilized by terminal tert-butyl substituents.
Scheme 2: The catalytic hydrogenation of diene 3.
Figure 1: The structure of compound 4 in the crystal. Ellipsoids correspond to 30% probability levels.
Scheme 3: The catalytic hydrogenation of triene 7.
Scheme 4: Addition of bromine to model dienes.
Scheme 5: Bromine addition to diene 3 and triene 7.
Scheme 6: Bromine addition to the higher oligoenes 19–22.
Figure 2: (a) The structure of compound 24 in the crystal. Ellipsoids correspond to 50% probability levels. (...
Figure 3: The structure of compound 25 in the crystal. This was a structure of poor quality and served only t...
Scheme 7: Epoxidation of triene 7 with MCPBA and DMDO.
Scheme 8: Epoxidation of tetraene 19 with MCPBA and DMDO.
Scheme 9: Diels–Alder addition of PTAD (36) to triene 7 and tetraene 19.
Figure 4: The structure of compound 37 in the crystal. Only one of two independent molecules is shown. Ellips...
Scheme 10: Diels-Alder addition of oligoenes 20 and 21 with PTAD (36).
Scheme 11: Addition of excess PTAD (36) to hexaene 21 and heptaene 22.
Scheme 12: TCNE addition to oligoolefins: from tetraene 19 to nonaene 42.
Figure 5: The structure of compound 43 in the crystal. Only one of two independent molecules is shown. Ellips...
Scheme 13: Photochemical experiments with tetraene 19.
Figure 6: The structure of compound 52 in the crystal. Ellipsoids correspond to 50% probability levels.
The synthesis of active pharmaceutical ingredients (APIs) using continuous flow chemistry
- Marcus Baumann and
- Ian R. Baxendale
Beilstein J. Org. Chem. 2015, 11, 1194–1219, doi:10.3762/bjoc.11.134
- singlet oxygen mediated ene-reaction, a Hock cleavage of the resulting hydroperoxide 58 followed by oxidation with triplet oxygen and a final peracetalisation (Scheme 9). Based on previous work by the Seeberger group and others [63][64][65] a simple flow photoreactor set-up comprising of a layer of FEP
- -polymer tubing wrapped around a cooled medium pressure mercury lamp was used to efficiently generate and react the singlet oxygen in the presence of tetraphenylporphyrin (TPP) as a photosensitizer. Upon exiting the photoreactor, the reaction stream was acidified by combining with a stream of TFA in order
Graphical Abstract
Figure 1: Pharmaceutical structures targeted in early flow syntheses.
Scheme 1: Flow synthesis of 6-hydroxybuspirone (9). Inserted photograph reprinted with permission from [45]. Copy...
Figure 2: Configuration of a baffled reactor tube (left) and its schematic working principle (right).
Scheme 2: McQuade’s flow synthesis of ibuprofen (16).
Scheme 3: Jamison’s flow synthesis of ibuprofen sodium salt (17).
Scheme 4: Flow synthesis of imatinib (23).
Scheme 5: Flow synthesis of the potent 5HT1B antagonist 28.
Scheme 6: Flow synthesis of a selective δ-opioid receptor agonist 33.
Scheme 7: Flow synthesis of a casein kinase I inhibitor library (38).
Scheme 8: Flow synthesis of fluoxetine (46).
Scheme 9: Flow synthesis of artemisinin (55).
Scheme 10: Telescoped flow synthesis of artemisinin (55) and derivatives (62–64).
Scheme 11: Flow approach towards AZD6906 (65).
Scheme 12: Pilot scale flow synthesis of key intermediate 73.
Scheme 13: Semi-flow synthesis of vildagliptine (77).
Scheme 14: Pilot scale asymmetric flow hydrogenation towards 83. Inserted photograph reprinted with permission...
Figure 3: Schematic representation of the ‘tube-in-tube’ reactor.
Scheme 15: Flow synthesis of fanetizole (87) via tube-in-tube system.
Scheme 16: Flow synthesis of diphenhydramine.HCl (92).
Scheme 17: Flow synthesis of rufinamide (95).
Scheme 18: Large scale flow synthesis of rufinamide precursor 102.
Scheme 19: First stage in the flow synthesis of meclinertant (103).
Scheme 20: Completion of the flow synthesis of meclinertant (103).
Scheme 21: Flow synthesis of olanzapine (121) utilising inductive heating techniques.
Scheme 22: Flow synthesis of amitriptyline·HCl (127).
Scheme 23: Flow synthesis of E/Z-tamoxifen (132) using peristaltic pumping modules.
Figure 4: Container sized portable mini factory (photograph credit: INVITE GmbH, Leverkusen Germany).
Scheme 24: Flow synthesis of imidazo[1,2-a]pyridines 136 linked to frontal affinity chromatography (FAC).
Figure 5: Structures of zolpidem (142) and alpidem (143).
Scheme 25: Synthesis and screening loops in the discovery of new Abl kinase inhibitors.
Figure 6: Schotten–Baumann approach towards LY573636.Na (147).
Scheme 26: Pilot scale flow synthesis of LY2886721 (146).
Scheme 27: Continuous flow manufacture of alikiren hemifumarate 152.
Electrochemical oxidation of cholesterol
- Jacek W. Morzycki and
- Andrzej Sobkowiak
Beilstein J. Org. Chem. 2015, 11, 392–402, doi:10.3762/bjoc.11.45
- ) when hydrogen peroxide was combined with superoxide solution in water matrix. The authors suggested that under these conditions the rate of the disproportionation reaction of superoxide radical anion is increased, and the formation of more reactive oxygen species such as hydroxyl radical or singlet
- oxygen is possible. A stereoselective electrochemical method of the chlorination of steroidal Δ5-olefins was described by Takayama et al. [38]. The oxidation of cholesterol was carried out in an undivided cell under constant current conditions in CH2Cl2/MeCN/H2O (2:2:1), the cathode and anode being
Graphical Abstract
Figure 1: Preferential sites of cholesterol electrooxidation.
Scheme 1: Functionalization of the cholesterol side chain.
Scheme 2: Oxidation of cholestane-3β,5α,6β-triol triacetate (3) with the Gif system.
Scheme 3: Electrochemical oxidation of cholesteryl acetate (1a) with dioxygen and iron–picolinate complexes.
Scheme 4: Electrochemical chlorination of cholesterol catalyzed by FeCl3.
Scheme 5: Electrochemical chlorination of Δ5-steroids.
Scheme 6: Electrochemical bromination of Δ5-steroids in different solvents.
Scheme 7: Direct electrochemical acetoxylation of cholesterol at the allylic position.
Scheme 8: Direct anodic oxidation of cholesterol in dichloromethane.
Scheme 9: A plausible mechanism of the electrochemical oxidation of cholesterol in dichloromethane.
Scheme 10: The electrochemical formation of glycosides and glycoconjugates.
Scheme 11: Efficient electrochemical oxidation of cholesterol to cholesta-4,6-dien-3-one (24).
Oxidative phenylamination of 5-substituted 1-hydroxynaphthalenes to N-phenyl-1,4-naphthoquinone monoimines by air and light “on water”
- Julio Benites,
- Juan Meléndez,
- Cynthia Estela,
- David Ríos,
- Luis Espinoza,
- Iván Brito and
- Jaime A. Valderrama
Beilstein J. Org. Chem. 2014, 10, 2448–2452, doi:10.3762/bjoc.10.255
- by on-water oxidative phenylamination of 1,5-dihydroxynaphthalene (1) and 5-acetylamino-1-hydroxynaphthalene (5) with oxygen-substituted phenylamines under aerobic conditions and either solar or green LED radiation, in the presence of rose bengal as singlet oxygen sensitizer. As compared to the
- green route for the preparation of N-phenyl-1,4-naphthoquinone monoimines by on-water oxidative coupling reaction of 1-hydroxynaphthalene derivatives with oxygen-substituted phenylamines under solar light or green LEDs radiation, rose bengal as singlet oxygen sensitizer and aerobic conditions. Results
- then in the same flask, the arylamination of 2 to the respective aminoquinones was accomplished [14]. The on-water photooxygenation of 1,5-DHN (1) was carried out for 5 h in round-bottom flasks, under the presence of 1.6 mmol % of rose bengal (RB) as singlet oxygen sensitizer, by using sunlight
Graphical Abstract
Figure 1: Structures of compounds 1–3.
Scheme 1: Hypothetical one-pot synthesis of compound 4a and/or 4b.
Figure 2: Structure of compound 6 determined by single crystal X-ray diffractometry.
Scheme 2: Evaluation of the substrate scope using RB as oxygen (1O2) sensitizer “on water”.
Scheme 3: Evaluation of the oxidative coupling in the absence of RB, on water.
Photo, thermal and chemical degradation of riboflavin
- Muhammad Ali Sheraz,
- Sadia Hafeez Kazi,
- Sofia Ahmed,
- Zubair Anwar and
- Iqbal Ahmad
Beilstein J. Org. Chem. 2014, 10, 1999–2012, doi:10.3762/bjoc.10.208
- different mechanisms [36][41][42][46][47][50][51][52][53][54][55][56][57]. RF also forms singlet oxygen from the ordinary triplet oxygen under light by the excited triplet RF and triplet oxygen annihilation mechanism which plays a part in photosensitized reactions [58][59]. FMF, LC and LF are formed by the
- identified as 2,3-butanedione and is produced from the side-chain of RF by the action of singlet oxygen. Its formation is greatly affected by the pH of the medium as the highest content of this compound was found at pH 6.5, followed by 4.5 and 8.5 [59]. RF is highly sensitive to pH and has pKa values of 1.7
- mechanisms. Ascorbic acid quenches both singlet oxygen and excited triplet states of RF whereas sodium azide quenches only the singlet oxygen in RF solution. Due to the dual activity, ascorbic acid is a comparatively better quencher than sodium azide. RF destructions were 94% and ~16% when photodegraded in
Graphical Abstract
Figure 1: Structures of RF and its photoproducts.
Figure 2: A general scheme for the photodegradation of RF in aqueous solution.
Figure 3: log k–pH profiles for the photolysis of RF in aqueous solution using UV light (∆) and visible light...
Figure 4: log k–pH profiles for the photolysis of FMF (10−4 M) in alkaline solution under aerobic (○) and ana...
Figure 5: k'–pH profiles for the photolysis of FMF (10−4 M) in acidic solution under aerobic (○) and anaerobi...
Figure 6: Plots of k` versus pH for phosphate (▲) and sulfate (●) anion-catalyzed photodegradation of RF (5 ×...
Figure 7: log kobs–pH profiles for the photolysis of RF (5 × 10−5 M) in 0.1–0.5 M borate buffer. Experimental...
Figure 8: log kobs–pH profiles for the photolysis of RF (5 × 10−5 M) in 0.2–1.0 M citrate buffer. Experimenta...
Figure 9: k'–pH profile for the photolysis of RF (5 × 10−5 M) in the presence of CF (0.5–2.5 × 10−4 M). Exper...
Cyclization–endoperoxidation cascade reactions of dienes mediated by a pyrylium photoredox catalyst
- Nathan J. Gesmundo and
- David A. Nicewicz
Beilstein J. Org. Chem. 2014, 10, 1272–1281, doi:10.3762/bjoc.10.128
- challenges. Classical approaches to the introduction of cyclic peroxides typically rely on cycloadditions of alkenes and dienes with singlet oxygen. However, ene processes can often compete, leading to complex mixtures of hydroperoxide adducts [1][6][7][8]. More recently, cyclization reactions of
- single electron oxidants capable of this task, we elected to employ photooxidation catalysts. Additionally, we sought to select visible light-activated organic single electron oxidants that do not readily sensitize singlet oxygen [17][18][19]. For these reasons, we were attracted to the use of
- , to exclude the intervention of a singlet oxygen mechanism, we conducted the reaction in the presence of Rose Bengal. Under these conditions, we observed only 1O2 ene reactivity with the isoprenyl group (65% yield of hydroperoxide), underscoring the unique reactivity garnered by this catalyst system
Graphical Abstract
Figure 1: Selected examples of endoperoxide-containing natural products.
Scheme 1: Endoperoxide formation via cation radicals. In both examples, single electron oxidation is followed...
Scheme 2: Diversification strategy for endoperoxide synthesis by single electron transfer. E*red vs SCE [20].
Figure 2: ORTEP of 3a.
Scheme 3: Proposed mechanism for endoperoxide synthesis from tethered dienes.
Scheme 4: Competing formal [3,3] pathway.
From porphyrin benzylphosphoramidate conjugates to the catalytic hydrogenation of 5,10,15,20-tetrakis(pentafluorophenyl)porphyrin
- Marcos C. de Souza,
- Leandro F. Pedrosa,
- Géssica S. Cazagrande,
- Vitor F. Ferreira,
- Maria G. P. M. S. Neves and
- José A. S. Cavaleiro
Beilstein J. Org. Chem. 2014, 10, 628–633, doi:10.3762/bjoc.10.54
- recently synthesized porphyrin diisopropylphosphoramidate conjugates derived from 5,10,15,20-tetrakis(pentafluorophenyl)porphyrin (TPPF20). Such compounds showed a high photostability and a good capacity to generate singlet oxygen, but their solubility in water is moderate [4]. Additionally, we tried to
Graphical Abstract
Scheme 1: Synthesis of porphyrin aminoalkylphosphoramidates 1a–c, and of chlorin (TPCF20) and isobacteriochlo...
Figure 1: UV–vis spectrum (CHCl3) of the crude mixture obtained from the hydrogenation of 1a and 1b over 10% ...
Figure 2: Main products from the hydrogenation of TPPF20 with 10% Pd/C. Comparative UV–vis spectra of isolate...
Synthesis of five- and six-membered cyclic organic peroxides: Key transformations into peroxide ring-retaining products
- Alexander O. Terent'ev,
- Dmitry A. Borisov,
- Vera A. Vil’ and
- Valery M. Dembitsky
Beilstein J. Org. Chem. 2014, 10, 34–114, doi:10.3762/bjoc.10.6
- peroxides are based on three key reagents: oxygen, ozone, and hydrogen peroxide. These reagents and their derivatives are used in the main methods for the introduction of the peroxide group, such as the singlet-oxygen ene reaction with alkenes, the [4 + 2]-cycloaddition of singlet oxygen to dienes, the
- peroxide moiety, the Isayama–Mukaiyama peroxysilylation, and reactions involving peroxycarbenium ions. Syntheses employing hydrogen peroxide and the intramolecular Kobayashi cyclization are less frequently used. 1.1. Use of oxygen for the peroxide ring formation The singlet-oxygen ene reaction with alkenes
- the oxidation of cyclopropanes by oxygen in the presence of transition-metal salts as the catalysts. The reactions of bicycloalkanols 10a–e with singlet oxygen in the presence of catalytic amounts of Fe(III) acetylacetonate produce peroxides 12a–e, which can also be synthesized starting from silylated
Graphical Abstract
Figure 1: Five and six-membered cyclic peroxides.
Figure 2: Artemisinin and semi-synthetic derivatives.
Scheme 1: Synthesis of 3-hydroxy-1,2-dioxolanes 3a–c.
Scheme 2: Synthesis of dioxolane 6.
Scheme 3: Photooxygenation of oxazolidines 7a–d with formation of spiro-fused oxazolidine-containing dioxolan...
Scheme 4: Oxidation of cyclopropanes 10a–e and 11a–e with preparation of 1,2-dioxolanes 12a–e.
Scheme 5: VO(acac)2-catalyzed oxidation of silylated bicycloalkanols 13a–c.
Scheme 6: Mn(II)-catalyzed oxidation of cyclopropanols 15a–g.
Scheme 7: Oxidation of aminocyclopropanes 20a–c.
Scheme 8: Synthesis of aminodioxolanes 24.
Figure 3: Trifluoromethyl-containing dioxolane 25.
Scheme 9: Synthesis of 1,2-dioxolanes 27a–e by the oxidation of cyclopropanes 26a–e.
Scheme 10: Photoinduced oxidation of methylenecyclopropanes 28.
Scheme 11: Irradiation-mediated oxidation.
Scheme 12: Application of diazene 34 for dioxolane synthesis.
Scheme 13: Mn(OAc)3-catalyzed cooxidation of arylacetylenes 37a–h and acetylacetone with atmospheric oxygen.
Scheme 14: Peroxidation of (2-vinylcyclopropyl)benzene (40).
Scheme 15: Peroxidation of 1,4-dienes 43a,b.
Scheme 16: Peroxidation of 1,5-dienes 46.
Scheme 17: Peroxidation of oxetanes 53a,b.
Scheme 18: Peroxidation of 1,6-diene 56.
Scheme 19: Synthesis of 3-alkoxy-1,2-dioxolanes 62a,b.
Scheme 20: Synthesis of spiro-bis(1,2-dioxolane) 66.
Scheme 21: Synthesis of dispiro-1,2-dioxolanes 68, 70, 71.
Scheme 22: Synthesis of spirohydroperoxydioxolanes 75a,b.
Scheme 23: Synthesis of spirohydroperoxydioxolane 77 and dihydroperoxydioxolane 79.
Scheme 24: Ozonolysis of azepino[4,5-b]indole 80.
Scheme 25: SnCl4-mediated fragmentation of ozonides 84a–l in the presence of allyltrimethylsilane.
Scheme 26: SnCl4-mediated fragmentation of bicyclic ozonide 84m in the presence of allyltrimethylsilane.
Scheme 27: MCl4-mediated fragmentation of alkoxyhydroperoxides 96 in the presence of allyltrimethylsilane.
Scheme 28: SnCl4-catalyzed reaction of monotriethylsilylperoxyacetal 108 with alkene 109.
Scheme 29: SnCl4-catalyzed reaction of triethylsilylperoxyacetals 111 with alkenes.
Scheme 30: Desilylation of tert-butyldimethylsilylperoxy ketones 131a,b followed by cyclization.
Scheme 31: Deprotection of peroxide 133 followed by cyclization.
Scheme 32: Asymmetric peroxidation of methyl vinyl ketones 137a–e.
Scheme 33: Et2NH-catalyzed intramolecular cyclization.
Scheme 34: Synthesis of oxodioxolanes 143a–j.
Scheme 35: Haloperoxidation accompanied by intramolecular ring closure.
Scheme 36: Oxidation of triterpenes 149a–d with Na2Cr2O7/N-hydroxysuccinimide.
Scheme 37: Curtius and Wolff rearrangements to form 1,2-dioxolane ring-retaining products.
Scheme 38: Oxidative desilylation of peroxide 124.
Scheme 39: Synthesis of dioxolane 158, a compound containing the aminoquinoline antimalarial pharmacophore.
Scheme 40: Diastereomers of plakinic acid A, 162a and 162b.
Scheme 41: Ozonolysis of alkenes.
Scheme 42: Cross-ozonolysis of alkenes 166 with carbonyl compounds.
Scheme 43: Ozonolysis of the bicyclic cyclohexenone 168.
Scheme 44: Cross-ozonolysis of enol ethers 172a,b with cyclohexanone.
Scheme 45: Griesbaum co-ozonolysis.
Scheme 46: Reactions of aryloxiranes 177a,b with oxygen.
Scheme 47: Intramolecular formation of 1,2,4-trioxolane 180.
Scheme 48: Formation of 1,2,4-trioxolane 180 by the reaction of 1,5-ketoacetal 181 with H2O2.
Scheme 49: 1,2,4-Trioxolane 186 with tetrazole fragment.
Scheme 50: 1,2,4-Trioxolane 188 with a pyridine fragment.
Scheme 51: 1,2,4-Trioxolane 189 with pyrimidine fragment.
Scheme 52: Synthesis of aminoquinoline-containing 1,2,4-trioxalane 191.
Scheme 53: Synthesis of arterolane.
Scheme 54: Oxidation of diarylheptadienes 197a–c with singlet oxygen.
Scheme 55: Synthesis of hexacyclinol peroxide 200.
Scheme 56: Oxidation of enone 201 and enenitrile 203 with singlet oxygen.
Scheme 57: Synthesis of 1,2-dioxanes 207 by oxidative coupling of carbonyl compounds 206 and alkenes 205.
Scheme 58: 1,2-Dioxanes 209 synthesis by co-oxidation of 1,5-dienes 208 and thiols.
Scheme 59: Synthesis of bicyclic 1,2-dioxanes 212 with aryl substituents.
Scheme 60: Isayama–Mukaiyama peroxysilylation of 1,5-dienes 213 followed by desilylation under acidic conditio...
Scheme 61: Synthesis of bicycle 218 with an 1,2-dioxane ring.
Scheme 62: Intramolecular cyclization with an oxirane-ring opening.
Scheme 63: Inramolecular cyclization with the oxetane-ring opening.
Scheme 64: Intramolecular cyclization with the attack on a keto group.
Scheme 65: Peroxidation of the carbonyl group in unsaturated ketones 228 followed by cyclization of hydroperox...
Scheme 66: CsOH and Et2NH-catalyzed cyclization.
Scheme 67: Preparation of peroxyplakoric acid methyl ethers A and D.
Scheme 68: Hg(OAc)2 in 1,2-dioxane synthesis.
Scheme 69: Reaction of 1,4-diketones 242 with hydrogen peroxide.
Scheme 70: Inramolecular cyclization with oxetane-ring opening.
Scheme 71: Inramolecular cyclization with MsO fragment substitution.
Scheme 72: Synthesis of 1,2-dioxane 255a, a structurally similar compound to natural peroxyplakoric acids.
Scheme 73: Synthesis of 1,2-dioxanes based on the intramolecular cyclization of hydroperoxides containing C=C ...
Scheme 74: Use of BCIH in the intramolecular cyclization.
Scheme 75: Palladium-catalyzed cyclization of δ-unsaturated hydroperoxides 271a–e.
Scheme 76: Intramolecular cyclization of unsaturated peroxyacetals 273a–d.
Scheme 77: Allyltrimethylsilane in the synthesis of 1,2-dioxanes 276a–d.
Scheme 78: Intramolecular cyclization using the electrophilic center of the peroxycarbenium ion 279.
Scheme 79: Synthesis of bicyclic 1,2-dioxanes.
Scheme 80: Preparation of 1,2-dioxane 286.
Scheme 81: Di(tert-butyl)peroxalate-initiated radical cyclization of unsaturated hydroperoxide 287.
Scheme 82: Oxidation of 1,4-betaines 291a–d.
Scheme 83: Synthesis of aminoquinoline-containing 1,2-dioxane 294.
Scheme 84: Synthesis of the sulfonyl-containing 1,2-dioxane.
Scheme 85: Synthesis of the amido-containing 1,2-dioxane 301.
Scheme 86: Reaction of singlet oxygen with the 1,3-diene system 302.
Scheme 87: Synthesis of (+)-premnalane А and 8-epi-premnalane A.
Scheme 88: Synthesis of the diazo group containing 1,2-dioxenes 309a–e.
Figure 4: Plakortolide Е.
Scheme 89: Synthesis of 6-epiplakortolide Е.
Scheme 90: Application of Bu3SnH for the preparation of tetrahydrofuran-containing bicyclic peroxides 318a,b.
Scheme 91: Application of Bu3SnH for the preparation of lactone-containing bicyclic peroxides 320a–f.
Scheme 92: Dihydroxylation of the double bond in the 1,2-dioxene ring 321 with OsO4.
Scheme 93: Epoxidation of 1,2-dioxenes 324.
Scheme 94: Cyclopropanation of the double bond in endoperoxides 327.
Scheme 95: Preparation of pyridazine-containing bicyclic endoperoxides 334a–c.
Scheme 96: Synthesis of 1,2,4-trioxanes 337 by the hydroperoxidation of unsaturated alcohols 335 with 1O2 and ...
Scheme 97: Synthesis of sulfur-containing 1,2,4-trioxanes 339.
Scheme 98: BF3·Et2O-catalyzed synthesis of the 1,2,4-trioxanes 342a–g.
Scheme 99: Photooxidation of enol ethers or vinyl sulfides 343.
Scheme 100: Synthesis of tricyclic peroxide 346.
Scheme 101: Reaction of endoperoxides 348a,b derived from cyclohexadienes 347a,b with 1,4-cyclohexanedione.
Scheme 102: [4 + 2]-Cycloaddition of singlet oxygen to 2Н-pyrans 350.
Scheme 103: Synthesis of 1,2,4-trioxanes 354 using peroxysilylation stage.
Scheme 104: Epoxide-ring opening in 355 with H2O2 followed by the condensation of hydroxy hydroperoxides 356 wi...
Scheme 105: Peroxidation of unsaturated ketones 358 with the H2O2/CF3COOH/H2SO4 system.
Scheme 106: Synthesis of 1,2,4-trioxanes 362 through Et2NH-catalyzed intramolecular cyclization.
Scheme 107: Reduction of the double bond in tricyclic peroxides 363.
Scheme 108: Horner–Wadsworth–Emmons reaction in the presence of peroxide group.
Scheme 109: Reduction of ester group by LiBH4 in the presence of 1,2,4-trioxane moiety.
Scheme 110: Reductive amination of keto-containing 1,2,4-trioxane 370.
Scheme 111: Reductive amination of keto-containing 1,2,4-trioxane and a Fe-containing moiety.
Scheme 112: Acid-catalyzed reactions of Н2О2 with ketones and aldehydes 374.
Scheme 113: Cyclocondensation of carbonyl compounds 376a–d using Me3SiOOSiMe3/CF3SO3SiMe3.
Scheme 114: Peroxidation of 4-methylcyclohexanone (378).
Scheme 115: Synthesis of symmetrical tetraoxanes 382a,b from aldehydes 381a,b.
Scheme 116: Synthesis of unsymmetrical tetraoxanes using of MeReO3.
Scheme 117: Synthesis of symmetrical tetraoxanes using of MeReO3.
Scheme 118: Synthesis of symmetrical tetraoxanes using of MeReO3.
Scheme 119: MeReO3 in the synthesis of symmetrical tetraoxanes with the use of aldehydes.
Scheme 120: Preparation of unsymmmetrical 1,2,4,5-tetraoxanes with high antimalarial activity.
Scheme 121: Re2O7-Catalyzed synthesis of tetraoxanes 398.
Scheme 122: H2SO4-Catalyzed synthesis of steroidal tetraoxanes 401.
Scheme 123: HBF4-Catalyzed condensation of bishydroperoxide 402 with 1,4-cyclohexanedione.
Scheme 124: BF3·Et2O-Catalyzed reaction of gem-bishydroperoxides 404 with enol ethers 405 and acetals 406.
Scheme 125: HBF4-Catalyzed cyclocondensation of bishydroperoxide 410 with ketones.
Scheme 126: Synthesis of symmetrical and unsymmetrical tetraoxanes 413 from benzaldehydes 412.
Scheme 127: Synthesis of bridged 1,2,4,5-tetraoxanes 415a–l from β-diketones 414a–l and H2O2.
Scheme 128: Dimerization of zwitterions 417.
Scheme 129: Ozonolysis of verbenone 419.
Scheme 130: Ozonolysis of O-methyl oxime 424.
Scheme 131: Peroxidation of 1,1,1-trifluorododecan-2-one 426 with oxone.
Scheme 132: Intramolecular cyclization of dialdehyde 428 with H2O2.
Scheme 133: Tetraoxanes 433–435 as by-products in peroxidation of ketals 430–432.
Scheme 134: Transformation of triperoxide 436 in diperoxide 437.
Scheme 135: Preparation and structural modifications of tetraoxanes.
Scheme 136: Structural modifications of steroidal tetraoxanes.
Scheme 137: Synthesis of 1,2,4,5-tetraoxane 454 containing the fluorescent moiety.
Scheme 138: Synthesis of tetraoxane 458 (RKA182).
Studies on the photodegradation of red, green and blue phosphorescent OLED emitters
- Susanna Schmidbauer,
- Andreas Hohenleutner and
- Burkhard König
Beilstein J. Org. Chem. 2013, 9, 2088–2096, doi:10.3762/bjoc.9.245
- the samples in different solvents and under atmospheric as well as inert conditions helped to identify several pathways that can contribute to the deterioration of these compounds. Degradation via singlet oxygen or the excited states of the emitters as well as the detrimental influence of halogenated
- , though only as a side product, while no indication of halogen abstraction was found for the other two complexes. The influence of dioxygen As cyclometalated Ir-complexes are very efficient singlet oxygen sensitizers we investigated the influence of oxygen on the photostability of the compounds. 1O2 is
- -thaw, then argon atmosphere). All compounds were irradiated in CH2Cl2 and toluene as mentioned above, but also in benzene and benzene-d6. Singlet oxygen has a significantly higher lifetime in deuterated solvents, resulting in an effective enhancement of the reaction rates of singlet oxygen. Processes
Graphical Abstract
Figure 1: Structures of the investigated phosphorescent triscyclometalated iridium complexes.
Figure 2: Photodegradation of the different compounds in toluene under ambient atmosphere. Plotted is the rat...
Figure 3: Photodegradation behavior of the iridium complexes in CH2Cl2 and toluene solution and in a spin-coa...
Figure 4: Mass spectra of the identified halogenated degradation products of a) Ir(ppy)3 after 200 min of irr...
Figure 5: Degradation curves of Ir(piq)3 in benzene and benzene-d6 under ambient and inert conditions (left)....
Figure 6: DAD chromatogram showing the formation of two main degradation products (left) and their assigned m...
Figure 7: Degradation curves of Ir(ppy)3 in benzene and benzene-d6 under ambient and inert conditions, and ma...
Figure 8: (a) Degradation curves of Ir(Me-ppy)3 in benzene and benzene-d6 under ambient and inert conditions....
Figure 9: Degradation curves of Ir(F,CN-ppy)3 in benzene, benzene-d6 and toluene under ambient conditions and...
The chemistry of amine radical cations produced by visible light photoredox catalysis
- Jie Hu,
- Jiang Wang,
- Theresa H. Nguyen and
- Nan Zheng
Beilstein J. Org. Chem. 2013, 9, 1977–2001, doi:10.3762/bjoc.9.234
- the adduct of superoxide to DMPO. In contrast, an ESR study on the same solution but with DMPO being replaced by TEMP (2,3,6,6-tetramethylpiperidine) did not detect TEMPO, the oxidation product of TEMP by singlet oxygen. However, TEMPO was detected in the absence of N-phenyltetrahydroisoquinoline. The
- results from these ESR studies are consistent with the notion that singlet oxygen is not formed in the presence of N-phenyltetrahydroisoquinoline and the Eosin Y radical anion reduces oxygen to superoxide. Finally, the yield of the product 18 increased when the reaction mixture was kept stirring in the
Graphical Abstract
Scheme 1: Amine radical cations’ mode of reactivity.
Scheme 2: Reductive quenching of photoexcited Ru complexes by Et3N.
Scheme 3: Photoredox aza-Henry reaction.
Scheme 4: Formation of iminium ions using BrCCl3 as stoichiometric oxidant.
Scheme 5: Oxidative functionalization of N-aryltetrahydroisoquinolines using Eosin Y.
Scheme 6: Synthetic and mechanistic studies of Eosin Y-catalyzed aza-Henry reaction.
Scheme 7: Oxidative functionalization of N-aryltetrahydroisoquinolines using RB and GO.
Scheme 8: Merging Ru-based photoredox catalysis and Lewis base catalysis for the Mannich reaction.
Scheme 9: Merging Au-based photoredox catalysis and Lewis base catalysis for the Mannich reaction.
Scheme 10: Merging Ru-based photoredox catalysis and Cu-catalyzed alkynylation reaction.
Scheme 11: Merging Ru-based photoredox catalysis and NHC catalysis.
Scheme 12: 1,3-Dipolar cycloaddition of photogenically formed azomethine ylides.
Scheme 13: Plausible mechanism for photoredox 1,3-dipolar cycloaddition.
Scheme 14: Photoredox-catalyzed cascade reaction for the synthesis of fused isoxazolidines.
Scheme 15: Plausible mechanism for the photoredox-catalyzed cascade reaction.
Scheme 16: Photoredox-catalyzed α-arylation of glycine derivatives.
Scheme 17: Photoredox-catalyzed α-arylation of amides.
Scheme 18: Intramolecular interception of iminium ions by sulfonamides.
Scheme 19: Intramolecular interception of iminium ions by alcohols and sulfonamides.
Scheme 20: Intermolecular interception of iminium ions by phosphites.
Scheme 21: Photoredox-catalyzed oxidative phosphonylation by Eosin Y.
Scheme 22: Conjugated addition of α-amino radicals to Michael acceptors.
Scheme 23: Conjugated addition of α-amino radicals to Michael acceptors assisted by a Brønsted acid.
Scheme 24: Conjugated addition of α-amino radicals derived from anilines to Michael acceptors.
Scheme 25: Oxygen switch between two pathways involving α-amino radicals.
Scheme 26: Interception of α-amino radicals by azodicarboxylates.
Scheme 27: α-Arylation of amines.
Scheme 28: Plausible mechanism for α-arylation of amines.
Scheme 29: Photoinduced C–C bond cleavage of tertiary amines.
Scheme 30: Photoredox cleavage of C–C bonds of 1,2-diamines.
Scheme 31: Proposed mechanism photoredox cleavage of C–C bonds.
Scheme 32: Intermolecular [3 + 2] annulation of cyclopropylamines with olefins.
Scheme 33: Proposed mechanism for intermolecular [3 + 2] annulation.
Scheme 34: Photoinduced clevage of N–N bonds of aromatic hydrazines and hydrazides.
Flow photochemistry: Old light through new windows
- Jonathan P. Knowles,
- Luke D. Elliott and
- Kevin I. Booker-Milburn
Beilstein J. Org. Chem. 2012, 8, 2025–2052, doi:10.3762/bjoc.8.229
- the lower-power light source. These longer residence times further lowered the reactor productivity to 0.15 mmol/h [24]. Photooxygenations Direct oxygenation of organic molecules through the photosensitised addition of singlet oxygen represents an atom-economic method of functionalisation and is
- of bulk solutions, which combined with the extremely short lifetime of singlet oxygen means that lengthy irradiations are often required. These issues can be overcome through the use of continuous-flow chemistry: reactions performed in this manner have only a small amount of oxygenated solvent and
- peroxide product present at any one time, and this can be reduced immediately upon leaving the reactor. The smaller reactor volumes involved in flow chemistry also mean that irradiation is efficient and hence that the singlet oxygen generated can react within its short lifetime. Falling-film microreactors
Graphical Abstract
Figure 1: An immersion-well batch reactor with 125 W medium pressure Hg lamp.
Figure 2: Transmission profile of a 0.05 M solution, ε = 200 M−1 cm−1.
Figure 3: Schematic of a typical microflow photochemical reactor (above) and detail of a triple-channel micro...
Figure 4: Schematic of a typical macroflow photochemical reactor (above) and images of the FEP photochemical ...
Scheme 1: [2 + 2] photocycloadditions of enones with enol derivatives.
Scheme 2: Competing reactions in an intramolecular [2 + 2] photocycloaddition.
Scheme 3: Diastereocontrolled cycloaddition of a cyclic enone with cyclopentene.
Scheme 4: Comparison of yields and reaction times for a batch reactor with a microflow system.
Scheme 5: Intramolecular [2 + 2] photocycloaddition.
Scheme 6: Paterno–Büchi reaction of benzophenone with an allylic alcohol.
Scheme 7: Photooxygenation of cyclopentadiene.
Scheme 8: Preparation of the anthelmintic ascaridole 23.
Scheme 9: Production of rose oxide 27 from (−)-β-citronellol (24).
Scheme 10: Photocatalytic alkylation of benzylamine.
Scheme 11: Photocatalytic reduction of 4-nitroacetophenone.
Scheme 12: Conversion of L-lysine to L-pipecolinic acid.
Scheme 13: Photocatalytic hydrodehalogenation.
Scheme 14: Photocatalytic aza-Henry reactions.
Scheme 15: Photocatalytic α-alkylation of aliphatic ketones.
Scheme 16: Decarboxylative photochemical additions.
Scheme 17: Photochemical addition of isopropanol to furanones.
Scheme 18: Photochemical addition of methanol to limonene.
Scheme 19: Light-promoted reduction of flavone.
Scheme 20: Photoreduction of benzophenone with benzhydrol.
Scheme 21: Barton reaction in a microflow system.
Scheme 22: Microflow synthesis of vitamin D3.
Scheme 23: photochemical chlorination of cyclohexane.
Scheme 24: photochemical cyanation of pyrene.
Scheme 25: Intermolecular [2 + 2] cycloaddition of maleimide (76) and intramolecular [2 + 2] cycloaddition of ...
Scheme 26: Intramolecular [5 + 2] cycloaddition of maleimide under flow conditions.
Scheme 27: Intramolecular [5 + 2] cycloaddition as a key step in the synthesis of (±)-neostenine.
Scheme 28: In situ generation of a thioaldehyde by photolysis of a phenacyl sulfide.
Scheme 29: Photodimerisation of maleic anhydride.
Scheme 30: [2 + 2] cycloaddition of a chiral enone with ethylene.
Scheme 31: Intramolecular [2 + 2] cycloaddition of a cyclopentenone.
Scheme 32: Photochemical Wolff rearrangement and cyclisation to β-lactams.
Scheme 33: Photochemical rearrangement of aryl azides.
Scheme 34: Rearrangement of quinoline N-oxides to quinolones.
Scheme 35: Photochemical rearrangement of cyclobutenones.
Scheme 36: Photoisomerisation en route to a vitamin-D derivative.
Scheme 37: Schematic of the Seeberger photooxygenation apparatus and sensitised photooxygenation of citronello...
Scheme 38: Sensitised photooxygenation of dihydroartemisinic acid.
Scheme 39: Photochemical preparation of CpRu(MeCN)3PF6.
Scheme 40: In situ photochemical generation and reaction of a [CpRu]+ catalyst.
Scheme 41: Intermolecular alkene–alkyne coupling with photogenerated catalyst.
Scheme 42: PET deoxygenation of nucleosides.
Scheme 43: Photochemical defluorination of DABFT.
Scheme 44: Aromatic azide reduction by visible-light-mediated photocatalysis.
Scheme 45: Examples of visible-light-mediated reactions.
Scheme 46: Visible-light-mediated formation of iminium ions.
Scheme 47: Examples of visible-light-mediated photocatalytic reactions.
Scheme 48: Anhydride formation from a visible-light-mediated process.
Scheme 49: Light-mediated conjugate addition of glycosyl bromide 141 to acrolein.
Scheme 50: Visible-light-mediated photocyclisation to [5]helicene.
The chemistry of bisallenes
- Henning Hopf and
- Georgios Markopoulos
Beilstein J. Org. Chem. 2012, 8, 1936–1998, doi:10.3762/bjoc.8.225
Graphical Abstract
Figure 1: Loschmidt’s structure proposal for benzene (1) (Scheme 181 from [3]) and the corresponding modern stru...
Figure 2: The first isolated bisallenes.
Figure 3: Carbon skeletons of selected bisallenes discussed in this review.
Scheme 1: The preparation of 1,2,4,5-hexatetraene (2).
Scheme 2: The preparation of a conjugated bisallene by the DMS-protocol.
Scheme 3: Preparation of the 3-deuterio- and 3,4-dideuterio derivatives of 24.
Scheme 4: A versatile method to prepare alkylated conjugated bisallenes and other allenes.
Scheme 5: A preparation of 3,4-dimethyl-1,2,4,5-hexatetraene (38).
Scheme 6: A (C6 + 0)-approach to 1,2,4,5-hexatetraene (2).
Scheme 7: The preparation of a fully alkylated bisallenes from a 2,4-hexadiyne-1,6-diol diacetate.
Scheme 8: The preparation of the first phenyl-substituted conjugated bisallenes 3 and 4.
Scheme 9: Selective hydrogenation of [5]cumulenes to conjugated bisallenes: another (C6 + 0)-route.
Scheme 10: Aryl-substituted conjugated bisallenes by a (C3 + C3)-approach.
Scheme 11: Hexaphenyl-1,2,4,5-hexatetraene (59) by a (C3 + C3)-approach.
Scheme 12: An allenation route to conjugated bisallenes.
Scheme 13: The preparation of 3,4-difunctionalized conjugated bisallenes.
Scheme 14: Problems during the preparation of sulfur-substituted conjugated bisallenes.
Scheme 15: The preparation of 3,4-dibromo bisallenes.
Scheme 16: Generation of allenolates by an oxy-Cope rearrangement.
Scheme 17: A linear trimerization of alkynes to conjugated bisallenes: a (C2 + C2 + C2)-protocol.
Scheme 18: Preparation of a TMS-substituted conjugated bisallene by a C3-dimerization route.
Scheme 19: A bis(trimethylsilyl)bisallene by a C3-coupling protocol.
Scheme 20: The rearrangement of highly substituted benzene derivatives into their conjugated bisallenic isomer...
Scheme 21: From fully substituted benzene derivatives to fully substituted bisallenes.
Scheme 22: From a bicyclopropenyl to a conjugated bisallene derivative.
Scheme 23: The conversion of a bismethylenecyclobutene into a conjugated bisallene.
Scheme 24: The preparation of monofunctionalized bisallenes.
Scheme 25: Preparation of bisallene diols and their cyclization to dihydrofurans.
Scheme 26: A 3,4-difunctionalized conjugated bisallene by a C3-coupling process.
Scheme 27: Preparation of a bisallenic diketone by a coupling reaction.
Scheme 28: Sulfur and selenium-substituted bisallenes by a [2.3]sigmatropic rearrangement.
Scheme 29: The biallenylation of azetidinones.
Scheme 30: The preparation of a fully ferrocenylated conjugated bisallene.
Scheme 31: The first isomerization of a 1,5-hexadiyne to a 1,2,4,5-hexatetraene.
Scheme 32: The preparation of alkynyl-substituted bisallenes by a C3-dimerization protocol.
Scheme 33: Preparation of another completely ferrocenylated bisallene.
Scheme 34: The cyclization of 1,5-hexadiyne (129) to 3,4-bismethylenecyclobutene (130) via 1,2,4,5-hexatetraen...
Scheme 35: Stereochemistry of the thermal cyclization of bisallenes to bismethylenecyclobutenes.
Scheme 36: Bisallene→bismethylenecyclobutene ring closures in the solid state.
Scheme 37: A bisallene cyclization/dimerization reaction.
Scheme 38: A selection of Diels–Alder additions of 1,2,4,5-hexatetraene with various double-bond dienophiles.
Scheme 39: The stereochemistry of the [2 + 4] cycloaddition to conjugated bisallenes.
Scheme 40: Preparation of azetidinone derivatives from conjugated bisallenes.
Scheme 41: Cycloaddition of heterodienophiles to a conjugated bisallene.
Scheme 42: Addition of triple-bond dienophiles to conjugated bisallenes.
Scheme 43: Sulfur dioxide addition to conjugated bisallenes.
Scheme 44: The addition of a germylene to a conjugated bisallene.
Scheme 45: Trapping of conjugated bisallenes with phosphinidenes.
Scheme 46: The cyclopropanantion of 1,2,4,5-hexatetraene (2).
Scheme 47: Photochemical reactions involving conjugated bisallenes.
Scheme 48: Base-catalyzed isomerizations of conjugated bisallenes.
Scheme 49: Ionic additions to a conjugated bisallene.
Scheme 50: Oxidation reactions of a conjugated bisallene.
Scheme 51: The mechanism of oxidation of the bisallene 24.
Scheme 52: CuCl-catalyzed cyclization of 1,2,4,5-hexatetraene (2).
Scheme 53: The conversion of conjugated bisallenes into cyclopentenones.
Scheme 54: Oligomerization of a conjugated bisallene by nickel catalysts.
Scheme 55: Generation of 1,2,5,6-heptatetraene (229) as a reaction intermediate.
Scheme 56: The preparation of a stable derivative of 1,2,5,6-heptatetraene.
Scheme 57: A bisallene with a carbonyl group as a spacer element.
Scheme 58: The first preparation of 1,2,6,7-octatetraene (242).
Scheme 59: Preparation of 1,2,6,7-octatetraenes by (C4 + C4)-coupling of enynes.
Scheme 60: Preparation of 1,2,6,7-octatetraenes by (C4 + C4)-coupling of homoallenyl bromides.
Scheme 61: Preparation of 1,2,6,7-octatetraenes by alkylation of propargylic substrates.
Scheme 62: Preparation of two highly functionalized 1,2,6,7-octatetraenes.
Scheme 63: Preparation of several higher α,ω-bisallenes.
Scheme 64: Preparation of different alkyl derivatives of α,ω-bisallenes.
Scheme 65: The preparation of functionalized 1,2,7,8-nonatetraene derivatives.
Scheme 66: Preparation of functionalized α,ω-bisallenes.
Scheme 67: The preparation of an α,ω-bisallene by direct homologation of an α,ω-bisalkyne.
Scheme 68: The gas-phase pyrolysis of 4,4-dimethyl-1,2,5,6-heptatetraene (237).
Scheme 69: Gas-phase pyrolysis of 1,2,6,7-octatetraene (242).
Scheme 70: The cyclopropanation of 1,2,6,7-octatetraene (242).
Scheme 71: Intramolecular cyclization of 1,2,6,7-octatetraene derivatives.
Scheme 72: The gas-phase pyrolysis of 1,2,7,8-nonatetraene (265) and 1,2,8,9-decatetraene (266).
Scheme 73: Rh-catalyzed cyclization of a functionalized 1,2,7,8-nonatetraene.
Scheme 74: A triple cyclization involving two different allenic substrates.
Scheme 75: Bicyclization of keto derivatives of 1,2,7,8-nonatetraene.
Scheme 76: The preparation of complex organic compounds from functionalized bisallenes.
Scheme 77: Cycloisomerization of an α,ω-bisallene containing a C9 tether.
Scheme 78: Organoborane polymers from α,ω-bisallenes.
Scheme 79: Preparation of trans- (337) and cis-1,2,4,6,7-octapentaene (341).
Scheme 80: The preparation of 4-methylene-1,2,5,6-heptatetraene (349).
Scheme 81: The preparation of acetylenic bisallenes.
Scheme 82: The preparation of derivatives of hydrocarbon 351.
Scheme 83: The construction of macrocyclic alleno-acetylenes.
Scheme 84: Preparation and reactions of 4,5-bismethylene-1,2,6,7-octatetraene (365).
Scheme 85: Preparation of 1,2-bis(propadienyl)benzene (370).
Scheme 86: The preparation of 1,4-bis(propadienyl)benzene (376).
Scheme 87: The preparation of aromatic and heteroaromatic bisallenes by metal-mediated coupling reactions.
Scheme 88: Double cyclization of an aromatic bisallene.
Scheme 89: Preparation of an allenic [15]paracyclophane by a ring-closing metathesis reaction of an aromatic α...
Scheme 90: Preparation of a macrocyclic ring system containing 1,4-bis(propadienyl)benzene units.
Scheme 91: Preparation of copolymers from 1,4-bis(propadienyl)benzene (376).
Scheme 92: A boration/copolymerization sequence of an aromatic bisallene and an aromatic bisacetylene.
Scheme 93: Formation of a layered aromatic bisallene.
Figure 4: The first members of the semicyclic bisallene series.
Scheme 94: Preparation of the first bis(vinylidene)cyclobutane derivative.
Scheme 95: Dimerization of strain-activated cumulenes to bis(vinylidene)cyclobutanes.
Scheme 96: Photodimerization of two fully substituted butatrienes in the solid state.
Scheme 97: Preparation of the two parent bis(vinylidene)cyclobutanes.
Scheme 98: The preparation of 1,3-bis(vinylidene)cyclopentane and its thermal isomerization.
Scheme 99: The preparation of the isomeric bis(vinylidene)cyclohexanes.
Scheme 100: Bi- and tricyclic conjugated bisallenes.
Scheme 101: A selection of polycyclic bisallenes.
Scheme 102: The first endocyclic bisallenes.
Figure 5: The stereochemistry of 1,2,6,7-cyclodecatetraene.
Scheme 103: The preparation of several endocyclic bisallenes.
Scheme 104: Synthesis of diastereomeric derivatives of 1,2,6,7-cyclodecatetraene.
Scheme 105: Preparation of a derivative of 1,2,8,9-cyclotetradecatetraene.
Scheme 106: The preparation of keto derivatives of cyclic bisallenes.
Scheme 107: The preparation of cyclic biscumulenic ring systems.
Scheme 108: Cyclic bisallenes in natural- and non-natural-product chemistry.
Scheme 109: The preparation of iron carbonyl complexes from cyclic bisallenes.
Figure 6: A selection of unknown exocyclic bisallenes that should have interesting chemical properties.
Scheme 110: The thermal isomerization of 1,2-diethynylcyclopropanes and -cyclobutanes.
Scheme 111: Intermediate generation of a cyclooctapentaene.
Scheme 112: Attempted preparation of a cyclodecahexaene.
Scheme 113: The thermal isomerization of 1,5,9-cyclododecatriyne (511) into [6]radialene (514).
Scheme 114: An isomerization involving a diketone derived from a conjugated bisallene.
Scheme 115: Typical reaction modes of heteroorganic bisallenes.
Scheme 116: Generation and thermal behavior of acyclic hetero-organic bisallenes.
Scheme 117: Generation of bis(propadienyl)thioether.
Scheme 118: The preparation of a bisallenic sulfone and its thermal isomerization.
Scheme 119: Bromination of the bisallenic sulfone 535.
Scheme 120: Metalation/hydrolysis of the bisallenic sulfone 535.
Scheme 121: Aromatic compounds from hetero bisallenes.
Scheme 122: Isomerization/cyclization of bispropargylic ethers.
Scheme 123: The preparation of novel aromatic systems by base-catalyzed isomerization of bispropargyl ethers.
Scheme 124: The isomerization of bisacetylenic thioethers to bicyclic thiophenes.
Scheme 125: Aromatization of macrocyclic bispropargylic sulfides.
Scheme 126: Preparation of ansa-compounds from macrocyclic bispropargyl thioethers.
Scheme 127: Alternate route for cyclization of a heterorganic bisallene.
Scheme 128: Multiple isomerization/cyclization of “double” bispropargylic thioethers.
Scheme 129: Preparation of a bisallenyl disulfide and its subsequent bicyclization.
Scheme 130: Thermal cyclization of a bisallenyl thiosulfonate.
Scheme 131: Some reactions of heteroorganic bisallenes with two sulfur atoms.
Scheme 132: Further methods for the preparation of heteroorganic bisallenes.
Scheme 133: Cyclization reactions of heteroorganic bisallenes.
Scheme 134: Thermal cycloadditions of bisallenic tertiary amines.
Scheme 135: Cyclization of a bisallenic tertiary amine in the presence of a transition-metal catalyst.
Scheme 136: A Pauson–Khand reaction of a bisallenic ether.
Scheme 137: Formation of a 2:1adduct from two allenic substrates.
Scheme 138: A ring-forming silastannylation of a bisallenic tertiary amine.
Scheme 139: A three-component cyclization involving a heterorganic bisallene.
Scheme 140: Atom-economic construction of a complex organic framework from a heterorganic α,ω-bisallene.
Triple-channel microreactor for biphasic gas–liquid reactions: Photosensitized oxygenations
- Ram Awatar Maurya,
- Chan Pil Park and
- Dong-Pyo Kim
Beilstein J. Org. Chem. 2011, 7, 1158–1163, doi:10.3762/bjoc.7.134
- oxygenations of α-terpinene, citronellol, and allyl alcohols. Keywords: gas–liquid reaction; microreactor; photosensitization; singlet oxygen; Introduction Microreactors have recently attracted much interest among the scientific community for performing laboratory operations on small scales [1][2][3][4][5][6
- from long reaction times due to restricted spatial illumination. In addition, the short lifetime of singlet oxygen in solutions, the low interfacial area between the oxygen and the reaction solution, and the long molecular diffusion distances significantly reduce the reaction efficiency. In this
Graphical Abstract
Figure 1: Schematic the for contacting modes of biphasic gas–liquid in (a) batch reactor, (b) dual-channel, a...
Figure 2: Optical image of the triple-channel microreactor (for demonstration purposes, the inner channel for...
Figure 3: Photosensitized oxygenation in the triple-channel microreactor.
Scheme 1: Photosensitized oxygenation of citronellol (a key step in the synthesis of rose oxide).
Fine-tuning alkyne cycloadditions: Insights into photochemistry responsible for the double-strand DNA cleavage via structural perturbations in diaryl alkyne conjugates
- Wang-Yong Yang,
- Samantha A. Marrone,
- Nalisha Minors,
- Diego A. R. Zorio and
- Igor V. Alabugin
Beilstein J. Org. Chem. 2011, 7, 813–823, doi:10.3762/bjoc.7.93
- acetamides. The significant protecting effect of the hydroxyl radical and singlet oxygen scavengers to DNA cleavage was shown only with m-lysine conjugate. All three isomeric lysine conjugates inhibited human melanoma cell growth under photoactivation: The p-conjugate had the lowest CC50 (50% cell
- previous mechanistic studies suggested that neither singlet oxygen nor diffusing oxygen- and carbon-centered radical species play a significant role under the conditions where the most efficient ds cleavage by monoalkynes is observed (pH 6) [25]. From the narrowed list of mechanistic scenarios, base
- on DNA cleavage In order to get further insight into the mechanism of the DNA cleavage by the three conjugates, we used the plasmid relaxation assays for the cleavage with conjugates 1, 6, and 7 in the presence of hydroxyl radicals (glycerol, DMSO) and singlet oxygen (NaN3) scavengers [65]. The
Graphical Abstract
Figure 1: Structure of C-lysine conjugates.
Figure 2: Alternative pathways of enediyne photoreactivity: photo-Bergman cyclization (left), C1–C5 cyclizati...
Figure 3: Summary of possible mechanistic alternatives for the observed DNA cleavage by monoacetylene conjuga...
Scheme 1: Proposed mechanism of photocycloaddition of acetylene with 1,4-CHD.
Figure 4: p-, m-, and o-amidyl acetylenes and respective lysine conjugates.
Scheme 2: Synthesis of amido-substituted monoacetylenes and lysine conjugates. Reagents and conditions: a. Pd...
Scheme 3: Photochemical reactions of TFP-substituted aryl alkynes with selected π-systems. In short, the reac...
Scheme 4: Photocycloaddition of amido acetylenes with 1,4-CHD.
Scheme 5: Possible mechanism for photochemical hydration of diaryl acetylene moiety catalyzed by the ortho-am...
Figure 5: Stern–Volmer plots of three regioisomers, 3 (blue diamond), 4 (red square), and 5 (green triangle),...
Figure 6: Absorption spectra of three isomers, 3, 4, 5, and Ph-TFP in acetonitrile (10 μM).
Figure 7: Quantified DNA cleavage data for 1 (a), 6 (b) and 7 (c). Blue: Form I (supercoiled) DNA; red: Form ...
Figure 8: Effect of hydroxyl radical/singlet oxygen scavengers (20 mM) on the efficiency of DNA cleavage at p...
Figure 9: Cell proliferation assay using A375 cells (human melanoma) and compound 1 (green square), 6 (red up...
Palladium-catalyzed formation of oxazolidinones from biscarbamates: a mechanistic study
- Benan Kilbas and
- Metin Balci
Beilstein J. Org. Chem. 2011, 7, 246–253, doi:10.3762/bjoc.7.33
- nucleophile is not necessary to form oxazolidinones. The metal is probably bonded to the allylic system from the same face as the nucleophile. Keywords: bicyclic endoperoxides; biscarbamates; oxazolidinone; Pd-catalyzed allylic reaction; singlet oxygen; Introduction Palladium-catalyzed carbon–carbon bond
- shift the equilibrium to the norcaradiene 4b side, while electron donating substituents, such as –OR, –NR2 favor the cycloheptatriene 4a structure. It has been shown that singlet oxygen and 4-phenyl-1,2,4-triazoline-3,5-dione (PTAD) are sufficiently reactive to intervene in the cycloheptatriene
Graphical Abstract
Scheme 1: General route to oxazolidinones via a palladium-catalyzed reaction.
Figure 1: Metal–olefin complexation from the anti-face of the double bond.
Figure 2: Cyclic systems with enantiotopic leaving groups at allylic positions.
Scheme 2: The cycloheptatriene–norcaradiene equilibrium.
Scheme 3: Synthesis of oxazolidinone 9 starting from carboxymethyl cycloheptatriene 5a.
Scheme 4: Attempted isomerization of 7 to 10.
Scheme 5: Synthesis of oxazolidinones 17 and 20.
Scheme 6: The mechanism for the formation of oxazolidinones [3].
Figure 3: Nucleophilic attack on the double bond from the leaving group's side.
Synthesis of spiroannulated and 3-arylated 1,2,4-trioxanes from mesitylol and methyl 4-hydroxytiglate by photooxygenation and peroxyacetalization
- Axel G. Griesbeck,
- Lars-Oliver Höinck and
- Jörg M. Neudörfl
Beilstein J. Org. Chem. 2010, 6, No. 61, doi:10.3762/bjoc.6.61
- -hydroperoxy homoallylic alcohols (prepared by the ene reaction of the allylic alcohols mesitylol and methyl 4-hydroxytiglate, respectively, with singlet oxygen) to give spiroannulated 1,2,4-trioxanes 5a–5e and 9a–9e, respectively. A second series of 3-arylated trioxanes 10a–10h, that are available from the
- hydroperoxy alcohol 4 and benzaldehyde derivatives, was investigated by X-ray crystallography. Keywords: ene reaction; peracetalization; peroxides; singlet oxygen; trioxanes; Introduction The antimalaria-active molecule artemisinin (1) is a naturally occurring sesquiterpene peroxide with remarkable
- singlet oxygen ene reaction of allylic alcohols as a route to ß-hydroperoxy alcohols that can be transformed into 1,2,4-trioxanes by reaction with carbonyl compounds in the presence of Lewis acids [11]. This approach leads to simple cyclic peroxides (e.g. 2) which in some cases show similar antimalarial
Graphical Abstract
Figure 1: Antimalaria active natural artemisinin 1 and the spirobicyclic 1,2,4-trioxane derivative 2 show the...
Scheme 1: Singlet oxygen ene reaction of methyl 4-hydroxytiglate (3) and mesitylol (6) under solid-phase cond...
Scheme 2: 1,2,4-trioxane 9c and bis-trioxane 8a,b formation from the bifunctional cyclohexa-1,4-dione.
Figure 2: Structure of the spirobicyclic trioxane 5c in the crystal.
Scheme 3: BF3-catalyzed acetalization of hydroperoxide 4 with benzaldehyde derivatives.
Figure 3: Structure of the 3-arylated trioxane 10b in the crystal.
Figure 4: Structure of the p-bromophenyl derivative 10d in the crystal lattice (disordered water molecules in...
Figure 5: Numbering of 3-aryl-1,2,4-trioxanes 10 and relevant bonds; structure of artemether (AM).
Synthesis of a new class of aminocyclitol analogues with the conduramine D-2 configuration
- Latif Kelebekli,
- Yunus Kara and
- Murat Celik
Beilstein J. Org. Chem. 2010, 6, No. 15, doi:10.3762/bjoc.6.15
- cyclooctatetraene (8) by the addition of mercury(II) acetate [31]. Tetraphenylporphyrin sensitized photooxygenation of diacetoxydiene 9 with singlet oxygen gave the expected endoperoxide 10. Reduction of the peroxide bond in 10 was performed with thiourea under very mild conditions to give the cis-diol 11 in 99
- -dichlorobicylooctadiene 19 with singlet oxygen gave the expected endoperoxide 20 [19][20][21] (Scheme 4). Since the dichlorobicyclooctadiene 19 has no plane of symmetry, singlet oxygen approaches the diene unit exclusively from the less crowded side of the molecule in accord with previous reports [20][21]. Reduction of
Graphical Abstract
Scheme 1: Synthesis of bis-carbamate 12 and oxazolidinone 13.
Scheme 2: Mechanism of the palladium-catalyzed ionization/cyclization reaction.
Scheme 3: Synthesis of aminocyclitol analogue 6.
Figure 1: The thermal ellipsoid plot of the single crystal X-ray crystallographic structure of 18.
Scheme 4: Synthesis of oxazolidone 23.
Scheme 5: Mechanism of the palladium-catalyzed ionization/cyclization reaction in dichloro biscarbamate 22.
Scheme 6: Synthesis of dichloroaminocyclitol 7.
Figure 2: 1H NMR NOE spectrum of compound 7.
Sordarin, an antifungal agent with a unique mode of action
- Huan Liang
Beilstein J. Org. Chem. 2008, 4, No. 31, doi:10.3762/bjoc.4.31
- al. [20]. The resultant alcohol was converted to the methyl ether using NaH and MeI. The subsequent Cope rearrangement of 10 occurred at 200 °C via a boat-like transition state [18] to yield 11. The elaboration of this material to 12 involved treatment with singlet oxygen and AcCl [21] to yield α,β
Graphical Abstract
Figure 1: Therapeutic antifungal agents.
Figure 2: Structure of sordarin (1) and sordaricin (2).
Scheme 1: Kato’s retrosynthetic plan.
Scheme 2: Synthesis of cyclopentadiene 13.
Scheme 3: Synthesis of sordaricin methyl ester.
Scheme 4: Mander’s retrosynthetic plan.
Scheme 5: Synthesis of iodo compound 27.
Scheme 6: Synthesis of sordaricin (2).
Scheme 7: Retrosynthesis of sordarin and sordaricin.
Scheme 8: Synthesis of ketone 43.
Scheme 9: Synthesis of β-keto ethyl ester 45.
Scheme 10: Synthesis of tetracyclic framework 52.
Scheme 11: Synthesis of sordaricin and sordarin.
Figure 3: Modifications of glycosyl part.
Scheme 12: Simplified model of sordarin.
Scheme 13: Synthesis of cyclopentane analog precursors.
Scheme 14: Synthesis of six cyclopentane analogs.
Scheme 15: Retrosynthetic plan of sordarin analog.
Scheme 16: Synthesis of sordarin analog 98.
Scheme 17: Synthesis of sordarin analog 103.
