- Comparison of the photocatalytic activity of novel hybrid photocatalysts based on phthalocyanines, subphthalocyanines and porphyrins immobilized onto nanoporous gold
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A series of different singlet oxygen photosensitizers was immobilized onto nanoporous gold powder with a mean pore size of 40 nmviacopper catalyzed azide-alkyne cycloaddition. The attachment of phthalocyanine and porphyrin derivatives was performed on the peripheral substituent of the macrocycle, whereas the subphthalocyanine derivatives were attachedviathe axial substituent with respect to the macrocyclic ring system. All obtained hybrid systems were studied in the photooxidation of 2,5-diphenylfuran as a chemical singlet oxygen quencher and showed increased photocatalytic activity compared to the same amount of the corresponding photosensitizer in solution due to photoinduced interactions of the plasmon resonance of the nanostructured gold support and the attached photosensitizer. The understanding of the different photophysical interactions depending on the coordination mode of the macrocycle as well as the position of the absorbance in the electromagnetic spectrum is an important point in the development towards highly active hybrid photocatalysts covering a broad absorption range within the spectrum of visible light.
- Steinebrunner, David,Schnurpfeil, Günter,Thayssen, Jan,Tapia Burgos, Jorge Adrian,Wichmann, Andre,W?hrle, Dieter,Wittstock, Arne
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- Reaction of nitrous oxide with cyclopentadienyl complexes of cobalt, rhodium, and titanium
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The reaction of nitrous oxide with some cyclopentadienyl compounds of cobalt, rhodium, and titanium was studied. The corresponding furans were obtained in low to moderate yields.
- Leont'ev,Fomicheva,Proskurnina,Zefirov
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- Rh(III)-Catalyzed Cascade Reactions of Sulfoxonium Ylides with α-Diazocarbonyl Compounds: An Access to Highly Functionalized Naphthalenones
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An unprecedented cascade reaction of benzoyl sulfoxonium ylides with α-diazocarbonyl compounds leading to the formation of highly functionalized naphthalenones containing a β-ketosulfoxonium ylide moiety is presented. Promisingly, the naphthalenone derivative thus obtained was found to be a versatile intermediate toward diversely functionalized naphthalene derivatives including substituted 1-naphthol, 2-hydroxynaphthalen-1(2H)-one, naphthalen-1,2-dione, and 2-(methylsulfinyl)naphthalen-1-ol.
- Chen, Xi,Wang, Muhua,Zhang, Xinying,Fan, Xuesen
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Read Online
- Facile Synthesis of Enantiopure Sugar Alcohols: Asymmetric Hydrogenation and Dynamic Kinetic Resolution Combined
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An unprecedented Ir/f-amphox-catalyzed asymmetric hydrogenation of racemic 2,3-syn-dihydroxy-1,4-diones is presented involving dynamic kinetic resolution, which produces (1R,2R,3R,4R)-tetraols. This protocol constitutes an efficient and straightforward approach to accessing sugar alcohols bearing four contiguous stereocenters. The strategy exhibits various advantages over existing methods, including excellent yields (up to 98 %), exceptional stereoselectivities (up to 99:1 dr, 99.9 % ee), operational simplicity and substrate generality. Moreover, the nature of the reaction was revealed as a stepwise transformation by in situ Fourier-transform infrared spectroscopy and isolation of intermediates.
- Lin, Xin,Ma, Baode,Shao, Pan-Lin,Wang, Jiang,Wen, Jialin,Zhang, Xumu
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supporting information
p. 18166 - 18171
(2020/08/21)
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- Rhodium-Catalyzed 1,1-Hydroacylation of Thioacyl Carbenes with Alkynyl Aldehydes and Subsequent Cyclization
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A rhodium-catalyzed 1,1-hydroacylation of thioacyl carbenes with alkynyl and alkenyl aldehydes and subsequent 6-endo-trig/dig cyclization are realized, giving structurally diverse 4H-thiopyran-4-ones and 2,3-dihydro-4H-thiopyran-4-ones in moderate to good yields. The oxidative addition of Rh(I) to aldehydes is proposed to be the turnover-limiting step. Manipulations of estrones demonstrate the applications of our formal (3 + 3) transannulations in the structural modifications of natural products.
- Zhou, Bingnan,Wu, Qiuyue,Dong, Ziyang,Xu, Jiaxi,Yang, Zhanhui
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supporting information
p. 3594 - 3599
(2019/05/24)
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- Unusual reactions of diazocarbonyl compounds with α,β-unsaturated δ-amino esters: Rh(II)-catalyzed Wolff rearrangement and oxidative cleavage of N-H-insertion products
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Rh(II)-catalyzed reactions of aroyldiazomethanes, diazoketoesters and diazodiketones with α,β-unsaturated δ-aminoesters, in contrast to reactions of diazomalonates and other diazoesters, give rise to the Wolff rearrangement and/or oxidative cleavage of the initially formed N-H-insertion products. These oxidation processes are mediated by Rh(II) catalysts possessing perfluorinated ligands. The formation of pyrrolidine structures, characteristic for catalytic reactions of diazoesters, was not observed in these processes at all.
- Nikolaev, Valerij A.,Medvedev, Jury J.,Galkina, Olesia S.,Azarova, Ksenia V.,Schneider, Christoph
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supporting information
p. 1904 - 1910
(2016/10/05)
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- Copper-Catalyzed Cross-Coupling of Allylboronic Acids with α-Diazoketones
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Copper-catalyzed cross-coupling of substituted allylboronic acids with α-diazoketones was studied. This allylation reaction is highly regioselective, providing the branched allylic product. The process involves creation of a new C(sp3)-C(sp3) bond by retaining the keto functional group of the α-diazoketone precursor.
- Das, Arindam,Wang, Dong,Belhomme, Marie-Charlotte,Szabó, Kálmán J.
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p. 4754 - 4757
(2015/10/12)
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- Successively recycle waste as catalyst: A one-pot wittig/1,4-reduction/paal-knorr sequence for modular synthesis of substituted furans
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A one-pot tandem Wittig/conjugate reduction/Paal-Knorr reaction is reported for the synthesis of di- or trisubstituted furans. This novel sequence first demonstrates the possibility of successively recycling waste from upstream steps to catalyze downstream reactions.
- Chen, Long,Du, Yi,Zeng, Xing-Ping,Shi, Tao-Da,Zhou, Feng,Zhou, Jian
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p. 1557 - 1560
(2015/03/30)
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- Asymmetric organocatalytic aza-michael reactions of isatin derivatives
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Isatin was activated by derivatization to a Schiff base with aniline and used as an aza-Michael donor in organocatalytic asymmetric reactions with symmetric and nonsymmetric unsaturated 1,4-diketones. After hydrolysis (in situ), the N-substituted isatins were obtained in high yields (up to >95%) with high enantioselectivity (up to 95%).
- ?ari, Sergei,Metsala, Andrus,Kudrjashova, Marina,Kaabel, Sandra,J?rving, Ivar,Kanger, T?nis
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p. 875 - 886
(2015/03/14)
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- Elemental reductants for the deoxydehydration of glycols
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The elements zinc, iron, manganese, and carbon are demonstrated to be practical reductants for the oxorhenium catalyzed deoxydehydration (DODH) of biomass model polyols. These reductants and their oxidization products remain heterogeneous throughout the reaction, which aids in their separation. Their effectiveness is shown with the catalysts ammonium perrhenate and trans-[(Py)4Re(O)2]+Z- (1). Stoichiometric experiments with the Re(V) complex indicate a likely rhenium 5?7 oxidation cycle for the deoxydehydration of polyols reported herein.
- Michael McClain,Nicholas, Kenneth M.
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p. 2109 - 2112
(2014/07/21)
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- Facile selective synthesis of new furo[3,4-d[-1,3-thiazoles
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In presence of triethylamine, the reaction of substituted 2-aroyl-hydrazinecarbothioamides with 1,4-Diphenyl-but-2-yne-1,4-dione afforded novel furo[3,4-d]-1,3-thiazoles in good yield. The reaction mechanism suggests that the second molecule of 1,4-Diphen
- Aly, Ashraf A.,Hassan, Alaa A.,Al-Qalawi, Husam R.M.,Ishak, Esam A.
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p. 419 - 426
(2012/10/29)
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- Intermolecular asymmetric cyclopropanation with diazoketones catalyzed by chiral ruthenium porphyrins
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The asymmetric addition of diazoacetophenone to styrene derivatives to give optically active cyclopropyl ketones (ee up to 86%) was carried out by using chiral ruthenium porphyrins as homogeneous catalysts.
- Nicolas, Irène,Maux, Paul Le,Simonneaux, Gérard
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p. 2111 - 2113
(2008/09/17)
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- Diazo decomposition in the presence of tributyltin hydride. Reduction of α-diazo carbonyl compounds
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The diazo group of a series of α-diazo carbonyl compounds can be reduced to the corresponding CH2 group by Bu3SnH under Cu(acac)2-catalytic or photochemical conditions. The mechanistic aspects of this reaction were investigated in some detail, and a possible reaction pathway was discussed. (C) 2000 Elsevier Science Ltd.
- Tan, Zhongping,Qu, Zhaohui,Chen, Bei,Wang, Jianbo
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p. 7457 - 7461
(2007/10/03)
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- The reactions of diazo compounds with lactones. Part 1. Cyclopropanespiro-β-lactones from diketene: Synthesis and reactions
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The cyclopropanespiro-β-lactones 3, 4 and 12 can be prepared by the metal catalysed, or photochemically promoted decomposition reactions of diazocompounds in the presence of diketene. The thermal reactions of these compounds give a variety of products depending on the nature of the spirolactone; these include a furan 9a, 1,4-dicarbonyl compounds 18a-c and 19b, a pyranone 20b, furanones 21a, 21f and 22a and the enol 16. The boron trifluoride promoted reaction of a mixture of 3b and 4b gives a 13-ketoacid. Mechanisms are proposed for the formation of these products. The rearrangment of the cyclopropanespiro-β-lactones to furan-2(5H)-ones and furan-2-(3H)-ones 6-8, 21a, 21f, 22a and 24 is shown to be a general reaction that involves metal catalysis. A mechanism based on formation of a metallocycle by a novel insertion of the metal into the C-O bond of the β-lactone ring is proposed for this rearrangement. This accounts for the observed features of the reaction.
- Murphy, Paul V.,O'Sullivan, Timothy J.,Geraghty, Niall W.A.
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p. 2109 - 2119
(2007/10/03)
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- Reactions of α-Diazoketones with Olefinic Compounds in Presence of Catalysts and Related Studies
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A relatively stable cyclopropane adduct is produced by trapping ketocarbenes in olefin.The reactivities of ketocarbenes prepared thermally from different α-diazoketones and of the olefin substrates, and the effect of different catalysts and solvents are some of the parameters which have a pronounced effect on the yield of the products.Besides the cyclopropane adducts some side products have also been isolated and characterized.
- Podder, Ranjan Kumar,Sarkar, Tarani Kanta,Sarkar, Ranjit Kumar,Ray, Suvas C.
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p. 217 - 224
(2007/10/02)
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- Studies on the Oxidative Cleavage of the CC Triple Bond during the Autoxidation of Acetylenic Hydrocarbons. II. Studies Concerning the Reaction of Ketocarbenes with Molecular Oxygen
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α-Diazoacetophenone, α-diazopropiophenone, α-diazobutyrophenone and α-diazodesoxybenzoin were thermally and photochemically decomposed in the presence and in the absence of oxygen using benzene, cyclohexane and chlorobenzene as solvents.The products expected from the reaction of the short-lived intermediate ketocarbenes with oxygen (α-diketones and lower carboxylic acids, especially benzoic acid) could not be detected.No substantial difference was found between the composition of the reaction mixtures formed in the presence and absence of oxygen.The results show that the oxidative cleavage of the CC triple bond during the autoxidation of acetylenic hydrocarbons does not proceed via the corresponding oxirenes or the valence-isomeric ketocarbenes.
- Rao, T. S. S.,Pritzkow, W.
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p. 617 - 625
(2007/10/02)
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- Cyclopropanation of α,β-Unsaturated Carbonyl Compounds and Nitriles with Diazo Compounds. The nature of the Involvement of Transition-Metal Promoters
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In the presence of molybdenum hexacarbonyl or molybdenum(II) acetate, ethyl diazoacetate and α-diazoacetophenone react with α,β-unsaturated carbonyl compounds and nitriles to form derivative cyclopropane and vinyl CH insertion products.In the absence of these promoters or in the presence of catalytic amounts of pyridine, 2-pyrazolines are the major or sole reaction products.Kinetic investigations for reactions between ethyl diazoacetate and α,β-unsaturated esters and nitriles in the presence of Mo(CO)6, Mo2(OAc)4, or pyridine demonstrate the absence of any significant influence by these molybdenum promoters or pyridine on the rates and activation parameters for ethyl diazoacetate decomposition.Representative 1-pyrazolines have been synthesized and observed to undergo dinitrogen extrusion without apparent influence by molybdenum promoters.The composite results suggest that these molybdenum promoted reactions occur by dipolar cycloaddition of diazocarbonyl compounds to α,β-unsaturated systems and that the derivative 1-pyrazoline intermediates undergo dinitrogen extrusion to form the observed cyclopropane and vinyl CH insertion products.Molybdenum promoters function to inhibit competitive tautomerization of the initially formed cycloaddition products.The relative effectiveness of a broad selection of transition-metal compounds in directing reactions between ethyl diazoacetate and α,β-unsaturated esters and nitriles to cyclopropane products is described.The cycloaddition / dinitrogen extrusion pathway is presented as a viable mechanism for cyclopropanation of α,β-unsaturated systems by diazo compounds, even for reactions performed in the presence of traditional cyclopropanation catalysts.
- Doyle, Michael P.,Dorow, Roberta L.,Tamblyn, William H.
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p. 4059 - 4068
(2007/10/02)
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- Photosensitized Electron-transfer Reactions of Phenylacetylene
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Phenylacetylene (A) reacts with excited sensitizers (S) to produce radical ions (S).-, (A).+, which react as geminate or separated pairs with (A) to give a dimeric radical cation (A+-.A);the latter reacts with nitriles to give pyridines (1) or with nitromethane leading to an oxidation product (2) and a dimer (1-phenylnaphthalene) is also formed via the geminate pair.
- Mattes, Susan L.,Farid, Samir
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p. 126 - 128
(2007/10/02)
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- Molybdenum Hexacarbonyl Catalyzed Cyclopropanation of α,β-Unsaturated Esters and Nitriles with Diazocarbonyl Compounds
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Molybdenum hexacarbonyl, when employed in catalytic amounts, effectively promotes cyclopropanation of acrylonitrile, methacrylonitrile, and ethyl acrylate by ethyl diazoacetate and α-diazoacetophenone; the intermediacy of molybdenum carbene species in the formation of cyclopropane derivatives is suggested.
- Doyle, Michael P.,Davidson, James G.
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p. 1538 - 1539
(2007/10/02)
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