- Continuous Flow Magnesiation or Zincation of Acrylonitriles, Acrylates, and Nitroolefins. Application to the Synthesis of Butenolides
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Scalable continuous flow procedures are reported for the metalation and downstream functionalization of β-substituted acrylates. The flow conditions allow the metalation of acrylonitriles, acrylates, and nitroolefins at 0.25-2.50 mmol/min conversion rates. Magnesiations can be performed with short residence times (1-20 min) and near-ambient temperature using TMPMgCl·LiCl. Further, high temperature zincation (≤90°C) using TMPZnCl·LiCl is possible. This method allows a simple entry to 2(5H)-furanones by flow generation of magnesiated acrylates and a subsequent reaction with aldehydes. (Chemical Equation Presented).
- Ganiek, Maximilian A.,Becker, Matthias R.,Ketels, Marthe,Knochel, Paul
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- Rhodium(I)-Catalyzed CO-Gas-Free Arylative Dual-Carbonylation of Alkynes with Arylboronic Acids via the Formyl C-H Activation of Formaldehyde
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The rhodium(I)-catalyzed reaction of alkynes with aryl boronic acids in the presence of formaldehyde results in a CO-gas-free arylative dual-carbonylation to produce γ-butenolide derivatives. The simultaneous loading of phosphine-ligated and phosphine-free rhodium(I) complexes is required for efficient catalysis. The former complex catalyzes the abstraction of a carbonyl moiety from formaldehyde through the activation of its formyl C-H bond (decarbonylation) and the latter catalyzes the subsequent dual-incorporation of the resulting carbonyl unit (carbonylation). The use of larger amounts of the phosphine-ligated rhodium(I) complex generates more carbonyl units, leading to the formation γ-butenolides via the dual-incorporation of the carbonyl unit.
- Morimoto, Tsumoru,Wang, Chuang,Tanimoto, Hiroki,Artok, Levent,Kakiuchi, Kiyomi
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p. 3372 - 3382
(2021/05/04)
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- Titanium-Promoted Cross-Coupling for the Selective Synthesis of Polysubstituted, Conjugated Amides
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α,β-Unsaturated amides are important building blocks and are key structural elements in a number of biologically active natural products. Despite their importance and prevalence, few methods exist to prepare conjugated amides directly and modularly. To address this gap, a titanium-promoted coupling of alkynes and isocyanates has been developed. The method is highly stereoselective, producing only the E isomer with good chemoselectivity and regioselectivity (>95/5), for unsymmetrical internal alkynes that contain a steric bias. The reactive titanacyclopentene intermediate formed from the coupling of the alkyne and isocyanate was additionally reacted with various electrophiles to access tetrasubstituted enamides.
- Chenniappan, Vinoth Kumar,Rahaim, Ronald J.
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supporting information
p. 5090 - 5093
(2016/10/14)
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- Intermolecular [2+2+1] Carbonylative Cycloaddition of Aldehydes with Alkynes, and Subsequent Oxidation to γ-Hydroxybutenolides by a Supported Ruthenium Catalyst
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Intermolecular [2+2+1] carbonylative cycloaddition of aldehydes with alkynes and subsequent oxidation to γ-hydroxybutenolides is achieved using a supported ruthenium catalyst. A ceria-supported ruthenium catalyst promotes the reaction efficiently, even with an ambient pressure of CO or without external CO, thus giving the corresponding γ-hydroxybutenolide derivatives in good to high yields. Moreover this catalyst can be reused with no loss of activity.
- Miura, Hiroki,Takeuchi, Kazuki,Shishido, Tetsuya
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supporting information
p. 278 - 282
(2016/01/25)
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- Nickel(0)-catalyzed formation of oxaaluminacyclopentenes via an oxanickelacyclopentene key intermediate: Me2AlOTf-assisted oxidative cyclization of an aldehyde and an alkyne with nickel(0)
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The use of Me2AlOTf as an additive allowed the oxidative cyclization of pivalaldehyde and diphenylacetylene with nickel(0) in the presence of PCy3 to give an oxanickelacyclopentene, the structure of which was unambiguously determined
- Ohashi, Masato,Saijo, Hiroki,Arai, Tomoya,Ogoshi, Sensuke
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experimental part
p. 6534 - 6540
(2011/02/17)
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- Rhodium catalyzed reaction of internal alkynes with organoborons under CO atmosphere: a product tunable reaction
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Alkynes react with organoborons under a CO atmosphere in the presence of a rhodium(I) catalyst to afford mainly 5-aryl-2(5H)-furanones, α,β-unsaturated ketones, and indanones. The product selectivity can be tuned by modifying the reaction conditions.
- Artok, Levent,Ku?, Melih,Aksin-Artok, ?zge,Dege, Fatma Nurcan,?zkilin?, Fatma Yelda
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scheme or table
p. 9125 - 9133
(2010/01/16)
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- Synthesis of α,β-unsaturated ketones by rhodium-catalyzed carbonylative arylation of internal alkynes with arylboronic acids
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The Rh-catalyzed reaction of arylboronic acids with internal alkynes under a CO atmosphere in the presence of an acid additive afforded α,β-unsaturated ketones as the major products. Hydroacylation of internal alkynes, except in the case of diaryl acetylenes, proceeded in syn fashion, yielding the E-configured isomer. A mixture of E- and Z-isomers was obtained with diphenyl acetylene. Reactions were also highly regioselective for various nonsymmetric alkynes.
- Ku?, Melih,Artok, ?zge Aksin,Ziyanak, Firat,Artok, Levent
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experimental part
p. 2587 - 2592
(2009/04/16)
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- Rhodium-catalyzed carbonylative arylation of alkynes with arylboronic acids: An efficient and straightforward method in the synthesis of 5-aryl-2(5H)-furanones
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5-Aryl-2(5H)-furanones can be synthesized by the Rh-catalyzed reactions of arylboronic acids with internal alkynes under a CO atmosphere. The Royal Society of Chemistry 2006.
- Aksin, Oezge,Dege, Nurcan,Artok, Levent,Tuerkmen, Hayati,Cetinkaya, Bekir
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p. 3187 - 3189
(2008/09/19)
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- Acylpalladation of internal alkynes and palladium-catalyzed carbonylation of (Z)-β-iodoenones and related derivatives producing γ-lactones and γ-lactams
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The reaction of either an internal alkyne-organic halide mixture or (Z)-β-iodoenones with CO in the presence of a Pd-phosphine catalyst, e.g., Cl2Pd(PPh3)2, can give one of the three discrete types of compounds as the major products depending on the substrate structure and the reaction conditions. Those substrates which are convertible to (Z)-γ-oxo-α,β-unsaturated acylpalladium derivatives lacking δ-H atoms are converted to the corresponding 2-butenolides (13) in the presence of water, which serves as a H donor. Carbon monoxide most likely is the source of two electrons. Either in the absence of water (or any other suitable H source) or in the presence of some factors disfavoring the butenolide formation, the same reaction gives the corresponding dimeric product (16). Even in cases where there is an α-H atom in the α-substitutent, 1,4-elimination products (11), reported to be the major products in a related Pd-catalyzed reaction of terminal alkyne-aryl iodide mixtures with CO, were not detected. In sharp contrast, those substrates which can give rise to (Z)-γ-oxo-α,β-unsaturated acylpalladium derivatives containing δ-H atoms give, under comparable reaction conditions, enol lactones (12), i.e., (Z)-3-alkylidene-2-butenolides, contaminated with only very minor amounts of 22 even in cases where an excess (4 equiv) of water was present. The required (Z)-β-iodoenones can be readily prepared in one pot via ZrCp2-promoted cyclization of alkynes with nitriles. The ready availability of the starting compounds and the high Z stereoselectivity make the overall sequence an attractive synthetic route to 12. The courses of the Pd-catalyzed carbonylation reactions of (Z)-β-iodo-α,β-unsaturated imines 23 closely parallel the reactions of enones and produce the corresponding lactams, i.e., 24 and 25.
- Copéret, Christophe,Sugihara, Takumichi,Wu, Guangzhong,Shimoyama, Izumi,Negishi, Ei-Ichi
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p. 3422 - 3431
(2007/10/02)
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- Substituent Effects in the Photochemistry of 5-Aryl-3,3-diphenyl-2(3H)-furanones. Steady-State and Laser Flash Photolysis Studies
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The photochemistry of a series of 5-aryl-3,3-diphenyl-2(3H)-furanones, containing electron-releasing as well as electron-withdrawing para substituents on the phenyl group at theC5 position, has been investigated by steady-state photolysis, prod
- Pratapan, S.,Ashok, K.,Cyr, D.R.,Das, P.K.,George, M.V.
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p. 5826 - 5831
(2007/10/02)
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- Sensitized Photorearrangement of 3,3,5-Triaryl-2(3H)-furanones to 3,4,5-Triaryl-2(5H)-furanones. Steady-State and Laser Flash Photolysis Investigations
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A novel photorearrangement of 3,3,5-triaryl-2(3H)-furanones 1a-e under acetone or acetophenone sesitization is reported.Sensitized irradiation of 1-a-e in benzene gave a mixture of the photorearranged 2(5H)-furanones 3 and 4, along with the corresponding
- Gopidas, K.R.,Lohray, B.B.,Rajadurai, S.,Das, P.K.,George, M.V.
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p. 2831 - 2838
(2007/10/02)
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- Electron Transfer Reactions. Reaction of Furanones and Bifurandiones with Potassium and Oxygen
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Treatment of furanones (1a - c, 25, 34) and bifurandiones (23, 37) with potassium in THF gave rise to radical anion intermediates, which reacted with oxygen to give superoxide and ultimately products derived through the reaction of superoxide with the starting furanones and bifurandiones.Thus, the reaction of 1a with potassium gave a mixture of 4-oxo-2,2,4-triphenylbutanoic acid (7a), 1,3,3-triphenyl-2-propen-1-one (11a), and benzoic acid (12).The reaction of 11a itself, under similar conditions, gave a mixture of benzophenone (18a) and 12.Similar reactions have been observed in the case of 1b and c.The bifurandione 23, on treatment with potassium, gave a mixture of the 2(5H)-furanone 25, 2,3-diphenylpropenoic acid (31), and 12.The reaction of 25 itself with potassium under similar conditions gave the same mixture of 31 and 12.Treatment of 3-phenyl-2(3H)-benzofuranone (34) with potassium, however, did not give any isolable product; only the starting material could be recovered.Under similar conditions, the bifurandione 37 gave the fragmentation product 34.Cyclic voltammetric studies have been employed to measure the reduction potentials, leading to radical anions, and these intermediates have been characterized through their electronic spectra.
- Pandey, Bipin,Tikare, Ravindra K.,Muneer, Mohammed,Kamat, Prashant V.,George, Manapurathu V.
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p. 917 - 928
(2007/10/02)
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- Photochemical and Thermal Transformations of 2(3H)-Furanones and Bis(benzofuranones). A Laser Flash Photolysis study
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Transformations of the 2(3H)-furanones 1-4 and bis(benzofuranones) 16-18 under steady-state photolysis and thermolysis are reported.Irradiation of 1 in benzene gives a mixture of the decarbonylated product 5 (62percent) and the cyclized phenanthrene derivative 10 (15percent).Similar results were obtained when the photolysis of 1 was carried out in methanol and acetone.Irradiation of 2 in benzene and methanol gave exclusively the decarbonylation product 6, whereas, in acetone, a mixture of the rearranged lactone 13 and and its cyclized product, 15, was obtained.Irradiation of both 3 and 4 gave the cyclized products 11 and 12, respectively.In contrast, the photolysis of the bis(benzofuranone) 16 in cyclohexane gave 3-phenylbenzo-2-(3H)-furanone (25), whereas the photolysis in methanol led to a mixture of methyl α-(2-hydroxyphenyl)phenylacetate (34) and 3-hydroxy-3-phenylbenzo-2(3H)-furanone (31).Similar results were obtained in the irradiation of 17 and 18.Neat thermolysis of furanones 1-3 at 350-450 deg C gave the decarbonylated products 5, 6, and 37 in 36-80 percent yields, whereas furanone 4 underwent facile isomerization to 5-benzyl-3,4,5-triphenyl-2(5H)-furanone (38), upon refluxing in diphenyl ether (ca. 255 deg C).Heating of bis(benzofuranones) 16-18 in refluxing cumene (ca. 150 deg C) gave the corresponding furanones 25-27 in 62-68 percent yields.Laser flash photolysis of furanones 1-4 at 248 and 337 nm leads to absorption spectral changes that can be explained in terms of singlet-mediated decarbonylation (φ = 0.3 for 2 in methanol, λex = 248 nm) and cyclization, i.e., dihydrophenanthrene formation (φ = 0.1-0.5 for 1, 3, and 4 in benzene and methanol, λex = 337 nm).The triplets of the furanones generated under energy-transfer sensitization by benzophenone in benzene are relatively long lived (r = 1.2-12 μs) and exhibit absorption maxima at 330-370 nm (εmax = (11-14) * 103 M-1 cm-1); these spectral and kinetic features appear to be characteristic of the styrene and cis-stilbene chromophores, constrained into planar configurations.Upon laser flash photolysis at 248 nm in methanol, bis(benzofuranones) 16-18 undergo facile fragmentation to the corresponding radicals 19-21, characterized by sharp and intense absorption maxima at ca. 330 nm, in addition to broad and weak absorption band systems at 500-600 nm; these radical species are the primary intermediates implicated in the formation of various final products in the course of steady-state photolysis of 16-18 under different conditions.
- Lohray, B. B.,Kumar, C. V.,Das, P. K.,George, M. V.
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p. 7352 - 7359
(2007/10/02)
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- Photochemistry of Cyclopropene Derivatives. Synthesis and Photorearrangement of a 3-Acyl-Substituted Cyclopropene
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Two different approaches toward the synthesis of a 3-acyl-substituted 1,2,3-triphenylcyclopropene were investigated.The first involved treating triphenylcyclopropenyl perchlorate with the anion derived from 1,3-dithiane followed by hydrolysis of the resulting dithioacetal.Unfortunately, all attempts to obtain a carbonyl compound from the hydrolysis failed.The only product obtained corresponded to a 1,2-diphenyl-1,2-diacyl-substituted alkene.The second approach utilized for the synthesis involved treating 3-cyano-1,2,3-triphenylcyclopropene with methyllithium.The addition proceeded quite smoothly to give the desired 3-acetyl derivative in high yield.Irradiation of 1,2,3-triphenyl-3-acetylcyclopropene in benzene afforded a mixture of 2,3,4-triphenyl-2-cyclopentenone (60percent), 2-methyl-3,4,5-triphenylfuran (27percent), and 3-acetyl-1,2-diphenylindene (13percent).The formation of the three products obtained can be rationalized in terms of a vinylcarbene intermediate.Several different pathways are available to this species, depending on the stereochemistry about the double bond and on the conformation the oxygen atom assumes in the cis intermediate.The formation of the 2-cyclopentenone derivative provides good support for the mechanism proposed some years ago to rationalize the photochemical rearrangement of 2,5-dimethylfuran.
- Padwa, Albert,Akiba, Mitsuo,Chou, Chuen S.,Cohen, Leslie
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p. 183 - 191
(2007/10/02)
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