- Continuous Electrochemical Synthesis of Iso-Coumarin Derivatives from o-(1-Alkynyl) Benzoates under Metal- and Oxidant-Free
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A non-oxidant and metal-free strategy for synthesizing iso-coumarin by using a continuous electrochemical microreactor to initiate an oxidative cyclization reaction of o-(1-alkynyl) benzoate and radicals. This efficient and clean continuous electrosynthesis method not only avoids the complicated gas protection operation and production of by-products in the batch processes, but also help to overcome the difficulty that batch metal catalysis and electrocatalysis are difficult to scale up, and has the potential for pilot-scale experiment.
- Lin, Xinxin,Fang, Zheng,Zeng, Cuilian,Zhu, Chenlong,Pang, Xinyan,Liu, Chengkou,He, Wei,Duan, Jindian,Qin, Ning,Guo, Kai
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supporting information
p. 13738 - 13742
(2020/10/02)
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- p-TSA-Based DESs as “Active Green Solvents” for Microwave Enhanced Cyclization of 2-Alkynyl-(hetero)-arylcarboxylates: an Alternative Access to 6-Substituted 3,4-Fused 2-Pyranones
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In this paper, we describe the use of p-TSA based Deep Eutectic Solvents (DESs) as alternative environmental-friendly “active” solvents for the microwave-mediated synthesis of 6-substituted 3,4-fused 2-pyranones, and in particular isocoumarins, starting from 2-alkynyl-(hetero)arylcarboxylates. When the alkyne terminus bears a neutral or an electron-donating group (EDG), the reactions are fast, clean and highly regioselective, to give the 6-endo-dig cyclization products in good to excellent yields. For substrates bearing an electron-withdrawing group (EWG) on the alkyne end, the regioselectivity can be tuned by adding a small amount of silver(I) triflate as co-catalyst. DES was demonstrated to be reusable without loss of efficiency in terms of reaction yields. Based on experimental evidence and previous findings, two competitive mechanisms working simultaneously are proposed to explain the outcomes and the regioselectivity issues.
- Curti, Fabiola,Tiecco, Matteo,Pirovano, Valentina,Germani, Raimondo,Caselli, Alessandro,Rossi, Elisabetta,Abbiati, Giorgio
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p. 1904 - 1914
(2019/02/26)
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- Metal-Free Synthesis of 4-Chloroisocoumarins by TMSCl-Catalyzed NCS-Induced Chlorinative Annulation of 2-Alkynylaryloate Esters
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4-Chloroisocoumarins can be conveniently prepared from 2-alkynylaryloate esters via the activation of alkynes by electrophilic chlorine, generated in situ from N-chlorosuccinimide (NCS) in the presence of 10 mol % trimethylsilyl chloride (TMSCl), which leads to 6-endo-dig-selective chlorinative annulation to give the desired products in moderate to quantitative yields. The procedure employs readily available reagents and can be conveniently carried out on a wide scope of substrates under mild conditions (0 °C to rt). Furthermore, the reaction is scalable for gram-scale preparation of 4-chloroisocoumarins. Additionally, 4-bromo- and 4-iodoisocoumarins can be prepared in moderate to good yields by replacing NCS with N-bromosuccinimide (NBS) and N-iodosuccinimide (NIS), respectively.
- Norseeda, Krissada,Chaisan, Nattawadee,Thongsornkleeb, Charnsak,Tummatorn, Jumreang,Ruchirawat, Somsak
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p. 16222 - 16236
(2019/12/25)
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- Silver triflate/: P -TSA co-catalysed synthesis of 3-substituted isocoumarins from 2-alkynylbenzoates
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In this paper, we describe the silver triflate/p-toluenesulfonic acid co-catalysed synthesis of seventeen isocoumarins and two thieno[2,3-c]pyran-7-ones starting from 2-alkynylbenzoates and 3-alkynylthiophene-2-carboxylates, respectively. The reaction proceeds with absolute regioselectivity under mild reaction conditions and low catalyst loading, to afford the desired products in good to excellent yields. A conceivable reaction mechanism is proposed and supported by isotope-exchange tests, 1H NMR studies and ad hoc experiments.
- Gianni, Jonathan,Pirovano, Valentina,Abbiati, Giorgio
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supporting information
p. 3213 - 3219
(2018/05/17)
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- Divergent Syntheses of (Z)-3-Alkylideneisobenzofuran-1(3 H)-ones and 1 H-Isochromen-1-ones by Copper-Catalyzed Cycloisomerization of 2-Alkynylbenzoic Acids in Ionic Liquids
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The cycloisomerization of readily available 2-alkynylbenzoic acids 1 in ionic liquids (ILs) as recyclable reaction media has been studied under the catalytic action of CuCl2. With substrates bearing an aryl group on the triple bond, a mixture o
- Mancuso, Raffaella,Pomelli, Christian S.,Chiappetta, Piera,Gioia, Katia F.,Maner, Asif,Marino, Nadia,Veltri, Lucia,Chiappe, Cinzia,Gabriele, Bartolo
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p. 6673 - 6680
(2018/06/01)
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- Stoichiometric and Catalytic C?C and C?H Bond Formation with B(C6F5)3 via Cationic Intermediates
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This work showcases a new catalytic cyclization reaction using a highly Lewis acidic borane with concomitant C?H or C?C bond formation. The activation of alkyne-containing substrates with B(C6F5)3 enabled the first catalytic intramolecular cyclizations of carboxylic acid substrates using this Lewis acid. In addition, intramolecular cyclizations of esters enable C?C bond formation as catalytic B(C6F5)3 can be used to effect formal 1,5-alkyl migrations from the ester functional groups to unsaturated carbon–carbon frameworks. This metal-free method was used for the catalytic formation of complex dihydropyrones and isocoumarins in very good yields under relatively mild conditions with excellent atom efficiency.
- Soltani, Yashar,Wilkins, Lewis C.,Melen, Rebecca L.
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supporting information
p. 11995 - 11999
(2017/09/20)
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- Divergent syntheses of iodinated isobenzofuranones and isochromenones by iodolactonization of 2-alkynylbenzoic acids in ionic liquids
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The regiochemical outcome of the iodolactonization of 2-alkynylbenzoic acids, carried out at 100 °C in ionic liquids (ILs) as unconventional solvents and with molecular iodine as the iodine source, in the absence of external bases, was found to be strongl
- Mancuso, Raffaella,Pomelli, Christian C.,Malafronte, Francesco,Maner, Asif,Marino, Nadia,Chiappe, Cinzia,Gabriele, Bartolo
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supporting information
p. 4831 - 4841
(2017/07/10)
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- Hydroiodination-Triggered Cascade Reaction with I2/PPh3/H2O: Metal-Free Access to 3-Substituted Phthalides from 2-Alkynylbenzoates
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Phthalide is an important scaffold found in several biologically active compounds. Therefore, effective methods for the synthesis of phthalides are strongly desired. Herein, we describe the metal-free synthesis of 3-substituted phthalides by the reductive hydroiodination of 2-alkynylbenzoates through an I2/PPh3/H2O-triggered cascade reaction. A variety of 3-substituted phthalides were synthesized in excellent yields by a one-pot reaction involving four processes: desilylation, hydroiodination, cyclization, and reduction.
- Kawaguchi, Shin-Ichi,Nakamura, Kentaro,Yamaguchi, Kotaro,Sato, Yuki,Gonda, Yuhei,Nishioka, Masaaki,Sonoda, Motohiro,Nomoto, Akihiro,Ogawa, Akiya
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supporting information
p. 5343 - 5346
(2017/09/06)
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- Synthesis of isocoumarins: Rhenium complex-catalyzed cyclization of 2-ethynylbenzoic acids
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When 2-ethynylbenzoic acids were treated with a catalytic amount of a rhenium complex, such as ReCl(CO)5, 6-endo cyclization of 2-ethynylbenzoic acids proceeded with a high selectivity to give the corresponding isocoumarins in moderate to good yields.
- Umeda, Rui,Yoshikawa, Shunya,Yamashita, Kouji,Nishiyama, Yutaka
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p. 2172 - 2179
(2015/12/12)
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- Palladium(II)-catalyzed tandem annulation reaction of o-alkynylbenzoates with methyl vinyl ketone for the synthesis of isocoumarins
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A palladium(II)-catalyzed highly regioselective tandem reactions of o-alkynylbenzoates with methyl vinyl ketone for the synthesis of isocoumarins was developed. It is a convenient, mild and environmentally benign reaction with moderate to high yield. The
- Wang, Huan,Han, Xiuling,Lu, Xiyan
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p. 8626 - 8631
(2013/09/12)
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- On homogeneous gold/palladium catalytic systems
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Two substrates containing an aryl iodide and an allenoate ester were prepared and the goldinduced cycloisomerisation to vinylgold(I) species and their proto-deauration as well as the intramolecular palladium-catalysed cross-coupling reactions were investigated. Switching to catalytic amounts of gold and palladium and stoichiometric amounts of silver did indeed furnish the product of a cycloisomerisation/ intramolecular cross-coupling. Control experiments revealed that silver cannot substitute for gold or palladium in these reactions, but a different palladium catalyst in a different oxidation state also afforded the cycloisomerisation/intramolecular crosscoupling products in only slightly reduced yields. By ICP analysis the palladium was shown to contain gold only at the sub-ppm level. This shows how carefully results obtained with such systems have to be interpreted. Then a series of allylic and benzylic o-alkynylbenzoates were investigated in gold-and palladium-catalysed reactions. For esters of benzyl alcohol and cinnamyl alcohol no palladium co-catalyst was needed for the conversion. All reagents were thoroughly checked for palladium traces by ICP analysis in order to thoroughly exclude a gold/palladium cocatalysis. Optimisation of the gold complex, counter ion and solvent showed that gold(I) isonitrile precatalysts and silver triflate as activator in dioxane are suitable to convert a number of substrates with aryl, alkyl and even cyclopropyl substituents. Crossover experiments proved an intermolecular allyl transfer.
- Hashmi, A. Stephen K.,Lothschuetz, Christian,Doepp, Rene,Ackermann, Martin,De Buck Becker, Janosc,Rudolph, Matthias,Scholz, Christian,Rominger, Frank
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supporting information; experimental part
p. 133 - 147
(2012/04/10)
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- Concise route to 3-arylisoquinoline skeleton by lewis acid catalyzed c(sp3)-h bond functionalization and its application to formal synthesis of (±)-Tetrahydropalmatine
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An expeditious route to furnish an isoquinoline skeleton via hydride shift mediated C-H bond functionalization was developed. In this process, an unusual [1,5]-H shift without the assistance of the adjacent heteroatom took place to produce tetrahydroisoquinoline derivatives in good to excellent chemical yields. The formal synthesis of (±)-tetrahydropalmatine was achieved by exploiting this new transformation.
- Mori, Keiji,Kawasaki, Taro,Akiyama, Takahiko
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experimental part
p. 1436 - 1439
(2012/05/05)
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- Rapid access to 3-aryltetralin skeleton via C(sp3)-H bond functionalization: Investigation on the substituent effect of aromatic ring adjacent to C-H bond in hydride shift/cyclization sequence
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The concise construction of 3-aryltetralin skeleton via hydride shift mediated C-H bond functionalization was achieved. In this process, the benzylic [1,5]-H shift occurred smoothly to furnish tetralin derivatives in good to excellent chemical yields. The electronic and steric properties of the aromatic ring adjacent to the C-H bond influenced significantly the reactivity of this transformation.
- Mori, Keiji,Sueoka, Shosaku,Akiyama, Takahiko
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supporting information; experimental part
p. 1386 - 1388
(2012/01/12)
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- A simple and mild synthesis of 1H-isochromenes and (Z)-1-alkylidene-1,3- dihydroisobenzofurans by the iodocyclization of 2-(1-alkynyl)benzylic alcohols
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(Chemical Equation Presented) A variety of iodo-substituted isochromenes, dihydroisobenzofurans, and pyranopyridines are readily prepared in good to excellent yields under mild conditions by the iodocyclization of readily available 2-(1-alkynyl)benzylic a
- Mancuso, Raffaella,Mehta, Saurabh,Gabriele, Bartolo,Salerno, Giuseppe,Jenks, William S.,Larock, Richard C.
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supporting information; experimental part
p. 897 - 901
(2010/05/02)
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- Transmission of Polar Effects. Part 21. Alkaline Hydrolysis of the 2'- and 4'-substituted 2-Methoxycarbonyldiphenylacetylenes and (Z)-2'- and -4'- Substituted 2-Methoxycarbonylstilbenes and the Ionisation and Esterification, with Diazodiphenylmethane of t
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The rate coefficients for the alkaline hydrolysis of a series of 2'- and 4'-substituted 2-methoxycarbonyldiphenylacetylenes and (Z)-2-methoxycarbonylstilbenes have been determined in 70percent (v/v) dimethyl sulphoxide-water at both 30.0 and 50.0 deg C an
- Bowden, Keith,Ghadir, Khalaf D. F.
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p. 1333 - 1338
(2007/10/02)
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