- Rhodium-Catalyzed meta-Selective C?H Carboxylation Reaction of 1,1-Diarylethylenes via Hydrorhodation-Rhodium Migration
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A meta-selective C?H carboxylation reaction of 1,1-diarylethylene derivatives with CO2 by using a rhodium catalyst with NaOiPr as a stoichiometric reductant has been achieved. Together with hydrogenation of the ethylene moiety, a carboxyl group was introduced to the meta-position of the aryl ring with high selectivity over the ortho-positions. Experimental and computational mechanistic studies indicate that this carboxylation reaction proceeds via hydrorhodation on the ethylene moiety, followed by 1,4-rhodium migration and successive 1,2-rhodium migration on the aryl ring. The use of a bulky phosphine ligand seems to be the key to this unusual aryl-to-aryl 1,2-rhodium shift.
- Caner, Joaquim,Iwasawa, Nobuharu,Saito, Takanobu,Toriumi, Naoyuki
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supporting information
p. 23349 - 23356
(2021/09/18)
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- Synergistic N-Heterocyclic Carbene/Palladium-Catalyzed Umpolung 1,4-Addition of Aryl Iodides to Enals
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An umpolung 1,4-addition of aryl iodides to enals promoted by cooperative (terpy)Pd/NHC catalysis was developed that generates various bioactive β,β-diaryl propanoate derivatives. This system is not only the first reported palladium-catalyzed arylation of NHC-bound homoenolates but also expands the scope of NHC-induced umpolung transformations. A diverse array of functional groups such as esters, nitriles, alcohols, and heterocycles are tolerated under the mild conditions. This method also circumvents the use of moisture-sensitive organometallic reagents.
- Yang, Wenjun,Ling, Bo,Hu, Bowen,Yin, Haolin,Mao, Jianyou,Walsh, Patrick J.
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supporting information
p. 161 - 166
(2019/12/03)
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- C-C Bond Cleavage of Unactivated 2-Acylimidazoles
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2-Acylimidazoles are widely used as post-Transformable carboxylic acid equivalents in chemoselective and enantioselective reactions. Their transformations, however, require pretreatment with highly reactive, toxic methylating reagents to facilitate C-C bond cleavage. Here, we demonstrate that such pretreatment can be avoided and the C-C bond cleaved under neutral conditions without the use of additional reagents or catalysts. The scope of the reaction, including the use of products reported in the literature as substrates, and some mechanistic insights are described.
- Xin, Hai-Long,Pang, Bo,Choi, Jeesoo,Akkad, Walaa,Morimoto, Hiroyuki,Ohshima, Takashi
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p. 11592 - 11606
(2020/10/23)
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- Visible-Light-Driven Reductive Carboarylation of Styrenes with CO2 and Aryl Halides
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The first example of visible-light-driven reductive carboarylation of styrenes with CO2 and aryl halides in a regioselective manner has been achieved. A broad range of aryl iodides and bromides were compatible with this reaction. Moreover, pyridyl halides, alkyl halides, and even aryl chlorides were also viable with this method. These findings may stimulate the exploration of novel visible-light-driven Meerwein arylation-addition reactions with user-friendly aryl halides as the radical sources and the photocatalytic utilization of CO2
- Gao, Yuzhen,Li, Gang,Wang, Hao,Zhou, Chunlin
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supporting information
p. 8122 - 8129
(2020/05/20)
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- Synthetic method of beta, beta-disubstituted propionate derivative
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The invention discloses a synthetic method of beta, beta-disubstituted propionate derivative, and belongs to the field of organic synthesis. An aldehyde compound, an iodide and an alcohol are adoptedto synthesize the beta, beta-disubstituted propionate derivative through a one-pot method, and the synthetic method is used for realizing beta-bit arylation and esterification of carbonyl groups of alpha, beta-unsaturated aldehyde to synthesize beta, beta-disubstituted methyl propionate. The synthesis steps of a traditional method are reduced, the reaction yield is increased, and according to thesynthetic method, raw materials are cheap, the operation steps are simple, the reaction condition is mild, and applicability of reaction substrates is greatly enriched.
- -
-
Paragraph 0044; 0075-0084
(2020/02/19)
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- Phenoxy-Dialkoxy Borates as a New Class of Readily Prepared Preactivated Reagents for Base-Free Cross-Coupling
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One of the most useful chemical transformations of organoboronic acids is the Suzuki–Miyaura cross-coupling reaction. Although it has vast application, it possesses some limitations: boronic acids can be difficult to quantify accurately due to their tendency to form oligomeric anhydrides and they must be activated under basic conditions. To address these problems, a new class of boronic acid derivatives is described. Phenoxy-dialkoxy borates are prepared under mild conditions and show good solubility in common organic solvents. These adducts can be used in base-free metal-catalysed cross-coupling reactions, including orthogonal reactions with MIDA boronates and trifluoroborates.
- Paladino, Marco,Boghi, Michele,Hall, Dennis G.
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supporting information
p. 6566 - 6570
(2019/10/22)
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- Rhenium complex-catalyzed carbon-carbon formation of alcohols and organosilicon compounds
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The coupling reactions of allylic and benzylic alcohols and allyltrimethylsilane are efficiently catalyzed by a rhenium complex to give the corresponding 1,5-dienes and alkenes in moderate to good yields. Similarly, alcohols were coupled with ketene silyl acetals to form the corresponding esters.
- Umeda, Rui,Jikyo, Toshifumi,Toda, Kazuki,Osaka, Issey,Nishiyama, Yutaka
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supporting information
p. 1121 - 1124
(2018/02/21)
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- Catalytic Use of Low-Valent Cationic Gallium(I) Complexes as π-Acids
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Transformations of alkene and alkyne substrates relevant to π-Lewis acid catalysis have been performed using low-valent Ga(I) species for the first time. [Ga(I)(PhF)2]+[Al(ORF)4]? and gallium dichloride (i. e. [Ga(I)]+[GaCl4]?) proved to be efficient catalysts for cycloisomerizations, Friedel-Crafts reactions, transfer hydrogenations, and reductive hydroarylations. Their activity is compared to more common Ga(III) complexes. This study shows that even the readily available and yet overlooked gallium dichloride salt can be a more active π-Lewis acid catalyst than gallium trichloride or other Ga(III) species. (Figure presented.).
- Li, Zhilong,Thiery, Guillaume,Lichtenthaler, Martin R.,Guillot, Régis,Krossing, Ingo,Gandon, Vincent,Bour, Christophe
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supporting information
p. 544 - 549
(2017/11/27)
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- Direct Catalytic Alcoholysis of Unactivated 8-Aminoquinoline Amides
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Direct catalytic alcoholysis of unactivated amides is one of the most difficult challenges in organic chemistry, and an applicable method for cleaving amides used as directing groups in regioselective functionalization reactions has not been reported. Herein, we report direct catalytic alcoholysis of 8-aminoquinoline amides, which are highly effective directing groups in regioselective functionalization reactions. The reactions proceeded with a simple combination of substrates, air-stable catalysts, and alcohols, affording the corresponding esters in good yields with broad functional group tolerance. Highly chemoselective cleavage of the 8-aminoquinoline amides in the presence of related carbonyl functionalities and preliminary mechanistic studies are also described.
- Deguchi, Toru,Xin, Hai-Long,Morimoto, Hiroyuki,Ohshima, Takashi
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p. 3157 - 3161
(2017/06/09)
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- Metal-Free Enantioselective Oxidative Arylation of Alkenes: Hypervalent-Iodine-Promoted Oxidative C?C Bond Formation
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The enantioselective oxyarylation of (E)-6-aryl-1-silyloxylhex-3-ene was achieved using a lactate-based chiral hypervalent iodine(III) reagent in the presence of boron trifluoride diethyl etherate. The silyl ether promotes the oxidative cyclization, and enhances the enantioselectivity. In addition, the corresponding aminoarylation was achieved.
- Shimogaki, Mio,Fujita, Morifumi,Sugimura, Takashi
-
supporting information
p. 15797 - 15801
(2016/12/16)
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- Rh-catalyzed 1,4-addition of triallyl(aryl)silanes to α,β-unsaturated carbonyl compounds
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Rh-catalyzed 1,4-addition of triallyl(aryl)silane to α,β-unsaturated carbonyl compounds was developed. Triallyl(aryl)silanes were used as air- and moisture-stable silicon nucleophiles. Allylsilanes were converted to silanols in situ and underwent transmetalation. This method can accept a wide range of functionalized triallyl(aryl)silane and α,β-unsaturated carbonyl compounds.
- Kamei, Toshiyuki,Uryu, Mizuho,Shimada, Toyoshi
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supporting information
p. 1622 - 1624
(2018/03/22)
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- One-pot tandem hydrophenylation and ionic hydrogenation of 3-phenylpropynoic acid derivatives under superelectrophilic activation
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The reactions of esters and amides of 3-phenylpropynoic acid with strong Lewis acids AlX3 (X = Cl, Br) or conjugate Br?nsted-Lewis superacids HX-AlX3 (X = Cl, Br) in benzene and cyclohexane at room temperature afforded 3,3-diphenylpropanoic acid derivatives in up to 94% yield. This tandem reaction of the acetylene bond proceeded by hydrophenylation followed by ionic hydrogenation.
- Nilov, Denis I.,Vasilyev, Aleksander V.
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p. 5714 - 5717
(2015/09/29)
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- Ligand-free nickel-catalysed 1,4-addition of arylboronic acids to α,β-unsaturated carbonyl compounds
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A simple and efficient ligand-free nickel-based catalytic system has been developed for the 1,4-addition of arylboronic acids to α,β-unsaturated carbonyl compounds. With catalyst loadings of 1-2 mol%, a series of 1,4-adducts from chalcones and cinnamates was obtained in moderate to excellent yields within 5-30 min under a nitrogen atmosphere and microwave irradiation. The 1,4-addition of arylboronic acids to acrylates is less efficient.
- Chen, Wen,Sun, Lu,Huang, Xi,Wang, Jiayi,Peng, Yanqing,Song, Gonghua
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p. 1474 - 1482
(2015/05/19)
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- Dibromoindium(iii) cations as a π-Lewis acid: Characterization of [IPr·InBr2][SbF6] and its catalytic activity towards alkynes and alkenes
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[IPr·InBr2][SbF6] (2) (IPr = 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene) has been synthesized and characterized in the solid state. This complex proved to be a very active catalyst for hydroarylations, transfer hydrogenations, and cycloisomerizations.
- Michelet, Bastien,Colard-Itté, Jean-Rémy,Thiery, Guillaume,Guillot, Régis,Bour, Christophe,Gandon, Vincent
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p. 7401 - 7404
(2015/05/27)
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- Gallium-assisted transfer hydrogenation of alkenes
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We report a rare case of alkene transfer hydrogenation using a main-group compound instead of a transition-metal complex as catalyst. We disclosed that 1, 4-cyclo-hexadiene can be used as H2 surrogate towards olefin reduction in the presence of [IPrGaCl2][SbF6]. Hydrogenative cycli-zations have also been carried out because this cationic gallium complex is also a potent hydroarylation catalyst.
- Michelet, Bastien,Bour, Christophe,Gandon, Vincent
-
supporting information
p. 14488 - 14492
(2015/04/16)
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- New Pd(II) binuclear complexes as effective catalysts in oxidative-heck reaction using arylboronic acid derivatives
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A series of new binuclear Pd(II) complexes based on chelating diimines and bridging diphosphine or diimine ligands have been synthesized and characterized successfully. The formula of the new complexes are [Pd2(mbyp) 2(DPA)2](PF6)4 (1), [Pd 2(mbyp)2(DPE)2] (PF6)4 (2), [Pd2(mbyp)2(4,4-byp)2] (PF 6)4 (3), [Pd2(mbyp)2(t-pye) 2] (PF6)4 (4) [mbyp= 4,4-dimethyl-2,2- bipyridine, DPA= 1,2-bis(diphenylphosphino)acetylene, DPE= 1,2- bis(diphenylphosphino)ethylene, 4,4-byp= 4,4-bipyridine, and t-ype= trans 1,2-bis(4-pyridyl)ethylene)]. The catalytic activities of the new complexes have been investigated in the coupling of arylboronic acid derivatives to various olefins. Results obtained showed interesting catalytic activities and chemoselectivities for the new complexes in the coupling reactions to produce the conjugate addition and heck coupling products under free base or oxidant conditions.
- Suleiman, Rami,Shakil Hussain,Fettouhi, Mohammed,El Ali, Bassam
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scheme or table
p. 850 - 856
(2012/09/22)
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- Palladium-catalyzed desulfitative conjugate addition of aryl sulfinic acids and direct ESI-MS for mechanistic studies
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A new and efficient method for palladium(II) catalytic desulfitative conjugate addition of arylsulfinic acids with α,β-unsaturated carbonyl compound has been developed. The key reacting intermediates including aryl Pd(II) sulfinic intermediate, aryl Pd(II), and C=O-Pd complexes were captured by ESI-MS/MS, which provide new experimental evidence for the understanding of addition mechanism.
- Wang, Huifeng,Li, Yaming,Zhang, Rong,Jin, Kun,Zhao, Defeng,Duan, Chunying
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supporting information; experimental part
p. 4849 - 4853
(2012/07/02)
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- Rhodium-catalyzed double 1,4-addition of arylboronic acids to β-aryloxyacrylates involving β-oxygen elimination
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The rhodium-catalyzed addition reaction of arylboronic acids to β-aryloxyacrylates gives 3,3-diarylpropanoates in good yields. The double arylation reaction proceeds via the intermediate cinnamates generated by β-oxygen elimination. Copyright
- Matsuda, Takanori,Shiose, Shigeru,Suda, Yuya
-
supporting information; experimental part
p. 1923 - 1926
(2011/10/05)
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- One-pot hydroxy group activation/carbon-carbon bond forming sequence using a Bronsted base/bronsted acid system
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A new sequential two-step multicatalytic strategy is presented consisting in the efficient DBU-catalysed trichloroacetimidation of an alcohol followed by a ditriflylamine (Tf2NH)-catalysed intermolecular alkylation by silicon-based nucleophiles and C-H nucleophiles. The distinct feature of the trichloroacetimidate group allows use of weaker acid catalysts such as 1,1′-bi-2-naphthol (BINOL)-derived phosphoric acid, pointing out the possible development of an enantioselective variant. This unprecedented sequential one-pot Bronsted base-Bronsted acid catalysis further expands the synthetic scope of the trichloroacetimidate group. Copyright
- Devineau, Alice,Pousse, Guillaume,Taillier, Catherine,Blanchet, Jerome,Rouden, Jacques,Dalla, Vincent
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supporting information; experimental part
p. 2881 - 2886
(2011/02/21)
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- New 1,3-dioxolane and 1,3-dioxane derivatives as effective modulators to overcome multidrug resistance
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Multidrug resistance (MDR) to antitumor agents represents a major obstacle to a successful chemotherapy of cancer. Overexpression of P-glycoprotein (p-gp) seems to be the major factor responsible for MDR. A large number of chemically unrelated compounds are known to interact with p-gp resulting in a decreasing resistance. In our efforts related to structure-activity studies of new potential MDR reversal agents we synthesized a series of compounds that differ in the aromatic core structure, the linker, and the basic moiety. For our search of new aromatic core structures we synthesized novel 2,2-diphenyl-1,3-dioxolane, 2,2- diphenyl-1,3-dioxane, and 4,5-diphenyl-1,3-dioxolane derivatives. A range of lipophilic linker structures and protonable basic moieties were synthesized and investigated to optimize the structure of the potential MDR-modulators. The compounds were tested in vitro using human Caco-2 cells. Both the cytotoxicity of the synthons and their ability to resensitize the cells were determined with a MTT assay. The results show that at low concentration various substances reverse tumor cell MDR. Some of the new structures show better effects than established modulators like trifluoperazine.
- Schmidt, Matthias,Ungvari, Johannes,Gloede, Julia,Dobner, Bodo,Langner, Andreas
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p. 2283 - 2297
(2007/10/03)
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- Conjugate addition of organocopper reagents in dichloromethane to α,β-unsaturated esters
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Organocopper reagents in conjunction with Lewis acid activators provide greater stability than traditional cuprate reagents while maintaining the reactivity needed for conjugate addition reactions in dichloromethane. Whereas cuprates engage in cross-coupl
- Yang, Jingyue,Dudley, Gregory B.
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p. 7887 - 7889
(2008/03/11)
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- Rhodium-catalyzed aryl transfer from trisubstituted aryl methanols to α,β-unsaturated carbonyl compounds
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(Chemical Equation Presented) A process of elimination: The rhodium-catalyzed arylation of α,β-unsaturated carbonyl compounds with 9-aryl-10-benzyl-9,10-dihydroacridin-9-ols 1 as arylating reagents proceeds efficiently via β-aryl elimination of the rhodium alkoxide intermediates, to give the 1,4-addition products in high yields (see scheme; Bn = benzyl, cod = cycloocta-1,5-diene).
- Nishimura, Takahiro,Katoh, Taisuke,Hayashi, Tamio
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p. 4937 - 4939
(2008/02/08)
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- Synthesis of N-glyoxyl prolyl and pipecolyl amides and thioesters and evaluation of their in vitro and in vivo nerve regenerative effects
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The recent discovery that small molecule ligands for the peptidyl-prolyl isomerase (PPIase) FKBP12 possess powerful neuroprotective and neuroregenerative properties in vitro and in vivo suggests therapeutic utility for such compounds in neurodegenerative disease. The neurotrophic effects of these compounds are independent of the immunosuppressive pathways by which drugs such as FK506 and rapamycin operate. Previous work by ourselves and other groups exploring the structure-activity relationships (SAR) of small molecules that mimic only the FKBP binding domain portion of FK506 has focused on esters of proline and pipecolic acid. We have explored amide and thioester analogues of these earlier structures and found that they too are extremely potent in promoting recovery of lesioned dopaminergic pathways in a mouse model of Parkinson's disease. Several compounds were shown to be highly effective upon oral administration after lesioning of the dopaminergic pathway, providing further evidence of the potential clinical utility of a variety of structural classes of FKBP12 ligands.
- Hamilton, Gregory S.,Wu, Yong-Qian,Limburg, David C.,Wilkinson, Douglas E.,Vaal, Mark J.,Li, Jia-He,Thomas, Christine,Huang, Wei,Sauer, Hansjorg,Ross, Douglas T.,Soni, Raj,Chen, Yi,Guo, Hongshi,Howorth, Pamela,Valentine, Heather,Liang, Shi,Spicer, Dawn,Fuller, Mike,Steiner, Joseph P.
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p. 3549 - 3557
(2007/10/03)
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- Conjugate addition of organosiloxanes to α,β-unsaturated carbonyl compounds catalyzed by a cationic rhodium complex
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A novel, additive-free, and clean conjugate addition reaction of organosiloxanes to α,β-unsaturated carbonyl compounds catalyzed by a cationic rhodium complex in water-containing solvent has been developed. A plausible reaction mechanism involving the add
- Oi, Shuichi,Honma, Yoshio,Inoue, Yoshio
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p. 667 - 669
(2007/10/03)
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- Rhodium-catalyzed conjugate addition of aryl- and alkenyl-stannanes to α,β-unsaturated carbonyl compounds
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The addition of aryl- or alkenyl-trimethylstannanes to α,β-unsaturated carbonyl compounds in the presence of a catalytic amount of a cationic rhodium complex ([Rh(cod)(MeCN)2]BF4) and water to afford the conjugate addition products in good yields was examined. It was observed that addition of water was necessary for the reaction to proceed smoothly. The aryl- or alkenyl-rhodium complex, which is generated by the transmetalation from the organotin compound, is considered to be the active catalytic species.
- Oi, Shuichi,Moro, Mitsutoshi,Ito, Hisanori,Honma, Yoshio,Miyano, Sotaro,Inoue, Yoshio
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- Cyclopropanation of benzylidenemalononitrile with dialkoxycarbenes and free radical rearrangement of the cyclopropanes
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Thermolysis of 2-cinnamyloxy-2-methoxy-5,5-dimethyl-Δ3-1,3,4-oxadiazoline (1a) and the analogous 2-benzyloxy-2-methoxy compound (1b) at 110°C, in benzene containing benzylidenemalononitrile, afforded products of apparent regiospecific addition of methoxycarbonyl and cinnamyl (or benzyl) radicals to the double bond. When the thermolysis of 1a was run with added TEMPO, methoxycarbonyl and cinnamyl radicals were captured. Thermolysis of the 2,2-dibenzyloxy analogue (1c) in the presence of benzylidenemalononitrile gave an adduct that is formally the product of addition of benzyloxycarbonyl and benzyl radicals to the double bond. In this case, a radical addition mechanism could be ruled out, because the rate constant for decarboxylation of benzyloxycarbonyl radicals is very large. A mechanism that fits all of the results is predominant cyclopropanation of benzylidenemalononitrile by the dialkoxycarbenes derived from the oxadiazolines, in competition with fragmentation of the carbenes to radical pairs. The cyclopropanes so formed then undergo homolytic ring-opening to the appropriate diradicals. Subsequent β-scission of the diradicals to afford radical pairs, and coupling of those pairs, gives the final products. Thus, both carbene and radical chemistry are involved in the overall processes.
- Merkley,Venneri,Warkentin
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p. 312 - 318
(2007/10/03)
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- Rhodium catalyzed conjugated addition of unsaturated carbonyl compounds by triphenylbismuth in aqueous media and under an air atmosphere
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In the presence of a rhodium catalyst, α,β-unsaturated esters and ketones react with triphenylbismuth in aqueous media and under an air atmosphere to give the corresponding conjugated addition products in high yields.
- Venkatraman, Sripathy,Li, Chao-Jun
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p. 781 - 784
(2007/10/03)
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- Quasi-nature catalysis: Conjugated addition of unsaturated carbonyl compounds with aryl and vinyltin reagents catalyzed by rhodium in air and water
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In air and water, trialkylphenyl- or trialkylvinylstannanes react with α,β-unsaturated esters and ketones to give the corresponding conjugated addition products in high yields in the presence of a rhodium catalyst.
- Venkatraman, Sripathy,Meng, Yue,Li, Chao-Jun
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p. 4459 - 4462
(2007/10/03)
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- Asymmetric conjugate 1,4-addition of arylboronic acids to α,β-unsaturated esters catalyzed by rhodium(I)/(S)-binap
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Arylboronic acids underwent the conjugate 1,4-addition to α,β-unsaturated esters to give β-aryl esters in high yields in the presence of a rhodium(I) catalyst. The addition of arylboronic acids to isopropyl crotonate resulted in high yields and high enantioselectivity exceeding 90% ee in the presence of 3 mol % of Rh(acac)(C2H4)2 and (S)-binap at 100 °C. The rhodium/(S)-binap complex provided (R)-3-phenylbutanoate in the addition of phenylboronic acid to benzyl crotonate. The effects on the enantioselectivity of chiral phosphine ligands, rhodium precursors, and substituents on α,β-unsaturated esters are discussed, as well as the mechanistic aspect of the catalytic cycle.
- Sakuma, Satoshi,Sakai, Masaaki,Itooka, Ryoh,Miyaura, Noria
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p. 5951 - 5955
(2007/10/03)
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- Rhodium-catalyzed Conjugate Addition of Arylstannanes to α,β-Unsaturated Ketones and Esters
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Aryltrimethylstannanes react with α,β-unsaturated ketones and esters in the presence of a catalytic amount of cationic rhodium complex, BF4, affording the conjugate addition products in good yields.
- Oi, Shuichi,Moro, Mitsutoshi,Ono, Sachie,Inoue, Yoshio
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-
- Palladium(II)-catalyzed hydroarylation of α,β-unsaturated aldehydes and ketones with triarylstibines in the presence of silver acetate
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Triarylstibines react with α,β-unsaturated aldehydes and ketones in acetic acid at 25°C in the presence of silver acetate and a catalytic amount of palladium(II) acetate to afford the hydroarylation products by conjugate addition in good yields.
- Cho, Chan Sik,Tanabe, Koichiro,Uemura, Sakae
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p. 1275 - 1278
(2007/10/02)
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- Convenient Synthetic Sequence for the Preparation of Indanones
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A convenient and general methods is reported for the synthesis of indanones from aryl ketones or aldehydes.
- Smonou, Ioulia,Orfanopoulos, Michael
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p. 1387 - 1397
(2007/10/02)
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- CHLORO- AND IODOTRIMETHYLSILANE-ACTIVATED ADDITIONS OF ORGANOCOPPER COMPOUNDS TO ENONES AND ENOATES
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Organocopper compounds add to enones and enoates in the presence of chloromethylsilane in ether giving the conjugate adducts in preparatively usefu yields via the silyl enol ethers.Presence of lithium iodide is important and excess of chlorotrimethylsilane accelerates the reactions.The combination of organocopper compound, iodotrimethylsilane and dimethyl sulfide gave faster reactions and very high yields, particularly in dichloromethane, where the reaction mixtures gradually became homogeneous.
- Bergdahl, Mikael,Lindstedt, Eva-Lotte,Nilsson, Martin,Olsson, Thomas
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p. 2055 - 2062
(2007/10/02)
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- 2-Thienyl as Auxiliary Group in Mixed Lithium Diorganocuprate
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2-Thienylcopper (ThCu) gives mixed lithium organothienylcuprate reagents (LiRThCu) with organolithium compounds (R = methyl, butyl, phenyl and 2-pyridyl) in ether.These cuprates react with enones or enoates adding the group R, 1,4 to the substrates, 2-thienylcopper being regenerated.The isolated yields of conjugate addition are substantial (40-89percent) and comparable to those obtained with LiR2Cu in corresponding addition.Since a mixed organothienylcuprates are rather stable at 0 deg C, and sometimes even at room temperature, the 2-thienyl group is an useful auxiliary in mixed lithium organocuprates for conjugate addition.Lithium bis(2-thienyl)cuprate, on the other hand, gives 1,2- as well as 1,4-addition of the 2-thienyl group to enones and to methyl crotonate.
- Lindstedt, Eva-Lotte,Nilsson, Martin
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p. 466 - 469
(2007/10/02)
-
- Redox-photosensitised Reactions. Part 12. Effects of Magnesium(II) Ion on the 2+ -Photomediated Reduction of Olefins by 1-Benzyl-1,4-dihydronicotinamide: Metal-ion Catalysis of Electron Transfer Processes Involving an NADH Model
-
Magnesium(II) ion catalyses the photosensitised reduction of carbon-carbon double bonds of dimethylfumarate, derivates of methyl cinnamate, and some other related olefins by 1-benzyl-1.4-dihydronicotinamide (BNAH), which proceeds via sequential two electron transfer initiated by the photoexcitation of +2 (bpy = 2,2'-bipyridine).The metal ion forms a complex with BNAH in methanol as well as in 10:1 (v/v) pyridine-methanol, leading to the retardation of electron transfer from BNAH to luminescent excited-state Ru(ppy)32+.The net metal-ion effects arise from the catalysis of both the first and second one-electron reduction processes.
- Ishitani, Osamu,Ihama, Mikio,Miyauchi, Yoji,Pac, Chyongjin
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p. 1527 - 1532
(2007/10/02)
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- Redox-Photosensitized Reactions. 11. Ru(bpy)32+-Photosensitized Reactions of 1-Benzyl-1,4-dihydronicotinamide with Aryl-Substituted Enones, Derivatives of Methyl Cinnamate, and Substituted Cinnamonitriles: Electron-Transfer Mechanism and Structure-Reactivity Relationship
-
Reactions of 1-benzyl-1,4-dihydronicotinamide (BNAH) with aryl-substituted enones and derivatives of methyl cinnamate and cinnamonitrile (1a-u) are photosensitized by Ru(bpy)32+ (bpy = 2,2'-bipyridine).The reduction of carbon-carbon double bonds commonly requires the substitution of either an electron-withdrawing aryl group or two phenyl groups at the β-carbon atom of 1.With enones which possess one aryl substituent with no extra electron-withdrawing group at the β position, the photosensitized reactions result in no two-electron reductions but give 1:1 adducts (4d-h) along with half-reduced dimers of olefins (3d and 3g) and a half-oxidized dimer of BNAH (5).The observed results can be easily interpreted by assuming the intervention of 1-benzyl-3-carbamoyl-1,4-dihydropyridin-4-yl radical (BNA.) and half-reduced species (.1-H) as key intermediates that are formed by mediated electron-proton transfer from BNAH to 1 in which Ru(bpy)32+ acts as a one-electron shuttle upon photoexcitation in the initial electron transfer.Whether BNA. undergoes electron transfer to or a radical-coupling reaction with .1-H depends on steric and electronic properties of .1-H which should be affected by the substituents at the radical center.Mechanistic implications for thermal reactions of NADH models with olefins in the dark are briefly discussed on the basis of these observations.
- Pac, Chyongjin,Miyauchi, Yoji,Ishitani, Osamu,Ihama, Mikio,Yasuda, Masahide,Sakurai, Hiroshi
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- Palladium-Catalyzed Conjugate Addition Type Reaction of Aryl Iodides with α,β-Unsaturated Ketones
-
Aryl iodides have been found to react with α,β-unsaturated ketones in the presence of catalytic amounts of palladium, an excess of formic acid, and triethylamine, giving rise to conjugate addition type products.The electron-withdrawing power of the group attached to the olefinic double bond, the substituent β to the carbonyl group, and the basic reaction medium appear to effect greatly the conjugate addition/vinylic substitution ratio.
- Cacchi, S.,Arcadi, A.
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p. 4236 - 4240
(2007/10/02)
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- THE REACTION OF DIAZOACETIC ESTER WITH THIOBENZOPHENONE
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Methyl diazoacetate reacts with two equivalents of thiobenzophenone to furnish two isomeric 1,3-dithiolanes and nitrogen; the intermediate thiocarbonyl ylide is intercepted by 1,3-dipolar cycloaddition or undergoes electrocyclic ring closure.
- Kalwinsch, Ivars,Huisgen, Rolf
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p. 3941 - 3944
(2007/10/02)
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- CONJUGATE ADDITION REACTIONS OF SOME MAGNESIUM-BASED ORGANOCUPRATES WITH α-ETHYLENIC CARBONYL COMPOUNDS
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Bromomagnesium diphenylcuprate and the iodomagnesium dimethylcuprate reagent (prepared from 2 RMgX + CuI) react with methyl or ethyl 3-phenyl-propenoate and methyl 2-butenoate to give 25-70percent yileds of the corresponding conjugate addition products.Th
- Rahman, M. T.,Saha, S. L.,Hansson, A.-T.
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