- NOVEL RUTHENIUM COMPLEXES, METHODS OF THEIR PREPARATION AND APPLICATION THEREOF IN OLEFIN CROSS METATHESIS
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The invention relates to novel ruthenium complexes of general formula 4 in which the substituents are defined herein. The invention relates also to methods for preparing such compounds and use thereof as catalysts and/or (pre)catalysts in olefin cross metathesis.
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Page/Page column 34
(2022/03/07)
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- Oxidative rearrangement of alkenes using in situ generated hypervalent iodine(III)
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A novel protocol for the oxidative rearrangement of alkenes using in situ generated hypervalent iodine(III) was developed. This approach uses inexpensive, readily available, and stable chemicals (PhI, mCPBA, and TsOH) giving rearrangement products in yields comparable to those obtained using the more expensive commercially available [hydroxy(tosyloxy)iodo]benzene [HTIB or Koser's reagent]. Additionally, an alternative protocol for the synthesis of 1-methyl-2-tetralone through the one-step epoxidation/rearrangement of 4-methyl-1,2-dihydronaphthalene using mCPBA and TsOH was developed.
- Ahmad, Anees,Scarassati, Paulo,Jalalian, Nazli,Olofsson, Berit,Silva Jr., Luiz F.
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supporting information
p. 5818 - 5820
(2013/10/01)
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- Metal-free synthesis of indanes by iodine(iii)-mediated ring contraction of 1,2-dihydronaphthalenes
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A metal-free protocol was developed to synthesize indanes by ring contraction of 1,2-dihydronaphthalenes promoted by PhI(OH)OTs (HTIB or Koser's reagent). This oxidative rearrangement can be performed in several solvents (MeOH, CH3CN, 2,2,2-trifluoroethanol (TFE), 1,1,1,3,3,3-hexafluoroisopropanol (HFIP), and a 1:4 mixture of TFE:CH2Cl2) under mild conditions. The ring contraction diastereoselectively gives functionalized trans-1,3-disubstituted indanes, which are difficult to obtain in synthetic organic chemistry. ?2011 Sociedade Brasileira de Qui?mica.
- Siqueira, Fernanda A.,Ishikawa, Eloisa E.,Fogac?a, Andre?,Faccio, Andre?a T.,Carneiro, Va?nia M. T.,Soares, Rafael R. S.,Utaka, Aline,Te?be?ka, Iris R. M.,Bielawski, Marcin,Olofsson, Berit,Silva Jr., Luiz F.
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body text
p. 1795 - 1807
(2012/06/01)
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- Efficient platinum(II) catalyzed hydroformylation reaction in water: Unusual product distribution in micellar media
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The hydroformylation of a variety of terminal and internal alkenes is efficiently performed by cationic platinum triflate complexes of the type [P2Pt(H2O)2](OTf)2 under mild conditions in an aqueous micellar medium. The use of surfactants is essential to ensure dissolution of the catalyst and substrate in water with catalysts being positioned on the anionic surface of the micelles. Aldehydes are obtained with linear to branched ratios up to >99:1. With styrene derivatives also the corresponding benzaldehydes are formed. The catalyst can be separated by extraction of the organic products with hexane and recycled for at least four times with only a modest loss of activity and no effect on selectivity.
- Gottardo, Marina,Scarso, Alessandro,Paganelli, Stefano,Strukul, Giorgio
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experimental part
p. 2251 - 2262
(2010/12/25)
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- Ring contraction of 1,2-dihydronaphthalenes promoted by thallium(III) in acetonitrile: A diastereoselective approach to indanes
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Trans-1,3-Disubstituted indanes are conveniently accessed by a stereoselective ring contraction of 1,2-dihydronaphthalenes upon treatment with thallium(III) nitrate (TTN) in acetonitrile. Under these conditions, the oxidative rearrangement of either di- or trisubstituted double bonds is possible. Georg Thieme Verlag Stuttgart.
- Ferraz, Helena M. C.,Carneiro, Vania M. T.,Silva Jr., Luiz F.
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experimental part
p. 385 - 388
(2009/06/18)
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- Et2Zn-mediated rearrangement of bromohydrins
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(Chemical Equation Presented) A simple and highly efficient method for the rearrangement of bromohydrins mediated by Et2Zn to synthesize carbonyl compounds was described. Various β-bromo alcohols were treated with 0.6 equiv of Et2Zn to form a zinc complex in CH 2Cl2 at room temperature for 2 h, followed by 1,2-migration to give the corresponding carbonyl compounds. This remarkable and clean rearrangement is general for acyclic and cyclic bromohydrins, and a variety of ring-expansive and -contractive carbonyl compounds were obtained in good to excellent yields according to the feature of the starting bromohydrins. The functional group tolerance of organozinc reagents in this reaction will be useful in organic synthesis. The scope and limitations of this rearrangement process were also investigated.
- Li, Lezhen,Cai, Peijie,Guo, Qingxiang,Xue, Song
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p. 3516 - 3522
(2008/09/20)
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- Microbial deracemization of α-substituted carboxylic acids: Substrate specificity and mechanistic investigation
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A new enzymatic method for the preparation of optically active α-substituted carboxylic acids is reported. This technique is called deracemization reaction, which provides us with a route to obtain the enantiomerically pure compounds, theoretically in 100% yield starting from the racemic mixture. This means that the synthesis of a racemate is almost equal to the synthesis of the optically active compound, and this concept is entirely different from the commonly accepted one in the asymmetric synthesis. Using the growing cell system of Nocardia diaphanozonaria JCM3208, racemates of 2-aryl- and 2-aryloxypropanoic acid are deracemized smoothly and (R)-form-enriched products are recovered in high chemical yield (>50%). In addition, using optically active starting compounds and deuterated derivatives as well as inhibitors, we have disclosed the fact that a new type of enzyme takes part in this biotransformation, and that the reaction proceeds probably via the same mechanism as that in rat liver.
- Kato, Dai-Ichiro,Mitsuda, Satoshi,Ohta, Hiromichi
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p. 7234 - 7242
(2007/10/03)
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- Phosphine oxides as ligands in the hydroformylation reaction
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A new rhodium-phosphine oxide system has been investigated in the hydroformylation reaction. Some of the phosphine oxide ligands of type 2-12 (i.e. R2N(CH2)nP(O)R′2, R′ = Ph, Cy; n = 0, 1, 2, 3; R = Me, Et, iPr, or NR2 = 2-pyridyl) were found to be better ligands than the phosphine analogues (i.e. R2N(CH)2PR′2) in the hydroformylation of olefins catalyzed by rhodium complexes. Detailed examination of factors controlling the selectivity for aldehydes formation revealed the following characteristics of the reaction: (a) use of ligands having bulkier amino groups decrease the yield of the aldehydes slightly; (b) ligands having amino groups with low basicity decrease the rate of the hydroformylation dramatically; (c) the electronic properties of the phosphine oxide group have no influence on the hydroformylation reaction; (d) uncoordinating solvents of low polarity such as dichloromethane, chloroform and toluene gave the best reaction rate and selectivity; (e) spectroscopic investigation of the hydroformylation of styrene catalyzed by rhodium with ligand 2 shows that the ligand is coordinated by the amino and the phosphine oxide groups under 1 atm of CO-H2 and only by the amino group under 600 lbf in-2 of CO-H2.
- Abu-Gnim, Chalil,Amer, Ibrahim
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p. 235 - 243
(2007/10/03)
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- Photochemistry of 1-Phenyl-1,2-dihydronaphthalene in Methanol
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The photochemistry of 1-phenyl-1,2-dihydronaphthalene (1) in methanol and hexane has been investigated.The lack of influence of solvent polarity and of the presence of sulfuric acid on the rate of formation of exo-4-phenylbenzobicyclohex-2-ene (exo-2) from the primary, ring-opened photoproduct cZt-3a of 1 precludes a sudden-polarized, zwitterionic excited state from being involved in the intramolecular photocycloaddition reaction leading to exo-2.The experimental results can be rationalized by assuming that this photoprocess involves a concerted ?4a+ ?2a-type electrocyclic reaction. cis-Dibenzobicycloocta-2,7-diene (8) is proposed to arise by photocyclization of cZc-3b, followed by a thermal rearrangement.On irradiation of 1 with a broad-spectrum lamp, the ratio of the photoproducts exo-2 and 8 is correlated with the ratio of the pe and pa conformers of 1.The novel compound 1-(o-benzylphenyl)allene (6) is also formed under these conditions.Irradiation of 1 at 254 nm yields 8 as the only photoproduct.Photochemical addition of methanol was observed to complete with the photoprocess, leading to exo-2, though at a comparatively low level.A photodecomposition mode of exo-2, presumably involving heterolytic cleavage of the cyclopropane ring, presents the chief source of methoxylated photoproducts at low temperatures in methanol.
- Woning, Jan,Lijten, Frank A. T.,Laarhoven, Wim H.
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p. 2427 - 2435
(2007/10/02)
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- HYDROFORMYLATION OF TRICARBONYL(η-STYRENE)CHROMIUM AND RELATED COMPOUNDS
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Hydroformylation of the tricarbonylchromium derivatives of styrene, indene, and dihydronaphthalene using rhodium-based catalysts gives α-arylaldehydes with high regioselectivity and, using appropriate chiral catalysts, with enantiomeric excesses of up to
- Doyle, Michael M.,Jackson, Roy W.,Perlmutter, Patrick
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p. 5357 - 5360
(2007/10/02)
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- Photolysis of cis-1,2-Dihydroxyindane Carbonate and cis-1,2-Dihydroxy-1,2,3,4-tetrahydronaphthalene Carbonate
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Cyclic carbonate esters 2 and 3 were prepared and the photochemistry studied.The direct irradiation of these esters produces 1,3-diradicals which undergo either ring closure to form epoxides, H migration to form ketones or Grob type fragmentation processes which lead to products via ring expansion or contraction.
- White, Rick C.,Drew, Phil,Moorman, Richard
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p. 1781 - 1783
(2007/10/02)
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- Total Synthesis of the Spirans of Cannabis: Cannabispiradienone, Cannabispirenone-A and -B, Cannabispirone, α- and β-Cannabispiranols and the Dihydrophenanthrene Cannithrene-1
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O-Methylcannabispirenone has been synthesised (57percent overall from 3,5-dimethoxycinnamic acid) via 5,7-dimethoxyindanone, p-tolylsulphonylmethyl isocyanide conversion into the 1-nitrile, alkylation with 1-iodo-3,3-ethylenedioxybutane, deacetalisation, and spirocyclisation. 5,7-Dimethoxyindanone is 7-deprotected by boron trichloride with high selectivity, and re-protected as the methoxyethoxymethyl ether: following the above route, finally deprotecting by boron trichloride, gives cannabispirenone-A (2) in 21percent overall yield.O-Methylcannabispirenone can be demethylated to give (2) by lithium 1,1-dimethylethanethiolate: demethylation with boron tribromide gives cannabispirenone-B (3).Hydrogenation of synthetic cannabispirenone-A gives cannabispirone (4), reduced by borohydride to the epimeric α-(6) and β-(5) cannabispiranols, separated by h.p.l.c.Dehydrogenation of O-methylcannabispirenone with dichlorodicyanobenzoquinone, followed by lithium 1,1-dimethylethanethiolate demethylation, gives cannabispiradienone (1).Under acidic conditions, the latter undergoes dienone-phenol rearrangement to give cannithrene-1 (8), thus completing the total synthesis of the spiro-cannabinoid group of natural products discussed in the preceding paper.The unsubstituted cannabispirenone parent has also been synthesised.
- Crombie, Leslie,Tuchinda, Patoomratana,Powell, Michael J.
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p. 1477 - 1484
(2007/10/02)
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