- Synthesis of α,β-unsaturated ketones and esters using polymer-supported selenium bromide
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Treatment of the polymer-supported α-phenylseleno ketones and esters prepared from polymer-supported selenium bromide with ketone and ester enolates with hydrogen peroxide afford α,β-unsaturated ketones and esters in good yields and high purities.
- Sheng, Shou-Ri,Liu, Xiao-Ling,Wang, Xing-Cong
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- Improved Preparation of Methyl 3-Oxo-1-cyclohexene-1-carboxylate and Its Use in the Synthesis of Substituted 1,5-Cyclodecadienes
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An improved preparation of methyl 3-oxo-1-cyclohexene-1-carboxylate (6) is reported in which cyclohexanecarboxylic acid is converted to methyl 1-bromocyclohexanecarboxylate by a variation of the Hell-Volhard-Zelinsky reaction and then the bromo ester is dehydrohalogenated with quinoline and the resultant unsaturated ester is oxidized at an allylic position with chromium trioxide in acetic acid and acetic anhydride to give 6.The overall conversion proceeds in 49percent yield, which is a substantial improvement over previous attempts reported for this sequence.Photoadditionof 6 and cyclobutene-1-carboxylic acid yields adduct 8, which after esterification and thermolysis gives the 1,5-cyclodecadiene 12.In addition, reduction of adduct 8 with NaCNBH3 followed by spontaneous lactoniaztion yields 10, which upon thermolysis gives the lactone diene 11.This approach should have applications in the synthesis of germacranolides that have an ester or related carbonyl function on C(14).
- Lange, Gordon L.,Otulakowski, John A.
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- Merging Halogen-Atom Transfer (XAT) and Cobalt Catalysis to Override E2-Selectivity in the Elimination of Alkyl Halides: A Mild Route towardcontra-Thermodynamic Olefins
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We report here a mechanistically distinct tactic to carry E2-type eliminations on alkyl halides. This strategy exploits the interplay of α-aminoalkyl radical-mediated halogen-atom transfer (XAT) with desaturative cobalt catalysis. The methodology is high-yielding, tolerates many functionalities, and was used to access industrially relevant materials. In contrast to thermal E2 eliminations where unsymmetrical substrates give regioisomeric mixtures, this approach enables, by fine-tuning of the electronic and steric properties of the cobalt catalyst, to obtain high olefin positional selectivity. This unprecedented mechanistic feature has allowed access tocontra-thermodynamic olefins, elusive by E2 eliminations.
- Zhao, Huaibo,McMillan, Alastair J.,Constantin, Timothée,Mykura, Rory C.,Juliá, Fabio,Leonori, Daniele
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supporting information
p. 14806 - 14813
(2021/09/18)
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- Electrochemically driven desaturation of carbonyl compounds
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Electrochemical techniques have long been heralded for their innate sustainability as efficient methods to achieve redox reactions. Carbonyl desaturation, as a fundamental organic oxidation, is an oft-employed transformation to unlock adjacent reactivity through the formal removal of two hydrogen atoms. To date, the most reliable methods to achieve this seemingly trivial reaction rely on transition metals (Pd or Cu) or stoichiometric reagents based on I, Br, Se or S. Here we report an operationally simple pathway to access such structures from enol silanes and phosphates using electrons as the primary reagent. This electrochemically driven desaturation exhibits a broad scope across an array of carbonyl derivatives, is easily scalable (1–100 g) and can be predictably implemented into synthetic pathways using experimentally or computationally derived NMR shifts. Systematic comparisons to state-of-the-art techniques reveal that this method can uniquely desaturate a wide array of carbonyl groups. Mechanistic interrogation suggests a radical-based reaction pathway. [Figure not available: see fulltext.]
- Gnaim, Samer,Takahira, Yusuke,Wilke, Henrik R.,Yao, Zhen,Li, Jinjun,Delbrayelle, Dominique,Echeverria, Pierre-Georges,Vantourout, Julien C.,Baran, Phil S.
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p. 367 - 372
(2021/03/31)
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- Photoredox/Cobalt Dual-Catalyzed Decarboxylative Elimination of Carboxylic Acids: Development and Mechanistic Insight
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Recently, dual-catalytic strategies towards the decarboxylative elimination of carboxylic acids have gained attention. Our lab previously reported a photoredox/cobaloxime dual catalytic method that allows the synthesis of enamides and enecarbamates directly from N-acyl amino acids and avoids the use of any stoichiometric reagents. Further development, detailed herein, has improved upon this transformation's utility and further experimentation has provided new insights into the reaction mechanism. These new developments and insights are anticipated to aid in the expansion of photoredox/cobalt dual-catalytic systems.
- Cartwright, Kaitie C.,Joseph, Ebbin,Comadoll, Chelsea G.,Tunge, Jon A.
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p. 12454 - 12471
(2020/09/09)
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- Pd-Catalyzed Carbonylation of Vinyl Triflates to Afford α,β-Unsaturated Aldehydes, Esters, and Amides under Mild Conditions
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An efficient and general protocol for the synthesis of α,β-unsaturated aldehydes, esters, and amides via carbonylation of vinyl triflates including derivatives of camphor, ketoisophorone, verbenone, and pulegone was developed. Crucial for these transformations is the use of a specific palladium catalyst containing a pyridyl-substituted dtbpx-type ligand. This procedure also allows for an easy access of dicarbonylated products from the corresponding ketones.
- Zhang, Shaoke,Neumann, Helfried,Beller, Matthias
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p. 3528 - 3532
(2019/05/24)
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- Synthetic method for 3-acetoxy-2-cyclohexenyl-1-one and derivatives thereof
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The invention discloses a synthetic method for 3-acetoxy-2-cyclohexenyl-1-one and derivatives thereof. The synthetic method comprises the following steps: (1) reacting a substance as described in thespecification with nitromethane at 110 DEG C to obtain a product I as described in the specification, wherein R in the product I is H or CH3; (2) reacting the product I of the step (1) with sodium nitrite and acetic acid at 37 DEG C to obtain a product II as described in the specification; (3) reacting the product II of the step (2) with methanol and concentrated sulfuric acid at 88 DEG C to obtain a product III as described in the specification; and (4) weighing the product III of the step (3), potassium carbonate, palladium on activated carbon and t-butyl hydroperoxide, adding the weighed materials into dichloromethane, carrying out a reaction at 0 DEG C, and allowing temperature to naturally rise to room temperature so as to obtain a product IV, wherein R in the product IV is H or CH3.The synthetic method of the invention is simpler and more efficient, and has high total yield; the toxicity of reagents used in the preparation is smaller than the toxicity of m-methoxybenzoic acid, thionyl chloride and the like used in the prior art; and the method is low in cost, simple and convenient in separation and purification, applicable to large-scale preparation and capable of realizingindustrial mass production. The synthetic method is applicable as a general synthetic method for 3-acetoxy-2-cyclohexenyl-1-one and 4-substituted derivatives thereof.
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- Cyanide-Free One-Pot Synthesis of Methacrylic Esters from Acetone
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Methacrylic esters, represented by methyl methacrylate (MMA), are widely used as commodity chemicals. Here, the one-pot synthesis of methacrylic esters from acetone, a haloform and alcohols in the presence of an organic base is described. Using DBU as the organic base for the reaction of acetone, chloroform and methanol in acetonitrile afforded MMA in 66 % yield. When the solvent was replaced by benzonitrile, the product MMA was successfully purified by distillation. Applicability of this process to various alcohols was also investigated to show ethyl, phenyl, CF3CH2, and n-C6F13CH2CH2 esters were obtained in moderate yields. The use of bromoform instead of chloroform resulted in the improvement of the yield, for example, methyl and n-C6F13CH2CH2 esters up to 81 and 70 %, respectively. The reaction with deuterated starting materials acetone-d6 and MeOH-d4, with DBU in acetonitrile afforded deuterated MMA (MMA-d8) in 70 % yield.
- Koyama, Minoru,Kawakami, Takafumi,Okazoe, Takashi,Nozaki, Kyoko
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p. 10913 - 10917
(2019/08/02)
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- A new selective route towards benzoic acid and derivatives from biomass-derived coumalic acid
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The selective production of aromatics from bio-based sources is an area of interest to expand the potential for greener alternatives to petroleum-derived chemicals. A scalable, efficient route to produce bio-based benzoates is demonstrated by carrying out heterogeneous catalytic reactions in non-toxic bio-based solvents at 180°C obtaining yields of up to 100 mol%. This approach extends the 2-pyrone (coumalic acid/methyl coumalate) Diels-Alder platform by utilizing a bioavailable co-reactant ethylene. A detailed investigation using a combination of kinetic experiments, DFT calculations, and multi-dimensional NMR was carried out to determine the detailed reaction network, and the corresponding activation energies for critical steps. Additionally, a series of experiments were conducted to maximize the yields by comparing different solvents, for both coumalic acid and methyl coumalate. Our results show that the choice of solvent was a significant factor when coumalic acid was the reactant (yields 71-92 mol%), while methyl coumalate was only minimally affected by the solvent (yields 95-100 mol%). Interestingly, the reaction network and kinetic analysis showed that the Diels-Alder reactions were not significantly different between coumalic acid and methyl coumalate, with the rate limiting step for both being decarboxylation with an activation barrier of 141 kJ mol-1 compared to 77 kJ mol-1 for the formation of the bicyclic adduct. Finally, the reaction cascade was found to be highly susceptible to by-product formation when as little as 5 vol% water was present in the solvent, which demonstrates that the absence of water is essential for high yielding benzoate production.
- Pfennig, Toni,Carraher, Jack M.,Chemburkar, Ashwin,Johnson, Robert L.,Anderson, Austin T.,Tessonnier, Jean-Philippe,Neurock, Matthew,Shanks, Brent H.
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supporting information
p. 4879 - 4888
(2017/10/23)
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- Palladium-Catalyzed α,β-Dehydrogenation of Esters and Nitriles
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A highly practical and general palladium-catalyzed methodology for the α,β-dehydrogenation of esters and nitriles is reported. Generation of a zinc enolate or (cyanoalkyl)zinc species followed by the addition of an allyl oxidant and a palladium catalyst results in synthetically useful yields of α,β-unsaturated esters, lactones, and nitriles. Preliminary mechanistic investigations are consistent with reversible β-hydride elimination and turnover-limiting, propene-forming reductive elimination.
- Chen, Yifeng,Romaire, Justin P.,Newhouse, Timothy R.
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supporting information
p. 5875 - 5878
(2015/05/27)
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- NMR studies on [2+3] cycloaddition of nitrile oxides to cyclohexene derivatives
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Site selectivity, regioselectivity and stereoselectivity of [2+3] cycloaddition of 4-trifluoromethylbenzonitrile oxide to cyclohexene carboxylates substituted with alkenyl functions were examined. Site selectivity was correlated with electron charges of alkenyl carbon atoms. Structure of the products has been established by an extensive application of 2D 1H and 13C NMR spectroscopy and electrospray ionization mass spectrometry.
- Gucma, Miros?aw,Go??biewski, W. Marek,Michalczyk, Alicja K.
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p. 223 - 232
(2014/02/14)
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- Iridium(I)-catalyzed vinylic C-H borylation of 1-cycloalkenecarboxylates with bis(pinacolato)diboron
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Ir(i)-catalyzed C-H borylation of 1-cycloalkenecarboxylic derivatives with bis(pinacolato)diboron affords various alkenylboronates with functional groups in excellent yields. This reaction was also used in a one-pot borylation/Suzuki-Miyaura cross-coupling procedure.
- Sasaki, Ikuo,Doi, Hana,Hashimoto, Toshiya,Kikuchi, Takao,Ito, Hajime,Ishiyama, Tatsuo
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supporting information
p. 7546 - 7548
(2013/08/23)
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- Non-Cp titanium alkoxide-based homolytic ring-opening of epoxides by an intramolecular hydrogen abstraction in β-titanoxy radical intermediates
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A low-valent titanium species derived in situ from Ti(O-i-Pr)4, Me3SiCl and Mg powder in tetrahydrofuran reacted with epoxides to selectively provide less hindered alcohols via a homolytic ring-opening of epoxides, in which the intermediate β-titanoxy radical intramolecularly abstracted a hydrogen atom from an alkoxy moiety in the titanium complexes.
- Kawaji, Tsuyoshi,Shohji, Noriaki,Miyashita, Kenji,Okamoto, Sentaro
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p. 7857 - 7859
(2011/09/15)
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- Electroreduction of organic compounds, 36 [1]. Electroreduction of chlorinated methyl benzoates
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The preparative electroreduction of the three methyl monochlorobenzoates, the six methyl dichlorobenzoates, and methyl 2,3,4-trichlorobenzoate in different solvent-supporting electrolytes (SSE) was studied. The rate of the dechlorination, which is the main reaction, is dependent on the substitution pattern. Pronounced regioselectivity is therefore observed in case of the oligochloro derivatives. Hydrogenation of the benzene ring and reduction of the methoxycarbonyl group with formation of a hydroxymethyl group are observed as side-reactions. Quantum chemical calculations on the reaction mechanism were performed. The theoretical results are in accordance with the experimental observations.
- Gassmann, Joerg,Voss, Juergen
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body text
p. 1291 - 1299
(2009/06/19)
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- α-Hydroxylation of carbonyls using iodine
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The α-hydroxylation of ketones and aldehydes to α-hydroxyketals mediated by iodine under basic conditions in MeOH is described. Enolates generated under the reaction conditions are iodinated and the resulting α-iodocarbonyl is transformed into the hydroxyketal. The use of iodine for this chemistry represents an economical and practical alternative to existing methods for this transformation.
- Zacuto, Michael J.,Cai, Dongwei
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p. 447 - 450
(2007/10/03)
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- Indirect electrochemical oxidation of cyclic ketones: Influence of ring size, mediator and supporting electrolyte on the result of the reaction
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The result of the indirect electrochemical oxidation of cyclic ketones in methanol in an undivided cell in the presence of sodium halides depends on the ring size of ketone and the type of mediator. Selectivity of the reaction in some cases and current efficiency are increased by addition of supporting electrolyte - sodium hydroxide. Formation of cyclic 2,2-dimethoxycycloalkanols and the electrochemically induced Favorskii rearrangement with the formation of methyl cycloalkencarboxylates containing in the ring one carbon atom less than starting ketone are the main ways of the indirect electrochemical oxidation of cyclic ketones.
- Barba, Fructuoso,Elinson, Michail N.,Escudero, Jose,Feducovich, Sergey K.
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p. 4427 - 4436
(2007/10/03)
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- Synthesis and some reactions of 1-(trimethoxymethyl)cyclohexene
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1-(Trimethoxymethyl)cyclohexene (11) was synthesized in three steps from N-methyl-N-phenylcyclohex-1-ene-1-carboxamide (8). Reaction of the α,β-unsaturated ortho ester (11) with sodium hydride and N-methylaniline gave a 1:1 mixture of methyl cyclohex-1-ene-1-carboxylate (15) and N,N-dimethylaniline. Treatment of (11) with 3-methoxyphenol gave 1-[dimethoxy(3′-methoxyphenoxy)methyl]cyclohexene (10) which underwent thermolysis at 250° to give 1,3-dimethoxybenzene (16) and methyl cyclohex-1-ene-1-carboxylate (15).
- Bourke, David G.,Collins, David J.
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p. 1287 - 1291
(2007/10/03)
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- Indirect electrochemical oxidation of cyclic ketones: Strong influence of ring size on the result of the reaction
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The result of the indirect electrochemical oxidation of cyclic ketones in methanol in the undivided cell in the presence of sodium iodide depends on the ring size. Cyclopentanone affords 2,2-dimethoxycyclopentanone. While cyclohexanone gives rise 2,2-dimethoxycyclo-hexanol, and cyclic ketones with higher ring size undergo new type of the electrochemically induced Favorskii rearrangement with the formation of methyl cycloalkencarboxylates containing in the ring on the one carbon atom less than starting ketone. So the simple electrocatalytic system can distinguish the ring size of cyclic ketones.
- Barba, Fructuoso,Elinson, Michail N.,Escudero, Jose,Feducovich, Sergey K.
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p. 5759 - 5762
(2007/10/03)
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- A New Indirect Application of Aggregative Activation: Synthesis of Esters by Cobalt-Catalyzed Carbonylation of Aryl, Heterocyclic, and Vinyl Halides under Atmospheric Pressure
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Sun lamp illuminated alkoxycarbonylation of aryl, heteroaryl, and vinyl halides was performed under atmospheric pressure of CO in the presence of a cobalt catalyst in situ generated from Co(OAc)2.Illunination through a Pyrex flask was sufficient to catalyze the reaction.This process avoids the use of Co2(CO)8 and excess CH3I, which were required in the earlier procedure.A SRN1 mechanism is proposed.
- Marchal, Joel,Bodiguel, Jacques,Fort, Yves,Caubere, Paul
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p. 8336 - 8340
(2007/10/02)
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- A convenient synthesis of aziridine-2-carboxylic esters
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Optically active oxirane-2-carboxylic esters, prepared from allylic alcohols employing the Sharpless epoxidation, were treated with sodium azide.The azido alcohols obtained were subsequently converted into aziridine-2-carboxylic esters by reaction with triphenylphosphine, in good yields and with high optical purity.Various racemic oxirane-2-carboxylic esters were subjected to the same sequence of reactions.
- Legters, Johan,Thijs, Lambertus,Zwanenburg, Binne
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- NEW SYNTHETIC METHODS FOR α,β-UNSATURATED KETONES, ALDEHYDES, ESTERS AND LACTONES BY THE PALLADIUM-CATALYZED REACTIONS OF SILYL ENOL ETHERS, KETENE SILYL ACETALS, AND ENOL ACETATES WITH ALLYL CARBONATES
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Silyl enol ethers and ketene silyl acetals derived from ketones, aldehydes, esters and lactones are converted into α,β-unsaturated ketones, aldehydes and lactones by treatment with allyl carbonates in high yields using the palladium-bis(diphenylphosphino)ethane (dppe) complex as catalyst.Phosphine-free palladium catalyst instead of the palladium-phosphine complex gives a higher selectivity for the preparation of cyclopentenone, cyclooctenone, dienones, α,β-unsaturated esters and lactones.As a solvent, the use of nitriles such as acetonitrile is essential.In other solvents, allylation takes place.Enol acetates derived from ketones are converted into α,β-unsaturated ketones by reaction with allyl carbonate in acetonitrile using the palladium complex and tributyltin methoxide as bimetallic catalysts.
- Minami, Ichiro,Takahashi, Kazuhiko,Shimizu, Isao,Kimura, Tsuneo,Tsuji, Jiro
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p. 2971 - 2978
(2007/10/02)
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- Complex Catalysis with Technetium Compounds. Hydroformylation with Technetiumcarbonyl Catalysts
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The hydroformylation reaction of cyclohexene (1), propene (2) and 1-octene (3) was studied using Tc2(CO)10 and Tc(CO)10/P(n-C4H9)3, resp., as catalysts in solution.For comparison experiments have also been made with Mn2(CO)10, Mn2(CO)10/P(n-C4H9)3 and Re2(CO)10/P(n-C4H9)3 as catalysts for the hydroformylation of 1.There is always a competition between hydrogenation and hydroformylation.Tc2(CO)10/P(n-C4H9)3 gave the best results in activity and selectivity within the subgroup VII complexes studied, but is a rather poor catalyst compared with the cobalt or rhodium compounds.
- Kaden, L.,Lorenz, B.,Wahren, M.
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p. 407 - 412
(2007/10/02)
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- PALLADIUM-CATALYZED PREPARATION OF α-ALLYL ESTERS AND α,β-UNSATURATED ESTERS FROM SATURATED ESTERS VIA THEIR KETENE SILYL ACETALS
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Reaction of ketene silyl acetals with allylic carbonates in the presence of palladium-phosphine catalyst in dioxane gives α-allyl esters in high yields.When the reaction is carried out with phosphine-free palladium catalyst in nitriles, α,β-unsaturated esters are obtained in good yields.
- Tsuji, Jiro,Takahashi, Kazuhiro,Minami, Ichiro,Shimizu, Isao
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p. 4783 - 4786
(2007/10/02)
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- Polarized Ketene Dithioacetals. 28. A New General Highly Stereoselective and Regiospecific Method for Homologation of Ketones to α,β-Unsaturated Esters via α-Oxoketene Dithioacetals
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A new highly stereoselective and regiospecific general method for the conversion of active methylene ketones to α,β-unsaturated O-methyl esters, S-methyl esters, and aldehydes via the corresponding oxoketene dithioacetals has been developed.Thus the carbinols 7a-g obtained by sodium borohydride reduction of the corresponding oxoketene dithioacetals 6a-g, derived from acetophenones and their higher homologues, have been shown to undergo boron trifluoride etherate assisted methanolysis to give the corresponding (E)-methylcinnamates 3a-d and their α-alkyl derivatives 3e-g in high yields.Also the acetals 6h-k derived from alkylmethyl ketones gave the corresponding (E)-methylcrotonates 3h-k.Similarly, the acetals 6l-p derived from alicyclic ketones gave the corresponding cyclic ene esters 3l-p under identical conditions.A few carbinols, 7a-d, were shown to undergo partial hydrolysis in the presence of boron trifluoride etherate/water to give the corresponding S-methyl thiocinnamates 8a-d.The cyclic acetals 6l-n were also similarly converted to the corresponding cyclic S-methylene thio esters 8e-g.The (methylthio)alkenyl ketones 20a-d and 18 after borohydride reduction and acidic hydrolysis gave the corresponding (E)-α,β-unsaturated aldehydes 22a-d and 19.The mechanism governing these transformations has been proposed.
- Myrboh, Bekington,Ila, Hiriyakkanavar,Junjappa, Hiriyakkanavar
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p. 5327 - 5332
(2007/10/02)
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- Synthesis and Rearrangement of 1-Substituted Bicyclohexanes
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Starting from 7-oxobicycloheptane-1-carbonyl chloride (3), bicyclohexane-1-carboxylic acid (9) was prepared via Hunsdiecker degradation and Favorskii rearrangement.The conversion of 9 to 1-methoxybicyclohexane (15) via methyl ketone 12 and acetate 13 was complicated by the facile homoketonization of the elusive bicyclohexane-1-ol (14).Similarly, bicyclohexane-1-amine readily underwent hydrolysis whereas N,N-dimethylbicyclohexane-1-amine (17) proved to be more resistant.Thermolysis of methyl bicyclohexane-1-carboxylate (10) revealed a "normal" rate enhancement (ΔEa ca. 6 kcal/mol = 25 kJ/mol).The effects of 1-acetoxy, 1-methoxy and 1-dimethylamino groups on the rate of rearrangement were unexpectedly small.
- Kirmse, Wolfgang,Sandkuehler, Peter
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p. 1394 - 1406
(2007/10/02)
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- Preparation of organic acids and/or esters
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Carboxylic acids and/or esters are prepared by converting the STR1 moiety in a 1-substituted 2,2-trihaloethanol, or derivative wherein X represents halogen and R is hydrogen or an acyl group to an organic acid and/or ester grouping of the formula STR2 wherein R' is hydrogen or alkyl of 1 to 6 carbon atoms, in the process which comprises reacting the 1-substituted 2,2,2-trihaloethanol or acylated derivative with molecular oxygen in the presence of a catalyst comprising a complex of a transition metal having an atomic number from 21-30, 39-48 or 57-80 and at least one molecule of a ligand containing trivalent nitrogen, phosphorus, arsenic or antimony. This reaction is carried out in a reaction medium comprising an alcohol or aqueous alcohol having 1 to 6 carbon atoms optionally containing an alkali metal, said alcoholic solvent also serving as a reactant source when carboxylic acid esters are formed.
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