- Alkylation via tris(dialkylamino)sulfonium enolates
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Tris(dialkylamino)sulfonium enolates generated from tris(diethylamino)sulfonium difluorotrimethylsiliconate and enol silyl ethers are readily alkylated by various alkyl halides under mild conditions.
- Noyori,Nishida,Sakata
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- Cerium(III) Chloride Mediated Michael Addition of RMgX to Nitroenes: a Very Efficient Access to Complex Nitroalkanes
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Reactions of RMgX-CeCl3 complexes with nitroenes lead to functionalized nitroalkanes in very good yields.
- Bartoli, Giuseppe,Bosco, Marcella,Sambri, Letizia,Marcantoni, Enrico
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- Resolution of Racemic ε-Lactones
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Kinetic resolution of racemic ε-lactones by Pig Liver Esterase give optically active R (+) ε-lactones.When alkyl group is higher than propyl, Horse Liver Esterase leads to the destruction of the opposite enantiomer.Enantiomeric excess is easily evaluated by G.C. on a chiral stationary phase.
- Fellous, R.,Lizzani-Cuvelier, L.,Loiseau, M. A.,Sassy, E.
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- One-pot synthesis of 2-alkyl cycloketones on bifunctional Pd/ZrO2 catalyst
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2-Alkyl cycloketones are essential chemicals and intermediates for synthetic perfumes and pesticides, which are conventionally produced by multistep process including aldol condensation, separation and hydrogenation. In present work, a batch one-pot cascade approach using aldehydes and cycloketones as the raw materials, and a bifunctional Pd/ZrO2 catalyst was developed for the synthesis of 2-alkyl cycloketones, e.g., cyclohexanone and cycloheptanone. Very high aldehydes (except for paraldehyde with large steric hindrance) conversion and high yields for 2-alkyl cycloketones (e.g., 99 % of conversion for n-butanal and 76 wt.% of yield for 2-butyl cyclohexanone) were obtained at mild temperature of 140 °C. After 10 cycles of reuse, Pd/ZrO2 catalyst showed slight deactivation (ca. 5 % conversion and 10 % yield losses), due to the coke on the catalyst. However, the performance of the catalyst was completely recovered after an oxidative regeneration.
- Xue, Weiyang,Gu, Bin,Wu, Huiling,Liu, Mengyang,He, Songbo,Li, Jingmei,Rong, Xin,Sun, Chenglin
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- A milk lactone perfume continuous compound into method (by machine translation)
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The invention belongs to the technical field of synthetic perfume, and in particular relates to a milk lactone perfume continuous compound into a method, including the role of the alkali under the condition of the aldol reaction, then by hydrogenation reaction, Baeyer - Villiger oxidation, acid continuous hydrolysis, dehydrating and gets milk lactone perfume; the aldol condensation reactions include: part of the as a footing of a cyclohexanone with a alkali mixing, heating processing, the rest [...] butyraldehyde mixture of cyclohexanone with, side drop edge added stirring, and after dropping to continue stirring, thermal insulation reaction-butyraldehyde content to 1% following the end of the reaction; static divider separating the oil, collected and recycled water; collecting oil layer after washing the processing and then transferred to the distillating still distillation recovery excessive cyclohexanone mechanically, the collection of the condensation product of the pan bottom; the invention by adding cyclohexanone in a different way, improving the yield of the aldol condensation reaction; and, of the present invention under the conditions of reaction temperature, can step from an aldol condensation product. (by machine translation)
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- A ε - decalactone with synthetic perfume production method (by machine translation)
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The invention belongs to the technical field of spice production, and in particular relates to relates to a ε - decalactone with synthetic perfume production method, including: (1) preparing an aqueous alkali; (2) the preparation of cyclohexanone and butyraldehyde mixture A; (3) the alkali is added to the reactor, the footing cyclohexanone is added to the mix in the reactor; (4) is added to the mixture in the reactor A drop, side drop edge added stirring, after dropping to continue stirring, thermal insulation to react to the detected in-butyraldehyde content of 1% until the following; (5) the step (4) and the product and sequentially through the hydrogenation, separation and purification, oxidation, obtained after the separation and purification of the ε - decalactone synthetic perfume; the invention to butyraldehyde and cyclohexanone as the starting material to aldol condensation reaction, and then after hydrogenation of peracetic acid oxidation ring enlargement reaction synthesis ε - decalactone perfume, to excessive cyclohexanone as the reaction solvent, recovery after mechanically, reduce the reaction solvent separation and purification, and raw materials are easy, the reaction yield is high. (by machine translation)
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- Synthetic method of epsilon-decalactone perfume
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The invention belongs to the technical field of perfume synthesis, and particularly relates to a synthetic method of epsilon-decalactone perfume. The synthetic method comprises the following steps: (1) mixing an alkaline solution with a part of cyclohexanone, then dropwise adding a mixture of n-butyraldehyde and the rest of cyclohexanone into the mixture, carrying out stirring, and carrying out heat preservation for a reaction; (2) standing the reactants in the step (1), collecting a water layer, collecting an oil layer, and washing the oil layer with water to obtain a condensed product 2-butenyl cyclohexanone crude product; (3) carrying out distilling to recover cyclohexanone to obtain 2-butenyl cyclohexanone; (4) carrying out a hydrogenation reaction; (5) collecting a liquid-phase intermediate product 2-butyl cyclohexanone crude product, and carrying out distilling to obtain 2-butyl cyclohexanone; (6) carrying out an oxidation reaction; and (7) carrying out distilling purification toobtain the epsilon-decalactone perfume product. According to the invention, the cyclohexanone is added into the reaction system in different ways, the excess cyclohexanone is used as a reaction solvent through a stirring dripping technology, and the cyclohexanone is reused after being recycled, so that separation and purification processes of the reaction solvent are reduced, and a high reactionyield is ensured.
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- Investigating: Saccharomyces cerevisiae alkene reductase OYE 3 by substrate profiling, X-ray crystallography and computational methods
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Saccharomyces cerevisiae OYE 3 shares 80% sequence identity with the well-studied Saccharomyces pastorianus OYE 1; however, wild-type OYE 3 shows different stereoselectivities toward some alkene substrates. Site-saturation mutagenesis of Trp 116 in OYE 3 followed by substrate profiling showed that the mutations had relatively little effect, opposite to that observed previously for OYE 1. The X-ray crystal structures of unliganded and phenol-bound OYE 3 were solved to 1.8 and 1.9 ? resolution, respectively. Both structures were nearly identical to that of OYE 1, with only a single amino acid difference in the active site region (Ser 296 versus Phe 296, part of loop 6). Despite their essentially identical static X-ray structures, molecular dynamics (MD) simulations revealed that loop 6 conformations differed significantly in solution between OYE 3 and OYE 1. In OYE 3, loop 6 remained nearly as open as observed in the crystal structure; by contrast, loop 6 closed over the active site of OYE 1 by ca. 4 ?. Loop closure likely generates a greater number of active site protein contacts for substrate bound to OYE 1 as compared to OYE 3. These differences provide an explanation for the differing stereoselectivities of OYE 3 and OYE 1, despite their nearly identical X-ray crystal structures.
- Powell, Robert W.,Buteler, M. Pilar,Lenka, Sunidhi,Crotti, Michele,Santangelo, Sara,Burg, Matthew J.,Bruner, Steven,Brenna, Elisabetta,Roitberg, Adrian E.,Stewart, Jon D.
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p. 5003 - 5016
(2018/10/17)
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- Versatile CuI/Pd0 dual catalysis for the synthesis of quaternary α-allylated carbonyl compounds: Development, mechanistic investigations and scope
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We report herein a versatile cooperative dual catalysis reaction based on a CuI/Pd0 system. Mechanistic investigation shows that every component plays a crucial role in determining the reaction outcome. The reaction is successfully extended to various substrates; such as α,β-unsaturated ketones, malonates and coumarins. The strategy tolerates different substitution patterns and affords good yields for each family of substrates.
- Nahra, Fady,Mace, Yohan,Boreux, Arnaud,Billard, Francois,Riant, Olivier
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p. 10970 - 10981
(2014/09/17)
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- Direct α-alkylation of ketones with alcohols in water
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The direct α-alkylation of ketones with alcohols has emerged as a new green protocol to construct C-C bonds with H2O as the sole byproduct. In this work, a very simple and convenient Pd/C catalytic system for the direct a-alkylation of ketones with primary alcohols in pure water is developed. Based on this catalytic system, aqueous mixtures of dilute acetone, 1-butanol, and ethanol (mimicking ABE fermentation products) can be directly transformed into C5-C11 or longer-chain ketones and alcohols, which are precursors to fuels.
- Xu, Guoqiang,Li, Qiong,Feng, Jiange,Liu, Qiang,Zhang, Zuojun,Wang, Xicheng,Zhang, Xiaoyun,Mu, Xindong
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p. 105 - 109
(2014/03/21)
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- Pichia stipitis OYE 2.6 variants with improved catalytic efficiencies from site-saturation mutagenesis libraries
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An earlier directed evolution project using alkene reductase OYE 2.6 from Pichia stipitis yielded 13 active site variants with improved properties toward three homologous Baylis-Hillman adducts. Here, we probed the generality of these improvements by testing the wild-type and all 13 variants against a panel of 16 structurally-diverse electron-deficient alkenes. Several substrates were sterically demanding, and as hoped, creating additional active site volume yielded better conversions for these alkenes. The most impressive improvement was found for 2-butylidenecyclohexanone. The wild-type provided less than 20% conversion after 24 h; a triple mutant afforded more than 60% conversion in the same time period. Moreover, even wild-type OYE 2.6 can reduce cyclohexenones with very bulky 4-substituents efficiently.
- Patterson-Orazem, Athéna,Sullivan, Bradford,Stewart, Jon D.
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p. 5628 - 5632
(2015/01/09)
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- The reactivity of potassium carbanions with epoxides
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Cyclohexene oxide reacted with n-butylpotassium unexpectedly to produce 2-butylcyclohexanone in a 10% isolated yield of its semicarbazone derivative. Based on previous literature, a three-part mechanism is proposed that implies that a yield greater than 33% is not possible. Copyright
- Dorado, Christina,Salvador, James M.
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p. 2314 - 2318
(2013/07/26)
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- DEHYDROGENATION OF CYCLOHEXANONE TO PRODUCE PHENOL
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In a process for the dehydrogenation of cyclohexanone to produce phenol, a feed comprising cyclohexanone is contacted with a dehydrogenation catalyst under dehydrogenation conditions comprising a temperature of less than 4000C and a pressure of less than 690 kPa, gauge, such 0.1 to 50 wt% of the cyclohexanone in said feed is converted to phenol and the dehydrogenation product contains less than 100 ppm by weight of alkylbenzenes.
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Page/Page column 23; 25
(2011/09/14)
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- Palladium-catalyzed intramolecular hydroalkylation of alkenyl- β-keto esters, α-aryl ketones, and alkyl ketones in the presence of Me 3SiCl or HCI
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Reaction of 3-butenyl β-keto esters or 3-butenyl α-aryl ketones with a catalytic amount of [PdCl2(CH3CN)2] (2) and a stoichiometric amount of Me3SiCl or Me3SiCl/ CuCl2 in dioxane at 25-70°C formed 2-substituted cyclohexanones in good yield with high regioselectivity. This protocol tolerated a number of ester and aryl groups and tolerated substitution at the allylic, enolic, and cis and trans terminal olefinic positions. In situ NMR experiments indicated that the chlorosilane was not directly involved in palladium-catalyzed hydroalkylation, but rather served as a source of HCl, which presumably catalyzes enolization of the ketone. Identification of HCl as the active promoter of palladium-catalyzed hydroalkylation led to the development of an effective protocol for the hydroalkylation of alkyl 3-butenyl ketones that employed sub-stoichiometric amounts of 2, HCl, and CuCl2 in a sealed tube at 70°C.
- Han, Xiaoqing,Wang, Xiang,Pei, Tao,Widenhoefer, Ross A.
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p. 6333 - 6342
(2007/10/03)
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- Catalytic cross-coupling of alkylzinc halides with α-chloroketones
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The cross-coupling of alkylzinc halides with α-chloroketones catalyzed by Cu(acac)2 is described. Using this method, primary and secondary alkyl groups are introduced adjacent to a ketone carbonyl under mild reaction conditions and in good yield. Cyclic, acyclic, aromatic, and aliphatic α-chloroketones are suitable substrates. Optically active α-chloroketones are converted to optically active products. The reaction was found to proceed stereospecifically with inversion of stereochemistry. The reaction is proposed to occur by direct substitution of the chloride with the alkyl group of an organocopper, -magnesium, or -zinc species. Copyright
- Malosh, Chrysa F.,Ready, Joseph M.
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p. 10240 - 10241
(2007/10/03)
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- Assessing the Substrate Selectivities and Enantioselectivities of Eight Novel Baeyer-Villiger Monooxygenases toward Alkyl-Substituted Cyclohexanones
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Genes encoding eight Baeyer-Villiger monooxygenases have recently been cloned from bacteria inhabiting a wastewater treatment plant. We have carried out a systematic investigation in which each newly cloned enzyme, as well as the cyclohexanone monooxygenase from Acinetobacter sp. NCIB 9871, was used to oxidize 15 different alkyl-substituted cyclohexanones. The panel of substrates included equal numbers of 2-, 3-, and 4-alkyl-substituted compounds to probe each enzyme's stereoselectivity toward a homologous series of synthetically important compounds. For all 4-alkyl-substituted cyclohexanones tested, enzymes were discovered that afforded each of the corresponding (S)-lactones in ≥98% ee. This was also true for the 2-alkyl-substituted cyclohexanones examined. The situation was more complex for 3-akyl-substituted cyclohexanones. In a few cases, single Baeyer-Villiger monooxygenases possessed both high regio- and enantioselectivities toward these compounds. More commonly, however, they showed only one type of selectivity. Nonetheless, enzymes with such properties might be useful as parts of a two-step bioprocess where an initial kinetic resolution is followed by a regioselective oxidation on the isolated, optically pure ketone.
- Kyte, Brian G.,Rouviere, Pierre,Cheng, Qiong,Stewart, Jon D.
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- Palladium-catalyzed intramolecular hydroalkylation of unactivated olefins with dialkyl ketones
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(Matrix presented) Treatment of 3-butenyl heptyl ketone with substoichiometric amounts of PdCl2(CH3CN)2 (10 mol%), HCl (0.1 equiv), and CuCl2 (0.3 equiv) in dioxane at 70°C for 12 h in a sealed tube formed 2-hexylcyclohexanone in 77% isolated yield. A number of alkyl 3-butenyl ketones underwent hydroalkylation under these conditions to form 2-substituted cyclohexanones in moderate to good yield.
- Wang, Xiang,Pei, Tao,Han, Xiaoqing,Widenhoefer, Ross A.
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p. 2699 - 2701
(2007/10/03)
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- Amidino derivatives useful as nitric oxide synthase inhibitors
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The current invention discloses useful pharmaceutical compositions containing amidino derivative useful as nitric oxide synthase inhibitors.
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- Amidino dervatives useful as nitric oxide synthase inhibitors
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The current invention discloses useful pharmaceutical compositions containing azepine derivatives useful as nitric oxide synthase inhibitors.
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- Synthesis of 2-Alkylcyclohexanones Using Solvent-free Conditions and Microwave Technology
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An expeditious solvent-free route to 2-alkylcyclohexanones from 2-ethoxycarbonylcyclohexanone is described via a solid-liquid phase transfer catalysed alkylation using ButOK as base and Aliquat 336 as catalyst and a LiBr-H2O-NBu4Br induced dealkoxycarbonylation under microwave activation in a focused open-vessel Maxidigest system.Yields were >/= 75percent over two steps.
- Barnier, Jean Pierre,Loupy, Andre,Pigeon, Philippe,Ramdani, Mohamed,Jacquault, Patrick
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p. 397 - 398
(2007/10/02)
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- The alkylation of silyl enol ethers with SN1-unreactive iodides in the presence of silver trifluoroacetate
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Silyl enol ethers can be effectively alkylated with primary n-alkyl iodides in the presence of silver trifluoro-acetate to give monoalkyl ketones.
- Jefford, Charles W.,Sledeski, Adam W.,Lelandais, Patrick,Boukouvalas, John
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p. 1855 - 1858
(2007/10/02)
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- Gas Chromatography/Electron Impact Mass Spectrometry Applied to the Differentiation of the Positional Isomers of Long-chain n-Alkylcyclohexanones
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The influence of n-butyl group position upon the fragmentation behaviour of the three isomeric n-butylcyclohexanones was studied.The different fragmentation processes are described and have been applied to the differentation of the positional isomers of long-chain n-alkylcyclohexanones.In the case of the 4-n-alkyl isomers, an interesting mechanism involving a recyclization is proposed and substantiated by deuterium labelling.
- Rontani, J.-F.,Giusti, G.
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p. 773 - 776
(2007/10/02)
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- α-ALKYLATION AND α-ALKYLIDENATION OF CARBONYL COMPOUNDS BY O-SILYLATED ENOLATE PHENYLTHIOALKYLATION
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For many reactions next to a carbonyl group, the use of O-silylated enolate chemistry offers improvements in yield and selectivity over the corresponding reactions of Group I metal enolates.In the case of α-alkylation of carbonyl compounds, Lewis acid (TiCl4 or ZnBr2) promoted phenylthioalkylation of O-silylated enolates 3 by α-chlorosulphides 4 (R3=H, Me, Prn, Pri, Bui, and Me3Si), followed by reductive sulphur removal by Raney nickel, 5->6, is found to be a reliable method for this synthetically important C-C bond forming step.An alternative sulphur elimination pathway via the sulphoxide, 5->7, allows the regio- and stereocontrolled α-alkylidenation of carbonyl compounds.The phenylthioalkylation reaction is applicable to ketones, aldehydes, esters, and lactones.
- Paterson, Ian
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p. 4207 - 4220
(2007/10/02)
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- Oxidation of Secondary Alcohols with t-Butyl Hypochlorite in the Presence of Pyridine
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When treated with t-butyl hypochlorite and pyridine in methylene dichloride, secondary alcohols give the corresponding ketones in very high yield.The relative reactivities of a number of p-substituted 1-phenylethanols containing electron-donating and -withdrawing substituents were investigated.Oxidation of cis- and trans-4-t-butylcyclohexanol, as well as some other cycloalkanols, proceeds with the same relative rate.On the basis of this and other data a cyclic transition state and loss of α-hydrogen of the starting alcohols as hydride ion are proposed as characteristics of the reaction mechanism.
- Milovanovic, Jovan N.,Vasojevic, Miorad,Gojkovic, Svetislav
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p. 533 - 536
(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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- One-pot Synthesis of 2-Substituted Cyclohexanones
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The one-pot synthesis of 2-substituted cyclohexanones involves alkylation of 2-hydroxymethylenecyclohexanone (1) in the presence of solid KOH
- Ravikumar, V. T.,Sathyamoorthi, G.,Thangaraj, K.,Rajagopalan, K.
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- Hydroboration. 67. Cyclic Hydroboration of Acyclic α,ω-Dienes with 9-Borabicyclononane/Borane-Dimethyl Sulfide
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Hydroboration of acyclic α,ω-dienes, 1,3-butadiene, 1,4-pentadiene, 1,5-hexadiene, 1,7-octadiene, 1,8-nonadiene, 1,9-decadiene, 1,11-dodecadiene, and 1,13-tetradecadiene, with 2 molar equiv of 9-borabicyclononane (9-BBN), followed by redistribution of the resulting dumbbell-shaped trialkylboranes with 1 molar equiv of borane-methyl Sulfide complex (BMS), has been investigated.With 1,3-butadiene, the initial redistribution product, the five-membered boracyclane, borolane, underwent a rapid ring-opening reaction to give the known 1,6-diboracyclodecane. 1,4-Pentadiene and 1,5-hexadiene afforded the corresponding boracyclanes, borinane and borepane, in quantitative yields.With all other dienes, the initial redistribution products were polymeric.They were converted to the methyl esters by treatment with methanol, and these products were depolymerized into cyclic derivatives in 88-98percent yield by vacuum distillation at 175-200 deg C.In every case the cyclization was accompanied by varying amounts of isomerization so that the major products were both the parent B-methoxyboracyclane and the corresponding B-methoxy-2-n-alkylborinane.Thus, 1,6-heptadiene afforded B-methoxyborocane and B-methoxy-2-ethylborinane in 3:1 ratio and a total yield of 95percent.With 1,7-octadiene, 1,8-nonadiene, 1,9-decadiene and 1,11-dodecadiene, the isomerized product constituted the major constituent of the distillate. 1,13-Tetradecadiene afforded the parent boracyclane and the isomer in a 47:53 ratio and a combined yield of 82percent.The B-methoxyboracyclanes were converted to the corresponding cyclic ketones by the DCME reaction in 55-65percent yield.
- Brown, Herbert C.,Pai, Ganesh G.,Naik, Ramachandra G.
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p. 1072 - 1078
(2007/10/02)
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- Five-membered ring spiro-annulation via thermal rearrangement of enol silyl ethers of 2-(cyclopropylmethylene)cycloalkanones. A formal total synthesis of some spirovetivane-type sesquiterpenoids
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Treatment of the 2-(iodomethylene)cycloalkanones 10 and 11 with lithium (phenylthio)(cyclopropyl)cuprate provided good yields of the corresponding β-cyclopropyl enones 12 and 13, respectively.Thermolysis of the latter substances produced relatively poor yields of the desired spiro-annulation products 14 and 15.However, conversion of 12 and 13 into the corresponding enol silyl ethers 24 and 25, followed by thermal rearrangement of the latter materials and acid hydrolysis of the resulting products, provided synthetically useful yields of the spiro enones 14 and 15.Cuprous iodide-catalyzed addition of methyl magnesium iodide to 2-cyclohexen-1-one, followed by trapping of the resultant enolate anion with cyclopropanecarboxaldehyde, provided the ketols 38, which could be converted into the mixture of enol silyl ethers 34 and 35.Thermal rearrangement of the latter substances gave, after acid hydrolysis of the crude thermolysate, the spiro enones 42 and 43 in a ratio of ca. 2.5 : 1 (57 percent yield).Treatment of 42 with methyllithium in ether gave the tertiary alcohols 44 and 45 (ratio ca. 4 : 1).Hydroboration (disiamylborane, tetrahydrofuran; H2O2, NaOH) of 44, followed by oxidation of the resultant diol 46 with pyridinium chlorochromate, provided the ketol 47.A similar sequence of reactions converted the olefinic alcohol 45 into the ketol 49.Dehydration (p-toluenesulfonic acid in benzene) of 47 gave the spiro enones 28 and 48, in a ratio of ca. 9 : 1.Compound 28, also prepared previously from the ketol 49, had been converted earlier into the spirovetivane-type sesquiterpenoids (+/-)-α-vetispirene (29), (+/-)-vetivone (30), (+/-)-hinesol (31), (+/-)-hinesol acetate (32), and (+/-)-agarospirol (33).
- Piers, Edward,Lau, Cheuk Kun,Nagakura, Isao
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p. 288 - 297
(2007/10/02)
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- β-Fisson of 9-Decalinoxyl Radicals: Reversible Formation of 6-Ketocyclodecyl Radical
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Rearrangement at 0 deg C of trans-9-decalinyl hypobromide (1trans, X=Br), formed by interaction of 1trans (X=H) with bromine and silver acetate or mercuric oxide, gives 6-bromocyclodecanone(4, X=Br) whereas the same reaction at 81 deg C gives 2-(4-bromobutyl)cyclohexanone (6, X=Br).The cis isomer (1cis, X=Br) behaves similarly.The relative yields of the nitroso dimers, 11, 12, and 13, formed by photolysis of 1cis (X=NO) and 1trans (X=NO), also depend on the reaction temperature.Reduction of 6-bromocyclodecanone (4, X=Br) with tribytylstannane in high concentration gives mainly cis- and trans-9-decalinol, with the former predominating.These results indicate (i) that 9,10-bond fisson of the 9-decalinoxyl radicals, 2cis and 2trans, is rapid but reversible, (ii) that 1,9-bond fisson of 2cis and 2trans is relatively slow and is essentially irreversible under the conditions used here, and (iii) that ring closure of the radical (5) favors formation of the cis product (2cis).
- Beckwith, Athelstan L.J.,Kazlauskas, Rymantas,Syner-Lyons, Mark R.
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p. 4718 - 4722
(2007/10/02)
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- Tris(dialkylamino)sulfonium Enolates. Synthesis, Structure, and Reactions
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A mixture of an enol trimethylsilyl ether and a fluoride salt exists in a dynamic equilibrium with an enolate species and fluorotrimethylsilane.Evacuation of an equimolar mixture of an enol trimethylsilyl ether of benzyl methyl ketone and tris(diethylamino)sulfonium (TAS) difluorotrimethylsiliconate produces fluorotrimethylsilane as the volatile fraction and the corresponding TAS enolate as air-sensitive crystals.The conductivity measurement and the 1H and 13C NMR analysis have substantiated the ionic nature of the TAS enolate in THF.The NMR chemical shifts are interpreted in terms of the electron distribution.The isolated TAS enolate undergoes O-acetylation with acetic anhydride and C-alkylation with methyl iodide exclusively.TAS enolate intermediates generated in situ from a series of enol silyl ethers and TAS difluorotrimethylsiliconate react with various active organic halides under mild conditions to give the regiospecific C-alkylation products.The in situ formed enolates react with aldehyde substrates to afford the β-trimethylsiloxy ketone adducts.In most cases, the reaction is kinetically controlled and the major products have erythro stereochemistry regardless of enolate configuration.This aldol reaction is postulated to proceed via an acyclic, extended transition state, in contrast to ordinary aldol reactions of Lewis acid coordinated enolates, which take place by way of six-membered chelate transition states.
- Noyori, R.,Nishida, I.,Sakata, J.
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p. 1598 - 1608
(2007/10/02)
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- Magnesium-Induced Cyclizations of 2-(3-Iodopropyl)cycloalkanones. A Cyclopentane Annelation Method
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A process for the stereoselective construction of a cyclopentane ring onto a preexisting cycloalkanone is developed. 2-(3-Iodopropyl)cycloalkanones, obtained by known methods from the parent cyclic ketones, were converted to bicycloalkan-1-ols in moderate to good yields by magnesium in THF.This cyclization shows a large preference for formation of the cis compounds.Attempts to extend this reaction to the formation of six- and seven-membered rings were largely unsuccessful.
- Crandall, Jack K.,Magaha, H. Steve
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p. 5368 - 5371
(2007/10/02)
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- Fluoride-Mediated Reactions of Enol Silyl Ethers. Regiospecific Monoalkylation of Ketones
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Treatment of enol silyl ethers with alkyl halides in the presence of benzyltrimethylammonium fluoride and molecular sieves at room temperature gives the corresponding monoalkylated products with high regiospecificity.In most cases no polyalkylated products formed in the reaction.The alkylation reaction is highly chemospecific: esters, epoxides, and even ketones survive the reaction conditions.The reactions of various cyclohexanone derivatives proceed with the preferential axial attack of the electrophile.
- Kuwajima, Isao,Nakamura, Eiichi,Shimizu, Makoto
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p. 1025 - 1030
(2007/10/02)
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- HIGHLY DISPERSED POTASSIUM ON ALUMINA AS A METALATING AGENT. ALKYLATION OF ENOLIZABLE COMPOUNDS
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Highly dispersed potassium on alumina (K/Al2O3) acts as a metalating agent towards enolizable compounds and the intermediate organopotassium derivatives can be alkylated with primary alkyl bromides.The reaction conditions are dependent on the substrate.In particular, tetrahydrofuran is the solvent of choice for the metalation of nitriles and aldehyde N,N-dimethylhydrazones at -60 deg C and of N-cyclohexyl ketimines at room temperature, whereas hexane must be used for ketones.
- Savoia, Diego,Tagliavini, Emilio,Trombini, Claudio,Umani-Ronchi, Achille
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p. 281 - 286
(2007/10/02)
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