- Searching for the Ionized Alkene/Alkanol Complexes +./HOCH3> and +./HOCH2CH3>
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Experiments on a variety of isomeric +. and +. ions have failed to produce direct evidence for the involvement of the complex ions +./HOCH3> and +./HOC2H5>.For the isomers studied, the rearrangements prior to their dissociation of lowest energy requirement (loss of H2O and C2H5., respectively) are proposed to involve distonic and ylid ions.
- Cao, J. R.,George, M.,Holmes, John L.
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Read Online
- Synthesis and Catalytic Activity of Niobium-Containing Hexagonal Mesoporous Silica
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Niobium-containing hexagonal mesoporous silica has been synthesized using n-dodecylamine as a template; the novel material is very active as a catalyst in the epoxidation of propylene with hydrogen peroxide and alkyl peroxides as oxidants.
- Liu, Yanyong,Murata, Kazuhisa,Inaba, Megumu
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Read Online
- Hydrogenation of Esters by Manganese Catalysts
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The hydrogenation of esters catalyzed by a manganese complex of phosphine-aminopyridine ligand was developed. Using this protocol, a variety of (hetero)aromatic and aliphatic carboxylates including biomass-derived esters and lactones were hydrogenated to primary alcohols with 63–98% yields. The manganese catalyst was found to be active for the hydrogenation of methyl benzoate, providing benzyl alcohol with turnover numbers (TON) as high as 45,000. Investigation of catalyst intermediates indicated that the amido manganese complex was the active catalyst species for the reaction. (Figure presented.).
- Li, Fu,Li, Xiao-Gen,Xiao, Li-Jun,Xie, Jian-Hua,Xu, Yue,Zhou, Qi-Lin
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- A HPPO by-product recycling synthetic 1, 3 - propanediol (by machine translation)
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The invention belongs to the technical field of organic chemical industry, relates to a HPPO by-product recycling synthetic 1, 3 - propanediol, more specifically, relates to a propylene HPPO process with methanol the reaction product of propylene glycol monomethyl ether as the raw material, and sequentially passes through the dewatering, borohydrite oxidation, hydrolysis of the three-step reaction synthesizes the high value added 1, 3 - propylene glycol, 1, 3 - propylene glycol total yield of 80% or more, purity 99.5% or more, the invention has the simple process route, rationalization of resources use, 1, 3 - propylene glycol yield and purity and the like. (by machine translation)
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Paragraph 0036-0041
(2019/07/04)
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- Method for preparing 1,3-propylene glycol by means of methyl 3-methoxypropionate
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The invention provides a method for preparing 1,3-propylene glycol by means of methyl 3-methoxypropionate, and relates to the field of chemical synthesis. Aiming at the problems that for an existing method, the technology condition is high, a reaction is harsh, and operation is complex, methyl 3-methoxypropionate serves as the main raw material, methyl 3-methoxypropionate is obtained through a hydrogenation reaction, demethylation is conducted, and reaction is conducted with hydroiodic acid, a target product 1,3-propylene glycol and methyl iodide are obtained, methyl iodide is subjected to catalytic cracking finally, and hydroiodic acid is obtained, wherein hydroiodic acid is reused in the demethylation process. For the whole scheme, the synthetic route is short, reaction selectivity is good, the cost is low, the yield is high, the quality is high, raw material resources are simple, the method does not refer to high temperature and high pressure, the technology is safe and reliable, operability is high, and the influence on the environment is low.
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Page/Page column 4-6
(2018/10/11)
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- CONTROLLED RELEASE PREPARATION
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A controlled release preparation wherein the release of active ingredient is controlled, which releases an active ingredient for an extended period of time by staying or slowly migrating in the gastrointestinal tract, is provided by means such as capsulating a tablet, granule or fine granule wherein the release of active ingredient is controlled and a gel-forming polymer. Said tablet, granule or fine granule has a release-controlled coating-layer formed on a core particle containing an active ingredient.
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Paragraph 0529; 0530
(2016/06/06)
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- Replacing phosphorus with sulfur for the efficient hydrogenation of esters
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Catalyst tune-up: A readily available, air-stable amino-sulfide catalyst, [RuCl2(PPh3){HN(C2H4SEt) 2}], has been developed. This complex displays outstanding efficiency for the hydrogenation of a broad range of substrates with C-X bonds (esters, ketones, imines), as well as for the acceptorless dehydrogenative coupling of ethanol to ethyl acetate (see scheme). Copyright
- Spasyuk, Denis,Smith, Samantha,Gusev, Dmitry G.
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supporting information
p. 2538 - 2542
(2013/04/10)
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- Catalytic hydrogenation of esters. Development of an efficient catalyst and processes for synthesising (R)-1,2-propanediol and 2-(l-Menthoxy)ethanol
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A ruthenium catalyst for the reduction of esters by hydrogenation has been developed. Processes for the hydrogenation of esters have also been developed for (R)-1,2-propanediol and 2-(l-menthoxy)ethanol. The catalyst shows good catalytic activity for the hydrogenation of esters in methanol. Methyl lactate was reduced at 30 °C and gave turnover numbers (TON) up to 4000. The optical purity of the (R)-1,2-propanediol made by the hydrogenation of methyl (R)-lactate was higher than that via the asymmetric hydrogenation of hydroxyacetone. A hydrogenation process to replace the lithium aluminum hydride (LAH) reduction used in the production of 2-(l-menthoxy)ethanol was developed.
- Kuriyama, Wataru,Matsumoto, Takaji,Ogata, Osamu,Ino, Yasunori,Aoki, Kunimori,Tanaka, Shigeru,Ishida, Kenya,Kobayashi, Tohru,Sayo, Noboru,Saito, Takao
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experimental part
p. 166 - 171
(2012/05/20)
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- PROCESS FOR THE PREPARATION OF (2S,4S,5S,7S)-N-(2-CARBAMYL-2- METHYLPROPYL)-5-AMINO-4-HYDROXY-2,7-DIISOPROPYL-8-[4-METHOXY-3-(3- METHOXYPROPOXY)PHENYL]-OCTANAMIDE HEMIFUMARATE AND ITS INTERMEDIATES THEREOF
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The present invention relates to a process for the preparation of (2S,4S,5S,7S)-N-(2- Carbamoyl-2-methylpropyl)-5-amino-4-hydroxy-2,7-diisopropyl-8-[4-methoxy-3-(3-methoxy propoxy )phenyl]-octanamide compound of formula- 1 and its pharmaceutically acceptable salts thereof. Further, relates to the processes for the preparation of (R)-4-(2-(halomethyl)-3- methylbutyl)-l-methoxy-2-(3-methoxypropoxy) benzene and (R)-2-(4-methoxy-3-(3-methoxy propoxy) benzyl)-3-methyIbutan-l-ol useful intermediates in the synthesis of compound of formula- 1.
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Page/Page column 57-58
(2011/12/14)
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- INTERMEDIATE COMPOUND OF TECHNETIUM NITRIDE COMPLEX FOR RADIODIAGNOSTIC IMAGING
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A bisphosphonoaminc compound represented by the following formula (I): wherein R1, R2, R3, R4 and R5 are independently an alkyl group having 1 to 6 carbon atoms, and n is an integer of 1 to 6, is extremely useful as an intermediate for preparing a technetium nitride complex for radiodiagnostic imaging.
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Page/Page column 6
(2010/07/04)
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- PROCESS FOR PREPARING 3-ALKOXYPROPAN-1-OLS
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The present invention relates to a process for preparing 3-alkoxypropan-1-ols of the general formula I by catalytic hydrogenation of esters of the general formula II, where the radicals R1 and R2 and R3, R4 and R5 are each, independently of one another, a straight-chain or branched C1-C20-alkyl radical which may optionally be substituted by one or more C1-C20-alkoxy radicals or interrupted by one or more oxygen atoms in the chain, C6-C20-aryl, C7-C20-arylalkyl which may optionally be substituted by one or more C1-C20-alkoxy radicals or interrupted by one or more oxygen atoms in the alkyl chain, C7-C20-alkylaryl which may optionally be substituted by one or more C1-C20-alkoxy radicals or interrupted by one or more oxygen atoms in the alkyl chain, a C1-C20-cycloalkyl radical which may optionally be substituted by one or more C1-C20-alkoxy radicals and R2, R3 and R4 can, independently of one another, also be hydrogen, over chromium- and nickel-free catalysts.
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Page/Page column 4-5
(2010/04/23)
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- NPY ANTAGONISTS, PREPARATION AND USES
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The present invention concerns novel compounds, their preparation and their uses, therapeutic uses in particular. More specifically it concerns derivative compounds having at least two aromatic cycles, their preparation and their uses, in particular in the area of human or animal health. These compounds have an affinity for the biological receptors of neuropeptide Y, NPY, present in the central and peripheral nervous systems. The compounds of the invention are preferably NPY antagonists, and more particularly antagonists of sub-type NPY Y1, and can therefore be used for the therapeutic or prophylactic treatment of any disorder involving NPY. The present invention also concerns pharmaceutical compositions containing said compounds, their preparation and their uses, as well as treatment methods using said compounds.
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Page/Page column 98
(2009/09/28)
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- Method for producing alcohols
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A method for producing alcohols which comprises reducing esters or lactones with hydrogen gas in the presence of a catalyst comprising (i) a ruthenium compound, (ii) a monodentate monophosphine or a bidentate bisphosphine, and (iii) an amine. Examples of the catalyst include a ruthenium (Ru) complex represented by the formula:RuX1X2(LP)m(LN)n [X1 and X2 each represent an anionic ligand, LP represents a phosphine ligand, m is 1 when LP is bidentate, while m is 2 when LP is monodentate, LN represents an amine ligand, and n is 1 when LN is bidentate, while n is 2 when LN is monodentate.] and a catalyst comprising an amine and a ruthenium (Ru) complex of the formula: RuX1X2 (LP1)r [LP1 represents a monophosphine ligand and r is 3 or 4.].
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Page/Page column 18
(2008/12/08)
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- Hydrogen bonding lowers intrinsic nucleophilicity of solvated nucleophiles
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The relationship between nucleophilicity and the structure/environment of the nucleophile is of fundamental importance in organic chemistry. In this work, we have measured nucleophilicities of a series of substituted alkoxides in the gas phase. The functional group substitutions affect the nucleophiles through ion-dipole, ion-induced dipole interactions and through hydrogen bonding whenever structurally possible. This set of alkoxides serves as an ideal model system for studying nucleophiles under microsolvation settings. Marcus theory was applied to analyze the results. Using Marcus theory, we separate nucleophilicity into two independent components, an intrinsic nucleophilicity and a thermodynamic driving force determined solely by the overall reaction exothermicity. It is found that the apparent nucleophilicities of the substituted alkoxides are always much lower than those of the unsubstituted ones. However, ion-dipole, ion-induced dipole interactions, by themselves, do not significantly affect the intrinsic nucleophilicity; the decrease in the apparent nucleophilicity results from a weaker thermodynamic driving force. On the other hand, hydrogen bonding not only stabilizes the nucleophile but also increases the intrinsic barrier height by 3 to ~4 kcal mol-1. In this regard, the hydrogen bond is not acting as a perturbation in the sense of an external dipole but more directly affects the electronic structure and reactivity of the nucleophilic alkoxide. This finding offers a deeper insight into the solvation effect on nucleophilicity, such as the remarkably lower reactivities in nucleophilic substitution reactions in protic solvents than in aprotic solvents.
- Chen, Xin,Brauman, John I.
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scheme or table
p. 15038 - 15046
(2009/03/12)
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- INTERMEDIATE COMPOUND OF TECHNETIUM NITRIDE COMPLEX FOR RADIODIAGNOSTIC IMAGING
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A bisphosphonoamine compound represented by the following formula (I): wherein R1, R2, R3, R4 and R5 are independently an alkyl group having 1 to 6 carbon atoms, and n is an integer of 1 to 6, is extremely useful as an intermediate for preparing a technetium nitride complex for radiodiagnostic imaging.
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Page/Page column 24-25
(2010/11/28)
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- DRUG COMPOSITION HAVING ACTIVE INGREDIENT ADHERED AT HIGH CONCENTRATION TO SPHERICAL CORE
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Granule, fine particle or tablet of excellent leaching property, comprising a drug active ingredient in high content realized by forming a layer containing drug active ingredient on core particles through a combination of a method of dispersing and adhering an active ingredient while spraying or adding a binder with a method of spraying or adding a solution or suspension wherein an active ingredient and a binder are contained so as to effect adhesion. Further, there are provided a drug composition containing such a granule, fine particle or tablet and a process for producing the same.
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Page/Page column 57
(2010/02/14)
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- CONTROLLED RELEASE COMPOSITION
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The present invention provides a controlled release composition showing release of an active ingredient (proton pump inhibitor) controlled in two or more steps at different release rates, which contains1) a release-controlled part A capable of controlling release of the active ingredient to occur at a predetermined rate,2) a release-controlled part B capable of controlling release of the active ingredient to occur at a predetermined rate lower than the release rate of the release-controlled part A, and where necessary, 3) a release-controlled part C capable of controlling release of the active ingredient to occur at a predetermined rate faster than the release rate of the release-controlled part B, wherein the release of the active ingredient from the release-controlled part B precedes the release of the active ingredient from the release-controlled part A (when release-controlled part C is contained, the release of the active ingredient from the release-controlled part C precedes the release of the active ingredient from the release-controlled part B).
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Page/Page column 57
(2010/02/15)
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- PRODUCTION PROCESS OF 3-ALKOXY-1-PROPANOLS, AND 3-ALKOXY-1-PROPANOLS OBTAINED BY THE PRODUCTION PROCESS
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In the presence of a catalyst containing at least one element selected from the group consisting of elements of the group III, lanthanoid elements and actinoid elements of the Periodic Table, an allyl alcohol is reacted with an alcohol compound. A method for efficiently producing 3-alkoxy-1-propanol in a single step using an alcohol as a starting material is provided.
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Page/Page column 35-36; 54
(2008/06/13)
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- Synthesis of the marine compound (2R,5Z,9Z)-2-methoxyhexacosa-5,9-dienoic acid via a lipase-catalyzed resolution and a novel O-alkylation protocol
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The title compound has been synthesized by a facile route starting from 4-pentyn-1-ol. The enantioselectivity was attained by a strategy involving a lipase-catalyzed acetylation of a solid-phase immobilized long chain α-hydroxy acid. Another important feature of the synthesis was the formulation of an efficient HgO-catalyzed O-methylation of the α-hydroxy acids which proceeded without any racemization. The alkylation protocol was also highly efficient for selective mono-methylation/benzylation of symmetrical diols.
- Kulkarni, Bheemashankar A.,Sharma, Anubha,Gamre, Sunita,Chattopadhyay, Subrata
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p. 595 - 599
(2007/10/03)
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- Precursors of 3-alkoxyalkanols and processes for the preparation of 3-alkoxyalkanols
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Processes for the preparation of 3-alkoxyalkanols useful as solvents for coating materials, photoresists, or the like. Specifically, (1) a process which comprises reacting an α,β-unsaturated aldehyde with an alcohol in the presence of an acidic catalyst and subjecting the obtained product to hydrolysis and hydrogenation successively; (2) a process which comprises subjecting a reaction mixture obtained by the reaction of an α,β-unsaturated aldehyde with an alcohol and comprising the corresponding 1,1,3-trialkoxyalkane and 3-alkoxyalkanal to hydrolysis and hydrogenation at the same time; (3) a process which comprises recovering a 3-alkoxyalkanal through distillation as an azeotropic mixture thereof with water from a reaction solution obtained by the reaction of an alcohol with acid-containing acrolein or methacrolein prepared by the oxidation of propylene or isobutylene, and hydrogenating the recovered 3-alkoxyalkanal into the corresponding 3-alkoxyalkanol; and (4) a process which comprises bringing a gas produced by the oxidation of propylene or isobutylene into contact with an alcohol, conducting the reaction of the gas with the alcohol to form the corresponding 1,1,3-trialkoxyalkane, and subjecting it to hydrolysis and hydrogenation.
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- PRODRUGS OF IMIDAZOLE DERIVATIVES, FOR USE AS PROTON PUMP INHIBITORS IN THE TREATMENT OF E.G. PEPTIC ULCERS
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An imidazole compound represented by the formula (I), a salt thereof and a compound of the formula (V), which is one of the intermediates thereof. wherein each symbol is as defined in the present specification. The compound of the present invention shows a superior anti-ulcer activity, a gastric acid secretion inhibitory action, a mucosa-protecting action, an anti-Helicobacter pylori action and the like. Since it shows low toxicity, the compound is useful as a pharmaceutical product.
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- PRECURSORS OF 3-ALKOXYALKANOLS AND PROCESSES FOR THE PREPARATION OF 3-ALKOXYALKANOLS
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Processes for the preparation of 3-alkoxyalkanols useful as solvents for coating materials, photoresists, or the like.Specifcally,(1) a process which comprises reacting an α,β-unsaturated aldehyde with an alcohol in the presence of an acidic catalyst and subjecting the obtained product to hydrolysis and hydrogenation successively;(2) a process which comprises subjecting a reaction mixture obtained by the reaction of an α,β-unsaturated aldehyde with an alcohol and comprising the corresponding 1,1,3-trialkoxyalkane and 3-alkoxyalkanal to hydrolysis and hydrogenation at the same time;(3) a process which comprises recovering a 3-alkoxyalkanal through distillation as an azeotropic mixture thereof with water from a reaction solution obtained by the reaction of an alcohol with acid-containing acrolein or methacrolein prepared by the oxidation of propylene or isobutylene, and hydrogenating the recovered 3-alkoxyalkanal into the corresponding 3-alkoxyalkanol; and(4) a process which comprises bringing a gas produced by the oxidation of propylene or isobutylene Into contact with an alcohol, conducting the reaction of the gas with the alcohol to form the corresponding 1,1,3-trialkoxyalkane, and subjecting it to hydrolysis and hydrogenation.
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Page column 17
(2008/06/13)
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- Method and compounds for diagnosing coronary artery disease
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The present invention relates generally to methods of diagnosis, evaluation and treatment of coronary artery disease in mammals using substituted catecholamines and compounds therefore. It also relates to the preparation, use and administration of these compounds which are useful in the diagnosis, evaluation and treatment of coronary artery disease by means of a feedback controlled drug delivery system that delivers exercise simulating agents which are capable of eliciting acute responses similar to those elicited by aerobic exercise.
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- Kit for preparing a technetium-99m myocardial imaging agent
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A myocardial imaging agent for use in humans comprising a Tc(III) complex ligated in a planar position by a tetradentate ligand having incorporated therein four hard atotms and two furanone rings and in the axial positions by phosphines containing dioxanyl or ether moieties. The agent exhibits improved biodistribution, improved labeling and extremely rapid blood clearance following administration to a human. The agent has high myocardial uptake accompanied with exceptionally rapid hepatobilary clearance and extensive renal clearance to give sufficiently high heart/liver and heart/lung ratio that provide nearly ideal myocardial images in humans. A kit for producing the myocardial imaging agent is provided.
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- Dynamical Characterization in Aqueous Solutions of 3-Methoxy- and 3-Ethoxy-1-propanol by Ultrasonic Methods
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3-Methoxy-1-propanol and 3-ethoxy-1-propanol were synthesized through potassium propoxide from 1,3-propanediol.Ultrasonic absorptions in their aqueous solutions were measured in the frequency range from 8.5 to 220 MHz as functions of their concentrations along with the sound velocity and density.In a solution of 3-ethoxy-1-propanol, a single relaxational absorption was observed; the cause was attributed to a perturbation of an equilibrium as AB A + B, where AB represents the solute-solvent complex, A the solute and B the solvent molecules.On the other hand, no relaxational absorption was observed in a 3-methoxy-1-propanol solution up to 4 mol dm-3.The thermodynamic and the kinetic parameters were evaluated for the abovementioned process from the concentration dependences of the ultrasonic parameters in a 3-ethoxy-1-propanol solution.From evidence concerning the appearance and disappearance of ultrasonic relaxational absorption and comparisons of the rate and thermodynamic constants in aqueous solutions of various alcohols, the alternation of the water structure affected by the addition of the solutes is discussed in connection with the solute structures.The methoxyl group was explicitly found to act as a water structure breaker and the ethoxyl group to do so slightly.
- Nishikawa, Sadakatsu,Ueda, Masayuki
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p. 1294 - 1298
(2007/10/02)
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- Organic solvent soluble polyvalent metal alkoxy alkoxides
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Organic solvent soluble alkoxides of magnesium, calcium, strontium, barium, scandium, yttrium and lanthanum are prepared by the reaction of these elements with alkoxy alcohols.
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- Vacuum-ultraviolet photlysis (185) nm of liquid 1,3-dioxan
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1,3-Dioxan photolytic destruction at 185 nm occurs with a quantum yield of about 0.3 in the liquid phase.Of the 22 products determined, the major ones are n-propylformate (φ = 0.10), formaldehyde (0.075), 1,3-diox-4-en (0.06), hydrogen (0.05), ethylene (0.04), and 3-methoxypropionaldehyde (0.04).A number of the minor products are of the general type B, some of which bear a hydroxyl function at the end of the side chain.N2O interacts with excited 1,3-dioxan, leading to the production of N2.Some experiments have been carried out in the vapour phase, the results of which indicate that considerable fragmentation of hot primary intermediates and products into low-molecular-weight products occurs.The nature of these products cannot be linked directly to the primary photolytic process inferred from the liquid-phase studies.Certain contrasts in the photolytic behaviour of 1,3-dioxan and 1,4-dioxan are discussed.
- Schuchmann, Heinz-Peter,Clemens, Sonntag von
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p. 1833 - 1839
(2007/10/02)
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- Gaseous 1-Methyl-1-oxoniacycloalkanes as Stable Intermediates on the C3H7O+ and C4H9O+ Potential Energy Surfaces
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The nature and the isomeric distribution of the neutral products obtained from the gas-phase attack of CH5+, C2H5+, and CH3FCH3+ ions on cyclic CnH2nO (n = 2, 3, and 4) ethers provide the first experimental evidence in favour of 1-methyl-1-oxoniacyclopropane and 1-methyl-1-oxoniacyclobutane as stable intermediates on the corresponding potential energy surface.
- Angelini, Giancarlo,Speranza, Maurizio
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p. 1217 - 1219
(2007/10/02)
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- TRANSITION METAL PHOSPHINE COMPLEXES POSSESING A PHASE TRANSFER FUNCTION. PREPARATION AND PROPERTIES OF POLYETHER-SUBSTITUED PHOSPHINES AND THEIR PALLADIUM COMPLEXES
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For the purpose of endowing transition metal phosphine complexes with a phase transfer function, tertiary phosphines modified by polyether chains were prepared, and their properties were examined.The palladium complexes of these phosphines were efficient as catalysts for the reduction of bromobenzene with sodium hydride under a liquid-solid two-phase condition.
- Okano, Tamon,Yamamoto, Manabu,Noguchi, Takeo,Konishi, Hisatoshi
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p. 977 - 980
(2007/10/02)
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- Solvomercuration-Demercuration. 8. Oxymercuration-Demercuration of Methoxy-, Hydroxy-, and Acetoxy-Substituted Alkenes
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The oxymercuration-demercuration (OM-DM) of a series of methoxy-, hydroxy-, and acetoxy-substituted alkenes was examined.The systems examined were the allyl, crotyl, 3-buten-1-yl, 4-penten-1-yl, and 5-hexen-1-yl.The methoxyalkenes undergo hydration with very high regioselectivity and almost quantitative yield in all cases.However, a small -I effect is observed in the case of the allylalkene (97.1percent Markovnikov vs. 99.5percent in 1-hexene).Moreover, in the crotyl case, a major directing effect is observed: 97.7percent 3-ol, 2.3percent 2-ol.The other three alkenes undergo the OM reaction with no effect from the methoxy group (99.5percent Markovnikov isomer).In contrast, only allyl-, crotyl-, and 3-buten-1-yl alcohols produce major amounts of hydrated products, the diols.While no hydroxyl group directing effect is observed in the allyl system, a major one is again seen in the case of the crotyl: 93.5percent l,3-diol and 6.5percent l,2-diol.The major products from the 4-penten-1-yl and 5-hexen-1-yl and alcohols are 2-methyltetrahydrofuran and 2-methyltetrahydropyran, respectively, resulting from OH-5 and OH-6 neighboring group participation in the OM stage.The acetoxy alkenes undergo hydration to give diols in ca. 80percent yield with ca. 20percent unreacted starting material.This is the result of a competitive deoxymercuration reaction which is occurring in the DM stage.However, the yield of hydrated products can be increased by varying the amount of base used in the DM.Neighboring-group participation, AcO-5, is observed in the allyl system only, resulting in a 65percent yield of the Markovnikov oxymercurial, by 1H NMR analysis, and a 35percent yield of the acetoxy-exchanged mercurial.Again, a major -I-directing effect of the acetoxy group was observed in the crotyl system but not in the others.In addition to the expected l,2- and l,3-diols, the OM-DM of crotyl acetate also resulted in small amounts of the unexpected 2,3-diol under kinetic conditions.Finally, a modified DM procedure has been developed which is compatible with the acetoxy group.
- Brown, Herbert C.,Lynch, Gary J.
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p. 531 - 538
(2007/10/02)
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- Hydroboration. 57. Hydroboration with 9-Borabicyclononane of Alkenes Containing Representative Functional Groups
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The hydroboration of alkenes containing representative functional groups was examined with 9-borabicyclononane (9-BBN) in order to extend the hydroboration reaction for the preparation of functionally substituted organoboranes.Terminal alkenes containing a remote functional group are hydroborated with a remarkable regioselectivity (>=98percent terminal), producing the corresponding stable organoboranes. 9-BBN hydroborates the allylic derivatives so as to place boron essentially on the terminal carbon atom (>=97percent).The directive effect is further enhanced (>=99percent) in the case of β-methylallyl derivatives.The hydroboration of crotyl derivatives attaches boron predominantly at the 2-position, followed by an elimination-rehydroboration sequence.However, crotyl alcohol can be protected against elimination as the tert-butyl or tetrahydropyranyl ethers.The hydroboration-oxidation of ethyl crotonate involves a series of elimination, hydroboration, and condensation processes.In the vinyl, crotyl, and isobutenyl systems, the mesomeric effect of the substituent favors the placement of boron at the β-position, while the inductive effect favors the α-position, with the former effect predominating in most cases.Acyclic β-substituted organoboranes undergo rapid elimination.Nonpolar solvents and lower reaction temperatures decrease the rate of elimination.However, those derived from cyclic vinyl derivatives are relatively stable under neutral conditions, undergoing facile elimination in the presence of a base.
- Brown, Herbert C.,Chen, Jackson C.
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p. 3978 - 3988
(2007/10/02)
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- Opening of Cyclic Acetals by Trichloro-, Dichloro- and Tribromo-borane
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The rate-determining step in the ring opening of cyclic acetals by trichloroborane to yield α-chloro-ethers is shown to be consistent with the formation of an oxocarbenium ion.Subsequent reduction provides a general route for the conversion of a diol into a hydroxy-ether.Tribromoborane is a more powerful and dichloroborane a less powerful reagent than trichloroborane.
- Bonner, Trevor G.,Lewis, David,Rutter, Keith
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p. 1807 - 1810
(2007/10/02)
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- Polar Substituent Effects in the Solvolysis of Primary and Tertiary Alkyl Halides. Polar Effect IX
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When the Hammett-Taft equation log (k/k0) = ρq ?qi is applied to the solvolysis of the 3-substituted propyl bromides 6a-6i in ethanol/water 4:1 (v/v) log k correlates linearly with ?qI except in cases where R exerts an anchimetric effect.The reaction constant ρq for 6 is -0.12 and is typical for a nucleophilic solvent assisted ks process at a primary C-atom.The tertiary halides 1 and 3, however, which reacty with little or no nucleophilic solvent assistance, i.e. by kc processes, lead to larger ρq values of -0.71 and -1.14, respectively.The reacton constant ρq is therefore a sensitive gauge for charge development in the transition state for solvolysis of satured compounds.
- Grob, Cyril A.,Waldner, Adrian
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p. 2152 - 2158
(2007/10/02)
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