- Palladium/Copper-catalyzed Oxidation of Aliphatic Terminal Alkenes to Aldehydes Assisted by p-Benzoquinone
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The development of an anti-Markovnikov Wacker-type oxidation for simple aliphatic alkenes is a significant challenge. Herein, a variety of aldehydes can be selectively obtained from various unbiased aliphatic terminal alkenes using PdCl2(MeCN)2/CuCl in the presence of p-benzoquinone (BQ) under mild reaction conditions. Isomerization of the terminal alkene to the internal alkene was suppressed via slow addition of the starting material to the reaction mixture. In addition to the Pd catalyst, CuCl and BQ were essential in order to obtain the anti-Markovnikov product with high selectivity. Terminal alkenes bearing a halogen substituent afforded their corresponding aldehydes with high anti-Markovnikov selectivity. The halogen acts as a directing group in the reaction. DFT calculations indicate that a μ-chloro Pd(II)?Cu(I) bimetallic species with BQ coordinated to Cu is the catalytically active species in the case of a terminal alkene without a directing group.
- Komori, Saki,Yamaguchi, Yoshiko,Murakami, Yuka,Kataoka, Yasutaka,Ura, Yasuyuki
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p. 3946 - 3955
(2020/07/06)
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- Palladium-Catalyzed Aerobic Anti-Markovnikov Oxidation of Aliphatic Alkenes to Terminal Acetals
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Terminal acetals were selectively synthesized from various unbiased aliphatic terminal alkenes and 1,2-, 1,3-, or 1,4-diols using a PdCl2(MeCN)2/CuCl catalyst system in the presence of p-toluquinone under 1 atm of O2 and mild reaction conditions. The slow addition of terminal alkenes suppressed the isomerization to internal alkenes successfully. Electron-deficient cyclic alkenes, such as p-toluquinone, were key additives to enhance the catalytic activity and the anti-Markovnikov selectivity. The halogen groups in the alkenes were found to operate as directing groups, suppressing isomerization and increasing the selectivity efficiently.
- Komori, Saki,Yamaguchi, Yoshiko,Kataoka, Yasutaka,Ura, Yasuyuki
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p. 3093 - 3099
(2019/03/29)
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- PROCESS FOR PREPARING KETONES BY REACTING 1,1-DISUBSTITUTED OLEFINS WITH N2O
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The present invention relates to a process for preparing a ketone, comprising the reaction of a composition (I) at least comprising a 1,1-disubstituted olefin, with a composition comprising dinitrogen monoxide, wherein the reaction is effected in the presence of a solvent which comprises at least one proton-donating functional group.
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Page/Page column 5-6
(2011/11/12)
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- Complete ozonolysis of alkyl substituted ethenes at -60°C: Distributions of ozonide and oligomeric products
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The distribution of ozonidc and oligomeric structures formed on complete ozonolysis of alkenes in a non-participating solvent at -60°C is governed by the alkyl substitution around the carbon-carbon double bond. The ozonolysis of a 1,1-alkyl substituted ethene generally favours the formation of an ozonide (a 1,2,4-trioxolane). Whereas the ozonolysis of a 1,1,2-alkyl substituted ethene also produces ozonide, a considerable amount of the ozonised products are oligomeric in nature. For example, the ozonolysis of 3-methylpent-2-ene in solution to high conversion in pentane yields oligomers with structural units derived from the fragmentation products of the primary ozonide (a 1,2,3-trioxolane) which are namely butanone carbonyl oxide and acetaldehyde; these can be characterised by electrospray ionisation mass spectroscopy (ESI-MS) under soft ionisation conditions. The predominant oligomers formed are rich in carbonyl oxide units (80 + mol%) and are cyclic in nature. A small proportion of the oligomers formed are open chain compounds with end groups that suggest that chain termination is brought about either by water or by hydrogen peroxide. Residual water in the solvent will react with the carbonyl oxides to produce 2-methoxybut-2-yl hydroperoxide, which we propose readily decomposes generating hydrogen peroxide. A significant yield of oligomers also is obtained from the ozonolysis of a 1,2-alkyl substituted ethene. The ozonolysis of trans-hex-2-ene in pentane yields oligomers containing up to four structural units and are predicted to be mainly cyclic. The Royal Society of Chemistry 2005.
- Barton, Matthew,Ebdon, John R.,Foster, Andrew B.,Rimmer, Steve
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p. 1323 - 1329
(2007/10/03)
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- Process for producing carbonyl or hydroxy compound
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There are disclosed are a method for producing at least one compound selected from a carbonyl compound and a hydroxy adduct compound by an oxidative cleavage or addition reaction of an olefinic double bond of an olefin compound,???which contains??????reacting an olefin compound with hydrogen peroxide, utilizing as a catalyst, at least one member selected from(a) tungsten,(b) molybdenum, or(c) a tungsten or molybdenum metal compound containing(ia) tungsten or (ib) molybdenum and(ii) an element of Group IIIb, IVb, Vb or VIb excluding oxygen, anda catalyst composition.
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- Thermolysis of 3-alkyl-3-methyl-1,2-dioxetanes: Activation parameters and chemiexcitation yields
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3-Methyl-3-(3-pentyl)-1,2-dioxetane 1 and 3-methyl-3-(2,2-dimethyl-1-propyl)-1,2-dioxetane 2 were synthesized in low yield by the α-bromohydroperoxide method. The activation parameters were determined by the chemiluminescence method (for 1 ΔH? = 25.0 ± 0.3 kcal/mol, ΔS? = -1.0 entropy unit (e.u.), ΔG? = 25.3 kcal/mol, k1 (60°C) = 4.6 × 10-4s-1; for 2 ΔH? = 24.2 ± 0.2 kcal/mol, ΔS? = -2.0 e.u., ΔG? = 24.9 kcal/mol, k1 (60°C) = 9.2 × 10-4s-1. Thermolysis of 1-2 produced excited carbonyl fragments (direct production of high yields of triplets relative to excited singlets) (chemiexcitation yields for 1: φT = 0.02, φS ≤ 0.0005; for 2: φT = 0.02, φS ≤ 0.0004). The results are discussed in relation to a diradical-like mechanism.
- Baumstark, Alfons L.,Anderson, Sean L.,Sapp, Chariety J.,Vasquez, Pedro C.
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p. 176 - 179
(2007/10/03)
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- Thermolysis of 3-alkyl-3-methyl-1,2-dioxetanes: Activation parameters and chemiexcitation yields
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3-Methyl-3-(3-pentyl)-1,2-dioxetane 1 and 3-methyl-3-(2,2-dimethyl-1-propyl)-1,2-dioxetane 2 were synthesized in low yield by the α-bromohydroperoxide method. The activation parameters were determined by the chemiluminescence method (for 1 ΔH? = 25.0 ± 0.3 kcal/mol, ΔS? = -1.0 entropy unit (e.u.), ΔG? = 25.3 kcal/mol, k1 (60°C) = 4.6 × 10-4s-1. Thermolysis of 1-2 produced excited carbonyl fragments (direct production of high yields of triplets relative to excited singlets) (chemiexcitation yields) for 1: φT = 0.2, φ ≤ 0.0005; for 2: φT = 0.02 φS ≤ 0.0004). The results are discussed in relation to a radical-like mechanism.
- Baumstark, Alfons L.,Anderson, Sean L.,Sapp, Chariety J.,Vasquez, Pedro C.
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p. 459 - 462
(2007/10/03)
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- Radical addition to carbenoids. Chain reactions of α-diazo carbonyl compounds with triorganotin hydrides, tris(trimethylsilyl)silane and allyltributylstannane
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α-Diazo ketones RC(O)CH=N2 react with tributyltin hydride at 60°C in benzene to give the corresponding α-stannyl ketones RC(O)CH2SnBu3, which exist in equilibrium with the stannyl enol ether tautomers R(Bu3SnO)C=CH2. The reactions are initiated by di-tert-butyl hyponitrite and follow a free-radical chain mechanism. Triphenyltin hydride and tris(trimethylsilyl)silane [(TMS)3SiH] react similarly, the latter to yield the α-silyl ketone RC(O)CH2Si(TMS)3 which does not isomerise to the more stable silyl enol ether R[(TMS)3SiO]C=CH2 under the reaction conditions. This result indicates that TMS3Si. reacts at the α-carbon atom of the α-diazo ketone to give R(CO)CHSiTMS3, probably via an initial diazenyl radical adduct; triorganotin radicals are assumed to react in the same way. When the group R in the α-diazo ketone is but-3-enyl, the intermediate α-metalloalkyl radical undergoes 5-exo-cyclisation. Allyltributylstannane reacts with α-diazo ketones and with ethyl α-diazoacetate in refluxing benzene, in the presence of 2,2′-azo(2-methylpropionitrile) as initiator, to give butenyl ketones RC(O)CH2CH2CH=CH2 and ethyl pent-4-enoate, respectively, after a hydrolytic work-up.
- Dang, Hai-Shan,Roberts, Brian P.
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p. 769 - 775
(2007/10/03)
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- Thexylhaloborane-Methyl Sulfide as Monohydroboration Reagent. Directive Effects in the Hydroboration of Alkynes
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Thexylhaloborane-Methyl Sulfide ThxBHX-SMe2 (X = Cl, Br, I) undergoes direct hydroboration of both terminal and internal alkynes at 25 deg C to provide the corresponding alkenyl-thexylhaloboranes in the exceptional isomeric purity.
- Cha, Jin Soon,Min, Soo Jin,Kim, Jong Mi,Kwon, Oh Own
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p. 5113 - 5116
(2007/10/02)
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- Structure and reactions of oxametallacyclobutanes and oxametallacyclobutenes of ruthenium
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Structure and reactivity studies are reported with the ruthenium metallacycles prepared as described in the previous paper. A C-C cleavage reaction by an apparent β-Me elimination pathway at 45°C is reported for the PMe3-substituted oxametallacyclobutane complex (PMe3)4Ru(OC(Me)(Ph)CH2) (1), while the analogous DMPE-substituted metallacyclobutane (DMPE)2Ru(OC(Me)(Ph)CH2) (2) is stable at 140°C. Similarly, compound 1 undergoes insertion of CO into the metal-carbon bond, while 2 is inert toward this substrate. Addition of protic acids and electrophiles leads to rapid extrusion of α-methylstyrene with both metallacycles. X-ray structural analysis of the acetone dianion complex (PMe3)4Ru((CH2)2CO) (17) was performed and displays a dihedral angle of 46°C in the metallacycle. In contrast, the 4,4-dimethyl-2-butanone dianion complex (PMe3)4Ru(CH2C(CHCMe3)O) (15) contains a flat metallacycle that is bound through the CH2 group and the oxygen atom. Reactivity studies with 15 showed that, unlike compounds 1 and 2, the organic portion remained intact upon addition of protic acids. The addition of 4,4-dimethyl-2-butanone led to a second C-C cleavage reaction, forming the di-tert-butylacetylacetonate complex (PMe3)3Ru-(Me)(CH(COCH2CMe3) 2) (19). Reactivity studies with 17 showed reversible formation of the isolable oxatrimethylenemethane complex 18, which was isolated and structurally characterized. Addition of acetone to 17 led to formation of mesityl oxide dianion complex (PMe3)4Ru(OC(Me)CHC(Me)CH) (19); mesityl oxide is presumably formed by aldol condensation at the metal center. Reactivity studies of the oxametallacyclobutene complex (PMe3)4Ru(OC(CMe3)CH) showed formation of free ketone upon addition of protic acids and insertion into the metal-oxygen bond upon addition of CO2. The metallacycle was converted to the silyl enol ether upon addition of trimethylsilane and to the free ketone following addition of H2.
- Hartwig, John F.,Bergman, Robert G.,Andersen, Richard A.
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p. 3344 - 3362
(2008/10/08)
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- ORGANOCOPPER REAGENTS IN DIMETHYL SULFIDE
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Organocopper(I) reagents, RCu, are both more stable and more reactive when prepared in dimethyl sulfide instead of ether or tetrahydrofuran.A wide range of Li reagents has been investigated with good results, as has a selection of Grignard reagents.Excellent yields of products are observed with typical substrates as α,β-unsaturated ketones and acid chlorides.
- Bertz, Steven H.,Dabbagh, Gary
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p. 425 - 434
(2007/10/02)
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- 1-BROMO-1-(TRIMETHYLSILYL)-1-ALKENES. A SINGLE SYNTHON FOR BOTH THE CARBONYL ANION AND CATION
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The utility of 1-bromo-1-(trimethylsilyl)-1-alkenes as a single synthon for both the carbonyl anion and cation is demonstrated.
- Miller, R. B.,Al-Hassan, M. I.,McGarvey, G.
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p. 969 - 976
(2007/10/02)
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- Studies on the Autoxidation of Branched-chain Olefins. I. Autoxidation of 2-Methylalk-1-enes and 2-Methylalk-2-enes
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The products of the autoxidation of 2-methylpent-1-ene, 2-methylpent-2-ene, 2-methylhex-1-ene, 2-methylhex-2-ene, 2,4,4-trimethylpent-1-ene, and 2,4,4-trimethylpent-2-ene were analyzed by gas chromatography.The identification of the products corresponding to the individual peaks was possible by comparison with authentic substances or by preparative gaschromatographic separation and n.m.r.-spectroscopy of the isolated samples.In this way not only the epoxides and the products of the oxidative cleavage of the C=C double bond but also the allylic alcohols formed by LiAlH4-reduction of the oxidation mixtures could be identified and analyzed.From the results the compositions of the original oxidation mixtures were calculated.
- Bilas, W.,Hoebold, W.,Pritzkow, W.
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p. 125 - 141
(2007/10/02)
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- Thermochemical Studies of Carbonyl Reactions. 2. Steric Effects in Acetal and Ketal Hydrolysis
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A calorimetric determination of the enthalpies of hydrolysis of a series of alkyl-substituted dimethyl acetals is reported.These data are critically compared with the enthalpies of hydrolysis from an analogous set of aliphatic dimethyl ketals derived from 2-alkanones.The acetals exhibit a significantly attenuated range in their enthalpies of hydrolysis relative to that for ketal hydrolysis.The free energies of acetal formation in solution were modeled by measurements of the corresponding free energies of hemiacetal formation from the aldehydes in neutral methanol.The observed free-energy differences are satisfactorily correlated with the Taft Es steric substituent constant scale, but the corresponding acetal enthalpy data vary in a complex manner.The role of entropy in determining kinetic and equilibrium steric effects in a variety of other systems is discussed.Preliminary molecular mechanics calculations on these systems indicate the importance of bond angle bending in evaluating the torsional potential at a carbonyl group.Many of the compounds were found to possess several conformations having comparable energies.
- Wiberg, Kenneth B.,Squires, Robert R.
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p. 4473 - 4478
(2007/10/02)
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- Lewis Acid Mediated α-Alkylation of Carbonyl Compounds, VI. Optimization of the Procedure for the α-tert-Alkylation of Ketones and Aldehydes
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A simple procedure is described according to which ketones and aldehydes can be tert-alkylated at the α-position in two steps.Silyl enol ethers, which are easily accessible from the corresponding carbonyl compounds, are reacted with tert-alkyl halides in the presence of Lewis acids.Using cyclohexanone and n-butyraldehyde, the method was optimized.Tin or titanium tetrachloride in combination with tert-butyl chloride in methylene chloride at low temperatures is usually optimal.The method can be applied generally to structurally different ketones.
- Reetz, Manfred T.,Maier, Wilhelm F.,Heimbach, Horst,Giannis, Athanassios,Anastassious, Georgia
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p. 3734 - 3740
(2007/10/02)
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