- OPEN-FLASK HYDROBORATION AND THE USE THEREOF
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The present disclosure generally relates to a process for hydroboration of an alkene or alkyne using ammonia borane (AB). In particular, the present invention relates to hydroboration of an alkene or alkyne in the presence of air or moisture, and a clean process for facile preparation of an alcohol by oxidizing the organoborane so formed with hydrogen peroxide. The products, including aminodialkylboranes, ammonia trialkylborane complexes, as well as various alcohols so prepared, are within the scope of this disclosure.
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Paragraph 0046; 0049; 0059; 0060; 0061
(2018/03/25)
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- Iridium Clusters Encapsulated in Carbon Nanospheres as Nanocatalysts for Methylation of (Bio)Alcohols
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C?H methylation is an attractive chemical transformation for C?C bonds construction in organic chemistry, yet efficient methylation of readily available (bio)alcohols in water using methanol as sustainable C1 feedstock is limited. Herein, iridium nanocatalysts encapsulated in yolk–shell-structured mesoporous carbon nanospheres (Ir@YSMCNs) were synthesized for this transformation. Monodispersed Ir clusters (ca. 1.0 nm) were encapsulated in situ and spatially isolated within YSMCNs by a silica-assisted sol–gel emulsion strategy. A selection of (bio)alcohols (19 examples) was selectively methylated in aqueous phase with good-to-high yields over the developed Ir@YSMCNs. The improved catalytic efficiencies in terms of activity and selectivity together with the good stability and recyclability were contributable to the ultrasmall Ir clusters with oxidation chemical state as a consequence of the confinement effect of YSMCNs with interconnected nanostructures.
- Liu, Qiang,Xu, Guoqiang,Wang, Zhendong,Liu, Xiaoran,Wang, Xicheng,Dong, Linlin,Mu, Xindong,Liu, Huizhou
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p. 4748 - 4755
(2017/12/15)
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- A non-dissociative open-flask hydroboration with ammonia borane: Ready synthesis of ammonia-trialkylboranes and aminodialkylboranes
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Under open-flask conditions, ammonia borane hydroborates olefins in refluxing tetrahydrofuran. Unlike conventional hydroboration, the Lewis base (ammonia) is not dissociated from the boron center. Terminal alkenes selectively provide ammonia-trialkylborane complexes. On the other hand, internal alkenes afford aminodialkylboranes via a metal-free hydroboration-dehydrogenation sequence. Alkaline hydrogen peroxide oxidation of the products provides the corresponding alcohols in high yields.
- Ramachandran, P. Veeraraghavan,Drolet, Michael P.,Kulkarni, Ameya S.
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p. 11897 - 11900
(2016/10/09)
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- Enantioselective Ethylation of Various Aldehydes Catalyzed by Readily Accessible Chiral Diols
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Four chiral C2-symmetric diols were synthesized in a straightforward three-step reaction and demonstrated excellent enantioselectivities and good overall yields. Their catalytic activities were examined via the addition of diethylzinc to various aldehydes. The enantioselective addition of diethylzinc to 2-methoxybenzaldehyde gave the corresponding chiral secondary alcohol with high yields (up to 95%) and moderate to good enantiomeric excess (up to 88%). All synthesized ligands were evaluated in the addition of diethylzinc to various aldehydes in the presence of an additional metal such as Ti(IV) complexes. Chirality 28:593–598, 2016.
- G?k, Ya?ar,Kili?arslan, Seda,G?k, Halil Zeki,Karayi?it, ?lker ümit
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p. 593 - 598
(2016/08/27)
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- Facile Protocol for Catalytic Frustrated Lewis Pair Hydrogenation and Reductive Deoxygenation of Ketones and Aldehydes
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A series of ketones and aldehydes are reduced in toluene under H2 in the presence of 5 mol % B(C6F5)3 and either cyclodextrin or molecular sieves affording a facile metal-free protocol for reduction to alcohols. Similar treatment of aryl ketones resulted in metal-free deoxygenation yielding aromatic hydrocarbons.
- Mahdi, Tayseer,Stephan, Douglas W.
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supporting information
p. 8511 - 8514
(2015/11/27)
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- Enabling catalytic ketone hydrogenation by frustrated lewis pairs
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Hydrogenation of alkyl and aryl ketones using H2 is catalytically achieved in 18 examples using 5 mol % B(C6F5)3 in an ethereal solvent. In these cases the borane and ether behave as a frustrated Lewis pair to activate H2 and effect the reduction.
- Mahdi, Tayseer,Stephan, Douglas W.
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supporting information
p. 15809 - 15812
(2015/02/19)
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- Organoleptic compound
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The present invention is directed to a novel compound, but-2-enoic acid 1,2-dimethyl-butyl ester, and a method of improving, enhancing or modifying a fragrance formulation through the addition of an olfactory acceptable amount of but-2-enoic acid 1,2-dimethyl-butyl ester.
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Page/Page column 7; 8
(2014/08/06)
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- Novel Organoleptic Compound
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The present invention is directed to a novel compound, but-2-enoic acid 1-ethyl-2-methyl-propyl ester, and a method of improving, enhancing or modifying a fragrance formulation through the addition of an olfactory acceptable amount of but-2-enoic acid 1-ethyl-2-methyl-propyl ester.
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Paragraph 0025; 0026
(2014/09/03)
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- Organoleptic compound
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The present invention is directed to a novel compound, but-2-enoic acid 1-ethyl-2-methyl-propyl ester, and a method of improving, enhancing or modifying a fragrance formulation through the addition of an olfactory acceptable amount of but-2-enoic acid 1-ethyl-2-methyl-propyl ester.
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Page/Page column 5
(2014/07/21)
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- SYNTHESIS OF HIGH CALORIC FUELS AND CHEMICALS
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In one embodiment, the present application discloses methods to selectively synthesize higher alcohols and hydrocarbons useful as fuels and industrial chemicals from syngas and biomass. Ketene and ketonization chemistry along with hydrogenation reactions are used to synthesize fuels and chemicals. In another embodiment, ketene used to form fuels and chemicals may be manufactured from acetic acid which in turn can be synthesized from synthesis gas which is produced from coal, biomass, natural gas, etc.
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Paragraph 00109
(2013/05/23)
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- Hydroboration. 97. Synthesis of new exceptional chloroborane-Lewis base adducts for hydroboration. Dioxane-monochloroborane as a superior reagent for the selective hydroboration of terminal alkenes
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Several less volatile oxygen-containing Lewis bases, such as tert-butyl methyl ether, dioxane, anisole, ethyl acetate, β-chloroethyl ether, and monoglyme, were examined as prospective mono- and dichloroborane carriers. Dioxane, ethyl acetate, and β-chloroethyl ether form relatively stable boron trichloride adducts, but the boron trichloride adduct of monoglyme is not very stable and must be used immediately. On the other hand, tert-butyl methyl ether and anisole fail to form stable boron trichloride adducts and the corresponding ether-cleaved products are obtained. Among the selected oxygen-containing Lewis bases, only dioxane forms stable and reactive mono- and dichloroborane adducts. Monoglyme and β-chloroethyl ether give stable dichloroborane adducts requiring excess of diborane. Convenient methods for the preparation of mono- and dichloroborane adducts of dioxane from dioxane-BCl3 and NaBH4 in the presence of catalytic amounts of tri- or tetraglyme were developed. The dioxane-monochloroborane adduct hydroborates representative olefins cleanly and rapidly. The corresponding alcohols were obtained in quantitative yields after oxidation. Also, the hydroboration of several terminal olefins with dioxane-monochloroborane were highly regioselective and the primary alcohols were obtained almost exclusively (>99.5%), after oxidation. Accordingly, dioxane-monochloroborane should serve as a reagent of choice for such hydroborations. The dioxane-dichloroborane adduct showed remarkable selectivity toward 2-substituted terminal olefins, such as 2-methyl-1-butene and β-pinene, when compared to simple terminal and hindered olefins, giving a unique tool for selective hydroborations. Dichloroborane adducts of monoglyme and β-chloroethyl ether also showed high reactivity, even at room temperature, toward simple unhindered olefins. However, hydroboration of hindered olefins is slow and requires either higher temperatures or the addition of 1 equiv of boron trichloride to liberate free dichloroborane, as in the case of the previously known dichloroborane adducts of methyl sulfide and diethyl ether.
- Kanth,Brown
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p. 5359 - 5365
(2007/10/03)
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- Dioxane-monochloroborane: A new and highly reactive hydroborating reagent with exceptional properties
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(equation presented) Dioxane-monochloroborane was prepared by the reaction of dioxane and dioxane-BCl3 with diborane or NaBH4 in 98% purity. The adduct thus obtained is a liquid, 6.2 M in BH2Cl, stable indefinitely at either 0 or 25°C. The adduct hydroborates simple unhindered olefins to the corresponding dialkylchloroboranes within 0.5 h, while moderately hindered olefins take 1-4 h at room temperature. Hindered tetrasubstituted olefins rapidly hydroborate to the monoalkylchloroborane stage with further hydroboration slow. Regioselectivity studies of representative olefins reveal that this new reagent possesses selectivities similar to those from the monochloroborane-diethyl ether adduct. Consequently, dioxane-monochloroborane can readily substitute for the older hydroborating agents, BH3:THF and BH3:DMS.
- Kanth, Josyula V. B.,Brown, Herbert C.
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p. 315 - 317
(2008/02/11)
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- The Predominance and Quantification of Steric Effects in the Solvolysis of Secondary Aliphatic Esters
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The solvolysis rates of 35 tosylates in hexafluoroisopropyl alcohol are measured and compared to MM2 calculated strain energies, ΔSI, between weighted sp3 states and the lowest sp2 state.For unhindered (pseudo)equatorially substituted cycloalkyl tosylates a linear correlation, free from ambiguities involved, e.g., with the leaving group simulation, is obtained which shows a sensitivity of m=1.04+/-0.05, indicating an extremely late transition state or limiting behavior.Based on the corresponding equation, it is shown that alkyl substituents in the γ- and in the β-position do not promote significant rate increases, even when there is an antiperiplanar disposition between the leaving group and a migrating β-methyl substituent.Instead, these substituents can lead to substantial ΔG* increase (by up to 5 kcal/mol in comparison to the ΔSI prediction), which is related to steric hindrance of solvation and/or hindrance for elimination. 17-(Tosyloxy)androstanes show extremely large epimeric rate ratios of>30000; these are not due to anchimeric assistance but only to the exceedingly slow reaction of the hindered 17β isomer, whereas the fast reaction of the 17α tosylate (e.g. 200 times higher than cyclopentyl tosylate) is in line with the ΔSI calculation. endo-Bicycloheptane esters show evidence for steric hindrance; exo-norbornyl tosylate has, however, a ΔG* value lower by 4 kcal/mol than predicted. ks/kc values, obtained by rate comparison in 80percent ethanol and 97percent HFIP, vary between 0.5 and 300, mainly as a result of different steric hindrance to rearside nucleophilic subnstitution
- Schneider, Hans-Joerg,Becker, Norman,Schmidt, Guenther,Thomas, Fred
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p. 3602 - 3607
(2007/10/02)
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- ACTIVATION OF REDUCING AGENTS. SODIUM HYDRIDE CONTAINING COMPLEX REDUCING AGENTS 21. REGIOSELECTIVE REDUCTION OF ALKENE OXIDES
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It is shown that epoxides are reduced by ZnCRA and NiCRA.Interestingly, the simple change in the nature of the metal included in the reagent, changes the regiochemistry of the reduction.
- Fort, Yves,Vanderesse, Regis,Caubere, Paul
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p. 3111 - 3114
(2007/10/02)
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- Hydroboration. 64. Effect of Structure on the Relative Reactivity of Representative Alkenes and Alkynes toward Hydroboration by Dibromoborane-Methyl Sulfide
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The relative reactivities of 22 alkenes and 5 alkynes toward hydroboration by dibromoborane-methyl sulfide (Br2BH*SMe2) have been determined in CH2Cl2 at 25 deg C by the competitive method.The data are compared and contrasted with those available on 9-borabicyclononane (9-BBN), disiamylborane (Sia2BH), and thexylchloroborane-methyl sulfide (ThxBHCl*SMe2).Br2BH*SMe2 exhibits a uniquely high selectivity toward an internal triple bond compared to a terminal triple or double bond, while the reverse is true with 9-BBN.Consequently, 1-octen-4-yne has been selectively converted to (4Z)-1,4-octadiene by hydroboration with Br2BH*SMe2, followed by protonolysis.The terminal double bond, on the other hand, is selectively hydroborated by 9-BBN.The far higher reactivity of Br2BH*SMe2 toward the C(CH3)=CH2 structure, as compared with the CH=CH2 structure makes possible the selective hydroboration of the 1,2-positions of 2-methyl-1,5-hexadiene; Sia2BH, on the other hand, is known to hydroborate the 5,6-positions selectively.Thus we have at hand several monofunctional hydroborating agents with widely different selectivities, making them highly useful for selective hydroborations for synthesis.
- Brown, Herbert C.,Chandrasekharan, J.
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p. 644 - 648
(2007/10/02)
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- Thexylchloroborane-Methyl Sulfide. A Selective Monohydroborating agent with Exceptional regioselectivity
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Thexylchloroborane, readily prepared from 2,3-dimethyl-2-butene and monochloroborane-methyl sulfide in dichloromethane solution, hydroborates representative alkenes with excellent regioselectivity to afford thexylalkylchloroboranes.
- Brown, Herbert C.,Sikorski, James A.,Kulkarni, Surendra U.,Lee, Hsiupu D.
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p. 4540 - 4542
(2007/10/02)
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- Cp2TiCl2-catalyzed grignard reactions. 2. Reactions with ketones and aldehydes
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The reaction of Grignard reagents with ketones or aldehydes in the presence of a catalytic amount of Cp2TiCl2 leads to the corresponding reduction products in high yields. Cp2TiH intermediate was proposed to account for this observation.
- Sato, Fumie,Jinbo, Takamasa,Sato, Masao
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p. 2171 - 2174
(2007/10/02)
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- Stereochemistry of Aliphatic Carbocations, 12. Alkyl Shifts between Secondary Carbon Atoms
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Several optically active, β-branched alkylamines have been synthesized from amino acids.The corresponding amines were obtained from isobutyraldehyde and 2-methylbutanal (37), respectively.The stereochemistry at the terminus of 1,2-methyl shifts has been elucidated in the nitrous acid deaminations of 4 and 21.Predominant, although incomplete inversion at the migration terminus is consistent with conformational control rather than neighboring group participation.The deamination of 31 involves a degenerate 1,2-ethyl shift and a nondegenerate 1,2-methyl shift, the reverse holds for 44.Complete inversion at the origin of the methyl migrations and the absence of subsequent retrogressive H shifts strongly support the intermediacy of methyl-bridged carbocations.Partial racemization at the origin of the ethyl migrations has been traced to proton shifts within ethyl-bridged intermediates.Rearranged open cations contribute significantly to the overall reaction if micelles are produced by self-aggregation of the alkylammonium ions.
- Kirmse, Wolfgang,Prolingheuer, Ernst-Christoph
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p. 104 - 128
(2007/10/02)
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- Stereochemistry of Aliphatic Carbocations, 14. Alkyl Shifts from Secondary to Primary Carbon Atoms
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Alkyl shifts from secondary to primary carbon atoms have been induced by the nitrous acid deamination of suitable amines (4, 22, 39, 51); they include sequential rearrangements (-CH3,CH3 and -CH3,H).Predominant although incomplete inversion at the migration origin has been observed (Me 70percent, Et 62-64percent, nPr 65percent, iPr 64percent, tBu 55percent).Our results require the intervention of open secondary carbocations which may be preceded by less stable bridged intermediates.
- Kirmse, Wolfgang,Guenther, Bernd-Rainer,Knist, Johannes,Kratz, Sigrid,Loosen, Karin,et al.
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p. 2127 - 2139
(2007/10/02)
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- Cp2TiCl2-CATALYZED GRIGNARD REACTIONS. 3. REACTIONS WITH ESTERS: EFFICIENT METHODOLOGY FOR THE SYNTHESIS OF SECONDARY ALCOHOLS AND FOR THE REDUCTION OF ESTERS TO PRIMARY ALCOHOLS
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Cp2TiCl2-catalyzed Grignard reactions with esters provide general methodology for preparation of secondary alcohols or for reduction of esters to the corresponding primary alcohols.
- Sato, Fumie,Jinbo, Takamasa,Sato, Masao
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p. 2175 - 2178
(2007/10/02)
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