- GAS-TO-LIQUID REACTOR AND METHOD OF USING
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A device and a process to propagate molecular growth of hydrocarbons, either straight or branched chain structures, that naturally occur in the gas phase to a molecular size sufficient to shift the natural occurring phase to a liquid or solid state is provided. According to one embodiment, the device includes a grounded reactor vessel having a gas inlet, a liquid outlet, and an electrode within the vessel; a power supply coupled to the electrode for creating an elecirostatic field within the vessel for converting the gas to a liquid and or solid state.
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Paragraph 0143; 0144
(2019/08/15)
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- Sml2-promoted reformatsky-type coupling reactions in exceptionally hindered contexts
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Highly substituted, very hindered enones were synthesized using a two-step procedure that utilizes a diiodosamarium-promoted Reformatsky-type coupling and dehydration using Martin sulfurane. Both α-chloro- and α-bromoketones were coupled with a variety of carbonyl nucleophiles to form the intermediate β-hydroxyketones, occurring with excellent diastereoselectivity, favoring the syn isomer (R1 = Me). This technique complements other methods and enables the preparation of enones outside of the scope of current olefination methodology.
- Sparling, Brian A.,Moslin, Ryan M.,Jamison, Timothy F.
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supporting information; experimental part
p. 1291 - 1294
(2009/04/08)
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- Electrochemical alkyl transfer reactions of trialkylborane to carbonyl compounds by use of copper sacrificial anode
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Alkyl groups in trialkylboranes were successfully transferred to carbonyl compounds in the presence of the platinum cathode and copper anode by electrochemical method. The new, mild electrochemical alkyl transfer reaction produced various substituted alcohols in good yields.
- Choi, Jung Hoon,Youm, Jong Sung,Cho, Cheon-Gyu,Czae, Myung-Zoon,Hwang, Book Kee,Kim, Jung Sung
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p. 4835 - 4838
(2007/10/03)
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- Enantioselective addition of diethylzinc to aldehydes using γ-aminoalcohols derived from α-D-xylose as new chiral catalysts
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The enantioselective addition of diethylzinc to aldehydes using 1,2-isopropylidene-5-deoxy-5-dialkylamino-α-D-xylofuranoses derived from α-D-xylose as new catalysts provided the corresponding alcohols with 75-96% ee.
- Cho, Byung Tae,Kim, Namdu
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p. 4115 - 4118
(2007/10/02)
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- Gas-phase Unimolecular Chemistry of Ethyl Butyl Ketone Cations
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Mass spectra of the four isomeric ethyl butyl ketones, C2H5CO-n-C4H9 (1), C2H5CO-iso-C4H9 (2), C2H5CO-sec-C4H9 (3) and C2H5CO-t-C4H9 (4), are reported.The structure of the fragment ions produced from precursors of both high and low internal energy were identified by collision experiments in a six-sector mass-spectrometer.Metastable molecular ions 1(+.) and 2(+.) behave identically in expelling CH3(.), C3H6 and C2H5(.) to produce the same fragment ions: (+), (+.) and a mixture of (+) and (+), respectively.The key isomerization step between 1(+.) and 2(+.) is a 1,2-enol-olefin shift.Metastable molecular ions 3(+.) and 4(+.) give essentially ethene and ethyl losses, respectively; the fragment ions are (+.) and (+).Keto-enol isomerization also occurs to a significant extent for ions 1(+.) and 2(+.) and 3(+.).In contrast, 1,2- or 1,3-ethylhydroxycarbene migrations are only marginal processes.
- Bouchoux, Guy,Flammang, Robert,Jaudon, Pascale,Lefevre, Odile
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p. 1189 - 1196
(2007/10/02)
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- A Study of Solvent Effects on the Rates of Solvolyses of Pinacolyl Derivatives
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The solvolysis rates of RCH(O3SAr)C(CH3)3 (4a, R = Et, Ar = p-BrPh; 4b, R = i-Pr, Ar = p-BrPh; 4c, R = t-Bu, Ar = p-Tol) and CF3CH(O3SR)C(CH3)3 (6-OBs, R = p-BrPh; 6-OTf, R = CF3) have been determined in mixtures of ethanol and water (the E-W solvent series) and acetic acid and formic acid (the A-F solvent series).Correlations of the rate data by eq 1 neophyl-OTs + c> showed that 4a,b responded similarly to pinacolyl brosylate (1) to the examined solvent effect, yielding separate E-W, A-F regression lines, but with decreased dispersion with increased steric bulk of R.For compound 4c a linear correlation with eq 1 was obtained.These results are interpreted in terms of steric hindrance to electrostatic solvation of the incipient carbocation.The reactivity of the CF3-substituted sulfonate 6-OBs is greatly depressed.The substrate failed to react in the E-W solvent series.Added salt produced enhanced rates of solvolysis of 6-OBs in 25percent AcOH-75percent HCOOH.These results suggest an SN2-like mechanism with very strong electrophilic solvent assistance in the transition state.However, since the solvolysis reactions of 6-OBs are attended with kinetic complexities, the data do not allow a detailed mechanistic interpretation.The solvolytic behavior of 6-OTf stands in sharp contrast to that of 6-OBs.For example, added nucleophilic salts cause only small increases in the rates of solvolysis of 6-OTf in both 70percent EtOH-30percent H2O and 25percent AcOH-75percent HCOOH.Furthemore, the solvolysis rate constants of 6-OTf in all solvents examined correlate with those of 2-adamantyl triflate.These data support a kΔ mechanism for 6-OTf and are discussed in terms of the decreased importance of electrostatic solvation of the forming carbocation from 6-OTf than from pinacolyl brosylate.
- Roberts, Donald D.,Hall, Edward W.
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p. 2573 - 2579
(2007/10/02)
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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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- Hydroboration. 61. Diisopinocampheylborane of High Optical Purity. Improved Preparation and Asymmetric Hydroboration of Representative Cis-Disubstituted Alkenes
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The convenient preparation of diisopinocampheylborane of high enentiomeric purity (99.1percent) utilizing the commercially available relatively stable borane-methyl sulfide and α-pinene of 92percent enantiomeric purity is described.Methyl sulfide liberated in the hydroboration step interferes with the equilibration needed to improve the optical purity of the reagent.However, this difficulty is readily overcome by removal of methyl sulfide under vacuum following hydroboration of the α-pinene.The raegent is then equilibrated in THF with 15percent excess α-pinene at 0 deg C for3 days.During this equilibration period, the major isomer becomes incorporated selectively into the reagent.This high optical purity diisopinocampheylborane has been utilized for asymmetric hydroboration of representative cis-disubstituted alkenes such as cis-2-butene, cis-3-hexene, cis-2-pentene, norbornene, norbornadiene, cis-4,4-dimethyl-2-pentene, and cis-propenylbenzene.Oxidation of the intermediate organoboranes provides the coprresponding alcohols in enantiomeric purities of 60-98percent.
- Brown, Herbert C.,Desai, Manoj C.,Jadhav, Prabhakar K.
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p. 5065 - 5069
(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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