23183-11-1Relevant academic research and scientific papers
Aromatic compound hydrogenation and hydrodeoxygenation method and application thereof
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Paragraph 0094-0096; 0098; 0100-0104, (2021/05/29)
The invention belongs to the technical field of medicines, and discloses an aromatic compound hydrogenation and hydrodeoxygenation method under mild conditions and application of the method in hydrogenation and hydrodeoxygenation reactions of the aromatic compounds and related mixtures. Specifically, the method comprises the following steps: contacting the aromatic compound or a mixture containing the aromatic compound with a catalyst and hydrogen with proper pressure in a solvent under a proper temperature condition, and reacting the hydrogen, the solvent and the aromatic compound under the action of the catalyst to obtain a corresponding hydrogenation product or/and a hydrodeoxygenation product without an oxygen-containing substituent group. The invention also discloses specific implementation conditions of the method and an aromatic compound structure type applicable to the method. The hydrogenation and hydrodeoxygenation reaction method used in the invention has the advantages of mild reaction conditions, high hydrodeoxygenation efficiency, wide substrate applicability, convenient post-treatment, and good laboratory and industrial application prospects.
Replacing conventional carbon nucleophiles with electrophiles: Nickel-catalyzed reductive alkylation of aryl bromides and chlorides
Everson, Daniel A.,Jones, Brittany A.,Weix, Daniel J.
supporting information; experimental part, p. 6146 - 6159 (2012/05/07)
A general method is presented for the synthesis of alkylated arenes by the chemoselective combination of two electrophilic carbons. Under the optimized conditions, a variety of aryl and vinyl bromides are reductively coupled with alkyl bromides in high yields. Under similar conditions, activated aryl chlorides can also be coupled with bromoalkanes. The protocols are highly functional-group tolerant (-OH, -NHTs, -OAc, -OTs, -OTf, -COMe, -NHBoc, -NHCbz, -CN, -SO2Me), and the reactions are assembled on the benchtop with no special precautions to exclude air or moisture. The reaction displays different chemoselectivity than conventional cross-coupling reactions, such as the Suzuki-Miyaura, Stille, and Hiyama-Denmark reactions. Substrates bearing both an electrophilic and nucleophilic carbon result in selective coupling at the electrophilic carbon (R-X) and no reaction at the nucleophilic carbon (R-[M]) for organoboron (-Bpin), organotin (-SnMe3), and organosilicon (-SiMe2OH) containing organic halides (X-R-[M]). A Hammett study showed a linear correlation of σ and σ(-) parameters with the relative rate of reaction of substituted aryl bromides with bromoalkanes. The small ρ values for these correlations (1.2-1.7) indicate that oxidative addition of the bromoarene is not the turnover-frequency determining step. The rate of reaction has a positive dependence on the concentration of alkyl bromide and catalyst, no dependence upon the amount of zinc (reducing agent), and an inverse dependence upon aryl halide concentration. These results and studies with an organic reductant (TDAE) argue against the intermediacy of organozinc reagents.
A structure-activity study of Ni-catalyzed alkyl-alkyl kumada coupling. Improved catalysts for coupling of secondary alkyl halides
Ren, Peng,Vechorkin, Oleg,Von Allmen, Kim,Scopelliti, Rosario,Hu, Xile
supporting information; experimental part, p. 7084 - 7095 (2011/06/26)
A structureactivity study was carried out for Ni catalyzed alkylalkyl Kumada-type cross coupling reactions. A series of new nickel(II) complexes including those with tridentate pincer bis(amino)amide ligands (RN2N) and those with bidentate mixed amino-amide ligands (RNN) were synthesized and structurally characterized. The coordination geometries of these complexes range from square planar, tetrahedral, to square pyramidal. The complexes had been examined as precatalysts for cross coupling of nonactivated alkyl halides, particularly secondary alkyl iodides, with alkyl Grignard reagents. Comparison was made to the results obtained with the previously reported Ni pincer complex [( MeN2N)NiCl]. A transmetalation site in the precatalysts is necessary for the catalysis. The coordination geometries and spin-states of the precatalysts have a small or no influence. The work led to the discovery of several well-defined Ni catalysts that are significantly more active and efficient than the pincer complex [(MeN2N)NiCl] for the coupling of secondary alkyl halides. The best two catalysts are [(HNN)Ni(PPh3)Cl] and [(HNN)Ni(2,4-lutidine)Cl]. The improved activity and efficiency was attributed to the fact that phosphine and lutidine ligands in these complexes can dissociate from the Ni center during catalysis. The activation of alkyl halides was shown to proceed via a radical mechanism.
Making Mercury-Ptotosensitized Dehydrodimerization into an Organic Synthetic Method: Vapor Pressure Selectivity and the Behavior of Functionalized Substrates
Brown, Stephen H.,Crabtree, Robert H.
, p. 2935 - 2946 (2007/10/02)
Mercury-photosensitized dehydrodimerization in the vapor phase can be made synthetically useful by taking advantage of a simple reflux apparatus (Figure 1), in which the products promptly condense and are protected from further conversion.This vapor pressure selectivity gives high chemical selectivity even at high conversion and on a multigram scale.Mercury absorbs 254-nm light to give the 3P1 excited state (Hg*), which homolyses a C-H bond of the substrate with a 3o>2o>1o selectivity.Quantitative prediction of product mixtures in alkane dimerization and in alkane-alkane cross-dimerizations is discussed.Radical disproportionation gives alkene, but this intermediate is recycled back into the radical pool via H atom attack, which is beneficial both for yield and selectivity.The method is very efficient at constructing C-C bonds between highly substituted carbon atoms, yet the method fails if a dimer has four sets of obligatory 1,3-syn methyl-methyl steric repulsions, as in the unknown 2,3,4,4,5,5,6,7-octamethyloctane.We have extended the range of substrates susceptible to the reaction, for example to higher alcohols, ethers, silanes, partially fluorinated alcohols, and partially fluorinated ethers.We see selectivity for dimers involving C-H bonds α to O or N and for S-H over C-H.An important advantage of our experimental conditions in the case of alcohols is that the aldehyde or ketone disproportionation product (which is not subject to H. attack) is swept out of the system by the stream of H2 also produced, so it does not remain and inhibit the rate and lower the selectivity. kdis/krec is estimated for a number of radicals studied.The very hindered 3o 1,4-dimethylcyclohex-1-yl radical is notable in having a kdis/krec as high as 7.1.
The Mechanim of Formation of Grignard Reagents: Trapping of Free Alkyl Radical Intermediates by Reaction with Tetramethylpiperidine-N-oxyl
Root, Karen S.,Hill, Craig L.,Lawrence, Lynette M.,Whitesides, George M.
, p. 5405 - 5412 (2007/10/02)
In the presence of the free radical scavenger 2,2,6,6-tetramethylpiperidine-N-oxyl (TMPO., 0.50 M), cycloheptyl bromide (RBr, 0.001 M) reacts with magnesium metal in a solution containing tert-amyl alcohol (5.0 M), lithium bromide (0.05 M), and diethyl ether at 20 deg C and forms N-cycloheptoxy-2,2,6,6-tetramethylpiperidine (TMPOR) as the major product (>/=93percent yield, based on RBr).In the absence of TMPO., cycloheptane (RH) is formed in >/=95percent yield.The dependence of the relative yields of TMPOR and RH on the initial concentration of TMPO. suggests that bothproducts share a common precursor-free cycloheptyl radical-and that this radical has a median lifetime of ca. 1E-7 s.Cycloheptyl radicals appear to be intermediates on the major path to the Grignard reagent cycloheptylmagnesium bromide.TMPO. is reduced by Mg(0) to the anion of the corresponding hydroxylamine, TMPO(1-), at a rate that is competitive with that of the reaction between RBr and Mg(0).Although the magnesium salts of TMPO(1-) are insoluble in diethyl ether, solutions containing TMPO(1-), Mg(2+), and Li(1+) remain homogeneous.For systems containing a high concentration of tert-amyl alcohol, a simple mathematical model attributes apparent zero-order kinetic behavior to the dependence of reactive surface area on the extent of reaction between alkyl halide and Mg.
DECOMPOSITION DU PERCARBONATE DE O,O-t-BUTYLE ET O-ISOPROPENYLE EN SOLUTION DANS DES CYCLANES
Jaouhari, R.,Filliatre, C.,Maillard, B.,Villenave, J.J.
, p. 3137 - 3142 (2007/10/02)
Thermolysis of O,O-t-butyl and O-isopropenyl percarbonate in cyclohexane involves free-radical acetonylation of solvent.Free radicals derived from solvent add to the percarbonate double bond and after a double β-scission reaction, cyclohexylacetone carbon dioxide and t-butoxy radicals are formed.Abstracting H atoms from the solvent, t-butoxy radicals regenerate free radicals from solvent, and the reaction becomes a chain process.Extending the study to other cycloalkanes it has been shown that the process is a general synthesis method for cycloalkylacetones.On the other hand, competitive reactions of pairs of solvents have shown that the reactivity of the substrates depends on H atom lability and on more complex phenomena like transfers between hydrocarbons and C-centred free-radicals.
