- Direct Synthesis of Hydroquinones from Quinones through Sequential and Continuous-Flow Hydrogenation-Derivatization Using Heterogeneous Au–Pt Nanoparticles as Catalysts
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Pt–Au bimetallic nanoparticle catalysts immobilized on dimethyl polysilane (Pt–Au/(DMPSi-Al2O3)) have been developed for selective hydrogenation of quinones to hydroquinones. High reactivity, selectivity, and robustness of the catalysts were confirmed under continuous-flow conditions. Various direct derivatizations of quinones, such as methylation, acetylation, trifluoromethanesulfonylation, methacrylation, and benzoylation were successfully performed under sequential and continuous-flow conditions to afford the desired products in good to excellent yields. Especially, air-sensitive hydroquinones, such as anthrahydroquinones and naphthohydroquinones, could be successfully generated and derivatized under closed sequential and continuous-flow conditions without decomposition.
- Miyamura, Hiroyuki,Tobita, Fumiya,Suzuki, Aya,Kobayashi, Shū
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supporting information
p. 9220 - 9224
(2019/06/13)
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- Dihedral-Angle-Controlled Crossover from Static Hole Delocalization to Dynamic Hopping in Biaryl Cation Radicals
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In cases of coherent charge-transfer mechanism in biaryl compounds the rates follow a squared cosine trend with varying dihedral angle. Herein we demonstrate using a series of biaryl cation radicals with varying dihedral angles that the hole stabilization
- Talipov, Marat R.,Navale, Tushar S.,Hossain, Mohammad M.,Shukla, Ruchi,Ivanov, Maxim V.,Rathore, Rajendra
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supporting information
p. 266 - 269
(2016/12/30)
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- Direct alkylation of aromatics using alcohols in the presence of NaHSO 4/SiO2
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Simple and efficient procedure for alkylation of aromatics from alcohols in the presence of NaHSO4/SiO2 was developed. Various triaryl methanes were obtained in good yields in short reaction time. For instance the reaction of mesitylene with benzhydrol in the presence of NaHSO4/SiO2 gave the corresponding triaryl methane in a quantitative yield. NaHSO4/SiO2 was regenerated by simple treatment and could be recycled eight times without activity loss.
- Sato, Yuta,Aoyama, Tadashi,Takido, Toshio,Kodomari, Mitsuo
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supporting information; experimental part
p. 7077 - 7081
(2012/08/28)
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- Spiroketal-based phosphorus ligands for highly regioselective hydroformylation of terminal and internal olefins
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A new class of bidentate phosphoramidite ligands, based on a spiroketal backbone, has been developed for the rhodium-catalyzed hydroformylation reactions. A range of short- and long-chain olefins, were found amenable to the protocol, affording high catalytic activity and excellent regioselectivity for the linear aldehydes. Under the optimized reaction conditions, a turnover number (TON) of up to 2.3×104 and linear to branched ratio (l/b) of up to 174.4 were obtained in the RhI-catalyzed hydroformylation of terminal olefins. Remarkably, the catalysts were also found to be efficient in the isomerization-hydroformylation of some internal olefins, to regioselectively afford the linear aldehydes with TON values of up to 2.0×104 and l/b ratios in the range of 23.4-30.6. X-ray crystallographic analysis revealed the cis coordination of the ligand in the precatalyst [Rh(3 d)(acac)], whereas NMR and IR studies on the catalytically active hydride complex [HRh(CO)2(3 d)] suggested an eq-eq coordination of the ligand in the species. Spiro-spine! The effect of a spiro backbone was observed in the rhodium-catalyzed hydroformylation of terminal and internal olefins. High activity and excellent regioselectivity for the formation of linear aldehydes was realized in the case of the matched stereochemistry of the ligand (see scheme). It was found that the spiroketal is superior to biphenyl as the backbone of the ligand in terms of the regioselectivity of hydroformylation. Copyright
- Jia, Xiaofei,Wang, Zheng,Xia, Chungu,Ding, Kuiling
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supporting information
p. 15288 - 15295
(2013/01/15)
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- Nickel-catalyzed Kumada reaction of tosylalkanes with Grignard reagents to produce alkenes and modified arylketones
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Open a new door: The first example of alkene synthesis from alkyl electrophiles with Grignard reagents using the Kumada cross-coupling reaction strategy is reported. This method opens a new door for the Kumada cross-coupling reaction, allowing alkenes to be prepared from the reaction of tosylalkanes with Grignard reagents. Copyright
- Wu, Ji-Cheng,Gong, Lu-Bing,Xia, Yuanzhi,Song, Ren-Jie,Xie, Ye-Xiang,Li, Jin-Heng
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supporting information
p. 9909 - 9913
(2012/10/30)
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- Synthesis of aryl alkyl ethers by alkylation of phenols with quaternary ammonium salts
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Phenolic compounds can be efficiently O-methylated with tetramethylammonium chloride in diglyme or polyethyleneglycol (PEG) at temperatures of 150-160 °C and in the presence of either K2CO3 or NaOH. When applying benzyl-trimethylammonium chloride as a reagent, the benzylation and methylation of phenols occurs, with the benzylation product always predominating. With allyl-substituted phenols as substrates and using NaOH as a base it was possible to achieve both the alkylation and the double-bond isomerization of the allyl group to obtain (E/Z)-propenyl-substituted methyl and benzyl aryl ethers in a single preparative step.
- Maras, Nenad,Polanc, Slovenko,Kocevar, Marijan
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experimental part
p. 29 - 36
(2010/09/05)
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- Rhenium complexes-catalyzed alkylation of arenes with alkyl halides
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Rhenium complexes have been shown to catalyze the alkylation of arenes with alkyl halides. When arenes were reacted with an alkyl chloride in the presence of a catalytic amount of rhenium complexes, such as bromopentacarbonylrhenium(I) [ReBr(CO)5], tricarbonylcyclopentadienylrhenium(I) [Re(C5H5)(CO)3] and decacarbonyldirhenium [Re2(CO)10], alkylation of the arenes proceeded under mild conditions to give a mixture of mono- and dialkyl substituted arenes in moderate-to-good yields.
- Nishiyama,Kakushou,Sonoda
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p. 2779 - 2782
(2007/10/03)
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- Iron Porphyrin-Catalyzed Oxidation of 1,2-Dimethoxyarenes: A Discussion of the Different Reactions Involved and the Competition between the Formation of Methoxyquinones or Muconic Dimethyl Esters
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This paper describes the oxidation of an α,β-diarylpropane lignin dimer model and other dimethoxyarenes by several iron porphyrin-based biomimetic systems.From 1-(3,4-dimethoxyphenyl)-2-phenylpropanol (1), three types of products are identified: the 3,4-dimethoxybenzaldehyde derived from the Cα-Cβ cleavage of the propyl side chain and either quinones or muconic dimethyl esters resulting from oxidations at level of the dimethoxyaryl group.The selectivity of the reaction is discussed with respect to the nature and reactivity of the high-valent iron-oxo species formed upon reaction of the oxidants, H2O2 or magnesium monoperoxyphthalate (MMP), with the iron porphyrins.Fe(TF5PP)Cl-catalyzed oxidation of 1 by H2O2 in an aprotic medium (CH3CN/CH2Cl2), yields a clean "lignin peroxidase-like" reaction with selective formation of the aldehyde.In an aqueous buffered solution, MMP oxidation of para-substituted 1,2-dimethoxyarenes catalyzed by an iron tetrakis(pentafluorophenyl)-β-tetrasulfonatoporphyrin, Fe(TF5PS4P), clearly depends on the electronic properties of the para-substituent.The reaction is selective for para-quinone formation in the case of an electron-releasing group and for muconic dimethyl ester formation in the case of an electron-withdrawing group.
- Artaud, Isabelle,Ben-Aziza, Khaled,Mansuy, Daniel
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p. 3373 - 3380
(2007/10/02)
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- DISPLACEMENT AND ELECTRON-TRANSFER REACTIONS OF SUBSTITUTED 2-CHLORO-1,3,2-BENZODIOXASTIBOLES WITH BASES
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2-Chloro-1,3,2-benzodioxastiboles undergo apparent nucleophilic displacement reactions on antimony in reactions with relatively weak bases.For example, 2-chloro-5-methyl-1,3,2-benzodioxastibole (3) gives 2-(n-butylamino)-5-methyl-1,3,2-benzodioxastibole (14) on treatment with n-butylamine.However, reaction of a 2-chloro-1,3,2-benzodioxastibole with a strong base leads, at least in part, to an apparent electron transfer reaction, with formation of a complex mixture of products.For example, treatment of 2-chloro-5-tert-butyl-1,3,2-benzodioxastibole (2) with phenylmagnesium bromide in tetrahydrofuran, with subsequent acid-catalyzed hydrolysis of the reaction mixture, gives rise to tert-butyl alcohol, catechol, 4-tert-butyl-catechol, phenol, triphenylantimony, biphenyl and methylphenylcarbinol.Key words: benzodioxastiboles; electron transfer; acid-catalyzed hydrolysis; organoantimony; nucleophilic displacement; mechanism.
- McEwen, William E.,Tien, J.-H.,Rembetsy, L. M.,Kalbacher, B. J.,Lubinkowski, Jacek J.,et al.
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p. 153 - 164
(2007/10/02)
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- O-Methylation of tert-Alkylpyrocatecholes. Analytical Method for Determination of the Content of Product Mixtures and Way for Preparation of 4-tert-Alkylveratroles
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The O-methylation of tert-alkylpyrocatecholes with dimethylsulfate leads to a mixture of substituted guaiacoles 6/7, 9/10 and veratroles 5, 6 which are separated by gas/liquid-chromatography for analytical purposes.It is also possible to prepare 4-tert-alkylsubstituted veratroles 5 with good yields in this way.On the other hand, the alkylation of veratrole was only successful with lower tert-alkanols or alkenes.Long-chained tert-alkanols fail in this reaction.The analytical and spectroscopical data of some new 4-tert-alkylveratroles 5a-g are given.
- Beger, J.,Meerbote, M.
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p. 119 - 125
(2007/10/02)
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- Improved Preparation of 5,6-Dialkoxy-1,1-dimethylindenes, Precocene Analogues Lacking the Pyranyl Oxygen Atom
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The use of methanesulfonic acid as solvent and catalyst in the cyclocondensation of 1,2-dialkoxybenzenes with 3-methylbut-2-enoyl chloride to afford indanones 3, thus allowing the preparation of indenes 4 with improved overall yields, is reported.Additionally, structure of dimeric compound 7a, formed in high yield by thermal treatment of 4a has been determined by combination of spectroscopic means and selective deuterations. - Keywords: Precocene Analogues, Methanesulfonic Acid, Indenes
- Camps, F.,Coll, J.,Colomina, O.,Messeguer, A.
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p. 1801 - 1805
(2007/10/02)
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- REACTION OF o-BENZOQUINONE BISACETALS WITH ORGANOLITHIUMS. A NOVEL ROUTE TO SUBSTITUTED VERATROLES
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Substituted veratroles were easily obtained by the reaction of o-benzquinone bisacetals with organolithiums.
- Kikuchi, Yoshiyuki,Hasegawa, Yoko,Matsumoto, Masakatsu
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p. 2199 - 2202
(2007/10/02)
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