- The Silicon-Hydrogen Exchange Reaction: A Catalytic σ-Bond Metathesis Approach to the Enantioselective Synthesis of Enol Silanes
-
The use of chiral enol silanes in fundamental transformations such as Mukaiyama aldol, Michael, and Mannich reactions as well as Saegusa-Ito dehydrogenations has enabled the chemical synthesis of enantiopure natural products and valuable pharmaceuticals. However, accessing these intermediates in high enantiopurity has generally required the use of either stoichiometric chiral precursors or stoichiometric chiral reagents. We now describe a catalytic approach in which strongly acidic and confined imidodiphosphorimidates (IDPi) catalyze highly enantioselective interconversions of ketones and enol silanes. These "silicon-hydrogen exchange reactions"enable access to enantiopure enol silanes via tautomerizing σ-bond metatheses, either in a deprotosilylative desymmetrization of ketones with allyl silanes as the silicon source or in a protodesilylative kinetic resolution of racemic enol silanes with a carboxylic acid as the silyl acceptor.
- Zhou, Hui,Bae, Han Yong,Leutzsch, Markus,Kennemur, Jennifer L.,Bécart, Diane,List, Benjamin
-
supporting information
p. 13695 - 13700
(2020/08/24)
-
- Pd nanoparticles/polyoxometalate-ionic liquid composites on SiO2 as multifunctional catalysts for efficient production of ketones from diaryl ethers
-
The high stability of C-O bonds in diaryl ethers limits the valorization of lignin. Herein, reductive hydrolysis of C-O bonds in diaryl ethers was achieved over Pd nanoparticle/polyoxometalate-ionic liquid composite supported on SiO2 (Pd/H2[POM-IL]@SiO2) in water, selectively yielding ketones free from their alcohol counterparts in unprecedentedly high yields (>80%).
- Zhang, Zhanrong,Liu, Mingyang,Song, Jinliang,Liu, Huizhen,Xie, Zhenbing,Liu, Shuaishuai,Meng, Qinglei,Zhang, Pei,Han, Buxing
-
p. 4865 - 4869
(2018/11/21)
-
- Conversion of lignin model compounds under mild conditions in pseudo-homogeneous systems
-
To produce basic chemicals from lignin, depolymerization and removal of oxygen from lignin through C-O cleavage and hydrodeoxygenation (HDO) are crucial steps. In this study, a novel, pseudo-homogeneous catalyst system, consisting of uniformly stabilized noble metal nanoparticles (NPs) in ionic liquids is developed for the selective reductive cleavage of C-O and HDO. Phenol and guaiacol as lignin monomer model compounds are investigated to gain an insight into the possible HDO pathway, meanwhile, dimeric model compounds such as diphenyl ether and benzyl phenyl ether are studied for the cleavage of C-O bonds between aromatic units. Four types of NPs including Pd, Pt, Rh and Ru were synthesized in situ and well distributed in ILs without aggregation. These catalytic systems displayed almost 100% conversion for various monomeric and dimeric lignin model compounds at 130°C and were recycled several times without loss of activity. The catalytic selectivity of metals for HDO/C-O cleavage normally decreases in the order of Pt > Rh ～ Ru ? Pd, which is similar to the order of NP size, Pd ? Pt > Rh ～ Ru. With a mean diameter of 5.6 nm, Pt NPs in [Bmim]PF6 are identified as the best catalytic system for the transformation of lignin monomeric and dimeric model compounds with an almost 100% conversion and maximum 97% selectivity.
- Chen, Lu,Xin, Jiayu,Ni, Lingli,Dong, Huixian,Yan, Dongxia,Lu, Xingmei,Zhang, Suojiang
-
supporting information
p. 2341 - 2352
(2016/05/19)
-
- Promising Ni/Al-SBA-15 catalysts for hydrodeoxygenation of dibenzofuran into fuel grade hydrocarbons: Synergetic effect of Ni and Al-SBA-15 support
-
This work has been undertaken with the aim of designing promising noble-metal-free catalysts for efficient hydrodeoxygenation (HDO) of dibenzofuran (DBF) into fuel grade hydrocarbons. For this, various Ni/Al-SBA-15 catalysts with different Si/Al (50, 60, 70 and 80) mole ratios were synthesized and their catalytic performance was tested for HDO of DBF in a batch reactor. The catalysts were systematically characterized using XRD, N2-adsorption-desorption, Raman, H2-TPR, NH3-TPD, XRF, and FESEM techniques. The activity results showed that the HDO of DBF proceeds via hydrogenation of benzene on the Ni sites followed by cleavage of C-O bonds on the acidic sites of the catalyst to yield unsaturated hydrocarbons. Further hydrogenation of unsaturated hydrocarbons on the Ni sites gives bicyclohexane as the major product. Remarkably, a 100% DBF conversion was found for all the catalysts except for Ni/SBA-15 and Ni/Al-SBA-15(80) (Si/Al mole ratio = 80) catalysts, which showed 97.97 and 99.31%, respectively. A significant observation noticed in this study is that the incorporation of Al into Ni/SBA-15 results in an outstanding improvement in the selectivity of the bicyclohexane product. Among the catalysts tested, the Ni/Al-SBA-15(50) (Si/Al mole ratio = 50) catalyst showed the highest efficiency, with superior selectivity of ～87% for bicyclohexane and ～96% degree of deoxygenation at 10 MPa, 260 °C and 5 h. The obtained structure-activity results reveal the synergetic effect of Ni and support in HDO of DBF reaction: the concentration of acidic sites has a significant effect on the selectivity of the desired products.
- Gbadamasi, Sharafadeen,Ali, Tammar Hussein,Voon, Lee Hwei,Atta, Abdulazeez Yusuf,Sudarsanam, Putla,Bhargava, Suresh K.,Abd Hamid, Sharifah Bee
-
p. 25992 - 26002
(2016/03/25)
-
- Effective hydrodeoxygenation of dibenzofuran by a bimetallic catalyst in water
-
Effective hydrodeoxygenation (HDO) of dibenzofuran (DBF) catalyzed by a bimetallic nickel/platinum (Ni/Pt) catalyst in water was demonstrated at 200 °C and 1.2 MPa hydrogen (H2) pressure. The bimetallic catalysts prepared by a wet chemical method exhibit prominent activity that overcomes the limitations of use of a single Ni or Pt metal catalyst. The yield of HDO products can be up to 90%. Reaction results indicate that the conversion of DBF was affected by the reaction temperature and H2 pressure. The deoxygenation selectivity was strongly dependent on reaction temperature. The reaction pathway is also proposed.
- Dong, Peng,Lu, Guo-Ping,Cai, Chun
-
p. 1605 - 1609
(2016/02/19)
-
- Cu/Mg/Al/Zr non-noble metal catalysts for o-phenylphenol synthesis
-
Cu/Mg/Al/Zr hydrotalcite-like precursors with Zr4+:(Al3+ + Zr4+) atomic ratios between 0 and 1 were prepared by co-precipitation methods. The precursors were analyzed using X-ray diffraction (XRD), scanning electron microscopy (SEM), thermogravimetric (TG) analysis and Fourier transform infrared spectroscopy (FT-IR). The results confirmed that well-defined layered double hydroxides (LDH) can be synthesized when the added Zr content is less than 0.25 in terms of Zr4+/(Al3+ + Zr4+) atomic ratio. The catalysts of Cu/Zn/Al/Zr mixed oxides can be obtained via thermal decomposition of hydroxide precursors, and can be used in dehydrogenation of 2-(1-cyclohexenyl) cyclohexanone (CHCH) to ortho-phenylphenol (OPP). Copper particles inside the catalyst act as active sites for dehydrogenation. Transmission electron microscopy (TEM), XRD, N2O chemisorption and N2 adsorption-desorption were performed to investigate the effect of Zr content on determining the copper particle size. Based on the catalytic performance test, it was concluded that the conversion of CHCH depends on the copper particle size of these catalysts.
- Zeng, Yongping,Zhang, Tianchi,Xu, Yueyang,Hu, Peili,Ye, Ting,Jia, Zhehua,Ju, Shengui
-
p. 6737 - 6746
(2016/02/03)
-
- Highly Selective Hydrogenation of Aromatic Ketones and Phenols Enabled by Cyclic (Amino)(alkyl)carbene Rhodium Complexes
-
Air-stable Rh complexes ligated by strongly σ-donating cyclic (amino)(alkyl)carbenes (CAACs) show unique catalytic activity for the selective hydrogenation of aromatic ketones and phenols by reducing the aryl groups. The use of CAAC ligands is essential for achieving high selectivity and conversion. This method is characterized by its good compatibility with unsaturated ketones, esters, carboxylic acids, amides, and amino acids and is scalable without detriment to its efficiency.
- Wei, Yu,Rao, Bin,Cong, Xuefeng,Zeng, Xiaoming
-
supporting information
p. 9250 - 9253
(2015/08/11)
-
- Clean borrowing hydrogen methodology using hydrotalcite supported copper catalyst
-
The catalytic activity of Mg-Al hydrotalcite supported copper catalyst was investigated for clean CC and CN bond forming reactions using alcohols as alkylating agent via borrowing hydrogen methodology. The catalyst showed excellent conversion of ketone and amine substrates (71-99%) to alkylated products with high selectivity in alkylation reactions.
- Dixit, Manish,Mishra, Manish,Joshi, Pradyuman A.,Shah, Dinesh O.
-
-
- A boron-based synthesis of the natural product (+)-trans- dihydrolycoricidine
-
Diastereoselective diboration results in the highly selective 1,4-dihydroxylation of chiral cyclohexadienes (see scheme). Together with the catalytic enantioselective conjugate allylboration, the diene diboration facilitates the asymmetric synthesis of the cytotoxic agent (+)-trans- dihydrolycoricidine (1). pin=pinacol. Copyright
- Poe, Sarah L.,Morken, James P.
-
supporting information; experimental part
p. 4189 - 4192
(2011/06/20)
-
- Comparative dehydrogenation of cyclohexanol to cyclohexanone with commercial copper catalysts: Catalytic activity and impurities formed
-
Catalytic dehydrogenation of cyclohexanol to cyclohexanone has been carried out on phase gas in a continuous fixed bed reactor under atmospheric pressure. Copper chromite and copper zinc oxide catalysts have been checked. Effect of temperature (in the range 250-290 °C) and spatial time in reactor have been studied. The catalytic activity has been evaluated in terms of cyclohexanone yields and impurities from secondary reactions of dehydration and dehydrogenation of cyclohexanol have also been identified and quantified by GC/MS. Catalysts have been characterized by X-ray diffraction, temperature programmed desorption of ammonia and BET surface area measurement. High activity was confirmed by copper-based catalysts under the operating conditions, concerning the size and dispersion of the copper specie. It was also found that catalysts with alumina and chromium exhibit higher dehydration capacity, being cyclohexene the main impurity obtained. For a given cyclohexanone yield the impurities from dehydrogenation reactions showed similar trends for the three catalysts tested. Phenol was the main impurity obtained by dehydrogenation.
- Romero, Arturo,Santos, Aurora,Escrig, Daniel,Simón, Ernesto
-
experimental part
p. 19 - 27
(2011/11/07)
-
- Catalytic asymmetric hydrolysis: Asymmetric hydrolytic protonation of enol esters catalyzed by phase-transfer catalysts
-
Like an enzyme: Asymmetric hydrolysis of enol esters is accomplished by chiral phase-transfer catalysts under biphasic base hydrolysis conditions. Stoichiometric reactions support the generation of a well-organized chiral ammonium hydroxide species (Q+OH-). Copyright
- Yamamoto, Eiji,Nagai, Ayano,Hamasaki, Akiyuki,Tokunaga, Makoto
-
p. 7178 - 7182
(2011/08/03)
-
- An investigation into cyclohexanone ammoximation over Ti-MWW in a continuous slurry reactor
-
In the present study, the liquid-phase ammoximation of cyclohexanone with ammonia and hydrogen peroxide was studied using a MWW-type titanosilicate (Ti-MWW) catalyst in a continuous slurry reactor to develop a clean process for producing cyclohexanone oxime. The reaction parameters, which governed the cyclohexanone conversion, oxime selectivity and catalyst deactivation, were investigated by simulating the operating conditions of an industrial process. Under optimized reaction conditions, Ti-MWW produced a cyclohexanone conversion and oxime selectivity over 96% and 99%, respectively. Moreover, Ti-MWW was extremely robust and showed a longer lifetime than the conventional titanium silicalite-1 catalyst. The causes of deactivation were elucidated to be the coke deposition and partial dissolution of the zeolite framework of Ti-MWW during ammoximation. The deactivated Ti-MWW catalyst was regenerated effectively by a combination of acid treatment and cyclic amine-assisted structural rearrangement.
- Zhao, Song,Xie, Wei,Yang, Junxia,Liu, Yueming,Zhang, Yingtian,Xu, Biliang,Jiang, Jin-Gang,He, Mingyuan,Wu, Peng
-
experimental part
p. 1 - 8
(2011/12/16)
-
- Induced allostery in the directed evolution of an enantioselective Baeyer-Villiger monooxygenase
-
The molecular basis of allosteric effects, known to be caused by an effector docking to an enzyme at a site distal from the binding pocket, has been studied recently by applying directed evolution. Here, we utilize laboratory evolution in a different way, namely to induce allostery by introducing appropriate distal mutations that cause domain movements with concomitant reshaping of the binding pocket in the absence of an effector. To test this concept, the thermostable Baeyer-Villiger monooxygenase, phenylacetone monooxygenase (PAMO), was chosen as the enzyme to be employed in asymmetric Baeyer-Villiger reactions of substrates that are not accepted by the wild type. By using the known X-ray structure of PAMO, a decision was made regarding an appropriate site at which saturation mutagenesis is most likely to generate mutants capable of inducing allostery without any effector compound being present. After screening only 400 transformants, a double mutant was discovered that catalyzes the asymmetric oxidative kinetic resolution of a set of structurally different 2-substituted cyclohexanone derivatives as well as the desymmetrization of three different 4-substituted cyclohexanones, all with high enantioselectivity. Molecular dynamics (MD) simulations and covariance maps unveiled the origin of increased substrate scope as being due to allostery. Large domain movements occur that expose and reshape the binding pocket. This type of focused library production, aimed at inducing significant allosteric effects, is a viable alternative to traditional approaches to designed directed evolution that address the binding site directly.
- Wu, Sheng,Acevedo, Juan Pablo,Reetz, Manfred T.
-
experimental part
p. 2775 - 2780
(2010/10/03)
-
- Reductive amination of cyclohexanone in the presence of cyclohexanol over zeolites Hβ and HY
-
Reductive amination of a mixture of cyclohexanone/cyclohexanol in varying proportions has been carried out in the gas phase over zeolites Hβ and HY. The products identified were cyclohexylamine, N-cyclohexylcyclohexanimine, 2-cyclohexen-1-ylcyclohexanone and 2-cyclohexylcyclohexanone. The product distribution during the experiments indicates that cyclohexanol does not undergo reductive amination over acid catalysts; it only forms a condensation product with cyclohexanone. The reaction rates were obtained from experimental data and fit to a kinetic model derived for this reaction. The fits show that this reaction follows a Langmuir-Hinshelwood pathway by the adsorption of both cyclohexanone and the NH3 on the surface of the zeolite.
- Kirumakki, Sharath R.,Papadaki, Maria,Chary, Komandur V.R.,Nagaraju
-
experimental part
p. 15 - 21
(2010/10/04)
-
- Efficient aerobic oxidation of alcohols using a hydrotalcitesupported gold nanoparticle catalyst
-
Hydrotalcite-supported gold nanoparticles (Au/HT) were found to be a highly efficient heterogeneous catalyst for the aerobic oxidation of alcohols under mild reaction conditions (4O°C, in air). This catalyst system does not require any additives and is applicable to a wide range of alcohols, including less reactive cyclohexanol derivatives. This Au/HT catalyst could also function in the oxidation of 1-phenylethanol under neat conditions; the turnover number (TON) and turnover frequency (TOF) reached 200,000 and 8,300 h -1, respectively. These values are among the highest values compared to those of other reported catalyst systems at high conversion. Moreover, the Au/HT can be recovered by simple filtration and reused without any loss of its activity and selectivity.
- Mitsudome, Takato,Noujima, Akifumi,Mizugaki, Tomoo,Jitsukawa, Koichiro,Kaneda, Kiyotomi
-
scheme or table
p. 1890 - 1896
(2011/03/18)
-
- Laboratory evolution of robust and enantioselective Baeyer-Villiger monooxygenases for asymmetric catalysis
-
The Baeyer-Villiger Monooxygenase, Phenylacetone Monooxygenase (PAMO), recently discovered by Fraaije, Janssen, and co-workers, is unusually thermostable, which makes it a promising candidate for catalyzing enantioselective Baeyer-Villiger reactions in organic chemistry. Unfortunately, however, its substrate scope is very limited, reasonable reaction rates being observed essentially only with phenylacetone and similar linear phenyl-substituted analogs. Previous protein engineering attempts to broaden the range of substrate acceptance and to control enantioselectivity have been met with limited success, including rational design and directed evolution based on saturation mutagenesis with formation of focused mutant libraries, which may have to do with complex domain movements. In the present study, a new approach to laboratory evolution is described which has led to mutants showing unusually high activity and enantioselectivity in the oxidative kinetic resolution of a variety of 2-aryl and 2-alkylcyclohexanones which are not accepted by the wild-type (WT) PAMO and of a structurally very different bicyclic ketone. The new strategy exploits bioinformatics data derived from sequence alignment of eight different Baeyer-Villiger Monooxygenases, which in conjunction with the known X-ray structure of PAMO and induced fit docking suggests potential randomization sites, different from all previous approaches to focused library generation. Sites harboring highly conserved proline in a loop of the WT are targeted. The most active and enantioselective mutants retain the high thermostability of the parent WT PAMO. The success of the "proline" hypothesis in the present system calls for further testing in future laboratory evolution studies.
- Reetz, Manfred T.,Wu, Sheng
-
supporting information; experimental part
p. 15424 - 15432
(2010/02/16)
-
- A bronsted acid catalyst for the enantioselective protonation reaction
-
A highly reactive and robust chiral Bronsted acid catalyst, chiral N-triflyl thiophosphoramide, was developed. The first metal-free Bronsted acid catalyzed enantioselective protonation reaction of silyl enol ethers was demonstrated using this chiral Bronsted acid catalyst. The catalyst loading could be reduced to 0.05 mol % without any deleterious effect on the enantioselectivity. Copyright
- Cheol, Hong Cheon,Yamamoto, Hisashi
-
supporting information; scheme or table
p. 9246 - 9247
(2009/02/02)
-
- Regioselective α-alkylation of ketones with alkyl chlorides and fluorides via highly nucleophilic magnesium enamides
-
A magnesium enamide derived from N-2-(N′,N′-dimethylamino)ethyl imine reacts with primary and secondary alkyl chlorides and fluorides to give an α-alkylated ketone in good to excellent yields upon hydrolysis of the imine moiety. Reactions of the highly nucleophilic magnesium enamide derived from an unsymmetrical ketone take place regioselectively. In addition, the C-C bond formation is stereospecific: a substantial inversion of stereochemistry at the electrophilic carbon center (Walden inversion) was observed, proving its potential utility for the production of optically active compounds.
- Hatakeyama, Takuji,Ito, Shingo,Yamane, Hiroaki,Nakamura, Masaharu,Nakamura, Eiichi
-
p. 8440 - 8448
(2008/02/08)
-
- Tetrabutylammonium decatungstate-photosensitized alkylation of electrophilic alkenes: Convenient functionalization of aliphatic C-H bonds
-
Tetrabutylammonium decatungstate (TBADT, 2×10-3M) is an effective photocatalyst for the alkylation of electrophilic alkenes (0.1 M, α,β-unsaturated nitriles, esters, ketones) by alkanes, alcohols, and ethers. The products are in most cases obtained in >70% isolated yields, through an experimentally very simple procedure. The kinetics of the radical processes following initial hydrogen abstraction by excited TBADT in deoxygenated MeCN have been studied. In the absence of a trap, back hydrogen transfer from reduced tungstate is the main pathway for alkyl radicals, while α-hydroxyalkyl radicals are oxidized to ketones by ground-state TBADT. With both radical types the reaction ceases at a few percent conversion. However, trapping by electrophilic alkenes is followed by reduction of the radical adduct and regeneration of the catalyst, which allows the alkylation to proceed up to complete alkene conversion with the mentioned good yields of products. With a nucleophilic (α-hydroxyalkyl) radical, alkylation is efficient (Φ = 0.58) and can also be carried out when degassing is omitted, the only difference being a short induction period. With a less reactive (cyclohexyl) radical, the quantum yield is lower (Φ = 0.06) and the reaction is considerably slowed in aerated solutions, but the chemical yield remains good.
- Dondi, Daniele,Fagnoni, Maurizio,Albini, Angelo
-
p. 4153 - 4163
(2007/10/03)
-
- Palladium-catalyzed intramolecular hydroalkylation of alkenyl- β-keto esters, α-aryl ketones, and alkyl ketones in the presence of Me 3SiCl or HCI
-
Reaction of 3-butenyl β-keto esters or 3-butenyl α-aryl ketones with a catalytic amount of [PdCl2(CH3CN)2] (2) and a stoichiometric amount of Me3SiCl or Me3SiCl/ CuCl2 in dioxane at 25-70°C formed 2-substituted cyclohexanones in good yield with high regioselectivity. This protocol tolerated a number of ester and aryl groups and tolerated substitution at the allylic, enolic, and cis and trans terminal olefinic positions. In situ NMR experiments indicated that the chlorosilane was not directly involved in palladium-catalyzed hydroalkylation, but rather served as a source of HCl, which presumably catalyzes enolization of the ketone. Identification of HCl as the active promoter of palladium-catalyzed hydroalkylation led to the development of an effective protocol for the hydroalkylation of alkyl 3-butenyl ketones that employed sub-stoichiometric amounts of 2, HCl, and CuCl2 in a sealed tube at 70°C.
- Han, Xiaoqing,Wang, Xiang,Pei, Tao,Widenhoefer, Ross A.
-
p. 6333 - 6342
(2007/10/03)
-
- Catalytic cross-coupling of alkylzinc halides with α-chloroketones
-
The cross-coupling of alkylzinc halides with α-chloroketones catalyzed by Cu(acac)2 is described. Using this method, primary and secondary alkyl groups are introduced adjacent to a ketone carbonyl under mild reaction conditions and in good yield. Cyclic, acyclic, aromatic, and aliphatic α-chloroketones are suitable substrates. Optically active α-chloroketones are converted to optically active products. The reaction was found to proceed stereospecifically with inversion of stereochemistry. The reaction is proposed to occur by direct substitution of the chloride with the alkyl group of an organocopper, -magnesium, or -zinc species. Copyright
- Malosh, Chrysa F.,Ready, Joseph M.
-
p. 10240 - 10241
(2007/10/03)
-
- Unfunctionalized, α-epimerizable nonracemic ketones and aldehydes can be accessed by crystallization-induced dynamic resolution of imines
-
This paper describes an operationally simple deracemization process of aldehydes and ketones. This new crystallization-induced dynamic resolution (CIDR) protocol allows for nearly complete conversion of the racemic mixture into one enantiomer. Crystallization of imines derived from racemic ketones or aldehydes 1 and trans-(1R,2R)-1-amino-6-nitroindan-2-ol (2) afforded diastereomerically pure, crystalline imines 3. Biphasic hydrolysis of 3 then affords recovered 2 and enantiomerically enriched 1 in high yield and er (substrate, yield/ee: 2-methylcyclohexanone, 97%/92; 2-ethylhexanal, 94%/98; 2-methylcyclopentanone, 94%/98; 2-cyclohexylcyclohexanone, ND/98; 3-methyl-2-pentanone, ND/76). The scope, limitations, and industrial perspective of this process are discussed. This highly effective CIDR process is likely due to π-stacking of 2 and a hydrogen bonding of the imine with the free hydroxyl of 2 in the solid state. Copyright
- Kosmrlj, Janez,Weigel, Leland O.,Evans, David A.,Downey, C. Wade,Wu, Jimmy
-
p. 3208 - 3209
(2007/10/03)
-
- Palladium-catalyzed intramolecular hydroalkylation of unactivated olefins with dialkyl ketones
-
(Matrix presented) Treatment of 3-butenyl heptyl ketone with substoichiometric amounts of PdCl2(CH3CN)2 (10 mol%), HCl (0.1 equiv), and CuCl2 (0.3 equiv) in dioxane at 70°C for 12 h in a sealed tube formed 2-hexylcyclohexanone in 77% isolated yield. A number of alkyl 3-butenyl ketones underwent hydroalkylation under these conditions to form 2-substituted cyclohexanones in moderate to good yield.
- Wang, Xiang,Pei, Tao,Han, Xiaoqing,Widenhoefer, Ross A.
-
p. 2699 - 2701
(2007/10/03)
-
- Amidino derivatives useful as nitric oxide synthase inhibitors
-
The current invention discloses useful pharmaceutical compositions containing amidino derivative useful as nitric oxide synthase inhibitors.
- -
-
-
- Amidino dervatives useful as nitric oxide synthase inhibitors
-
The current invention discloses useful pharmaceutical compositions containing azepine derivatives useful as nitric oxide synthase inhibitors.
- -
-
-
- Catalytic oxidation of alkyl- and cycloalkylcyclanones into lactones
-
Pilot-plant syntheses of alkyl and cycloalkylcyclanones and their subsequent liquid-phase oxidation into lactones are described. Characteristics of resulting intermediates and target products are reported.
- Abbasov,Alimardanov,Suleimanova
-
p. 621 - 626
(2007/10/03)
-
- Classical Organic Reactions in Pure Superheated Water
-
At high temperatures and pressures, pure liquid water becomes a surprisingly effective medium for the reactions of organic compounds.It may function simultaneously as a convenient solvent, catalyst, and reagent for reactions which are typically acid- or base-catalyzed.Rapid and highly selective conversion are observed for the majority of the compounds in this study.
- Kuhlmann, Barbara,Arnett, Edward M.,Siskin, Michael
-
p. 3098 - 3101
(2007/10/02)
-
- CONVERSION OF DIMERIC PRODUCT OF CYCLOHEXANONE CONDENSATION ON ALUMINOMETALLIC CATALYSTS
-
The possibility of preparing 2-phenylphenol by catalytic dehydrogenation of 2-(cyclohexen-1-yl)-cyclohexanone was studied.Conversions of initial and intermediate compounds on alumina and aluminoplatinum and aluminopalladium catalysts at 100-375 deg C were examined for clarifying the mechanism of this reaction.
- Gorchakova, E. N.,Sibarov, D. A.,Fedorov, V. S.,Proskuryakov, V. A.
-
p. 1291 - 1295
(2007/10/02)
-
- A Convenient Preparation of Ketones by the Oxidation of Secondary Alcohols with Chromium(VI) Trioxide in Aprotic Solvent in the Presence of "Wet"-Aluminium Oxide
-
The oxidation of aliphatic and alicyclic secondary alcohols with chromium(VI) trioxide in the presence of "wet"-aluminium oxide in hexane gave the corresponding ketones in excellent yields under mild conditions.
- Hirano, Masao,Nagasawa, Sonoko,Morimoto, Takashi
-
p. 2857 - 2859
(2007/10/02)
-
- CYCLIC HYDROCARBONS WITH AN AMINOALKYL SIDECHAIN
-
Provided are cyclic hydrocarbons of Formula I with an aminoalkyl sidechain that are useful for treating phospholipase A2 mediated conditions, diabetes, and obesity.
- -
-
-
- Hydroalkylation of Phenol to Cyclohexylphenyl in the Presence of Pd-Al2O3 and NaCl-AlCl3 under Hydrogen Pressure
-
The hydroalkylation of phenol (1) in the presence of palladium catalyst and fused salt (NaCl-AlCl3) under hydrogen pressure was carried out.By using 1percent Pd-Al2O3 (1g) and the fused salt (1:1 mol ratio, 6g), 4-cyclohexyphenol (6) was obtained selectively from 1 (30g) in a yield of 31.9 percent at 120 deg C for 4.5 h.Cyclohexylphenols were formed by way of 2-cyclohexen-1-ol and 1.Keywords-hydroalkylation; palladium catalyst; fused salt; phenol; 2-cyclohexylphenol; 4-cyclohexylphenol; 2-cyclohexylcyclohexanone
- Kamiyama, Tsutomu,Enomoto, Saburo,Inoue, Masami
-
p. 450 - 454
(2007/10/02)
-
- Reactions of Cyclohexanone with Metal Vapors
-
Metal atom vapors of several d and f transition elements were cocondensed with cyclohexanone at -196 deg C.Radical reduction of cyclohexanone to -1,1'-diol, a pinacol, was observed for elements which are both highly electropositive and form strong metal-oxygen bonds, for example, the early transition, lanthanide, and actinide elements.High yields of aldol condensation products were produced along with a small amount of bicyclohexylidene.Metal atoms of the latter transition elements were much less reactive with cyclohexanone and did not yield a pinacol product.Titanium clusters were prepared by codepositing titanium atoms with a large excess of solvent.Titanium clusters were less reactive than titanium atoms toward cyclohexanone radical reduction reactions.High surface area titanium powders produced by solution techniques yield pinacols when cyclohexanone reacts in excess and further deoxygenate pinacolic dianions to olefins under conditions of limited stoichiometry.
- Miller, Jeffrey T.,DeKock, Carroll W.
-
p. 516 - 520
(2007/10/02)
-
- PHOTOCHEMISTRY OF HALOKETONES-I. REACTIONS OF SOME α-HALOCYCLOHEXANONES
-
α-Halocyclohexanones 1-4 on irradiation in cyclohexane have been found to involve competing radical and ionic photo-behaviour.The principal photoprocess observed in α-chloro-, α-bromo-, α-iodo-cyclohexanones was homolytic β-cleavage of carbon-halogen bond to afford radical products.These were usually accompanied by ionic products such as cyclohexenones, but in much lower proportions.Photo-Favorskii type ring contraction reported recently for α-chlorocyclobutanones was found to be completely absent.Sensitisation and quenching studies indicate that radical cleavage occurs from n-?* triplet states whereas ionic cleavage could be a singlet derived reaction; thus providing for the first time experimental support to the proposed Wagner-model for the cleavage of carbon-halogen bond in α-haloketones.
- Purohit, P.C.,Sonawane, H.R.
-
p. 873 - 877
(2007/10/02)
-
- STEREOSELECTIVITE DE L'ADDITION DE REACTIFS NUCLEOPHILES SUR DES CETONES POLYCYCLIQUES A JONCTION TRANS
-
The nucleophilic additions of hindered organometallic compounds to polycyclic ketones with trans ring junctions involve predominant axial attack when flattening of the ring containing the carbonyl group occurs.The influence of nucleophile structure (O-Por C-metalled character) on equatorial or axial attack is discussed.
- Calmes, D.,Gorrichon-Guigon, L.,Maroni, P.,Accary, A.,Barret, R.,Huet, J.
-
p. 879 - 885
(2007/10/02)
-
- UNUSUAL REDUCTIVE CONDENSATIONS IN THE REACTION OF DIIODODIMETHYLSILANE WITH KETONES
-
Diiododimethylsilane reacts with various ketones in the presence of zinc to give the corresponding reductive condensation products in good yields.
- Ando, Wataru,Ikeno, Masayuki
-
p. 1255 - 1256
(2007/10/02)
-
