- Deciphering Reactivity and Selectivity Patterns in Aliphatic C-H Bond Oxygenation of Cyclopentane and Cyclohexane Derivatives
-
A kinetic, product, and computational study on the reactions of the cumyloxyl radical with monosubstituted cyclopentanes and cyclohexanes has been carried out. HAT rates, site-selectivities for C-H bond oxidation, and DFT computations provide quantitative information and theoretical models to explain the observed patterns. Cyclopentanes functionalize predominantly at C-1, and tertiary C-H bond activation barriers decrease on going from methyl- and tert-butylcyclopentane to phenylcyclopentane, in line with the computed C-H BDEs. With cyclohexanes, the relative importance of HAT from C-1 decreases on going from methyl- and phenylcyclohexane to ethyl-, isopropyl-, and tert-butylcyclohexane. Deactivation is also observed at C-2 with site-selectivity that progressively shifts to C-3 and C-4 with increasing substituent steric bulk. The site-selectivities observed in the corresponding oxidations promoted by ethyl(trifluoromethyl)dioxirane support this mechanistic picture. Comparison of these results with those obtained previously for C-H bond azidation and functionalizations promoted by the PINO radical of phenyl and tert-butylcyclohexane, together with new calculations, provides a mechanistic framework for understanding C-H bond functionalization of cycloalkanes. The nature of the HAT reagent, C-H bond strengths, and torsional effects are important determinants of site-selectivity, with the latter effects that play a major role in the reactions of oxygen-centered HAT reagents with monosubstituted cyclohexanes.
- Martin, Teo,Galeotti, Marco,Salamone, Michela,Liu, Fengjiao,Yu, Yanmin,Duan, Meng,Houk,Bietti, Massimo
-
supporting information
p. 9925 - 9937
(2021/06/30)
-
- Selective C-C Bond Cleavage of Cycloalkanones by NaNO2/HCl
-
A novel selective fragmentation of cycloalkanones by NaNO2/HCl has been established. The C-C bond cleavage reaction proceeds smoothly under mild conditions, selectively affording versatile keto acids or oxime acids. The methodology can streamline the synthesis of valuable chiral molecules and isocoumarins from readily available feedstocks.
- He, Tianyu,Chen, Dengfeng,Qian, Shencheng,Zheng, Yu,Huang, Shenlin
-
supporting information
p. 6525 - 6529
(2021/09/02)
-
- Enantioselective Protonation of Enol Esters with Bifunctional Phosphonium/Thiourea Catalysts
-
Bifunctional phosphonium/thioureas derived from tert-leucine behaved as highly selective catalysts for enantioselective protonation of enol esters, providing α-chiral ketones in yields of up to 99% with high enantioselectivities (up to 98.5:1.5 er). Control experiments clarified that a bulky tert-butyl group and phosphonium and thiourea moieties were necessary to achieve such high stereoselectivity. In addition, mechanistic investigations indicated the catalyst was converted to the corresponding betaine species, which served as a monomolecular catalyst.
- Yamamoto, Eiji,Wakafuji, Kodai,Mori, Yusuke,Teshima, Gaku,Hidani, Yuki,Tokunaga, Makoto
-
supporting information
p. 4030 - 4034
(2019/06/07)
-
- Ductile Pd-Catalysed Hydrodearomatization of Phenol-Containing Bio-Oils Into Either Ketones or Alcohols using PMHS and H2O as Hydrogen Source
-
A series of phenolic bio-oil components were selectively hydrodearomatized by palladium on carbon into the corresponding ketones or alcohols in excellent yields using polymethylhydrosiloxane and water as reducing agent. The selectivity of the reaction was governed by the water concentration where selectivity to alcohol was favoured at higher water concentrations. As phenolic bio-oil examples cardanol and beech wood tar creosote were studied as substrate to the developed reaction conditions. Cardanol was hydrodearomatized into 3-pentadecylcyclohexanone in excellent yield. From beech wood tar creosote, a mixture of cyclohexanols was produced. No hydrodeoxygenation occurred, suggesting the applicability of the reported method for the production of ketone-alcohol oil from biomass. (Figure presented.).
- Di Francesco, Davide,Subbotina, Elena,Rautiainen, Sari,Samec, Joseph S. M.
-
supporting information
p. 3924 - 3929
(2018/09/14)
-
- Regioselective ketone α-alkylation with simple olefins via dual activation
-
Alkylation of carbonyl compounds is a commonly used carbon-carbon bond-forming reaction. However, the conventional enolate alkylation approach remains problematic due to lack of regioselectivity, risk of overalkylation, and the need for strongly basic conditions and expensive alkyl halide reagents. Here, we describe development of a ketone-alkylation strategy using simple olefins as the alkylating agents. This strategy employs a bifunctional catalyst comprising a secondary amine and a low-valent rhodium complex capable of activating ketones and olefins simultaneously. Both cyclic and acyclic ketones can be mono-a-alkylated with simple terminal olefins, such as ethylene, propylene, 1-hexene, and styrene, selectively at the less hindered site; a large number of functional groups are tolerated.The pH/redox neutral and byproduct-free nature of this dual-activation approach shows promise for large-scale syntheses.
- Mo, Fanyang,Dong, Guangbin
-
-
- Photocatalytic degradation of water taste and odour compounds in the presence of polyoxometalates and TiO2: Intermediates and degradation pathways
-
Geosmin (GSM) and 2-methylisoborneol (MIB) are produced by several species of cyanobacteria and actinomycetes. These compounds can taint water and fish causing undesirable taste and odours. Studies have shown that GSM/MIB are resistant in standard water treatments. Polyoxometalates (POM) are efficient photocatalysts in the degradation and mineralization of a great variety of organic pollutants, presenting similar behaviour with the widely published titanium dioxide (TiO2). Photocatalytic degradation of GSM and MIB under UV-A light in the presence of a characteristic POM photocatalyst, SiW 12O404-, in aqueous solution has been studied and compared with the photodegradation by TiO2 suspensions. GSM and MIB are effectively degraded in the presence of both photocatalysts. Addition of OH radical scavengers (KBr and tertiary butyl alcohol, TBA) retards the photodegradation rates of both compounds, suggesting that photodegradation mechanism takes place via OH radicals. Intermediates identified using GC-MS in the case of GSM and MIB, are mainly identical in the presence of both photocatalysts, also suggesting a common reaction mechanism. Possible photocatalytic degradation pathway for both GSM and MIB is proposed.
- Fotiou, Theodora,Triantis, Theodoros M.,Kaloudis, Triantafyllos,Papaconstantinou, Elias,Hiskia, Anastasia
-
-
- Selective activation of secondary C-H bonds by an iron catalyst: Insights into possibilities created by the use of a carboxyl-containing bipyridine ligand
-
In this work, we report the discovery of a carboxyl-containing iron catalyst 1 (FeII-DCBPY, DCBPY = 2,2′-bipyridine-4,4′- dicarboxylic acid), which could activate the C-H bonds of cycloalkanes with high secondary (2°) C-H bond selectivity. A turnover number (TN) of 11.8 and a 30% yield (based on the H2O2 oxidant) were achieved during the catalytic oxidation of cyclohexane by 1 under irradiation with visible light. For the transformation of cycloalkanes and bicyclic decalins with both 2° and tertiary (3°) C-H bonds, 1 always preferred to oxidise the 2° C-H bonds to the corresponding ketone and alcohol products; the 2°/3° ratio ranged between 78/22 and >99/1 across 7 examples. 18O isotope labelling experiments, ESR experiments, a PPh3 method and the catalase method were used to characterize the reaction process during the oxidation. The success of 1 showed that, in addition to using a bulky catalyst, high 2° C-H bond selectivity could also be achieved using a less bulky molecular iron complex as the catalyst.
- Cheng, Shi,Li, Jing,Yu, Xiaoxiao,Chen, Chuncheng,Ji, Hongwei,Ma, Wanhong,Zhao, Jincai
-
p. 3267 - 3273
(2013/10/01)
-
- Enantioselective oxidation by a cyclohexanone monooxygenase from the xenobiotic-degrading Polaromonas sp. strain JS666
-
A cyclohexanone monooxygenase (CHMO) from the xenobiotic-degrading Polaromonas sp. strain JS666 was heterologously expressed in Escherichia coli, and its ability to catalyze enantio- and regiodivergent oxidations of prochiral and racemic ketones was investigated. The expression system was also used to evaluate this enzyme's potential role in the oxidation of cis-1,2-dichloroethene (cDCE), a groundwater pollutant for which strain JS666 is the only known assimilator. The substrate enantiopreference and -selectivity of the strain JS666 CHMO is similar to that of other CHMO-type enzymes; of note is this enzyme's excellent stereodiscrimination of 2-substituted cyclic ketones. The expression system exhibits no activity with ethene or cDCE as substrates under the tested conditions. Phylogenetic analysis shows that sequence variability among cyclohexanone monooxygenases could be a rich source of new enzyme activities and attributes.
- Alexander, Anne K.,Biedermann, David,Fink, Michael J.,Mihovilovic, Marko D.,Mattes, Timothy E.
-
experimental part
p. 105 - 110
(2012/07/28)
-
- 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)
-
- Nucleophilic α-arylation and α-alkylation of ketones by polarity inversion of N-alkoxyenamines: Entry to the umpolung reaction at the α-carbon position of carbonyl compounds
-
A new aspect of enamine chemistry: The formation of N-alkoxyenamines from ketones has led to an efficient umpolung reaction. The alkylation of N-alkoxyenamines with trialkylaluminum compounds proceeded smoothly and gave α-alkylated ketones (see scheme). This reaction offers a simple transformation of ketones into α-substituted ketones without the need to isolate enamines and intermediary imines.
- Miyoshi, Tetsuya,Miyakawa, Takayuki,Ueda, Masafumi,Miyata, Okiko
-
supporting information; experimental part
p. 928 - 931
(2011/04/14)
-
- 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)
-
- Synthesis and preliminary biochemical evaluation of novel derivatives of PCP
-
(±)-Trans-Ph/Et and (±)-cis-Ph/Et 1-(2-ethyl-1- phenylcyclohexyl)piperidine were synthesized from 2-ethylcyclohexanone. In contrast to the corresponding trans-substituted 2-methyl compound which is 5x more potent than PCP, the trans-2-ethyl derivative has a 75x lower affinity for the PCP binding site. The cis-2-ethyl isomer is inactive like the cis-2-methyl derivative. (±)-1-(1-Phenylcyclohexyl)-2-methylpiperidine is almost as active as the parent PCP. Reduction of the aromatic ring or quaternization of the piperidine in PCP reduces the affinity for the PCP site.
- Linders, Joannes T. M.,Furlano, David C.,Mattson, Mariena V.,Jacobson, Arthur E.,Rice, Kenner C.
-
experimental part
p. 79 - 87
(2011/01/13)
-
- 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)
-
- Homogeneous pd-catalyzed enantioselective decarboxylative protonation
-
General homogeneous conditions for the palladium-catalyzed synthesis of carbonyl compounds with tertiary carbon stereocenters at the a-position are reported. The highly reactive catalyst tolerates a variety of substrate substitution and functionality, and generates enantioenriched cyclic ketones from racemic allyl ss-ketoester starting materials.
- Marinescu, Smaranda C.,Nishimata, Toyoki,Mohr, Justin T.,Stoltz, Brian M.
-
supporting information; experimental part
p. 1039 - 1042
(2009/04/06)
-
- Efficient and selective Al-catalyzed alcohol oxidation via oppenauer chemistry
-
A highly active and selective Al-based catalytic Oppenauer (O) oxidation is reported. Quantitative and selective oxidations of a variety of benzylic, propargylic, allylic, and aliphatic primary and secondary alcohols were achieved using nitrobenzaldehyde derivatives as the oxidant and simple aluminum compounds as precatalysts. Copyright
- Graves, Christopher R.,Zeng, Bi-Shun,Nguyen, SonBinh T.
-
p. 12596 - 12597
(2008/02/03)
-
- Asymmetric reduction of enones with Synechococcus sp. PCC 7942
-
Synechococcus sp. PCC 7942, a cyanobacterium, reduced both the endocyclic C-C double bond of s-trans enones and the exocyclic C-C double bond of s-cis enones with high enantioselectivity to afford the corresponding (S)-ketones under illumination.
- Shimoda, Kei,Kubota, Naoji,Hamada, Hiroki,Kaji, Misato,Hirata, Toshifumi
-
p. 1677 - 1679
(2007/10/03)
-
- Asymmetric transformation of enones with Synechococcus sp. PCC 7942
-
Asymmetric transformation of enones was investigated with cultured cells of Synechococcus sp. PCC 7942 (a cyanobacterium). The cells reduced both the endocyclic C-C double bond of s-trans enones and the exocyclic C-C double bond of s-cis enones with high enantioselectivity to afford optically active α-substituted (S)-ketones under illumination. In addition, the reduction of the double bond of these enones was accompanied by the formation of saturated alcohols. The cells preferentially reduced simple aliphatic ketones rather than cyclic ones to the corresponding (S)-alcohols with excellent enantioselectivity.
- Shimoda, Kei,Kubota, Naoji,Hamada, Hiroki,Yamane, Shin-Ya,Hirata, Toshifumi
-
p. 2269 - 2272
(2007/10/03)
-
- α-alkylation of ketones by addition of zinc enamides to unactivated olefins
-
A zinc enamide generated from the corresponding N-aryl imine undergoes addition to an unactivated olefin, such as ethylene, 1-octene, and isobutylene, to generate an α-alkylated γ-zincioimine intermediate in good to excellent yield. Terminal and gem-disubstituted olefins react with >99% regioselectivity, allowing the C-C bond formation to take place at the more hindered carbon of the double bond. The organozinc intermediate undergoes further C-C bond formation with a carbon electrophile to give, upon hydrolysis of the imine, an α-alkylated ketone bearing a variety of functionalized primary, secondary, and tertiary alkyl groups.
- Nakamura, Masaharu,Hatakeyama, Takuji,Nakamura, Eiichi
-
p. 11820 - 11825
(2007/10/03)
-
- Assessing the Substrate Selectivities and Enantioselectivities of Eight Novel Baeyer-Villiger Monooxygenases toward Alkyl-Substituted Cyclohexanones
-
Genes encoding eight Baeyer-Villiger monooxygenases have recently been cloned from bacteria inhabiting a wastewater treatment plant. We have carried out a systematic investigation in which each newly cloned enzyme, as well as the cyclohexanone monooxygenase from Acinetobacter sp. NCIB 9871, was used to oxidize 15 different alkyl-substituted cyclohexanones. The panel of substrates included equal numbers of 2-, 3-, and 4-alkyl-substituted compounds to probe each enzyme's stereoselectivity toward a homologous series of synthetically important compounds. For all 4-alkyl-substituted cyclohexanones tested, enzymes were discovered that afforded each of the corresponding (S)-lactones in ≥98% ee. This was also true for the 2-alkyl-substituted cyclohexanones examined. The situation was more complex for 3-akyl-substituted cyclohexanones. In a few cases, single Baeyer-Villiger monooxygenases possessed both high regio- and enantioselectivities toward these compounds. More commonly, however, they showed only one type of selectivity. Nonetheless, enzymes with such properties might be useful as parts of a two-step bioprocess where an initial kinetic resolution is followed by a regioselective oxidation on the isolated, optically pure ketone.
- Kyte, Brian G.,Rouviere, Pierre,Cheng, Qiong,Stewart, Jon D.
-
-
- Enantioselective synthesis of α-substituted ketones by asymmetric addition of chiral zinc enamides to 1-alkenes
-
A zinc enamide of a chiral imine derived from a ketone and (S)-valinol or (S)-t-leucinol undergoes addition to 1-alkene to generate a γ-zincioimine intermediate, which reacts with a carbon electrophile to give upon hydrolysis an optically active α-substituted ketone in good yield. The stereoselectivity of the addition reaction may reach 99% for the reaction of a cyclohexanone imine with ethylene. Copyright
- Nakamura, Masaharu,Hatakeyama, Takuji,Hara, Kenji,Nakamura, Eiichi
-
p. 6362 - 6363
(2007/10/03)
-
- (2-hydroxy)ethyl-thioureas useful as modulators of alpha2B adrenergic receptors
-
Compounds of formula (i) and of formula (ii) wherein the symbols have the meaning disclosed in the specification, specifically or selectively modulate α2B and/or α2C adrenergic receptors in preference over α2A adrenergic receptors, and as such are useful for alleviating chronic pain and allodynia and have no or only minimal cardivascular and/or sedatory activity.
- -
-
-
- Cu-catalyzed enantioselective conjugate addition of alkylzincs to cyclic nitroalkenes: Catalytic asymmetric synthesis of cyclic α-substituted ketones
-
An efficient and highly enantioselective (≥92% ee) catalytic method for conjugate addition of alkylzinc reagents to cyclic nitroalkenes is reported. Reactions are promoted in the presence of 0.5-5 mol % (CuOTf)2·C6H6 and 1
- Luchaco-Cullis, Courtney A.,Hoveyda, Amir H.
-
p. 8192 - 8193
(2007/10/03)
-
- Asymmetric hydrogenation of the C-C double bond of enones with the reductases from Nicotiana tabacum
-
Three enone reductases, p44, p74, and p90, from the cultured cells of Nicotiana tabacum catalyzed the asymmetric hydrogenation of the C-C double bond of enones. Reduction of 2-alkyl-2-cyclohexen-1-ones with the p44 reductase gave highly optically active (
- Hirata, Toshifumi,Shimoda, Kei,Gondai, Takayuki
-
p. 850 - 851
(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.
- -
-
-
- Substituted tetronic acids useful for treating HIV and other retroviruses
-
This invention comprises novel substituted tetronic acid type compounds, 2, 4(3H, 5H)-furandiones, that are useful for the inhibition of the HIV protease enzyme. The compounds may be useful for the treatment of a person with AIDS or AIDS related diseases. The compounds may be used in the attempt to retard the further replication of any retrovirus containing the aspartyl protease enzyme. Compounds are represented by the formula below. STR1
- -
-
-
- Recombinant baker's yeast as a whole-cell catalyst for asymmetric Baeyer - Villiger oxidations
-
Cyclohexanone monooxygenase (E.C. 1.14.13.22) from Acinetobacter sp. NCIB 9871 has been expressed in baker's yeast (Saccharomyces cerevisiae) to create a general reagent for asymmetric Baeyer - Villiger oxidations. This 'designer yeast' approach combines
- Stewart, Jon D.,Reed, Kieth W.,Martinez, Carlos A.,Zhu, Jun,Chen, Gang,Kayser, Margaret M.
-
p. 3541 - 3548
(2007/10/03)
-
- Amidino dervatives useful as nitric oxide synthase inhibitors
-
The current invention discloses useful pharmaceutical compositions containing azepine derivatives useful as nitric oxide synthase inhibitors.
- -
-
-
- MMPP (Magnesium Monoperoxyphthalate) in acetonitrile; a new approach to the synthesis of lactones via Baeyer-Villiger oxidation of cyclic ketones
-
A variety of unsubstituted and mono- or di-substituted cycloalkanones can be oxidised with modest excess of magnesium monoperoxyphthalate hexahydrate in acetonitrile to produce the corresponding lactones in facile, selective, and high yielding manner.
- Hirano, Masao,Yakabe, Shigetaka,Satoh, Akiko,Clark, James H.,Morimoto, Takashi
-
p. 4591 - 4596
(2007/10/03)
-
- Ring enlargement of α-ethylidenecycloalkanones to β-alkylidenecycloalkanones induced by trimethylstannyllithium/aldehyde equivalents/Lewis acids
-
α-Ethylidenecycloalkanones underwent a ring enlargement to β-alkylidenecycloalkanones upon a treatment with trimethylstannyllithium/aldehyde equivalents/Lewis acids with high stereoselectivity.
- Fujiwara,Tokuyasu,Sato
-
p. 289 - 296
(2007/10/02)
-
- Resolution of Racemic ε-Lactones
-
Kinetic resolution of racemic ε-lactones by Pig Liver Esterase give optically active R (+) ε-lactones.When alkyl group is higher than propyl, Horse Liver Esterase leads to the destruction of the opposite enantiomer.Enantiomeric excess is easily evaluated by G.C. on a chiral stationary phase.
- Fellous, R.,Lizzani-Cuvelier, L.,Loiseau, M. A.,Sassy, E.
-
p. 343 - 346
(2007/10/02)
-
- Reactivity of 2-Substituted Cyclohex-1-enylacetic Acids with Diazodiphenylmethane in Various Alcohols
-
The reactivities of 2-substituted cyclohex-1-enylacetic acids with diazodiphenylmethane in eleven alcohols has been investigated.The solvent effect is interpreted in terms of the influence of the relative permittivity on the rate constants.The multiple linear correlation of log k with the Kirkwood function of relative permittivity.Taft ?* value for the alkyl group of the alcohol and the number of γ-hydrogen atoms in the alcohol nγH was highly successful (R=0.9927).The log k values for the various acids were correlated by using the appropriate form of the extended Hammett equation involving inductive, resonance and steric parameters.The reaction of cyclohex-1-enylacetic acid with diazodiphenylmethane in eleven alcohols shows a good linear free energy relationship with the corresponding reaction of phenylacetic acid (R=0.9793).The results obtained for 2-substituted cyclohex-1-enylacetic acids were compared with the results for ortho-substituted phenylacetic acids under the same experimental conditions.
- Uscumlic, Gordana S.,Muskatirovic, Milan D.
-
p. 1799 - 1802
(2007/10/02)
-
- Efficient Cleavage of Cyclopropyl Bond by Adjacent Ketyl Radical Generated Under PET Conditions
-
Photolysis of various conjugated cyclopropyl and epoxy ketones in 20percent triethyl amine (TEA) and ethanol leads to cleavage of cyclopropyl bond.Significant wavelength dependence phenomenon is observed during photolysis for the cleanliness and efficient photo transformation.Steroidal cyclopropyl ketones cleave efficiently at 300nm photolysis, whereas exo-cyclopropyl ketones cleave at 254nm.The regiochemistry of cyclopropyl bond cleavage is governed by the principle of maximum overlap.The nature of chemistry generated by ketyl radical is shown to be a function of methodology of their generation.
- Pandey, Bipin,Rao, Ashok T.,Dalvi, Pramod V.,Kumar, Pradeep
-
p. 3843 - 3848
(2007/10/02)
-
- The Reactivity of 2-Substituted Cyclohex-1-enecarboxylic Acid With Diazodiphenylmethane in Various Alcohols
-
The reactivities of 2-substituted cyclohex-1-enecarboxylic acids with diazodiphenylmethane in several alcohols were investigated.The rate data for these acids were correlated with a simple Hammett equation by means of the ?p constants.The transmission of polar effects through the double bond, in terms of polar susceptibility constant ρ, has been discussed.For the reactions of a given acid in the various alcohols, the log k and ρ values were correlated through multiple regression on appropriate solvent parameters.The results obtained for 2-substituted cyclohex-1-enecarboxylic acids were compared with the results for ortho-substituted benzoic acids under the same experimental conditions.
- Uscumlic, Gordana S.,Krstic, Vera V.,Muskatirovic, Milan D.
-
p. 999 - 1002
(2007/10/02)
-
- Synthesis of 2-Alkylcyclohexanones Using Solvent-free Conditions and Microwave Technology
-
An expeditious solvent-free route to 2-alkylcyclohexanones from 2-ethoxycarbonylcyclohexanone is described via a solid-liquid phase transfer catalysed alkylation using ButOK as base and Aliquat 336 as catalyst and a LiBr-H2O-NBu4Br induced dealkoxycarbonylation under microwave activation in a focused open-vessel Maxidigest system.Yields were >/= 75percent over two steps.
- Barnier, Jean Pierre,Loupy, Andre,Pigeon, Philippe,Ramdani, Mohamed,Jacquault, Patrick
-
p. 397 - 398
(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)
-
- Oxidation of Secondary Alcohols over Hydrous Zirconium(IV) Oxide
-
The oxidation of secondary alcohols with ketones was carried out by catalysis with hydrous zirconium(IV) oxide.In the batch reaction system, the oxidation proceeded efficiently to give the corresponding ketones, except for some secondary alcohols.On the other hand, all of the secondary alcohols were efficiently converted to the corresponding ketones in the flow oxidation system.The influence of the hydrogen acceptor on the oxidation rate was investigated by the use of several ketones, and the oxidation rate was influenced by the electron density and steric hindrance around the carbonyl group.The dependence on the reaction temperature was also investigated in the flow reaction system.
- Kuno, Hideyuki,Takahashi, Kyoko,Shibagaki, Makoto,Shimazaki, Kazuko,Matsushita, Hajime
-
p. 1943 - 1946
(2007/10/02)
-
- Charge-reversal Mass Spectra of Enolate Ions of Some Open-chain and Cyclic Ketones for Structure Identification
-
The charge-reversal (CR) mass spectra of the enolate ions of heptanal and ten isomeric heptanones, of cyclohexanone, of cycloheptanone, of isomeric methylcyclohexanones, of isomeric ethylcyclohexanones and of the isomeric monoterpene ketones camphor, fenchone, pulegone and thujone were obtained by deprotonating using OH(-) under chemical ionization conditions followed by collision of the (-) ions with helium in the second field-free region of a VG ZAB 2F mass spectrometer.The CR mass spectra were evaluated by similarity index (SI) values.Characteristic of the CR mass spectra of the open-chain enolates are fragment ions formed by α- cleavage.However, the CR mass spectra are dominated by peaks of small hydrocarbon ions, particularly in the case of cyclic and bicyclic enolates.The CR mass spectra of enolates of linear heptanones differing in the position of the carbonyl group can be easily correlated with the structure of the parent ketone.The CR mass spectra of enolates of isomeric heptan-2-ones differing only in the degree of branching of the alkyl group are similar, but can be distinguished by the SI values.The CR mass spectra of the enolates of the isomeric cyclic and bicyclic ketones studied are more or less identical and cannot be used for structural assignment.
- Suerig, Thomas,Gruetzmacher, Hans-Friedrich
-
p. 446 - 452
(2007/10/02)
-
- Preparation and Chiroptical Properties of Optically Active Vinyl Ether-Iron and Olefin-Iron Complexes. A CD Quadrant Rule Correlating Absolute Configurations.
-
Exchange etherification of dicarbonylcyclopentadienyl(η2-ethyl vinyl ether)iron tetrafluoroborate (4) with optically active primary and secondary alcohols yields a mixture of diastereomeric cations.These isomers are in rapid equilibrium at room
- Begum, M. Kohinoor,Chu, Kai-Hsuan,Coolbaugh, Thomas S.,Rosenblum, Myron,Zhu, Xiao-Ya
-
p. 5252 - 5259
(2007/10/02)
-
- Efficient Conjugate Alkylation of α,β-Unsaturated Nitro Olefins by Triorganoalanes
-
Both trialkylaluminum (AlR3; R = Et, i-Bu) and triorganoaluminum etherates (AlR3*OEt2; R = Et, i-Bu, Ph) rapidly react with α,β-unsaturated nitro olefins to give only 1,4-monoalkylated products in high yields.The natures of substrates, the reaction conditions as well as the reagents molar ratio, do not cause significant variations on the recovered products.
- Pecunioso, Angelo,Menicagli, Rita
-
-
- α-ALKYLATION AND α-ALKYLIDENATION OF CARBONYL COMPOUNDS BY O-SILYLATED ENOLATE PHENYLTHIOALKYLATION
-
For many reactions next to a carbonyl group, the use of O-silylated enolate chemistry offers improvements in yield and selectivity over the corresponding reactions of Group I metal enolates.In the case of α-alkylation of carbonyl compounds, Lewis acid (TiCl4 or ZnBr2) promoted phenylthioalkylation of O-silylated enolates 3 by α-chlorosulphides 4 (R3=H, Me, Prn, Pri, Bui, and Me3Si), followed by reductive sulphur removal by Raney nickel, 5->6, is found to be a reliable method for this synthetically important C-C bond forming step.An alternative sulphur elimination pathway via the sulphoxide, 5->7, allows the regio- and stereocontrolled α-alkylidenation of carbonyl compounds.The phenylthioalkylation reaction is applicable to ketones, aldehydes, esters, and lactones.
- Paterson, Ian
-
p. 4207 - 4220
(2007/10/02)
-
- Process for preparing substituted 2,3,4,9-tetrahydro-1H-carbazole-1-acetic acid
-
Substituted 2,3,4,9-tetrahydro-1H-carbazole-1-acetic acid derivatives and methods for their preparation and use are disclosed. The compounds are useful analgesic and antiinflammatory agents.
- -
-
-
- Substituted 2,3,4,9-tetrahydro-1H-carbazole-1-acetic acid
-
Substituted 2,3,4,9-tetrahydro-1H-carbazole-1-acetic acid derivatives and methods for their preparation and use are disclosed. The compounds are useful analgesic and antiinflammatory agents.
- -
-
-