- Equilibration of Alkene Regioisomers in trans- and cis-Octalins
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As models for studying the energetics of double-bond regiochemistry in the octalin system, the enol acetates of trans- and cis-2-decalone (1,4), trans- and cis-10-methyl-2-decalone (7,10) and trans- and cis-9-methyl-2-decalone (13,16) have been synthesized.Acid-catalyzed equilibrations of double-bond position were conducted in acetic anhydride at ca. 60, 100 and 140 deg C and assessed by integration of the vinyl-proton NMR signals, which were unambiguously assigned to each enol acetate either by the observed splitting pattern or synthesis.Values of ΔH and ΔS (Δ2:Δ1) are derived and compared with experimental and theoretical literature values.Values of ΔH for the enol acetates of 1 and 4 are -0.69 and 0.0 kcal mol-1, respectively, and addition of an angular methyl decreases the relative stability (ΔH) of the Δ1 isomer, by 1.25 - 2.25 kcal mol-1 for the trans skeleton and by 1.0 - 1.4 kcal mol-1 for the cis skeleton.For a given angular substituent, changing cis stereochemistry to trans also decreases the relative Δ1-stability, by 0.7 kcal mol-1 when R = H and 0.95 - 1.55 kcal mol-1 when R = Me.Values of ΔS are all small, between +0.1 and -3.2 cal mol-1 K-1.Trends in the data and features of the 1H NMR spectra related to conformation are discussed, and an approach is suggested for calculating approximate ΔH, ΔS and ΔG values for Δ1-9-methyl- vs. Δ1-10-methyloctalin in the trans and cis series.
- Thompson, Hugh W.,Gaglani, Kamlesh D.
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Read Online
- High trans-2-Decalones by Photoredox Catalyzed β-Isomerization
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The synergistic combination of three catalytic processes – photoredox, enamine and hydrogen atom transfer (HAT) catalysis – enabled the β-isomerization of 2-decalones towards the thermodynamically most stable trans-isomers. A library of iridium (III) complexes and organic dyes were screened in combination with cyclic amines and thiols which after optimization gave the desired trans-2-decalones with high trans/cis ratios of 60 : 40 up to 98 : 2.
- Barnes, Quentin,Biremond, Tony,Quintaine, Julie,Saudan, Lionel,Sombret, Juliette,de Saint-Laumer, Jean-Yves
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- Ozonation of decalin as a model saturated cyclic molecule: A spectroscopic study
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Ozonolysis is used for oxidation of a model cyclic molecule-decalin, which may be consid-ered as an analog of saturated cyclic molecules present in heavy oil. The conversion of decalin exceeds 50% with the highest yield of formation of acids about 15–17%. Carboxylic acids, ketones/aldehydes, and alcohols are produced as intermediate products. The methods of UV-visible, transmission IR, at-tenuated total reflection IR-spectroscopy, NMR and mass-spectrometry were used to identify reaction products and unravel a possible reaction mechanism. The key stage of the process is undoubtedly the activation of the first C-H bond and the formation of peroxide radicals.
- Bykov, Gennadii L.,Ershov, Boris G.,Krasovskiy, Vladimir G.,Kustov, Alexander L.,Kustov, Leonid M.,Panich, Nadezhda M.
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- Enhancing Chemo- And Stereoselectivity in C-H Bond Oxygenation with H2O2by Nonheme High-Spin Iron Catalysts- And Role of Lewis Acid and Multimetal Centers
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Spin states of iron often direct the selectivity in oxidation catalysis by iron complexes using hydrogen peroxide (H2O2) on an oxidant. While low-spin iron(III) hydroperoxides display stereoselective C-H bond hydroxylation, the reactions are nonstereoselective with high-spin iron(II) catalysts. The catalytic studies with a series of high-spin iron(II) complexes of N4 ligands with H2O2 and Sc3+ reported here reveal that the Lewis acid promotes catalytic C-H bond hydroxylation with high chemo- and stereoselectivity. This reactivity pattern is observed with iron(II) complexes containing two cis-labile sites. The enhanced selectivity for C-H bond hydroxylation catalyzed by the high-spin iron(II) complexes in the presence of Sc3+ parallels that of the low-spin iron catalysts. Furthermore, the introduction of multimetal centers enhances the activity and selectivity of the iron catalyst. The study provides insights into the development of peroxide-dependent bioinspired catalysts for the selective oxygenation of C-H bonds without the restriction of using iron complexes of strong-field ligands.
- Das, Abhishek,Jana, Rahul Dev,Paine, Tapan Kanti
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p. 5969 - 5979
(2021/05/04)
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- ISOMERISATION REACTION
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The present invention relates to the field of organic synthesis and more specifically to the isomerization of the β position of a β?trisubstituted C3-C70 carbonyl compound.
- -
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Paragraph 16
(2020/10/09)
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- The debut of chiral cyclic (alkyl)(amino)carbenes (CAACs) in enantioselective catalysis
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The popularity of NHCs in transition metal catalysis has prompted the development of chiral versions as electron-rich neutral stereodirecting ancillary ligands for enantioselective transformations. Herein we demonstrate that cyclic (alkyl)(amino)carbene (CAAC) ligands can also engage in asymmetric transformations, thereby expanding the toolbox of available chiral carbenes.
- Pichon, Delphine,Soleilhavoup, Michele,Morvan, Jennifer,Junor, Glen P.,Vives, Thomas,Crévisy, Christophe,Lavallo, Vincent,Campagne, Jean-Marc,Mauduit, Marc,Jazzar, Rodolphe,Bertrand, Guy
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p. 7807 - 7811
(2019/08/30)
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- Iron Complex Catalyzed Selective C-H Bond Oxidation with Broad Substrate Scope
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The use of a peroxidase-mimicking Fe complex has been reported on the basis of the biuret-modified TAML macrocyclic ligand framework (Fe-bTAML) as a catalyst to perform selective oxidation of unactivated 3° C-H bonds and activated 2° C-H bonds with low catalyst loading (1 mol %) and high product yield (excellent mass balance) under near-neutral conditions and broad substrate scope (18 substrates which includes arenes, heteroaromatics, and polar functional groups). Aliphatic C-H oxidation of 3° and 2° sites of complex substrates was achieved with predictable selectivity using steric, electronic, and stereoelectronic rules that govern site selectivity, which included oxidation of (+)-artemisinin to (+)-10β-hydroxyartemisinin. Mechanistic studies indicate FeV(O) to be the active oxidant during these reactions.
- Jana, Sandipan,Ghosh, Munmun,Ambule, Mayur,Sen Gupta, Sayam
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supporting information
p. 746 - 749
(2017/03/01)
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- Alkane oxidation catalysed by a self-folded multi-iron complex
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A preorganised ligand scaffold is capable of coordinating multiple Fe(II) centres to form an electrophilic CH oxidation catalyst. This catalyst oxidises unactivated hydrocarbons including simple, linear alkanes under mild conditions in good yields with selectivity for the oxidation of secondary CH bonds. Control complexes containing a single metal centre are incapable of oxidising unstrained linear hydrocarbons, indicating that participation of multiple centres aids the CH oxidation of challenging substrates.
- Mettry, Magi,Moehlig, Melissa Padilla,Gill, Adam D.,Hooley, Richard J.
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p. 120 - 128
(2016/11/09)
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- From DNA to catalysis: A thymine-acetate ligated non-heme iron(III) catalyst for oxidative activation of aliphatic C-H bonds
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A non-heme, iron(iii)/THA(thymine-1-acetate) catalyst together with H2O2 as an oxidant is efficient in oxidative C-H activation of alkanes. Although having a higher preference for tertiary C-H bonds, the catalyst also oxidizes aliphatic secondary C-H bonds into carbonyl compounds with good to excellent conversions. Based on the site selectivity of the catalyst and our mechanistic studies the reaction proceeds via an Fe-oxo species without long lived carbon centered radicals.
- Al-Hunaiti, Afnan,R?is?nen, Minn?,Repo, Timo
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p. 2043 - 2046
(2016/02/05)
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- Highly Selective Hydrogenation of Aromatic Ketones and Phenols Enabled by Cyclic (Amino)(alkyl)carbene Rhodium Complexes
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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
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supporting information
p. 9250 - 9253
(2015/08/11)
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- ALPHA-HYDROGEN SUBSTITUTED NITROXYLS AND DERIVATIVES THEREOF AS CATALYSTS
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The present invention relates to novel alpha-hydrogen substituted nitroxyl compounds and their corresponding oxidized (oxoammonium cations) and reduced (hydroxylamine) forms, and to the use of such compounds, inter alia, for (1) oxidation of primary and secondary alcohols to aldehydes and ketones, respectively; (2) resolution of racemic alcohols; (3) desymmetrization of meso-alcohol; (4) as radicals and spin trapping reagents; and (5) as polymerization agents. The present invention further relates to processes for preparing the novel nitroxyl/oxoammonium/ hydroxylamine compounds from the corresponding amines, and to certain novel amine derivatives and their uses. The compounds of the invention as well as the amine precursors are also useful as ligands for transition metals and as organocatalysts in e.g., aldol reactions.
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Page/Page column 37
(2013/08/28)
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- Selective activation of secondary C-H bonds by an iron catalyst: Insights into possibilities created by the use of a carboxyl-containing bipyridine ligand
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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
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p. 3267 - 3273
(2013/10/01)
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- An iron catalyst for oxidation of alkyl C-H bonds showing enhanced selectivity for methylenic sites
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Many are called but few are chosen: A nonheme iron complex catalyzes the oxidation of alkyl C-H bonds by using H2O2 as the oxidant, showing an enhanced selectivity for secondary over tertiary C-H bonds (see scheme). Copyright
- Prat, Irene,Gomez, Laura,Canta, Merce,Ribas, Xavi,Costas, Miquel
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supporting information
p. 1908 - 1913
(2013/03/14)
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- Nanoshell carbon-supported cobalt catalyst for the aerobic oxidation of alcohols in the presence of benzaldehyde: An efficient, solvent free protocol
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A versatile, solvent free aerobic alcohol oxidation system has been established in the presence of benzaldehyde based on a heterogenous cobalt catalyst supported on nanoshell carbon (Co/NSC), which was prepared through the pyrolysis of a mixture of Co(II) phthalocyanine and phenol resin. The established system features equal efficiency toward both benzylic alcohols and aliphatic alcohols. The nanoshell carbon has been demonstrated to be a better supporting material for the present reaction than some other carbon materials, e.g., activated carbon. Mechanistic studies suggest that Co/NSC can catalyze the formation of oxidative intermediate peroxybenzoic acid as efficiently as homogeneous cobalt catalyst, and moreover, suppress the undesired Baeyer-Villiger side reaction. Co/NSC also exhibits good reusability, i.e., it can be reused for at least 10 times without significant loss of performance. Crown Copyright
- Kuang, Yongbo,Nabae, Yuta,Hayakawa, Teruaki,Kakimoto, Masa-Aki
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scheme or table
p. 52 - 58
(2012/06/01)
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- Construction of a quaternary carbon at the carbonyl carbon of the cyclohexane ring
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High SN2′ selectivity in the allylic substitution of cyclohexylidene ethyl picolinates with copper reagents prepared from RMgBr and CuBr·Me2S was realized by addition of ZnX2 (X = I, Br, Cl). Furthermore, ZnX2 accelerated the reaction with the bulky iPr reagent. The Royal Society of Chemistry 2010.
- Kaneko, Yuki,Kiyotsuka, Yohei,Acharya, Hukum P.,Kobayashi, Yuichi
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supporting information; experimental part
p. 5482 - 5484
(2010/10/04)
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- Efficient stereo- and regioselective hydroxylation of alkanes catalysed by a bulky polyoxometalate
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Direct functionalization of alkanes by oxidation of C-H bonds to form alcohols under mild conditions is a challenge for synthetic chemistry. Most alkanes contain a large number of C-H bonds that present difficulties for selectivity, and the oxidants employed often result in overoxidation. Here we describe a divanadium-substituted phosphotungstate that catalyses the stereo- and regioselective hydroxylation of alkanes with hydrogen peroxide as the sole oxidant. Both cyclic and acyclic alkanes were oxidized to form alcohols with greater than 96% selectivity. The bulky polyoxometalate framework of the catalyst results in an unusual selectivity that can lead to the oxidation of secondary rather than the weaker tertiary C-H bonds. The catalyst also avoids wasteful decomposition of the stoichiometric oxidant, which can result in the production of hydroxyl radicals and lead to non-selective oxidation and overoxidation of the desired products.
- Kamata, Keigo,Yonehara, Kazuhiro,Nakagawa, Yoshinao,Uehara, Kazuhiro,Mizuno, Noritaka
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scheme or table
p. 478 - 483
(2010/09/17)
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- A new regeneration system for oxidized nicotinamide cofactors
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A novel regeneration system for oxidized nicotinamide cofactors (NAD + and NADP+) is presented. By combining 2,2′-azino-bis(3-ethylbenzthiazoline-6-sulphonic acid (ABTS)-catalyzed oxidation of NAD(P)H with laccase-catalyzed utilization of molecular oxygen as terminal oxidant, a simple chemo-enzymatic NAD(P)+ regeneration method is achieved. Thus, the advantages of both worlds, chemical oxidation of reduced nicotinamide cofactors and laccase-catalyzed utilization of oxygen from air are combined in a simple and generally applicable new approach for biooxidation catalysis. This new application of the well-known laccase-mediator system (LMS) is successfully used to promote alcohol dehydrogenase-catalyzed oxidation reactions of primary and secondary alcohols. Already under non-optimized conditions, high turnover numbers of > 300 and > 16000 were obtained for the nicotinamide cofactor and ABTS, respectively. In this communication, we present the proofof-principle and initial characterization of the proposed new regeneration system.
- Aksu, Seda,Arends, Isabel W.C.E.,Hollmann, Frank
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supporting information; experimental part
p. 1211 - 1216
(2010/03/01)
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- Improved dienophilicity of nitrocycloalkenes: Prospects for the development of a trans-Diels-Alder paradigm
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(Chemical Equation Presented) The development of an efficient and stereoselective trans-Diels-Alder paradigm is described. A central element of this transformation is the introduction of a temporary dienophilic functionality (A), which serves both to acti
- Woo, Han Kim,Jun, Hee Lee,Danishefsky, Samuel J.
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supporting information; experimental part
p. 12576 - 12578
(2010/01/30)
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- Equatorial preference in the C-H activation of cycloalkanes: GaCl 3-catalyzed aromatic alkylation reaction
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GaCl3 catalyzes the aromatic alkylation of naphthalene or phenanthrene using cycloalkanes. The C-C bond formation predominantly takes place at the least hindered positions of the substrates, and equatorial isomers regarding the cycloalkane moiety are generally obtained. The reaction of bicyclo[4.4.0]decane and naphthalene occurs at the 2-position of naphthalene and at the 2- or 3-carbons of the cycloalkane, and the products possess a trans configuration at the junctures and an equatorial configuration at the naphthyl groups. Notably, cis-bicyclo[4.4.0]decane turns out to be much more reactive than the trans isomer, and a turnover number "TON" up to 20 based on GaCl3 is attained. 1,2-Dimethylcyclohexane reacts similarly, and the cis isomer is more reactive than the trans isomer. Monoalkylcycloalkanes react at the secondary carbons provided that the alkyl group is smaller than tert-butyl. Adamantanes react at the tertiary 1-position. The alkylation reaction is considered to involve the C-H activation of cycloalkanes with GaCl3 at the tertiary center followed by the migration of carbocations and electrophilic aromatic substitution yielding thermodynamically stable products. The stereochemistry of the reaction reveals that GaCl 3 activates the equatorial tertiary C-H bond rather than the axial tertiary C-H bond.
- Yonehara, Fumi,Kido, Yoshiyuki,Sugimoto, Hiraku,Morita, Satoshi,Yamaguchi, Masahiko
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p. 6752 - 6759
(2007/10/03)
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- Allyl sulfoxides as precursors for radical two-carbon ring expansion of cyclobutanones
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The two-carbon ring expansion of cycloalkanones is now possible in a two-step procedure. This procedure is based on an unusual cascade reaction that consists of a [2,3]-sigmatropic rearrangement (Mislow-Braverman-Evans rearrangement) of an allylic sulfoxide followed by a radical fragmentation-cyclization process (see scheme; AIBN = azobisisobutyronitrile).
- Chuard, Rachel,Giraud, Anne,Renaud, Philippe
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p. 4323 - 4325
(2007/10/03)
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- The selective functionalization of saturated hydrocarbons. Part 46. An investigation of Udenfriend's system under Gif conditions
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Under Gif conditions using ascorbic acid as reductant and oxygen as oxidant in pyridine, the selectivity for secondary hydrogen functionalization is exceptional. EDTA (ethylenediamine-tetra-acetic acid) is not needed as a ligand for iron.
- Barton, Derek H.R.,Delanghe, Nathalie C.
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p. 4471 - 4476
(2007/10/03)
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- Oxidation with the "O2 - H2O2 - Vauauium complex - Pyrazine-2-carboxylic acid" reagent 9. Oxidation of cyclohexene and decalin
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The oxidation of cyclohexene with hydrogen peroxide catalyzed by a vanadium complex and pyrazine-2-carboxylic acid (PCA) in air results in the formation of cyclohex-2-enyl hydroperoxide as the main product and cyclohex-2-enol, cyclohex-2-enone, cyclohex-3-enyl hydroperoxide, cyclohex-3-enol, cyclohexanol, cyclohexane, and 1,2-epoxycyclohexane in lesser amounts. The composition of the products of oxidation of decalin isomers with the system in question is similar to those obtained in the photochemical oxidation with hydrogen peroxide in air and in the oxidation with air in the presence of anthraquinone. A proposed mechanism for the oxidation includes the initiation by hydroxyl radicals generated from hydrogen peroxide under the action of the V - PCA system.
- Schuchardt,Guerreiro,Shul'pin
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p. 247 - 252
(2007/11/27)
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- Zeolite H-ZSM 5 Catalysed Oxidation of Alcohols with Chromium Trioxide. Part 9. General Synthetic Methods
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A variety of alcohols are oxidised to the corresponding carbonyl compounds in excellent yields by chromium trioxide-H-ZSM 5 in dichloromethane at room temperature.
- Pitre, Sangeeta V.,Venkat Ram Reddy,Vankar, Yashwant D.
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p. 462 - 463
(2007/10/03)
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- New synthesis of (±)2,3-dimethoxyhexahydroberbine
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The total synthesis of (±)2,3-dimethoxyhexahydroberbine 7 key compound transhexahydroisochroman-3-one 5 has been reported.
- Chatterjee, Asima,Sahu, Arabinda,Saha, Munmun,Banerji, Julie
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p. 121 - 122
(2007/10/03)
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- Palladium Assisted Transfer Hydrogenation of Cyclic α,β-Unsaturated Ketones by Ammonium Formate
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α,β-Unsaturated ketones can be hydrogenated conveniently under catalytic hydrogenation conditions using ammonium formate / Pd-C (10percent) in refluxing methanol.
- Rao, H. Surya Prakash,Reddy, K. Subba
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p. 171 - 174
(2007/10/02)
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- Use of excited-state and ground-state redox properties of polyoxometalates for selective transformation of unactivated carbon-hydrogen centers remote from the functional group in ketones
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Two types of processes are described which involve the selective transformation of unactivated carbon-hydrogen bonds in a ketone, cis-2-decalone, cis-1, which possesses conventionally far more reactive bonds. The first type of process involves irradiation of decatungstate, W10O324- in the presence of cis-1 producing, trans-2-decalone, trans-1, the product resulting from epimerization of an unactivated tertiary C-H bond remote from the carbonyl group, in high selectivity at high conversion of substrate, eq 1. The second type of reaction involves irradiation of the heteropolytungstate, α-P2W18O626- or α-PW12O403-, in the presence of cis-1 producing two monounsaturated ketones (octalones) in high selectivity with the nonthermodynamic isomer, 2, in comparable or greater quantity than the conventional thermodynamic (conjugated) isomer, 3, eq 2. Both types of processes are independent of wavelength over the principal range of absorption of the complexes (250-380 nm). The reactions are first order in W10O324- under optically dilute conditions. The primary kinetic isotope of the corresponding decalin hydrocarbons evaluated under the same reaction conditions as eq 1, kcis-decalin-H18/kcis-decalin-D18 ～ 2, and the solvent kinetic isotope effect, kCH3CN/kCD3CN = 1.0. The photochemical reaction of decatungstate with α,α,α′,α′-D4-cis-1 leads exclusively, even at moderate conversion of substrate (25%), to α,α,α′,α′-D4-trans-1. These data, an isotope crossover experiment in which decatungstate was irradiated in the presence of a 50/50 molar mixture of deuterated and protiated cis-decalin in CD3CN, reactions of cis-1 and cis-decalin with an authentic localized ground-state radical, t-BuO?, and a number of other experiments are consistent with initial H atom abstraction in all cases. The dramatically different products seen with the different polyoxometalate systems are dictated by the relative rates of epimerization, oxidation, and escape of the cisoid tertiary bridgehead radicals in the initial radical cage and, to a lesser extent, by the rates of conventional radical-radical reactions and other processes.
- Combs-Walker, Lucille A.,Hill, Craig L.
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p. 938 - 946
(2007/10/02)
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- Catalytic Alkane Activations in Reverse Microemulsions Containing Iron Salts and Hydrogen Peroxide
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A microemulsion system generated from two reverse microemulsions containing respectively an aqueous solution of iron salts and 30percent H2O2 dispersed in liquid alkanes catalyses the oxidation of C-H bonds.
- Briffaud, T.,Larpent, C.,Patin, H.
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p. 1193 - 1194
(2007/10/02)
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- Oxidations by Methyl(trifluoromethyl)dioxirane. 2. Oxyfunctionalization of Saturated Hydrocarbons
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The reaction of methyl(trifluoromethyl)dioxirane (1b), a novel dioxirane species, with two open-chain, four cyclic, and five polycyclic saturated hydrocarbons and two aralkyl hydrocarbons in CH2Cl2/1,1,1-trifluoropropanone has been studied; under mild conditions (-22 to 0 deg C), it gives alcohols and/or ketones (deriving from further oxidation of secondary alcohols) in high yields and within very short reaction times.Primary C-H bonds are not appreciably oxidized and high regioselectivities were determined for attack at tertiary over secondary C-H bonds, with theexception of norbornane, which showed opposite regioselectivity.The reaction is also highly stereoselective, since hydroxylations of cis- and trans-decalin and of cis- and trans-1,2-dimethylcyclohexane were found to be in each case stereospecific with retention.From kinetic data, Ea = 14.3 kcal mol-1 and log A = 9.9 were estimated for cyclohexane oxidation.Relative rates change in the order cyclohexane (0.78) octane (9.2) adamantane (146); cis-1,2-dimethylcyclohexane was observed to be 7-fold more reactive than its trans isomer, demonstrating remarkable discrimination for equatorial vs axial C-H attack (also noticed in the case of cis- and trans-decalin).The relative rate of oxidation of cumene vs ethylbenzene was found to be ca. 3.1 (after statistical correction), i.e., in sharp excess over values usually recorded in classical radical H-atom abstraction from benzylic position.Rate constants determined for the reactions of cumene and of ethylbenzene show the title dioxirane (1b) is more reactive than dimethyldioxirane (1a) by factors of ca. 600 and over 700, respectively.The whole of theobservations is better accommodated by an "oxenoid" mechanism, involving concerted O-atom insertion by dioxirane into C-H bonds of hydrocarbons.
- Mello, Rossella,Fiorentino, Michele,Fusco, Caterina,Curci, Ruggero
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p. 6749 - 6757
(2007/10/02)
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- A CONVENIENT PROCEDURE FOR DISSOLVING METAL REDUCTIONS
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Alicyclic α,β-unsaturated ketones react with lithium in ethylenediamine, followed by Jones oxidation, to give cyclic ketones in good yield.The stereoselectivity at the β position parallels that observed with lithium in liquid ammonia.
- Markgraf, J. Hodge,Staley, Stuart Waugh,Allen, Timothy R.
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p. 1471 - 1478
(2007/10/02)
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- FUNCTIONALISATION OF SATURATED HYDROCARBONS. Part X. A COMPARATIVE STUDY OF CHEMICAL AND ELECTROCHEMICAL PROCESSES (GIF AND GIF-ORSAY SYSTEMS) IN PYRIDINE, IN ACETONE AND IN PYRIDINE-CO-SOLVENT MIXTURES
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Six saturated hydrocarbons (cyclohexane, 3-ethylpentane, methylcyclopentane, cis- and trans-decalin and adamantane) were oxidised by the Gif system (iron catalyst, oxygen, zinc, carboxylic acid) and its electrochemical equivalent (Gif-Orsay system).Results obtained using various solvents (pyridine, acetone, pyridine-acetone mixtures) were similar for both systems.Total or partial replacement of pyridine with acetone affects the selectivity for secondary positions and lowers the ketone/secondary alcohol ratio.The formation of the same ratio of cis- and trans-decal-9-ol from both cis- and trans-decalin clearly demonstrates that tertiary alcohols result from a mechanism essentially radical in nature.
- Belavoine, Gilbert,Barton, Derek H. R.,Boivin, Jean,Gref, Aurore,Coupanec, Pascale Le,et al.
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p. 1091 - 1106
(2007/10/02)
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- Anaerobic Functionalization of Remote Unactivated Carbon-Hydrogen Bonds by Polyoxometalates
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The excited states of a representative heteropolytungstate, α-PW12O40(3-), and a representative isopolytungstate, W10O32(4-), accessible with near UV or blue light, oxidize alkanes and conventionally far more reactive organic molecules including alcohols, alkenes, N-alkylacetamides, and ketones, at comparable rates.One or more of the latter three types of compounds are produced upon irradiation of acetonitrile solutions containing the polyoxotungstate and alkane substrate under anaerobic conditions.Comparison of alcohol versus alkane reactivities under absolute and competitive kinetic conditions indicates that alcohol-polyoxotungstate preassociation can be important in these processes.Reaction of cis- and trans-decalones in these systems indicates that functionalization of unactivated positions (primarily incorporation of the olefinic unit) remote from the usually activating ketone group can be accomplished.
- Hill, Craig L.,Renneke, Roman F.,Combs, Lucille
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p. 7499 - 7508
(2007/10/02)
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- Enzymes in organic synthesis. 37. Preparation and characterization of potential decalindione substrates of horse liver alcohol dehydrogenase
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The preparations of ten decalindiones for investigation as substrates of horse liver alcohol dehydrogenase are reported.The structure characterizations include clarifications of some ambiguities in the decalin literature.
- Jones, J. Bryan,Dodds, David R.
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p. 2397 - 2404
(2007/10/02)
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- Lewis Acid-prompted Conjugate Reduction of α,β-Unsaturated Carbonyl Compounds by 2-Phenylbenzothiazoline (2-Phenyl-2,3-dihydrobenzothiazole)
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Reduction of various α,β-unsaturated ketones (3a-g) and (4a-d) in methanol by the benzothiazoline (1) in the presence of aluminium chloride gives, in all cases, the corresponding saturated ketones (5a-g) and (6a-d)without any of the unsaturated or saturated alcohol.Reduction of α,β-unsaturated esters (7a,b) similarly gives the saturated esters (9a,b), while reaction of cinnamaldehyde (8) with compound (1) does not occur at all.Among the Lewis acids examined, aluminium chloride gives the best results.Reduction of 2'-azachalcone (21) with 2-phenylbenzothiazoline reveals that, in the reduction product, the deuterium atom is located at the β-position with respect to the carbonyl group.The result obtained from the reduction of the same substrate with compound (1) in methanol shows that no incorporation of a hydrogen atom from the solvent takes place and suggests (indirectly) that the introduced hydrogen atom at the α-position of the product comes from the benzothiazoline (1).The reaction of (Z)-1,2-dibenzoyl-1,2-diphenylethylene (30) with compound (1) in the presence of aluminium chloride stereospecifically yields meso-1,2-dibenzoyl-1,2-diphenylethane (31).This shows that the transfer of two hydrogens from compound (1) to the carbon-carbon double bond of the enone proceeds via cis-addition.Experiments with ethyl phenylpropiolate (28) also support cis-reduction for the present conjugate reduction.These results are interpreted in terms of a mechanism involving synchronous transport of a pair of hydrogens from the benzothiazoline (1); i.e a cyclic addition of the two hydrogens either in exact or nearly exact concurrence.
- Chikashita, Hidenori,Miyazaki, Makoto,Itoh, Kazuyoshi
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p. 699 - 706
(2007/10/02)
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- Oxidation of trans-Decahydronaphthalene in Acetic Anhydride
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The oxidation of trans-decahydronaphthalene (1) was carried out in acetic anhydride with oxygen in the presence of Co(OAc)2, Ce(OAc)3, and NH4Br.Decahydronaphthyl acetates were obtained as main oxidation products in a selectivity of 81 molpercent at 120 degC.In addition, relative reactivities of hydrogen atoms of 1 were determined at temperatures from 90 to 120 degC.
- Yazu, Kaumasa,Wakabayashi, Takeshige,Nakayama, Tetsuo
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p. 1409 - 1412
(2007/10/02)
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- A CONFIGURATION-RETAINING α,β-DIOL TO 1,4-DIOXANE CONVERSION
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Cis-Perhydronaphthalene-2,3-diol treated with ethyl diazoacetate/rhodium(II) pivalate gives the mono-O-alkylation product which cyclizes readily to the lactone(dioxanone)- Photochemical deoxygenation with trichlorosilane affords the dioxane derivative perhydro-1,4-dioxaanthracene.
- Hosten, N. G. C.,Tavernier, D.,Anteunis, M. J. O.
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p. 183 - 186
(2007/10/02)
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- SELECTIVE REDUCTION OF CARBONYL COMPOUNDS BY DIPHENYLSTIBINE
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Carbonyl compounds were selectively reduced by diphenylstibine in the presence of Lewis acid.
- Huang, Yaozeng,Shen, Yanchang,Chen, Chen
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p. 5171 - 5172
(2007/10/02)
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- HYDROGENATION AND HYDROGENOLYSIS. XVII. THE SELECTIVITIES OF PLATINUM GROUP METALS IN CATALYTIC HYDROGENATION OF 2-NAPHTHOL AND TETRAHYDRO-2-NAPHTHOLS.
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Catalytic hydrogenation of 2-naphthol (NL) with the six platinum metals has been studied in t-BuOH at 80 degree C and 4-5 MPa H//2 pressure. Selectivities for formation of 1,2,3,4- and 5,6,7,8-tetrahydro-2-naphthols (ac- and ar-TLs) have been determined by application of a kinetic equation. ar-TL was formed more predominantly than ac-TL over all the metals. The hydrogenation of ac- and ar-TLs has also been studied under the same conditions for comparison. The hydrogenation of NL and ar-TL was accompanied by extensive hydrogenolysis to give decalins over Os, Ir, and Pt, whereas the hydrogenolysis occurred only slightly over Ru, Rh, and Pd. In general the hydrogenolysis occurred to much lesser extents with ac-TL. The amounts of 2-decalone formed in hydrogenation of ar-TL have been determined by application of the kinetic equation.
- Nishimura,Ohbuchi,Ikeno,Okada
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p. 2557 - 2564
(2007/10/02)
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- CONVERSION OF N,N-DIMETHYLHYDRAZONES TO CARBONYL COMPOUNDS BY CLAY-SUPPORTED FERRIC NITRATE
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Cleavage of N,N-dimethylhydrazones is cleanly effected with good yield in dichloromethane using the extremely inexpensive clay-supported ferric nitrate.
- Laszlo, Pierre,Polla, Eugenio
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p. 3309 - 3312
(2007/10/02)
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- On the Stereoelectronic Requirements of 1,2-Rearrangements of Vinyl Cations
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The triflates 8,9,12,17,19, and 23 have been synthesized to investigate their solvolysis products in absol. 2,2,2-trifluoroethanol (TFE) (Table 1).The kinetics of the solvolysis in 50percent ethanol have been measured as well.The rate constants give a straight correlation line when we apply an approximate Taft's equation, from which we deduce that the solvolyses take place by a kc mechanism; one exception is 12, as it reacts with S-O bond cleavage.We also deduce that the value of ρ* does not depend on steric factors.Relations between structure and rearrangement of vinyl cations are discussed.Mechanisms for the formation of reaction products are proposed.
- Collins, Clair J.,Martinez, Antonio Garcia,Alvarez, Roberto Martinez,Aguirre, Juan Arranz
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p. 2815 - 2824
(2007/10/02)
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- VANADIUM(V) PEROXO COMPLEXES. NEW VERSATILE BIOMIMETIC REAGENTS FOR EXPOXIDATION OF OLEFINS AND HYDROXYLATION OF ALKANES AND AROMATIC HYDROCARBONS.
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Novel covalent vandium(V) oxo peroxo complexes of general formula VO(O//2)(O-N)LL prime and anionic complexes with the general formula left bracket VO(O//2)(Pic)//2 right bracket ** minus A** plus L were synthesized and characterized by physicochemical methods and X-ray crystallography. The crystal structure of VO(O//2)(Pic) multiplied by (times) 2H//2O (Ia) revealed a pentagonal-bipyramidal environment, with a significant hydrogen bonding between the peroxo moiety and the equatorial water molecule. Protonated type II complexes (A** plus equals H** plus ) are dissociated in an aqueous solution and have an acidic nature (pK//a equals 1. 8) but are undissociated in a nonprotic solution, with a presumably peracid-like oxohydroperoxo structure. It is shown that vanadium peroxo complexes are effective oxidants in nonprotic solvents under mild conditions. They transform olefins to epoxides and cleavage products in a nonsteoroselective fashion (cis-2-butene gave a mixture of cis and trans epoxides). More interestingly, they hydroxylate aromatic hydrocarbons to phenols and alkanes to alcohols and ketones.
- Mimoun,Saussine,Daire,Postel,Fischer,Weiss
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p. 3101 - 3110
(2007/12/18)
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- SELECTIVITE DE LA REDUCTION D'α-ENONES POLYCYCLIQUES PAR LES BOROHYDRURES: EFFET DE L'ADDITION DE TETRAMETHYL-ETHYLENEDIAMINE AU BOROHYDRURE DE TETRABUTYLAMMONIUM
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Δ1,9octalone, Δ1,9-10-methyl octalone and testosterone were reduced by NBu4BH4, alone or in the presence of tetramethylethylenediamine (TMEDA), in THF and in toluene.With TMEDA, the first step of the reduction is the regioselective 1,4 attack by BH4(1-) which leads either to the saturated ketones or to the corresponding saturated alcohols.The results observed under different conditions were interpreted by the intervention of various reductive species: diborane, enoxyborohydrides in the absence of TMEDA, amine-borane in its presence.
- D'incan, E.,Loupy, A.,Maia, A.,Seyden-Penne, J.,Viout, P.
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p. 2923 - 2927
(2007/10/02)
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- STEREOCHIMIE - LIII. CONTROLE ORBITALAIRE DE LA STEREOCHIMIE DES REACTIONS - IV HYDROCYANATION 1,4 DE CETO-3 Δ1-STEROIDES ET D'OCTALONES APPARENTEES
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Hydrocyanation at sites other than ring junctions does not exhibit the same stereoselectivity in the keto-3 Δ1-steroid series as in analogous bicyclic compounds.Irrespective of the presence or the absence of an angular methyl group, the kinetic product has always an axial cyano group; however a stereoelectronic control of the reverse reaction explains why under thermodynamic conditions, only enones of the decalin series give both axial and equatorial epimers.A conformational analysis based on the conservation of the torsion angle and the maximum overlap of orbitals accounts for these facts.
- Agami, C.,Fadlallah, M.,Levisalles, J.
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p. 903 - 908
(2007/10/02)
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- Models for Glycoside Hydrolysis. Synthesis and Hydrolytic Studies of the Anomers of a Conformationally Rigid Acetal
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The methyl acetals of 2-hydroxy-3-oxa-trans-decalin were synthesized as models for conformationally rigid methyl glycosides.The compounds were prepared by Baeyer-Villiger oxidation of trans-hexahydrohydrindan-2-one followed by reduction of the resulting lactone with diisobutylaluminum hydride.Treatment of the hemiacetal with methanol and an acid catalyst afforded a mixture of acetals which were separated by chromatography and identified by NMR.Hydrolytic studies were carried out under a range of acid concentrations and temperatures.The mechanistic implications of the relative hydrolysis rates (axial/equatorial ratio of 1.51+/-0.22) and activation parameters are discussed.
- Eikeren, Paul van
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p. 4641 - 4645
(2007/10/02)
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- SOME COMMENTS ON THE THERMAL STABILITY OF SUBSTITUTED AMMONIUM, PHOSPHONIUM, AND ARSONIUM PERMANGANATES AND THEIR USE IN ALKANE OXIDATION
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Tetraethyl- and tetrabutylammonium permanganate are less prone to explosive decomposition when heated than are benzyl(triethyl)ammonium and methyl(triphenyl)phosphonium permanganate and are about equally effective as oxidants for the conversion of alkanes into alcohol and ketones.
- Leddy, Bernard P.,McKervey, M.Antony,McSweeney, Peter
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p. 2261 - 2264
(2007/10/02)
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