- Dienolates of Cycloalkenones and α,β-Unsaturated Esters Form Diels–Alder Adducts by a Michael/Michael-Tandem Reaction Rather Than in One Step
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α,β-Unsaturated esters and lithium 1,3-dien-2-olates are known to furnish bicyclic lithium enolates by anionic Diels–Alder reactions. However, in principle, the respective products might form not only in a single step but also in two consecutive – or “tandem” – Michael additions, the first of which occurs intermolecularly, the second intramolecularly. Three cyclic lithium dienolates and four esters with a stereogenic Cα=Cβ bond reacted to give Diels–Alder adducts (10 times) or failed to react (2 times). Seven of the reactive combinations furnished adducts wherein the configuration of the former ester moiety had in part inverted. This precludes concerted pathways as their origins. This was a surprise since donors at C-2 of the 1,3-diene accelerate normal electron-demand Diels–Alder reactions in the order alkyl ⊕O? being a far better donor still, it is not obvious why the mechanism is non-concerted rather than concerted (and still more asynchronous).
- Loesche, Ann-Christine,Brückner, Reinhard
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Read Online
- Discovery of Salidroside-Derivated Glycoside Analogues as Novel Angiogenesis Agents to Treat Diabetic Hind Limb Ischemia
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Therapeutic angiogenesis is a potential therapeutic strategy for hind limb ischemia (HLI); however, currently, there are no small-molecule drugs capable of inducing it at the clinical level. Activating the hypoxia-inducible factor-1 (HIF-1) pathway in skeletal muscle induces the secretion of angiogenic factors and thus is an attractive therapeutic angiogenesis strategy. Using salidroside, a natural glycosidic compound as a lead, we performed a structure-activity relationship (SAR) study for developing a more effective and druggable angiogenesis agent. We found a novel glycoside scaffold compound (C-30) with better efficacy than salidroside in enhancing the accumulation of the HIF-1α protein and stimulating the paracrine functions of skeletal muscle cells. This in turn significantly increased the angiogenic potential of vascular endothelial and smooth muscle cells and, subsequently, induced the formation of mature, functional blood vessels in diabetic and nondiabetic HLI mice. Together, this study offers a novel, promising small-molecule-based therapeutic strategy for treating HLI.
- Liu, Caiping,Han, Jingxuan,Marcelina, Olivia,Nugrahaningrum, Dyah Ari,Huang, Song,Zou, Meijuan,Wang, Guixue,Miyagishi, Makoto,He, Yun,Wu, Shourong,Kasim, Vivi
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p. 135 - 162
(2022/01/14)
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- Oxidative and Redox-Neutral Approaches to Symmetrical Diamines and Diols by Single Electron Transfer/Hydrogen Atom Transfer Synergistic Catalysis
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Homocoupling reactions of benzylamines and benzyl alcohols were examined under synergistic catalysis conditions with a photoredox catalyst and thiobenzoic acid as a hydrogen atom abstractor. When pivalaldehyde was used as an electron acceptor, oxidative dimerization proceeded selectively, whereas the use of benzaldehydes or iminium ions as electron acceptors resulted in redox-neutral coupling. These reactions afforded symmetrical 1,2-diamines and 1,2-diols in good yields.
- Fujita, Masashi,Kobayashi, Fumihisa,Ide, Takafumi,Egami, Hiromichi,Hamashima, Yoshitaka
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supporting information
p. 7151 - 7155
(2020/12/01)
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- Structure-Guided Optimization of Dipeptidyl Inhibitors of Norovirus 3CL Protease
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Acute gastroenteritis caused by noroviruses has a major impact on public health worldwide in terms of morbidity, mortality, and economic burden. The disease impacts most severely immunocompromised patients, the elderly, and children. The current lack of approved vaccines and small-molecule therapeutics for the treatment and prophylaxis of norovirus infections underscores the need for the development of norovirus-specific drugs. The studies described herein entail the use of the gem-dimethyl moiety as a means of improving the pharmacological activity and physicochemical properties of a dipeptidyl series of transition state inhibitors of norovirus 3CL protease, an enzyme essential for viral replication. Several compounds were found to be potent inhibitors of the enzyme in biochemical and cell-based assays. The pharmacological activity and cellular permeability of the inhibitors were found to be sensitive to the location of the gem-dimethyl group.
- Rathnayake, Athri D.,Kim, Yunjeong,Dampalla, Chamandi S.,Nguyen, Harry Nhat,Jesri, Abdul-Rahman M.,Kashipathy, Maithri M.,Lushington, Gerald H.,Battaile, Kevin P.,Lovell, Scott,Chang, Kyeong-Ok,Groutas, William C.
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p. 11945 - 11963
(2020/11/26)
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- Expeditious Total Synthesis of Hemiasterlin through a Convergent Multicomponent Strategy and Its Use in Targeted Cancer Therapeutics
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Hemiasterlin is an antimitotic marine natural product with reported sub-nanomolar potency against several cancer cell lines. Herein, we describe an expeditious total synthesis of hemiasterlin featuring a four-component Ugi reaction (Ugi-4CR) as the key st
- Carroll, Jason S.,Charoenpattarapreeda, Jiraborrirak,Spring, David R.,Walsh, Stephen J.
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supporting information
p. 23045 - 23050
(2020/11/11)
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- Aerobic C-C and C-O bond formation reactions mediated by high-valent nickel species
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Nickel complexes have been widely employed as catalysts in C-C and C-heteroatom bond formation reactions. While Ni(0), Ni(i), and Ni(ii) intermediates are most relevant in these transformations, recently Ni(iii) and Ni(iv) species have also been proposed to play a role in catalysis. Reported herein is the synthesis, detailed characterization, and reactivity of a series of Ni(ii) and Ni(iii) metallacycle complexes stabilized by tetradentate pyridinophane ligands with various N-substituents. Interestingly, while the oxidation of the Ni(ii) complexes with various other oxidants led to exclusive C-C bond formation in very good yields, the use of O2 or H2O2 as oxidants led to formation of appreciable amounts of C-O bond formation products, especially for the Ni(ii) complex supported by an asymmetric pyridinophane ligand containing one tosyl N-substituent. Moreover, cryo-ESI-MS studies support the formation of several high-valent Ni species as key intermediates in this uncommon Ni-mediated oxygenase-type chemistry.
- Gómez, Laura,Mirica, Liviu M.,Planas, Oriol,Rath, Nigam P.,Ribas, Xavi,Smith, Sofia M.
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p. 10366 - 10372
(2019/11/20)
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- Donor–Acceptor Complex Enables Alkoxyl Radical Generation for Metal-Free C(sp3)–C(sp3) Cleavage and Allylation/Alkenylation
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The alkoxyl radical is an essential and prevalent reactive intermediate for chemical and biological studies. Here we report the first donor–acceptor complex-enabled alkoxyl radical generation under metal-free reaction conditions induced by visible light. Hantzsch ester forms the key donor–acceptor complex with N-alkoxyl derivatives, which is elucidated by a series of spectrometry and mechanistic experiments. Selective C(sp3)-C(sp3) bond cleavage and allylation/alkenylation is demonstrated for the first time using this photocatalyst-free approach with linear primary, secondary, and tertiary alkoxyl radicals.
- Zhang, Jing,Li, Yang,Xu, Ruoyu,Chen, Yiyun
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supporting information
p. 12619 - 12623
(2017/09/11)
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- Br?nsted Acid-Catalyzed Intramolecular Hydroarylation of β-Benzylstyrenes
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Using triphenylmethylium tetrakis(pentafluorophenyl)borate as a convenient Br?nsted acid precatalyst, β-(α,α-dimethylbenzyl)styrenes are shown to cyclize efficiently to afford a variety of new indanes that possess a benzylic quaternary center. The geminal dimethyl-containing quaternary center is proposed to be necessary to arm the substrate for cyclization through steric biasing.
- Cai, Xiao,Keshavarz, Amir,Omaque, Justin D.,Stokes, Benjamin J.
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supporting information
p. 2626 - 2629
(2017/05/24)
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- Design of Potent and Druglike Nonphenolic Inhibitors for Catechol O-Methyltransferase Derived from a Fragment Screening Approach Targeting the S-Adenosyl- l -methionine Pocket
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A fragment screening approach designed to target specifically the S-adenosyl-l-methionine pocket of catechol O-methyl transferase allowed the identification of structurally related fragments of high ligand efficiency and with activity on the described orthogonal assays. By use of a reliable enzymatic assay together with X-ray crystallography as guidance, a series of fragment modifications revealed an SAR and, after several expansions, potent lead compounds could be obtained. For the first time nonphenolic and small low nanomolar potent, SAM competitive COMT inhibitors are reported. These compounds represent a novel series of potent COMT inhibitors that might be further optimized to new drugs useful for the treatment of Parkinson's disease, as adjuncts in levodopa based therapy, or for the treatment of schizophrenia.
- Lerner, Christian,Jakob-Roetne, Roland,Buettelmann, Bernd,Ehler, Andreas,Rudolph, Markus,Sarmiento, Rosa María Rodríguez
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p. 10163 - 10175
(2016/12/07)
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- Compositions for Treatment of Cystic Fibrosis and Other Chronic Diseases
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The present invention relates to pharmaceutical compositions comprising an inhibitor of epithelial sodium channel activity in combination with at least one ABC Transporter modulator compound of Formula A, Formula B, Formula C, or Formula D. The invention also relates to pharmaceutical formulations thereof, and to methods of using such compositions in the treatment of CFTR mediated diseases, particularly cystic fibrosis using the pharmaceutical combination compositions.
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Paragraph 0553
(2015/09/22)
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- Access to nitriles from aldehydes mediated by an oxoammonium salt
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A scalable, high yielding, rapid route to access an array of nitriles from aldehydes mediated by an oxoammonium salt (4-acetylamino-2,2,6,6-tetramethylpiperidine-1-oxoammonium tetrafluoroborate) and hexamethyldisilazane (HMDS) as an ammonia surrogate has been developed. The reaction likely involves two distinct chemical transformations: reversible silyl-imine formation between HMDS and an aldehyde, followed by oxidation mediated by the oxoammonium salt and desilylation to furnish a nitrile. The spent oxidant can be easily recovered and used to regenerate the oxoammonium salt oxidant.
- Kelly, Christopher B.,Lambert, Kyle M.,Mercadante, Michael A.,Ovian, John M.,Bailey, William F.,Leadbeater, Nicholas E.
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supporting information
p. 4241 - 4245
(2015/04/14)
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- PYRIMIDONE DERIVATIVES AND THEIR USE IN THE TREATMENT, AMELIORATION OR PREVENTION OF A VIRAL DISEASE
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The present invention relates to a compound having the general formula (I), optionally in the form of a pharmaceutically acceptable salt, solvate, polymorph, codrug, cocrystal, prodrug, tautomer, racemate, enantiomer, or diastereomer or mixture thereof, which are useful in treating, ameloriating or preventing a viral disease. Furthermore, specific combination therapies are disclosed.
- -
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Paragraph 0349-0351
(2014/07/22)
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- MODULATORS OF ATP-BINDING CASSETTE TRANSPORTERS
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The present invention relates to modulators of ATP-Binding Cassette (“ABC”) transporters or fragments thereof, including Cystic Fibrosis Transmembrane Conductance Regulator, compositions thereof, and methods therewith. The present invention also relates to methods of treating ABC transporter mediated diseases using such modulators.
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- Trisubstituted imidazoles as mycobacterium tuberculosis glutamine synthetase inhibitors
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Mycobacterium tuberculosis glutamine synthetase (MtGS) is a promising target for antituberculosis drug discovery. In a recent high-throughput screening study we identified several classes of MtGS inhibitors targeting the ATP-binding site. We now explore o
- Gising, Johan,Nilsson, Mikael T.,Odell, Luke R.,Yahiaoui, Samir,Lindh, Martin,Iyer, Harini,Sinha, Achyut M.,Srinivasa, Bachally R.,Larhed, Mats,Mowbray, Sherry L.,Karlén, Anders
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experimental part
p. 2894 - 2898
(2012/06/01)
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- Synthesis of [2H5]-ebastine fumarate and [ 2H5]-hydroxyebastine
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This study describes the synthesis of deuterium-labelled ebastine fumarate and its deuterium-labelled metabolite hydroxyebastine. The synthesis of the two desired compounds both used [2H5]-bromodiphenylmethane as deuterium-labelled reagent, which was synthesized beforehand in three steps. [2H5]-ebastine was synthesized in further three steps with a 27% overall yield and [2H5]-hydroxyebastine was synthesized in further seven steps with a 13% overall yield.
- Yu, Zhoujie,Wang, Wei,Chen, Liqin
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experimental part
p. 352 - 356
(2012/06/01)
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- COMPOSITIONS FOR TREATMENT OF CYSTIC FIBROSIS AND OTHER CHRONIC DISEASES
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The present invention relates to pharmaceutical compositions comprising an inhibitor of epithelial sodium channel activity in combination with at least one ABC Transporter modulator compound of Formula A, Formula B, Formula C, or Formula D. The invention also relates to pharmaceutical formulations thereof, and to methods of using such compositions in the treatment of CFTR mediated diseases, particularly cystic fibrosis using the pharmaceutical combination compositions.
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- UREA GLUCOKINASE ACTIVATORS
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This application relates to novel urea glucokinase activators and use of the compounds of the invention for preparation of a medicament for the treatment of various diseases, e.g. for the treatment of type 2 diabetes. Further encompassed is a pharmaceutic
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Page/Page column 117
(2008/12/07)
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- FEXOFENADINE POLYMORPHS AND PROCESSES OF PREPARING THE SAME
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Anhydrous crystalline fexofenadine hydrochloride Form C, crystalline fexofenadine acetate monohydrate Form D, crystalline fexofenadine acetate dihydrate Form E and crystalline fexofenadine free base monohydrate Form F, processes of preparing the same, pharmaceutical compositions thereof, therapeutic uses thereof and methods of treatment therewith.
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Page/Page column 23-24
(2008/06/13)
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- New Synthetic Methods for Seven- and Eight-Membered Cyclic Ethers Based on the Ring-Expansion Reactions of Hydroxy or Lithioxy Methoxyallenylisochroman Derivatives
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The Pd(0)-catalyzed ring-expansion reactions of hydroxy methoxyallenyl-4,4-dialkylisochroman derivatives in the presence of P(o-tolyl)3 proceeded smoothly via hydropalladation to give 3-benzoxepan-1-one derivatives in high yields. Treatment of
- Nagao, Yoshimitsu,Tanaka, Satoru,Hayashi, Kazuhiko,Sano, Shigeki,Shiro, Motoo
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p. 481 - 484
(2007/10/03)
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- ARYL SULFONAMIDES
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Compounds are provided that act as potent antagonists of the CCR9 receptor, and which have been further confirmed in animal testing for inflammation, one of the hallmark disease states for CCR9. The compounds are generally aryl sulfonamide derivatives and are useful in pharmaceutical compositions, methods for the treatment of CCR9-mediated diseases, and as controls in assays for the identification of CCR9 antagonists.
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- Compounds that modulate PPAR activity and methods of preparation
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This invention discloses compounds that alter PPAR activity. The invention also discloses pharmaceutically acceptable salts of the compounds, pharmaceutically acceptable compositions comprising the compounds or their salts, and methods of using them as therapeutic agents for treating or preventing hyperlipidemia and hypercholesteremia in a mammal. The present invention also discloses methods for making the disclosed compounds.
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- Electrophilic peptide analogs as inhibitors of trypsin-like enzymes
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This invention relates to electrophilic dipeptide analogs conjugated to an N,N-disubstituted alpha -amino acid as inhibitors of trypsin-like serine protease enzymes.
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- A new synthesis of carboxyterfenadine (fexofenadine) and its bioisosteric tetrazole analogs
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A new synthesis of carboxyterfenadine (4), based on the conversion of a α-halo-alkylarylketone into the corresponding substituted 2-arylalkanoic ester, is described. The enantioselective synthesis of its two bioisosteric tetrazole analogs together with preliminary biological results are reported. Copyright (C) 1999 Elsevier Science S.A.
- Di Giacomo, Barbara,Coletta, Donato,Natalini, Benedetto,Ni, Ming-Hong,Pellicciari, Roberto
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p. 600 - 610
(2007/10/03)
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- Synthesis of substituted benzyl 2-methyl-2-phenylpropyl ethers and their moth-proofing activity on wool against larvae of Anthrenus fasciatus
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Synthesis of new moth-proofing agents is necessary to overcome the damage caused by clothes moths and carpet beetles to hosiery and upholstery. In the present paper substituted benzyl 2-methyl-2-phenylpropyl ethers were synthesised and evaluated for moth-proofing activity. Two compounds were found to provide protection against larvae of Anthrenus fasciatus at levels of 1.0 and 10 g kg-1 respectively. The introduction of a methyl group in the para position of the benzene ring attached to C2 of the 2-methylpropyl chain (ring A) increased moth-proofing activity. The introduction of a phenoxy ring at the meta position of the benzyl nucleus (ring B) also increased activity, while the presence of a nitro group on the benzyl nucleus (ring B) decreased activity.
- Acharya,Joshi
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p. 850 - 856
(2007/10/03)
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- Heterocyclic compounds for the treatment of CNS and cardiovascular disorders
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Novel aromatic bicyclic amines of formula (I) STR1 are useful in treating central nervous system disorders and cardiac arrhythmias and cardiac fibrillation.
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- Rational design of boropeptide thrombin inhibitors: β,β-Dialkyl-phenethylglycine P2 analogs of DuP 714 with greater selectivity over complement factor I and an improved safety profile
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The potent boropeptide thrombin inhibitor DuP 714 caused side effects in laboratory animals that appear to be related to its ability to inhibit complement factor I, thereby activating the complement cascade. Using X-ray crystal structure information, we have designed compounds that have greater selectivity for thrombin over factor I and that have reduced tendency to produce these side effects.
- Fevig, John M.,Buriak Jr., Joseph,Cacciola, Joseph,Alexander, Richard S.,Kettner, Charles A.,Knabb, Robert M.,Pruitt, James R.,Weber, Patricia C.,Wexler, Ruth R.
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p. 301 - 306
(2007/10/03)
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- Substituent effects on the C-C bond strength, 20 geminal substituent effects, 14: Stabilization of the cyano(dimethylamino)methyl radical - Synergistic effect due to interaction between α-amino and α-cyano groups on the radical stabilization energy
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The thermolysis reactions of 3a and 2a, b were studied over a temperature range of 40°C and the activation parameters were determined. They were compared with the activation parameters of structurally comparable hydrocarbons of similar strain in order to obtain the radical stabilization enthalpies RSEs of the cyano(dimethylamino)methyl radical 1a. For this comparison the geminal interaction enthalpies of the cyano and the dimethylamino groups in the ground state had to be determined for the series of amino nitrites 4a-4c and 4j-4n by thermochemical methods. The geminal interaction in the ground state varies between -0.6 kcal/mol stabilization in 4a and a destabilization of +10.7 and +7.0 kJ mol-1 for secondary and tertiary α-dialkylaminonitriles, respectively. A synergistic (i.e. more than additive) stabilization enthalpy of 26 kJ mol-1 of la was found in contrast to predictions in the literature. This stabilization is interpreted by conjugation between the substituents, which are separated by the radical center. (Chemical Equation Presented) VCH Verlagsgesellschaft mbH, 1997.
- Welle, Frank M.,Verevkin, Sergey P.,Beckhaus, Hans-Dieter,Ruechardt, Christoph
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p. 155 - 163
(2007/10/03)
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- Antihistaminic compounds, process for their preparation and pharmaceutical compositions containing them
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The present invention relates to terfenadine derivatives of formula where R?, which is in position 1 or 2 of the tetrazole ring, stands for H, or a linear or branched alkyl group containing from 1 to 6 carbon atoms; R? and R?, different from one another, are selected between H and OH, and their pharmaceutically acceptable salts.
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- Alkylsilver and Alkylgold Reagents, II. Cyano(methyl)argentates: Spectroscopy, Selectivity as Methylating Reagents, Comparison with Other Methylsilver Reagents
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As the first examples of a new type of Ag complex the cyanoargentates MeAg(CN)Li (1), Me2Ag(CN)Li2 (2), MeAg(CN)MgBr (3), and Me2Ag(CN)(MgBr)2 (4) were prepared in solution or suspension by transmetallation of MeLi or MeMgBr with AgCN.Compared to AgBr-derived reagents, such as MeAg*MgBr2 (5) and Me2AgMgBr (6), the cyano(methyl)argentates are clearly less sensitive to light.According to the IR spectrum, the Ag atom of 2 is connected with the cyano group.The 13C-NMR spectra of 2, 4, 5, and 6 furnish proof of the Ag-Me group in these compounds and points to the partial structure Ag-Me-Mg in 4, 5, and 6. - Complexes 2 (stable up to 20 deg C), 4, 5, and 6 methylate the ketoaldehyde 13 with high selectivity at the aldehyde group (best yield with 4). 4, 5, and 6 exhibit high cheleselectivity in the reaction with the hydroxy diketone 22 (best yield with 4) and comparable intermolecular competitive systems. 2 and 6 methylate 11,12-epoxy-2-dodecanone (28) with virtually complete regioselective ring opening to give 11-hydroxy-2-tridecanone (29).In contrast to Me2Cu(CN)Li2 (7) and Me2CuMgBr, the analogous reagents Me2Ag(CN)Li2 (2) and Me2AgMgBr (6) methylate styrene oxide (32), and 6 also methylates α-methylstyrene oxide (36) in α-position to the phenyl residue with high selectivity, yielding nearly exclusively 2-phenylpropanol (33) or 2-methyl-2-phenylpropanol (37), respectively.The selective "α-attack" of Ag reagents is explained by fixation of the reagent to the phenyl residue of 32 and 36 in the first reaction step.
- Kauffmann, Thomas,Neiteler, Christel,Robbe, Sonja
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p. 2409 - 2418
(2007/10/02)
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- Saturated heterocyclic carboxamide derivatives
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A saturated heterocyclic carboxamide derivative of the following general formula (I) and salts thereof which have platelet activating factor (PAF) antagonizing activity. STR1
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- Solvent Effects on Solvolytic Reactivity. A Diagnostic Test for Neighboring-Group Assistance by ? Conjugation in Solvolysis Reactions
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The solvolysis rates of 13 arenesulfonates have been determined in mixtures of ethanol and water (the E-series solvents) and acetic acid and formic acid (the A-series solvents).The substrates studied include the following: neophyl (1), 2-adamantyl (2), neopentyl (3), and cyclooctyl (4) tosylates; cyclopropylcarbinyl pemsylate (5a) and tosylate (5b); exo-2-norbornyl tosylate (6); cyclobutylcarbinyl (7), cyclobutyl (8), and pinacolyl (9) brosylates; cyclopentyl (10), cyclohexyl (11), and 2-propyl (12) tosylates; and cyclopentylcarbinyl brosylate (13).Correlations of the rate data by eq 1 t(Y) = a + b log kt(neophyl-OTs)> showed that the various substrates responded differently to the examined solvent effects on the solvolytic reactivity.For compounds 2-4, linear correlations were obtained.For compounds 5-9, E-line, A-line dispersions were noted which diverged with increasing ionizing power; for compounds 10-12, parallel E-line, A-line dispersions were obtained; and for compound 13, an E-line, A-line dispersion was observed which converged with increasing ionizing power.Stastistical analyses of the rate data correlations confirmed the significance of the E or A classification of data.The results are interpreted in terms of differences in the involvement of solvent in the transition state for those solvolyses assisted by bridging from those assisted by C-C ? bond hyperconjugation.
- Roberts, Donald D.
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p. 2521 - 2526
(2007/10/02)
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- OXIDATIVE CLEAVAGE OF SILICON-CARBON BONDS IN ORGANOSILICON FLUORIDES TO ALCOHOLS
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Certain functional silyl groups have been shown to be synthetically equivalent to the OH group.All of the C-Si bonds in organosilicon fluorides, K2 and RnSiF4-n (n=1,2,3) are cleaved by m-chloroperbenzoic acid (MCPBA) in DMF to give the corresponding alcohols in high yields.Although the reaction with RSiF5(2-) and RSiF3 proceeds without any additive, cleavage of R2SiF2 and R3SiF requires, respectively, a catalytic or excess amount of KF.A triorganoethoxysilane also undergoes similar oxidative cleavage reactions in the presence of an excess amount of KF.The MCPBA-oxidation of exo- and endo-2-norbornyl-silicate and -trifluorosilane proceeds stereospecifically with retention of configuration at carbon.A remarkable solvent effect has been observed in the oxidative cleavage of RSiF3.A plausible mechanism involves a hexacoordinate silicon species in which the organic group intramolecularly migrates from Si to O of the coordinated MCPBA.
- Tamao, K.,Kakui, T.,Akita, M.,Iwahara, T.,Kanatani, R.,et al.
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p. 983 - 990
(2007/10/02)
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- Catalytic Replacement of Unactivated Alkane Carbon-Hydrogen Bonds with Carbon-X Bonds (X = Nitrogen, Oxygen, Chlorine, Bromine, or Iodine). Coupling of Intermolecular Hydrocarbon Activation by MnIIITPPX Complexes with Phase-Transfer Catalysis
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A simple system has been devised to facilitate the first processes for the catalytic replacement of unactivated alkane C-H bonds with C-X bonds, X = nitrogen and iodine.The system also enables alkane C-H bonds to be replaced by C-X bonds, X = chlorine, bromine, and oxygen.The system is composed of two liquid phases and the oxidant iodosylbenzene (iodosobenzene).The alkane substrate, the MnIIITPPX catalyst, and the organic solvent (dichloromethane, chlorobenzene, or other aromatic hydrocarbon) constitute one phase, a saturated aqueous solution of the sodium salt of the anion to be incorporated into the alkane, NaX, X = N3(1-), NCO(1-), I(1-), Br(1-), or Cl(1-), constitutes the second phase, and the sparingly soluble oxidant iodosylbenzene constitutes a third phase.When the two liquid phases and the oxidant iodosylbenzene are stirred under an inert atmosphere, both RX and ROH products are produced catalytically based on MnTPP and in reasonable yield based on iodosylbenzene.The MnTPP moiety functions as a catalyst for C-H bond cleavage and for phase transfer of X(1-) from the aqueous phase to the organic phase where the functionalization chemistry takes place.The oxidant hypochlorite can be used in place of, but is less effective than, iodosylbenzene, and the oxidants hydrogen peroxide, periodate, and persulfate are ineffective.Product distributions obtained from the oxidation of cyclohexane, isobutane, 2,3-dimethylbutane, and tert-butylbenzene are most consistent with a product-determining step that involves transfer of X from manganese to a free alkyl radical intermediate.
- Hill, Craig L.,Smegal, John A.,Henly, Timothy J.
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p. 3277 - 3281
(2007/10/02)
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- Hydrocarbon Functionalization by the (Iodosylbenzene)manganese(IV) Porphyrin Complexes from the (Tetraphenylporphinato)manganese(III)-Iodosylbenzene Catalytic Hydrocarbon Oxidation System. Mechanism and Reaction Chemistry
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The two types of complexes isolated from the reaction of (tetraphenylporphinato)manganese(III) derivatives, XMnIIITPP, with iodosylbenzene - IVTPP(OIPh)>2O, 1, X = Cl- or Br-, and IVTPP>2O, 2, X = N3- - are capable of oxidizing alkane substrates in good yields at room temperature.Several lines of evidence establish the intermediacy of free alkyl radicals in the reactions of 1 and 2 with alkanes.Oxygen exchange with water in both the iodosyl (Mn-O-I) and μ-oxo (Mn-O-Mn) moieties of 1 suggests the formation of oxo manganese porphyrin complexes from these moieties.Hydrogen abstraction from the alkane substrate by an oxo manganese porphyrin intermediate is postulated to be mechanism for reaction of 1 and 2 with alkanes.Observation of a monomeric manganese(IV) porphyrin intermediate by EPR spectroscopy during the reactions of 1 with alkanes is consistent with the formation of a hydroxymanganese(IV) porphyrin complex resulting from substrate hydrogen abstraction by an oxo intermediate.The formation of RX product from oxidation of RH by 1 has been determined to result from ligand-transfer oxidation of free alkyl radicals by the porphyrin complexes in solution.Through competition reactions and time-dependent product formation studies, ligand-transfer oxidation by XMnIIITPP was found to be the major pathway for RX production.Observation of MnIITPP by EPR spectroscopy during the reactions of 1 with alkanes supports this conclusion.Formation of ROH product may result from ligand-transfer oxidation of free radicals or from the collapse of an intermediate caged radical pair.The mechanism of ROH product formation in the caged radical pair is postulated to be an outer-sphere electron-transfer process due to the expected slow rate of inner-sphere ligand transfer for the high-spin d3 hydroxymanganese(IV) porphyrin complex.Thus the ability of the substrate radical to undergo electron-transfer oxidation determines the ratio of radicals that undergo cage escape to give free radicals to radicals that undergo oxidation and subsequent formation of alcohol product in the caged species.Studies with tertiary substrates support these conclusions.
- Smegal, John A.,Hill, Craig L.
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p. 3515 - 3521
(2007/10/02)
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- PHOTOSUBSTITUTION OF BENZYL HYDROGENS WITH ALCOHOLIC MOIETIES. SELECTIVE FORMATION OF ALKYLBENZENE CARBINOLS
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Irradiations of alkylbenzene compounds with various alcohols in an air atmosphere, resulted in substitution of the benzyl hydrogens with alcoholic moieties in a very selective mode.
- Pasternak, Mordechai,Morduchowitz, Abraham
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p. 3439 - 3442
(2007/10/02)
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- HYDROFORMYLATION OF OLEFINS WITH PARAFORMALDEHYDE CATALYZED BY RHODIUM COMPLEXES
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The addition of formaldehyde to olefins is efficiently catalyzed by RhH2(O2COH)2 and gives the corresponding aldehydes in neutral solution.
- Okano, Tamon,Kobayashi, Teruyuki,Konishi, Hisatoshi,Kiji, Jitsuo
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p. 4967 - 4968
(2007/10/02)
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- 1,8,17,24-Tetraoxa(2,6)naphthalenophane-3,5,19,21-tetrayne-10,13-dicarboxylic Acid Derivatives, Novel Complexors of Aromatic Guests
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Synthesis and complexation behavior of the title molecules are described.Study of aromatic solvent induced shifts of these molecules support the contention that their large cavity can accomodate aromatic rings.The behavior of acid 1a in water suggests that this effect enhanced in aqueous medium, as is expected for formation of hydrophobic inclusion complexes.In contrast to the rigid naphthalenophanes (1), their saturated derivatives (7) exist in a collapsed conformation and do not incorporate aromatic guests.
- Jarvi, Esa T.,Whitlock, Howard W.
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p. 7196 - 7204
(2007/10/02)
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- The Surface of Silica as a Medium for the Radical and Ionic Decomposition of Diacyl Peroxides
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The rates of decomposition of β-phenylpropionyl peroxide 1, β-phenylisovaleryl peroxide 2, and β-phenylisovaleryl p-nitrobenzoyl peroxide 3 are much higher on silica surfaces than they are in solution.The products formed on silica surfaces are derived from both radical and ionic precursors except in the case of 3, for which the reaction may be entirely ionic.The relationships between the medium effects on the rates and on the products suggest that the ionic and radical parts of the reaction branch from a common polar intermediate.Both the ionic and radical products differ significantly from those formed in solution.In the neophyl radical, adsorption inhibits the migration of phenyl to form phenyl-tert-butyl radical.In the ionic reaction, there is extensive migration of methyl in competition with phenyl, in contrast to the behavior of neophyl derivatives in solvolysis reaction.Dihydrocoumarin, from 1, and dimethyldihydrocoumarin, from 2 and 3, are not formed at all in solution.Esters, which are often formed via carboxy inversion and related reactions when polar diacyl peroxides decompose in solution, appear to arise from electron transfer in radial-pair precursors.There is no evidence of carboxy inversion compounds or carbonic acid esters in the physically adsorbed products, although some RO-C(=O)+ groups (1-2percent) appear to be trapped by the silica.Rearranged and unrearranged neophyl cations are trapped more extensively as silyl ethers.Other ion-derived products are one of the phenylisobutylenes, several phenylbutenes, and the carboxylic acids.Coadsorbed oxygen or acetonitrile alters the product distribution partly by trapping radicals and partly by site preemption effects.
- Leffler, J.E.,Barbas, J.T.
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p. 7768 - 7773
(2007/10/02)
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