- Acid-catalyzed hydrolysis of bridged bi- and tricyclic compounds. XXXVII. Kinetics and mechanisms of 1- and 3-acetoxynortricyclanes
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The disappearance of 3- and 1-acetoxynortricyclanes (1 and 2) in aqueous perchloric acid was followed by capillary gas chromatography at different temperatures and acid concentrations. According to the activation parameters, solvent deuterium isotope effe
- Lajunen, Martti,Yli-Mannila, Rita,Salminen, Outi
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- Role of Dioxygen as an Activator in Olefin Metathesis
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Evidence is presented that the beneficial or essential influences often noted when small amounts of dioxygen are added to catalytic systems for olefin metathesis and ring-opening polymerization are due to the formation of epoxides and the corresponding me
- Ivin, Kenneth J.,Reddy, Boreddy S. R.,Rooney, John J.
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- Acid-catalyzed hydrolysis of bridged bi- and tricyclic compounds. XXXVIII - Kinetics and mechanisms of 1- and 3-nortricyclanols
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The disappearance of 1- and 3-nortricyclanols (1-OH and 2-OH) in aqueous perchloric acid was followed by capillary GC at different temperatures and acid concentrations. 1-OH is ca 1000 times more reactive than 2-OH. The activation parameters, solvent deut
- Lajunen, Martti,Lahti, Veli
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- OXIDATION OF NON-ACTIVATED C-H BONDS IN HYDROCARBONS AND STEROIDS
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CrO3 in CH2Cl2/CH3COOH/(CH3CO)2O oxidizes hydrocarbons to alcohols and ketones, 5α-androstane and 3β-acetoxy-5α-androstane are converted to 5α-androst-14-en-16-ones.
- Linz, T.,Schaefer, H. J.
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- Supported rhenium nanoparticle catalysts for acceptorless dehydrogenation of alcohols: Structure-activity relationship and mechanistic studies
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Al2O3-supported Re with different oxidation states and Re0 metal nanoparticles on various supports are prepared, characterized and tested for the dehydrogenation of 2-octanol. The activity of Re/Al2O3 increases with the fraction of metallic Re. The activity of metallic Re depends on the support oxides, and the support with moderate electronegativity (Al2O3) gives the highest turnover frequency (TOF) per surface Re0 site. Re/Al2O3 is effective for acceptorless dehydrogenation of various aliphatic secondary alcohols to ketones. The kinetic isotope effects on the dehydrogenation of 2-propanol show that dissociation of the α-C-H bond of 2-propanol is the rate-limiting step. The IR study of the reaction of gas phase 2-propanol over the Re/Al2O3 surface shows that the acid-base pair site of Al2O3 is responsible for the O-H dissociation of 2-propanol. The structural requirements are discussed on the basis of the mechanistic results.
- Kon, Kenichi,Onodera, Wataru,Toyao, Takashi,Shimizu, Ken-Ichi
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- Improved synthesis of 2-norbornanone
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Herein a two-step process for the synthesis of 2-norbornanone with 91 % overall yield has been developed. The addition of sublimation inhibitors suppressed the sublimation of norbornene in the process of sulfuric acid-promoted hydration and increased the yield of 2-norbornanol significantly under mild conditions. Additionally, reuse of sulfuric acid has been achieved. A 4-hydroxy-TEMPO/CuCl/TBN triple-component catalyst system for the highly selective aerobic oxidation of 2-norbornanol was developed and displayed high atom efficiency and yield.
- Zhang, Heng,Fu, Shuixiang,Tao, Ming,Liao, Zutai,Qian, Chao,Chen, Xinzhi
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- Catalytic alcohol oxidation using cationic Schiff base manganeseIII complexes with flexible diamino bridge
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Four Schiff base manganese(III) complexes with derivatives of [(R,R)-N,N’-bis(salicy1idene)-1,2-cyclohexanediaminato)] including substituents on salicylaldehyde such as 3-methoxy, 3,5-di-tert-butyl and 3,5-chloro were synthesized and characterized using a combination of IR, UV–Vis, and HR ESI-MS techniques. The catalytic activity of these complexes was tested in the oxidation of 1-phenylethanol to acetophenone, revealing very good performances for all of the four manganese complexes. The catalytic reactions were carried out in the presence of tert-butyl hydroperoxide (TBHP) as oxidant and imidazole as co-catalyst. Complex Mn-4, bearing electron withdrawing [(R,R)-N,N’-bis(3,5-di-chloro-salicylidene)-1,2-cyclohexanediaminato)] ligand was found to be the most stable of the tested Mn(III) complexes and was selected for the oxidation of several primary and secondary alcohols.
- Kakavand, Meysam,Mastrorilli, Piero,Mesto, Ernesto,Neshat, Abdollah,Osanlou, Farzane,Schingaro, Emanuela,Todisco, Stefano
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- Liquid-phase oxidation of olefins with rare hydronium ion salt of dinuclear dioxido-vanadium(V) complexes and comparative catalytic studies with analogous copper complexes
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Homogeneous liquid-phase oxidation of a number of aromatic and aliphatic olefins was examined using dinuclear anionic vanadium dioxido complexes [(VO2)2(salLH)]? (1) and [(VO2)2(NsalLH)]? (2) and dinuclear copper complexes [(CuCl)2(salLH)]? (3) and [(CuCl)2(NsalLH)]? (4) (reaction of carbohydrazide with salicylaldehyde and 4-diethylamino salicylaldehyde afforded Schiff-base ligands [salLH4] and [NsalLH4], respectively). Anionic vanadium and copper complexes 1, 2, 3, and 4 were isolated in the form of their hydronium ion salt, which is rare. The molecular structure of the hydronium ion salt of anionic dinuclear vanadium dioxido complex [(VO2)2(salLH)]? (1) was established through single-crystal X-ray analysis. The chemical and structural properties were studied using Fourier transform infrared (FT-IR), ultraviolet–visible (UV–Vis), 1H and 13C nuclear magnetic resonance (NMR), electrospray ionization mass spectrometry (ESI-MS), electron paramagnetic resonance (EPR) spectroscopy, and thermogravimetric analysis (TGA). In the presence of hydrogen peroxide, both dinuclear vanadium dioxido complexes were applied for the oxidation of a series of aromatic and aliphatic alkenes. High catalytic activity and efficiency were achieved using catalysts 1 and 2 in the oxidation of olefins. Alkenes with electron-donating groups make the oxidation processes easy. Thus, in general, aromatic olefins show better substrate conversion in comparison to the aliphatic olefins. Under optimized reaction conditions, both copper catalysts 3 and 4 fail to compete with the activity shown by their vanadium counterparts. Irrespective of olefins, metal (vanadium or copper) complexes of the ligand [salLH4] (I) show better substrate conversion(%) compared with the metal complexes of the ligand [NsalLH4] (II).
- Maurya, Abhishek,Haldar, Chanchal
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- A Structural View on the Stereospecificity of Plant Borneol-Type Dehydrogenases
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The development of sustainable processes for the valorization of byproducts and other waste streams remains an ongoing challenge in the field of catalysis. Racemic borneol, isoborneol and camphor are currently produced from α-pinene, a side product from the production of cellulose. The pure enantiomers of these monoterpenoids have numerous applications in cosmetics and act as reagents for asymmetric synthesis, making an enzymatic route for their separation into optically pure enantiomers a desirable goal. Known short-chain borneol-type dehydrogenases (BDHs) from plants and bacteria lack the required specificity, stability or activity for industrial utilization. Prompted by reports on the presence of pure (?)-borneol and (?)-camphor in essential oils from rosemary, we set out to investigate dehydrogenases from the genus Salvia and discovered a dehydrogenase with high specificity (E>120) and high specific activity (>0.02 U mg?1) for borneol and isoborneol. Compared to other specific dehydrogenases, the one reported here shows remarkably higher stability, which was exploited to obtain the first three-dimensional structure of an enantiospecific borneol-type short-chain dehydrogenase. This, together with docking studies, led to the identification of a hydrophobic pocket in the enzyme that plays a crucial role in the stereo discrimination of bornane-type monoterpenoids. The kinetic resolution of borneol and isoborneol can be easily integrated into the existing synthetic route from α-pinene to camphor thereby allowing the facile synthesis of optically pure monoterpenols from an abundant renewable source.
- Chánique, Andrea M.,Dimos, Nicole,Drienovská, Ivana,Calderini, Elia,Pantín, Mónica P.,Helmer, Carl P. O.,Hofer, Michael,Sieber, Volker,Parra, Loreto P.,Loll, Bernhard,Kourist, Robert
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p. 2262 - 2277
(2021/03/16)
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- Aerobic oxidation and oxidative esterification of alcohols through cooperative catalysis under metal-free conditions
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The ABNO@PMO-IL-Br material obtained by anchoring 9-azabicyclo[3.3.1]nonane-3-oneN-oxyl (keto-ABNO) within the mesopores of periodic mesoporous organosilica with bridged imidazolium groups is a robust bifunctional catalyst for the metal-free aerobic oxidation of numerous primary and secondary alcohols under oxygen balloon reaction conditions. The catalyst, furthermore, can be successfully employed in the first metal-free self-esterification of primary aliphatic alcohols affording valued esters.
- Karimi, Babak,Ghahremani, Mina,Vali, Hojatollah,Ciriminna, Rosaria,Pagliaro, Mario
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supporting information
p. 8897 - 8900
(2021/09/10)
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- Reduced Amino Acid Schiff Base-Iron(III) Complexes Catalyzing Oxidation of Cyclohexane with Hydrogen Peroxide
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The reduced amino acid Schiff base ligands have been prepared and were coordinated with ferric chloride to generate the iron(III) complexes. The ligands and complexes have been characterized using FT-IR, UV-vis, elemental analysis, ICP-AES analysis, mass spectra etc. After the structural characterization, these complexes were applied for the oxidation of cyclohexane using hydrogen peroxide as the oxidant under mild conditions. The activity tests showed that the L-phenylalanine-derived reduced Schiff base iron(III) complex(Ph?FeCl) afforded the highest yield of cyclohexanol and cyclohexanone(total yield up to 23.2 %). Notably, the Ph?FeCl complex catalyzes the reaction via a heterogeneous approach, allowing the complex to be separated and recycled conveniently after the oxidation reaction. Besides, the Ph?FeCl catalyst can also be extended for the selective oxidation of other alkanes and aromatics into alcohols, ketones and phenols etc. Finally, the reaction mechanism of cyclohexane oxidation on the iron(III) complex was proposed as well by the free radical inhibitors and EPR study of active intermediates.
- Zheng, Anna,Zhou, Qingqing,Ding, Bingjie,Li, Difan,Zhang, Tong,Hou, Zhenshan
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p. 3385 - 3395
(2021/08/23)
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- New Cu(II), Co(II) and Ni(II) azo-Schiff base complexes: Synthesis, characterization, catalytic oxidation of alkenes and DFT study
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Three new complexes with general formula of ML (M = Cu (1), Co (2), Ni (3)) containing an azo-Schiff base ligand (H2L) derived from 2,3-butanediamine and 4-(benzeneazo) salicylaldehyde were synthesized by template method. Characterization of the ligand and complexes were accomplished with FT-IR, UV–Vis, and 1H NMR. The catalytic activity of the complexes (1–3) were tested for the oxidation of various alkenes (cyclooctene, cyclohexene, styrene, α-methyl styrene, and norbornene) applying tert-butyl hydroperoxide (TBHP) as an oxidizing agent, and it was found that they were acceptable catalysts. Under the optimized reaction conditions, CuL complex displayed 94% conversion for the oxidation of cyclooctene, and CoL and NiL complexes exhibited 90 and 85% conversions for oxidizing α-methyl styrene, respectively. Based on our density functional computations, diffuse functions are compulsory in the basis set for geometry optimization of these systems. Therefore, the most stable structures and the vibrational frequencies were calculated at the M06-2X/6–311++G(d,p) level. By establishing the correlation between observed and calculated frequencies, the assignment of the vibrational modes was performed. Based on natural charge analysis (NAO), the back electron transfer from ML to the TBHP breaks the O–O bond and facilitates the formation of tert-butoxyl radicals.
- Lashanizadegan, Maryam,Asna Ashari, Hadiseh,Sarkheil, Marzieh,Anafcheh, Maryam,Jahangiry, Samira
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- A sustainable approach towards solventless organic oxidations catalyzed by polymer immobilized Nb(V)-peroxido compounds with H2O2 as oxidant
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New heterogeneous catalysts comprising of peroxidoniobium(V) complexes immobilized on amino acid grafted cross-linked poly(styrene-divinylbenzene) resin has been developed. Results of FTIR, Raman, NMR, XPS, XRD, EDX, SEM, BET, TGA, and elemental analysis confirmed the successful anchoring of triperoxidoniobium(V), [Nb(O2)3]? species to the host polymer via the pendant amino acid groups. The supported catalysts exhibited excellent performance in epoxidation of styrene and a range of cyclic and terpenic compounds under environmentally acceptable solvent-free condition, with aqueous H2O2 as oxidant. The catalytic protocols provided excellent conversion to the desired epoxide (up to 100%) with selectivity > 99%, TON as high as 1000, and high H2O2 utilization efficiency (92–97%). Moreover, the catalysts efficiently facilitated chemoselective solvent-free oxidation of a variety of thioethers to sulfones at room temperature. Simple operational strategy, easy recyclability for multiple reaction cycles with the consistent activity-selectivity profile are the additional significant attributes of the developed catalytic processes.
- Ahmed, Kabirun,Gogoi, Sandhya Rani,Islam, Nashreen S.,Saikia, Gangutri,Sultana, Sazida Yasmin,Talukdar, Hiya
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- Alcohol Oxidations by Schiff Base Manganese(III) Complexes
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Asymmetric Schiff base manganese(III) complexes involving salen ligands, N,N'-bis(salicylidene)2,3-diaminopyridine, N,N'-bis(3-methoxysalicylidene)2,3-diaminopyridine, N,N'-bis(3,5-di-tert-butylsalicylidene)2,3-diaminopyridine and N,N'-bis(3,5-di-chloro-salicylidene)2,3-diaminopyridine were prepared and their catalytic activity was investigated in the oxidation of some primary and secondary alcohols. During optimization of oxidation reactions, Mn-4, bearing electron withdrawing N,N'-Bis(3,5-di-chloro-salicylidene)2,3-diaminopyridine ligand, showed higher activity than other catalysts tested. The catalytic reactions were carried out in the presence of various oxidants such as oxygen, hydrogen peroxide or tert-butyl hydroperoxide (TBHP) and additives such as acetic acid and imidazole. The oxidant/additive combination of TBHP and imidazole was shown to be effective for the oxidation process and the degree of their impact on oxidation reaction was found highly dependent on a balanced ratio between them. Mn-4 was selected as the most effective catalyst under optimized reaction conditions and revealed efficient for the oxidation of secondary alcohols.
- Neshat, Abdollah,Kakavand, Meysam,Osanlou, Farzane,Mastrorilli, Piero,Schingaro, Emanuela,Mesto, Ernesto,Todisco, Stefano
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p. 480 - 490
(2020/02/05)
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- Homogeneous catalytic oxidation of alkenes employing mononuclear vanadium complex with hydrogen peroxide
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Abstract: Homogeneous liquid-phase oxidation of alkenes (allylbenzene, cis-cyclooctene, 4-chlorostyrene, styrene, 2-norbornene, 1-methyl cyclohexene, indene, lemonine, and 1-hexene) were catalyzed by using vanadium complex [VO(hyap)(acac)2] in existence of H2O2. The complex [VO(hyap)(acac)2] was formed as a crystal by the reaction of [VO(acac)2] and 2-hydroxyacetophenone (hyap) in the presence of methanol by refluxing the reaction mixture. Various analytical and spectroscopic techniques, namely FTIR, ESI–MS, UV–Vis, single-crystal XRD, and EPR, were used to analyze and optimize the structure of the complexes. Graphic abstract: [Figure not available: see fulltext.].
- Maurya, Abhishek
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p. 3261 - 3269
(2020/07/14)
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- Oxidation of Alkenes by Water with H2 Liberation
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Oxidation by water with H2 liberation is highly desirable, as it can serve as an environmentally friendly way for the oxidation of organic compounds. Herein, we report the oxidation of alkenes with water as the oxidant by using a catalyst combination of a dearomatized acridine-based PNP-Ru complex and indium(III) triflate. Compared to traditional Wacker-type oxidation, this transformation avoids the use of added chemical oxidants and liberates hydrogen gas as the only byproduct.
- Ben-David, Yehoshoa,Milstein, David,Tang, Shan
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supporting information
p. 5980 - 5984
(2020/04/27)
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- Ionic liquid-stabilized vanadium oxo-clusters catalyzing alkane oxidation by regulating oligovanadates
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Alkane oxidation under mild conditions occupies an important position in the chemical industry. Herein, we have designed a novel class of ionic liquid ([TBA][Pic])-stabilized vanadium oxo-clusters (TBA = tetrabutylammonium; Pic = picolinate ions), in which the molar ratio of the IL to V atoms can be tuned facilely to obtain V-OC?IL-0.5, V-OC?IL-1 and V-OC?IL-2, respectively. The as-synthesized vanadium oxo-clusters have been characterized by elemental analysis, FT-IR, UV-vis, XRD, TGA, EPR, NMR and MS. These vanadium oxo-clusters were catalytically active for catalyzing the oxidation of cyclohexane with H2O2 as an oxidant. In particular, the oxo-cluster V-OC?IL-1 (where IL/V is 1.0) can provide an approximately 30% total yield of KA oil (cyclohexanol and cyclohexanone) without adding any co-catalyst at 50 °C within 1.0 h. Moreover, the present vanadium oxo-cluster was recyclable owing to the modification of the IL and it can also be extended to the oxidation of the sp2 hybrid aromatic ring. The further characterization results demonstrated that the oligovanadate anions were strongly dependent on the molar ratio of the IL to V atoms. The vanadium oxo-clusters with the appropriate molar ratio of IL/V could exist in the form of a trimer and a dimer due to the presence of the TBA cation and the coordination of picolinate. Notably, the oligovanadate anions are highly active species for the C-H oxidation but the mononuclear vanadate afforded a very poor activity according to the activity assessment and the identification of vanadium species from the 51V NMR spectra and MS spectra. The annihilation reaction of free radicals and EPR characterization suggested that the vanadium oxo-clusters operated via a mechanism of the HO radical in the oxidation reaction.
- Ding, Bingjie,Gong, Xueqing,Hou, Zhenshan,Li, Difan,Yao, Yefeng,Zhang, Ran,Zheng, Anna,Zhou, Qingqing
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p. 7601 - 7612
(2020/11/27)
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- Polymer immobilized tantalum(v)-amino acid complexes as selective and recyclable heterogeneous catalysts for oxidation of olefins and sulfides with aqueous H2O2
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Polymer supported heterogeneous peroxotantalum(v) catalysts were prepared by anchoring Ta(v)-diperoxo species to chloromethylated poly(styrene-divinylbenzene) resin functionalized with amino acids asparagine (l-Asn) and arginine (l-Arg). The structurally well-defined catalysts, [Ta(O2)2(L)2]--MR, [L = asparagine (catalyst 1) or arginine (catalyst 2) and MR = Merrifield resin], were comprehensively characterized by elemental analysis (CHN, ICP-OES, energy dispersive X-ray spectroscopy), spectral studies (FT-IR, Raman, 13C NMR, diffuse reflectance UV-vis and XPS), SEM, XRD, Brunauer-Emmett-Teller (BET) and thermogravimetric analysis (TGA). The supported peroxotantalum (pTa) compounds displayed excellent catalytic performance in epoxidation of alkenes with 30% H2O2, under solvent free reaction conditions. Styrene was epoxidized with >99% selectivity with the highest TOF of 1040 h-1 obtained within 30 min reaction time, whereas the TOF for norbornene epoxidation was 2000 h-1 within 1 h with >95% epoxide selectivity. Furthermore, the immobilized catalysts facilitated chemoselective oxidation of a broad range of organic sulfides to the desired sulfoxides with H2O2 in methanol, under mild reaction conditions. The oxidations proceeded with a high H2O2 efficiency percentage and are amenable to ready scalability. The heterogeneous catalysts could be easily recovered and reused for several consecutive catalytic cycles with undiminished activity/selectivity profiles in all cases. The developed catalytic strategies are operationally simple and, being free from halogenated solvent or any other toxic auxiliaries, environmentally clean.
- Saikia, Gangutri,Ahmed, Kabirun,Rajkhowa, Chandrasee,Sharma, Mitu,Talukdar, Hiya,Islam, Nashreen S.
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supporting information
p. 17251 - 17266
(2019/11/20)
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- Epoxidation of Cyclooctene Using Water as the Oxygen Atom Source at Manganese Oxide Electrocatalysts
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Epoxides are useful intermediates for the manufacture of a diverse set of chemical products. Current routes of olefin epoxidation either involve hazardous reagents or generate stoichiometric side products, leading to challenges in separation and significant waste streams. Here, we demonstrate a sustainable and safe route to epoxidize olefin substrates using water as the oxygen atom source at room temperature and ambient pressure. Manganese oxide nanoparticles (NPs) are shown to catalyze cyclooctene epoxidation with Faradaic efficiencies above 30%. Isotopic studies and detailed product analysis reveal an overall reaction in which water and cyclooctene are converted to cyclooctene oxide and hydrogen. Electrokinetic studies provide insights into the mechanism of olefin epoxidation, including an approximate first-order dependence on the substrate and water and a rate-determining step which involves the first electron transfer. We demonstrate that this new route can also achieve a cyclooctene conversion of ～50% over 4 h.
- Jin, Kyoungsuk,Maalouf, Joseph H.,Lazouski, Nikifar,Corbin, Nathan,Yang, Dengtao,Manthiram, Karthish
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supporting information
p. 6413 - 6418
(2019/05/02)
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- Chemoselective Continuous Ru-Catalyzed Hydrogen-Transfer Oppenauer-Type Oxidation of Secondary Alcohols
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A continuous flow method for the selective oxidation of secondary alcohols is reported. The method is based on an Oppenauer-type ruthenium-catalyzed hydrogen-transfer process that uses acetone as both solvent and oxidant. The process utilizes a low loading (1 mol%) of the commercially available ruthenium catalyst [Ru(p-cymene)Cl2]2 and triethylamine as a base and can be successfully applied to a range of different substrates, with a good level of functional group tolerance.
- Labes, Ricardo,Battilocchio, Claudio,Mateos, Carlos,Cumming, Graham R.,De Frutos, Oscar,Rincón, Juan A.,Binder, Kellie,Ley, Steven V.
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supporting information
p. 1419 - 1422
(2017/09/23)
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- Discovery of dual Axl/VEGF-R2 inhibitors as potential anti-angiogenic and anti-metastatic drugs for cancer chemotherapy
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Axl tyrosine kinase has been shown to be involved in multiple pathways contributing to tumor development, angiogenesis, and metastasis. High Axl expression has been observed in many human tumors where it appears to confer aggressive tumor behavior. Here we present several series of dual Axl-VEGF-R2 kinase inhibitors based on extensive optimization of an acyl diaminotriazole. It was hypothesized that dual inhibition of these two receptor tyrosine kinases may have a synergistic affect in inhibiting tumor angiogenesis and metastasis. One of these molecules, R916562 showed comparable activity to Sunitinib in two mouse tumor xenograft models and a mouse corneal micropocket model.
- Goff, Dane,Zhang, Jing,Heckrodt, Thilo,Yu, Jiaxin,Ding, Pingyu,Singh, Raj,Holland, Sacha,Li, Weiqun,Irving, Mark
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p. 3766 - 3771
(2017/07/27)
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- Reductive activation of O2 by a bioinspired Fe complex for catalytic epoxidation reactions
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Aerobic epoxidation of olefins catalyzed by iron complexes without the use of a sacrificial coreductant is unknown. We report the reductive activation of O2 by a bioinspired [(bTAML)FeIII(H2O)]- (1) complex to catalyze the epoxidation of alkenes with TONs of up to 80. Spectroscopic and kinetic evidence indicates the involvement of FeV(O) as the active oxidant during the reaction.
- Singh, Kundan K.,Gupta, Sayam Sen
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supporting information
p. 5914 - 5917
(2017/07/11)
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- Nonheme iron complex-catalyzed efficient alcohol oxidation by t-BuOOH with N-hydroxyphthalimide (NHPI) as co-catalyst: Implication of high valent iron-oxo species
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Two iron catalysts ([Fe(bpc)Cl2][Et4N] (1a) and [Fe(Me2bpb)Cl2][Et3NH] (1b)) displayed efficient catalysis in oxidation of various alcohols to the corresponding carbonyl products using t-BuOOH as an oxidant in the presence of N-hydroxyphthalimide (NHPI) under mild conditions. 1a having an electron-withdrawing group showed a little better catalytic activity than that of 1b with an electron-donating group. The mechanistic studies through Hammett plot, deuterium isotope effect, and the use of 2-methyl-1-phenylprop-2-yl hydroperoxide (MPPH) as a mechanistic probe suggested that the reactive oxidants responsible for the alcohol oxidation possibly involved FeIV[Formula presented]), and phthalimide N-oxyl radical [Formula presented]. On the other hand, the presence of imidazole increased the heterolytic cleavage of Fe-OOR intermediate to form FeV[Formula presented] species and accelerated its [Formula presented] bond cleavage rate. In particular, the formation of FeV[Formula presented] intermediate via the heterolytic cleavage of Fe-OOR species in the presence of imidazole in the catalytic oxidation systems of nonheme iron complexes with t-BuOOH was substantialized, for the first time, to the best of our knowledge.
- Bae, Jeong Mi,Lee, Myoung Mi,Lee, Seul Ah,Lee, Sun Young,Bok, Kwon Hee,Kim, Jinheung,Kim, Cheal
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- Efficient epoxide isomerization within a self-assembled hexameric organic capsule
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The isomerization of epoxides to the corresponding carbonyl compounds is efficiently catalyzed by the supramolecular organic nano-capsule formed by the self-assembly of six resorcin[4]arene units. The capsule provides a combination of weak Br?nsted acidity and a suitable nano-environment that favors the metal-free isomerization reaction.
- Caneva, Thomas,Sperni, Laura,Strukul, Giorgio,Scarso, Alessandro
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p. 83505 - 83509
(2016/11/01)
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- Synergistic catalysis within TEMPO-functionalized periodic mesoporous organosilica with bridge imidazolium groups in the aerobic oxidation of alcohols
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Anchoring 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO) within the nanospaces of a periodic mesoporous organosilica with bridged imidazolium groups led to an unprecedented powerful bifunctional catalyst (TEMPO@PMO-IL-Br), which showed enhanced activity in the metal-free aerobic oxidation of alcohols. The catalyst and its precursors were characterized by N2 adsorption-desorption analysis, transmission electron microscopy (TEM), small angle X-ray scattering (SAXS), thermal gravimetric analysis (TGA), diffuse reflectance infrared Fourier transform spectroscopy (DRIFT), solid state electron paramagnetic resonance (EPR) spectroscopy, elemental analysis, transmission electron microscopy (TEM) and high resolution TEM. It was clearly found that the catalytic activity of SBA-15-functionalized TEMPO (TEMPO@SBA-15) not bearing IL, TEMPO@PMO-IL-Cl, PMO-IL-AMP, or individual catalytic functionalities (PMO-IL/TEMPO@SBA-15) was inferior as compared with those obtained from TEMPO@PMO-IL-Br in the metal-free aerobic oxidation of benzyl alcohol, suggesting the critical role of co-supported TEMPO and imidazolium bromide in obtaining high catalytic activity in the described catalyst system. Our observation clearly points to the fact that the combination of imidazolium bromide units in close proximity to TEMPO moieties in the nanospaces of TEMPO@PMO-IL-Br might be indeed one of the key factors explaining the enhanced catalytic activity observed for this catalyst in the oxidation of benzyl alcohol, possibly through a synergistic catalysis relay pathway. A proposed model was suggested for the observed synergistic effect.
- Karimi, Babak,Vahdati, Saleh,Vali, Hojatollah
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p. 63717 - 63723
(2016/07/19)
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- Visible light induced oxygenation of alkenes with water sensitized by silicon-porphyrins with the second most earth-abundant element
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Silicon as the second most abundant element on Earth was effectively utilized as the central atom in the porphyrin to induce photochemical oxygenation of alkenes as the first example of photocatalytic reaction through activation of water molecule in the presence of K2PtCl6 as an electron acceptor. Oxygen atom of water was confirmed to be incorporated in the oxygenated product by the photoreaction with H218O. The excited triplet state of silicon porphyrin was revealed to be responsible for the photochemical oxygenation. The one-electron oxidized silicon porphyrin was predicted by DFT calculation to have its spin population mostly on the axially ligated hydroxyl oxygen atom. The oxyl radical character of the axial ligand could rationalize the oxygenation reaction.
- Remello, Sebastian Nybin,Hirano, Takehiro,Kuttassery, Fazalurahman,Nabetani, Yu,Yamamoto, Daisuke,Onuki, Satomi,Tachibana, Hiroshi,Inoue, Haruo
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p. 176 - 183
(2015/10/28)
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- Catalysis and molecular magnetism of dinuclear iron(iii) complexes with N-(2-pyridylmethyl)-iminodiethanol/-ate
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The reaction of N-(2-pyridylmethyl)iminodiethanol (H2pmide) and Fe(NO3)3·9H2O in MeOH led to the formation of a dimeric iron(iii) complex, [(Hpmide)Fe(NO3)] 2(NO3)2·2CH3OH (1). Its anion-exchanged form, [(pmide)Fe(N3)]2 (2), was prepared by the reaction of 1 and NaN3 in MeOH, during which the Hpmide ligand of 1 was also deprotonated. These compounds were investigated by single crystal X-ray diffraction and magnetochemistry. In complex 1, one iron(iii) ion was bonded with a mono-deprotonated Hpmide ligand and a nitrate ion. The two iron(iii) ions within the dinuclear unit were connected by two ethoxy groups with an inversion center. In 2, one iron(iii) ion was coordinated with a deprotonated pmide ligand and an azide ion. The Fe(pmide)(N3) unit was related by symmetry through an inversion center. Both 1 and 2 efficiently catalyzed the oxidation of a variety of alcohols under mild conditions. The oxidation mechanism was proposed to involve an FeIVO intermediate as the major reactive species and an FeVO intermediate as a minor oxidant. Evidence for this proposal was derived from reactivity and Hammett studies, KIE (kH/kD) values, and the use of MPPH (2-methyl-1-phenylprop-2-yl hydroperoxide) as a mechanistic probe. Both compounds had significant antiferromagnetic interactions between the iron(iii) ions via the oxygen atoms. 1 showed a strong antiferromagnetic interaction within the Fe(iii) dimer, while 2 had a weak antiferromagnetic coupling within the Fe(iii) dimer.
- Shin, Jong Won,Bae, Jeong Mi,Kim, Cheal,Min, Kil Sik
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p. 3999 - 4008
(2014/03/21)
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- Norbornanoid chiral ketones by desymmetrization of dibromoalkenes
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New optically active polycyclic ketones 6a-6d, amenable to a large variety of synthetic applications, have been prepared from readily available 2,3-dibromonorbornene and analogs (Scheme 2) via desymmetrization with (-)-ephedrine, followed by hydrolysis under mild acidic conditions. At variance with substrates 4a-4d, the sterically hindered norbornene derivative 4e reacts with the solvent N-methylpyrrolidin-2-one (NMP) leading to the formation of the unusual cyclopropanoid products 8a and 8b. Copyright
- Ko?ak, Ramazan,Borsato, Giuseppe,De Lucchi, Ottorino,Da?tan, Arif
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p. 537 - 545
(2014/05/06)
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- Heterogeneous cobalt catalysts for the acceptorless dehydrogenation of alcohols
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A series of transition metal(M)-loaded TiO2 catalysts (M/TiO2) and Co-loaded catalysts on various support materials were prepared by an impregnation method, followed by in situ H2-reduction at 400 °C, and tested for the acceptor-free oxidation of cyclododecanol in the liquid phase. Among the catalysts including noble metal catalysts, Co/TiO2 showed the highest activity. In the presence of Co/TiO 2 (0.1-3 mol%) the dehydrogenation of various aliphatic secondary alcohols proceeded to afford the corresponding ketones. The catalyst was recoverable and was reused after the H2-reduction treatment. Based on the spectroscopic characterization of the catalyst combined with the studies on the effect of the Co oxidation states on the catalytic activity, it is clarified that the surface metallic Co sites with electron deficiency are the catalytically active species.
- Shimizu, Ken-Ichi,Kon, Kenichi,Seto, Mayumi,Shimura, Katsuya,Yamazaki, Hiroshi,Kondo, Junko N.
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p. 418 - 424
(2013/03/29)
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- Acceptor-free dehydrogenation of secondary alcohols by heterogeneous cooperative catalysis between Ni nanoparticles and acid-base sites of alumina supports
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Nickel-nanoparticle-loaded θ-Al2O3 (Ni/θ-Al2O3), prepared by H2-reduction of NiO/θ-Al2O3, acts as an effective and reusable heterogeneous catalyst for acceptor-free dehydrogenation of alcohols in a liquid phase. Among various supports, amphoteric supports (such as θ-Al 2O3), having both acidic and basic sites, gave higher activity than acidic or basic supports. Among Ni/θ-Al2O 3 catalysts with different Ni particle sizes, turnover frequency (TOF) per surface Ni increases with decreasing Ni particle size. These results suggest that low-coordinated Ni0 sites and metal/support interfaces play important roles in the catalytic cycle. The reaction mechanism is investigated by in situ IR study combined with kinetic analysis (kinetic isotope effect), and the following mechanism is proposed: (1) reaction of an alcohol with Lewis acid (Alδ+)-base (AlOδ-) pair site of alumina yields an alkoxide on the Alδ+ site and a proton on the AlOδ- site, (2) CH dissociation of the alkoxide by Ni 0 site to form NiH and a ketone, and (3) protolysis of NiH by a neighboring proton to release H2 gas. The proposed mechanism provides fundamental reasons for the higher activity of Ni on the acid-base bifunctional support (Al2O3) than on basic and acidic ones.
- Shimizu, Ken-Ichi,Kon, Kenichi,Shimura, Katsuya,Hakim, Siddiki S.M.A.
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p. 242 - 250
(2013/04/10)
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- Chemoselective oxidation by electronically tuned nitroxyl radical catalysts
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Electronic tuning: Nitroxyl radical 1 is shown to be an efficient catalyst for the oxidation of secondary alcohols, and promotes oxidation through an oxoammonium species which is highly reactive because of the adjacent electron-withdrawing ester groups. Chemoselective oxidation of benzylic alcohols in the presence of aliphatic alcohols is observed and is proposed to proceed by a rate-determining hydride transfer. Copyright
- Hamada, Shohei,Furuta, Takumi,Wada, Yoshiyuki,Kawabata, Takeo
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supporting information
p. 8093 - 8097
(2013/08/23)
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- NICOTINIC RECEPTOR TARGETED COMPOUNDS AND COMPOSITIONS
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The invention relates to the design and synthesis of novel anabaseine-based compounds, which are useful in treating or preventing a wide variety of conditions, including nervous system diseases or disorders, such as, schizophrenia, Alzheimer's disease, Parkinson's disease, drug dependence, and substance addiction, and compositions, kits, and methods thereof. The invention also provides novel anabaseine-based compounds, compositions, kits, and methods thereof for treating or preventing non-nerve system diseases or disorders (such as, inflammation and cancer) in a subject identified in need thereof. Certain enantiomeric compounds of the invention exhibited enhanced selectivity toward α7 nAChRs relative to alpha4beta2 nAChRs. Other enantiomeric compounds of the invention exhibited enhanced selectivity for alpha4beta2 nAChRs relative to α7 nAChRs.
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Page/Page column 60
(2013/07/05)
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- Total synthesis of (-)-isoschizogamine
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A first asymmetric total synthesis of (-)-isoschizogamine has been accomplished. Our synthesis features the facile construction of the carbon framework of the natural product through a Wagner-Meerwein rearrangement, a tandem metathesis, a stereoselective rhodium-mediated 1,4-addition of an arylboronic acid, and a ring-closing metathesis via a hemiaminal ether.
- Miura, Yusuke,Hayashi, Noriyuki,Yokoshima, Satoshi,Fukuyama, Tohru
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supporting information; experimental part
p. 11995 - 11997
(2012/09/08)
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- Cyclohexylamine oxidase as a useful biocatalyst for the kinetic resolution and dereacemization of amines
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The biocatalytic performance of a cloned cyclohexylamine oxidase derived from Brevibacterium oxydans IH-35A towards structurally different amines was investigated. Cycloalkyl primary amines, alkyl aryl amines, and α-carbon-substituted aliphatic amines were identified as suitable substrates for the biocatalyst based on an activity assay. Kinetic resolutions of several amines by either recombinant whole cells or crude enzyme extracts prepared therefrom gave enantiomerically pure (R)-amines besides the corresponding ketones. When cyclohexylamine oxidase in combination with a borane-ammonia complex as reducing agent was applied to the deracemization of several substrates, excellent enantiomeric ratios (>99:1) and good isolated yields (62%-75%) of the corresponding (R)-amines were obtained.
- Leisch, Hannes,Grosse, Stephan,Iwaki, Hiroaki,Hasegawa, Yoshie,Lau, Peter C.K.
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experimental part
p. 39 - 45
(2012/03/07)
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- Bromine-catalyzed aerobic oxidation of alcohols
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We have demonstrated that a simple and environmentally benign catalytic system HBr/NaNO2 is very effective for the selective oxidation of alcohols under balloon pressure of O2. Furthermore, the aerobic oxidation of alcohols has been achieved under balloon pressure of air rather that pure O2, with this HBr/NaNO2/HNO3 catalytic system. (Chemical equation presented).
- Uyanik, Muhammet,Fukatsu, Ryota,Ishihara, Kazuaki
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supporting information; experimental part
p. 456 - 460
(2010/08/20)
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- Stereoselective cyclotrimerization of enantiopure iodonorbornenes catalyzed by Pd nanoclusters for C 3 or C 3 v symmetric syntris(norborneno)benzenes
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(Figure presented) C3 or C3v symmetric enantiopure syn-tris(norborneno)benzenes with various functional groups were synthesized through Pd-catalyzed cyclotrimerization of enantiopure iodonorbornenes. The generality of Pd-catalyzed cyclotrimerization for syn-tris(norborneno)benzenes were well-demonstrated.
- Higashibayashi, Shuhei,Masud Reza,Sakurai, Hidehiro
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supporting information; experimental part
p. 4626 - 4628
(2010/09/18)
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- Homogeneous green catalysts for olefin oxidation by mono oxovanadium(V) complexes of hydrazone Schiff base ligands
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Three mono oxovanadium(V) complexes of tridentate Schiff base ligands [VO(OMe)L'] (1), [VO(OMe)L2] (2) and [VO(OMe)L3] (3) obtained by monocondensation of 3-hydroxy-2-naphthohydrazide and aromatic o-hydroxyaldehydes have been synthesized (H2L2 - (E)-3-hydroxy-N′-(2-hydroxy-3-methoxybenzylidene)-2-naphthohydrazide, H2L2 - (E)-3-hydroxy-N′-(2-hydroxybenzylidene)-2- naphthohydrazide and H2L3 - (E)-N′-(5-bromo-2- hydroxybenzylidene)-3-hydroxy-2-naphthohydrazide). The complexes were characterized by spectroscopic methods in the solid state (IR) and in solution (UV-Vis, 1H NMR). Single crystal X-ray analyses were performed with 1 and 2. The catalytic potential of these complexes has been tested for the oxidation of cyclooctene using H2O2 as the terminal oxidant. The effects of various parameters including the molar ratio of oxidant to substrate, the temperature, and the solvent have been studied. The catalyst 2 showed the most powerful catalytic activity in oxidation of various terminal, cyclic and phenyl substituted olefins. Excellent conversions have been obtained for the oxidation of cyclic and bicyclic olefins.
- Monfared, Hassan Hosseini,Bikas, Rahman,Mayer, Peter
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experimental part
p. 2574 - 2583
(2011/02/17)
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- Novel polyaniline supported cobalt catalyzed aerobic oxidation of unsaturated organic compounds
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The oxidation of organic compounds with carbon-carbon double bond with molecular oxygen under atmospheric pressure in the presence of new polyaniline supported catalyst 1 has been studied. This catalyst turned out to be efficient and selective for oxidation of some unsaturated organic compounds. Oxidation of alkenes, cycloalkenes and terpenes give corresponding epoxy derivatives, whereas organic compounds with carbon carbon double bond in benzylic position give ketones as a main product. Taylor & Francis Group, LLC.
- Pielichowski, Jan,Kowalski, Grzegorz
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experimental part
p. 105 - 111
(2011/08/03)
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- Reactions of halonorbornane and oxo-substituted derivatives with different anions by the electron transfer mechanism; Redox catalysis in stabilized radicals
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Reactions of 2-bromo-, 2-chloronorbornane, 3-chloronorbornan-2-one and 3-bromocamphor with Me3Sn-, Ph2P- or PhS- ions were studied by an SRN1 mechanism in liquid ammonia or DMSO. The results show that substrates having a carbonyl group facilitate electron transfer reactions, which are impeded in the absence of such a group. However, when the free radical formed is stabilized by conjugation, the coupling reaction decreases, causing a concomitant increase in the reduction product. Theoretical studies explain the observed reactivity on the basis of a mechanism involving reductive cleavage as a function of the π-σ interactions.
- Uranga, Jorge G.,Santiago, Ana N.
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scheme or table
p. 2006 - 2012
(2011/01/10)
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- Development of safe and scalable continuous-flow methods for palladium-catalyzed aerobic oxidation reactions
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The synthetic scope and utility of Pd-catalyzed aerobic oxidation reactions has advanced significantly over the past decade, and these reactions have the potential to address important green-chemistry challenges in the pharmaceutical industry. This potential has not been realized, however, because safety concerns and process constraints hinder large-scale applications of this chemistry. These limitations are addressed by the development of a continuous-flow tube reactor, which has been demonstrated on several scales in the aerobic oxidation of alcohols. Use of a dilute oxygen gas source (8% O2 in N 2) ensures that the oxygen/organic mixture never enters the explosive regime, and efficient gas-liquid mixing in the reactor minimizes decomposition of the homogeneous catalyst into inactive Pd metal. These results provide the basis for large-scale implementation of palladium-catalyzed (and other) aerobic oxidation reactions for pharmaceutical synthesis. The Royal Society of Chemistry 2010.
- Ye, Xuan,Johnson, Martin D.,Diao, Tianning,Yates, Matthew H.,Stahl, Shannon S.
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supporting information; experimental part
p. 1180 - 1186
(2010/10/20)
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- Photocatalytic aerobic epoxidation of alkenes under visible light irradiation by an iron(III) porphyrin with Mg-Al hydrotalcite anionic clay
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In photocatalytic aerobic oxidation of cyclohexene catalyzed by 5, 10, 15, 20-tetrakis(pentafluorophenyl)porphyriniron(III) chloride [Fe(TPFPP)Cl] under visible light irradiation, the coexistence of solid bases was found to enhance the selectivity to cyclohexene oxide drastically. In the absence of solid bases, however, only the allylic oxidation of cyclohexene was catalyzed by the porphyrin complex acting as a sensitizer. Among the various metal oxides investigated, hydrotalcite exhibited the highest conversion of cyclohexene and selectivity to cyclohexene oxide. Copyright
- Teramura, Kentaro,Ogura, Kentaro,Sugimoto, Takashi,Tsuneoka, Hideo,Shishido, Tetsuya,Tanaka, Tsunehiro
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scheme or table
p. 1098 - 1099
(2010/06/12)
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- Efficient aerobic oxidation of alcohols using a hydrotalcitesupported gold nanoparticle catalyst
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Hydrotalcite-supported gold nanoparticles (Au/HT) were found to be a highly efficient heterogeneous catalyst for the aerobic oxidation of alcohols under mild reaction conditions (4O°C, in air). This catalyst system does not require any additives and is applicable to a wide range of alcohols, including less reactive cyclohexanol derivatives. This Au/HT catalyst could also function in the oxidation of 1-phenylethanol under neat conditions; the turnover number (TON) and turnover frequency (TOF) reached 200,000 and 8,300 h -1, respectively. These values are among the highest values compared to those of other reported catalyst systems at high conversion. Moreover, the Au/HT can be recovered by simple filtration and reused without any loss of its activity and selectivity.
- Mitsudome, Takato,Noujima, Akifumi,Mizugaki, Tomoo,Jitsukawa, Koichiro,Kaneda, Kiyotomi
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scheme or table
p. 1890 - 1896
(2011/03/18)
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- SUBSTITUTED TRIAZOLES USEFUL AS AXL INHIBITORS
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Substituted triazoles and pharmaceutical compositions containing the compounds are disclosed as being useful in inhibiting the activity of the receptor protein tyrosine kinase Axl. Methods of using the compounds in treating diseases or conditions associated with Axl activity are also disclosed.
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Page/Page column 147
(2008/12/07)
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- Copper nanoparticles on hydrotalcite as a heterogeneous catalyst for oxidant-free dehydrogenation of alcohols
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We have developed a highly efficient heterogeneous catalytic system using hydrotalcite-supported Cu nanoparticles (Cu/HT) that can successfully promote the oxidant-free dehydrogenation of various alcohols under liquid-phase conditions. The Royal Society of Chemistry.
- Mitsudome, Takato,Mikami, Yusuke,Ebata, Kaori,Mizugaki, Tomoo,Jitsukawa, Koichiro,Kaneda, Kiyotomi
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supporting information; experimental part
p. 4804 - 4806
(2009/03/12)
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- Oxidation of alcohols with molecular oxygen promoted by Nafion ionomer anchored pyrochlore composite at room temperature
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Nafion ionomer anchored ruthenium oxide pyrochlore composite has been demonstrated for selective oxidation of alcohols to aldehydes and ketones in good yields. In the absence of any additives, the reaction was achieved by atmospheric air or molecular oxygen at room temperature.
- Venkatesan,Kumar, A. Senthil,Zen
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p. 4339 - 4341
(2008/12/21)
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- A simple protocol for the generation of methyl(trifluoromethyl)dioxirane
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Methyl(trifluoromethyl)dioxirane, generated from an aqueous solution of 1,1,1-trifluoroacetone hydrate, sodium bicarbonate and peroxomonosulfate, is removed from the reaction mixture by the evolved gases and applied to the oxidation of substrates placed in a second reaction zone. The method is simple and robust, and allows for the application of methyl(trifluoromethyl)dioxirane in oxidation reactions on a preparative scale. Georg Thieme Verlag Stuttgart.
- Mello, Rossella,González-Nú?ez, Maria Elena,Asensio, Gregorio
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- Synthesis and thermal decomposition of hydrotrioxide obtained by ozonization of exo-bicyclo[2.2.1]heptan-2-ol
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Low-temperature (-70 °C) ozonization of exo-bicyclo[2.2.1]heptan-2-ol in CCl3F led to a hydrotrioxide, which was identified by 1H NMR spectroscopy. Kinetics of decomposition of given hydrotrioxide was studied by analysis of the chemiluminescence fading in the IR range of the spectrum and the activation parameters of the process were calculated. Singlet oxygen (1Δg) served as an emitter of eradiation. Yields of 1O2 in a range of temperature from -31.0 to +12.5 °C were determined (at -31 °C the yield was 37.6%). Bicyclo[2.2.1]heptan-2-one was found to be the main product of decomposition of the hydrotrioxide (the yield was 98%).
- Abdrakhmanova,Khalitova,Spirikhin,Dokichev,Grabovskiy,Kabal'nova
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p. 271 - 275
(2008/03/12)
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- Oppenauer oxidation of secondary alcohols with 1,1,1-trifluoroacetone as hydride acceptor
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(Chemical Equation Presented) 1,1,1-Trifluoroacetone (2a) reacts as a hydride-acceptor in the Oppenauer oxidation of secondary alcohols (1) in the presence of diethylethoxyaluminum. The oxidant allows for selective oxidation of secondary alcohols in the presence of primary alcohols.
- Mello, Rossella,Martinez-Ferrer, Jaime,Asensio, Gregorio,Gonzalez-Nunez, Maria Elena
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p. 9376 - 9378
(2008/03/13)
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- Expeditious oxidation of alcohols to carbonyl compounds using iron(III) nitrate
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An efficient and solvent-free protocol for the oxidation of alcohols to corresponding carbonyl compounds using iron(III) nitrate nonahydrate has been developed.
- Namboodiri, Vasudevan V.,Polshettiwar, Vivek,Varma, Rajender S.
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p. 8839 - 8842
(2008/03/18)
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- Efficient and convenient procedure for protection of hydroxyl groups to the THP, THF and TMS ethers and oxidation of these ethers to their aldehydes or ketones in [BPy]FeCl4 as a low cost room temperature ionic liquid
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Alcohols were converted to the corresponding THP, THF or TMS ethers in high to excellent yields in 1-n-butylpyridinium chloroferrate media as a stable and low cost room temperature ionic liquid. In addition, oxidation of these ethers to their aldehydes or ketones without any overoxidation reactions in this ionic liquid was also performed.
- Khosropour, Ahmad R.,Khodaei, Mohammad M.,Ghaderi, Sattar
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p. 326 - 330
(2007/10/03)
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- Oxidation of alcohols to carbonyl compounds with CrO3· SiO2 in supercritical carbon dioxide
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Supercritical carbon dioxide (scCO2) is an effective reaction medium to perform the oxidation of primary and secondary aliphatic alcohols to the corresponding carbonyl compounds with chromium trioxide supported on silica. These reactions were performed by flowing a solution of the alcohol in scCO2 through a column containing the supported reagent and recovering the product by depressurization. This method avoids the use of organic solvents and the contamination of the products with chromium species.
- Gonzalez-Nunez, Maria Elena,Mello, Rossella,Olmos, Andrea,Accrete, Rafael,Asensio, Gregorio
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p. 1039 - 1042
(2007/10/03)
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- 2-Chlorobicyclo[2.2.1]hept-5-ene-2-carboxamide and 2-chlorobicyclo[2.2.1] heptane-2-carboxamide as precursors of bicyclo[2.2.1]hept-5-en-2-one and bicyclo[2.2.1]heptan-2-one: Resolution, absolute configuration and hydrogen-bonding properties
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The absolute configuration of bicyclo[2.2.1]heptan-2-one has not been correlated with a crystal structure of a chemical precursor. The only chemical correlation available had an ambiguity, which could have reversed the assignment. Herein, we report the resolution of 2-chlorobicyclo[2.2.1]hept-5-en- 2-exo-carboxamide on a cellulose triacetate column and the crystal structures of the enantiomerically pure and racemic α-chloroamide. We found the absolute configuration (1R,2R,4R) for the (+)-enantiomer of the α-chloroamide. This compound was converted to (+)-bicyclo[2.2.1]hept-5- ene-2-one by base hydrolysis, and the 5,6-unsaturated compounds converted to the saturated congeners. This is the first unambiguous experimental determination of the absolute configuration of bicyclo[2.2.1]heptan-2-one and of bicyclo[2.2.1]hept-5-ene-2-one. The three crystal structures of 2-chlorobicyclo[2.2.1]hept-5-en-2-exo-carboxamide reported herein reveal H-bonded dimers, with two distinct orientations of the bicyclic portion relative to the carboxamide dimer. In the racemic crystal, each dimer is composed of two enantiomers, and the bicyclic portions have their bridge carbon atom (C-7) on opposite sides of the H-bonded carboxamide dimer moiety. In the enantiomerically pure crystals, the major dimer had both C-7 atoms on the same side of the carboxamide dimer moiety while the minor dimer had the C-7 atoms on opposite sides. The dimers are present in solution, and can be easily monitored.
- Plettner, Erika,Mohle, Ashley,Mwangi, Martin T.,Griscti, Johanna,Patrick, Brian O.,Nair, Ranjeet,Batchelor, Raymond J.,Einstein, Fredrick
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p. 2754 - 2763
(2007/10/03)
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- Biomimetic alcohol oxidations by an iron(III) porphyrin complex: Relevance to cytochrome P-450 catalytic oxidation and involvement of the two-state radical rebound mechanism
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The systematic oxidation reactions of a wide range of alcohols have been carried out by using an iron porphyrin complex in order to understand their relation to cytochrome P-450 enzymes and to have a practical application to organic synthesis. The iron porphyrin complex catalyzed efficiently alcohol oxidation to the respective carbonyl compound via a high-valent iron-oxo porphyrin intermediate ((Porp)Fe=O+). Several mechanistic studies such as isotope 18O labeling, deuterium isotope effect, linear free energy relationship, and ring-opening of radical clock substrate, have suggested that the alcohol is oxidized by a sequence of reactions involving an a-hydroxyalkyl radical intermediate and oxygen rebound to form the gem-diol, dehydration of which yields the carbonyl compounds. Moreover, it has been proposed that a two-state reactivity mechanism can also be adopted for alcohol oxidation reactions in iron porphyrin model systems as exhibited by P-450 enzymes.
- Han, Jung Hee,Yoo, Sang-Kun,Seo, Jin Soo,Hong, Sung Jin,Kim, Seok Kyu,Kim, Cheal
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p. 402 - 406
(2007/10/03)
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- Acetonitrile-assisted highly selective photocatalytic epoxidation of olefins on Ti-containing silica with molecular oxygen
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Highly selective photocatalytic epoxidation of olefins proceeds on Ti-containing silica with tetrahedrally coordinated Ti-oride species with molecular oxygen and a simple addition of MeCN. The Royal Society of Chemistry 2005.
- Shiraishi, Yasuhiro,Morishita, Masatsugu,Hirai, Takayuku
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p. 5977 - 5979
(2008/01/27)
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