The Experts below are selected from a list of 162 Experts worldwide ranked by ideXlab platform
Xiuzhi Susan Sun - One of the best experts on this subject based on the ideXlab platform.
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Chemical pathways of epoxidized and hydroxylated fatty acid methyl esters and triglycerides with phosphoric acid
Journal of Materials Chemistry, 2011Co-Authors: Byung Jun Kollbe Ahn, Stefan Kraft, Xiuzhi Susan SunAbstract:The polymerization pathways of epoxidized and hydroxylated triglycerides with phosphoric acid (H3PO4) were investigated using model Reactions. Involved epoxides and diols were derived from oleic acid methyl ester, which was easily monitored by one- and two-dimensional nuclear magnetic resonance (NMR) techniques as well as electrospray ionization mass spectroscopy (ESI-MS). Phosphoric acid played two key functions: (a) as a Brønsted acid catalyst that activated the epoxide toward nucleophilic attack by the diol, thus generating ether (C–O–C) cross-linkages; and (b) as a Reaction Partner establishing phosphate ester linkages [(RO)2(O)P–O–C, R = C or H]. In studies with 18O labeled diol, phosphate esters formed exclusively from H3PO4 and epoxide without incorporation of diol whereas diols acted as polymerization initiators in polyether formations.
H. Ihee - One of the best experts on this subject based on the ideXlab platform.
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Recombination of photodissociated iodine: A time-resolved x-ray-diffraction study
Journal of Chemical Physics, 2006Co-Authors: Michaël Wulff, S. Bratos, F. Mirloup, Rodolphe Vuilleumier, Maciej Lorenc, Anton Plech, Q Kong, H. IheeAbstract:A time-resolved x-ray-diffraction experiment is presented that aims to study the recombination of laser-dissociated iodine molecules dissolved in CCl4. This process is monitored over an extended time interval from pico- to microseconds. The variations of atom-atom distances are probed with a milliangstrom resolution. A recent theory of time-resolved x-ray diffraction is used to analyze the experimental data; it employs the correlation function approach of statistical mechanics. The most striking outcome of this study is the experimental determination of time-dependent I-I atom-atom distribution functions. The structure of the CCl4 solvent changes simultaneously; the solvent thus appears as a Reaction Partner rather than an inert medium hosting it. Thermal expansion of the system is nonuniform in time, an effect due to the presence of the acoustic horizon. One concludes that a time-resolved x-ray diffraction permits real-time visualization of solvent and solute motions during a chemical Reaction.
Byung Jun Kollbe Ahn - One of the best experts on this subject based on the ideXlab platform.
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Chemical pathways of epoxidized and hydroxylated fatty acid methyl esters and triglycerides with phosphoric acid
Journal of Materials Chemistry, 2011Co-Authors: Byung Jun Kollbe Ahn, Stefan Kraft, Xiuzhi Susan SunAbstract:The polymerization pathways of epoxidized and hydroxylated triglycerides with phosphoric acid (H3PO4) were investigated using model Reactions. Involved epoxides and diols were derived from oleic acid methyl ester, which was easily monitored by one- and two-dimensional nuclear magnetic resonance (NMR) techniques as well as electrospray ionization mass spectroscopy (ESI-MS). Phosphoric acid played two key functions: (a) as a Brønsted acid catalyst that activated the epoxide toward nucleophilic attack by the diol, thus generating ether (C–O–C) cross-linkages; and (b) as a Reaction Partner establishing phosphate ester linkages [(RO)2(O)P–O–C, R = C or H]. In studies with 18O labeled diol, phosphate esters formed exclusively from H3PO4 and epoxide without incorporation of diol whereas diols acted as polymerization initiators in polyether formations.
Rick L. Danheiser - One of the best experts on this subject based on the ideXlab platform.
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Supporting Information: AzaAza Diels–Alder Reactions of Nitriles, N , N -Dimethylhydrazones, and Oximino Ethers. Application in Formal [2 + 2 + 2] Cycloadditions for the Synthesis of Pyridines
The Journal of Organic Chemistry, 2017Co-Authors: Philip J. Hamzik, Anne-sophie Goutierre, Takeo Sakai, Rick L. DanheiserAbstract:Metal-free, formal [2 + 2 + 2] cycloaddition strategies for the synthesis of polycyclic pyridine derivatives are described. The overall transformation proceeds via a two-stage pericyclic cascade mechanism. In the first step, an intramolecular propargylic ene Reaction generates a vinylallene that is necessarily locked in the s-cis conformation. This vinylallene exhibits exceptional reactivity as a Diels–Alder Reaction Partner and engages in [4 + 2] cycloadditions with normally unreactive azadienophiles including unactivated cyano groups and heterosubstituted imine derivatives such as dimethylhydrazones and oximino ethers. Few examples of oximino ether Diels–Alder Reactions have been reported previously, and normal electron-demand [4 + 2] cycloadditions of unactivated dialkylhydrazones are unprecedented. Overall, this metal-free formal [2 + 2 + 2] cycloaddition provides access to polycyclic pyridine derivatives and complements transition-metal-catalyzed [2 + 2 + 2] strategies.
Romano V A Orru - One of the best experts on this subject based on the ideXlab platform.
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1 azadienes in cycloaddition and multicomponent Reactions towards n heterocycles
Chemical Communications, 2008Co-Authors: Bas Groenendaal, Eelco Ruijter, Romano V A OrruAbstract:1-Azadienes are versatile building blocks for the efficient construction of various N-heterocycles. Depending on the substitution pattern and Reaction Partner, they may participate in a range of different Reactions. An overview of recent methods for the generation of 1-azadienes is presented, as well as their application in cycloaddition, electrocyclization, and multicomponent Reactions. Considering the broad range of reactivities and resulting heterocyclic scaffold structures, 1-azadienes are very useful reactive intermediates for the development of modular Reaction sequences in diversity-oriented synthesis.
