Download or read book Transition Metal Activation and Functionalization of Carbon hydrogen Bonds Progress Report December 1 1989 November 30 1992 written by and published by . This book was released on 1992 with total page 37 pages. Available in PDF, EPUB and Kindle. Book excerpt: We are investigating the fundamental thermodynamic and kinetic factors that influence carbon-hydrogen bond activation at homogeneous transition metal centers and the conversion of hydrocarbons into functionalized products of potential use to the chemical industry. Advances have been made in both understanding the interactions of hydrocarbons with metals and in the functionalization of hydrocarbons. We have found that RhCl(PR3)2(CNR) complexes can catalyze the insertion of isonitriles into the C-H bonds or arenes upon photolysis. The mechanism of these reactions was found to proceed by way of initial phosphine dissociation, followed by C-H activation and isonitrile insertion. We have also examined reactions of a series of arenes with (C5Me5)Rh(PMe3)PhH and begun to map out the kinetic and thermodynamic preferences for arene coordination. The effects of resonance, specifically the differences in the Hueckel energies of the bound vs free ligand, are now believed to fully control the C-H activation/?2-coordination equilibria. We have begun to examine the reactions of rhodium isonitrile pyrazolylborates for alkane and arene C-H bond activation. A new, labile, carbodiimide precursor has been developed for these studies. We have completed studies of the reactions of (C5Me5)Rh(PMe3)H2 with D2 and PMe3 that indicate that both?5 2!?3 ring slippage and metal to ring hydride migration occur more facilely than thermal reductive elimination of H2. We have examined the reactions of heterocycles with (C5Me5)Rh(PMe3)PhH and found that pyrrole and furan undergo C-H or N-H activation. Thiophene, however, undergoes C-S bond oxidative addition, and the mechanism of activation has been shown to proceed through sulfur coordination prior to C-S insertion.
Download or read book Transition Metal Activation and Functionalization of Carbon hydrogen Bonds Progress Report December 1 1992 November 30 1993 written by and published by . This book was released on 1993 with total page 3 pages. Available in PDF, EPUB and Kindle. Book excerpt: A method was developed for synthesizing a new complex for studying C-H activation, (HBPz*3)Rh(CNCH2CMe3)(PhN=C=NCH2CMe3). This complex loses the carbodiimide ligand, thereby serving as a precursor for a 16-electron Rh(I) fragment which activates (via oxidative addition) a wide range of aromatic and aliphatic C-H bonds. Mechanism of activation of benzene by this fragment was studied. Reaction of [TpR̀h(CNR)] fragment with aliphatic hydrocarbons was also studied. A study of C-H bond activation by the complex MnH3(dmpe)2 was completed. Reactions of [Ru(dmpe)2] with several small molecules were also investigated. Effects of fluorine substituents on aromatic ring on C-H activation were looked at. Studies of?2-arene coordination with [(C5Me5)Rh(PMe3)] were completed; studies of reaction of this complex with 1,3-disubstituted benzenes are in progress.
Download or read book Energy Research Abstracts written by and published by . This book was released on 1993 with total page 754 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Government Reports Annual Index written by and published by . This book was released on 1992 with total page 1114 pages. Available in PDF, EPUB and Kindle. Book excerpt: Sections 1-2. Keyword Index.--Section 3. Personal author index.--Section 4. Corporate author index.-- Section 5. Contract/grant number index, NTIS order/report number index 1-E.--Section 6. NTIS order/report number index F-Z.
Download or read book Transition Metal Activation and Functionalization of Carbon hydrogen Bonds written by and published by . This book was released on 1992 with total page 37 pages. Available in PDF, EPUB and Kindle. Book excerpt: We are investigating the fundamental thermodynamic and kinetic factors that influence carbon-hydrogen bond activation at homogeneous transition metal centers and the conversion of hydrocarbons into functionalized products of potential use to the chemical industry. Advances have been made in both understanding the interactions of hydrocarbons with metals and in the functionalization of hydrocarbons. We have found that RhCl(PR3)2(CNR) complexes can catalyze the insertion of isonitriles into the C-H bonds or arenes upon photolysis. The mechanism of these reactions was found to proceed by way of initial phosphine dissociation, followed by C-H activation and isonitrile insertion. We have also examined reactions of a series of arenes with (C5Me5)Rh(PMe3)PhH and begun to map out the kinetic and thermodynamic preferences for arene coordination. The effects of resonance, specifically the differences in the Hueckel energies of the bound vs free ligand, are now believed to fully control the C-H activation/?2-coordination equilibria. We have begun to examine the reactions of rhodium isonitrile pyrazolylborates for alkane and arene C-H bond activation. A new, labile, carbodiimide precursor has been developed for these studies. We have completed studies of the reactions of (C5Me5)Rh(PMe3)H2 with D2 and PMe3 that indicate that both?5 2!?3 ring slippage and metal to ring hydride migration occur more facilely than thermal reductive elimination of H2. We have examined the reactions of heterocycles with (C5Me5)Rh(PMe3)PhH and found that pyrrole and furan undergo C-H or N-H activation. Thiophene, however, undergoes C-S bond oxidative addition, and the mechanism of activation has been shown to proceed through sulfur coordination prior to C-S insertion.
Download or read book Government Reports Announcements Index written by and published by . This book was released on 1992 with total page 1736 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book C H and C X Bond Functionalization written by Xavi Ribas and published by Royal Society of Chemistry. This book was released on 2013-05-24 with total page 489 pages. Available in PDF, EPUB and Kindle. Book excerpt: Cross-coupling reactions involving C-H and C-X bond functionalisation are commonplace in natural product synthesis and natural products, therapeutic agents, biological probes, and advanced materials. Much attention has been given to understanding the mechanistic strategies used to achieve this, making this a hot topic in recent years. In this edited book, contributions from across the globe examine these strategies, with a particular focus on palladium and copper, as well as iron – an emerging element in this field. Reviewing the recent literature, the book presents an in-depth understanding of the field, guiding the reader to achieving the best synthetic strategies for aromatic functionalisation. Organic and Organometallic chemists, as well as natural product and pharmaceutical scientists, will find this an essential guide to a major transformation currently underway in synthetic chemistry.
Download or read book Cleavage of Carbon Carbon Single Bonds by Transition Metals written by Masahiro Murakami and published by John Wiley & Sons. This book was released on 2015-09-21 with total page 292 pages. Available in PDF, EPUB and Kindle. Book excerpt: Edited by leading experts and pioneers in the field, this is the first up-to-date book on this hot topic. The authors provide synthetic chemists with different methods to activate carbon-carbon sigma bonds in organic molecules promoted by transition metal complexes. They explain the basic principles and strategies for carbon-carbon bond cleavage and highlight recently developed synthetic protocols based on this methodology. In so doing, they cover cleavage of C-C bonds in strained molecules, reactions involving elimination of carbon dioxide and ketones, reactions via retroallylation, and cleavage of C-C bonds of ketones and nitriles. The result is an excellent information source for researchers in academia and industry working in the field of synthetic organic chemistry, while equally serving as supplementary reading for advanced courses in organometallic chemistry and catalysis.
Download or read book Chemistry of Oxygenates on Transition Metal Surfaces written by and published by . This book was released on 1991 with total page 4 pages. Available in PDF, EPUB and Kindle. Book excerpt: Goal is to understand the requirements for and competition between activation of C-H, C-C, and C-O bonds in the synthesis and decomposition of oxygenates on transition metal surfaces. Efforts during the past year was devoted primarily to the role of activation of [beta]-CH bonds in decarbonylation of higher oxygenates on surfaces of metals such as Rh and Pd; studies were completed of more than a dozen C1-C3 oxygenates on Rh(111), and progress was made with reagents for which [beta]-CH scission is blocked. It is shown that alcohols and aldehydes do not react via a common pathway on on Rh(111). Ethanol and acetaldehyde are formed from CO + H2 by parallel routes on Rh catalysts which do not contain interacting supports or oxide promoters; i.e., the two compounds result from CO insertion into different metal-hydrocarbon bonds. Aldehydes decarbonylate via [alpha]-CH scission to form acyl, followed by C-C scission to release an alkyl ligand; this ligand undergoes hydrogenation and dehydrogenation steps. Alcohols form surface alkoxides, but these do not dehydrogenate further to the aldehydes, they release CO + H2 but no volatile hydrocarbon. These results indicate that [beta]-CH scissors to form a surface oxametallacycle intermediate; supporting evidence is spresented for this intermediate. Chemistry of alcohols blocked to different extends at the [beta]-position was also studied; complete blocking (CF3CH2OH) forces the reaction to follow the aldehyde-acyl path, while partial substitution at the [beta] position (branched alcohols) favors the oxametallacycle pathway. (DLC).
Download or read book Wette Wilhelm Martin Leberecht de 1870 1849 written by and published by . This book was released on 1890 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Zeitungsausschnitte.
Download or read book Activation of Saturated Hydrocarbons by Transition Metal Complexes written by A.E. Shilov and published by Springer Science & Business Media. This book was released on 1984-06-30 with total page 226 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Transition metal Mediated Formation and Cleavage of Carbon hydrogen Bonds written by Paul Fredrich Seidler and published by . This book was released on 1985 with total page 384 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Activation of Carbon fluorine Bonds and Carbon hydrogen Bonds with Transition Metal Compounds written by Jian Yuan and published by . This book was released on 2009 with total page 768 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Activation of Carbon Hydrogen Bonds by Transition Metal Compounds written by Jeffrey Ira Melzer and published by . This book was released on 1982 with total page 142 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Transition Metal Mediated Synthesis of Heterocycles Via Carbon hydrogen Bond Activation written by Ling Li and published by . This book was released on 2009 with total page 514 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Part 1 written by Derek Schipper and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Part 1: Transition-metal-catalyzed direct transformations of aromatic C-H bonds are emerging as valuable tools in organic synthesis. These reactions are attractive because of they allow for inherently efficient construction of organic building blocks by minimizing the pre-activation of substrates. Of these processes, direct arylation has recently received much attention due to the importance of the biaryl core in medicinal and materials chemistry. Also, alkyne hydroarylation has garnered interest because it allows for the atom-economical synthesis of functionalized alkenes directly from simple arenes and alkynes. Described in this thesis are number of advancements in these areas. First, palladium catalyzed direct arylation of azine N-oxides using synthetically important aryl triflates is described. Interesting reactivity of aryl triflates compared to aryl bromides was uncovered and exploited in the synthesis of a compound that exhibits antimalarial and antimicrobial activity. Also reported is the efficient, direct arylation enabled (formal) synthesis of six thiophene based organic electronic materials in high yields using simple starting materials. Additionally, the site-selective direct arylation of both sp2 and sp3 sites on azine N-oxide substrates is described. The arylation reactions are carried out in either a divergent manner or a sequential manner and is applied to the synthesis of the natural products, Papaverine and Crykonisine. Mechanistic investigations point towards the intimate involvement of the base in the mechanism of these reactions. Next, the rhodium(III)-catalyzed hydroarylation of internal alkynes is described. Good yields are obtained for a variety of alkynes and arenes with excellent regioselectivity for unsymmetrically substituted alkynes. Mechanistic investigations suggest that this reaction proceeds through arene metalation with the cationic rhodium catalyst, which enables challenging intermolecular reactivity. Part 2: Access to single enantiomer compounds is a fundamental goal in organic chemistry and despite remarkable advances in enantioselective synthesis, their preparation remains a challenge. Kinetic resolution of racemic products is an important method to access enantioenriched compounds, especially when alternative methods are scarce. Described in this thesis is the resolution of tertiary and secondary alcohols, which arise from ketone and aldehyde aldol additions. The method is technically simple, easily scalable, and provides tertiary and secondary alcohols in high enantiomeric ratios. A rationale for the unique reactivity/selectivity associated with (1S,2R)-N-methylephedrine in the resolution is proposed. Organocatalysis is a rapidly developing, powerful field for the construction of enantioenriched organic molecules. Described here is a complimentary class of organocatalysis using simple aldehydes as temporary tethers to perform challenging formally intermolecular reactions at room temperature. This strategy allows for the enantioselective, intermolecular cope-type hydroamination of allylic amines with hydroxyl amines. Also, interesting catalytic reactivity for dichloromethane is revealed.
Download or read book Synthetic and Mechanistic Studies of Carbon hydrogen Bond Activation by Iridium III Complexes and Development of a Transition Metal Catalyzed Alkene Aziridination Reaction written by Peter James Alaimo and published by . This book was released on 1999 with total page 556 pages. Available in PDF, EPUB and Kindle. Book excerpt:
