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Showing 1 to 19 of 19 for “"Carbenoid"”.
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Carbenoid insertions and cyclometallations of zirconacycles
… of chloro(aryl)methyllithiums (benzyl carbenoids) into a range of<br/>zirconacyclopentenes and zirconacyclopentanes.<br/><br/>Benzyl carbenoid insertion into a zirconacyclopentene generated the<br/>zirconacyclohexene via a 1,2-metalate rearrangement. A low temperature …
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Reactivity of Aluminum Carbenoid with Unsaturated Substrates
Reactivity patterns of the β-diketiminate aluminum(I) complex NacNacAl towards a variety of unsaturated molecules were determined. Reaction of NacNacAl with one equivalent of benzophenone affords η2(C,O) adduct III-2 that undergoes cyclization reactions with benzophenone (III-3), aldimine (III-4), …
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Novel titanium carbenoid reagents: diversity orientated synthesis of indoles and spirocycles
… of lactones with functionalized titanium carbenoid reagents followed by acid-induced cyclisation of the resulting enol ethers constitutes a new method for the preparation of [4.4], [4.5], and [5.5] spiroacetals (1,6-dioxaspiro[4.4]nonanes, 1,6-dioxaspiro[4.5]decanes and …
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Intramolecular carbenoid insertion : reactions of [alpha] -diazoketones derived from benzothienyl, pyrolyl and indolyl alkanoic acids with rhodium (II) acetate
Recent studies have shown that the rhodium (II) acetate decomposition chemistry observed for a-diazoketones tethered to thienyl, furanyl, and benzofuranyl moieties is dependent not only on the nature of the heteroatom but also on the length of the aliphatic tether linking the diazoketone moiety …
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The generation and reactivity of functionalised organozinc carbenoids for cyclopropane synthesis
… and reactivity of functionalised organozinc carbenoids for cyclopropane synthesis with alkenes. In the introductory chapter, a brief overview of the different methods for preparation of heteroatom-functionalised cyclopropanes is presented, including [2+1] cycloaddition reactions using a …
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Studies towards the total synthesis of labiatin A
… the total synthesis of labiatin A using metal carbenoid chemistry. The work described herein shows the most recent contribution to this field from our research group. Chapter I provides an introduction to metal carbenoids and their uses in organic synthesis. In particular, the synthesis of …
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I Ceric ammonium nitrate-mediated oxidative cleavages of hemiacetals II Synthesis of beta-proline derivatives through the tandem chain extension-imine capture reaction
… generated through the use of the zinc carbenoid-mediated tandem chain extension-aldol reaction was developed. This chemistry has been applied towards the formation of a class of natural products, phaseolinic acids, in two steps from a commercially available beta-keto ester, methyl …
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The attempted synthesis of precursors of tetraaryldiazoethanes
… of these compounds is of importance since the carbenoid and carbonium ion decomposition of these compounds to tetraaryldiazoethanes would give formation about the nature of these intermediates.
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Ketomethylene isosteric amide bond replacements via the zinc -mediated chain extension of N -protected amino acids
… esters to gamma-keto esters utilizing a zinc carbenoid was developed. The reaction was used on amino acids containing various protective groups and a variety of side chain functionality. This method was used in the incorporation of ketomethylene isosteric amino acid replacements within amino …
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Intramolecular [4+1] pyrroline annulation as a general method for the synthesis of pyrrolizidine alkaloids
… and introduced the heteroatom equivalent of the carbenoid [4+1] annulation as a method or alkaloid synthesis. [See docment for associated image]
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I The synthesis of papyracillic acids: Application of the tandem chain extension-acylation reaction II Diastereoselective synthesis of beta-methyl-gamma-keto esters through the utility of an L-serine auxiliary
… ester backbone, through a methyl substituted carbenoid, allowed for the synthesis of papyracillic acid B and 4-epi-papyracillic acid C. Comparison between the reported and experimental spectral data for papyracillic acid B and 4- epi-papyracillic acid C permitted structural and stereochemical …
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N-Heterocyclic Carbenes of the Late Transition Metals: A Computational and Structural Database Study
… considers the change in the hybridization of the carbenoid carbon to incorporate more p character. The latter hypothesis is supported by the results. Analysis of these complexes using the natural bond orbital method evinces NHC ligands possessing trans influence.
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[4 + 1] annulation reactions of (trialkylsilyl)ketenes : synthesis of substituted indanones and cyclopentenones
… has been developed. In addition, a new class of carbenoid reagents for our previously reported [4 + 1] cyclopentenone annulation has been identified. Studies have shown that the reaction of a- benzotriazolyl organolithium compounds (prepared via metallation of readily available N- substituted …
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Formation of 2,5-trans-tetrahydrofuran-3-one application towards the synthesis of natural products
… a methodology based on an intramolecular tandem carbenoid insertion and ylide rearrangement reaction of a diazoketone. This diazoketone undergoes a nucleophilic attack onto an empty d orbital of the transition metal. The transition metal back donates the electrons of one of its d orbital to the …
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Formal Insertion Reactions Of Stannylenes And Germylenes Into Phosphorus-Halogen Bonds: A Structural And Mechanistic Investigation
<p>Insertion reactions of Group 14 carbenoids, divalent species of the form (R<sub>2</sub>N)<sub>2</sub>M (M = Ge or Sn) into the P-halogen bond of halophosphines have been known for some time. However, very few examples have been reported and no evidence has been presented regarding the mechanism …
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Progress in transition metal-based enantioselective catalysis
… of catalyzed, enantioselective insertion of carbenoid fragments into C-N sigma bonds are described (eq 3). The system uses commercially-available catalyst components and gives highly enantioselective rearrangements of benzylamine-, allylamine-, and [alpha]-aminocarbonyl-containing substrates. …
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Gold-catalysed reactions of Nitrogen containing molecules
… using a ynamide oxidation approach. Gold carbenoid intermediates can be formed regioselectively by action of an external oxidising agent, and were used in 1,2-insertion reactions.
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Studies on Syntheses of 1-Azaspirocycles, 2,6-Disubstituted 3-Piperidinols and cls-Decahydroquinolines
… steric interactions encountered by the Rh(II)-carbenoid with the tertiary CH insertion site might have impeded the desired CH insertion reaction pathway. Alkylidenecarbene generation-1,5-CH insertion reaction of 5-(3-oxobutyl)pyrrolidin-2-ones and 6-(3-oxobutyl)piperidin-2-ones was next …