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Showing 1 to 20 of 23 for “"Ketenes."”.
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Synthesis of 3-aminocyclobutenones via [2 + 2] cycloaddition of ynamides and ketenes
Ynamides react with various classes of ketenes in intermolecular [2 + 2] cycloaddition to afford substituted cyclobutenones with complete regioselectivity. The cycloaddition substrates are easily assembled from amine derivatives by copper-catalyzed N-alkynylation with acetylenic bromides. The …
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[4 + 1] annulation reactions of (trialkylsilyl)ketenes : synthesis of substituted indanones and cyclopentenones
(Trialkylsilyl)vinylketenes ("(TAS)vinylketenes") and (trialkylsilyl)arylketenes ("(TAS)- arylketenes") function as versatile four-carbon building blocks for the synthesis of carbocyclic and heterocyclic compounds. A new [4 + 1] annulation strategy for the synthesis of substituted 2-indanones, …
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Application of ketenes and allenes in the total synthesis of diterpene quinones and indoles
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemistry, 1995.
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Asymmetric synthesis of amines by the catalytic enantioselective additions of hydrazoic acid to ketenes
… enantioselective additions of HN3 to hindered ketenes was investigated. It was demonstrated that a new planar-chiral catalyst (1.5) is an excellent catalyst for the enantioselective addition of HN3 to hindered ketenes, en route to enantioenriched amines. The addition of HN3 to a ketene is …
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New methodology for the generation and cycloadditions of thio-substituted ketenes ; A synthetic approach to the taxol A-ring
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemistry, 1997.
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Synthesis of Aryl Ynol Ethers and Their Synthetic Applications
… have also been used as ideal precursors of ketenes and surrogates of alkynes with a higher oxidation state in many reactions. However, few studies focused on the applications of aryl ynol ethers, because their synthetic methods are limited. To make aryl ynol ethers practical synthetic …
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Cracking Meldrum's Acid: Lowering the Temperature
… incompatibilities is required. Utilisation of ketenes as a carbonyl source may be one such protocol. Ketenes are highly reactive intermediates that can be produced and reacted under the same reaction conditions, including at a neutral pH. Ketenes therefore present an attractive way to produce …
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Cracking Meldrum's Acid: Lowering the Temperature
… incompatibilities is required. Utilisation of ketenes as a carbonyl source may be one such protocol. Ketenes are highly reactive intermediates that can be produced and reacted under the same reaction conditions, including at a neutral pH. Ketenes therefore present an attractive way to produce …
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Large-Scale Applications of Multi-Reference Methods in Chemistry and Development of a Multi-Reference Moller-Plesset Perturbation Theory Program
… and relations to the more unusual class of enyne-ketenes are analyzed. The class of enyne-ketenes (and also the enyne-allenes) show a broad spectrum of possible intermediates (diradicals, zwitterions, allenes). The electronic structures of these intermediates are also possible for the (heteroatom …
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ΜΕΛΕΤΗ ΑΝΤΙΔΡΑΣΕΩΝ ΠΡΟΣΘΗΚΗΣ ΠΥΡΑΖΟΛΙΚΩΝ ΣΥΣΤΗΜΑΤΩΝ ΜΕ 1, 3-ΔΙΠΟΛΑ ΚΑΙ ΚΕΤΕΝΕΣ
… DERIVATIVES WITH NITRILOXIDES, NITRILIMINESAND KETENES. NON AROMATIC METHYLENE- PYRAZOLES IN PRESENCE OF NITRILOXIDE AND NITRILIMINES UNDERGO STEREOSELECTIVELY 1,3-DIPOLAR CYCLOADDITION, IN PRESENCE OF DIPHENYLNETENE THE CORRESPONDING 1-DIPHENYL-ACETYL (3,3-DIPHENYL- 2-AROGLOXY-2-PROPENYYL)-4,4 …
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TANDEM BENZANNULATION-CYCLIZATION STRATEGIES FOR THE SYNTHESIS OF HIGHLY SUBSTITUTED INDOLES
… strategies involved the reaction of vinylketenes (or aryl ketenes) with ynamides or with ynehydrazides to afford highly substituted phenols via a pericyclic cascade mechanism. The vinylketenes were generated via the Wolff rearrangement of diazo enones or via the 4π electrocyclic …
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Enantioselective nucleophile-catalyzed cycloadditions
… nucleophile-catalyzed [2+2] cycloaddition of ketenes with aldehydes. This is the first report of a catalytic enantioselective synthesis of trisubstituted [beta]-lactones. Two enantioselective phosphine-catalyzed [3+2] cycloadditions of allenoates are detailed in Chapter 2. A method for the …
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Tandem benzannulation-ring closing metathesis strategy for the synthesis of benzo-fused nitrogen heterocycles ;
… are generated from the addition of amines to ketenes, which are formed in situ from the retro-ene reaction of alkynyl ethers.
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Asymmetric nucleophilic catalysis with planar-chiral DMAP derivatives and chiral phosphines : synthetic and mechanistic studies
… alkyl fluorides via the [alpha]-fluorination of ketenes catalyzed by a planar-chiral nucleophile with N-fluorodibenzenesulfonimide in the presence of sodium pentafluorophenoxide. Chapter 3 describes the development and preliminary mechanistic study of the first asymmetric, phosphine-catalyzed …
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Mild [Pd(OAc)2/PPh3] catalyzed cyclization reactions of N-Alkyl-2-vinylazetidines with heterocumulenes.
… Unoptimized results in reactions with ketenes and ketenimines indicate a variety of carbon electrophiles could be used for the insertion and suggest great potential for these methods in organic synthesis. The steric and electronic influence of substituents on either the azetidine or …
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Substituent Effects: A Computational Study on Stabilities of Cumulenes and Low Barrier Hydrogen Bonds
… of substituents on the stabilities of cumulenes-ketenes, allenes, diazomethanes and isocyanates and related systems-alkynes, nitriles and nitrile oxides is studied using the density functional theory (B3LYP, SVWN and BP86) and ab initio (HF, MP2) calculations at the 6-31G* basis set level. Using …
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Pericyclic reactions in organic synthesis
… of carboxylic amides. The addition of amines to ketenes generated in situ via the retro-ene reaction of alkynyl ethers provides amides in good yield, in many cases with ethylene as the only byproduct of the reaction. With the exception of primary, unbranched amines, potential side reactions …
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Ultrahigh Vacuum Studies of the Kinetics and Reaction Mechanisms of Ozone with Surface-Bound Fullerenes
… as carbonyls, anhydrides, esters, ethers, and ketenes. Larger fullerenes (C₇₀, C₇₆, C₇₈, and C₈₄) were also exposed to gas-phase ozone, in order to observe the reaction rate for ozonolysis and to propose an initial mechanism for ozone exposure. The results indicate that the structure of the …
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Development of asymmetric catalysts based on planar-chiral [pi]-complxes of nigrogen heterocycles with iron
… and addition of alcohols to ketenes. The DMAP analog was resolved by chiral HPLC, but resulted in a disappointing selectivity when used as a catalyst for the kinetic resolution of 1-phenylethanol by acylation with acetic anhydride. By using the pentaphenylcyclopentadienyliron …
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