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Showing 1 to 20 of 33 for “"cycloadducts"”.
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Synthetic Applications Of The Photochemical Cycloaddition Reactions Of N-acylindoles And Conformational Studies Of The Cycloadducts
… study revealed that the N-acylindoles and their cycloadducts with cyclopentene exist as two slowly interconverting conformers in solution and that the photodimers exist as three slowly interconverting conformers. These conformers arise from the possible orientations of the amide carbonyl present …
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Arenophile-mediated dearomative functionalization of unactivated arenes
… an “arenophile” called MTAD. Arene-arenophile cycloadducts are formed by irradiation of mixtures of unactivated arenes and MTAD at cryogenic temperatures with visible light. These cycloadducts are subsequently used as substrates in metal-catalyzed transformations. In chapter one a …
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Silenes: Novel Reagents for Organic Synthesis
… of acylpolysilanes at 180 oC produced [4+2] cycloadducts, while [2+2] cycloadducts and ‘ene’ products were not observed. Similarly, it was found that intramolecular cycloadducts can be generated at lower temperatures by the addition of MeLi•LiBr to acylpolysilanes. These two approaches …
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Synthesis and cycloaddition chemistry 1,3-Bis(phenylsulfonyl)propadiene
… and peri-selectivity study to yield the [4+2] cycloadducts. Treatment of the furan cycloadducts with potassium t-butoxide opened up the oxygen bridge of three of the furan cycloadducts and resulted in aromatisation to the 3-phenylsulfonyl-2phenylsulfonylmethylphenol. The remaining cycloadduct …
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General method for the synthesis of pseudodisaccharides. Diels-Alder approach to the synthesis of pseudodisaccharides
… by chemical manipulation of the resulting cycloadducts. The thesis also describes the synthesis of inhibitors of Golgi ¿-mannosidase II and glucokinase. The first chapter is a comprehensive survey of the reported synthetic routes to pseudodisaccharides from the literature. The results and …
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[4 + 2] cycloadditions of iminoacetonitriles : synthesis of highly substituted tetrahydropyridines and indolizidine alkaloids
… and indolizidines. The [alpha]-amino nitrile cycloadducts are versatile synthetic intermediates that participate in a variety of stereoselective transformations to further elaborate the six-membered ring. This thesis describes the scope of the intermolecular [4 + 2] cycloaddition of …
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[4+2] cycloadditions of iminoacetonitriles : a general strategy for the synthesis of quinolizidines, indolizidines, and piperidines
… and piperidines. The resultant a-amino nitrile cycloadducts are versatile synthetic intermediates which can be further elaborated by stereoselective alkylation, reduction, reductive cyclization, and Bruylants reactions. The first part of this thesis describes the full details of our studies on …
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Synthesis of nitrogen heterocycles via the intramolecular [4+2] cycloaddition of iminoacetonitriles
… quinolizidines and indolizidines. The cycloadducts are formed with a high preference for an exo-orientated cyano group due to the a-amino nitrile anomeric effect. The substrates for these [4+2] cycloadditions are prepared from readily available alcohols via a Mitsunobu reaction with the …
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Intramolecular (4+2) -Cycloadditions of Three Heterodienes: Nitrosoalkenes, Nitroalkenes, and Z-Alpha,beta-Unsaturated Aldehydes
… (6-6)- and hexahydroindene (6-5)-oxazine cycloadducts varied. In the enol ether cases, the success of the cycloaddition depended on the olefin geometry. Only the dienophile bearing the proper geometry for secondary orbital overlap cyclized in high yield and with good stereoselectivity. The …
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ΜΕΛΕΤΗ ΑΝΤΙΔΡΑΣΕΩΝ 1,3-ΔΙΠΟΛΙΚΗΣ ΚΥΚΛΟΠΡΟΣΘΗΚΗΣ ΣΕ ΕΤΕΡΟΚΥΚΛΙΚΑ ΣΥΣΤΗΜΑΤΑ
… NITRILE OXIDES AND NITRILIMINES TO AFFORD SPIRO CYCLOADDUCTS, BY ADDITION OF THE DIPOLE ON THE EXOCYCLIC DOUBLE BOND. THE REACTIONS ARE STEREOSPECIFIC AND REGIOSELECTIVE, GIVING IN ALL CASES ONLY ONE REGIOISOMER, IN WHICH THE ANIONIC CENTER OF THE DIPOLE IS JOINED WITH THE TERTIARY CARBON ATOM OF …
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Cycloaddition studies in steroidal 14,16-dienes
… built-in bridge substituents of derived 14,17-cycloadducts, for eventual conversion into bridge-functionalised 19-norsteroids.
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Multicomponent Diels-Alder Sequences of 1-Aminodendralenes
… These condensation/Diels-Alder/Diels-Alder cycloadducts were generated with high diastereoselectivity, the origins of which were investigated and explained with the use of density functional theory calculations (carried out by Prof Paddon-Row). By reversing the order of events, that is …
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Multicomponent Diels-Alder Sequences of 1-Aminodendralenes
… These condensation/Diels-Alder/Diels-Alder cycloadducts were generated with high diastereoselectivity, the origins of which were investigated and explained with the use of density functional theory calculations (carried out by Prof Paddon-Row). By reversing the order of events, that is …
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Tandem Double Intramolecular [4+2]/[3+2] Cycloaddition of Nitro Olefins: Part I: Construction of Piperidine Rings. Part II: Construction of Vicinal Quaternary Stereogenic Centers. Part III: Progress Toward a Total Synthesis of Daphnilactone B
… two epimeric nitroso acetals. Ozonolysis of the cycloadducts, followed by hydrogenolysis and intramolecular acylation provided the intermediates for the total synthesis that may be elaborated to daphnilactone B. Possible routes to complete the synthesis are also discussed.
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Mechanistic and Synthetic Studies of Oxidopyrylium Cycloaddition Reactions
… synthetic advancements of their corresponding cycloadducts. Chapter 1 is a literature review where we specifically outline the use of oxidopyrylium cycloadditions in the synthesis of natural products. This includes the mention of previous syntheses prior to 2008, and a more thorough examination …
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Enantioselective [4 + 2] cycloadditions of iminoacetonitriles : application to the total synthesis of (-)-quinolizidine 2071
… and indolizidines. The resulting a-amino nitrile cycloadducts are versatile intermediates that can be further elaborated in a stereoselective manner. This thesis describes the development of intramolecular, enantioselective aza Diels- Alder cycloadditions promoted by chiral Brønsted acids as well …
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The synthesis and reactivity of 3-amino and 3-oxycyclopentadienones
… and acceptors provided chemo and regioselective cycloadducts in an efficient fashion. Final studies included investigations of the iron cyclopentadienones in diastereoselective reactions.
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Enantioselective synthesis of 2,2,5-Tri- and 2,2,5,5-tetrasubstituted tetrahydrofurans and synthesis of diketopiperazine containing natural products
… substituted furans in excellent yield. The cycloadducts can be stereoselectively transformed into tetrasubstituted tetrahydrofurans via ring-opening metathesis/cross-metathesis or oxidative cleavage and refunctionalization. A partial synthesis of the bioactive diketopiperazine containing …
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Chemoselective and Stereoselective Exploration of the Chemical Reactivity Space of Castagnoli-Cushman-Derived Allylic Lactamoyl Esters: Application to the Synthesis of Aza-Polycyclic Architectures
… anhydrides, followed by interception of the cycloadducts in cross-coupling manifolds (<em>e.g.</em>, Sonogashira coupling) and concomitant lithiation-cyclization of the tethered alkyne. An unprecedented example of a hydroamino alkylation that is transition metal-free and occurs at room …
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Synthetic and mechanistic aspects of the reactions of α-diazosulfoxides
… Trapping of the α-oxosulfine intermediates as cycloadducts by reaction with 2,3-dimethyl-1,3-butadiene proved useful both synthetically and mechanistically. As the stereochemistry of the α-oxosulfine is retained in the cycloadducts, this provided an ideal method for characterisation of this key …
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