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Showing 1 to 20 of 370 for “"cycloaddition"”.
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Cycloaddition Reactions of (Di)tetrelenes
This thesis examines a variety of cycloaddition reactions of multiply-bonded heavy analogues of carbon. With the aid of a mechanistic probe, the mechanism of the addition of alkynes to a germene and a digermyne was examined. In both cases, the addition does not involve the itermediacy of an vinyl …
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Cycloaddition studies in steroidal 14,16-dienes
… aim was to explore the scope for carrying out cycloaddition reactions, and exploiting the built-in bridge substituents of derived 14,17-cycloadducts, for eventual conversion into bridge-functionalised 19-norsteroids.
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Cycloaddition : fragmentation methodology in steroidal hormone design
Summary in English.
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An Investigation of Gold(I) Catalyzed Cycloaddition Reactions
… the furan moiety to give transannular [4C+3C] cycloaddition products. In addition, the tricyclic ring system with an oxabicyclo-[3.2.1]octadiene and a fused 6-membered ring was produced efficiently using the readily available propargyl ester-furan substrate in the presence of a Au(I) complex. …
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Mechanistic and Synthetic Studies of Oxidopyrylium Cycloaddition Reactions
<p>Cycloaddition chemistry has historically served as a robust route to stereo-rich and highly functionalized cyclic and heterocyclic compounds. Herein we describe our examination of 3-hydroxy-4-pyrone-derived oxidopyrylium cycloadditions in both mechanistic considerations as well as the unique …
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Preparation and Cycloaddition Reactions of Oxazoline Nitrogen Oxides
… with ortho esters or amide acetals. 3 + 2 Cycloaddition reactions of the oxazoline N-oxides and the related pyrroline N-oxides with phenyl isocyanate, dimethyl acetylenedicarboxylate, methyl phenylpropiolate, phenylpropiolonitrile, methyl acrylate, and acrylonitrile were carried out. The …
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Synthesis and cycloaddition chemistry 1,3-Bis(phenylsulfonyl)propadiene
An efficient synthesis of the highly activated I J-bis(phenylsulfonyl)propadiene is described. Starting from benzenesulfonyl chloride and propargyl bromide the key step of the synthesis is the addition of benzene sulfonyl iodide to phenylsulfonylpropyne. This is demonstrated to occur under thermal …
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Inter- and intramolecular (4+2) cycloaddition reactions and tandem inter- and intramolecular (4+2)/intramolecular (3+2)cycloaddition reactions of nitroalkenes
Both inter- and intramolecular cycloadditions of nitroalkenes with Lewis acid catalysis were investigated. The intramolecular cycloadditions of nitroalkenes were found to be completely stereoselective for trisubstituted nitroalkenes. Intermolecular cycloadditions of aromatic nitroalkenes were found …
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Alkinhaltige Blockcopolymere und ihre Modifizierung mittels 1,3-dipolarer Cycloaddition
… effizienten Cu(I)-katalyisierten 1,3-dipolaren Cycloadditionen (Click-Chemie) wurde diese modifiziert. Insbesondere durch die Addition dendritischer Verbindungen gelang die Darstellung nanosopischer Objekte. Darüber hinaus konnten dünne Filme phasenseparierten Blockcopolymere selektiv und …
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Five-Membered Carbocycles Through (3 Plus 2)-Cycloaddition Reactions
Made available in DSpace on 2014-12-09T17:36:49Z (GMT). No. of bitstreams: 1 7021035.pdf: 4061566 bytes, checksum: 151a1414f2fbdab60062b9bba6f15bc0 (MD5) Previous issue date: 1970
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In vitro Selektion von Ribozymen für eine 1,3-dipolare Cycloaddition
… essentielle Reaktion gewählt - die 1,3-dipolare Cycloaddition. Kombinatorische RNA-Bibliotheken wurden nach aktiven Molekülen durchsucht, die eine Reaktion zwischen einem Acrylat- funktionalisierten RNA-Konjugat und einem biotinylierten Nitriloxid katalysierten. Dabei wurde die Methode der …
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Cycloaddition-fragmentation mediated pathways to ring D modified 19-norsteroids
… has been investigated. The approach is based on cycloaddition of methyl vinyl ketone to 3-methoxyestra-1,3,5(10),14,16-pentaen-17-yl acetate which proceeded with a high degree of regio- and stereoselectivity to give 16α-acetyl-3-methoxy-14, 17α-ethenoestra-1 ,3,5(1 O)-trien-17β-yl acetate. The …
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Doubly Bonded Derivatives of Si and Ge: Cycloaddition Reactions and Polymer Chemistry
… gave 5-membered ring adducts via a formal [3+2] cycloaddition where the (di)tetrelene acts as the 2p component and the nitro/nitrone act as the 4p component. In some cases, the ring underwent rearrengment or cleavage to give secondary products. Reactivity of (di)tetrelenes toward R2HP=O …
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Stereochemical Course of the Tandem [4+2]/[3+2] Cycloaddition of Nitroalkenes
The [4+2] cycloaddition of nitrobutene was further examined with both experimental and theoretical studies. Small, soft Lewis acids (such as Me 3Al) promote endo cycloaddition with the vinyl ether reacting in an s-trans conformation. Most other Lewis acids favor exo cycloaddition due either to …
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Studies on the synthesis of cyclohexynes for inter- and intramolecular cycloaddition reactions
… their reactivity in inter- and intramolecular cycloadditions. Several strategies were investigated to generate substrates for the intramolecular trapping of the cyclohexynes. In addition, simple cyclohexyne derivatives were prepared and two cases of intermolecular trapping are reported.
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Synthesis of nitrogen heterocycles via the intramolecular [4+2] cycloaddition of iminoacetonitriles
… anomeric effect. The substrates for these [4+2] cycloadditions are prepared from readily available alcohols via a Mitsunobu reaction with the previously unknown N-cyanomethyltriflamide (HN(Tf)CH₂CN) followed by cesium carbonate promoted elimination of trifluoromethanesulfinate. The a-amino …
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Synthesis of 3-aminocyclobutenones via [2 + 2] cycloaddition of ynamides and ketenes
… 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 alkynylation reaction …
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