Spelling suggestions: "subject:"bicyclic"" "subject:"dicyclic""
41 |
Radical approaches towards the synthesis of peptidomimetic templatesKapur, Neha January 2000 (has links)
No description available.
|
42 |
Iron (III) mediated ring expansion / cyclisation reactionsThompson, David Francis January 1995 (has links)
No description available.
|
43 |
Synthesis and Bioactivity Investigation of Bridged Bicyclic Compounds and a Mechanistic Investigation of a Propargyl Hydrazine Cycloaddition Catalyzed by an Ammonium SaltUnknown Date (has links)
We report the development of a general route to the synthesis of [4.3.1], [3.3.1],
an especially [3.2.1] bicyclic compounds structurally related to vitisinol D, a natural
product. This allows for diastereoselective synthesis of bicyclic compounds with
five adjacent chiral centers. This route was employed in a preliminary SAR
investigation into the neuroprotectant effect of small molecules in an in vivo
experiment measuring the degree of restorative effect of synaptic transmission in
the neuromuscular junction of Drosophila melanogaster larvae under acute
oxidative stress. One of the compounds exhibited intriguing potential as a
neuroprotectant and outperformed resveratrol in restoring synaptic function under
oxidative stress. The hypothesis that bridged bicyclic compounds may hold promise as drug scaffolds due to their conformational rigidity and ability to orient
functional appendages in unique orientations is developed.
The second focus is a mechanistic investigation into a tetrabutylammoniumcatalyzed
cycloaddition as evidence of a novel ammonium-alkyne interaction. A
carbamate nitrogen adds to a non-conjugated carbon–carbon triple bond under the
action of an ammonium catalyst leading to a cyclic product. Studies in
homogeneous systems suggest that the ammonium agent facilitates cyclitive
nitrogen–carbon bond formation through a cation–π interaction with the alkyne
unit. Using Raman spectroscopy, this cation–π interaction is directly observed for
the first time. DFT modeling elucidated the mechanistic factors in this
cycloaddition.
A teaching experiment was developed based on this mechanistic investigation.
Control experiments were employed to demonstrate the testing of two alternative
mechanistic hypotheses. Cyclization reactions were performed with a soluble base
(sodium phenoxide) with and without tetrabutylammonium bromide under
homogeneous conditions. Students observed that ammonium salt accelerates the
reaction. They were encouraged to develop a testable hypothesis for the role of
the ammonium salt in the cyclization mechanism: typical phase transfer or other.
IR spectroscopy was used to directly observe a dose dependent shift of the alkyne
stretching mode due to a cation−π interaction. Undergraduates were able to
employ the scientific method on a contemporary system and see how data are
generated and interpreted to adjudicate between rival hypotheses in a way that
emulates authentic and current research in a lab setting. / Includes bibliography. / Dissertation (Ph.D.)--Florida Atlantic University, 2018. / FAU Electronic Theses and Dissertations Collection
|
44 |
Synthetic Studies Toward Alloyohimbane and Louisianin DChen, Hung-Wei 09 June 2006 (has links)
We have developed an one-pot reaction procedure to cis-fused bicyclic glutarimides. Synthesis of (+/-)-alloyohimbane (4) and louisianin D (5) were completed.
|
45 |
Novel reactions of oxabicyclic compounds and reductive aldol cyclizations of activated alkynesLeung, Sze-kar., 梁詩嘉. January 2004 (has links)
published_or_final_version / Chemistry / Doctoral / Doctor of Philosophy
|
46 |
THE SYNTHESES AND POLYMERIZATION OF BICYCLIC UREA DERIVATIVES CONTAINING BRIDGEHEAD NITROGENEkechukwu, Oluchukwu Ebenezer January 1980 (has links)
In the present study, a new "anti-Bredt" bicyclic urea, 1,3-diazabicyclo[3·3·1]nonan-2-one, and an isomeric bond-bridged reference compound 1,8-diazabicyclo[4·3·0]nonan-9-one, were synthesized. The [3·3·1] urea was prepared in two ways. 3-Aminomethylpiperidine was reacted with phosgene. Deprotonation of the precipitated ammonium salt with triethylamine gave the urea. In another method, thermal depolymerization (in vacuo) of a glassy product arising from the reaction of 3-aminomethylpiperidine with diphenyl carbonate afforded the urea. The [4·3·0] urea was obtained through the reaction of diphenyl carbonate with 2-aminomethylpiperidine. No glassy intermediate was observed. The [4·3·0] and [3·3·1] ureas resisted hydrolysis. The former would not polymerize either in bulk or in solution at any temperature with or without initiator catalysts. At 120° and above the [3·3·1] urea bulk polymerized within 30 minutes with or without catalysts. The uncatalysed thermal polymerization gave lower molecular weight polymers in lower yield than the catalysed one. Cationic initiator, phenylphosphonic acid, and anionic potassium tertiary butoxide catalysts gave highest molecular weight polymers. Comparatively, the anionic initiator generated a higher molecular weight polymer than the cationic one. Dibutyltin oxide which is a coordination metal catalyst was also effective in generating high polymer but the yield compared favorably only with the uncatalysed thermal polymerization. The bulk polymerization of the [3·3·1] urea is one of the rare cases of polymerization of a bicyclo [3·3·1] nonan derivative. The mechanism proposed for the thermal polymerization of [3·3·1] urea involved the dissociation of the urea to an aminoisocyanate which then propagated the polymerization. The reaction of 3-aminopiperidine with diphenyl carbonate afforded a urea which was proposed to be a dimer of the desired urea, 1,6-diazabicyclo[3·2·1]octan-7-one. The unsuccessful syntheses of two ureas possessing two nitrogen bridgehead atoms, 1,5-diazabicyclo[3·2·1]octan-8-one, and 1,5-diazabicyclo[3·3·1]nonan-9-one, and another which was seven-membered, 1,3-diazabicyclo[3·2·2]nonan-2-one, were explained in terms of their canonical forms violating Wiseman's rule. However, a nuclear magnetic resonance (NMR) spectrum evidence of the formation of 1,5-diazabicyclo[3·2·1]octan-8-one in the NMR tube was presented.
|
47 |
METAL COMPLEXES OF BICYCLIC AMINESHilliard, Harold Marcus, 1928- January 1965 (has links)
No description available.
|
48 |
Synthesis of bicyclic thioketones as phototriggers for a liquid crystal based optical switchBradford, Rochelle Lee Fisher 08 1900 (has links)
No description available.
|
49 |
Nitrogen-directed free radical rearrangementsBebbington, Magnus W. P. January 2002 (has links)
This thesis describes efforts to develop new methods for the synthesis of bridged azacycles using nitrogen-directed free radical rearrangements. Free radical addition to 7-azanorbornadienes were carried out to give 7-substituted 2- azanorbornenes (Scheme a.l, X-Y = RS-H or PhSe-H). [illustration in text ...] Scheme a. 1 Nitrogen-directed homoallylic radical rearrangement via intermolecular radical addition. A conceptually novel and theoretically interesting nitrogen-directed neophyl rearrangement (Scheme a.2) was developed into a synthesis of 2- azabenzonorbornanes 2. [illustration in text ...] Scheme a.2 Nitrogen-directed neophyl-like rearrangement to 2-azabenzonorbornanes. In this case the radical 1 was generated by Barton deoxygenation of 7- azabenzonorbornanols. The effect on rearrangement of bicyclic core substitution and of aromatic ring electronics was probed in some detail, and the process was synthetically useful for a wide range of substrates. Variation of the protecting group on nitrogen was investigated and the product profiles from neophyl-like rearrangement were consistent with a process driven by the stability of a radical α to nitrogen as a result of SOMO-lone pair orbital interaction. The kinetics and mechanism of these processes are examined where appropriate, leading to estimates of rate constants for the rearrangements.
|
50 |
Contributions To The Chemistry Of Cyclotriphosphazanes And Bicyclic TetraphosphapentazanesThirupathi, N 07 1900 (has links) (PDF)
No description available.
|
Page generated in 0.0217 seconds