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Showing 1 to 10 of 10 for “"Asymmetric Aldol"”.
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Lewis Base Activation of Lewis Acids in Asymmetric Aldol Reactions of Silyl Ketene Acetals
… chiral phosphoramide catalyzed/SiCl 4 promoted aldol reaction of silyl ketene acetals and silyl dienol ethers with aldehydes. The weakly acidic species, silicon tetrachloride (SiCl 4), is activated by binding of a strongly Lewis basic chiral phosphoramide, leading to in situ formation of a …
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Asymmetric synthesis of (+)-altholactone, a styryllactone from various goniothalamus species
… a RAMP-directed alkylation (ee > 98 %), an asymmetric aldol reaction (ee, de > 98 %) and a selective reduction (de > 96 %). The d-lactone, which is the main motif of the styryllactone family, results from an oxidation/in situ cyclisation sequence and the furanic cycle from an SN2 …
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Studies in asymmetric synthesis: I. the asymmetric α-alkylation of N,N-dimethylhydrazones II. the asymmetric aldol-Tishchenko reaction of (S)-tert-butanesulfinyl imines for the introduction of 2, 3, 4 and 5 new chiral centres in one pot
… on two different areas of research. Part 1 The asymmetric α-alkylation of ketones is one of the most fundamental yet challenging transformations in organic chemistry. Recently a new methodology to furnish enantiomerically enriched α-alkylated ketones was developed within the McGlacken group …
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New Methods for the Formation of Methyl Bearing Stereogenic Centers via Methylketene Dimerization and Free Radical Additions to Allyl Bromides
… involving allyl bromides. The first method, the asymmetric dimerization of methyl ketene, followed by an asymmetric aldol reaction and the appropriate functional group manipulations enabled us to construct the (2S, 4S, 6S) trimethylnonyl subunit found in the siphonariene class of natural …
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Synthese neuartiger Sulfonimidamide zur Anwendung in der asymmetrischen Katalyse
… envisaged with regard to their application in asymmetric catalysis. The first part of this work was dedicated to the synthesis of these highly oxidized sulfur compounds. Starting from sulfinic acid sodium salt and arylthiols, respectively, racemic and enantiopure sulfonimidamides were …
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Donor-Acceptor Cyclobutanes and Their Application for Heterocycle Synthesis and Progress Towards Biselide A
… an advanced stage intermediate included: Evans’ asymmetric aldol and a Prasad reduction to form a 1,3-syn diol exclusively which cyclized with Co(nmp)2 in high yield (93%). A tethering strategy will be used for the formation of the macrocyclic portion of the natural product.
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An excursion into the synthesis of novel flavanones
… new methodology for synthesizing flavanones asymmetrically in a manner that could be extended to the synthesis of novel indoloflavanone analogues. The designated approach was via an asymmetric aldol reaction catalysed by a chiral organocatalyst followed by an intramolecular Mitsunobu …
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Isomerization-Locked Alkene Analogues of Xaa–Pro Dipeptides in the Proteins Collagen and Bora
… We used the chiral catalyst, L-Thr, for asymmetric aldol addition to cyclopentanone, which inadvertently enhanced the yield of the wrong enantiomer, in contrast with aldol addition to cyclohexanone. A Mg2+-promoted Horner-Wadsworth-Emmons reaction afforded the (Z)-fluoro-alkene over the …
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Part A: Studies Towards Total Synthesis of an Anticancer and Antifungal Natural Product, Pseudolaric Acid B; Part B: Synthesis and Biological Evaluation of Berkeleyamide a and Its Derivatives
… from N-Boc- L-leucinal, employing Evans' syn-aldol reaction of N-acyl-4 R-benzyl oxazolidin-2-one as the key step. Excellent enantioselectivity (more than 95% ee) was obtained with a good yield (75%) for the crucial C-C bond formation key reaction step. In summary, our synthetic endeavor of …