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Showing 1 to 20 of 72 for “"Acetal"”.
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Marcus Theory Applied To Acetal Cleavage And Aldol Reactions
… acid catalyzed and uncatalyzed hydrolysis of the acetal 2,2-dimethoxypropane (DMOP) and the ortho ester trimethylorthoacetate (TMOA) have been studied in aqueous solution at 25{dollar}spcirc{dollar}C. Theoretical and experimental evidence have been found for a base catalyzed E2 mechanism of DMOP …
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Lewis Base Catalysis: I. Catalytic Enantioselective Aldol Additions of Methyl Trichlorosilyl Ketene Acetal to Ketones. II. Catalytic Enantioselective Alpha-Additions of Isocyanides to Aldehydes
The first catalytic, enantioselective alpha-addition reaction of isocyanides has been demonstrated with a SiCl4·bisbinaphthyldiamine phosphoramide catalyst. Good yields have been obtained with aromatic, heteroaromatic, conjugated non-aromatic and non-branched aliphatic aldehydes. Aromatic, …
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The total syntheses of (+)-crotanecine, (-)-hastanecine and (-)-rosmarinecine utilizing the tandem (4+2)/(3+2) cycloadditions of nitroalkenes
… with dimethyl maleate. The resulting nitroso acetal (${-}$)-96 had all the required stereocenters for (${-}$)-hastanecine. The critical unmasking of the nitroso acetal (${-}$)-96 employed a hydrogenolytic cleavage to give the 1-azabicyclo (3.3.0) octane skeleton of (${-}$)-hastanecine.
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I. Solution Photochemistry of Camphor II. Synthesis and Solution Photochemistry of 2, 2-Dimethylcyclobutanone
… α-campholenic aldehyde. In ethanol a bicyclic acetal is also formed, while in n-heptane a bicyclic enol ether is formed instead of the acetal. Deuterium labelling experiments indicate that the acetal is formed by reaction of a bicyclic oxycarbene with ethanol, and that the enol ether is formed …
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Benzophenone Derivatives of Hexitols in tthe Carbohydrate Series
… structural problems. Benzoates, methyl groups, acetal groups, etc. have been used for this purpose. |For example, compounds of glucosides with aromatic aldehydes were synthesized by Ekenstein and Blanksma. These compounds were of interest because the aromatic group can be easily split off from …
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Development and applications of acid degradable polymeric materials
… features a simple glycerol-based acyclic acetal unit as a kinetic and thermodynamic trap for chain shattering. Thus, transient oxocarbenium ion formation with an organic acid induces intramolecular cyclization to depolymerize a polyurethane (PU) backbone at room temperature in anhydrous or …
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Computational analysis and partialsynthesis of resolvin analogues
… and, finally, a comprehensive trial of acetal deprotection methods for a 1,2 dioxane acetal in the presence of a silyl ether. Chapter 5 summarises the overall findings of this project and outlines possible future avenues for exploration. The full computational data set and experimental …
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Studies on lignin biosynthesis and structure
… of the lignin from the root tissue as its acetal derivative demonstrated the incorporation of the labelled feru1ic acid into the lignin component of the tissue. Through sim1lar administrations of (1-¹³C, 2-¹³C and 3-¹³C) ferul1c acid and subsequent analysis of the root tissues by solid …
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Synthetic Studies Towards the Gombaspiroketals and a Cobalt-Catalysed Epoxide Olefination
… allylation of allylsilane 45 and cyclic acetal 172 followed by epoxidation. This work describes efforts in the syntheses of allylsilane 45 and cyclic acetal 172. Towards allylsilane 45, the literature cuprate conjugate addition of bromide 54 with acrylate 55 was irreproducible, affording …
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PH-responsive polymeric materials for encapsulation and triggered release
… portion of the dissertation concerns a novel polyacetal that utilizes a new mechanism to facilitate degradation. A small molecule model compound containing the novel acetal moiety was synthesized and confirmed by NMR to show the expected degradation products under an acidic environment. Linear …
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Synthesis and characterization of stimuli-responsive microgels based on poly(glycidol)block copolymers
… of (Omega)-hydroxyl group of poly(glycidol acetal) using 2-chloropropionyl chloride fallowed by selective acidic deprotection of acetal groups. The obtained macroinitiators of different molar masses were successfully employed in ATRP of NIPAM and 4VP to give well-defined stimuli sensitive …
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Synthesis and Characterization of a Novel Polyacetal & Design and Preparation of Superhydrophobic Photocatalytic Surfaces
<p>Polyacetal polymers are thermoplastic resins that play an important role in industry because of numerous industrial applications including automobile; household appliance; <em>etc</em>. The first part of this thesis (Chapter 2) is about the synthesis of a new acetal copolymer that exhibits …
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Studies directed towards the total synthesis of (+)-sieboldine A
… can be transformed into the tetracyclic N,O-acetal which is two steps removed from the natural product 1. Efforts directed towards completion of the synthesis of 1 via a direct late-stage amine oxidation are presented ...
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Scope and stereochemistry of carbon-carbon bond formation via addition of carbon nucleophiles to nitrones
… addition of Grignard reagents and silyl ketene acetals to acyclic and cyclic nitrones have been studied. A 4:1 selectivity favoring axial addition was observed in the reactions of cis-3,5-dimethyl-2,3,4,5-tetrahydropyridine N-oxide with both methyl and phenyl Grignard reagents and the silyl …
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Conjugate Additions and Transposition of the Allylic Alcohols of Enol Ethers of 1, 2-Cyclohexanedione.
… alternative protective group the methoxymethyl acetal was prepared and studied. Alkylation of these derivatives was successful; however, the oxidation was problematic and although evidence for rearrangement was observed in one case, it did not provide the desired ketone.</p>
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Synthesis, structures and studies of organoiron compounds
… were obtained, respectively. A chiral acetal as the metalation-directing group was used to give stereoselectively (S)-α-carbomethoxyferrocenecarboxaldehyde after the hydrolysis of the acetal group. The aldehyde was then converted to the nitrile, and the ester group was converted to an …
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Design, Synthesis and Characterization of D-glucosamine Low Molecular Weight Gelators
… glucosamine derivatives. Several series of 4,6-O-acetal protected glucosamine derivatives were synthesized and screened for their gelation properties in several solvents.
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Intermediate compounds in the synthesis of lignin
… of salicylaldehyde were prepared. The methyl acetal, the sodium bisulfite addition product, and the 2,4-dinitrophenylhydrazone of benzaldehyde were also prepared.</p><p>The bisulfite addition of both aldehydes was found to be too unstable in the presence of aldehyde was recovered in each case. …
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The asymmetric synthesis of (2S,3R)-capreomycidine and the total synthesis of capreomycin IB
… of α-formylglycine dimethyl and diethyl acetals are described. This two-step approach employs a novel titanium enolate of a chiral glycinate, followed by addition of the requisite trialkyl orthoformate to provide a single diastereomer of the glycinate adduct. Hydrogenolysis provides the …
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A scalable protocol for the synthesis and use of neomenthyldiphenylphosphine.
… intermediates. We discovered that a benzylidene acetal templated the cyclization of electronically unbiased epoxy alcohols, such as 75, affording products with significant synthetic utility. Critical for high endo-selectivity was the use of silicon-dioxide based promoters.
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