No description available.

This thesis describes the syntheses of some polyfunctionalised cyclopentanes via intramolecular aldol condensations of sugar δ-lactone precursors. The known azido carbpcycle (1S,2R,3S,4R,5R)-methyl [5-azido-1,2,3,4- tetrahydrpxy-2,3-O-isopropylidene-cyclopentane] carboxylate was prepared from 2- deoxy-2-iodo-3,4:6,7-di-O-isopropylidene-D-glycero-D-talo-heptono-1,5-lactone in five steps. The key reaction was a base-induced intramolecular aldol cyclisation of a 5- iodo-formyl-2,6-lactone. Borohydride reduction of the methyl ester gave an azido triol. Deprotection followed by reduction of the azide functionality produced an amino pentol. The analogous tetrahydroxy β-amino acid was synthesised from the azido carbocycle in three steps. The inhibitory activity of the amino pentol against human liver glycosidases is reported. Two azido bicyclic lactones, (1R,4R,5R,6R,7R)-4-azido-5,6,7-trihydroxy-5,6-0- isopropylidene-2-oxa-bicyclo[2.2.1]heptan-3-one and (1S,4S,5R,6R,7R)-4-azido- 5,6,7-trmydroxy-5,6-O-isopropydilene-2-oxa-bicyclo[2.2.1]heptan-3-one, were prepared from 3,4:6,7-di-O<./em>-isopropylidene-D-glycero-D-talo-heptono-1,5-lactone in five steps. The (1R,4R,5R,6R,7<em.R)-compound was further elaborated to give an amino pentol via a series of borohydride reduction / deprotection / catalytic hydrogenation. A novel carbocyclic spirohydantoin was synthesised by two alternative routes. The second route also provided access to an N'-phenyl spirohydantoin. The inhibitory activities of the amino pentol and the spirohydantoin against human liver glycosidases are reported. The azido bicyclic lactone triol (1R,4S,5R,6R,7R)-4-azido-5,6,7-trihydroxy-2-oxabicyclo[ 2.2.1]heptan-3-one underwent reduction of the azide functionality with concomitant epimerisation to give the (5S)-epimeric amine. The structure of this material was confirmed by X-ray diffraction analysis of a crystalline derivative. Treatment of the azido triol with base under non-aqueous conditions resulted in a retroaldol reaction to give the (5S)-epimeric azide, the relative configuration of which was determined by single crystal X-ray analysis. A third ketal protected azido bicyclic lactone was prepared via a base-induced retro-aldol epimerisation. Five tetrahydroxycyclopentane α-amino acids, including a pair of enantiomers, were synthesised from the azido bicyclic lactones. The structures of two of the α-amino acids were established by X-ray crystallographic analysis, whilst the enantiomeric compounds were identified using circular dichroism spectrometry. The diketal protected (2R,3R,4R,5R)-tetrahydroxy-cyclopentane α-amino acid was incorporated into six oligopeptides. Peptide coupling at the C-terminus of the carbocyclic amino acid was carried out using two amino acid tert-butyl esters. Chain extension at the N-terminus was achieved by reaction with N-benzyloxycarbonyl protected amino acids in the presence of 1-(3-dimethylaminopropyl)-3-ethyl-carbodiimide hydrochloride as the carbodiimide reagent. Complete deprotection of a tetrapeptide is described.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1984. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 323-333).

No description available.

A variety of organometallic-fused heterocycles and acene quinones were prepared and characterized. This work was divided into three parts: first, the synthesis of 5,5-fused heterocyclic complexes of tricarbonylmanganese and (1’,2’,3’,4’,5’-pentamethylcyclopentadienyl)ruthenium; second, the synthesis of 1,2-diacylcyclopentadienyl p-cymene complexes of ruthenium(II); and third, synthesis of cyclopentadienyl-fused polyacenequinone complexes of ruthenium, iron and manganese. The first examples of the convenient, versatile and symmetric cyclopentadienyl-fused heterocycle complexes of (1’,2’,3’,4’,5’-pentamethylcyclopentadienyl)ruthenium(II) and tricarbonylmanganese(I) were synthesized starting from (1,2-dicarbophenoxycyclopentadienyl)sodium. The sodium salt was transmetalated using [MnBr(CO)5] and 1/4 [Ru(μ3-Cl)(Cp*)]4 to give [Mn(CO)3{η5-C5H3(CO2Ph)2-1,2}] and [Ru{η5-C5H3(CO2Ph)2-1,2}(Cp*)]. The diester complexes were saponified under basic conditions to obtain the corresponding dicarboxylic acids. The dicarboxylic acids were used to synthesize unique cyclopentadienylmetal complexes including diacyl chlorides, anhydrides, thioanhydrides and p-tolyl imides of ruthenium and manganese. Similarly, a series of 1,2-diacylcyclopentadienyl-p-cymene cationic complexes of ruthenium were synthesized using thallium salt of 2-acyl-6-hydroxyfulvene and [Ru(η6-p-cymene)(μ-Cl)Cl]2 in a 2:1 ratio with an intension of converting them into heterocycle-fused cationic sandwich complexes. However, our attempts of ring closing on 1,4-diketons with sulfur or selenium were unsuccessful. A methodology involving the synthesis of metallocene-fused quinone complexes was employed starting from pentamethylruthenocene-1,2-dicarboxylic acids. The diacyl chloride was prepared in situ from the dicarboxylic acids and used for Friedel-Crafts acylation. We observed single-step room-temperature diacylation of aromatics, including benzene, o-xylene, toluene, 1,4-dimethoxybenzene and ferrocene with pentamethylruthenocene-1,2-diacyl chloride to obtain the corresponding quinone complexes. Similarly, we synthesized mononuclear and binuclear γ-quinones by aldol condensation of 1,2-diformylcyclopentadienylmetal complexes with cyclohexane-1,4-dione or 1,4-dihydroxyarenes. The third methodology involves the Friedel-Crafts acylation of ferrocene with 2-carbomethoxyaroyl chlorides followed by saponification, carbonyl reduction, and ring closing by second Friedel-Crafts acylation to give Ferrocene-capped anthrone-like tricyclic and tetracyclic ketones. The oxidation of the ketones gave [3,4-c]-fused α-quinone complexes of iron. The oxidative and reductive coupling, enolization and C-alkylation of the anthrone complex were studied. Solvolysis of α-carbinol gave α-ferrocenylcarbenium salt, which underwent dimerization on treatment with non-nucleophilic base. We were successful to trap the in situ generated trimethylsilylenol ether of ferrocene-anthrone using dienophiles like N-phenylmaleimide or dimethylacetylenedicarboxylate under Diels-Alder conditions.

<div>Biomass-derived fuels have long been considered as a possible replacement for traditional liquid fuels derived from petroleum. However, biomass as a feedstock requires significant refinement prior to application as a liquid fuel. The H2Bioil process has previously been proposed in which biomass is pyrolyzed and the resulting vapors are passed over a catalyst bed for upgrading to hydrocarbon products in a hydrogen environment [1]. A PtMo catalyst has been developed for the complete hydrodeoxygenation (HDO) of biomass pyrolysis vapors to hydrocarbons [2]. However, the product hydrocarbons contain a large fraction of molecules smaller than C4 which would not be suitable as liquid fuels. In fast hydropyrolysis of poplar followed by hydrodeoxygenation over a PtMo/MWCNT catalyst at 25 bar H2 and 300oC, only 32.1% of carbon is captured in C4 – C8 products; 21.7% of carbon is captured in C1 – C3 hydrocarbons [2]. Here, approaches are examined to increase selectivity of H2Bioil to desired products. Aldol condensation catalysts could be used prior to the HDO catalyst in order to increase the carbon number of products. These products would then be hydrodeoxygenated to hydrocarbons of greater average carbon number than with an HDO catalyst alone. Application of a 2% Cu/TiO2 catalyst to a classic aldehyde model compound, butanal, shows high selectivity towards aldol condensation products at low H2 pressures. In more complex systems which more closely resemble biomass pyrolysis vapors, this catalyst also shows significant yields to aldol condensation products, but substantial carbon losses presumed to be due to coke formation are observed. Both glycolaldehyde, a significant product of biomass pyrolysis, and cellulose, a component polymer of biomass, have been pyrolyzed and passed through aldol condensation followed by hydrodeoxygenation in a pulsed fixed-bed microreactor. Glycolaldehyde aldol condensation resulted in the formation of products in the C2-C¬9 range, while the major aldol condensation products observed from cellulose were C7 and C8 products. Carbon losses in glycolaldehyde aldol condensation were reduced under operation at increased hydrogen partial pressures, supporting the hypothesis that increasing selectivity to hydrogenation products can reduce coke formation from primary aldol condensation products. </div><div>The use of feeds which have undergone genetic modification and/or pretreatment by other catalytic processes may also lead to improvements in overall product selectivity. The influence of genetic modifications to poplar lignin on the pyrolysis plus HDO process are investigated, and it is found that these materials have no effect on the final product distribution. The product distribution from a poplar sample which has had lignin catalytically removed is also examined, with the conclusion that the product distribution strongly resembles that of cellulose, however the lignin-removed sample shows high selectivity towards char which is not seen from cellulose. </div><div><br></div>

Thesis (Ph. D.)--Brigham Young University. Dept. of Chemistry and Biochemistry, 2007. / Includes bibliographical references.

<p></p><p>Biomass and shale gas have been proposed as alternate sources of liquid hydrocarbon fuels. Traditional petroleum refining, however, is not capable of directly converting either the highly oxygenated molecular structure of lignocellulosic biomass or the low molecular weight alkanes of shale gas into liquid fuels. In this work, we investigate two processes to generate fuels by upgrading low molecular weight species present in biomass pyrolysis vapors and in shale gas via carbon-carbon coupling reactions of low molecular weight species present in biomass pyrolysis vapors and shale gas. </p> <p>In the first process, fast pyrolysis and hydrodeoxygenation are used to convert woody biomass into hydrocarbons. However, 22% of the carbon in this process forms C₁-C₃ species which are unsuitable for use as liquid fuels. Aldol condensation has been proposed as a means of leveraging carbonyl groups present in the pyrolysis product distribution prior to hydrodeoxygenation in order to couple low molecular weight species such as glycolaldehyde to transform the C₁-C₃ fraction into C₄₊ species. We demonstrate that aldol condensation of fast pyrolysis vapors results in a large (10%) reduction in carbon yield to C₆ species and only a small (5%) reduction in carbon yield to C₁-C₃ species to form C₇₊ products, suggesting that higher molecular weight species undergo significant reaction over the aldol condensation catalyst. We demonstrate a pathway by which levoglucosan can be converted into levoglucosenone, which then forms C₇₊ species through self-aldol condensation and condensation with light oxygenates. </p> <p>In the second process, light olefins in shale gas, consisting primarily of ethane and propane, are dehydrogenated and oligomerized into higher molecular weight species. Ni cation sites exchanged onto microporous materials catalyze ethene oligomerization to butenes and heavier oligomers, but also undergo rapid deactivation. The use of mesoporous supports has been reported in the literature to alleviate deactivation in regimes of high ethene pressures and low temperatures that cause capillary condensation of ethene within mesoporous voids. Here, we reproduce prior literature findings on mesoporous Ni-MCM-41 and report that, in sharp contrast, reaction conditions that nominally correspond to ethene capillary condensation in microporous Ni-Beta or Ni-FAU zeolites do not mitigate deactivation, likely because confinement within microporous voids restricts the formation of condensed phases of ethene <a>that are effective at solvating and desorbing heavier intermediates that are precursors to deactivation</a>. Deactivation rates are found to transition from a first-order to a second-order dependence on Ni site density in Ni-FAU zeolites with increasing ethene pressure, suggesting a transition in the dominant deactivation mechanism involving a single Ni site to one involving two Ni sites, reminiscent of the effects of increasing H₂ pressure on changing the kinetic order of deactivation in our prior work on Ni-Beta zeolites.</p><br><p></p>

No description available.

Atmospheric aldol self-reactions of octanal, heptanal and hexanal in a range of aqueous H2SO4 w/v% concentrations as a catalyst were studied in both bulk liquid-liquid experiments and gas-liquid experiments. Initially, a new practical methodology was developed and enhanced to monitor aldol reactions in aqueous acidic media. The evaluation of a quenching and extracting method were performed, confirming the suitability, reliability and reproducibility of the extraction method. In bulk studies, aldol products of the three aldehydes were separated and identified by preparative HPLC, GC-MS and NMR. The major aldol products observed at high acid concentrations were alpha,β-unsaturated aldehyde (dimer), trialkyl benzene (trimer) and tetraalkylcycloocta-tetraene (tetramer). The trimer of octanal was formed as trioxane in low sulfuric acid concentration and the possible mechanism accretion reaction pathways of high and low acid concentrations are proposed in this study. A systematic kinetic study of octanal, heptanal and hexanal in the bulk experiments at 65, 60 and 55 w/v% H2SO4 at 294 K were monitored using gas chromatographic equipped with a flame ionisation detector (GC-FID). The rate constants were generally estimated using second order kinetics and observed to increase as a function of sulfuric acid concentrations and also as the chain length of aliphatic aldehyde increased. The aldol self-reaction in the bulk experiment was too fast at room temperature to be easily measured using a quenching method therefore attempts were made to follow the reaction at low temperature (0 °C). The result at low temperature indicated that the rate constant of aldehyde was reduced but there was an issue of rapid rise in temperature as a result of mixing concentrated sulfuric acid with aqueous solution of the aldehyde. A gas bubbling system was developed which better simulates atmospheric reality, and which also resolves the issue of temperature rise on mixing. Two different methodologies were used: one in which the aldehyde was continually added, and one where a fixed amount was added from the gas phase and the reaction was then allowed to proceed, monitored at selected time intervals. The precision and accuracy of the fixed method was then further improved by the addition of an internal standard (IS). Using this, the concentrations of aliphatic aldehydes (C6-C8) were calibrated using an experimentally determined response factor and used to follow the loss of the reactant aldehydes. Similar methods were applied to the aldol dimers (C6-C8), which were purified and used to calibrate the chromatographic response. The rate constant for octanal, heptanal and hexanal at 76 wt% and 294 K were 0.0969 M-1 s-1, 0.1497 M-1 s-1 and 0.2622 M-1 s-1 respectively. There are some observations based upon the results presented in this thesis that may be of atmospheric significance: (i) phase separation between organic and aqueous layers in both the bulk experiment and in the bubbling system; (ii) the acid strength dependence and concentration-dependence of the various products; (iii) the faster rates than previously reported, and variation between bulk and bubbling; and (v) the time-dependent colour changes. Further work to explore these observations is proposed.