Thesis (Ph.D.) -- McMaster University, 2001. / Includes bibliographical references (leaves 242-263). Also available via World Wide Web.

Thesis (Ph. D.)--McMaster University, 2003. / Advisor: M. McGlinchey. Includes bibliographical references (leaves 182-195). Also available via World Wide Web.

The existence of the reactive intermediate trans-10b,10c-dimethyl-10b,10c-dihydropyr-1-yne, 57, generated via dehydrobromination, was proved by trapping with N,N-diethyl-1,3-butadienylamine, furan and a series of isoannelated furans. Comparison of 57 with benzyne, 1, was implemented using the results of MMX/PCMODEL calculations. A fast route to annelated dihydropyrenes was developed via the reactive intermediate 57. Through this route, five annelated dihydropyrenes, namely, trans-14b,14c-dimethyl-14b,14c-dihydronaphtho (2,1,8-gra) naphthacene, 204, trans-16b,16c-dimethyl-16b,16c-dihydrobenzo (a) naphtho (2,1,8-fgh) naphthacene, 206a, trans-16b,16c-dimethyl-16b,16c-dihydrobenzo (a) naphtho (2,1,8-hij) naphthacene, 206b, trans-14b,14c,18b,18c-tetramethyl-14b,14c,18b, 18c-tetrahydrodinaphtho (2,1,8-uva; 2,1,8-jkl) pentacene, 224a, and trans-15b,15c,18b,18c-tetramethyl-15b,15c,18b, 18c-tetrahydrodinaphtho (2,1,8-uva; 2,1,8-pon) pentacene, 224b, and one bridged oxa (17) annulene, namely, trans-11b,11c-dimethyl-11b,11c-dihydropyreno (1,2-c) furan, 222, were synthesized. Metal complexation of the benzo (a) dihydropyrene 95 was investigated. This led to the first two metal dihydropyrene complexes, namely, (7,8,9,10,10a,10b-η6)-trans-12b,12c-dimethyl-12b,12c-dihydrobenzo (a) pyrenechromium(0)-tricarbonyl, 239, and (1,2,3,3a-η4) -trans-12b,12c-dimethyl-12b,12c-dihydrobenzo (a) pyreneiron(0)tricarbonyl, 209. The delocalization effects due to complexation were studied. Combining the results of the newly synthesized annelated dihydropyrenes with previously obtained ones, a series of correlations between theoretical calculations and experimental results, such as bond order vs. chemical shift, bond order vs. coupling constant, and ring current vs. chemical shift were devised. The ortho-metalation of dihydropyrene derivatives and synthesis of 1-bromo-2-fluoro-dihydropyrene were attempted. This led to two new dihydropyrene derivatives, namely, trimethylacetamino-trans-10b,10c-dimethyl-10b,10c-dihydropyrene, 99, and 2-diethylcarbamyl-trans-10b,10c-dimethyl-10b,10c-dihydropyrene, 109, and two new cyclophane derivatives, namely, syn-5-bromo-6-fluoro-9,18-dimethyl-2,11-dithia (3.3) metacyclophane, 131a, and anti-5-bromo-6-fluoro-9,18-dimethyl-2,11-dithia (3.3) metacyclophane, 131b. / Graduate

M.Sc. (Chemistry) / The aim of this study was to investigate the oxidation of aromatic compounds and benzylidene acetals with dimethyldioxinne. Dimethyldioxirane, either by Insitu preparation or in the isolated form, has shown remarkable reactivity. This oxidant is effective in oxygen transfer, readily prepared from commercial materials and reacts under mild conditions. Quinones are natural materials with biological activity and some are key intermediates in the synthesis of medicines. A well-known method for the preparation of quinones, is the oxidation of phenols and aromatic ethers. The oxidation of simple phenol and anisole derivatives by dimethyldioxirane yielded complex mixtures. More hindered aromatic compounds were investigated, since the oxidation of these compounds proceeded in a more controlled manner. In this study the phenols were found to be more reactive than the corresponding aromatic ethers. para-Quinones were formed preferentially, whereas ortho-quinones were observed in one or two cases. Products formed in these oxidations depend on the substitution pattern of the substrate. The oxidation of phenols and aromatic compounds formed complex mixtures and does not have many synthetic applications. Mechanisms are proposed for the formation of the different products. Benzylidene acetals are important protecting groups in the chemistry of carbohydrates. Cleavage of these benzylidene acetals gave either the free diol or benzyl ether or benzoyl ester, depending on the reagent used. The reaction of dimethyldioxirane with benzylidene acetals gave the benzoylesters. With dioxanes, e.g. 4,6-O-benzylidene sugar derivatives, there are no difference in stereoelectronic effects in the cleavage of C-4 and C-6. The major product has a 6-benzoate group, probably due to the greater stability of the primary benzoate. In dioxolanes both reactivity and regioselectivity of the reactions are influenced by stereoeleetronic effects. It has been found that the cleavage of dioxolanes took place preferably in a conformation where the oxygen is antiperiplanar towards the leaving group. It has been shown that dimethyldioxinme can be used with success in the deprotection of benzylidene acetals in the chemistry of carbohydrates.

No description available.

In Part I, the C.D. spectra of a number of 3-keto and 20-keto steroids are reported. The 3-keto steroids were comprised of two series of compounds. For one series, the conformationally transmitted effects of olefinic centers located in, or exocyclic to, rings B and C were investigated. It was found that these effects were reflected in the C.D. spectra when the double bond was located in ring B, but not when the double bond was located in ring C. Further, no correlation could be made between the relative rates of alkali-catalyzed benzaldehyde condensation and the C.D. data. For the other series, the conformations of ring A in a number of steroids substituted at the 2- and 4- positions are discussed. The C.D. results are in agreement with other evidence on this subject, and suggest that a 1,3-diaxial methyl interaction leads to flattening of ring A. For the Δ⁵- 4,4-dimethyl-3-keto steroids, a non-chair conformation is indicated, but a distinction between a boat and a flat chair conformation cannot be made . For 2 α -bromo-4,4-dimethylcholest-5-en-3-one, a conformational equilibrium is suggested. The 20-keto steroids were comprised of a large number of 16-substituted pregnanone and 17 α -pregna-none derivatives. The C.D. spectra of the 16,17 trans compounds and the 16α , 17α -cis-compounds were similar to those of the 16-unsubstituted parent compounds. Modifications in rings A and B had little effect upon the dichroism of the 20-keto group. The C.D. spectra of the 16β, 17β-compounds were very sensitive to the nature of the 16β -substituent, These results are interpreted in terms of the preferred conformation of the 17β -acetyl group. Finally, the C.D. spectra of a number of 16, 17-epoxy-20-keto steroids are reported and discussed with reference to the "reversed octant rule". In Part II, the structural determination of the mould metabolite, hirsutic acid C, is reported. The functional groups were established from chemical information; however the X-ray analysis of the p-bromo-phenacyl ester was required to reveal the novel ring system. During the X-ray irradiation an unusual solid-phase rearrangement occurred, transforming the α-epoxy hydroxyl system of p-bromophenacyl hirsutate to a β -hydroxy ketone system without disrupting the crystal structure. The X-ray analysis revealed a 50:50 mixture of starting material and rearrangement product. A combination of the X-ray and the chemical data was required to complete the structural determinations of both products. The generality of the rearrangement process was investigated. It occurred with methyl hirsutate and dihydromethylhirsutate, but not with hirsutic acid. It could not be induced thermally. It did not occur with the steroids 3 α - and 3 β -hydroxy-4 β, 5-epoxy-5β-cholestane. The rearrangement process is probably controlled by the nature of the molecular packing and hydrogen-bond formation. In Part III, the biogenetic-type syntheses of a number of acetate-derived aromatic compounds are reported. A discussion of the preparation of the condensed polypyrone intermediates is given, and in particular the synthesis of the tetrapyrone, 4-hydroxy-9-methyl-2,5,7,12-tetraketo 1,6,8,11-tetra-oxachrysene from the condensation of bis (2,4-dichlorophenyl) malonate and the tripyrone, 7-methyl-1-hydroxy-3,5,10-triketo 4,6,9-trioxaphenanthrene is reported. Treatment of the tripyrone with methanolic potassium hydroxide solution resulted in ring opening to form a poly- β-keto chain, and subsequent aldol-type condensation to give aromatic compounds representative of the naturally-occurring 6,8 dihydroxy-isocoumarins and C-acetylorsellinic acid. Treatment with methanolic magnesium methoxide solution gave aromatic compounds derivable from different cyclization modes of the poly- β-keto chain. Among the compounds isolated were two representative of the naturally-occurring curvulinic acid and the 5,7-dihydroxychromones respectively. Structural assignments were made largely on the basis of the characteristic spectral properties of the compounds. / Science, Faculty of / Chemistry, Department of / Graduate

No description available.

published_or_final_version / Chemistry / Master / Master of Science

published_or_final_version / Chemistry / Master / Master of Science

Dehydroaromatization of methane (MDA) reaction was investigated over platinum modified Mo/H-ZSM-5 catalysts which were pre-carbided at 750 oC. The influence of platinum on the catalytic performance and product selectivity of Mo/H-ZSM-5 catalysts for the MDA reaction at 700 oC was studied. The presence of platinum led to a slight decrease in methane conversion. As the platinum loading increased, the methane conversion decreased further and the catalytic stability increased with time-on-stream (TOS) during the MDA reaction. Aromatic selectivities above 90% were obtained with catalysts containing low platinum loadings (0.5 and 1.0 wt.%), with benzene being the most prominent product. A decrease in coke selectivity and coke deposits was noted with the platinum modified Mo/H-ZSM-5 zeolite catalysts. A comparative study was performed to compare platinum, palladium and ruthenium promoted Mo/H-ZSM-5 zeolite catalysts with un-promoted Mo/H-ZSM-5. The ruthenium promoted catalyst proved to be superior in catalytic performance, with a higher methane conversion obtained than found for platinum promoted and palladium promoted Mo/H-ZSM-5 catalysts. Benzene selectivity of about 60% was obtained for ruthenium and palladium promoted Mo/HZSM- 5 catalysts and the total aromatic selectivity was maintained at 90%. TGA results showed a total reduction of 50% by weight of carbon deposited on the promoted Mo/H-ZSM-5 catalyst. Dehydroaromatization of methane was studied over tin modified Pt/Mo/HZSM-5 catalysts and compared to Pt/Mo/H-ZSM-5 catalyst at 700 oC. Addition of tin decreased the activity towards methane aromatization. However, the formation of aromatic compounds was favoured. The CO FT-IR adsorption and CO chemisorption techniques showed that the catalyst preparation method had an effect on the catalytic performance of tin modified Pt/Mo/H-ZSM-5 catalysts. High aromatic selectivity and low coke selectivity were obtained with co-impregnated and sequentially impregnated Pt/Sn catalysts. While a decrease in the formation rate of carbonaceous deposits is mainly dependent on the availability of platinum sites for the hydrogenation of carbon. The order of sequentially loading platinum and tin has an effect on the electronic and structural properties of platinum as shown by XPS and FT-IR studies. CO chemisorption and the FT-IR adsorption studies showed that addition of tin decreased the adsorption capacity of the platinum surface atoms. Catalyst preparation methods and successive calcination treatments affected the location of both tin and platinum atoms in the catalyst. Catalysts prepared by the coimpregnation method showed a good platinum dispersion, better than found for the sequentially impregnated catalysts. The MDA reaction was carried out at 800 oC over manganese modified H-ZSM-5 zeolite catalysts prepared by the incipient wetness impregnation method. The effect of a number of parameters on the catalytic performance and product selectivity was investigated, such as reaction temperature, manganese precursor-type, tungsten as promoter, manganese loading and use of noble metals. The study of the effect of reaction temperature showed that the methane conversion increased linearly with increase in reaction temperature from 700 to 850 oC. The selectivity towards aromatic compounds (of about 65%) was attained for the reactions performed at 750 and 800 oC. Formation rate of carbonaceous deposits increased linearly with increase in reaction temperature. The use of different manganese precursors to prepare Mn/H-ZSM-5 catalysts had an effect on both the catalytic behaviour and the product distribution. High catalytic activities were obtained for the catalysts prepared from Mn(NO3)2 and MnCl2 salts. However, the product distribution was significantly different, with the Mn(NO3)2 catalyst being more selective towards aromatic compounds while the MnCl2 catalyst was more selective toward coke. The effect of manganese loading was studied at 800 oC and an optimum catalyst activity was obtained at 2 and 4 wt.% manganese loadings. The aromatic selectivity above 70% and coke selectivity of 20% were obtained for a 2 wt.% loaded catalyst. Addition of tungsten as a promoter onto the 2 wt.% loaded catalyst (2Mn/H-ZSM-5) lowered the catalytic activity but the catalyst remained fairly stable with increase in TOS. Tungsten modified catalysts favoured the formation of carbonaceous deposits over aromatic compounds. TGA results showed a coke deposit of 164 mg/g.cat, an 88% increase in coke deposit when tungsten was used a promoter. Noble metals were added to reduce the total amount of coke on the tungsten modified Mn/H-ZSM-5 catalysts. The presence of a noble metal favoured the formation of aromatic compounds and suppressed the formation of coke. Platinum and ruthenium promoted catalysts were the active catalysts and aromatic selectivity increased from 12% to 55% and 46% respectively. A reduction in the total amount of coke deposit on the platinum promoted catalyst (42%) and the ruthenium promoted catalyst (31%) was noted.