Chapter 1 highlights the many advantages of heterogeneous inorganic solids as catalysts, and summarises the various microporous and mesoporous solids that have been employed as catalysts. The synthesis and characterisation of the mesoporous materials that were used in the study are described. Chapter 2 focuses on the nitration of naphthalene. An introduction to nitration is given, and the results of nitration over a range of solids are presented. Unusual dinitronaphthalene product ratios were achieved over Al-MCM-41. Reactions catalysed by heteropoly acid immobilised within the pores of mesoporous materials are also described. Chapters 3 to 6 focus upon the alkylation of naphthalene. Emphasis is placed upon the importance of 2,6-dialkylnaphthalenes (2,6-DAN) as intermediates for the production of high performance engineering plastics, and why there is still significant room for improvement in both 2,6-DAN yield and selectivity. A molecular modelling study of 2,6- and 2,7- di-<I>tert</I>-butylnaphthalene (DTBN) highlighted the potential for achieving selectivity for the 2,6-over the 2,7-isomer. Zeolite H-Mordenite (HM) was the most selective catalyst for 2,6-DTBN, but showed poor activity. Efforts to increase both the 2,6-DTBN yield and selectivity over HM focused upon varying the reaction time; temperature; pressure; solvent; amount of alkylating agent, solvent, and catalyst; Si/Al ratio of the catalyst; and mode of addition. Optimisation resulted in a 60% yield of 2,6-DTBN with a 2,6/2,7 ratio of over 50. <I>tert</I>-Butylation reactions were achieved using mainly <I>tert</I>-butanol as the alkylating agent. The identification of by-products in the <I>tert-</I>butylation reaction has been attempted. Alkylation with other alkylating agents has been attempted, but selectivity for 2,6-DAN was inferior to that achieved in the <I>tert</I>-butylation reaction using <I>tert</I>-butanol.

Chapters one, two and three provide some introductory information including a detailed review of supported reagents (from 1978 to mid-1986). Chapter four describes the electrophilic activation of a series of different chlorine-containing compounds by the presence of silica gel, these include <i>tert</i>-butylhypochlorite, N, N-dichloramine-T, N, N-dichlorourethane and calcium hypochlorite. Their ability to chlorinate toluene in the ring is comparable to more traditional reagents (like Cl<SUB>2</SUB> in acetic acid). Optimal results are obtained with silica which is significantly acidic and which has been dried at 120<SUP>o</SUP>C. The application of such reagents extends from anisole to more deactivated substrates like biphenyl. Chapter five involves the utilization of a variety of aluminosilicate (zeolite) supports. Thus by careful consideration of structural parameters (Al/Si ratio, counter cations, pore and cavity size/shape, and conditions of activation) it is shown that <i>tert</i>-butylhypochlorite in the presence of H<SUP>+</SUP>, Na<SUP>+</SUP> Faujasite X produces highly <i>para</i>-selective monochlorinations (> 90% para) of monosubstituted benzenes. For example, chlorobenzene in acetonitrile (at 40<SUP>o</SUP>C) produces dichlorobenzene (92% isolated yield) with an isomer ratio of 97% para/3% ortho. Similarly, toluene is chlorinated at 25<SUP>o</SUP>C in dichloromethane/diethyl ether (1/3) to give monochlorotoluenes quantitatively with a p:o ratio of 91:9. Proton-exchanged forms of Faujasite with a low aluminium content (Si/Al > 2.4) give by-products resulting from Friedel-Crafts type alkylation reactions. Presence of the stronger acid sites responsible for this reaction change is confirmed by ammonia-temperature programmed desorption experiments. Chapter six deals with the evaluation of different N-chlorodialkylamines in the presence of silica gel as <i>ortho</i>-selective chlorinating reagents for phenols. For example, N-chloro bis (2-chloroethyl) amine in the presence of silica gel in tetrachloromethane solvent gives good mono- to di-chlorination ratios with high selectivity for the <i>ortho</i>- position in phenol (o/p ~ atop = 12.75). Chapter seven outlines some preliminary attempts to control the exo-endo isomer ratio in the 4π + 2π cycloaddition reaction between cyclopentadiene and acrylonitrile.

The sulfonation of some alkylbenzene homologues and isomers with sulfur trioxide gas has been studied in order to determine any differences in their reactivity. Relative rate kinetics has been used to demonstrate subtle differences in reactivity towards substitution on the benzene ring. A decrease in the relative rate is shown to be consistent with an increasing steric parameter in the alkyl chain. The results are discussed in terms of alkyl chain length and the degree of branching in the alkyl chain. Cleavage of a range of di-<I>p</I>-substituted diaryl sulfones has been shown to occur in concentrated sulfuric acid at elevated temperatures. The kinetics of these reactions was determined from second order rate plots, and the activation energies for the reactions were calculated from Arrhenius plots of the rate data over a range of temperatures. Two reaction mechanisms are postulated in which the initial step is protonation at the <I>ipso</I> position of one benzene ring. Plots of reaction rates <I>versus</I> σ<SUB>p</SUB><SUP>+</SUP> values for the various functional groups provide support for initial protonation at the most electron rich aromatic ring. The first oxidation of a range of symmetrical <I>para</I>-substituted diaryl sulfides is reported using potassium hydrogen persulfate (Oxone) in acetone/water under reflux without the use of a buffer. Preparative scale reactions were straightforward and afforded high isolated yields of the sulfone, with no sulfoxide.

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No description available.

Calculations have been carried out on the structures of donor-acceptor azobenzenes, phenylazothiophenes, benzylideneanilines and extended conjugated systems (incorporation benzene and thiophene connected by azo and amino bridges) using the AM1 and PM3 molecular orbital methods. The results show that AM1 method gives the best results overall when compared to the X-ray data, but the PM3 method tends to give better results for sulfur contain systems. The dipole moments, transition energies and molecular hyperpolarisabilities, of the donor-acceptor structure listed above, have been calculated by the CNDOSVB method from the optimised AM1 calculations. Analysis of the calculated results for the azo dyes shows a slight increase in hyperpolarisability when increasing the number of electron acceptors on the chromophore, but a substantial increase when benzene is replace by thiophene. The benzylideneanilines show similar effects as the azo dye, when the number of electron acceptor groups are increased, but the substitution of the thiophene ring into the benzylideneaniline system produces differing effects on the magnitude of the hyperpolarisability depending on whether it replaces the benzene ring attached to the electron donor or the benzene ring attached to the electron attracting groups within the chromophore. Attempts have been made to synthesise the molecules with the largest hyperpolarisabilities. These include azo dyes, 4-N,N-bis(2-hydroxyethyl)amino-2',4'-dinitroazobenzene and (3',5'-dinitrothiopheneazo)-4-[N,N-bis(2-hydroxyethyl)aniline] which were synthesised in 60 and 40% yields by coupling either 2,4-dinitroanilne or 2-amino-3,5-dinitrothiophene with N-phenyldiethanolamine respectively. Benzylideneanilines were also synthesised, including some promising examples such as N,N-diethyl-N-(p-nitrobenzylidene)-p-phenylenediamine and N,N-diethyl-N-[(5-nitrothien-2-yl) methylene]-p-phenylenediamine which were synthesised in 60-70% yields by either condensing p-nitrobenzaldehyde or 5-nitrothiophene-2-carboxaldehyde with N,N-diethyl-phenylenediamine respectively. More complex systems were also synthesised, including 4-{[4- (N,N-bis(2-hydroxyethyl)amino)phenyl]diazenyl}-N-[(4-nitrophenyl)methylene]aniline which was synthesised in a 45% yield by condensing the azo dye 4-N,N-bis(2-hydroxyethyl)amino-4'-aminoazobenzene with p-nitrobenzaldehyde.

The various inorganic solids that may be employed as heterogeneous catalysts in organic reactions are discussed in Chapter 1. In the present climate, heterogeneous catalysts are seen as more environmentally acceptable alternatives to homogeneous Lewis acid type catalysts. Chapter 2 describes the Friedel-Crafts acylation of aromatics. Discussion focuses on both the classical and solid catalysed reactions. The study of a pharmaceutical intermediate is described in Chapter 3. The aims of the work described were to develop an efficient and commercially viable process for the production of 1-(4-methoxyphenyl)-2-phenyl-1-butanone by the acylation of anisole over a suitable heterogeneous catalyst. In Part A of Chapter 4, the acetylation of a range of 1,2-disubstituted aromatics over solids is discussed. Part B describes the use of different anhydrides in the acylation of 2,3-dihydrobenzofuran over a number of solids to elucidate the generality of the reaction. Investigations show the influence of the solid catalyst and the effective recovery and regeneration of a zeolite catalyst. Finally, the acylation of 2,3-dihydrobenzofuran with ethyl oxalyl chloride over heterogeneous catalysts is described in Chapter 5. The reaction proved difficult with close consideration given to the reasoning behind the poor performance of the reaction; a good case in point being the amount of material unaccounted for in certain experiments. Investigations led to the isolation and characterisation of what were considered to be likely by-products of the reaction. Efforts were made to reduce the likelihood of such by-products being formed and with further attention, a yield of 73% of the corresponding <I>para</I> acylated product was formed in the presence of zeolite Hβ after 7 days. Having speculated that the difficulties encountered during the study of this reaction may lie with the nature of the acylating agent, the use of mixed anhydrides based on ethyl oxalyl chloride as potential acylating agents was investigated.

The first project involved the synthesis of a series of N-acyl-N-alkyl-4-amino[2.2]paracyclophane derivatives and the formation of their enolates. This was followed by the reaction of the enolates with a series of different electrophiles at low temperature in order to determine the diastereoisomeric selectivity which could be achieved by the use of a [2.2]paracyclophane unit as a chiral auxiliary. The project also examined the development of more complex chiral auxiliaries which utilised additional functional groups to enhance the diasterofacial shielding capability of the [2.2]paracyclophane unit. The second project involved the development of a synthesis for 4-amino-13-carboxy[2.2]paracyclophane. This would be a homochiral amino acid containing a chiral[2.2]paracyclophane unit which relied for its chiral properties not from a discrete chiral centre but from the planar chirality of the [2.2]paracyclophane.

Oxidation of a 2-(4"-hydroxybenzyl)-3-(3',4'dimethoxybenzyl) butyrolactone, using the hypervalent iodine reagents bis(trifluoroacetoxy) iodobenzene (PIFA) or iodobenzene diacetate (PIDA), results in the formation of 3-([1"-hydroxy-4"-oxo-2",5"cyclodienyl] methylene)-4-(3',4' dimethoxy benzyl)-2-(5H)-furanone in high yield. Treatment of 3-([1"-hydroxy-4"-oxo-2",5" cyclodienyl] methylene)-4-(3',4' dimethoxy benzyl)-2-(5H)-furanone with trifluoracetic acid results in rearrangement, to form 11-hydroxy-2-3 dimethoxy dibenzo[1a,4a:8a,12a] cycloocta-6-(hydroxymethyl)-7-(carboxylic acid) lactone, in quantitative yield. Hence we have achieved a highly efficient method to produce isostegane and stegane type lignans. Attempts to modify the oxidation of 2-(4"hydroxybenzyl)-3-(3',4'dimethoxybenzyl) butyrolactone, in order to produce the corresponding quinone methide, gave disappointing results. Oxidation of 2-(4"hydroxy 3",5" dimethoxybenzyl)-3-(3',4'dimethoxybenzyl) butyrolactone using silver complexes resulted in formation of 3',4'dimethoxybenzyl butrolactone. Oxidation of <I>cis</I>-3' hydroxy isoflavan-4-ol, to produce the corresponding pterocarpan, results in oxidation of both hydroxyls to produce a dimethoxy cyclohexadienone in acceptable yields.

No description available.