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The Pummerer reaction, in which thionium ions are re generated and react with nucleophiles, has evolved into a valuable tool for synthesis. We have developed a connective route to thionium ions that has several advantages over the traditional route from sulfoxides. The process utilises widely-available thiol and aldehyde starting materials, negating the need to prepare sulfoxide or sulfide starting materials (activated sulfides are essentially prepared in situ). In addition, the properties or structural features of the thiol and aldehyde substituents are united in a single synthetic operation, with concomitant addition of a nucleophile.

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The modelling of chemical and biochemical systems is highly dependent on the reaction network of the system. A reaction network should contain all the reactions which can occur in addition to the species involved. However in many cases there will be reactions occurring which are missing from the network. These are called gaps (Reed et al., 2003; Duarte et al, 2004) and occur because the databases of reactions used to build them are incomplete. The main aim of this work is to identify all the reactions which can occur in a given system including the unknown ones. This is accomplished through a new procedure which will be called metabolic network development and is aimed at constructing reaction networks for biochemical systems.

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The homogeneous hydrogenation of esters and related compounds has been achieved by a catalyst-generated in-situ from the precursors Ru(acac)(_3) and the tripodal phosphine ligand l,l,l-tris(diphenylphosphinomethyl)ethane (Triphos). The catalyst is susceptible to deactivation in the presence of primary alcohols by their dehydrogenation to an aldehyde, which is subsequently decarbonylated to produce the [Ru(Triphos)H(_2)(CO)] complex, characterised by (^1)H and (^31)P NMR spectroscopy, elemental analysis, IR and X- ray crystallography. The co-ordinated carbonyl ligand of [Ru(Triphos)H(_2)(CO)] effectively blocks the co-ordination site required by the substrate for further hydrogenation, thus deactivating the catalyst. Reactivation of the deactivated catalyst can be achieved, by introducing water to the reaction mixture, and removing the carbonyl ligand through the water gas shift reaction. The inclusion of water within the reaction solvent results in catalyst reactivation during the hydrogenation process. Investigation of the hydrogenation of alkenes, in the absence of reagents susceptible to decarbonylation, resulted in the isolation of the solid dinuclear complex [(Triphos)RuH(μ-H)(_2)HRu(Triphos)], which was characterised by X-ray crystallography and (^31)P NMR spectroscopy. Its information suggests that the active catalyst is [Ru(Triphos)H(_2)].The separation of the products from the catalyst and unconsumed reactants has been achieved by distillation of the product solution of the hydrogenation reaction. The recovered catalyst is sufficiently robust to be capable of multiple recycles, replicating the original and repeated result without loss of activity or selectivity.

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No description available.

No description available.