Catalytic Studies Of Titanium Oxide Clusters In Claisen-Schmidt Condensation Reactions

Polyoxometalates (POMs) are metal oxide molecules with structural diversity and excellent catalytic activity. They have been applied in many fields. Polyoxotitanate (POT) is a branch of POM. Catalytic applications of POTs were seldom studied although large amounts of works about synthesis have been performed. Claisen-Schmidt reaction is a typical strategy to systhesize a, a’-bis-substituted alkanones. Other Lewis acid catalysts have many diadvantages of poor selevtivity, inconvenience of post-treatment, toxicity and expensive. In this thesis, we applied POTs to Claisen-Schmidt condensation reaction to systhesize a, a’-bis-substituted alkanones, resulting in high effiency and chemoselectivity. The mechnism in the reaction and the relationship of POTs structure and Lewis acid catalytic activity are also involved.In Chapter 1, the structures and the applications of POM were introduced, as well as structures of POTs. Analogues of curcumin (especially a, a’-bis-substituted alkanones) have many advantages in biological and pharmacy application. Traditional catalysts in Claisen-Schmidt condensation reactions are also described.In Chapter 2, a dinuclear titanium alkoxide cluster (Ti2) is applied to catalyze the Claisen-Schmidt condensation reaction, resulting high efficiency, activity and chemoselectivity in synthesizing a, a’-bis-substituted alkanones. In terms of studies of mechanism, the high efficiency is related to the weak Ti-Cl bond. The oxo-bridged dimeric motif of Ti2 should be responsible for the high chemoselectivity.In Chapter 3, five titanium alkoxides are applied to the Claisen-Schmidt condensation reaction, resulting in good efficiency. The relationship of structural factors and Lewis acid activity is studied via kinetics analysis and the condensation degree (y) of POTs is important to the Lewis acid activity.