Studies On The Synthesis And Applications Of α-oxo Ketene-(S,S)-Acetals

Environmental issues have attracted considerable attention of the world. Traditional organic reaction is facing the challenge for the limitation of the use of organic solvent. It is challenging research topic to avoid or reduce the waste for organic synthesis. Reacently, it was widely reported that water was used as organic reaction medium. Bing an easily available, cheap, safe and benign solvent, water avoid the disadvantages of most organic solvent, such as flamable, explosive, volatile and pollution.Organic synthesis in aqueous media has become active area of organic chemistry. Today, water as solvent has been applied to many organlic reactions such as oxidation, reduction, condensation, cycloaddition, coupling, Wittig, organic photochemistry, radical reactions.α-Oxo ketene-(S,S)-acetals are a kind of versatile intermediates used in organic synthesis. Base on its structure, it is widely used in organic synthesis. In the past decade, we have been devoting our efforts towards the synthesis and applications onα-oxo ketene-(S,S)-acetals and achieved interesting results. In particular, we successfully appliedα-oxo ketene-(S,S)-acetals as thiols equivalents in thioacetalization and Michael addition reactions in aqueous or solvent-free conditions, sorting out the environment and safety problems of thiols with low molecular weight used in organic reactions. To avoid the use of organic solvent, we has been investigating the novel organic reaction in water.In the present thesis, we devort our effort to develop novel organic reaction withα-oxo ketene-(S,S)-acetals in water. Aming to develop new basic reactions and new synthetic methods we developed a new [4 + 2] synthetic strategy from ?-oxo ketene-(S,S)-acetal chemistry based on synthetic design, providing a general and simple route to polysubstituted pyranons. Mono- and double condensed ?-alkenoyl ketene-(S,S)-acetals aere synthesized through aldol condensation reactions of ?,?-diacetyl ketene-(S,S)-acetals. An efficient synthesis of thieno[2,3-b]quinolines is developed from 2-aminothiophens. The thesis mainly include three aspects:1. The synthesis of mono-condensed and double condensed???-alkenoyl ketene-(S,S)-acetals has been developed via the aldol condensation of ?,?-diacetyl ketene-(S,S)-acetals with aromatic aldehydes in the presence of NaOH in water. The simple procedure, mild conditions, easy separation, high yields, high chemoselectivity, and especially that in relation to the current environmental concerns, make this protocol most attractive for academic research and practical applications.2. [4 + 2] Annulation strategy is developed. Dihydropyranones were synthesized via the formal [4+2] annulation of readily available ?-acetyl ketene-S,S-acetals with various aldehydes, involving tandem aldol reaction and conjugate addition-elimination reaction, in the presence of NaOH in water.3. A series of 2-aminothiophens were designed and synthesied, which were converted into substituted thieno[2,3-b]quinolines catlyzed BF3·Et2O. The thieno[2,3-b]quinoline synthesis is associated with advantages such as simple procedure, mild condition and high yields.