Development of catalytic organic reactions in aqueous media

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Recently, use of water as a reaction solvent has received considerable attention in synthetic organic chemistry for several reasons. First, water is a cheap, safe, and environmentally benign solvent when compared with organic solvents, which are normally used for organic reactions. Use of water will reduce the use of harmful organic solvents and is regarded as an important research topic in green chemistry. Second, in aqueous reactions, it is unnecessary to dry solvents, substrates, and reagents before use. Thus, consumption of drying agents, energy, and time can be reduced. Third, water has unique physical and chemical properties, and by utilizing these it would be possible to realize reactivity or selectivity that cannot be attained in organic solvents.Although various efficient catalytic systems in water have been developed so far, there are still many types of reactions which are difficult to carry out in water. The aim of this research is to develop efficient catalytic organic reactions in aqueous media.The following are the main results obtained during the research period.(1) Highly hydrophobic polymer-supported acid catalysts that can be used for various reactions in water were developed.(2) Palladium-catalyzed allylic substitution reactions of allyl alcohols in water were developed.(3) It was found that Fe(III) ion was effective for diastereoselective Mukaiyama aldol reactions in aqueous media.(4) Catalytic asymmetric hydroxymethylation of silyl enol ethers in aqueous media was developed.(5) Catalytic asymmetric Mannich-type reactions of hydrazones in water were developed.(6) Two-step repetitive synthesis of functionalized oligoarenes was achieved. The efficient methods for the synthesis using a water-THF mixed solvent system were developed.