Development of Synthetic Reactions Using New Types of Lewix Acid Catalysts

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1.Catalytic Friedel-Crafts acylation of benzene and unactivated benzenes such as chlorobenzene and fluorobenzene has been successfully carried out using hafnium (IV) inflate and trifluoromethanesulfonic acid as catalysts. Both aromatic and aliphatic carboxylic acid chlorides reacted smoothly under the conditions to afford the corresponding aromatic ketones in good yields.2. Metal chlorides and some perchlorates and trifluoromethanesulfonates (triflates) of group 1-15 elements were screened in the Mukaiyama aldol reaction (an aldol reaction of an aldehyde with a silyl enol ether) for the purpose of finding Lewis acid catalysts stable in water. It was shown that metal compounds based on Fe(II), Cu(II), Zn(II), Cd(II), Pb(II) as well as the rare earths (Sc(III), Y(III), Ln(III)) were stable and active in water. Correlation between catalytic activity of these elements (cations) in water and hydration constants and exchange rate constants for substitution of inner-sphere water ligands (wate … More r exchange rate constant (WERC)) were found, and without exception metal compounds, which have both pKh values from 4.3 to 10.08 and WERC greater than 3.2x10^6 M^<-1> sec^<-1>, gave satisfactory yields in the aldol reaction.3. Development of polymer-supported catalysts is one of the most important tasks in organic synthesis. especially in the move towards clean and environmentally friendly chemical processes. We have developed an unprecedented polymer-supported Lewis acid, a microencapsulated scandium trifluoromethanesulfonate (scandium inflate) (MC Sc(OTf)_3). This new method for immobilizing a catalyst onto a polymer is based both on physical envelopment by the polymer and on electronic interaction between pi electrons of benzene rings of the polymer and a vacant orbital of the Lewis acid.A scanning electron microscopy (SEM) micrograph revealed that small capsules of MC Sc(OTf)_3 adhered to each other, and it was also shown by scandium energy dispersive X-ray (EDX) mapping that Sc(OTf)_3 was located all over the polymer surface. One of the most remarkable points is that the activating ability of MC Sc(OTf)_3 was shown to be superior to monomeric Sc(OTf)_3 by preliminary kinetic studies. The catalyst was readily prepared and maintained high activity. Moreover, it was recoverable and reusable, and was successfully applied to many useful carbon-carbon bond-forming reactions. Less