Quantum Chemical Studies of Lewis-Acid Catalyzed Organic Chemical Reactions

Lewis-acid catalyst is one of the most fundamental catalysts in organic chemical reactions. In this paper, our recent quantum chemical studies on Lewis-acid catalyzed organic chemical reactions have been presented. First, we focused on the mechanism of Lewis-acid activated Lewis acid catalysts. Then, the normal-electron-demand Diels-Alder reaction between cyclopentadiene and maleic anhydride was discussed in order to clarify the origin of the stereoselectivity. The endo selectivity is attained when dienophile carries a group (or groups) involving highly polarized bonds. We show that the well-known donor-acceptor relationship in the normal-electron-demand Diels-Alder reaction is linked to the endo selectivity. On the basis of the results, the Diels-Alder reaction of cyclopentadiene with methyl acrylate catalyzed by a simple Lewis acid, AlCl3, has been investigated. The Lewis-acid catalyst facilitates the cycloaddition and brings a higher endo selectivity in the highly asynchronous process. Finally, we discussed two reactions catalyzed by tris(pentafluorophenyl) borane, B (C6F5)(3).