Solid base catalysts: generation of basic sites and application to organic synthesis

Abstract

Studies of solid base catalysts on generation of basic sites and their catalytic behaviors in organic reactions performed in our group are summarized. For most of the materials called solid base, the catalytic activities appear on removal of water and carbon dioxide from the surfaces. The nature of the surface basic sites varies with severity of pre-treatment conditions. Besides removal of water and carbon dioxide, rearrangement of surface and bulk atoms occurs during pre-treatment, which changes the number and nature of the basic sites with increasing the pre-treatment temperature. Therefore, the optimum pre-treatment temperature varies with the type of reaction. Applications of solid base catalysts to the following reactions are described; (1) double bond isomerization, (2) hydrogenation, (3) amination, (4) dehydrocyclodimerization, (5) aldol addition, (6) nitroaldol reaction, (7) Michael addition, (8) conjugate addition of alcohol, (9) cyanoethylation, and (10) Tishchenko reaction. Characteristic features of the solid base catalysts toward these reactions are briefly explained. Finally, selected base-catalyzed reactions which have been industrialized by use of solid base catalyst are exemplified, and short comments on the catalysts used in these processes are made.