Aldol Reaction ‐ Heterogeneous

Abstract This article deals with the heterogeneously catalyzed aldol condensation reactions. The convenience of heterogeneous operation compared to the traditional homogeneous processes is first discussed from the environmental point of view. The effect of the operating conditions such as liquid‐ or gas‐phase reactions, use of metallic, acidic, or basic catalysts, and high or low temperature on the reaction selectivity is also presented. The base‐catalyzed aldol condensation mechanism is thoroughly discussed. Several examples of carbonyl and carbonyl–derived compounds synthesized by aldol‐like reactions such as Knoevenagel, Claisen–Schmidt, and Michael condensations on basic catalysts are presented as well as the catalytic systems useful in the synthesis of solvents, pharmaceuticals, and other fine chemicals. Finally, the less known acid‐catalyzed pathway is presented, and examples of acidic catalysts are reported.