SHAPE SELECTIVITY IN ORGANIC-SYNTHESIS

Heterogeneous catalysis is the most convenient method for many organic syntheses due mainly to the ease of experimental handling and the sav ings in costs, since finely divided catalysts suspended in the reactio n medium (liquid in a high percentage of cases, due to the need for wo rking at low temperatures to avoid undesired side reactions) can be ea sily recovered at the end of the reaction. Zeotypes are amongst the mo st important solid catalysts to be used in organic synthesis (1-5), du e to their porous nature with controlable properties such as acidity, and molecular Sized cavities where reactions take place in quasi-enzym atic conditions, since molecules of greater size than the pore opening s are not able to enter and react. This steric hindrance gives rise to the property defined as shape selectivity (2). Between the 1960's and 1980's catalysis with zeotypes was dedicated to petrochemical process es (refining and hydrotreating), due to the petroleum crises during th at period. More recently their uses have been broadened to incorporate all types of organic syntheses, with appreciable advantages over more conventional catalysts in a number of processes.