Zeolites as Base Catalysts. Preparation of Calcium Antagonists Intermediates by Condensation of Benzaldehyde with Ethyl Acetoacetate.

The condensation of benzaldehyde with ethyl cyanoacetate, ethyl malonate and ethyl acetoacetate were carried out with high rates and selectivity promoted by lithium-, sodium, potassium-, and caesium-exchanged X and Y zeolites and on sodium-Germanium substituted faujasite. The 2-nitrobenzaldehyde, 3-nitrobenzaldehyde, 2-trifluoromethylbenzaldehyde and 2,4-dichlorobenzaldehyde were condensed with ethyl acetoacetate to obtain precursors in the production of dihydropyridine derivatives in the presence of these base catalysts operating in a batch reactor at moderate temperatures. The most active zeolites are more active than pyridine, and less active than piperidine, showing basic sites with pKb < 13.3. The selectivity to the desired condensation product when using zeolites is, at least, as high as in the case of the homogeneous catalyst.