Application of solid base catalysts in the preparation of prepolymers by condensation of ketones and malononitrile

Solid base catalysts such as zeolites, sepiolites and hydrotalcites have been used to prepare prepolymers of malononitrile with cyclohexanone, benzophenone, andp-amino acetophenone which are of interest for preparing living polymers. The reactivity depends on both the catalyst and the nature of the ketone. Among the catalysts studied, hydrotalcites are the most active, followed by cesium-exchanged sepiolites. High selectivities and good yields have been obtained with these two solid base catalysts. It is proposed that the controlling step for these condensation reactions is not the formation of the carbanion, but the addition of the carbanion to the carbonyl group.