Carbonyl-Olefin/Alkyne Metathesis Reactions Catalyzed by Bifunctional H-USY Zeolites

Metal-, organo-, and proton-catalyzed carbonyl-olefin/alkyne metathesis reactions have gained relevance in organic synthesis during the past decade, but their potential implementation in high-volume processes (i.e., in flow) is severely hampered by the lack of a general, robust, easily separable, and nontoxic solid catalyst. Both Brønsted and Lewis acid sites inside molecular-sized soluble cages seem to be involved during the catalytic process in solution; thus, a similar bifunctional acid solid catalyst, in a confined space, could play the desired catalytic role. We show here that commercially available, ultrastabilized aluminosilicate acid faujasites (H-USY zeolites), containing Brønsted and Lewis acid sites in microporous channels and cavities, catalyze a variety of intra- and intermolecular metathesis reactions between aldehydes/ketones and alkenes/alkynes, with diverse structural patterns, in reasonable yields and under mild reaction conditions. The zeolite can be easily recovered after the reaction in batch and reused or implemented in in-flow processes for continuous synthesis of the metathesis products. These results open the way to designing carbonyl-olefin/alkyne metathesis reactions with simple solid catalysts.