One-Pot Suzuki/Heck Sequence for the Synthesis of (E)-Stilbenes Featuring a Recyclable Silica-Supported Palladium Catalyst via a Multi-Component Reaction in 1,3-Propanediol
Résumé
The synthesis of (E)-stilbenes was performed following a one-pot Suzuki/Heck sequence through the use of potassium vinyltrifluoroborate. The combination of heterogeneous palladium/silica (Pd/SiO2) catalyst with potassium phosphate monohydrate (K3PO4H2O) as base resulted in useful to good isolated yields regardless of the ortho-, meta- or para-substitution of the aryl halides employed. In a sustainable approach. we found that bio-sourced 1,3-propanediol could advantageously replace N-methyl-pyrrolidone (NMP) as similar yields were obtained Moreover, the reactivity gap between aryl iodides and bromides resulting from the use of 1,3-propanediol allowed an efficient multi-component approach toward the synthesis of (E)-stilbenes. Furthermore. this heterogeneous catalyst was found to he extremely robust despite the use of aerobic conditions and was successfully re-used over several cycles.