New conditions for the synthesis of thiophenes via the Knoevenagel/Gewald reaction sequence. Application to the synthesis of a multitargeted kinase inhibitor

Novel conditions have been developed for the preparation of substituted 2-aminothiophenes employing the Knoevenagel condensation followed by the Gewald reaction. The benefits of these conditions are their mildness, and the ease of product isolation. Thus, the Knoevenagel condensation is run in the presence of hexamethyldisilazane and acetic acid, which combine to perform the roles of desiccant, and catalyst. The Gewald reaction is performed with inorganic base in THF/water, which suppresses byproduct formation. This process has been employed in the total synthesis of a multitargeted kinase inhibitor.