Silica-supported boric acid catalyzed synthesis of dihydropyrimidin-2-ones, bis(indolyl)methanes, esters and amides †

Silica-supported boric acid (H3BO3-SiO2) has been established as a green, efficient and recyclable catalyst for the synthesis of dihydropyrimidin-2-ones, bis(indolyl)methanes, and acetylation of alcohols, phenols, amines and thiols under solvent free conditions. The main features of the present method include clean reaction, mild conditions, low loading of environment friendly catalyst and easy workup procedure. The catalyst can be recycled at least five times without any significant loss in activity.