Boron trifluoride supported on nano-SiO2: an efficient and reusable heterogeneous catalyst for the synthesis of bis(indolyl)methanes and oxindole derivatives

Boron trifluoride supported on nano-SiO2 was used as an efficient and heterogeneous catalyst for the electrophilic substitution reaction of indole with various aromatic aldehydes and isatins in methanol to afford the corresponding bis(indolyl)methanes and oxindole derivatives in high yields at room temperature and under reflux conditions, respectively. The catalyst can be reused several times without loss of its catalytic activity.