o-phenylenediamine and carbonyl compounds by Brønstedacid/base assisted titanocene dichloride. Mechanism research including NMR and ESI-MS analyses and control experiments elucidated the new catalytic species formed by Cp2TiCl2 and the combination of titanocene Lewis acid with Brønstedacid/base was responsible for selective transformations of aldehyde and ketone with o-phenylenediamine into benzimidazole