Efficient Synthesis of 3,3'-(Phenylmethylene)Bis-(2-phenyl-1H-Indoles) by Salicylic Acid as a Catalyst

It is very important today to conduct chemical reactions using the concept of green chemistry [1]. The paper develops an efficient and environmentally safe method for the synthesis of 3,3 '- (phenylmethylene)bis(2-phenyl-1H-indole) based on the condensation of 2-phenylenindole and benzaldehyde. In order to optimize the reaction conditions, the synthesis is carried out under different conditions. In particular, the reaction was carried out without solvent, in a water area, in a mixture of ethyl alcohol and water with different volume ratios, using a catalyst. It was found that in almost all cases the reaction went with high yield (> 85%). The duration of the reaction is remarkable. The best result was achieved, when we used water as a solvent: a mixture of ethanol in a ratio of 1: 1, and as a catalyst - salicylic acid (optimal amount of catalyst 15 mol%).