The Synthesis of Formylated-Triarylmethanes and Their Use in the Preparation of Hydrazone and Azine Derivatives

Hydrazones and azines have attracted great interests in organic synthesis due to their versatile applications as synthons in the preparation of heterocyclic compounds as well as medical agents [1], [2]. Several methods are available for the synthesis of triarylmethanes (TRAMs), however their synthetic applications has gained less attention until now. In continuation of our work on TRAMs, herein we report controlled catalytic procedures for the synthesis of azine and hydrazine derivatives bearing triarylmethane unit(s) [3]. First, formylated-triarylmethanes were synthesized via the Friedel-Crafts reaction of arenes with dialdehydes catalyzed by silicasulfuric acid (SSA) under solvent-free conditions. Then, the aldehydes were reacted with hydrazine hydrate (1:2 molar ratio) in the presence of L-proline, as an organocatalyst, and under N2 atmosphere toafford the corresponding hydrazones, quantitatively (Figure 1). It was perceived that this reaction can be also used for the synthesis of azine products by changing the molar ratios of substrates and choosing an appropriate catalyst. Accordingly, the reaction of formylated-triarylmethanes with hydrazine hydrate in 2:1 molar ratio, catalyzed by either AcOH or SSA, gave the corresponding azines. The structures of the synthesized compounds were characterized by elemental analyses, and FT-IR, 1H-NMR, and 13C-NMR spectral data.