Study On Cyanation Of Aromatic Compounds And Its Application

Nitriles are useful intermediates in organic synthesis and play a crucial role in many fields as they can be easily converted into a variety of functional groups such as acids and amines. They also have a widespread application in the fields of pesticide, dyes and Pharmaceuticals. So the study of cyanation is of great value not only in basic theory study but also in its wide application in various fieldes. Various methods for the synthesis of nitriles have been reported. In general, nitriles are synthesized from halides and stoichiometric amounts of copper(I) cyanide, from aniline by diazotization and subsequent Sandmeyer reaction, or by ammoxidation. Nevertheless, the most convenient method for the synthesis of aryl nitriles is based on the transitionmetal-mediated displacement of aromatic halides and triflates by the cyanide ion.Firstly, a cyanation process of aryl halides with K4[Fe(CN)₆]-3H₂O as the cyanating reagent was studied. Compared with the traditional cyanating agent, potassium hexacyanoferrate(II) is non-toxic, environment-friendly and readily available without the need of complicated pre-processing. Then, cyanation of aryl halides using homogeneous catalyst (Pd(OAc)2) was investigated. Factors affecting the reaction such as the ratio of reactants, time, temperature, amount of catalyst on the cyanation were investigated. Optimal reaction conditions were determined. Also, aryl nitriles have been prepared from the corresponding aryl halides with potassium hexacyanoferrate(II) using Pd/C as a catalyst without phosphine ligand. Furthermore, the catalyst could be recycled by simple operations. Besides, cyanation of aryl halides using copper catalyst was investigated and good yields could be obtained using CuI/1,10-phenanthroline as the catalyst system.Aryl perfluoroalkanesulfonates are well-known aryl halide equivalents for transitionmetal-catalyzed coupling reactions owing to the diversity of available phenols. Subsequently, cyanation of aryl triflates, aryl nonaflates and aryl perfluorooctylsulfonates has been studied respectively. It was shown that the presence of ligand was the key factor in obtaining the corresponding aryl nitriles and the addition of CuI could not only reduce the amount of catalyst but also shorten the reaction time.Moreover, other kind of cyanation was explored. Nitriles were obtained from aldehydes through oxidation of in situ formed the corresponding aldimines using tetrabutylammonium tribromide (TBATB). On the basis of the studies above, a procedure for the synthesis of 5-substituted 1H-tetrazoles through the three-component reaction between aryl bromides, K₄[Fe(CN)6] and NaN3 catalyzed by Pd(OAc)2 and ZnBr2 has been developed.