| Abstract: | Electrochemistry behaviors including linear sweep voltammetry and cyclic voltammetry of tertiary cyclic amines with different substituted group were studied. The effect of different substituted group of the nitrogen on the oxidation potential was analyzed. The most suited potential used in αα-aminonitrile synthesis through potentiostatic anodic cyanation of cyclic teritary amines was found. The anodic cyanation of N-alkyl-substituted cyclic six-membered amines including N-benzylpiperidine and N-ethylpiperidine has been investigated. The reaction gives the corresponding á-aminonitrile and carried out at a platinum anode in methanolic solution of the amine, containing 2.5 equivalents of sodium cyanide per mol of substrate. In all the selected amines the introduction of the cyanide group occurs in the position α to the nitrogen atom. We obtained two α-aminonitrile isomers. One is cyanated in the ring, the other is cyanated in the side chain. 1 The reaction mechanism is analyzedt brough analyzing the product of the constant current electrolysis and potentiostatic electrolysis and explained why the difference in the relative amount of isomers of tertiary cyclic amines and in the reactivities of the alkyl group between the ring and the side chain.The amount of isomers could not affect by the anode potential, and decided by the adsorption status at the anode surface and stability of the intermediate.The intermediate formed in anodic cyanation of N-benzylpiperidine is a parallel reaction, so the yield of α-aminonitrile can be increased but the selectivity of the two isomers cannot be increased in the potentiostatic electrolysis.The mechanism of the anode cyanation of N-benzylpiperidine was studied In methanol-water solution, anode cyanation of N-benzylpiperidine gives not only monocyanation product α-cyanoamine but also dicyanation product α, α-dicyanoamine and other byproduct because of overoxidation of N-benzylpiperidine caused by polarization of the anode under the constant current electrolysis. Under potentiostatic electrolysis, the reaction can be controlled that only monocyanation product α-cyanoamine formed. The selectivity of the reaction can be enhanced through the potentiostatic electrolysis because of overoxidation can be avoided.Six-membered cyclic α-aminonitriles have been prepared from anodic cyanation of N-benzylpiperidine. The results of these investigaiton at different electrode material, solvent,surfactant and current under constant current electrolysis were studied. Low current, CH3OH/H2O and CH3CN/H2O used as solvent, tetraammonia salt such as Et4NOTs and Et4NBr used as surfactant are all propitious to the reaction. Graphite can be used as anode substitute for platinum. Controlled potential electrolysis under different potential, temperature, substrate concentration and the mechanism of the reaction were also studied. Good yield of α-aminonitriles can be obtained under the 0.9-1.4V (vs. SCE), low temperature and low substrate concentration. It is also explained that the amount of isomers is decided by the adsorption status at the anode surface and stability of intermediate. The studied methods and conclusions obtained from this paper can be used in organic electrochemistry industry. |
