A preparative method of synthesis of the new methyl 3-iodo-1-benzothiophene-2-carboxylate was elaborated. Electrochemical behavior of methyl 3-chloro-, bromo- and iodo-1-benzothiophene-2-carboxylates 1-3, and of their reduction and dimer products 4, 5 in anhydrous dimethylformamide has been investigated at mercury and platinum electrodes using polarography, cyclic voltammetry and voltammetry on a rotating platinum disk electrode. The reduction in divided cells follows the ECE mechanism (electron - chemical step - electron), where the primary radical anion is split into a halide anion and neutral heterocyclic radical, which is immediately reduced by the second electron and protonated. The only reduction product is the methyl 1-benzothiophene-2-carboxylate (5); whereas the EDim mechanism (electron - dimer formation) leading to the dimeric species 4 was not observed under the above conditions. Reduction of 1-3 on platinum causes formation of a blocking film on the electrode. Sonication during electrolysis successfully reactivates the electrode.
制备了新的甲基3-碘-1-苯并噻吩-2-羧酸甲酯的合成方法。在无水二甲基甲酰胺中,使用极谱法、循环伏安法和旋转铂盘电极伏安法研究了甲基3-氯、溴和碘-1-苯并噻吩-2-羧酸甲酯1-3及其还原和二聚产物4、5的电化学行为。在分裂电池中,还原遵循ECE机制(电子-化学步骤-电子),其中初级自由基阴离子分裂成卤离子和中性杂环自由基,后者立即被第二个电子还原并质子化。唯一的还原产物是甲基1-苯并噻吩-2-羧酸甲酯(5);而在上述条件下没有观察到导致二聚物4的EDim机制(电子-二聚物形成)的发生。在铂上还原1-3会导致电极上形成阻塞膜。在电解过程中超声波处理可以成功地使电极重新活化。