Electrosynthesis of N-tert-Butyl-2-benzothiazolesulfenamide

Conditions for the production of N-tert-butyl-2-benzothiazolesulfenamide (TBBS) in an oxidative condensation of 2-mercaptobenzothiazole and tert-butylamine are determined. The electrosynthesis occurs during electrolysis of a 4.5–5.0 M NaCl solution containing a water-immiscible organic solvent extracting TBBS. The process efficiency is the highest at the following conditions: a 1 : 8 ratio between 2-mercaptobenzothiazole and tert-butylamine, a DSA, a stainless-steel cathode, a current density of 300 A m^–2, and a continuous extraction of TBBS into a 3 : 1 mixture of carbon tetrachloride and acetonitrile. Under these conditions, the TBBS yield is 98–100%, the current efficiency is 74%, the process productivity is 0.9 kg m^–2 h^–1, and the electricity consumption is 1.9 kW h kg^–1. Repeated use of the aqueous phase corrected for the source products jeopardizes neither the process characteristics nor the product quality.     

Electroreduction of a Sodium Salt of 4-Nitrosodiphenylamine: Effect of the Technological Solution Components

Two methods of preparation of 4-aminodiphenylamine (I) are compared: by electrochemical reduction of an alkaline solution of 4-nitrosodiphenylamine (II), extracted from a technological solution, and by electrolysis of the solution itself, which contains, apart from the nitroso compound, methanol and NaCl. By voltammetry and preparative electrosynthesis it is shown that the lower reduction rate of the technological solution of the Na salt of II is due to inhibiting effects of methanol and NaCl. Tetraalkylammonium cations, decreasing the limiting reduction current of II, do not affect the electrosynthesis rate when the generated I is continuously extracted into a water-immiscible solvent.     

Electrochemical synthesis of 2,2,6,6-tetramethylpiperidine

A preparative method for the production of 2,2,6,6-tetramethylpiperidine based on the electrochemical reduction of 4-oxo-2,2,6,6-tetramethylpiperidine in 30% sulfuric acid on cadmium or lead electrodes was developed.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 358–359, March, 1984.     

Utilization of solutions after the electroreduction of a sodium salt of 4-nitrosodiphenylamine

An approximately 20-% alkali solution remains after the electroreduction of an alkali solution of a sodium salt of 4-nitrosodiphenylamine (II), in the course of which the formed 4-aminodiphenylamine (I) is continuously extracted into a water-immiscible solvent. The remaining solution, which contains about 10 mM I and up to 1 mM II, may be used for preparing the catholyte for another experiment. To this end, the solution must be anodically treated using a stainless-steel electrode, and the charge spent in the treatment must equal that spent during the electroreduction. After the treatment, the solution settles; the content of II remains virtually unchanged, that of I drops about tenfold, and that of alkali is 50% of the calculated (1 F per mole of alkali). A multiple use of the same alkali solution makes no impact on the yields of I.     

Synthesis of 4-aminodiphenylamine by electroreducing alkaline solutions of a sodium salt of 4-nitrosodiphenylamine

Conditions for the synthesis of 4-aminodiphenylamine (I) by electroreducing a 1 M solution of a sodium salt of 4-nitrosodiphenylamine (II) in a 5-% alkali solution are found. The electroreduction is carried out on the copper and stainless-steel cathodes with a continuous extraction of the product into a water-immiscible solvent. Variations in the alkali concentration, current density, and temperature have no effect on the yield of I, which is almost quantitative. The current efficiency increases with the temperature and approaches 60% at 60–70°C on a copper cathode. Copper and stainless-steel cathodes and stainless-steel anodes are sufficiently stable in the 4-aminodiphenylamine electrosynthesis.     

Utilization of Solutions after the Electrosynthesis of 4-Aminodiphenylamine

The electroreduction of technological solutions of a sodium salt of 4-nitrosodiphenylamine with a continuous extraction of formed 4-aminodiphenylamine into a water-immiscible solvent and a separation of the latter, leaves a solution containing alkali, sodium chloride, methanol, and admixtures of the initial and target compounds. Freed from the methanol, the solution may serve as anolyte in the salt electroreduction, instead of an alkali solution used for the purpose. The most suitable anode material is titanium covered with platinum or iridium. Anodically treated solutions are colorless and contain no initial and target substances but include oxygen compounds of chlorine. The formation of the compounds may be avoided by introducing 10^–4 M Co²⁺ into solution. The ions may be used repeatedly.