ISSN 1070-3632, Russian Journal of General Chemistry, 2008, Vol. 78, No. 5, pp. 1009–1010. © Pleiades Publishing, Ltd., 2008.
Original Russian Text © Yu.A. Lisitsin, L.V. Grigor’eva, 2008, published in Zhurnal Obshchei Khimii, 2008, Vol. 78, No. 5, pp. 866–867.
LETTERS
TO THE EDITOR
Electrochemical Amination of Anisole to Anisidines
in a Mixture Aqueous Sulfuric Acid and Acetonitrile
Yu. A. Lisitsin and L. V. Grigor’eva
Kazan State University, Butlerov Chemical Institute,
ul. Kremlevskaya 18, Kazan, Tatarstan, 420008 Russia
e-mail: Yuri.Lisitsyn@ksu.ru
Received December 24, 2007
DOI: 10.1134/S1070363208050307
Electrochemical amination of aromatic substrates
by hydroxylamine with Ti(IV)/Ti(III)system as me-
diator provides a fundamental possibility of one-stage
synthesis of mono- and diaminocompounds [1, 2]. In
the aqueous sulfuric acid up to 7 M concentration the
only substitution products are monoamines. But when
the substrates insoluble or poorly soluble in catholyte
are exposed to amination even under the most
favorable conditions (1–3 M H2SO4 solutions) the
current yields of monoaminocompounds do not exceed
11% [3, 4], the main part of the aminyl radicals is
reduced with Ti(III) ions to ammonia.
After the completion of amination the catholyte was
diluted with water to the H2SO4 concentration 1–1.5 M,
cooled and alkalinized to the weak acidic reaction with
NaOH solution and then neutralized with NaHCO3.
The products of amination of anisole were extracted
with chloroform and analyzed on
a Chrom-4
chromatograph. For more exact analysis of the nature
of products the flame ionization detector, the
katharometer, and the XE-60, the SE-30, and the OV-
17 phases were used. The quantitative analysis of
anisidines was carried out on a 2500 × 3 mm steel
column filled with 5% of XE-60 on Chromaton N-AW
(0.169–0.200 mm) at 150°C using the flame-ionization
detector.
In this study we showed by an example of anisole
functionalization that using in the process of amination
of aromatic compounds acetonitrile, the organic
solvent more inert to the aminoradical intermediates
[5], permits to increase significantly the efficiency of
substitution and to prepare monoamines in the
sufficiently high yields with respect to the
aminoradical source.
The electrolyses carried out in 1.5 M H2SO4
showed that the dependence of the current yield on the
acetonitrile concentration passes through the minimum
point in 11 M solution, but at high concentrations of
organic solvent the efficiency of the target
electrochemical process does not significantly exceed
11%. Therefore considering the effect of H2O/H2SO4
ratio on the results of substitution [4] we have carried
out the amination of anisole in the electrolytes
containing 2–7 M of H2SO4 and the concentrations of
acetonitrile close to the maximum possible.
The amination of anisole was carried out in the
glass electrochemical cell with the cathode and the
anode spaces separated with a ceramic diaphragm. The
catholyte, 25 ml of water solution, contained 0.2 M of
NH2OH, 0.1 M of Ti(IV), and also the required
concentrations of sulfuric acid and acetonitrile.
Electrolysis of the highly dispersed emulsion of 5 ml
of anisole in the catholyte deaerated with argon was
carried out at 40°C and the current density on the
mercury anode 2 mA cm–2. For the sake of comparison
of the results of investigation with the data of [4] the
amount of electricity passed through the emulsion in
the course of electrolysis as a rule was 250 Coulombs.
In the media with high content of solvent the
products of amination of anisole are ortho- and para-
anisidines. The highest yield of aminocompounds was
obtained in the catholyte containing 6 M of H2SO4 and
11.6 M of CH3CN. Due to the chain mechanism of the
electrochemical process the current yield of anisidines
(para/ortho ratio ~1.8) under these conditions
exceeded 100% and reached 147%. When the elec-
1009
Lisitsin
