10-Methyl-9-phenylacridinium iodide and 2,4,6-triphenylpyrylium perchlorate as catalysts for reduction of aromatic ketones

Full text of DOI:10.1134/S107042801503029X

ISSN 1070-4280, Russian Journal of Organic Chemistry, 2015, Vol. 51, No. 3, pp. 445–446. © Pleiades Publishing, Ltd., 2015.
Original Russian Text © B.S. Tanaseichuk, A.I. Azrapkina, M.K. Pryanichnikova, A.V. Dolganov, 2015, published in Zhurnal Organicheskoi Khimii, 2015,
Vol. 51, No. 3, pp. 458–459.
SHORT
COMMUNICATIONS
10-Methyl-9-phenylacridinium Iodide
and 2,4,6-Triphenylpyrylium Perchlorate as Catalysts
for Reduction of Aromatic Ketones
B. S. Tanaseichuka, A. I. Azrapkinaa, M. K. Pryanichnikovaa, and A. V. Dolganovb
a Ogarev Mordovian State University, ul. Bol’shevistskaya 68, Saransk, 430000 Russia
e-mail: orgchem@mrsu.ru
b Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences,
ul. Vavilova 28, Moscow, 119991 Russia
Received October 12, 2013
DOI: 10.1134/S107042801503029X
Methyl viologen and its analogs are capable of un-
dergoing multiple redox transformations dication
radical cation [1]. The resulting radical cation may be
regarded as an electron-rich radical [2] which tends to
donate electron to an appropriate acceptor and return to
the initial aromatic cation. This property was widely
utilized in various electrochemical, photochemical, and
other processes [3, 4], including reduction [5–7]. It
may be presumed that other heterocyclic cation which
can undergo reversible reduction to the radical, e.g.,
triphenylpyrylium (1) [8] or 10-methyl-9-phenylacridi-
nium (2) [9], can also act as electron carrier.
seen that benzil was reduced most readily; next
followed benzophenone, while acetophenone failed to
react. The different results of the reduction of aryl
ketones are determined by the substituent on the
carbonyl group: the stronger the electron-withdrawing
power of the substituent, the more facile is the reduc-
tion. On the other hand, the yield of the reduction prod-
uct also depends on the redox potential of the initial
ketone. Comparison of the data for benzil and benzo-
phenone shows that the yield increases in parallel with
the redox potential of the corresponding cation.
Thus, the ability to act as electron carrier in reduc-
tion processes is a characteristic feature of heterocyclic
cations. A probable mechanism of this reaction is
shown below.
We made an attempt to use cations 1 and 2 (as
perchlorate and iodide, respectively) in the reduction
of aromatic ketones with zinc. As model substrates we
selected benzil, benzophenone, and acetophenone.
All reactions were carried out in aqueous acetonitrile
under argon at the same reactant ratio.
The catalytic activity of cations 1 and 2 (as
perchlorate and iodide, respectively) was studied under
standard conditions: a mixture of 1.5 mmol of zinc,
1.0 mmol of aryl ketone, 0.05 mmol of the catalyst,
and 20 mL of 98% acetonitrile was stirred for 24 h at
20°C under argon.
Our results, as well as published data on the reduc-
tion of aromatic ketones in the presence of propyl
viologen (3) as catalyst [5], are given in table. It is
Yields of the reduction products (%) of aryl ketones with zinc in the presence of heterocyclic cations 1–3
1
2
3
Substrate
E1/2,a V [10]
Product
E1/2b = –0.35 V
E1/2b = –0.5 V E1/2 = –0.43 V [1]
PhCOCOPh
PhCOPh
–0.54
–1.25
–1.54
PhCH(OH)COPh
Ph2C(OH)C(OH)Ph2
–
50
00
00
99
62
00
92
13
00
PhCOMe
a
Ionization potential of ketone.
Reduction potential of the cation (data of this work).
b
445

TANASEICHUK et al.
This study was performed under financial support
446
Zn
R+
·
R
by the Council for Grants at the President of the
Russian Federation (project no. SP-1292.2013.1).
Ph
EWG
Ph
EWG
·
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O
O
H2O
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