A mild and convenient procedure for the oxidation of aromatic aldehydes to carboxylic acids using urea-hydrogen peroxide in formic acid

Article abstract of DOI:10.1081/SCC-100104472

Mild and safe oxidation of aromatic and heteroaromatic aldehydes to the corresponding acids was achieved by using UHP in formic acid.

Full text of DOI:10.1081/SCC-100104472

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A MILD AND CONVENIENT PROCEDURE FOR THE
OXIDATION OF AROMATIC ALDEHYDES TO CARBOXYLIC
ACIDS USING UREA-HYDROGEN PEROXIDE IN FORMIC
ACID
a
Roman Balicki
a
Pharmaceutical Research Institute, Rydygiera 8, Warszawa, 01-793, Poland
Version of record first published: 09 Nov 2006
To cite this article: Roman Balicki (2001): A MILD AND CONVENIENT PROCEDURE FOR THE OXIDATION OF AROMATIC
ALDEHYDES TO CARBOXYLIC ACIDS USING UREA-HYDROGEN PEROXIDE IN FORMIC ACID, Synthetic Communications: An
International Journal for Rapid Communication of Synthetic Organic Chemistry, 31:14, 2195-2198
To link to this article: http://dx.doi.org/10.1081/SCC-100104472
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SYNTHETIC COMMUNICATIONS, 31(14), 2195–2198 (2001)
A MILD AND CONVENIENT PROCEDURE
FOR THE OXIDATION OF AROMATIC
ALDEHYDES TO CARBOXYLIC ACIDS
USING UREA–HYDROGEN PEROXIDE IN
FORMIC ACID
Roman Balicki
Pharmaceutical Research Institute, Rydygiera 8,
01-793 Warszawa, Poland
ABSTRACT
Mild and safe oxidation of aromatic and heteroaromatic alde-
hydes to the corresponding acids was achieved by using UHP
in formic acid.
A large number methods have been reported for the transformation
1
ofaromatic aldehydes into their corresponding carboxylic acids.
The
conventional methods ofcarrying out this reaction make use ofoxidant
agents, i.e. potassium permanganate, chromium (VI) oxide, pyridinium
dichromate, pyridinium chlorochromate, silver (I) oxide or molecular
2
oxygen. Hydrogen peroxide has been also used for this purpose under
4–7
3
strongly basic conditions itselfor in combination with other reagents.
However, most ofthe existing methods are deficient in some respect such as:
low yields, high cost, severe acidic or basic reaction conditions and forma-
tion ofheterogeneous mixture. On the other hand concentrated H O is very
2
2
dangerous to handle and not readily available. Hence this agent is now
replaced by more stable and safe compounds. Urea–hydrogen peroxide
2
195
Copyright & 2001 by Marcel Dekker, Inc.
www.dekker.com

ORDER
REPRINTS
2
196
BALICKI
8
UHP) is a safe alternative to anhydrous H O , relatively stable, inexpen-
(
sive and commercially available.
2
2
Several systems containing UHP with some carboxylic acid or their
9
–11
anhydrides were used as efficient, oxidizing agents.
Recently we reported
that performic acid obtained by the combination of UHP and formic acid
appeared to be an effective reagent for mild N-oxidation of N-heteroaro-
1
2
13
matics and organic sulfides to sulfones. These results have prompted us
to extend the studies on the oxidizing ability ofthis novel reagent system.
In this paper we wish to report on a safe and efficient oxidation of
aromatic and heteroaromatic aldehydes 1 to the respective carboxylic acid 2
by use ofUHF/HCOOH system. The reaction is very easy and proceeds
within 1.5–3 hours upon addition ofthe substrate 1 to the solution ofUHP
in formic acid at room temperature to afford the corresponding carboxylic
acid 2.
The optimum ratio substrate 1 to UHP was found to be 1:4. Use in the
place of of rmic acid other carboxylic acids alone or in their methanolic
solutions gave less satisfactory results.
Several examples illustrating this novel and efficient procedure for the
oxidation ofaromatic aldehydes 1 to the corresponding carboxylic acids 2
are presented in Table. The reaction proceeds well with aldehydes contain-
ing electron-withdrawing (1h–g) or mildly activating (1h–i) groups. The
presence ofpower uf l electron-donating groups ( 1j–l) gave less satisfactory
results. Oxidation ofpyridine carboxaldehydes ( 1m–p) afforded the corre-
sponding acids in high yield, although the traces ofthe N-oxides were also
formed.
In conclusion, this new method for converting aromatic aldehydes to
the corresponding carboxylic acids offers the following advantages: (a) safe
and cheap oxidizing agent is used, (b) the oxidation is mild and fast giving in
most cases the carboxylic acids in high yields, (c) the method is efficient also
for the oxidation N-heteroaromatic aldehydes (entries 1m–p), (d) the pro-
cedure is facile and isolation of the products is easy. For the above reasons
the procedure described herein may be method ofchoice fo r the conversion
aldehydes into carboxylic acids.
EXPERIMENTAL
Typical Procedure: The corresponding aromatic aldehyde 1 (2 mmol)
was introduced portionwise to the stirred solution ofUHP (8 mmol) in 95%
3
formic acid (15 cm ) at room temperature. The mixture was stirred at this
temperature until tlc analysis indicated completion ofreaction (1. 5–3 hr).
3
The water (20 cm ) was then added to the reaction mixture. The aqueous

ORDER
REPRINTS
OXIDATION OF AROMATIC ALDEHYDES
Table. Oxidation of(Hetero)aromatic Aldehydes to Carboxylic Acids
UHP=HCOOH
2197
Ar—CHO
ꢀ! Ar—COOH
r:t:
1
2
a,b
Yield of 2,
%
Aldehyde 1
Entry
Reaction
time
m.p.
ꢀ
c
Ar
( C)
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
a
b
c
d
e
f
g
h
i
j
k
l
m
n
p
Ph
2-NO
3-NO
2-Cl-Ph
4-Cl-Ph
3-Cl-Ph
4-F-Ph
1.5
2.0
2.0
1.5
2.5
3.0
3.0
2.5
2.0
2.5
96
79
78
78
82
77
75
85
87
51
119–121 (121–123)
145–147 (146–148)
139–140 (140–142)
137–139 (138–140)
240–241 (239–241)
154–157 (155–157)
183–185 (184–187)
180–183 (180–182)
108–111 (108–110)
103–105 (106–108)
2
-Ph
-Ph
2
4-CH -Ph
3
3-CH
3-CH
2-CH O-Ph
3
-Ph
O-Ph
3
d
–
54
3
4-CH
3
O-Ph
3.0
1.5
1.5
2.0
179–181 (182–185)
>308 (310–315)
233–236 (236–239)
277–281 (277–280)
e
4-pyridyl
3-pyridyl
3-quinolyl
91
90
90
e
e
a
1
All products were characterized by their H-NMR and MS spectra.
b
Yields ofisolated crude acids.
Literature m.p’s in parantheses taken from Aldrich Chemical Co., catalogue.
c
d
Intractable complex reaction mixture was obtained.
3
solution was extracted with CHCl (3 Â 10 cm ) and organic layer washed
3
3
3
with water (2 Â 10 cm ), saturated aq. NaHCO solution (2 Â 10 cm ) and
3
3
again with water (2 Â 10 cm ). The combinated extracts were then dried over
anhydrous Na SO , filtered and evaporated to give product 2 (Table).
2
4
REFERENCES
1. Ogliaruso, M.A.; Wolfe J.F. ‘‘Synthesis of Carboxylic Acids, Esters and
Their Derivatives’’, Patai, S., Rappaport, Z., Eds., Wiley, Chichester,
1991, pp. 40–51.
2. Yamada, T.; Rhode, O.; Takai, T.; Mukaiyama, T. Chem. Lett. 1991, 5.
3. Birkinshaw, J.H.; Raistrick, H.; Ross, D.J.; Stickings, C.E. Biochem. J.
(
London) 1952, 5, 610.

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2
198
BALICKI
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3
1
1
1
˜
Received in The Netherlands October 14, 2000

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