New method of synthesis of functionally substituted aromatic aldehydes

Full text of DOI:10.1134/S1070363216090267

ISSN 1070-3632, Russian Journal of General Chemistry, 2016, Vol. 86, No. 9, pp. 2129–2131. © Pleiades Publishing, Ltd., 2016.
Original Russian Text © M.B. Gazizov, S.Yu. Ivanova, Sh.N. Ibragimov, L.R. Bagauva, R.A. Khairullin, K.A. Medvedeva, 2016, published in Zhurnal
Obshchei Khimii, 2016, Vol. 86, No. 9, pp. 1567–1569.
LETTERS
TO THE EDITOR
New Method of Synthesis
of Functionally Substituted Aromatic Aldehydes
M. B. Gazizov*, S. Yu. Ivanova, Sh. N. Ibragimov,
L. R. Bagauva, R. A. Khairullin, and K. A. Medvedeva
Kazan State Technological University, ul. K. Marksa 68, Kazan, Tatarstan, 420015 Russia
*e-mail: mukattisg@mail.ru
Received April 26, 2016
Keywords: aromatic aldehydes, benzaldehyde acetal, catalytic debromomethoxylation
DOI: 10.1134/S1070363216090267
We have previously carried out for the first time the
reaction of methyl esters of P(IV) acids with dihalo-
methylarenes resulting in the formation of aromatic
aldehydes and P(IV) pyro-compounds [1, 2]. The main
disadvantages of this method are high temperature
(160–180°C) and high cost of P(IV) acids esters. In the
last decade two promising method of aromatic mono-
aldehydes preparation from dihalomethylarenes have
been developed: heating a mixture of dihalomethyl-
arenes with a large excess of dimethyl sulfoxide [3] or
pyridine [4] at 70–120°C for 1–18 h followed by treat-
ing the reaction mixture with water. However, isola-
tion of pure aldehydes is labor consuming.
We suggest for the first time to synthesize func-
tionally substituted aromatic aldehydes via catalytic de-
bromomethoxylation of dibromomethylarenes 1 with
the use of benzaldehyde dimethyl acetal 2. Zinc chloride
being a soft Lewis acid was used as a catalyst, which
did not form a stable complex with the aldehyde group.
CHBr2
CHO
0.1 mol % ZnCl2
−2MeBr
+ PhCH(OMe)2
X
X + PhCHO
2
1
3
4
1, 3: X= 4-CHO (a), 4-CH(OMe)2 (b), 4-COOMe (c), 3-OCOMe (d).
Some experiments showed that a catalyst-free
thoxymethyl)benzenecarbaldehyde 3b were involved
into debromomethoxylation, and the major reaction
product was terephthalaldehyde 3a. Compound 3b was
detected only by 1H NMR and chromatography
methods. Moreover, since compound 1b contains both
dibromomethyl and acetal groups, we expected their
intermolecular interactions. Indeed, the formation of
terephthalaldehyde 3a with 96% yield occurred when
adding catalytic amounts of ZnCl2 to compound 1b.
reaction between compounds 1 and 2 occurs only at
220°C. The reaction was complete in 2 h at 50°C and
1 h at 80°C when using 0.1 mol % of ZnCl2. It was
carried out in the solvent-free conditions.
During the reaction such important functional
groups as methoxycarbonyl and carbonyl were not
affected. Acetal moieties of dibromide 1b and 4-(dime-
ZnCl2
50oC
4-OCHC6H4CHO + 4MeBr
2 4-Br2CHC6H4CH(OMe)2
1b
3а
2129

2130
GAZIZOV et al.
Generally, depending on the reactant ratio the
reaction of tetrabromide 1e with benzaldehyde
dimethyl acetal 2 may result in the formation of three
aldehydes: monoaldehyde 1a, dialdehyde 3a, and
benzaldehyde 4. Tetrabromide 1d might not react
completely.
0.1 mol % ZnCl2
4-Br2CHC6H4CHBr2 + PhCH(OMe)2
4-Br2CHC6H4CHO + 4-OCHC6H4CHO + PhCHO
1e
1а
3а
2
4
1
In the H NMR spectrum of the reaction mixture
(1e : 2 = 1.0 : 2.1) there was no signal at 6.61 ppm
corresponding to the proton of dibromomethyl group.
Terephthalaldehyde 3a was isolated in 90% yield.
b. A mixture of 3 g (0.007 mol) of tetrabromide 1e,
2.28 g (0.015 mol) of acetal 2, and 0.1 g (0.0007 mol)
of zinc chloride in 5 mL of isooctane was heated at 50°C
for 2.5 h. Isooctane solution was decanted, and the
residue was further extracted with 10 mL of isooctane.
Compound 3a (0.85 g, 89%) was isolated from the
combined isooctane solutions. The mother liquor
yielded 0.43 g (29%) of benzaldehyde 4.
In order to apply this reaction to the synthesis of 4-
(dibromomethyl)benzenecarbaldehyde 1a [5] we
varied the reactants ratio. At a ratio of 1.0 : 1.5,
tetrabromide 1e was absent in the reaction mixture
1
(according to H NMR). Compounds 1a and 3a were
c. A mixture of 3 g (0.007 mol) of tetrabromide 1e,
2.28 g (0.015 mol) of acetal 2, and 0.1 g (0.0007 mol)
of zinc chloride in 5 mL of isooctane was heated at 80°C
for 1 h. Compound 3a (0.86 g, 90%) was isolated from
the combined isooctane solutions. The mother liquor
yielded 0.4 g (28%) of benzaldehyde 4.
isolated in pure state by column chromatography
eluting with benzene with the yields of 11 and 64%,
respectively. Thus, in the absence of tetrabromide 1e in
the reaction mixture the main reaction product was
terephthalaldehyde 3a, i. e., the second dibromomethyl
group of 1e was affected, and the yield of 1a was
small.
d. Ratio of 1.0 : 1.5. A mixture of 3 g (0.007 mol)
of tetrabromide 1e, 1.67 g (0.011 mol) of acetal 2, and
0.1 g (0.0007 mol) of zinc chloride in 5 mL of
isooctane was heated at 80°C for 1 h. Isooctane solu-
tion provided 0.5 g (53%) of compound 3a. The
residue was chromatographed (eluent – benzene) to
give 0.66 g (55%) of benzaldehyde 4, 0.22 g (11%) of
compound 1a, and 0.11 g (11%) of compound 3a.
However, when the ratio of the reagents of 1 : 1,
17.7% of the starting tetrabromide 1e can be isolated.
The yields of chromatographically isolated products
1a, 3a, and 4 reached 22.6, 53.2, and 40.5%, respect-
tively. Hence, when using the equimolar reactants ratio
the yields of the target compound 1a can be increased
2 times.
The reaction of 4-(dibromomethyl)benzenecarb-
aldehyde 1a with acetal 2. A mixture of 1 g (0.0036 mol)
of compound 1a, 0.58 g (0.0038 mol) of acetal 2 and
0.049 g (0.00036 mol) of zinc chloride in 5 mL
isooctane was heated at 80°C for 1 h. Compound 3a
(0.4 g (83%) was isolated from isooctane solution. The
mother liquor yielded 0.21 g (55%) of benzaldehyde 4.
The starting acetal 2 was easily regenerated by
treating the formed benzaldehyde with trimethyl ortho-
formate.
In summary, we developed for the first time the
method of the synthesis of functionally substituted aromatic
aldehydes by catalytic debromomethoxylation of dibromo-
methylarenes using benzaldehyde dimethyl acetal.
The reaction of 1-(dibromomethyl)-4-(dimethyl-
methoxymethyl)benzene 1b with acetal 2. A mixture
of 1 g (0.0031 mol) of compound 1b, 0.5 g (0.0033 mol)
of acetal 2, and 0.04 g (0.00031 mol) of zinc chloride
was heated at 50°C for 1.5 h. Compound 3a (0.15 g,
36%) was isolated by extraction with isooctane. The
mother liquor was chromatographed (eluent benzene :
ether = 19 : 1) to provide fractions containing 0.1 g
(30%) of benzaldehyde 4, 0.06 g (15%) of dialdehyde
3a, as well as a fraction consisting of compounds 2 and
3b, which were detected by TLC (Sorbfil, benzene).
The reaction of 1,4-bis(dibromomethyl)benzene
1e with benzaldehyde dimethyl acetal 2. Ratio of
1.0 : 2.1. a. A mixture of 3 g (0.007 mol) of tetra-
bromide 1e, 2.28 g (0.015 mol) of acetal 2, and 0.1 g
(0.0007 mol) of zinc chloride was heated at 50°C for
2 h. Extraction with isooctane yielded 0.8 g (84%) of
compound 3a as colorless crystals melting at 115–116°C
(mp 115–116°C [6]). The mother liquor yielded 0.41 g
(28%) of benzaldehyde 4.
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 86 No. 9 2016

2131
NEW METHOD OF SYNTHESIS OF FUNCTIONALLY SUBSTITUTED
Transformation of 1-(dibromomethyl)-4-(dimethyl- ACKNOWLEDGMENTS
methoxymethyl)benzene 1b into dialdehyde 3a
under the action of catalytic amounts of zinc
chloride. A mixture of 1.1 g (0.0034 mol) of com-
pound 1b and 0.046 g (0.00034 mol) of zinc chloride
was heated at 50°C for 1 h. Extraction with isooctane
allowed isolating 0.44 g (96%) of compound 3a.
This work was financially supported by the Ministry
of Education and Science of the Russian Federation in
the frame of the base part of governmental contract
(no. 56/2014).
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С6Н4), 10.08 s (1Н, СНО). Benzaldehyde 4 (0.1 g,
29%) was isolated from mother liquor.
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1
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1
0.2 g (29%) of benzaldehyde was isolated. H NMR
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internal reference.
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 86 No. 9 2016