Synthesis of 3-alkoxy-4-acyloxyphenylmethylene(phenyl)amines

Article abstract of DOI:10.1134/S107036320804018X

Previously unknown E isomers of azomethines (Schiff bases) were synthesized from the vanillin and vanillal esters by the reaction with aniline.

Full text of DOI:10.1134/S107036320804018X

ISSN 1070-3632, Russian Journal of General Chemistry, 2008, Vol. 78, No. 4, pp. 623–625. © Pleiades Publishing, Ltd., 2008.
Original Russian Text © E.A. Dikusar, 2008, published in Zhurnal Obshchei Khimii, 2008, Vol. 78, No. 4, pp. 642–644.
Synthesis of 3-Alkoxy-4-acyloxyphenylmethylene(phenyl)amines
E. A. Dikusar
Institute of Physical Organic Chemistry, National Academy of Sciences of Belarus,
ul. Surganova 13, Minsk, 220072 Belarus
e-mail: evgen_58@mail.ru
Received October 15, 2007
Abstract— Previously unknown E isomers of azomethines (Schiff bases) were synthesized from the vanillin
and vanillal esters by the reaction with aniline.
DOI: 10.1134/S107036320804018X
Azomethines derived from natural aldophenols,
such as vanillin and vanillal, possess high biologic
HC=N
activity. They also exhibit film-forming properties and
are heat and light sensitive. Due to that these
compounds can be used for preparing nanomaterials
RO
[1, 2]
OCR1
The aim of the present work is the synthesis of new
O
I_XL
azomethines based on the vanillin and vanillal esters
we obtained previously [3–6]. The reaction of these
compounds with aniline in absolute methanol gave
(E)-3-alkoxy-4-acyloxyphenylmethylene (phenyl)amines
I–XL containing ether and ester groups in 85–95%
R = Me, R1 = Et (I), Pr (II), Me2CH (III), Me(CH2)6
(IV), Me(CH2)7 (V), Me(CH2)8 (VI), Me(CH2)16 (VII),
H2C=CMe (VIII), cyclo-C6H11 (IX), С6Н5СН2 (X),
С6Н5С(Ме)НСН2 (XI), Z-С6H5C(H)=C(C≡N) (XII),
С6Н5 (XIII), 4-ClC6H4 (XIV), 2,4-Cl2C6H3 (XV), 2,4-
Cl2C6H3OCH2 (XVI), 4-BrC6H4 (XVII), 3-O2NC6H4
(XVIII), 3,5-(O2N)2C6H3 (XIX), MeO (XX), EtO (XXI);
R = Et, R1 = Me (XXII), Et (XXIII), Pr (XXIV), Me2CH
(XXV), Me2CHCH2 (XXVI), Me(CH2)4 (XXVII), Me
(CH2)8 (XXVIII), Me(CH2)11 (XXIX), Me(CH2)16 (XXX),
cyclo-C6H11 (XXXI), trans-С6H5C(H)=C(H) (XXXII), Z-
С6H5C(H)=C(C≡N) (XXXIII), 4-MeC6H4 (XXXIV), 2,4-
Cl2C6H3 (XXXV), 2,4-Cl2C6H3OCH2 (XXXVI), 4-
O2NC6H4 (XXXVII), 3,5-(O2N)2C6H3 (XXXVIII), MeO
(XXXIX), EtO (XL).
1
isolable yields. According to H NMR data, the purity
of the products was 98 1%.
Liquid or low-melting vanillin and vanillal esters
also readily react with aniline without solvent. By
simply mixing stoichiometric amounts of aldehyde and
aniline and subsequently heating the mixture to 60–
80°C we obtained azomethines I–IX, XX–XXX,
XXXIX, XL in yields of 99 1%. The purity of the
compounds obtained was 92
2%, which is quite
enough for preparing azomethine nanofilms by means
of thermal vacuum deposition [2]. During this proce-
dure azomethines are additionally purified to no less
than 99% purity.
Hence, the condensation in methanol results in
slightly decreased yields of target azomethines, but a
higher purity of the products is attained. The reaction
in solvent-free conditions gives higher yields of
azomethines and simplifies their isolation.
points. Azomethines do not need the additional puri-
fication and contain no admixtures of starting
compounds. The structure of azomethines I–XL was
confirmed by the elemental analyses, cryoscopic mole-
Compounds I–XL are colorless or slightly colored
crystalline compounds having well-defined melting
623

624
DIKUSAR
Yields, melting points, elemental analyses, and molecular weights of azomethines I–XL
Found, %
Calculated, %
М
Yield,
%
mp,
Comp. no.
Formula
оС
C
H
N
C
H
N
found
275.6
285.8
289.1
340.7
354.2
365.0
480.6
278.4
328.3
337.3
358.9
365.8
322.5
351.4
386.3
418.7
402.6
365.1
408.8
272.4
289.6
275.0
290.4
303.7
304.2
316.4
330.1
381.5
428.7
489.8
340.9
362.0
380.3
350.2
401.4
428.6
376.7
421.9
291.5
302.8
calculated
88
90
92
94
91
95
90
85
89
90
91
88
95
92
93
88
94
93
95
88
86
90
85
87
88
91
90
93
92
89
90
92
91
89
93
90
91
89
85
90
43–44
21–22
47–48
25–26
20–21
20–21
63–64
62–63
96–97
72.39
73.06
72.96
74.88
75.35
75.80
78.03
73.37
74.95
76.84
77.53
75.65
76.39
69.20
63.29
61.78
61.48
67.15
60.01
67.77
68.38
72.34
72.99
73.56
73.54
74.05
74.50
76.19
76.98
78.34
75.43
77.85
76.03
77.00
64.04
62.29
67.87
60.94
68.47
69.35
6.14
6.59
6.49
7.78
8.08
8.31
9.70
5.83
7.00
5.62
6.43
4.97
5.29
4.56
3.98
4.12
3.93
4.35
3.68
5.36
5.80
6.05
6.48
6.90
6.92
7.22
7.52
8.45
9.03
9.76
7.28
5.79
5.19
5.90
4.21
4.52
4.78
4.10
5.83
6.18
4.78
4.50
4.52
3.83
3.62
3.60
2.57
4.61
3.97
3.83
3.48
7.06
3.95
3.54
3.25
2.90
3.41
7.14
9.52
4.70
4.47
4.80
4.47
4.18
4.24
4.05
3.91
3.32
2.96
2.65
3.80
3.63
6.84
3.79
3.07
2.88
6.87
9.36
4.32
4.14
C17H17NO3
C18H19NO3
C18H19NO3
C22H27NO3
C23H29NO3
C24H31NO3
C32H47NO3
C18H17NO3
C21H23NO3
C22H19NO3
C24H23NO3
C24H18N2O3
C21H17NO3
C21H16ClNO3
72.07
72.71
72.71
74.76
75.17
75.56
77.85
73.20
74.75
76.50
77.19
75.38
76.12
68.95
6.05
6.44
6.44
7.70
7.95
8.19
9.59
5.80
6.87
5.54
6.21
4.74
5.17
4.41
3.78
3.98
3.93
4.28
3.59
5.30
5.72
6.05
6.44
6.80
6.80
7.12
7.42
8.41
8.98
9.73
7.17
5.70
5.08
5.89
4.14
4.31
4.65
3.94
5.72
6.11
4.94
4.71
4.71
3.96
3.81
3.67
2.84
4.74
4.15
4.06
3.75
7.33
4.23
3.83
3.50
3.26
3.41
7.44
9.97
4.91
4.68
4.94
4.71
4.50
4.50
4.30
4.13
3.54
3.20
2.76
3.99
3.77
7.07
3.90
3.38
3.15
7.18
9.65
4.68
4.47
283.3
297.4
297.4
353.5
367.5
381.5
493.7
295.3
337.4
345.4
373.5
382.4
331.4
365.8
400.3
430.3
410.3
376.4
421.4
285.3
299.3
283.3
297.4
311.4
311.4
325.4
339.4
395.5
437.6
507.8
351.4
371.4
396.4
359.4
414.3
444.3
390.4
435.4
299.3
313.4
I
II
III
IV
V
VI
VII
VIII
IX
X
XI
XII
50–51
47–48
182–183
108–109
127–128
105–106
122–123
132–133
128–129
192–193
76–77
48–49
37–38
71–72
16–17
63–64
72–73
28–29
27–28
57–58
56–57
76–77
XIII
XIVa
XVb
C21H15Cl2NO3 63.02
C22H17Cl2NO4 61.41
XVIc
XVIId
XVIII
XIX
C21H16BrNO3
C21H16N2O5
C21H15N3O7
C16H15NO4
C17H17NO4
C17H17NO3
C18H19NO3
C19H21NO3
C19H21NO3
C20H23NO3
C21H25NO3
C25H33NO3
C28H39NO3
C33H49NO3
C22H25NO3
C24H21NO3
C25H20N2O3
C23H21NO3
61.48
67.02
59.86
67.36
68.22
72.07
72.71
73.29
73.29
73.82
74.31
75.92
76.85
78.06
75.19
77.61
75.74
76.86
XX
XXI
XXII
XXIII
XXIV
XXV
XXVI
XXVII
XXVIII
XXIX
XXX
XXXI
XXXII
XXXIII
XXXIV
XXXVe
XXXVIf
XXXVII
XXXVIII
XXXIX
XL
110–111
152–153
113–114
118–119
113–114
131–132
187–188
37–38
C22H17Cl2NO3 63.78
C23H19Cl2NO4 62.18
C22H16N2O5
C22H17N3O7
C17H17NO4
C18H19NO4
67.69
60.69
68.22
69.00
101–102
a Found Cl, %: 9.45. Calculated Cl, %: 9.69. b Found Cl, %: 17.48. Calculated Cl, %: 17.71. c Found Cl, %: 16.20. Calculated Cl, %: 16.48.
d Found Br, %: 19.09. Calculated Br, %: 19.48. e Found Cl, %: 16.92. Calculated Cl, %: 17.12. f Found Cl, %: 15.70. Calculated Cl, %: 15.96.
cular weights (see table), and IR, UV, and 1H NMR
spectra.
C–HAlk (2990–2830 cm–1), C=O (1770=1740 cm–1),
C=N (1630–1627 cm–1), C–CAr (1600 and 1315 cm–1),
and C–O bonds (1280 and 1035 cm–1). The presence of
NO2 groups in compounds XVIII, XIX, XXXVII, and
XXXVIII is confirmed by the observation of
The IR spectra of azomethines I–XL contain ab-
sorption bands of C–HAr (3100–3000 and 780–680 cm–1),
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 78 No. 4 2008

625
SYNTHESIS OF 3-ALKOXY-4-ACYLOXYPHENYLMETHYLENE(PHENYL)AMINES
characteristic bands at 1541–1525 and 1349–1343 cm–1.
The IR spectra of compounds XII, XXXIII show a
characteristic C≡N absorption band at 2225–2224 cm–1.
(E)-3-Alkoxy-4-acyloxyphenylmethylene(phenyl)-
amines I–XL. A solution of 5 mmol of vanillin or
vanillal ester and 5 mmol of aniline in 30 ml of
absolute methanol was refluxed for 15 min. The
solution was filtered while hot through a folded paper
filter, cooled, and left for 10–15 h at 5°C. Crystals of
compounds I–XL formed and were filtered off on a
glass frit, washed with a little methanol, and dried in
air at 20–23°C for 1 day (see table).
The UV spectra of compounds I–XL contain the
following absorption bands, λmax, nm (log ε): 202
(4.52), 221 (4.36), 269 (4.18), and 316 (4.08). These
bands belong to the (E)-3-alkoxy-4-acyloxyphenyl-
methylene(phenyl)amine fragments.
1
The H NMR spectra of azomethines I–XXI show
(E)-3-Alkoxy-4-acyloxyphenylmethylene(phenyl)-
amines I–IX, XX–XXX, XXXIX, XL. A mixture of
5 mmol of vanillin or vanillal ester and 5 mmol of
aniline was heated carefully at 60–80°C in a ceramic
crucible for 20–30 min. The homogenous mold that
formed crystallized on cooling, and the product was
dried in air at 20–23°C for 3–5 days.
MeO singlets at δ 3.85–3.92 ppm. The EtO proton
signals of compounds XXII–XL appear as a triplet at
1.40–1.70 ppm (Me) and a quartet at 4.00–4.50 ppm
(CH2). The aromatic proton signals of azomethines I–
XL are located at δ 7.05–7.75 ppm. The HC=N proton
signals are singlets at δ 8.35–8.47 ppm, which is
characteristic of the E isomers of azomethines [1, 2, 7–9].
1
REFERENCES
The IR, UV, and H spectra of azomethines I–IX
provide evidence for the presence of the corres-
ponding ester structural fragments [1–9].
1. Dikusar, E.A., Kozlov,N.G., Tlegenov, R.T., and Uteni-
yazov, K.U., Azometiny na osnove vanilina i vanilalya
(The Vanillin- and Vanillal-based Azomethines),
Nukus: Karakalpakstan, 2007.
To confirm the assigned E configuration of the syn-
thesized azomethines, we carried out quantum-
chemical calculations of the heats of formation (Hf) of
the E and Z isomers of compounds I, XIII, XXII, and
XXXIV by the semiempirical MNDO PM3 method
using the GAMESS program [10]. Full optimization of
all interatomic distances and bond and dihedral angles
was performed. The following Hf values (kcal mol–1)
were obtained for the E isomers (the Hf for the Z
isomers are given in brackets): –53.1 (–52.1) (I), –11.6
(–10.9) (XIII), –53.5 (–53.3) (XXII), –28.2 (–27.4)
2. Dikusar, E.A., Kozlov, N.G., Potkin, V.I., Azarko, V.A.,
and Yuvchenko, A.P., Zh. Obshch. Khim., 2007, vol. 77,
no. 2, p. 306.
3. Dikusar, E.A., Vyglazov, O.G., Moiseichuk, K.L., Zhu-
kovskaya, N.A., and Kozlov, N.G., Zh. Prikl. Khim.,
2005, vol. 78, no. 1, p. 122.
4. Dikusar E.A., Kozlov N.G., Khim. Prirodn. Soedin.,
2005, no. 1, p. 74.
(XXXIV). The calculations showed that the
E
5. Dikusar, E.A. and Kozlov, N.G., Zh. Org. Khim., 2005,
vol. 41, no. 7, p. 1015.
configuration is 0.2–1.0 kcal mol–1 more favorable
than Z. These results are nicely consistent with
published data for related compounds [7–9].
6. Dikusar, E.A., Zh. Prikl. Khim., 2006, vol. 79, no. 6,
p. 1043.
EXPERIMENTAL
7. Dikusar, E.A., Kozlov, N.G., Potkin, V.I., Zelenov-
skii, V.M., Malama, A.A., and Dubovik, S.V., Khim.
Prirodn. Soedin., 2005, no. 2, p. 164.
The IR spectra were recorded on a Nicolet Protege-
460 FTIR spectrometer in KBr pellets. The UV spectra
were registered on a Varian UV-Vis Cary-300
spectrophotometer for 1 × 10–4 M methanol solutions.
8. Dikusar, E.A., Kozlov, N.G., Potkin, V.I., and Zelen-
kovskii ,V.M., Zh. Obshch. Khim., 2006, vol. 76, no. 1,
p. 87
1
The H NMR spectra were taken on a Tesla BS-587A
9. Dikusar, E.A., Kozlov, N.G., Zhukovskaya, N.A., Pot-
kin, V.I., Ogorodnikova, M.M., and Zelenkovskii, V.M.,
Zh. Org. Khim., 2006, vol. 42, no. 2, p. 223.
(100 MHz) spectrometer for 5% CDCl3 solutions
against internal TMS. The elemental analyses were
obtained on an Elementar Vario EL-III C, H, N, O, S
analyzer, determination error 0.1%. The molecular
weights (M) were evaluated cryoscopically in benzene.
10. Schmidt, M.V., Baldridge, K.K., Boatz, J.A., Elbert, S.T.,
Gordon, M.S., Jensen, J.H., Koseki, S., Matsunaga, N.,
Nguyen, K.A., Su, S.J., Midus, T.L., Dupnis, M., and
Montgomery, J.A., J. Comput. Chem., 1993, vol. 14,
no. 7, p. 1347
The vanillin and vanillal esters were synthesized
according to the procedures in [3–6].
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 78 No. 4 2008