A new method for the synthesis of acyl-diazenes using NaNO 2-Ac2O

Article abstract of DOI:10.1002/jccs.200300067

An efficient and convenient method for the synthesis of acyl-diazenes from acylhydrazines using NaNO₂-acetic anhydride as a novel oxidant agent is reported. The reaction gives excellent yields and the reaction time is not long.

Full text of DOI:10.1002/jccs.200300067

Journal of the Chinese Chemical Society, 2003, 50, 433-435
433
A New Method for the Synthesis of Acyl-diazenes Using NaNO2-Ac2O
Jian-Ping Li* (
Wan-Xin Xue (
), Ping Liu (
) and Yu-Lu Wang (
)
)
College of Chemistry & Environmental Science, Henan Normal University, Xinxiang, 453002, P. R. China
The Key Laboratory of Environmental Science and Technology of High Education of Henan Province,
Xinxiang, 453002, P. R. China
An efficient and convenient method for the synthesis of acyl-diazenes from acylhydrazines using
NaNO2-acetic anhydride as a novel oxidant agent is reported. The reaction gives excellent yields and the reac-
tion time is not long.
Keywords: Acyl-diazenes; Acylhydrazines; NaNO2-acetic anhydride.
INTRODUCTION
As we know, azo compounds have played an important
tial are useful for optical information storage; azo-dye doped
polyimide films are a kind of good photosensitive mate-
rial.14,15 Therefore, the synthesis of azo compounds is impor-
tant. Previously, there have been versatile methods of synthe-
sizing azo compounds; they have their merits, but at the same
time, they have drawbacks such as using expensive catalysts
and tedious operation.
role in many respects and have attracted great interest in or-
ganic synthesis. In previous data, the methods for the synthe-
sis of azo compounds are versatile, such as two phases cata-
lyzed dehydrogenation,1 KClO3/H2SO4/FeSO4 oxidant re-
agents,2 DMF-NOX oxidant,3 NBS(N-bromosuccinimide)/
pyridine4 and the solid state method,5,6 but these methods
haven’t been used to synthesize acyl-diazenes, and most of
them are deficient in some aspects, for example, tedious oper-
ation,7,8 expensive catalysts,7,8 strong acid or basic media.2
NaNO2-Ac2O is a known oxidation system for the rapid
and selective oxidation of a variety of alcohols into their cor-
responding carbonyl compounds. Later, it has proved to be an
efficient reagent which is used to synthesize a,b-unsaturated
acyl azo compounds from a,b-unsaturated acylhydrazine.9
The method has many advantages such as high efficiency and
simple operation. Now we have synthesized acyl-diazenes by
this method and believe that it is an important methodology
in comparison to existing ones.
On the basis of these research results, we have been
paying continuous attention to the synthesis of acyl-diazenes.
We used a new reagent or reagent system to overcome the
above limitations. During the course of experiments the
method of using NaNO2-Ac2O as the oxidation system proved
to be efficient and convenient.
Scheme
NaNO2
Ac2O
X
CONHNH
1
Y
(
CH3)2CO
X
Y
CON=N
2a-j
a: X=H
Y=NO2
Y=NO2
Y=Cl
Y=Br
Y=H
b: X=EtO
d: X=EtO
f: X=H
h: X=Br
j: X=Br
Y=NO2
Y=Cl
Y=Br
Y=Br
Y=H
RESULTS AND DISCUSSION
c: X=Br
e: X=Br
g: X=EtO
I: X=EtO
It is well known that azo compounds are widely utilized
as analytic reagents and dyes;10 they can also be used in the
material of non-linear optics, the material of optics informa-
tion stored in laser disks, and in dyes with oil solubility in
photochromy in modern technology.11 Recently, many note-
worthy studies have shown that some azo compounds possess
excellent optical memory and photoelectric properties.12,13
For example, polymer scaffolds bearing azobenzene-poten-
In this paper, using NaNO2-Ac2O as an oxidation sys-
tem, ten acyl-diazenes have been synthesized from acylhy-
drazines in excellent yields (75.6-93.9%) under mild condi-
tions. This method does not need a long time and is easy to
operate. It is efficient and convenient. In the reaction we have
found there is no inevitable relationship between the yields

434 J. Chin. Chem. Soc., Vol. 50, No. 3A, 2003
Li et al.
1-(p-Ethoxybenzoyl)-2-(p-nitrophenyl)diazene (2b)
Possible reaction mechanism
Brown needles; Yield: 87.2%; mp 139-140.5 °C; IR
(KBr) n 3105, 2985, 2860, 1702, 1606, 1572, 1523, 1505,
1448 cm-1; 1H NMR d 1.47 (t, 3H, CH3), 4.15 (q, 2H, CH2),
6.98-8.46 (m, 8H, ArH); Anal. Calcd. for C15H13N3O4: C,
60.20; H, 4.38; N, 14.04. Found: C, 60.25; H, 4.22; N, 13.99.
O
CH3
CH3C O
C
O NaO N
+
O
O
CH COONa
+CH3C O N O
3
O
CH3C O N O
CH COO
+NO
3
1-(p-Bromobenzoyl)-2-(p-nitrophenyl)diazene (2c)
O
C
H
N
O
H
1)
NO
Brown tabular; Yield: 93.9%; mp 134-136 °C; IR (KBr)
n 3010, 1705, 1610, 1587, 1530, 1503, 1438 cm-1; 1H NMR d
7.71-8.47 (m, 8H, ArH); Anal. Calcd. for C13H8BrN3O3: C,
46.73; H, 2.41; N, 12.58. Found: C, 46.59; H, 2.30; N, 12.39.
Ar
Ar
C
N
N
H
2)
H
N
Ar'
Ar
Ar'
NO
O
HNO
C N
NAr'
2HNO
CH COO
H2N2O2
H2O +N2O
1-(p-Ethoxybenzoyl)-2-(p-chlorophenyl)diazene (2d)
Brown tabular; Yield: 80.1%; mp 91-93 °C; IR (KBr) n
3068, 2984, 2863, 1696, 1606, 1581, 1510, 1494, 1450 cm-1;
1H NMR d 1.46 (t, 3H, CH3), 4.12 (q, 2H, CH2), 6.97-8.04 (m,
8H, ArH); Anal. Calcd. for C15H13ClN2O2: C, 62.40; H, 4.54;
N, 9.70. Found: C, 62.12; H, 4.31; N, 9.49.
+
H
CH3COOH
3
and the effect of electron-withdrawing and -donating groups
in the substrates. However, the substrates containing elec-
tron-withdrawing groups can make the reaction time shorter.
1
The structures of the products were confirmed by IR, H
NMR and elemental analysis.
1-(p-Bromobenzoyl)-2-(p-chlorophenyl)diazene (2e)
Orange tabular; Yield: 84.9%; mp 135-137 °C; IR
(KBr) n 3094, 1706, 1610, 1587, 1503, 1422 cm-1; 1H NMR d
7.54-7.96 (m, 8H, ArH); Anal. Calcd. for C13H8BrClN2O: C,
48.26; H, 2.49; N, 8.66. Found: C, 48.47; H, 2.28; N, 8.41.
EXPERIMENTAL SECTION
Melting points were determined with a Kofler micro
melting point apparatus and are uncorrected. IR spectra were
recorded on a SP3-300 spectrophotometer in KBr. 1H NMR
spectra were measured on a FT-80A spectrometer using TMS
as internal standard and CDCl3 as solvent. Elemental analy-
ses were performed on PE-2400 CHN elemental analyzer.
1-Benzoyl-2-(p-bromophenyl)diazene (2f)
Yellow powder; Yield: 90.3%; mp 71.5-73 °C; IR IR
(KBr) n 3067, 1687, 1604, 1583, 1487, 1466 cm-1; 1H NMR d
7.51-8.02 (m, 9H, ArH); Anal. Calcd. for C13H9BrN2O: C,
54.00; H, 3.14; N, 9.69. Found: C, 53.87; H, 2.91; N, 9.54.
General Procedure for the Preparation acyl-diazenes
(2a-2j)
1-(p-Ethoxybenzoyl)-2-(p-bromophenyl)diazene (2g)
Yellow tabular; Yield: 81.4%; mp 120.5-123 °C; IR
(KBr) n 3079, 2985, 2869, 1703, 1607, 1574, 1502, 1454
cm-1; 1H NMR d 1.46 (t, 3H, CH3), 4.13 (q, 2H, CH2), 6.94-
8.07 (m, 8H, ArH); Anal. Calcd. for C15H13BrN2O2: C, 54.07;
H, 3.93; N, 8.41. Found: C, 53.78; H, 3.62; N, 8.19.
A mixture of acylhydrazine (1 mmol), acetic anhydride
(3 mmol) and NaNO2 (3 mmol) in acetone (15 mL) was
stirred at room temperature for 0.5-1 h; an orange red or deep
red turbid solution came into being. The reaction mixture was
filtrated, then cool water was poured to the filtered material
slowly. 1 h later, the resulting precipitate was filtrated, washed
with water and dried. The crude product was recrystallised
and dried to yield the pure product.
1-(p-Bromobenzoyl)-2-(p-bromophenyl)diazene (2h)
Orange tabular; Yield: 88.6%; mp 141.5-143 °C; IR
(KBr) n 3078, 1704, 1606, 1587, 1502, 1423 cm-1; 1H NMR d
7.68-7.94 (m, 8H, ArH); Anal. Calcd. for C13H8Br2N2O: C,
42.43; H, 2.19; N, 7.61. Found: C, 42.20; H, 2.23; N, 7.28.
1-Benzoyl-2-(p-nitrophenyl)diazene (2a)
Red tabular; Yield: 89.0%; mp 96-98 °C; IR (KBr) n
3109, 1703, 1611, 1598, 1525, 1510, 1450 cm-1; 1H NMR d
7.56-8.45 (m, 9H, ArH); Anal. Calcd. for C13H9N3O3: C,
61.18; H, 3.55; N, 16.46. Found: C, 61.02; H, 3.23; N, 16.16.
1-(p-Ethoxybenzoyl)-2-phenyldiazene (2i)
Yellow tabular; Yield: 83.7%; mp 54.5-57 °C; IR (KBr)
n 3063, 2984, 2857, 1697, 1605, 1574, 1504, 1455, cm-1; 1H

A New Method for the Synthesis of Acyl-diazenes
J. Chin. Chem. Soc., Vol. 50, No. 3A, 2003 435
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8H, ArH); Anal. Calcd. for C15H14N2O2: C, 70.85; H, 5.55; N,
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1
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