J. CHEM. RESEARCH (S), 1998 47
ꢀ
1
ated by the electron transfer from zinc to nitrobenzene may
react rapidly as a nucleophile toward the acetic anhydride
electrophile to form an intermediate, 4. Following electron
transfer, loss of the acetate anion could produce the nitroso
intermediate. Through similar continuous electron transfer
and acetylation, the nitroso intermediate may be transformed
to an N,O-diacetylated N-arylhydroxylamine.
s); v /cm (Nujol) 3057, 2993, 1799, 1694, 1430, 1185 (Found:
max
m/z, 207.0895. C11
N-(Acetyloxy)-N-(3-methylphenyl)acetamide (2c). Yield: 78%
liquid); TLC (30% ethyl acetate–hexane) R 0.39; d (300 MHz,
CDCl ) 7.35–7.21 (4 H, m), 2.38 (3 H, s), 2.19 (3 H, s), 2.06 (3 H,
s); vmax/cm (Nujol) 3057, 2993, 1799, 1688, 1378 (Found: m/z,
07.0899. C11 requires M , 207.0895).
N-(Acetyloxy)-N-(4-methylphenyl)acetamide (2d). Yield: 85%
(liquid); TLC (30% ethyl acetate–hexane) R 0.39; d (300 MHz,
CDCl ) 7.35 (2 H, d, J 8.4 Hz), 7.25 (2 H, d, J 8.4 Hz), 2.38 (3 H, s),
H13NO
3
requires M
r
, 207.0895).
(
f
H
3
ꢀ1
2
H13NO
3
r
In conclusion, we have now established a mild and novel
reaction route for N,O-diacetylated hydroxylamines by using
Ac O/Zn/CH Cl , which would be a useful chemical method
f
H
3
ꢀ
1
2
1
2
.18 (3 H, s), 2.03 (3 H, s); vmax/cm (Nujol) 3064, 2992, 1799,
688, 1428, 1284 (Found: m/z, 207.0888. C11
2
2
2
H13NO
3
requires M ,
r
for the reductive diacetylation of nitroaromatics. As far as
dehalogenation is concerned, our chemical method is
superior to the electrochemical one.
07.0895).
N-(Acetyloxy)-N-(3-bromophenyl)acetamide (2e). Yield: 91%
(liquid); TLC (30% ethyl acetate–hexane) R 0.39; d (300 MHz,
f
H
CDCl
m), 2.23 (3 H, s), 2.10 (3 H, s); vmax/cm (Nujol) 3057, 2989, 1805,
703, 1589, 1425, 1272 (Found: m/z, 270.9856. C10 10BrNO
requires M , 270.9844).
N-(Acetyloxy)-N-(9H-fluoren-2-yl)acetamide (2f). Yield: 83%
liquid); TLC (30% ethyl acetate–hexane) R 0.34; d (300 MHz,
CDCl ) 7.74–7.72 (2 H, m), 7.61 (1 H, s), 7.50–7.42 (2 H, m),
.37–7.26 (2 H, m), 3.82 (2 H, s), 2.17 (3 H, s), 2.07 (3 H, s); vmax
3
) 7.65 (1 H, t, J 1.9 Hz), 7.44–7.41 (2 H, m), 7.31–7.29 (1 H,
ꢀ1
Experimental
1
H
3
Most of the chemical reagents were purchased from Aldrich and
used without further purification in most cases. Acetic anhydride
was purchased from Duksan P. and purified by a standard method.
Zinc powder was purchased from Junsei Chemical Co. and was
used without further purification. Solvents were purchased and
dried by the usual laboratory techniques. Solvents were deoxygen-
ated before use by bubbling argon through them.
r
(
f
H
3
7
/
ꢀ1
cm (Nujol) 3057, 2988, 1799, 1691, 1425, 1272, 1187 (Found: m/z,
81.1046. C17 requires M , 281.1052).
N-(Acetyloxy)-N-(2-chloropyridin-5-yl)acetamide (2g). Yield:
93% (liquid); TLC (30% ethyl acetate–hexane) R 0.32; d (300
2
H15NO
3
r
Analytical GC was performed on a Donam 6200 gas chromato-
graph equipped with a DB-1 column and Hitachi D-2500 integra-
1
tor. H NMR spectra were recorded on a 300 MHz Bruker instru-
f
H
1
3
MHz, CDCl ) 8.49 (1 H, d, J 2.6 Hz), 7.85 (1 H, dd, J 2.6 and 8.5
ment and C NMR spectra were recorded on a 125 MHz Bruker
instrument. Chemical shifts are in ppm from tetramethylsilane
3
ꢀ1
Hz), 7.39 (1 H, d, J 8.5 Hz), 2.26 (3 H, s), 2.16 (3 H, s); vmax/cm
Nujol) 3063, 2983, 1810, 1703, 1612, 1425, 1266 (Found: m/z,
28.0286. C ClN requires M , 228.0301).
(
2
(
TMS). High-resolution mass spectra (EI) were recorded on a Jeol
9
H
9
2
O
3
r
JMS-DX 303 mass spectrometer. Infrared spectra (IR) were
recorded on a Nicolet 205 FT-IR.
Most products were isolated by flash column chromatography on
silica gel (70–230 mesh ATSM, Merck) with eluents of mixed
solvents (hexane and ethyl acetate). GC yields were determined by
using an internal standard (toluene) and were corrected with pre-
determined response factors.
This work was supported by the Korea Science and
Engineering Foundation (951-0301-011-2) and partly by
Kwangwoon University.
General Procedure for the Diacetylation of Nitro- or Nitroso-aro-
Received, 4th August 1997; Accepted, 4th September 1997
Paper E/7/05670B
matics.sZinc powder (327 mg, 5 mmol) and CH
2
Cl (3 ml) were
2
placed in a 20 ml vial equipped with a rubber septum. Acetic
anhydride (0.38 ml, 4 mmol) was added to the reaction mixture
followed by nitrobenzene (0.10 ml, 1 mmol). The mixture was
stirred under nitrogen or argon at room temperature. It was then
References
quenched with 10% NH
4
Cl and extracted with CH
2
Cl
4
2
(3Å20 ml).
The combined CH Cl extract was dried over MgSO
2
2
and the sol-
1 Recent reviews include (a) J. A. Miller, Cancer Res., 1970, 30, 559;
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2 A. K. Koul, J. M. Bachhawat, N. S. Remegowda, B. Prashad and
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vent evaporated. The GC yield was determined with an internal
standard and, if necessary, the products were isolated by flash
column chromatography with ethyl acetate–hexane co-solvent. In
general, d
C
(125 MHz, CDCl
3
) for OCOCH
3
and NCOCH of the
3
following compounds were 167–168 and 165–166, respectively.
N-(Acetyloxy)-N-phenylacetamide (2a).sThe compound was
obtained as a liquid. The yield was 87% when nitrobenzene was
starting substrate, and 95% with nitrosobenzene. TLC (30% ethyl
acetate–hexane) R
f
0.37; d
H
(300 MHz, CDCl ) 7.48–7.40 (5 H, m),
3
ꢀ1
2
1
1
.20 (3 H, s), 2.07 (3 H, s); vmax/cm (Nujol) 3059, 2993, 1803,
694, 1600, 1496 (Found: m/z, 193.0754. C10
H11NO
3
requires M ,
r
93.0739).
4 (a) L. H. Klemm, P. E. Iversion and H. Lund, Acta Chem. Scand.,
Sect. B, 1974, 28, 593; (b) L. Christensen and P. E. Iversion, Acta
Chem. Scand., Sect. B, 1979, 33, 352; (c) J. H. Wagenknecht and G.
V. Johnson, J. Electrochem. Soc., 1987, 134, 2754.
N-(Acetyloxy)-N-(2-methylphenyl)acetamide (2b). Yield: 73%
(liquid); TLC (30% ethyl acetate–hexane) R
f
0.38; d
H
(300 MHz,
CDCl
3
) 7.51–7.27 (4 H, m), 2.38 (3 H, s), 2.17 (3 H, s), 1.92 (3 H,