1752
O. M. E. El-Dusouqui, M. M. Abdelkhalik, N. A. Al-Awadi and M. H. Elnagdi
Vol 45
which involve coupling the 1,2,3-triazol-1-yl propanone 4 with
the corresponding aromatic diazonium salts.
ascertained to be (l-arylamino-2-imidazolyl)ethanone l0a-
c of molecular masses 201 from 3a, 235 from 3b and 215
from 3c. These products are believed to be formed via
elimination of molecular nitrogen from 3a-c leading to the
biradical 8, which is in resonance with its canonical form
9. This biradical is directly cyclized into N-arylamino-
acetyl imidazoles l0a-c. It is most likely that 2-acetyl-
imidazole 12 results from further pyrolytic elimination of
incipient aminoarene from N-arylaminoacetylimidazole
10 via a transition state similar to the quazi-aromatic six-
membered transition state suggested earlier to account for
the pyrolytic behavior of arylhydrazonoketones [7]
(Scheme 3). Loss of an arylamino moiety to give the
corresponding imidazole derivative and arylamine has
been reported for benzimidazole 2 [4].
(Z)-1-(2-Phenylhydrazono)-1-(1H-1,2,3-triazol-1-yl)pro-
panone 3a. Yield 71% (1.62 g); brownish crystals from ethanol;
m.p. 135-136 °C; IR (KBr): ꢀ/cm-1: 3135 (NH), 1672 (C=O); MS:
1
m/z = 229 (M+.); H NMR (DMSO-d6): ꢁ (ppm) = 2.56 (s, 3H,
CH3), 7.07 (t, 1H, J = 7.20 Hz, phenyl-H), 7.37 (t, 2H, J = 7.32
Hz, phenyl-H), 7.45 (d, 2H, J = 7.80 Hz, phenyl-H), 7.99 (d, 1H,
J = 0.8 Hz, triazolyl-H), 8.30 (d, 1H, J = 0.8 Hz, triazolyl-H),
10.89 (br. s, 1H, NH). Anal. Calcd. for C11H11N5O (229.10): C
57.63, H 4.84, N 30.55. Found C 56.99, H 4.65, N 30.21.
(Z)-1-[2-(4-Chlorophenyl)hydrazono)]-1-(1H-1,2,3-triazol-
1-yl)]propanone 3b. Yield 82% (2.15 g); yellow crystals from
ethanol; m.p. 209 °C; IR (KBr): ꢀ/cm-1: 3210 (NH), 1667
1
(C=O); MS: m/z = 263 (M+.); H NMR (DMSO-d6): ꢁ (ppm) =
2.56 (s, 3H, CH3), 7.42 (d, 2H, J = 8.8 Hz, chlorophenyl-H),
7.46 (d, 2H, J = 8.8 Hz, chlorophenyl-H), 8.00 (d, 1H, J = 0.75
Hz, triazolyl-H), 8.30 (d, 1H, J = 0.75 Hz, triazolyl-H), 10.94
(br. s, 1H, NH). Anal. Calcd. for C11H10ClN5O (263.68): C
50.10, H 3.82, N 26.56. Found C 49.80, H 3.90, N 26.41.
Scheme 3
.
N
N
H
(Z)-1-[2-(p-Tolylhydrazono)]-1-(1H-1,2,3-triazol-1-yl)]-
propanone 3c. Yield 80% (1.95 g); reddish crystals from
ethanol; m.p. 129 °C; IR (KBr): ꢀ/cm-1: 3231 (NH), 1671
N
.
.
N
.
N
Ar
O
H
H
N
- N2
N
N
Ar
Ar
N
N
1
(C=O); MS: m/z = 243 (M+.); H NMR (DMSO-d6): ꢁ (ppm) =
N
O
O
CH3
2.27 (s, 3H, CH3), 2.55 (s, 3H, CH3), 7.18 (d, 2H, J = 8.2 Hz,
tolyl-H), 7.32 (d, 2H, J = 8.2 Hz, tolyl-H), 7.99 (d, 1H, J = 0.75
Hz, triazolyl-H), 8.29 (d, 1H, J = 0.75 Hz, triazolyl-H), 10.83
(br. s, 1H, NH). Anal. Calcd. for C12H13N5O (243.26): C 59.25,
H 5.39, N 28.79. Found C 59.40, H 5.39, N 28.35.
CH3
CH3
8
9
3a-c
Ar
N
N
N
NH
Gas-Phase Pyrolysis.
H
OH
CH3
O
CH3
..
O
N
N
General Procedure for Pyrolysis of 3a-c. Each of
compounds 3a-c was introduced in the reaction tube (1.5x12 cm
Pyrex), cooled in liquid nitrogen, sealed under vacuum (0.06
mbar) and placed in the pyrolyser for 900 s at a temperature
verified for complete pyrolysis. The pyrolysate was then
separated into its constituents by preparative TLC (MERCK, 12
PSC-Platten 20x20 cm, Silica gel 60 F254 2mm) using
chloroform: petroleum ether (40:60) in 80:20 ratio as eluent, and
each constituent was collected, analyzed and characterized. The
techniques used include 1H NMR and high performance GC/MS.
A full description of the reactor and attachments has been
detailed in earlier publications [1,4].
N
CH3
10
12
11
EXPERIMENTAL
General. Melting points were determined on a Shimadzu-
Gallenkamp apparatus and are uncorrected. Elemental analysis was
by means of a LECO CHNS-932 Elemental Analyzer. NMR spectra
were measured using a Bruker DPX 400 MHz superconducting
spectrometer, and FT-IR measurements were from a Perkin Elmer
2000 FT-IR system. Mass spectrometric analysis was carried out on
a VG-Autospec-Q high performance tri-sector GC/MS/MS, and the
instrument for HPLC was an Agilent 1100 series LC/MSD with an
API-ES/APCI ionization mode.
1-[1-(Phenylamino)-1H-imidazol-2-yl]ethanone 10a. MS:
1
m/z for C11H11N3O (201.23) = 201 (M+.), H NMR (CDCl3): ꢁ
(ppm) = 2.64 (s, 3H, CH3), 6.82(d, 1H, J = 0.9 Hz, imidazolyl -
H), 6.93 (d, 1H, J = 0.9 Hz, imidazolyl-H), 7.49 (d, 2H, J = 8.05
Hz, phenyl-H), 7.55 (t, 3H, J = 8.05 Hz, phenyl-H), 10.40 (br. s,
1H, NH).
Synthesis.
1-[1-(4-Chlorophenylamino)-1H-imidazol-2-yl]ethanone
1
10b. MS: m/z for C11H10ClN3O (235.67) = 235 (M+.), H NMR
1-(1H-1,2,3-triazol-1-yl)propanone 4. Compound 4 was
prepared following published procedure [4] which involves
reacting 1H-1,2,3-triazole with chloroacetone in acetone in the
presence of triethylamine. Yield 62% (7.75 g); white crystals
from benzene; m.p. 245°C; IR (KBr): ꢀ/cm-1: 1630 (C=O); MS:
(CDCl3): ꢁ (ppm) = 2.68 (s, 3H, CH3), 7.21 (d, 1H, J = 1.0 Hz,
imidazolyl-H), 7.25 (d, 1H, J = 1.0 Hz, imidazolyl -H), 7.47 (d,
2H, J = 8.7 Hz, chlorophenyl-H), 7.56 (d, 2H, J = 8.7 Hz,
chlorophenyl-H), 10.43 (br. s, 1H, NH).
m/z = 125 (M+.); H NMR (DMSO-d6): ꢁ (ppm) = 2.33 (s, 3H,
1
1-[1-(p-Toluidino)-1H-imidazol-2-yl]ethanone 10c. MS: m/z
1
for C12H13N3O (215.25) = 215 (M+.), H NMR (CDCl3): ꢁ (ppm)
CH3), 5.50 (s, 2H, CH2), 7.96 (d, 1H, J = 1.00 Hz, triazolyl-
H), 8.28 (d, 1H, J = 1.0 Hz, triazolyl-H). Anal. Calcd. for
C5H7N3O (125.13): C 47.99, H 5.64, N 33.58. Found C 48.25, H
5.60, N 33.76.
General procedure for the preparation of compounds 3a-c.
Compounds 3a-c were prepared following earlier procedures [8]
= 2.38 (s, 3H, CH3), 2.70 (s, 3H, CH3), 6.62 (d, 1H, J = 0.9 Hz,
imidazolyl-H), 7.06 (d, 1H, J = 0.9 Hz, imidazolyl -H), 7.15 (d,
2H, J = 8.4 Hz), 7.49 (d, 2H, J = 8.4 Hz), 10.40 (br. s, 1H, NH).
1-(1H-Imidazol-2-yl)ethanone 12. m.p. 136 °C (Lit [5] mp
136-137 °C); IR (KBr): ꢀ/cm-1: 1680 (C=O); MS: m/z = 111