Benzoylation of 2(3H)-benzothiazolones in the presence of 8 equivalents of zinc chloride in N,N-dimethylformamide

Article abstract of DOI:10.1080/10426500210656

The use of the mixture of aluminum chloride-N,N-dimethylformamide^1,2 (AlCl₃-DMF, 11:1) reagent in the Friedl-Crafts C acylation reaction of 2(3H)-benzothiazolones was previously reported³. These acylations reactions were f

Full text of DOI:10.1080/10426500210656

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Benzoylation of 2(3H)-benzothiazolones in the
Presence of 8 Equivalents of Zinc Chloride in N,N-
dimethylformamide
a
a
a
Faouzi Guenadil , Houcine Aichaoui & Messaoud Liacha
a
Laboratoire de Chimie Pharmaceutique, Institut de Chimie , Université Badji , Mokhtar
Published online: 27 Oct 2010.
To cite this article: Faouzi Guenadil , Houcine Aichaoui & Messaoud Liacha (2002) Benzoylation of 2(3H)-benzothiazolones
in the Presence of 8 Equivalents of Zinc Chloride in N,N-dimethylformamide, Phosphorus, Sulfur, and Silicon and the Related
Elements, 177:4, 755-757, DOI: 10.1080/10426500210656
To link to this article: http://dx.doi.org/10.1080/10426500210656
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Phosphorus, Sulfur and Silicon, 2002, Vol. 177:755–757
Copyright �C 2002 Taylor & Francis
1
042-6507/02 $12.00 + .00
BENZOYLATION OF 2(3H)-BENZOTHIAZOLONES IN
THE PRESENCE OF 8 EQUIVALENTS OF ZINC
CHLORIDE IN N,N-DIMETHYLFORMAMIDE
Faouzi Guenadil, Houcine Aichaoui, and Messaoud Liacha
Laboratoire de Chimie Pharmaceutique, Institut de Chimie,
Universit e´ Badji Mokhtar
(Received July 17, 2001; accepted September 25, 2001)
The use of the mixture of aluminum chloride-N,N-dimethyl-
1
,2
formamide (AlCl -DMF, 11:1) reagent in the Friedl-Crafts C acyla-
3
3
tion reaction of 2(3H)-benzothiazolones was previously reported.
These acylations reactions were found to proceed with high regios-
electivity. The precise position of acylation was uniquivocally as-
signed by x-ray single-crystal defraction in the case of 6-benzoyl-2(3H)-
4
benzothiazolone. The assignment of the position of acylation was ex-
1
3
tended to other compounds by the use of high-field H-NMR.
Keywords: 2(3H)-benzothiazolones; 6-benzoyl-2(3H)-benzothiazol-
ones; acylation reaction; benzoyl chloride; benzoylation; zinc chloride
6
2
-Benzoyl-2(3H)-benzothiazolones are obtained by the reaction of
(3H)-benzothiazolones with benzoic acid in polyphosporic acid as sol-
3
vent and catalyst or with benzoyl chloride in the mixture AlCl3-DMF.
We conducted the reaction of 2(3H)-benzothiazolones (1a–b) with
benzoyl chloride in the presence of 8 equivalents of zinc chloride in N,N-
5
�
dimethylformamide as solvent at 140 C for 2 h and obtained the cor-
responding 6-benzoyl-2(3H)-benzothiazolones (2a–b) with high yields
(
Scheme 1).
The benzoylation of 2(3H)-benzothiazolones with the mixture of zinc
chloride-DMF was realized for the first time.
Address correspondence to Dr. F. Guenadil, Lab. de Chimie Pharmac., Institut de
Chimie, Universit e´ Badji Mokhtar, Bp. 12 El Hadjar Annaba, Algerie.
7
55

7
56
F. Guenadil et al.
SCHEME 1
EXPERIMENTAL
Melting points were determined using an electrothermal melting point
apparatus and are uncorrected. The IR spectra were recorded on a
1
Shimadzu 40-spectrometer and the H-NMR. Spectra were recorded
using a Bruker 80 MHz spectrometer. Chemical shifts are reported in
ppm with tetramethylsilane as internal standard and were compatible
with the compounds obtained by the AlCl3-DMF method.
6
-Benzoyl-2(3H)-benzothiazolone (2a)
Dimethyl formamide (0.037 mol, 2.8 ml) was slowly added to zinc chlo-
ride (0.104 mol, 14.18 g). The mixture was stirred and maintained
�
at 75 C and 2(3H)-benzothiazolone (1a) (0.013 mol, 2 g) and benzoyl
chloride (0.0195 mol, 2.73 ml) were added. The reaction mixture was
�
warmed at 140 C under stirring for 2 h. After cooling the complex was
decomposed by addition of ice water. The resulting residue was stirred
for 1 h, filtered, washed with water, and recrystallized from ethanol to
�
give the title compound (yield: 82%): m.p. 216–217 C; IR (KBr): 3220,
1
8
�
1
1
680, 1630 cm ; H-NMR. (DMSO-D6, � in ppm) 7.23 (d, 1 H, Jo =
.40 Hz); 7.60 (m, 6H); 8.00 (d, 1H, jm = 1.7 Hz); 12.10 (s, 1H, amide).
3
-Methyl-6-benzoyl-2(3H) benzothiazolone (2b)
Dimethyl formamide (0.037 mol, 2.8 ml) was slowly added to zinc chlo-
ride (0.104 mol, 14.18 g). The mixture was stirred and maintained
�
at 75 C and 3-methyl-2(3H)-benzothiazolone (1b) (0.013 mol, 2.16 g)
and benzoyl chloride (0.0195 mol, 2.73 ml) were added. The reaction
�
mixture was warmed at 140 C under stirring for 2 h. After cooling
the complex was decomposed by addition of ice water. The resulting
residue was stirred for 1 h, filtered, washed with water, and recrys-
tallized from ethanol to give the title compound (yield: 86%): m.p. 147–
�
� 1
1
1
48 C; IR (KBr): 1670, 1630 cm ; H-NMR. (DMSO-D6, � in ppm) 3.46
(
s, N CH3); 7.35 (d, 1H, J = 8.70 Hz); 7.50 (m, 7H).

Benzoyl-benzothiazolones
757
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