Regiospecific chlorination of xylenes using K-10 montmorrillonite clay

Article abstract of DOI:10.1080/00397910801979338

Regiospecific chlorination of xylenes has been developed by employing NCS as a reagent and K-10 montmorrillonite clay as a solid support. Copyright Taylor & Francis Group, LLC.

Full text of DOI:10.1080/00397910801979338

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Regiospecific Chlorination
of Xylenes Using K-10
Montmorrillonite Clay
a
B. T. S. Thirumamagal , Sureshbabu Narayanasamy
b
a
&
R. Venkatesan
a
Department of Organic Chemistry, University of
Madras, Guindy Campus, Chennai, India
b
College of pharmacy, Ohio State University,
Columbus, Ohio, USA
Published online: 25 Aug 2010.
To cite this article: B. T. S. Thirumamagal , Sureshbabu Narayanasamy & R.
Venkatesan (2008) Regiospecific Chlorination of Xylenes Using K-10 Montmorrillonite
Clay, Synthetic Communications: An International Journal for Rapid Communication of
Synthetic Organic Chemistry, 38:16, 2820-2825, DOI: 10.1080/00397910801979338
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1
Synthetic Communications , 38: 2820–2825, 2008
Copyright # Taylor & Francis Group, LLC
ISSN: 0039-7911 print/1532-2432 online
DOI: 10.1080/00397910801979338
Regiospecific Chlorination of Xylenes Using K-10
Montmorrillonite Clay
1
B. T. S. Thirumamagal, Sureshbabu Narayanasamy, and
2
1
R. Venkatesan
1
Department of Organic Chemistry, University of Madras, Guindy Campus,
Chennai, India
2
College of pharmacy, Ohio State University, Columbus, Ohio, USA
Abstract: Regiospecific chlorination of xylenes has been developed by employ-
ing NCS as a reagent and K-10 montmorrillonite clay as a solid support.
Keywords: a-Chloroxylene, K-10 montmoriillonite clay, NCS, regiospecific
chlorination
INTRODUCTION
Chlorination of activated benzenoid rings such as xylene derivatives is a
significant synthesis that can produce several important compounds (viz.,
[1]
[2]
monochlorophthalic acids and aromatic aldehydes. ) In particular,
a-chloroxylene is a useful chemical intermediate for herbicides and has
been used in the preparative route to benzocyclobutene as well as in
[
3]
[4]
the radical, cationic polymerisations. The most common methods for
the nuclear chlorination of xylene derivatives are by the treatment of
xylene with Cl under ultraviolet (UV) irradiation and by using calcium
2
[
5]
hypochlorite in aqueous acetone=acetic acid. Although there are several
methods for the ring chlorination of xylenes, there has not been a great
deal of research focusing on the regiospecific chlorination of xylenes
from easily available N-chloro succinimide (NCS) in the presence of a
heterogeneous catalyst. Heterogeneous catalysis is distinctive in organic
Received October 29, 2007
Address correspondence to B. T. S. Thirumamagal, Department of Organic
Chemistry, University of Madras, Guindy Campus, Chennai 25, India. E-mail:
srinivasaraghava.2@osu.edu
2
820

Regiospecific Chlorination of Xylenes
2821
[
6]
synthesis. Clay minerals are silicates of aluminium with layered
structures and are exploited very well in the synthesis of organic
compounds for their striking features such as high catalytic activity,
[
7–10]
versatility, selectivity, recyclability, and low cost.
Herein, we
communicate the results of the regiospecific chlorination of xylenes with
N-chlorosuccinimide in the presence of clay.
RESULTS
In the present study, the reaction of o-xylene in 1,2-dichloroethane with
NCS in the presence of K-10 montmorrillonite clay afforded 4-chloro-
1
,2-xylene as a liquid in 65% yield. The H NMR spectrum of 4 exhibited
1
two 3H singlets at d 2.35 and 2.37 due to the two methyl groups, and a
H multiplet at d 7.1–7.2 due to aromatic hydrogens. The product forma-
3
1
tion was very simplistic in the case of m- and p-xylene. The H NMR
spectra of other two chloro xylenes 5 and 6 were consistent with their
structure. In the case of anisole, p-chloroanisole was obtained in 70%
yield. From the high performance liquid chromatography (HPLC) stu-
dies, the product formation was further confirmed. In the absence of
K-10 montmorrillonite clay, the side-chain chlorination took place pre-
1
dominantly in all the xylenes. The H NMR spectrum of 7 exhibited a
3
H singlet at d 2.35 due to the methyl group, a 2H singlet at d 4.3 due
to the benzylic group, and a 4H multiplet at d 7.1–7.3 due to aromatic
hydrogens. Thus, clay plays a vital role in deciding the region of chlori-
nation. The results summarized in Table 1 clearly demonstrate the
competence, selectivity, and catalytic activity of clay in the chlorination
reactions. In view of the fact that clay is acidic in nature, it can be
Table 1. Regiospecific chlorination of xylenes in the presence of clay
Ring chlorinated product (%) Side-chain
chlorinated
S. no. Compound Conversion (%) Ortho
Para
Poly product (%)
1
2
3
4
o-Xylene
m-Xylene
p-Xylene
Anisole
65
60
62
70
3
—
62
—
62
60
—
70
—
—
—
—
0
0
0
—
In the absence of clay
a
5
6
7
o-Xylene
m-Xylene
p-Xylene
67
70
63
—
—
—
—
—
—
—
—
—
63 þ (4)
70
a
61 þ (2)
a
Dichloro product.

2822
B. T. S. Thirumamagal, S. Narayanasamy, and R. Venkatesan
Scheme 1. Regiospecific chlorination of xylenes. Reagents and conditions: i)
ꢀ
N-chlorosuccinimide, K-10 montmorrillonite clay, 1,2-dichloroethane, 80 C,
ꢀ
1
6–18 h; ii) N-chlorosuccinimide, 1,2-dichloroethane, 80 C, 12–14 h; iii) HNO
ꢀ
3
(
40%), 80 C, 12 h.
successfully used in chlorination reactions. Chlorination in the presence
of clay resulted in aromatic substitution through the conventional
electrophilic mechanism, and in its absence, the side-chain chlorinated
[
11]
product resulted through the conventional radical mechanism.
The
reaction was unsuccessful with p-nitro acetanilide. In the absence of
solvent, the reaction also was unsuccessful in all the cases. Use of
bentonite clay gave similar results. The monochloro compound was
further confirmed by regioselective oxidation of p-choroxylene to give
the corresponding chlorotoluic acid in 30% yield (Scheme 1).
EXPERIMENTAL
General
All chemicals were used without further purification. K-10 montmorrillo-
nite clay was purchased from Aldrich. Analyses of the products were per-
formed on a HP-5890-II gas chromatograph with flame ionization
detector (FID). Merck silica gel (ACME, l00–200 mesh) was used for
1
13
column chromatography. H and CNMR spectra were recorded on
Jeol-GSX 400 (400-MHz) and Jeol-FX 90Q (90-MHz) instruments with
TMS as internal standard [chemical shift in (d) ppm]. Mass spectra were
recorded on Finninngan MAT 8230 instrument.
Typical Procedure for Chlorination of Aromatic Compound using NCS and
K-10 Montmorrillonite Clay in 1,2-Dichloroethane
To a solution of aromatic compound (100 mmol) in a dry 1,2-
dichloroethane (50 mL), NCS (100 mmol) and K-10 montmorrillonite

Regiospecific Chlorination of Xylenes
2823
ꢀ
clay (4 g) were added and heated at 80 C for 16–18 h. The crystallized
succinimide along with the clay was filtered off and separated by washing
with dichloromethane. The solvent was removed by distillation from the
filtrate. The liquid chlorinated product was purified by passing through a
silica-gel column using hexanes=ethyl acetate (98:2) as the eluent. MS:
m=z (%) 140.51 (100.0), 142.34 (32.0).
Data
1
4
7
1
-Chloro-1,2-xylene (4): liquid (9.1 g, 65% yield). H NMR (CDCl ): d
3
1
.1–7.3 (m, 3H, Ar), 2.37 (s, 3H, Me), 2.35 (s, 3H, Me); C NMR 138,
3
37.2, 130.5, 130.3, 128.6, 125.9, 14.7, 13.9.
1
4
.1–7.4 (m, 3H, Ar), 2.3 (s, 3H, Me), 2.27 (s, 3H, Me); C NMR
-Chloro-1,3-xylene (5): liquid (8.4 g, 60%). H NMR (CDCl ): d
3
1
3
7
1
36.1, 135.3, 134.0, 130.6, 129.7, 127.3, 20.1, 11.0.
1
2
.8–6.9 (m, 3H, Ar), 2.35 (s, 3H, Me), 2.31 (s, 3H, Me); C NMR
-Chloro-1,4-xylene (6): liquid (8.6 g, 62%). H NMR (CDCl ): d
3
1
3
6
1
37.7, 135.5, 131.0, 130.8, 128.3, 126.9, 20.7, 11.9.
1
4-Chloroanisole: liquid (10 g, 70%). H NMR (CDCl ): d 7.4 (s, 2H,
Ar), 6.7 (s, 2H, Ar), 3.8 (s, 3H, Me); C NMR 162.1, 132.0, 125.6, 117.7,
3
1
3
5
5.7. MS: m=z (%) 142.00 (100.0).
General Procedure for Side-Chain Chlorination of Aromatic Compounds in
the Absence of Clay
NCS (100 mmol) was added to a solution of aromatic compound
ꢀ
(
1
100 mmol) in dry 1,2-dichloromethane (50 mL) and heated at 80 C for
2–14 h. The crystallized succinimide was filtered off. The solvent was
removed from the filtrate by distillation. The liquid chlorinated product
was purified by passing through a silica-gel column using hexane–ethyl-
acetate (9:1) as the eluting solvent. MS: m=z (%) 140.50 (100.0), 142.37
(
33.0).
Data
-Chloromethyltoluene (7): liquid (9.3 g, 67%). H NMR (CDCl ): d 2.35
1
2
(
3
1
3
s, 3H, Me), 4.3 (s, 2H, CH Cl), 7.1–7.3 (m, 4H, Ar); C NMR 138.7,
2
1
38.0, 130.1, 128.9, 128.6, 124.9, 43.0, 15.1.
-Chloromethyltoluene (8): liquid (9.8 g, 70%). H NMR (CDCl ): d
1
3
.31 (s, 3H, Me), 4.6 (s, 2H, CH Cl), 7.07–7.3 (m, 4H, Ar); C NMR
3
1
3
2
2
1
38.0, 137.6, 130.5, 130.3, 129.1, 124.7, 52.0, 21.5.

2824
B. T. S. Thirumamagal, S. Narayanasamy, and R. Venkatesan
1
-Chloromethyltoluene (9): liquid (8.8 g, 63% yield). H NMR
4
(
CDCl ): d 2.10 (s, 3H, Me), 4.4 (s, 2H, CH Cl), 6.8–7.1 (m, 4H, Ar);
C NMR: 137.2, 134.5, 130.3, 129.1, 51.0, 20.8.
3
2
1
3
2
-Chloro-4-methylbenzoic acid (10)
To 2-chloro-1,4-xylene (50 mmol), 40% nitric acid (110 mL) was added
ꢀ
and heated at 80 C for 12 h. The reaction mixture was poured into
crushed ice. The acid (2-chloro-4-methylbenzoic acid) was filtered and
ꢀ
1
dried over calcium chloride (2.55 g, 30%), mp 150–152 C; H NMR
CDCl ): d 2.35 (s, 3H, Me), 7.1–7.8 (m, 3H, Ar), 10.8 (s, 1H, COOH);
C NMR 170.4, 147.2, 135.5, 131.6, 130.1, 128.6, 126.4, 24.7; MS: m=z
(
3
1
3
(%): 170.45 (100.0%), 172.21 (32.0%).
ACKNOWLEDGMENT
B. T. S. T. acknowledges University Grants Commission-Special Assist-
ance Programme (UGC-SAP) for instrument grants to the department
and University of Madras for a URF.
REFERENCES
1
. Nazarenko, E. S.; Dolmat, V. M.; Pozdnyakovich, Y. V.; Shein, S. M. Prep-
aration of monochlorophthalic acids by the liquid-phase catalytic oxidation
of chloro-o-xylenes. Ukrainskii Khimicheskii Zhurnal 1984, 50, 644–647.
. Mitsubishi Gas Chemical Co. Aromatic aldehydes. Jpn. Kokai Tokkyo Koho
2
3
4
1982, 8.
. Hung So, Y. Substituent effects on the pyrolysis of a-chloro-o-xylenes.
J. Org. Chem. 1987, 52, 1615–1617.
. Ponce, P.; Catalani, L. H. Photolysis of a-xylyl chlorides: An efficient
deep-UV photoinitiating system for radical and cationic polymerization.
Photochem. Photobiol. Sci. 2004, 3, 700–705.
5
6
7
. Nwaukwa, S. O.; Keehn, P. M. Ring chlorination of benzenoid compounds
2
using calcium hypochlorite [Ca(OCl) ]. Synth. Commun. 1989, 19, 799–804.
. Varma, R. S. Clay and clay supported reagents in organic synthesis. Tetra-
hedron 2002, 58, 1235–1255.
. (a) Chakrabarty, M.; Ghosha, N.; Harigayab, Y. A clay-mediated, regioselec-
tive synthesis of 2-(aryl=alkyl)aminothiazolo[4,5-c]carbazoles. Tetrahedron
Lett. 2004, 45, 4955–4957; (b) Chakrabarty, M.; Kundu, T.; Harigaya, Y.
Clay-mediated reaction of indoles with cyclohexane-1,3-diones: An expedient
route to indolylcyclohexenones. J. Chem. Res. 2004, 11, 778–780.
. Chakrabarty, M.; Sarkar, S. A clay-mediated eco-friendly thiocyanation of
indoles and carbazoles. Tetrahedron Lett. 2003, 44, 8131–8133.
8

Regiospecific Chlorination of Xylenes
2825
9
. Vaccari, A. Clays and catalysis: A promising future. Appl. Clay Sci. 1999, 14,
61–198.
1
1
1
0. Susanta, S.; Frederick, F. B.; Bimal, K. B. Montmorillonite KSF–mediated
facile synthesis of pyrroles. Heterocycles 2001, 55, 1019–1022.
1. Venkatachalapathy, C.; Pitchumani, K. Selectivity in bromination of alkyl-
benzenes in the presence of montmorillonite clay. Tetrahedron 1997, 53,
2581–2584.