Promotion of 1,3-Dithiolanes using a Bentonitic Clay as Catalyst

Article abstract of DOI:10.1002/hc.10215

The reactions between 1,2-ethandithiol with several carbonylic compounds to form the corresponding 1,3-dithiolanes were performed using a natural clay as promotor. The target molecules are used as reagents to obtain fine chemicals, herbicides, fungicides,

Full text of DOI:10.1002/hc.10215

Heteroatom Chemistry
Volume 15, Number 1, 2004
P
romotion of 1,3-Dithiolanes Using
a Bentonitic Clay as Catalyst
1
1
1
1
J. M. Aceves, G. A. Arroyo, Y. M. Vargas, R. Miranda,
A. Cabrera, and F. Delgado
2
3
1
Departamento de Ciencias Qu ı´ micas, Facultad de Estudios Superiores Cuautitl a´ n,
Universidad Nacional Aut o´ noma de M e´ xico, Avenida 1 de Mayo s/n, Cuautitl a´ n Izcalli,
Estado de M e´ xico, CP 54740
2
Instituto de Qu ı´ mica, Universidad Nacional Aut o´ noma de M e´ xico, Circuito Exterior,
Ciudad Universitaria, Coyoac a´ n, M e´ xico, D.F., CP 04510
3
Departamento de Qu ı´ mica Org a´ nica, Escuela Nacional de Ciencias Biol o´ gicas,
Instituto Polit e´ cnico Nacional, Prolongaci o´ n Carpio y Plan de Ayala, Casco de Santo Tom a´ s,
M e´ xico, D.F., CP 11340
Received 10 July 2003
pharmaceuticals, flavors, and fine chemicals [1,2]. Of
ABSTRACT: The reactions between 1,2-ethandithiol
particular interest is their employment to protect the
with several carbonylic compounds to form the cor-
carbonyl group and as intermediates in the synthe-
responding 1,3-dithiolanes were performed using a
sis of organic sulfur compounds [2]. There are many
natural clay as promotor. The target molecules are
general methods for the preparation of dithiolanes
used as reagents to obtain fine chemicals, herbi-
involving different reagents and catalysts, such as
cides, fungicides, and pharmaceutical compounds
H·Y zeolite, FeCl
3
, nafion, and more commonly BF ;
3
among others applications. A kinetic study of cam-
phorquinone and 1,2-ethandithiol showed a first-order
dependence with 1,2-ethandithiol as well as with cam-
phorquinone. The substrate transformation in percent
was found to be dependent with the reaction time,
the amount of catalyst, and the reagents concentra-
tion. ꢀC 2003 Wiley Periodicals, Inc. Heteroatom Chem
however, these catalysts have restrictions due to the
pollution and their high cost [3]. In view of these con-
siderations, the use of natural and modified clays as
catalytic promoters provides important and attrac-
tive alternatives [4]. As part of our research work
[5–6], TAFF, a commercial bentonitic clay [3], has
long being employed by us as a catalyst and as a
support of inorganic molecules in order to promote
organic reactions, such as the promotion of oxathi-
olanes, ketonic dithiolanes, and trioxanes. Thus, the
aim of this paper is to describe the preparation of sev-
eral 1,3-dithiolanes with various carbonyl substrates
in the presence of 1,2-ethandithiol, using the acidic
clay as catalyst, in addition to a kinetic study for the
preparation of the ꢀ-dithiolane of camphorquinone.
1
5:71–76, 2004; Published online in Wiley InterScience
(
www.interscience.wiley.com). DOI 10.1002/hc.10215
INTRODUCTION
The 1,3-dithiolanes are useful starting materials for
the preparation of herbicides, fungicides, polymers,
Correspondence to: J. M. Aceves; e-mail: aceves h@yahoo.
com.mx.
RESULTS AND DISCUSSION
Contract grant sponsor: DGAPA-UNAM PAPIIT IN.
Contract grant number: 208202.
The results of several experiments performed with
ethandithiol and a set of aldehydes and ketones,
ꢀ
c 2003 Wiley Periodicals, Inc.
7
1

7
2 Aceves et al.
using TAFF as catalyst and anhydrous toluene as
solvent, are summarized in Table 1. The target
molecules are obtained in good yields and at short
reaction times. In general, the compounds obtained
were pure and the work-up procedure was simple,
since only one spot was detected on thin-layer chro-
matography (TLC). The employment of the ben-
tonitic clay thus is a good alternative for the pro-
motion of 1,3-dithiolanes.
In order to probe the catalytic effect of the
clay, the coupling reaction of ethandithiol with
camphorquinone was inhibited by adding different
amounts of pyridine. The results suggested the co-
3
+
ordination of the pyridine with the Al centers in
TABLE 1 Reaction Time and Dithiolane Formation Yields from Different Carbonyl Substrates, Using Ethandithiol as Reagent
and TAFF as the Catalyst
a
Substrate
Dithiolane
Reaction Time (h)
Yield (%)
O
3
99
S
S
O
O
O
O
S
S
S
4
5
75
60
O
O
S
O
O
O
O
O
O
O
O
O
O
5
3
80
90
S
O
S
O
O
S
S
S
S
3
2
2
90
90
95
O
S
S
(
(
CH2)5 Me
CH2)5 Me
H
O
S
O
O
S
O
S
H
S
2
2
2
90
90
60
O
H
S
S
O 2N
O2N
O
S
H
S
OH
OH
O
S
Cl
Cl
2
2
90
60
H
S
S
O
HO
HO
H
S
O
O
O
3
60
S
S
aThe yields are of pure isolated products.

Promotion of 1,3-Dithiolanes Using a Bentonitic Clay as Catalyst 73
1
00
9
0
0
0
0
0
0
0
0
0
8
7
6
5
4
3
2
1
0
0
1
2
3
4
5
mmol pyridine/0.5 g of TAFF
FIGURE 1 Pyridine as inhibitor of the generation of the ꢀ-dithiolane of the camphorquinone. Each point is the average of
three experiments.
the montmorillonitic frame, reducing the Lewis acid
sites of the clay, as shown in Fig. 1.
In addition, several reactions carried out with-
out catalyst yielded negative results. When compar-
in order to optimize the reaction time of the process,
an experiment was carried out by determining the
formation of 3-dithiolane as time function; in this
regard, Fig. 3 shows the plot of dithiolane yield vs.
time. A 100% transformation of the substrate was
obtained after an optimum reaction time of 5 h.
The effect of the ethandithiol concentration is
presented in Fig. 4, which shows the plot of the
dithiolane yield vs. time by changing the amount of
ethandithiol and maintaining the quinone concen-
tration constant in order to determine the initial re-
ing TAFF’s catalytic activity with that of Al
and SnCl , it was demonstrated that only the clay
produces the dithiolanes in quantitative amounts.
2
O
3
, SiO ,
2
2
In this sense, Fig. 2 shows the effect of the
catalyst concentration on the formation of 1,3-
dithiolane, following the optimized reaction condi-
tions when a 100% product formation was obtained.
Reaction of ethandithiol (40 mmol) with 550 mg
TAFF and 20 mmol camphorquinone for 5 h yields
products detected by using a GC-MS. Additionally,
action rate (V
0
). On plotting log V vs. log dithiolane
0
concentration, a straight line with slope 1.05 was
obtained.
1
00
9
8
7
0
0
0
6
5
4
3
0
0
0
0
2
1
0
0
0
0
100
200
300
400
500
700
800
1000
TAFF (mg)
◦
FIGURE 2 Effect of catalyst concentration on the formation of 1,3-dithiolane of camphorquinone; temperature, 105 C;
camphorquinone, 20 mmol; ethandithiol, 40 mmol; reaction time, 5 h. Each point is the average value of three experiments.

7
4 Aceves et al.
1
00
•
•
•
•
9
8
7
6
5
4
3
2
1
0
•
•
•
0
0
0
0
0
0
0
0
•
•
•
0
0
3
0
60
90
120
150
180
210
240
270
300
Time (min)
◦
FIGURE 3 Formation of the 3-dithiolane of camphorquinone as function of time; temperature, 105 C; ethandithiol, 40 mmol;
camphorquinone, 20 mmol; TAFF, 550 mg. Each point is the average value of three experiments.
A similar method was applied to study the effect
of quinone concentration, obtaining an order of 1 for
this experiment (Fig. 5).
prepared by a previously reported procedure [5]. The
natural clay was obtained from Tonsil Mexicana S.A.
de C.V. and analyzed prior to use with a Siemens
D-5000 X-ray diffractometer using the Cu Kꢁ ra-
1
diation. The Lewis acid character was confirmed
with a Perkin-Elmer 1600 series FTIR spectrome-
ter, by using the IR pyridine coordination method
[7]. Purified products were characterized by spec-
EXPERIMENTAL
Toluene (Aldrich) was dried prior to use (Na/
benzophenone). The carbonyl substrates and the
ethandithiol employed were also purchased from
Aldrich and used as received. Camphorquinone was
1
troscopic means: H NMR spectra were recorded in
a Varian FT-200 spectrometer using CDCl as solvent
3
1
00
90
80
70
60
50
40
30
20
10
0
0
20
40
60
80
100
120
140
160
180
Time (min)
FIGURE 4 Dithiolane formation as function of the time, maintaining constant (20 mmol) the initial quantity of camphorquinone
and varying the initial quantities of ethandithiol: 10 ( ), 20 ( ), 40 ( ), and 50 ( ) mmol. Each point is the average value of three
experiments.

Promotion of 1,3-Dithiolanes Using a Bentonitic Clay as Catalyst 75
70
60
50
40
30
20
10
0
0
50
100
150
200
Time (min)
FIGURE 5 Dithiolane formation vs. reaction time, maintaining the initial quantity of ethandithiol constant (20 mmol) and initial
quantities of camphorquinone (in mmol): 10 (ꢀ), 20 ( ), 30 (•), and 40 ( ). Each point is the average value of three experiments.
and TMS as internal reference; EIMS (70 eV) spec-
tra were obtained using a HP5985 B and a JEOL
JMS AX505HA mass spectrometer. For the kinetic
experiments a Polyscience Corporation Tempera-
ture Controller Model 73 was employed. The cor-
responding percentage formation values were ac-
quired by a Varian gas chromatograph model Star
4.63, 6.95, and 9.26) were tested; the concentrations
of camphorquinone and ethandithiol were 2 and 4
mmol respectively, and 5 h was the reaction time
(Fig. 1).
Formation of Camphorquinone
β-Monodithiolane with Different Quantities
of Catalyst
3400 equipped with a flame ionization detector and
a 30 m × 0.53 mm column packed with polyethylen-
eglycol. Thin-layer chromatography analysis was
performed using Merck precoated plates (silica gel
Various quantities (0–1000 mg) of TAFF were as-
sayed. The reflux time was 5 h and the cam-
phorquinone and ethandithiol concentrations were
60 F254, 0.25 mm), for which the corresponding
2
0 mmol and 40 mmol, respectively (Fig. 2).
chromatographic column silica gel 60 Merck 70-230
was employed.
β-Monodithiolane of Camphorquinone
Formation as Time Function
Typical Reaction Example
Several samples from a typical reaction were initially
monitored, at 2.5, 5.0, 7.5, 15.0, and 30 min, and af-
ter that with 30 min intervals for 5 h using 540 mg
of TAFF. The camphorquinone and ethandithiol
concentrations were maintained at 20 mmol and
Camphorquinone (2.42 g, 10 mmol) and 1,2-
ethandithiol (1.2 g, 12.7 mmol) in 10 ml of anhydrous
toluene were refluxed for 5 h in presence of 250 mg
of activated bentonite. The reaction was monitored
by TLC (n-hexane/EtOAc 7:3), and the reaction mix-
ture was filtered over celite and the solution washed
4
0 mmol (Fig. 3).
with NaOH 5% (2 × 20 ml) and dried (Na
2
SO ).
4
Determination of Ethandithiol Partial
Reaction Order
The solvent was removed under vacuum and the
residue purified by chromatographic column yield-
ing 80% of pure ꢀ-dithiolane. In other experiments
these amounts were optimized.
The camphorquinone concentration was constant
(
20 mmol), a set of four experiments (10, 20, 30,
and 50 mmol) of ethandithiol, 540 mg clay during
h, in order to know the partial reaction order of
3
Inhibition of a Catalyst
ethandithiol was performed; since the initial rate
method was employed, samples for each reaction
time at 2.5, 5, 7.5, 15, 30, 60, 90, 150, and 180 min
were analyzed (Fig. 4).
A set of experiments using pyridine as inhibitor
were accomplished; thus different ratios of mmol
py/g TAFF (0.274, 0.549, 0.8241, 1.17, 1.175, 2.31,

7
6 Aceves et al.
Determination of the Camphorquinone Partial
Reaction Order
M.; Matsuda, H. Eur Patent Appl. EP 308 909, 1987;
d) Soc, A.; Kanna, H.; Hasegawa, N.; Mihagi, Y. Eur
Patent Appl EP 218 736, 1985.
(
In order to determine the camphorquinone partial
reaction order, the initial rates method was also used.
The ethandithiol concentration was maintained con-
stant (20 mmol) while the camphorquinone concen-
tration was assayed from 20 to 60 mmol; the quantity
of TAFF in each case was 540 mg and the samples
were analyzed at 2.5, 5, 7.5, 15, 30, 60, 90, 150, and
[2] Labiad, B.; Villemin, D. Synth Commun 1989, 19, 31.
[
3] The Tonsil Actisil FF (TAFF) commercial bentonitic
clay was purchased from Tonsil Mexicana S. A.
de C. V. Insurgentes Sur 1971, CP. 01020 Ciudad
de M e´ xico at US $1.35/kg vs. [ZnCl2 99.99%, US
$2640.00/kg, AlCl3 99.99%, US $137.20/kg, TiCl2
99.98% US $21,900.00/kg, BF3·Et2O US $62.20/l,
FeCl US $3958.00/kg, Clay K 10 US $22.30/kg, Clay
3
K SF US $22.30, taken from Aldrich 1995–1997, Cat-
alogue]; analyzed with a Phillips spectrometer us-
ing Cu Kꢁ radiation; the X-ray fluorescence analy-
ses proved to have the following composition (in %):
180 min (Fig. 5).
CONCLUSIONS
MgO, 2.11; Al O , 8.55; SiO , 75.34; CaO, 4.72; K O,
2
3
2
2
2
.93; TiO , 1.03; MnO , 0.03; Fe O , 6.42; CuO, 0.01;
2 2 2 3
The reaction order for the camphorquinone and the
ethandithiol was 1 for both of them and the clay em-
ployed proved to be a convenient catalyst to promote
the preparation of 1,3-dithiolanes. Besides, there is
a maximum pyridine concentration for total inhibi-
tion of the clay catalytic effect. Thus, it had been
proven that this method is an easy one-pot work-up
procedure and an effective alternative for the dithi-
olane preparation reaction under mild conditions.
ZnO, 0.02; SeO , 0.002; Rb O, 0.032; SrO, 0.129. The
specific surface obtained was 190 m /g (BET method,
N ); in addition, quartz and cristobalite are also im-
portant components.
2
2
2
2
[4] Lazlo, P. J Phys Org Chem 1998, 11, 356.
5] (a) Delgado, F.; Tamariz, J.; Zepeda, G.; Landa, M.;
[
Miranda, R.; Garc ´ı a, J. Synth Commun 1995, 25, 753;
(b) Salm o´ n, M.; Zavala, N.; Cabrera, A.; C a´ rdenas,
J.; Gavi n˜ o, R.; Miranda, R.; Mart ´ı nez, M. J Mol Cat
1995, 104, L127; (c) Cabrera, A.; Pe o´ n, J.; Velasco,
L.; Miranda, R.; Salm o´ n, A. J Mol Cat 1995, 104, L5;
(
d) Penieres, G.; Miranda, R.; Garc ´ı a, J. G.; Aceves,
J. M.; Delgado, J. Heterocycl Commun 1996, 2, 401;
e) Miranda, R.; Aceves, J. M.; Gutierrez, C.; Mart ´ı nez,
ACKNOWLEDGMENT
(
Mr. Draucin Jim e´ nez, A. Becerril, and P. Garc ´ı a
R.; Delgado, F.; Cabrera, A.; Salm o´ n, M. Heterocyclic
Commun 1997, 3, 147, and cites therein.
6] Miranda, R.; Arroyo, G. A.; Penieres, G.; Salm o´ n,
M.; Cabrara, A.; Aluarez, C.; Delgado, F. Heterocyclic
Preparative Chemistry 1980–2003, Research Trends,
in press (2003).
Estrada are acknowledged for technical assistance.
[
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