Aminolysis of aryl dithio-2-thiophenates and dithio-2-furoates in acetonitrile

Article abstract of DOI:10.1002/(SICI)1097-4601(1998)30:11<849::AID-KIN7>3.0.CO;2-V

The aminolyses of the title substrates with anilines and benzylamines are investigated in acetonitrile. A clean second-order kinetics is obtained with a first-order rate law in the amine concentration, which is uncomplicated by the fast proton transfer st

Full text of DOI:10.1002/(SICI)1097-4601(1998)30:11<849::AID-KIN7>3.0.CO;2-V

Aminolysis of Aryl
Dithio-2-Thiophenates and
Dithio-2-Furoates in
Acetonitrile
HYUCK KEUN OH,1 SO YOUNG WOO,1 CHUL HO SHIN,1 IKCHOON LEE2
1Department of Chemistry, Chonbuk National University, Chonju 560-756, Korea
2Department of Chemistry, Inha University, Inchon 402-751, Korea
Received 25 February 1998; accepted 19 May 1998
ABSTRACT: The aminolyses of the title substrates with anilines and benzylamines are inves-
tigated in acetonitrile. A clean second-order kinetics is obtained with a first-order rate law in
the amine concentration, which is uncomplicated by the fast proton transfer step. The large
magnitude of ␳Z (␳1g) as well as ␳X (␳nuc) together with relatively large positive ␳ values is
XZ
consistent with a stepwise mechanism in which thiophenolate ion expulsion from the inter-
mediate is rate limiting. For the reactions of aryl dithio-2-thiophenates with benzylamines the
magnitude of ␳ and ␳ values is relatively smaller suggesting that both the addition and
X
Z
expulsion of thiophenolate are partially rate determining. Relatively large secondary kinetic
isotope effects, kH/kD Ն 1.7, with deuterated nucleophiles, support involvement a concurrent
proton transfer to the departing thiophenolate ion in the transition state. ᭧ 1998 John Wiley &
Sons, Inc. Int J Chem Kinet 30: 849–857, 1998
INTRODUCTION
R
: C6H5
I
S
IV :
II : CH3
In the acyl transfer reactions, one of the factors that
favors the stepwise mechanism involving a tetrahedral
addition intermediate is the presence of a strong elec-
tron acceptor acyl group [1], R, in a–d. It has been
shown that a phenyl group, R ϭ C6H5 , exhibits a rel-
atively strong accepting power leading
O
III :
to the stepwise mechanism with rate-limiting break-
down of a zwitterionic tetrahedral intermediate, TϮ, in
the aminolysis with relatively basic amines, benzylam-
ines (pKa Ն 8.5), as well as with weakly basic amines,
anilines for both aryl benzoates [2], Ia, and S-aryl
thiolbenzoates [3], Ib, in acetonitrile. However, in the
aminolysis of dithio analogs, Id, and IId, a mechanis-
tic changeover from a stepwise mechanism with rate-
limiting leaving group departure for weakly basic
amines, anilines [4], to that of rate-limiting attack (or
concerted mechanism) for basic amines, benzylamines
[5,4(b)], was observed in acetonitrile solvent; thus, for
I (R ϭ C6H5 ) with aniline nucleophiles (XC6H5NH2 )
the magnitudes of ␤X (␤nuc) and ␤Z (␤1g , for Ar ϭ
O
O
R9C9OAr
R9C9SAr
a
b
S
S
R9C9OAr R9C9SAr
c
d
Correspondence to: I. Lee
Contract grant Sponsor: Ministry of Education of Korea
Contract grant number: Basic Science Research Grant (BSRI-
97-3431)
᭧ 1998 John Wiley & Sons, Inc.
CCC 0538-8066/98/110849-09

850
OH ET AL.
Table I Second-Order Rate Constants, kN (ϫ103 MϪ1 sϪ1), for the Reactions of Phenyl Dithio-2-Furoates with
Anilines in Acetonitrile at 40.0ЊC
a
a
X\Z
p-Me
H
p-Cl
p-Br
␳
␤
Z
Z
p-OMe
p-Me
H
12.3
6.53
2.70
0.829
0.341
18.5
10.2
4.35
1.41
0.621
32.7
19.3
8.94
2.99
1.41
35.3
21.2
10.1
3.43
1.62
1.05 Ϯ 0.02
1.17 Ϯ 0.03
1.31 Ϯ 0.04
1.40 Ϯ 0.05
1.54 Ϯ 0.04
Ϫ0.46 Ϯ 0.02
Ϫ0.52 Ϯ 0.02
Ϫ0.58 Ϯ 0.03
Ϫ0.62 Ϯ 0.03
Ϫ0.68 Ϯ 0.04
p-Cl
m-Cl
a
␳
␤
Ϫ2.36 Ϯ 0.07
0.84 Ϯ 0.02
Ϫ2.24 Ϯ 0.06
0.80 Ϯ 0.02
Ϫ2.09 Ϯ 0.05
0.74 Ϯ 0.01
Ϫ2.05 Ϯ 0.05
0.73 Ϯ 0.01
X
a
X
a Correlation Coeff.: r Ն 0.997. Errors shown are standard deviations.
C6H4Z in I) were large, 1.03 and Ϫ0.76, respectively,
at 55.0ЊC in acetonitrile [4a] whereas, they were much
smaller with ␤X ϭ 0.24 and ␤Z ϭ Ϫ0.24 with ben-
zylamines at 30.0ЊC in acetonitrile [5]. This mecha-
nistic changeover was supported by a change of nor-
mal (kH/kD Ͼ 1.0) to inverse (kH/kD Ͻ 1.0) secondary
kinetic isotope effect (SKIE) involving deuterated
amine nucleophiles [6].
A similar mechanistic change was also observed for
aryl dithioacetates, R ϭ CH3 in IId [4(b)].
In this work, we examine the influence of the elec-
tron donating ability of the acyl group, R, on the mech-
anism of the aminolysis of the dithio analogs using
O
mechanistic change of the kind encountered in the
aminolysis of benzoates (R ϭ C6H5 ) as we vary
amines from weakly basic, anilines, to basic, benzyl-
amines, eq. (1), where R ϭ 2-furan or 2-thiophene,
RЈ ϭ XC6H4 , or XC6H4CH2 with X ϭ p-OMe,
S
MeCN
R9C9SC6H4Z ؉ 2R؅NH2
S
R9C9NHR؅ ؉ NH3R؅ ؉ ؊SC6H4Z
(1)
p-Me, H, p-Cl, or m-Cl and Z ϭ p-CH3 , H, p-Cl, or
p-Br. Acetonitrile was used as a reaction medium in
order to avoid complexities arising from the fast pro-
ton transfer step in aqueous solution [3–5,8]. In this
work, we adopt a convention of labeling substituents
in the nucleophile (anilines), substrate, and departing
group as X, Y, and Z, respectively.
2-furan
(IIId), and 2-thiophene
,
R ϭ
(
)
S
(IVd), groups. Our high level ab ini-
R ϭ
,
(
)
tio MO theoretical studies have shown that the relative
delocalizability of lone pair ␲ electrons is in the order
O
S
RESULTS AND DISCUSSION
III
Ͼ IV
Ͼ I
(
)
(
) (
)
Under the reaction conditions (see Tables I–IV) all
reactions obeyed the simple kinetic law given by eqs.
[7]. Especially, we are interested to see if there is any
Table II Second-Order Rate Constants, kN (ϫ102 MϪ1 sϪ1), for the Reactions of Phenyl Dithio-2-Furoates with
Benzylamines in Acetonitrile at 15.0ЊC
a
a
X\Z
p-Me
H
p-Cl
p-Br
␳
␤
Z
Z
p-OMe
p-Me
H
4.70
3.14
1.67
8.63
5.98
3.40
19.6
15.3
9.19
22.5
17.4
10.7
1.55 Ϯ 0.04
1.71 Ϯ 0.03
1.85 Ϯ 0.04
1.90 Ϯ 0.05
Ϫ0.68 Ϯ 0.04
Ϫ0.75 Ϯ 0.03
Ϫ0.81 Ϯ 0.04
Ϫ0.84 Ϯ 0.04
p-Cl
0.831
1.71
4.79
Ϫ1.21 Ϯ 0.02
1.24 Ϯ 0.03
5.64
Ϫ1.18 Ϯ 0.01
1.21 Ϯ 0.02
a
␳
␤
Ϫ1.47 Ϯ 0.08
1.50 Ϯ 0.09
Ϫ1.37 Ϯ 0.05
1.40 Ϯ 0.06
X
a
X
a Correlation Coeff.: r Ն 0.997. Errors shown are standard deviations.

ARYL DITHIO-2-THIOPHENATES AND DITHIO-2-FUROATES
851
Table III Second-Order Rate Constants, kN (ϫ104 MϪ1 sϪ1), for the Reactions of Phenyl Dithio-2-Thiophenates with
Anilines in Acetonitrile at 40.0ЊC
a
a
X\Z
p-Me
H
p-Cl
p-Br
␳
␤
Z
Z
p-OMe
p-Me
H
8.02
4.45
1.70
0.412
0.184
15.9
9.15
3.76
0.955
0.428
42.2
25.6
10.7
3.03
1.43
44.5
26.5
11.0
3.27
1.56
1.74 Ϯ 0.02
1.82 Ϯ 0.03
1.90 Ϯ 0.05
2.10 Ϯ 0.02
2.17 Ϯ 0.01
Ϫ0.77 Ϯ 0.03
Ϫ0.80 Ϯ 0.04
Ϫ0.84 Ϯ 0.05
Ϫ0.92 Ϯ 0.05
Ϫ0.95 Ϯ 0.04
p-Cl
m-Cl
a
␳
␤
Ϫ2.55 Ϯ 0.02
0.91 Ϯ 0.02
Ϫ2.44 Ϯ 0.04
0.87 Ϯ 0.02
Ϫ2.29 Ϯ 0.03
0.81 Ϯ 0.02
Ϫ2.26 Ϯ 0.02
0.80 Ϯ 0.02
X
a
X
a Correlation Coeff.: r Ն 0.996. Errors shown are standard deviations.
(2) and (3), where P is thiophenolate anion and N is
amine. Plots of kobs vs. [N] were linear, and
S
ka
R9C9SAr ؉ XN
S؊
k؊a
d[P]/dt ϭ kobs[Substrate]
kobs ϭ kN[N]
(2)
(3)
S
kb
R9C9SAr
R9C ؉ ArS؊
the kN values were obtained from the slopes of these
plots. The kN values determined are summarized in
Tables I–IV. The rates are faster with benzylamines
than with anilines, and, also, are faster with a stronger
nucleophile (X ϭ p-OMe) and a stronger nucleofuge
(Z ϭ p-Br). These trends are in accord with those for
typical nucleophilic substitution reactions. For these
series of reactions with benzylamines as well as ani-
lines, clean second-order kinetics, eqs. (2) and (3),
were obtained and, hence, there were no complications
arising from competition of the fast proton transfer
from TϮ, nor from general base catalysis by the amines
[8]. The mechanism of the reactions can, therefore, be
described completely by eq. (4), where Ar ϭ C6H4Z,
XN represents amines with substituent X, and R is 2-
furan or 2-thiophene. Thus kN in eq. (3) is a complex
quantity given by eq. (5).
؉NX
؉NX
T؎
(4)
(5)
ka
k؊a
kN ؍
ؒ kb ؍ Kkb
The Hammett ␳ and Brønsted ␤ values are summa-
rized in Tables I–IV. Since the reactions were con-
ducted in acetonitrile, the magnitude of ␤X (␤nuc) and
␤Z (␤1g ) determined using the pKa values in water may
not be reliable. However, as we have pointed out pre-
viously the ␤X values can provide reasonable guides
[4b], since although the absolute values of pKa in
MeCN differ from those in water a constant
⌬pKa ( ϭ pKCH CN Ϫ pKa H O Х 7.5) was experi-
3
3
2 2
mentally found [9]. The values of ␤z may be signifi-
cantly smaller than the values reported on the basis of
Table IV Second-Order Rate Constants, kN (ϫ102 MϪ1 sϪ1), for the Reactions of Phenyl Dithio-2-Thiophenates with
Benzylamines in Acetonitrile at 15.0ЊC
a
a
X\Z
p-Me
H
p-Cl
p-Br
␳
␤
Z
Z
p-OMe
p-Me
H
3.24
2.37
1.61
4.84
3.72
2.56
9.00
7.33
5.28
9.46
7.73
5.57
1.09 Ϯ 0.02
1.20 Ϯ 0.01
1.26 Ϯ 0.02
1.41 Ϯ 0.02
Ϫ0.48 Ϯ 0.01
Ϫ0.53 Ϯ 0.01
Ϫ0.56 Ϯ 0.02
Ϫ0.62 Ϯ 0.02
p-Cl
0.885
1.48
3.31
3.52
a
␳
␤
Ϫ1.09 Ϯ 0.04
1.11 Ϯ 0.03
Ϫ1.00 Ϯ 0.02
1.02 Ϯ 0.02
Ϫ0.85 Ϯ 0.01
0.87 Ϯ 0.01
Ϫ0.84 Ϯ 0.01
0.86 Ϯ 0.01
X
a
X
a Correlation Coeff.: r Ն 0.999. Errors shown are standard deviations.

852
OH ET AL.
Table V Comparison of ␳X, ␳Z, and ␳XZ Values for the Aminolysis of Various Aryl Thiol and Dithio Compounds in
Acetonitrile
O
S
O
S
S
S
O
O
S
C6H5CSC6H4Zd CH3CSC6H5Ze
COC6H5Zg
CSC6H5Zh
CSC6H5Zh
C6H5CSC6H5Zf
(Id)
(Ib)
(IId)
(IIIa)
(IIId)
(IVd)
␳
␳
␳
ANa
BA
AN
BA
AN
BA
Ϫ2.86–Ϫ3.11 Ϫ2.23–Ϫ2.96
Ϫ1.41–Ϫ2.06 Ϫ0.46–Ϫ0.63 Ϫ0.51–Ϫ0.73
Ϫ2.05–Ϫ2.36
Ϫ1.18–Ϫ1.47
1.05–1.54
Ϫ2.26–Ϫ2.55
Ϫ0.84–Ϫ1.09
1.74–2.17
X
Ϫ1.05–Ϫ1.92
1.66–1.95
1.09–1.28
0.58(50Њ)
1.46–2.33
0.43–0.69
0.60(55Њ)
Z
3.22–4.07
0.27(55Њ)c
Ex.
1.76–2.53
1.55–1.90
1.09–1.41
0.75 Ϯ 0.05(40Њ)i 0.68 Ϯ 0.07(40Њ)i
XZ
(0.998)j
(0.999)j
0.61(Ϫ20Њ)
0.50(30Њ)
1.19(55Њ)
0.65 Ϯ 0.14(15Њ) 0.59 Ϯ 0.06(15Њ)
(0.999)
Ex.
Ex.
(0.999)
Ex.
Ad-Ex.
RDSb AN
BA
Ex.
Ad.
Ex.
Ad.
Ex.
a Nucleophiles: AN ϭ aniline, BA ϭ benzylamine.
b RDS: rate-determining step: Either expulsion of leaving group (Ex.) or addition (Ad.) step.
c Temperature in ЊC.
d Ref. [3].
e Ref. [4(b)].
f Ref. [4(a), 5].
g H. J. Koh, J-W Lee, H. W. Lee, and I. Lee, New J. Chem., 21, 447, 1997.
h This work.
i Standard deviation.
j Correlation coefficient.
aqueous acidities. In Table V, we compared
zylamines. Comparison of the reactions of Ib and Id
with benzylamines (pKa Ն 9) shows that the change
of OϪ (Ib) to SϪ (Id) in TϮ favors arylthiolate ion
␳X (␳nuc), ␳Z (␳1g ), and ␳ (defined in eqs. (6)) [10]
XZ
values for the aminolysis of various aryl thiol and di-
thio derivatives in acetonitrile. It has been shown that
the magnitudes of ␳X and ␳Z are
expulsion suggesting the change of the kϪ /kb ratio
a
from Ͼ1.0 for Ib to ϽϽ 1.0 for Id. In contrast, the
aminolysis of Id with anilines (pKa Ͻ 5) leads to rate-
limiting addition, i. e., to the kϪ /kb ratio of Ͼ1.0.
log(kXZ/kHH) ϭ ␳ ␴ ϩ ␳ ␴ ϩ ␳ ␴ ␴
XZ X Z
(6a)
(6b)
a
X
X
Z
Z
These are in line with the results of Castro et. al., for
the aminolysis of IId with secondary alicyclic amines
in aqueous solution [8(a)].
Ѩ␳
Ѩ␳
X
Z
␳
ϭ
ϭ
XZ
Ѩ␴
Ѩ␴
Z
X
Relatively large magnitudes of ␳X and ␳Z values for
the aminolysis of IIId and IVd seem to support a step-
wise mechanism with rate-limiting expulsion of the
arylthiolate group. Consideration of temperature effect
on the relatively smaller magnitude of ␳X and ␳Z values
[12] for the reactions of IVd with benzylamines
(15ЊC), however, raises some doubt about this conclu-
sion. We note that the magnitudes of ␳X and ␳Z values
for IVd with benzylamines are smaller than those for
Ib and IIIa (which are believed to proceed by rate-
limiting leaving group departure) but are greater than
those for Id and IId (for which rate-limiting addition
is predicted). Thus, based on these comparisons, we
considerably larger for the rate-limiting leaving group
departure (kb ) than those for the corresponding values
of the rate-limiting addition (ka) [4(a),5,11], and the
cross-interaction constants␳XZ are relatively large pos-
itive value for the rate-determining expulsion of leav-
ing group from TϮ [4(a),5,11].
Reference to Table V reveals that for rate-limiting
leaving group departure in the aminolysis of Ib and
IIIa with benzylamines the magnitudes of ␳ and ␳
X
Z
values are indeed much greater than those correspond-
ing reactions of Id and IId with benzylamines for
which the rate-determining step is the addition of ben-

ARYL DITHIO-2-THIOPHENATES AND DITHIO-2-FUROATES
853
may conclude that both steps are partially rate deter-
mining in the reactions of IVd with benzylamines. It
is also notable that the magnitude of ␤X (0.86–1.11)
as well as ␤Z (Ϫ0.48–Ϫ0.62) for the reactions of IVd
with benzylamines in acetonitrile is also in between
those reported for the rate-limiting attack (␤X ϭ
0.2–0.7, ␤Z ϭ Ϫ0.3–Ϫ0.4) and rate-limiting expul-
sion of phenolate or thiophenolate ion (␤X ϭ
0.8–1.4, ␤Z ϭ Ϫ1.0–Ϫ1.5) in aqueous solution
[13]. Relatively large positive ␳XZ values for both IIId
and IVd are also in line with the proposed mechanism
[11].
Our ab initio computations at the MP2/6-31G*//
MP2/6-31G* level [14] have shown that the delocal-
izability of ring electrons (R) to the carbonyl group,
eq. (7), i.e., the stability of RCOH, is in the order
R ϭ III Ͼ IV Ͼ I [7].
ference of 40Њ [12] between the two rate constants
listed in Table VI. Since the mechanism of the two
reactions is rate-limiting expulsion of the thiopheno-
late ion, the approximate agreement with the rate in-
crease accompanied in the change of Ia : Ib : Ic is
satisfactory.
We note that a change of phenolate (OAr) to thio-
phenolate (SAr) results in a large rate increase, ca. 102
times, but a change of 9C("O)9 to 9C("S)9
only leads to a moderate rate increase, ca. 20 times.
This seems to contradict the results of Castro et.
al., who reported a decrease of rate with change of
9C("O)9 to 9C("S)9 [8], but discrepancy
may result from the different medium, i. e., aprotic vs.
aqueous solution.
In summary, the reactions of Id–IVd with anilines
proceed by a stepwise mechanism with rate-limiting
departure of the thiophenolate ion from the zwitteri-
onic tetrahedral intermediate, TϮ. In contrast, for the
corresponding reactions with the more basic amines,
benzylamine, the rate determining step changes from
the rate-limiting departure for a stronger inductive
electron acceptor acyl group, R ϭ III, to the rate-lim-
iting addition for a weaker acceptor acyl group, R ϭ
I. For R ϭ IV, which has an intermediate acceptor
ability [16], both steps are partially rate determining.
Finally, we have determined secondary kinetic iso-
tope effects involving deuterated aniline and benzy-
lamine nucleophiles. The kH/kD values are substantially
greater than 1.0 ranging from 1.7–1.9, Table VII.
Since the rates were first-order with respect to amine
concentration, eq. (3), general base catalysis by the
amine can be safely precluded. Thus, the relatively
large kH/kD values in Table VII seem to reflect a four-
center type transition state, V, where RЈ ϭ C6H4X or
C6H4CH2X.
O
O؊
؉
C
R"C
(7)
R
H
H
Accordingly, the natural bond orbital (NBO) positive
charge on the carbonyl carbon has been found to be
in the reverse order III (0.328) Ͻ IV (0.351) Ͻ
I (0.376). This analysis suggests that if the initial state
stability and the positive charge on the carbonyl car-
bon were important, i.e., if all the reactions proceeded
by rate-limiting attack, the aminolysis rate should be
the least with IIId and the fastest with Id. Examination
of the rate constants in Table VI, however, shows that
this expectation is not fulfilled. In fact, there is a
change in the rate determining step from addition of
amine to expulsion of thiophenolate as we vary R from
I through IV to III so that direct comparison of the
rate is meaningless. For example, the reactions of Ia–
Ic with benzylamines are reported to proceed by rate-
limiting departure of the leaving group. Roughly,
change of OAr (Ia) to SAr (Ib) (for Ar ϭ
C6H4 · p-NO2) brings a rate increase of ca. 102, while
change of 9C("O)9(Ia) to 9C("S)9(Ic) leads
to a rate increase of ca. 20. Thus, there is a ca. 103
times rate increase from Ia to Ic. However, no such
large rate increase is expected when the rate with ben-
zylamine of Ia is compared with that of Id; although
a direct comparison is difficult due to the different
reaction temperature, rough estimate gives a rate ratio
that is an order of magnitude lower, k(Id)/k(Ia) Ϸ 102.
This may be due to the mechanistic difference in the
reactions of the two, Ia (ex.) vs. Id (ad.). Similarly,
comparison of rates between the reactions of IIIa and
IIId leads to ca. 103 considering the temperature dif-
␦؊
S
␦؊
R9C SAr
HN␦؉ H␦
R؅
V
This type of four-centered transition state in which
there is concurrent thiophenolate ion departure and
proton transfer has also been proposed previously for
the aminolysis of phenyl dithioacetates (IId) [4(b)],
ethyl aryl carbonates [17] (EtO9C("O)9OAr) and
O-ethyl S-aryl dithiocarbonates [18] (EtO9C("S)
9SAr) in acetonitrile.

854
OH ET AL.
␴

ARYL DITHIO-2-THIOPHENATES AND DITHIO-2-FUROATES
855
Table VII Secondary Kinetic Isotope Effects for the Reactions of Phenyl Dithio-2-Furoates (IIId) with Deuterated
Anilines at 40.0ЊC and Phenyl Dithio-2-thiophenates (IVd) with Deuterated Benzylamines in Acetonitrile at 15.0ЊC
kD (dm3 mol
s
)
kH/kD
Ϫ1
Ϫ1
Ϫ1
Ϫ1
Nucleophile
X
Z
kH (dm3 mol
s
)
Ϫ3
Ϫ3
Ϫ3
Ϫ3
Ϫ3
Ϫ3
Ϫ3
Ϫ3
Ϫ3
Ϫ3
Ϫ3
Ϫ3
Ϫ3
Ϫ3
Ϫ3
Ϫ3
p-OMe
p-Cl
p-OMe
p-Cl
p-OMe
p-Cl
p-OMe
p-Cl
p-Me
p-Me
p-Br
p-Br
p-Me
p-Me
p-Br
p-Br
(12.3 Ϯ 0.13a) ϫ 10
(8.29 Ϯ 0.02) ϫ 10
(35.3 Ϯ 0.21) ϫ 10
(3.43 Ϯ 0.05) ϫ 10
(32.4 Ϯ 0.24a) ϫ 10
(8.85 Ϯ 0.16) ϫ 10
(94.6 Ϯ 0.45) ϫ 10
(35.2 Ϯ 0.22) ϫ 10
(7.02 Ϯ 0.12) ϫ 10
(4.53 Ϯ 0.02) ϫ 10
(19.9 Ϯ 0.23) ϫ 10
(1.86 Ϯ 0.05) ϫ 10
(18.8 Ϯ 0.25) ϫ 10
(4.97 Ϯ 0.16) ϫ 10
(52.3 Ϯ 0.47) ϫ 10
(18.6 Ϯ 0.21) ϫ 10
1.75 Ϯ 0.04a
1.83 Ϯ 0.01
1.78 Ϯ 0.02
1.84 Ϯ 0.06
1.72 Ϯ 0.03a
1.78 Ϯ 0.07
1.81 Ϯ 0.02
1.89 Ϯ 0.02
AN
BA
a Standard deviation.
EXPERIMENTAL
Materials
aromatic); ␦H (CDCl3 ), 7.89 (1H, dd, J ϭ 3.66,
1.47Hz, thiophene), 7.67 (1H, dd, J ϭ 4.39, 1.46Hz,
thiophene), 7.45 (2H, dd, 8.80, 2.20Hz, phenyl ring),
7.41 (2H, dd, J ϭ 8.80, 2.20Hz, phenyl ring), 7.16
(1H, dd, J ϭ 5.14, 4.40Hz, thiophene); ␦C 181.5 (C
"O), 141.0, 136.3, 136.1, 133.5, 131.8, 129.5, 128.1,
125.4.
S-p-bromophenyl thio-2-thiophenate: m. p. 90–
91ЊC, IR (KBr), 3110 (C9H, thiophene), 1658
(C"O), 1557, 1462 (C"C, aromatic), 810 (C9H,
Solvent, acetonitrile, was Merck G. R. grade, which
was used after three distillations. Anilines and ben-
zylamines were Tokyo Kasei G. R. grade.
a. Preparation of S-phenyl thio-2-thiophenecar-
boxylates (and thio-2-furancarboxylates). Thiophenol
derivatives (Aldrich G. R. grade) and 2-thiophenecar-
bonyl chloride (Aldrich G. R. grade) were dissolved
in dry ether kept at 0 ca. 5ЊC, and a small amount of
KOH was added successively. Adding ice to the re-
action mixture, ether layer was separated and extracted
twice. After drying with MgSO4 , solvent was removed
by distillation under reduced pressure. Melting points,
IR, proton, and carbon 13NMR analytical data are as
follows.
S-phenyl thio-2-thiophenate: m. p. 62–63ЊC, IR
(KBr), 3082 (C9H, thiophene), 1658 (C"O), 1553,
1465 (C"C, aromatic), 803 (C9H, aromatic); ␦H
(CDCl3 ), 7.96 (1H, dd, J ϭ 3.66, 1.47Hz, thiophene),
7.71 (1H, dd, J ϭ 5.13, 1.46Hz, thiophene), 7.48–
7.59 (5H, m, phenyl ring), 7.20 (1H, dd, J ϭ 5.13,
4.40Hz, thiophene); ␦C 181.0 (C"O), 141.4, 135.1,
133.2, 131.6, 129.3, 128.0, 127.0.
S-p-methylphenyl thio-2-thiophenate: m. p. 68–
69ЊC, IR (KBr), 3104 (C9H, thiophene), 1659
(C"O), 1552, 1478 (C"C, aromatic), 804 (C9H,
aromatic); ␦H (CDCl3 ), 7.89 (1H, dd, J ϭ 3.66Hz, thi-
ophene), 7.65 (1H, d, J ϭ 4.39Hz, thiophene), 7.39
(2H, d, phenyl ring), 7.25 (1H, d, J ϭ 8.06Hz, phenyl
ring), 7.15 (1H, t, J ϭ 4.40Hz), 2.43 (3H, s, methyl);
␦C 182.5 (C"O), 140.0, 135.0, 133.0, 131.5, 130.0,
127.9, 123.4 (methyl).
aromatic);
(CDCl ), 7.96 (1H, d,
thi-
␦
J ϭ 2.93Hz,
3
H
ophene), 7.68 (1H, dd,
1.47Hz, thiophene),
J ϭ 5.13,
7.57 (2H, dt, 8.80, 2.20Hz, phenyl ring), 7.38 (2H, dt,
2.20Hz, phenyl ring), 7.16 (1H, dd,
J ϭ 8.80,
4.40Hz, thiophene);
J ϭ
181.3 (C"O), 141.0,
␦
C
5.13,
136.4, 133.5, 132.5, 131.8, 128.1, 126.1, 124.4.
S-phenyl thio-2-furoate: m. p. 54–55ЊC, IR (KBr),
3033 (C9H, furan), 1662 (C"O), 1565, 1464
(C"C, aromatic), 751 (C9H, aromatic);
␦
H
(CDCl3 ), 7.61 (1H, s, furan), 7.43–7.51 (5H, m,
phenyl), 7.25 (1H, d, J ϭ 3.42Hz, furan), 6.59 (1H,
dd, J ϭ 3.42, 1.47Hz, furan); ␦C 178.4 (C"O), 150.1,
146.3, 134.9, 129.5, 129.1, 126.0, 116.1, 112.4.
S-p-methylphenyl thio-2-furoate: m. p. 77–78ЊC,
IR (KBr), 3124 (C9H, furan), 1661 (C"O), 1561,
1459 (C"C, aromatic), 768 (C9H, aromatic); ␦H
(CDCl3 ), 7.61 (1H, s, furan), 7.38 (2H, d, J ϭ
7.81Hz, phenyl ring), 7.25 (2H, d, 8.30Hz, phenyl
ring), 7.23 (1H, d, J ϭ 3.42Hz, furan), 6.56 (1H, dd,
J ϭ 3.42, 1.47Hz, furan), 2.39 (3H, s, methyl); ␦C
177.7 (C"O), 150.3, 141.1, 139.8, 134.9, 129.9,
122.4, 116.0, 112.2, 21.3 (methyl).
S-p-chlorophenyl thio-2-furoate: m. p. 102–103ЊC,
IR (KBr), 3122 (C9H, furan), 1665 (C"O), 1556,
1468 (C"C, aromatic), 767 (C9H, aromatic); ␦H
(CDCl3 ), 7.63 (1H, s, furan), 7.39–7.43 (4H, m,
phenyl ring), 7.27 (1H, d, J ϭ 3.42Hz, furan), 6.59
S-p-chlorophenyl thio-2-thiophenate: m. p. 85–
86ЊC, IR (KBr), 3122 (C9H, thiophene), 1658
(C"O), 1556, 1478 (C"C, aromatic), 809 (C9H,

856
OH ET AL.
(1H, dd, J ϭ 3.42, 1.47Hz, furan); ␦C 177.0 (C"O),
149.9, 146.5, 136.2, 136.0, 129.4, 124.5, 116.4, 112.4.
S-p-bromophenyl thio-2-furoate: m. p. 138–139ЊC,
IR (KBr), 3105 (C9H, furan), 1662 (C"O), 1561,
1470 (C"C, aromatic), 766 (C9H, aromatic); ␦H
(CDCl3 ), 7.63 (1H, s, furan), 7.57 (2H, d, J ϭ
8.30Hz, phenyl ring), 7.36 (2H, d, J ϭ 8.30Hz, phenyl
ring), 7.27 (1H, d, J ϭ 3.91Hz, furan), 6.59 (1H, dd,
J ϭ 3.42, 1.47Hz, furan); ␦C 177.7 (C"O), 149.9,
146.5, 136.4, 132.3, 125.2, 124.2, 116.4, 112.4.
b. Preparation of Phenyl Dithio-2-thiophenecar-
boxylates (and Phenyl Dithio-2-furan-carboxylates).
The S-phenyl thio-2-thiophenecarboxylates prepared
as above were dissolved in dry toluene and refluxed
with Lawesson’s reagent (Aldrich G. R. grade). After
extraction of the reaction mixture with dichlorometh-
ane, dried and removed solvent by distillation under
reduced pressure. Separation by column chromatog-
raphy gave the products, for which the following an-
alytical data were obtained.
phenyl dithio-2-thiophenate: m. p. 52–53ЊC, IR
(KBr), 3081 (C9H, thiophene), 1562, 1471 (C"C,
aromatic), 1054 (C"S), 783 (C9H, aromatic); ␦H
(CDCl3 ), 7.96 (1H, d, J ϭ 3.91Hz, thiophene), 7.67
(1H, d, J ϭ 4.88Hz, thiophene), 7.47–7.50 (5H, m,
phenyl ring), 7.15 (1H, t, J ϭ 4.40Hz, thiophene); ␦C
213.8 (C"S), 151.2, 135.8, 135.5, 133.1, 130.4,
129.5, 128.6, 127.0.
p-methylphenyl dithio-2-thiophenate: m. p. 58–
59ЊC, IR (KBr), 3075 (C9H, thiophene), 1594, 1496
(C"C, aromatic), 1050 (C"S), 777 (C9H, aro-
matic); ␦H (CDCl3 ), 7.95 (1H, d, J ϭ 3.90Hz, thio-
phene), 7.66 (1H, d, J ϭ 4.89Hz, thiophene), 7.36
(2H, d, J ϭ 7.82Hz, phenyl ring), 7.29 (2H, d, J ϭ
7.82Hz, phenyl ring), 7.15 (1H, t, J ϭ 4.40Hz, thio-
phene), 2.42 (3H, s, methyl); ␦C 214.4 (C"S), 21.58
(methyl), 151.2, 140.9, 135.6, 135.3, 130.8, 130.4,
128.6, 127.0.
p-chlorophenyl dithio-2-thiophenate: m. p. 67–
68ЊC, IR (KBr), 3075 (C9H, thiophene), 1572, 1473
(C"C, aromatic), 1049 (C"S), 774 (C9H, aro-
matic); ␦H (CDCl3 ), 7.94 (1H, dd, J ϭ 5.14, 1.47Hz,
thiophene), 7.68 (1H, dd, J ϭ 5.13, 1.47Hz, thio-
phene), 7.47 (2H, d, J ϭ 8.79Hz, phenyl ring), 7.40
(2H, d, J ϭ 8.79Hz, phenyl ring), 7.16 (1H, dd, J ϭ
5.13, 4.40Hz, thiophene); ␦C 212.9 (C"S), 151.0,
137.0, 136.9, 135.8, 129.8, 128.7, 128.6, 127.2.
p-bromophenyl dithio-2-thiophenate: m. p. 77–
78ЊC, IR (KBr), 3075 (C9H, thiophene), 1565, 1473
(C"C, aromatic), 1049 (C"S), 775 (C9H, aro-
matic); ␦H (CDCl3 ), 7.94 (1H, d, J ϭ 3.91Hz, thio-
phene), 7.68 (1H, d, J ϭ 4.89Hz, thiophene), 7.62
(2H, d, J ϭ 7.81Hz, phenyl ring), 7.32 (2H, d, J ϭ
7.81Hz, phenyl ring), 7.16 (1H, t, J ϭ 4.40Hz, thio-
phene); ␦C 212.7 (C"S), 151.0, 137.3, 135.8, 132.8,
129.4, 128.7, 127.3, 125.4.
phenyl dithio-2-furoate: m. p. 54–55ЊC, IR (KBr),
3105 (C9H, furan), 1550, 1448 (C"C, aromatic),
1055 (C"S), 600 (C9H, aromatic); ␦H (CDCl3 ),
7.69 (1H, s, furan), 7.46–7.51 (5H, m, phenyl), 7.44
(1H, d, J ϭ 3.91Hz, furan), 6.57 (1H, dd, J ϭ 3.42,
1.47Hz, furan); ␦C 206.6 (C"S), 157.3, 146.6, 135.8,
130.2, 129.3, 129.1, 116.0, 113.4.
p-methylphenyl dithio-2-furoate: m. p. 79–80ЊC,
IR (KBr), 3125 (C9H, furan), 1561, 1451 (C"C,
aromatic), 1058 (C"S), 804 (C9H, aromatic); ␦H
(CDCl3 ), 7.68 (1H, s, furan), 7.44 (2H, d, J ϭ
3.42Hz, furan), 7.36 (2H, d, J ϭ 8.30Hz, phenyl ring),
7.31 (2H, d, J ϭ 8.30Hz, phenyl ring), 6.54 (1H, dd,
J ϭ 3.42, 1.47Hz, furan), 2.43 (3H, s, methyl); ␦C
205.5 (C"S), 157.4, 146.6, 140.7, 135.6, 130.3,
125.6, 115.9, 113.5, 21.6 (methyl).
p-chlorophenyl dithio-2-furoate: m. p. 83–84ЊC,
IR (KBr), 3138 (C9H, furan), 1552, 1451 (C"C,
aromatic), 1056 (C"S), 803 (C9H, aromatic); ␦H
(CDCl3 ), 7.70 (1H, s, furan), 7.47 (2H, d, J ϭ
8.79Hz, phenyl ring), 7.44 (1H, s, furan), 7.38 (2H, d,
J ϭ 8.79Hz, phenyl ring), 6.58 (1H, dd, J ϭ 3.42,
1.47Hz, furan); ␦C 205.8 (C"S), 157.3, 146.8, 137.2,
136.9, 129.8, 127.6, 116.4, 113.6.
p-bromophenyl dithio-2-furoate: m. p. 86–87ЊC,
IR (KBr), 3128 (C9H, furan), 1554, 1452 (C"C,
aromatic), 1058 (C"S), 804 (C9H, aromatic); ␦H
(CDCl3 ), 7.70 (1H, s, furan), 7.62 (2H, d, J ϭ
8.30Hz, phenyl ring), 7.45 (1H, d, J ϭ 3.91Hz, furan),
7.31 (1H, d, J ϭ 8.79Hz, phenyl ring), 6.58 (1H, dd,
J ϭ 3.42, 1.47Hz, furan); ␦C 205.6 (C"S), 157.3,
146.8, 137.3, 132.7, 128.1, 125.2, 116.4, 113.6.
Kinetic Procedure
The reactions were followed conductimetrically under
pseudo-first-order condition with excess amount of
3
amine, [substrate] Х 10Ϫ M and [N] Х 0.03–0.5M.
The rate constants, kN in eq. (3), were obtained as de-
scribed previously [3,19]. The rate constants reported
were averages of more than two determinations and
were reproducible to Ϯ5%.
Product Analysis
Substrate, phenyl dithio-2-thiophenate (dithio-2-fu-
roate) (0.05 mole) and aniline (0.5 mole) were added
to acetonitrile and reacted at 40.0ЊC under the same
condition as the kinetic measurements. After more
than 15 half-lives, solvent was removed under reduced
pressure and anilide was separated by column chro-
matography. Analytical data are as follows.

ARYL DITHIO-2-THIOPHENATES AND DITHIO-2-FUROATES
857
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C4H3SC("S)NHCH2C6H5 : m. p. 85–87ЊC, IR
(KBr), 3073 (thiophene, C9H), 1120 (C"S), 811
(aromatic, C9H); ␦H (CDCl3 ), 8.55 (1H, br.s, NH),
6.98–7.56 (8H, m, phenyl, and thiophene), 4.53 (2H,
s, CH3 ), ␦C 170.9, 137.9, 135.5, 132.0, 130.0, 128.4,
128.2, 127.6, 127.2, 43.8.
C4H3SC("S)NHC6H5 : m. p. 74–76ЊC, IR (KBr),
2927 (thiophene, C9H), 1122 (C"S), 818 (aro-
matic, C9H); ␦H (CDCl3 ), 8.62 (1H, br.s, NH), 6.98–
7.76 (8H, m, aromatic, and thiophene), ␦C 182.0,
139.2, 135.4, 131.9, 129.1, 128.6, 128.5, 127.6, 124.2.
C4H3OC("S)NHCH2C6H5 : m. p. 81–83ЊC, IR
(KBr), 3374 (furan, C9H), 1070 (C"S), 811 (aro-
matic, C9H); ␦H (CDCl3 ), 8.18 (1H, br.s, NH), 6.44–
7.47 (8H, m, phenyl, and furan), 4.97 (2H, d, J ϭ
5.37Hz, CH2 ), ␦C 182.0, 151.9, 143.6, 136.1, 128.7,
128.1, 127.8, 117.9, 113.0, 48.9.
C4H3OC("S)NHC6H5 : m. p. 65–67ЊC, IR (KBr),
3356 (furan, C9H), 1072 (C"S), 811 (aromatic, C
9H); ␦H (CDCl3 ), 8.11 (1H, br.s, NH), 6.52–7.81
(8H, m, aromatic, and furan), ␦C 180.3, 152.7, 143.6,
137.8, 128.8, 126.7, 123.5, 118.5, 113.5.
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14. W. J. Hehre, L. Radom, P. v. R. Schleyer, and J. A.
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New York, Chapter 4, (1986).
We thank the Ministry of Education of Korea for a Basic
Science Research Grant (BSRI-97-3431) for this work, and,
also, Inha University for the continued support.
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and 0 for III, IV, and I, respectively. O. Exner, in
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man, and J. Shorter, Plenum, New York, Chapter 10,
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17. H. J. Koh, J-W. Lee, H. W. Lee, and I. Lee, Submitted.
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Soc., 107, 7472 (1987); (b) I. Lee, W. H. Lee, H. W.
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