Kinetics and mechanism of the anilinolysis of S-aryl N-arylthiocarbamates in acetonitrile

Article abstract of DOI:10.1002/poc.1418

The aminolysis reactions of S-aryl N-arylthiocarbamates (YC ₆H₄NH-C(=O)-SC₆H₄Z, 1) with anilines in acetonitrile are studied. The reaction rates are more influenced by the nucleophilicity of the nucleophile than the nucleofugality of the leaving group, but the change In the effective charge from reactants to the TS for formation of the tetrahedral intermediate is slightly greater in the leaving group (β_z from-0.07 to -0.14) than In the nucleophile (β_x = 0.04-0.12). The magnitude of the Broensted coefficients are in the range of values that are consistent for a stepwise mechanism with rate-limiting formation of the zwitterionic tetrahedral intermediate. Signs of cross-interaction constants, ρ_xy (>0), ρxz (>0) and ρyz (<0), are all consistent with a stepwise mechanism. It Is concluded that the change of the amine from benzylamines to anilines causes a shift of the aminolysis mechanism from a concerted to a stepwise process. Copyright

Full text of DOI:10.1002/poc.1418

Research Article
Received: 15 December 2007,
Revised: 10 May 2008,
Accepted: 5 June 2008,
Published online in Wiley InterScience: 10 July 2008
(www.interscience.wiley.com) DOI 10.1002/poc.1418
Kinetics and mechanism of the anilinolysis of
S-aryl N-arylthiocarbamates in acetonitrile
a
a
a
b
*
Dae Dong Sung , Hee Man Jang , Dae Il Jung and Ikchoon Lee
—
The aminolysis reactions of S-aryl N-arylthiocarbamates (YC H NH—C( O)—SC H Z, 1) with anilines in acetonitrile
—
6
4
6 4
are studied. The reaction rates are more influenced by the nucleophilicity of the nucleophile than the nucleofugality of
the leaving group, but the change in the effective charge from reactants to the TS for formation of the tetrahedral
intermediate is slightly greater in the leaving group (bZ fromꢀ0.07 to ꢀ0.14) than in the nucleophile (bX ¼ 0.04–0.12).
¨
The magnitude of the Bronsted coefficients are in the range of values that are consistent for a stepwise mechanism
with rate-limiting formation of the zwitterionic tetrahedral intermediate. Signs of cross-interaction constants, rXY
(>0), rXZ (>0) and rYZ (<0), are all consistent with a stepwise mechanism. It is concluded that the change of the amine
from benzylamines to anilines causes a shift of the aminolysis mechanism from a concerted to a stepwise process.
Copyright ß 2008 John Wiley & Sons, Ltd.
Supporting information may be found in the online version of this article.
Keywords: S-aryl N-arylthiocarbamate; cross-interaction constant; stepwise mechanism; zwitterionic intermediate; kinetic
isotope effect
INTRODUCTION
The object of this work is to shed more light into the
mechanism of the aminolysis of carbamates, and to investigate
the influence of the amine nature on the mechanism and
transition state structure by comparing the present reaction with
the aminolysis results for benzylamines. In this work, we
determined cross-interaction constants,[18,19] rij (eqn (2)) where
i and j are substituents X, Y, or Z in eqn (1), in order to shed
more light on the mechanism.
Although the mechanisms of the aminolysis of esters and
carbonates have been extensively studied, relatively less
attention has been given to those for carbamates. In our recent
experimental[1–3] and theoretical[4] works, the aminolyses of
carbamates have been shown to proceed by a direct displace-
ment, concerted mechanism, in contrast to
a stepwise
mechanism involving zwitterionic tetrahedral intermediates for
the aminolysis of esters[5–9] and carbonates.[10–13] According to
natural bond orbital (NBO)[4,14,15] analyses, the major cause of this
mechanistic variation for the carbamates is a considerable charge
transfer of nonbonding orbital electrons on the amino nitrogen,
nN, to the carbonyl pCꢁO orbital, a vicinal nN ! pCꢁO charge transfer
interaction,[4,14–17] which in effect enhances the leaving ability of
the phenolate or thiolate group. In the esters there is no vicinal
nonbonding orbital and hence this type of vicinal charge transfer
is lacking, whereas in the carbonates the charge transfer of the
vicinal nonbonding orbital, nO, of the methoxy oxygen to pꢁCO is
not strong enough to sufficiently weaken the carbonyl-leaving
group bond to induce a concerted process.
logðkij=kHHÞ ¼ risi þ rjsj þ rijsisj
(2)
RESULTS AND DISCUSSION
Reactions (1), carried out with excess aniline ([S] ¼ 5 ꢂ 10ꢀ5 M
and [An] ¼ 3–5 ꢂ 10ꢀ1 M) in acetonitrile followed clean, pseudo-
first-order kinetics given by the following eqns (3) and (4), where
S and An denote the substrate and the aniline, respectively.
rate ¼ kobs½Sꢃ
kobs ¼ k2½Anꢃ
(3)
(4)
In the present work, we have investigated the anilinolysis of
—
S-aryl N-arylthiocarbamates, Y—C H —NHC( O)—SC H Z, 1,
—
6
4
6 4
where Y and Z are substituents on the nonleaving and leaving
groups, respectively, in acetonitrile, eqn (1). We have used
anilines, XC6H4NH2 with X ¼ p-OMe, p-Me, H, p-Cl, or p-NO2,
instead of benzylamines which were used in the previous kinetic
studies of the carbamate aminolysis.[1–3]
*
Correspondence to: D. D. Sung, Department of Chemistry, Dong-A University,
Busan, 604-714, Korea.
E-mail: ddsung@dau.ac.kr
a
D. D. Sung, H. M. Jang, D. I. Jung, I. Lee
Department of Chemistry, Dong-A University, Busan 604-714, Korea
2XC6H4NH2 þ YC6H4NH ꢀ Cð¼OÞ ꢀ SC6H4Z !
1
(1)
b
I. Lee
Department of Chemistry, Inha University, Inchon 402-751, Korea
YC6H4NH ꢀ Cð¼OÞ ꢀ NHC6H4X þ XC6H4NHþ3 þ ZC6H4Sꢀ
J. Phys. Org. Chem. 2008, 21 1014–1019
Copyright ß 2008 John Wiley & Sons, Ltd.

ANILINOLYSIS OF S-ARYL N-ARYLTHIOCARBAMATES
The second-order rate constants, k2, obtained are summarized
¨
Table 1. The second-order rate constants, k2 (ꢂ103 Mꢀ1 sꢀ1) ,
*
in Table 1. The Hammett (rX, rY, and rZ) and Bronsted [bX (bnuc
)
for the reactions of S-aryl N-arylthiocarbamates
—
and bZ (blg)] coefficients are collected in Table 2. In the
determination of bX, we found that the values obtained
with pKas in water are 1.25-fold uniformly greater than those
determined with pKas in acetonitrile.[20] The magnitude of rX
(ꢀ0.60 for Y ¼ Z ¼ H) is in general larger than that of rZ (0.31 for
Y ¼ X ¼ H) indicating that the positive charge development on
the nitrogen atom of aniline is greater than the negative charge
developed on the sulfur atom of the leaving group in the TS. In
contrast, the magnitude of bz (for Y ¼ Br, average bZ ¼ ꢀ0.10
with pKas in water)[21] is somewhat larger than that of bX (for
Y ¼ Br, average of bX ¼ 0.07 with pKas in water) which implies that
the change in effective charge at the TS is somewhat greater in
the leaving group than that in the nucleophile. This is further
supported by the negative sign of rY values in Table 2. We note,
however, that the magnitude of both bX (0.04–0.12) and bZ (from
ꢀ0.07 to ꢀ0.18) is rather small, which is in the range of values
(bX ¼ ꢀbZ ¼ 0–0.4) normally found for a stepwise mechanism
where the formation of a zwitterionic tetrahedral intermediate is
the rate-determining step.[5,22–29] It has been shown that the bX
values are normally greater than ca. 0.8 for a stepwise mechanism
with rate-limiting breakdown of the intermediate,[5–13] while they
are in the range of 0.4–0.6 for a concerted aminolysis
(YC H NH-C( O)-SC H Z) with anilines (XC H NH ) in
—
6
4
6
4
6
4
2
acetonitrile at 25.0 8C
X
Y
Z
p-OMe
p-Me
H
p-Cl
p-NO2
H
p-OMe
p-Me
H
7.01
7.48
8.36
9.75
14.0
2.10
2.18
2.33
2.55
3.16
2.03
2.12
2.27
2.48
3.06
6.11
6.52
7.28
8.55
12.5
1.93
2.02
2.17
2.40
3.06
1.86
1.94
2.08
2.29
2.90
4.73
5.11
5.75
6.79
3.29
3.59
4.10
4.95
7.71
1.38
1.46
1.60
1.81
2.46
1.35
1.43
1.56
1.78
2.40
1.47
1.65
1.93
2.43
4.05
0.867
0.937
1.06
1.25
1.87
0.857
0.920
1.04
1.23
1.83
p-Cl
p-NO2
p-OMe
p-Me
H
10.1
p-Cl
p-Br
1.67
1.76
1.90
2.12
2.77
1.64
1.71
1.85
2.04
2.64
p-Cl
p-NO2
p-OMe
p-Me
H
p-Cl
p-NO2
process.[1–3,22–31] Based on the magnitude of Bronsted coeffi-
¨
cients therefore, we propose that reaction (1), proceeds through a
zwitterionic tetrahedral intermediate, Tꢄ, 2, the formation of
which is rate determining.
*
The k2 values are averages of more than three kinetic runs
and were reproducible to within ꢄ 3%.
˝
Table 2. Hammett (rx, ry, and rz) and Bronsted (in parentheses) coefficients for the reactions of S-aryl N-arylthiocarbamates with
anilines in acetonitrile at 25.0 8C
Y/Z
p-OMe
p-Me
H
p-Cl
p-NO2
rX and (bX) valuesa
H
p-Cl
p-Br
ꢀ0.65 (0.12)
ꢀ0.37 (0.07)
ꢀ0.36 (0.07)
ꢀ0.63 (0.11)
ꢀ0.35 (0.06)
ꢀ0.34 (0.06)
ꢀ0.60 (0.10)
ꢀ0.58 (0.11)
ꢀ0.30 (0.05)
ꢀ0.29 (0.05)
ꢀ0.51 (0.09)
ꢀ0.22 (0.04)
ꢀ0.21 (0.04)
ꢀ0.33 (0.06)
ꢀ0.32 (0.06)
Y/X
p-OMe
p-Me
H
p-Cl
p-NO2
rZ and (bZ) valuesb
H
p-Cl
p-Br
0.29 (ꢀ0.13)
0.17 (ꢀ0.07)
0.17 (ꢀ0.07)
0.30 (ꢀ0.13)
0.19 (ꢀ0.08)
0.18 (ꢀ0.08)
0.31 (ꢀ0.14)
0.21 (ꢀ0.09)
0.20 (ꢀ0.09)
0.35 (ꢀ0.15)
0.24 (ꢀ0.10)
0.24 (ꢀ0.10)
0.42 (ꢀ0.18)
0.32 (ꢀ0.14)
0.31 (ꢀ0.14)
X/Z
p-OMe
p-Me
H
p-Cl
p-NO2
rY valuesc
p-OMe
p-Me
H
p-Cl
p-NO2
ꢀ2.26
ꢀ2.16
ꢀ1.94
ꢀ1.63
ꢀ0.99
ꢀ2.30
ꢀ2.20
ꢀ2.00
ꢀ1.68
ꢀ1.06
ꢀ2.38
ꢀ2.27
ꢀ2.07
ꢀ1.76
ꢀ1.12
ꢀ2.50
ꢀ2.39
ꢀ2.19
ꢀ1.87
ꢀ1.24
ꢀ2.77
ꢀ2.65
ꢀ2.43
ꢀ2.13
ꢀ1.45
a The correlation coefficients were better than 0.991, and standard deviations were less than 0.01 (with an average value of 0.006) in
all cases. bX values were determined with pKas in acetonitrile8a.
b The correlation coefficients were better than 0.996, and standard deviations were less than 0.01.in all cases. bZ values were
determined with pKas in water8b at 25 8C.
c The correlation coefficients were better than 0.999, and standard deviations were less than 0.05 in all cases.
J. Phys. Org. Chem. 2008, 21 1014–1019
Copyright ß 2008 John Wiley & Sons, Ltd.
www.interscience.wiley.com/journal/poc

D. D. SUNG ET AL.
Table 3. Cross-interaction constants, rxy, rxz, and ryz, for the
reactions of S-aryl N-aryl thiocarbamates with anilines in
acetonitrile at 25.0 8C
Z
rXY
rXY valuesa
p-OMe
p-Me
H
p-Cl
p-NO2
1.23 ꢄ 0.03
1.20 ꢄ 0.02
1.21 ꢄ 0.03
1.21 ꢄ 0.03
1.27 ꢄ 0.03
In this type of TS, the changes in effective charge from
reactants to the TS for formation of the tetrahedral intermediate,
bX (bnuc) and ꢀbZ (ꢀblg), are small ranging from 0 to 0.4, and in
some cases the ꢀbZ values become greater than the bX values.
Such examples are found in the work of Castro group on the
aminolysis of 2,4-dinitrophenyl and 2,4,6-trinitrophenyl thiolace-
tates (bX ¼ 0.2 and bZ ¼ ꢀ0.3),[24] and in the work of Jencks group
on the acyl transfer reactions between sulfur and oxygen
nucleophiles (bX ¼ 0.2 and bZ ¼ ꢀ0.3).[9] Thus, in the stepwise
reactions with rate-limiting bond formation, changes in the
effective charge on the nitrogen of the aniline nucleophile and on
the sulfur of the leaving group are small, but the latter can be
larger. This does not mean that the reaction proceeds
concertedly[24,26] since the effective charge change is involved
in the process of formation of the zwitterionic tetrahedral
intermediate. According to our DFT calculations at the B3LYP/
Y
rXZ
rXZ valuesa
H
p-Cl
p-Br
0.13 ꢄ 0.01
0.14 ꢄ 0.02
0.14 ꢄ 0.01
X
rYZ
rYZ valuesa
p-OMe
p-Me
H
p-Cl
p-NO2
ꢀ0.50 ꢄ 0.04
ꢀ0.47 ꢄ 0.01
ꢀ0.47 ꢄ 0.02
ꢀ0.48 ꢄ 0.03
ꢀ0.43 ꢄ 0.02
6-31G level of theory[4,32] in the gas phase, the C—S bond
**
a The R2 values were greater than 0.9997 in all cases, and
Fischer’s F-tests at the 99.9% confidence level by comparing
the calculated F-values (Fcalc) with the tabulated F-value
(Ftab ¼ 999.5)[33] indicated that the results of the multiple
regressions are highly significant (Fcal > > Ftab).
˚
stretches from 1.839 to 1.844 A while the Mulliken charge of the
carbonyl carbon increases from þ 0.4131 to þ 0.4183 in going
from the reactants to the TS for formation of the tetrahedral
intermediate 3, which is formed from S-phenyl thiocarbamate
—
(NH —(C O)—SPh) and ammonia. In general, charged species
—
2
are more stabilized in solvents than in the gas phase so that this
gas-phase results can serve as an indication that the effective
charge development for rate-limiting formation can be larger in
the leaving group than in the nucleophile.
Amine nature is one of the key factors that influences the
mechanism of the aminolysis reactions of esters, carbonates, and
carbamates.[2,13,35] The rate of amine expulsion from Tꢄ increases
in the order pyridines < anilines < secondary alicyclic ami-
nes < quinuclidines < benzylamines and the stability of the
zwitterionic intermediate, Tꢄ, increases in the reverse
order.[13,34,35] Thus, pyridine nucleophiles are most likely to lead
the aminolysis to a stepwise reaction with a stable intermediate,
whereas benzylamines are known to strongly destabilize Tꢄ so
that the intermediate cannot exist and as a result the aminolysis
reactions are likely to proceed by a
NH2 ꢀ Cð¼ OÞ ꢀ SAr
EtNH ꢀ Cð¼ OÞ ꢀ SAr
4
5
YC6H4NH ꢀ Cð¼ OÞ ꢀ OC6H4 ꢀ p ꢀ NO2
The cross-interaction constants, rXY, rXZ, and rYZ, determined
by multiple regression using eqn (2) are shown in Table 3. The
signs of these constants, rXY > 0, rXZ > 0, and rYZ < 0, are indeed
consistent with our proposed mechanism of the stepwise
process.[19,34,35] It has been shown that in a concerted aminolysis,
the signs of these constants are all reversed to rXY < 0, rXZ < 0
,and rYZ > 0.[19,34,35] The variations of these constants with
substituents are negligible, i.e.,the values of rXYZ, are very small
(ꢅ0) in all cases. For example, rXY varies from 1.23 for Z ¼ p-OMe
to 1.27 for Z ¼ p-NO2 so that rXYZ ꢅ 0.04. This is an indication of a
loose C-nucleophile bond in the TS, as we have proposed above
6
concerted pathway.[34,35] For example, aminolyses of S-aryl-,[1] 4,
S-aryl N-ethyl-,[2] 5, and p-nitrophenyl N-aryl carbamates,[3] 1, with
benzylamines in acetonitrile were found to proceed by a concerted
mechanism, while pyridinolyses of many aryl esters and
carbonates are reported to proceed by a stepwise mechanism
through a zwitterionic tetrahedral intermediate.[36–43]
Anilines destabilize the tetrahedral intermediate relative to
pyridines but stabilize it compared with benzylamines. The
nucleofugality of anilines from Tꢄ being intermediate between
the two extremes, mechanistic changes can occur readily when
¨
based on the small magnitude of the Bronsted bX coefficients.
www.interscience.wiley.com/journal/poc
Copyright ß 2008 John Wiley & Sons, Ltd.
J. Phys. Org. Chem. 2008, 21 1014–1019

ANILINOLYSIS OF S-ARYL N-ARYLTHIOCARBAMATES
other factors are varied. For example, the aminolyses of S-aryl
—
pressure. The product was separated by column chromatography
on aluminum oxide (neutral Al2O3 grade 90, 63–200 mm) eluted
with diethyl ether (10%)-n-hexane.
O-ethyl thiocarbonates [EtO–C( O)–SC H Z] with anilines are
—
6
4
reported to shift from stepwise for a poorer leaving group
[Z ¼ 2,4-(NO2)2] to concerted manner for a better leaving group
[Z ¼ 2,4,6-(NO2)3].[44] This means that the nucleofugality of the
leaving group from Tꢄ is also a key factor influencing the
aminolysis mechanism of carbonates and carbamates. For
example, the aminolysis of p-nitrophenyl N-arycarbamates, 6,
with benzylamines is stepwise[45] in acetonitrile due to the low
nucleofugality of phenolate (OPhꢀ) relative to thiolate (SPhꢀ) in 1
despite the strong leaving ability of benzylamines from Tꢄ. The
stepwise mechanism proposed for the present anilinolysis
reactions of S-aryl N-arylthiocarbamates is therefore reasonable
in view of the possible mechanistic shift to a stepwise process by
changing the amine to aniline from benzylamine,[3] for which a
concerted process was observed.
S-Phenyl N-phenylthiocarbamate. IR (KBr (cmꢀ1)), N—H;
—
—
3257.3, C O; 1670, C—S; 1010.5, C C (Ar); 1486.9,1596.8,
—
—
Ar—H; (3182.1, 3108.8, 3043.3, 2923.7, 2852.3), 1H-NMR (350 MHz,
acetonitrile-d3) d 7.19–7.29 (4H, m, aromatic), 7.39–7.47 (2H, t,
aromatic), 7.56–7.72 (4H, m, aromatic), 8.27 (1H, s, NH).
S-p-Nitrophenyl N-phenylthiocarbamate. IR (KBr (cmꢀ1)), N—H;
—
3257.3, C O; 1670, C—NO ; 1107, Ar—NO ; 885, C—S; 1010.5,
—
2
2
—
C
C (Ar); 1486.9, 1596.8, Ar—H; (3182.1, 3108.8, 3043.3, 2923.7,
—
2852.3), 1H-NMR (350 MHz acetonitrile-d3) d 7.15–7.24 (1H, m,
aromatic), 7.40–7.47 (2H, t, aromatic), 7.61–7.72 (4H, m, aromatic),
8.00 (1H, s, NH), 8.12–8.20 (2H, d, aromatic).
S-p-Methylphenyl N-phenylthiocarbamate. IR (KBr (cmꢀ1)),
—
—
N—H; 3257.3, C O; 1670, C—S; 1010.5, C C (Ar); 1486.9,
—
—
The solvent change from water to a less polar solvent, MeCN,
can cause a mechanistic stepwise change in water to a
concerted change in acetonitrile, mainly due to a decrease in
the stability of zwitterionic intermediates in MeCN.[46] The
higher expulsion rate of the amine from Tꢄ in a less polar solvent
leads to a lower stability of Tꢄ. However, in many cases due to
other stronger effects, mechanistic changes are not observed
and the same mechanism is observed in both water and in
MeCN.[34,35]
1596.8, CH3; 2950.8, 1480.4 Ar—H; (3182.1, 3108.8, 3043.3, 2923.7,
2852.3), 1H-NMR; (350 MHz acetonitrile-d3) d 2.17 (3H, s, CH3),
6.82–6.89 (2H, d, aromatic), 7.06–7.15 (2H, d, aromatic), 7.19–7.28
(1H, m, aromatic), 7.40–7.48 (2H, m, aromatic), 7.52–7.63 (2H, d,
aromatic), 8.90 (1H, s, NH).
S-p-Methoxyphenyl N-phenylthiocarbamate. IR (KBr (cmꢀ1)),
—
—
N—H; 3257.3, C O; 1670, C—S; 1010.5, C C (Ar); 1486.9,
—
—
1596.8, OCH3; 1000, 1250, 2940, Ar—H; (3182.1, 3108.8, 3043.3,
1
2923.7, 2852.3), H-NMR (350 MHz, acetonitrile-d3) d 3.83 (3H, s,
The kinetic isotope effects, kH/kD, involving deuterated
anilines[47] (XC6H4ND2) are normal but negligible as shown in
Table 4 (Supporting Information). This is in line with the proposed
mechanism since the TS is very loose in the process involving the
formation of the tetrahedral intermediate. The activation
parameters, DH and DS , in Table 5 (Supporting Information)
are also consistent with our proposed mechanism. The activation
enthalpies (ca. 10 kcal/mol) are lower than those for the stepwise
process with rate-limiting breakdown of the intermediate (ca.
14 kcal/mol for 6 with benzylamines)[45] but are higher than those
for the H-bonded cyclic TS in the concerted processes (ca. 8 kcal/
mol for 4 with benzylamines).[1] The entropies of activations (ca.
ꢀ35 e.u.) are also intermediate between the two (ꢀ13 for 6, and
ꢀ37 e.u. for 4 with benzylamines).[1,45]
OCH3),7.19–7.28 (1H, m, aromatic), 7.40–7.51 (6H, m, aromatic),
7.60–7.65 (2H, d, aromatic), 8.36 (1H, s, NH).
S-p-Chlorophenyl N-phenylthiocarbamate. IR (KBr (cmꢀ1)),
—
—
N—H; 3257.3, C O; 1670, C—S; 1010.5, C C (Ar); 1486.9,
—
—
1
1596.8, Ar—H; (3182.1, 3108.8, 3043.3, 2923.7, 2852.3), H-NMR
(350 MHz acetonitrile-d3) d 7.01–7.05 (1H, m, aromatic), 7.36 (4H, s,
aromatic), 7.42–7.47 (2H, m, aromatic), 7.61–7.65 (2H, d, aromatic),
8.36 (1H, s, NH).
¼
¼
S-p-Chlorophenyl N-p-chlorophenylthiocarbamate. IR (KBr
—
(cmꢀ1)), N—H; 3257.3, C O; 1670, C—S; 1010.5, C C (Ar);
—
—
—
1486.9, 1596.8, Ar—H; (3182.1, 3108.8, 3043.3, 2923.7, 2852.3),
1H-NMR (350 MHz acetonitrile-d3) d 7.28–7.33 (4H, s, aromatic),
7.43–7.49 (2H, d, aromatic), 7.69–7.76 (2H, d, aromatic), 8.58 (1H, s,
NH).
S-p-Nitrophenyl N-p-chlorophenylthiocarbamate. IR (KBr
(cmꢀ1)), N—H; 3257.3, C O; 1670, C—S; 1010.5, Ar-NO ; 885,
—
—
C (Ar); 1486.9, 1596.8, Ar—H; (3182.1, 3108.8, 3043.3, 2923.7,
2
—
—
C
EXPERIMENTAL
2852.3), 1H-NMR (350 MHz acetonitrile-d3) d 7.15–7.19 (2H, d,
aromatic), 7.64–7.69 (2H, d, aromatic), 7.70–7.76 (2H, d, aromatic),
8.06 (1H, s, NH), 8.59–8.62 (2H, d, aromatic).
Materials
General procedure
S-p-Methylphenyl N-p-chlorophenylthiocarbamate. IR (KBr
(cmꢀ1)), N—H; 3257.3, C O; 1670, C—S; 1010.5, CH ; 2950.8,
—
GR grade acetonitrile was purchased from Aldrich and used after
re-distillation. The aniline nucleophilesof GR grade from Aldrich
were used after re-crystallization or re-distillation. FT-IR spectra
were taken using a Bruker IFS 55 spectrophotometer. 1H NMR
spectra were recorded on a Bruker DPX 300 MHz-NMR instrument
using CD3CN and CDCl3 as solvents with TMS as an internal
standard.
Preparation of S-p-substituted phenyl N-p-substituted phenyl-
carbamates. These were prepared by the literature method of
Velikorodov,[48] Moseley,[49] and Knapton.[50] To a solution of
0.1 mol of thiophenol and phenyl isocyanate in 20 ml of toluene,
10 ml of pyridine was added and purged with argon into the
solution. The reaction mixture was stirred for 2 h at 25 8C. When
the reaction was completed, the solid was filtered under reduced
pressure. The solid was added to the solvent mixture of
chloroform and n-pentane (2:1 v/v%) and filtered under reduced
—
3
—
1480.4, C C (Ar); 1486.9, 1596.8, Ar—H; (3182.1, 3108.8, 3043.3,
—
2923.7, 2852.3), 1H-NMR (350 MHz acetonitrile-d3) d 3.85 (3H,
s, CH3), 6.86–6.92 (2H, d, aromatic), 7.04–7.09 (2H, d, aromatic),
7.43–7.48 (2H, d, aromatic), 7.71–7.75 (2H, d, aromatic), 8.73 (1H, s,
NH).
S-p-Methoxyphenyl N-p-chlorophenylthiocarbamate. IR (KBr
(cmꢀ1)), N—H; 3257.3, C O; 1670, C—S; 1010.5, C C (Ar);
—
—
—
—
1486.9, 1596.8, OCH3; 1000, 1250, 2940, Ar—H; (3182.1, 3108.8,
1
3043.3, 2923.7, 2852.3), H-NMR (350 MHz acetonitrile-d3) d 3.81
(3H, s, OCH3), 7.13–7.47 (6H, m, aromatic), 7.73–7.78 (2H, d,
aromatic), 8.80 (1H, s, NH).
S-Phenyl N-p-chlorophenylthiocarbamate. IR (KBr (cmꢀ1)),
—
—
N—H; 3257.3, C O; 1670, C—S; 1010.5, C C (Ar); 1486.9,
—
—
1
1596.8, Ar—H; (3182.1, 3108.8, 3043.3, 2923.7, 2852.3), H-NMR
(350 MHz acetonitrile-d3) d 7.19–7.29 (3H, m, aromatic), 7.41–7.47
J. Phys. Org. Chem. 2008, 21 1014–1019
Copyright ß 2008 John Wiley & Sons, Ltd.
www.interscience.wiley.com/journal/poc

D. D. SUNG ET AL.
(2H, d, aromatic), 7.53–7.58 (2H, d, aromatic), 7.72–7.77 (2H, d,
aromatic), 8.60 (1H, s, NH).
S-p-Nitrophenyl N-p-bromophenylthiocarbamate. IR (KBr
for C14H13N2O2Br: C, 52.4; H, 4.10; N, 8.73. Found; C, 52.5; H,
4.11; N,8.74.
(cmꢀ1)), N—H; 3257.3, Ar—Br; 1070.3, Ar—NO ; 885, C O;
—
—
2
—
1670, C—S; 1010.5, C C (Ar); 1486.9, 1596.8, Ar—H; (3182.1,
—
Acknowledgements
3108.8, 3043.3, 2923.7, 2852.3), 1H-NMR (350 MHz acetonitrile-d3)
d 7.49–7.74 (6H, m, aromatic), 8.27 (1H, s, NH), 8.71–8.75 (2H, d,
aromatic).
This work was supported by a Korea Research Foundation Grant
funded by the Korean Government (MOEHRD)(KRF-2006-
042-C00074).
S-Phenyl N-p-bromophenythiocarbamate. IR (KBr (cmꢀ1)),
—
—
C
—
N—H; 3257.3, Ar—Br; 1070.3, C O; 1670, C—S; 1010.5, C
—
(Ar); 1486.9, 1596.8, Ar—H; (3182.1, 3108.8, 3043.3, 2923.7,
2852.3), 1H-NMR (350 MHz acetonitrile-d3) d 7.11–7.29 (3H, m,
aromatic), 7.53–7.58 (4H, t, aromatic), 7.67–7.74 (2H, d, aromatic),
8.40 (1H, s, NH).
REFERENCES
S-p-Methylphenyl N-p-bromophenylthiocarbamate. IR (KBr
(cmꢀ1)), N—H; 3257.3, Ar—Br; 1070.3, C O; 1670, C—S;
—
—
[1] H. K. Oh, Y. C. Jin, D. D. Sung, I. Lee, Org. Biomol. Chem. 2005, 3, 1240.
[2] H. K. Oh, J. E. Park, D. D. Sung, I. Lee, J. Org. Chem. 2004, 69, 9285.
[3] H. K. Oh, J. E. Park, D. D. Sung, I. Lee, J. Org. Chem. 2004, 69, 3150.
[4] D. D. Sung, I. S. Han, I. Lee, J. Sulfur Chem. 2007, 28, 483.
[5] A. C. Satterthwait, W. P. Jencks, J. Am. Chem. Soc. 1974, 96, 7018.
[6] M. J. Gresser, W. P. Jencks, J. Am. Chem. Soc. 1977, 99, (6963), 6970.
[7] E. A. Castro, Chem. Rev. 1999, 99, 3505.
—
1010.5, CH ; 2950.8, 1480.4, C C (Ar); 1486.9, 1596.8, Ar—H;
—
3
(3182.1, 3108.8, 3043.3, 2923.7, 2852.3), 1H-NMR (350 MHz
acetonitrile-d3) d 2.37 (3H, s, CH3), 6.84–6.89 (2H, d, aromatic),
7.07–7.11 (2H, d, aromatic), 7.53–7.58 (2H, d, aromatic), 7.65–7.70
(2H, d, aromatic), 8.74 (1H, s, NH).
[8] I.-H. Um, J.-A. Seok, H.-T. Kim, S.-K. Bae, J. Org. Chem. 2003, 68, 7742.
[9] D. J. Hupe, W. P. Jencks, J. Am. Chem. Soc. 1977, 99, 451.
[10] E. A. Castro, F. J. Gil, J. Am. Chem. Soc. 1977, 99, 7611.
[11] E. A. Castro, L. Leandro, P. Millan, J. G. Santos, J. Org. Chem. 1999, 64,
1953.
[12] E. A. Castro, M. Cubillos, J. G. Santos, J. Org. Chem. 1996, 61, 3501.
[13] E. A. Castro, M. Aliaga, P. Campodonico, J. G. Santos, J. Org. Chem.
2002, 67, 8911.
[14] A. Reed, L. A. Curtis, F. Weinhold, Chem. Rev. 1988, 88, 899.
[15] F. Weinhold, C. R. Landis, Valency and Bonding. A. Natural Bond Orbital
Donor–Acceptor Perspective, Cambridge University Press, Cambridge,
2005.
[16] N. D. Epiotis, W. R. Cherry, S. Shaik, R. L. Yates, F. Bernardi, Structural
Theory of Organic Chemistry, Springer, Berlin, 1977.
[17] A. Rauk, Orbital Interaction Theory of Organic Chemistry, Wiley, New
York, 1994.
S-p-Methoxyphenyl N-p-bromophenylthiocarbamate. IR (KBr
(cmꢀ1)), N—H; 3257.3, Ar—Br; 1070.3, C O; 1670, C—S; 1010.5,
—
—
—
C
C (Ar); 1486.9, 1596.8, OCH ; 1000, 1250, 2940, Ar—H; (3182.1,
3
—
3108.8, 3043.3, 2923.7, 2852.3),1H-NMR (350 MHz acetonitrile-d3)
d 3.83 (3H, s, OCH3), 7.42–7.51 (4H, m, aromatic), 7.55–7.60 (2H, d,
aromatic), 7.71–7.75 (2H, d, aromatic), 8.34 (1H, s, NH).
S-p-Chlorophenyl N-p-bromophenylthiocarbamate. IR (KBr
(cmꢀ1)), N—H; 3257.3, Ar—Br; 1070.3, C O; 1670, C—S;
—
—
—
1010.5, C C (Ar); 1486.9, 1596.8, Ar—H; (3182.1, 3108.8,
—
3043.3, 2923.7, 2852.3),1H-NMR (350 MHz, acetonitrile-d3) d 7.33
(4H, s, aromatic), 7.52–7.58 (2H, d, aromatic), 7.64–7.70 (2H, d,
aromatic), 8.59 (1H, s, NH).
[18] I. Lee, Chem. Soc. Rev. 1990, 19, 317.
[19] I. Lee, Adv. Phys. Org. Chem. 1992, 27, 57.
Kinetic measurements
[20] I. Kaljurand, A. Kutt, L. Soovah, T. Rodima, V. Maemets, I. Leito, I. A.
Koppel, J. Org. Chem. 2005, 70, 1019.
[21] C Ed.: J. Buckingham. Dictionary of Organic Compounds, (5th edn).
Chapman & Hall, New York, 1982.
[22] A. R. Butler, I. H. Robertson, R. Bacaloglu, J. Chem. Soc. Perkin Trans. 2,
1974, 173.
[23] H. J. Koh, K. I. Han, H. W. Lee, I. Lee, J. Org. Chem. 1998, 63, 9834.
[24] E. A. Castro, C. Ureta, J. Chem. Soc. Perkin Trans. 2, 1991, 63.
[25] D. J. Palling, W. P. Jencks, J. Am. Chem. Soc. 1984, 106, 4869.
[26] E. A. Castro, L. Leandro, N. Quesieh, J. G. Santos, J. Org. Chem. 2001,
66, 6130.
Rates were measured conductometrically in acetonitrile. The
conductivity bridge used in this study was WTW LF330
conductivity meter. Pseudo-first-order rate constants, kobs, were
determined by the Guggenheim method[51] with a large excess of
aniline, [S] ¼ 5 ꢂ 10ꢀ5 M and [An] ¼ 3–5 ꢂ 10ꢀ1 M. Second-order
rate constants, k2, were obtained from the slope of a plot of kobs
versus [An] with more than five concentrations of aniline. The k2
values are summarized in Table 1.
[27] A. R. Fersht, W. P. Jencks, J. Am. Chem. Soc. 1970, 92, 5442.
[28] E. A. Castro, P. Pavez, J. G. Santos, J. Org. Chem. 2001, 66, 3129; 2002,
67, 4494.
Product analysis
The substrate, 4-methoxy-S-phenyl thio-4-bromo-N-phenyl-
carbamate (0.1 mol) was reacted with excess aniline (0.3 mol)
and stirred for 24 h at 25 8C in acetonitrile and the product was
isolated by evaporating the solvent under reduced pressure. The
product was collected by column chromatography on aluminum
oxide (neutral Al2O3 grade 90, 63–200 mm) eluted with diethyl
ether (10%)-n-hexane. Analysis of the product gave the following
results:
4-MeO-C6H4NHCONHC6H4Br. Colorless oily liquid; 1H NMR
(350 MHz, acetonitrile-d3) d 3.74 (3H, s, CH3), 6.0 (2H, s, NH),
6.75–6.77 (2H, d, aromatic), 7.41–7.44 (2H, d, aromatic), 7.53–7.57
(4H, m, aromatic); 13C NMR (100.4 MHz, acetonitrile-d3) d 156.4,
151.9, 135.0, 132.2, 122.8, 123.9, 114.8, 55.9; nmax (KBr) 3350 (NH),
[29] E. A. Castro, M. Cubillos, F. Ibanez, I. Moraga, J. G. Santos, J. Org. Chem.
1993, 58, 5400.
[30] E. A. Castro, F. Ibanez, M. Salas, J. G. Santos, J. Org. Chem. 1991, 56,
4819.
[31] E. A. Castro, M. Salas, J. G. Santos, J. Org. Chem. 1994, 59, 30.
[32] Ed.: I. N. Levine, Quantum Chemistry, (5th edn). Prentice-Hall, Upper
Saddle River, 2000, 573.
[33] K. A. Brownlee, Statistical Theory and Methodology in Science and
Engineering; Wiley: New York 1965.
[34] I. Lee, D. D. Sung, Curr. Org. Chem. 2004, 8, 557.
[35] H. K. Oh, J. Y. Oh, D. D. Sung, I. Lee, Collect. Czech. Chem. Commun.
2004, 69, 2174.
[36] E. A. Castro, M. Freudenberg, J. Org. Chem. 1980, 45, 906.
[37] E. A. Castro, G. B. Steinfort, J. Chem. Soc. Perkin Trans. 2, 1983, 453.
[38] E. A. Castro, C. L. Santander, J. Org. Chem. 1985, 50, 3595.
[39] E. A. Castro, M. Vivanco, R. Aguayo, J. G. Santos, J. Org. Chem. 2004, 69,
5399.
—
3057 (CH, aromatic), 2837 (CH, CH ), 1598 (C C, aromatic), 1690
—
3
(C O), 576 (C—Br); MS m/z 321 (Mþ). Anal. Calcd
—
[40] H. J. Koh, K. L. Han, I. Lee, J. Org. Chem. 1999, 64, 4783.
—
www.interscience.wiley.com/journal/poc
Copyright ß 2008 John Wiley & Sons, Ltd.
J. Phys. Org. Chem. 2008, 21 1014–1019

ANILINOLYSIS OF S-ARYL N-ARYLTHIOCARBAMATES
[41] H. J. Koh, K. L. Han, H. W. Lee, I. Lee, Bull. Korean Chem. Soc. 2002, 23,
715.
[42] H. K. Oh, M. H. Ku, H. W. Lee, I. Lee, J. Org. Chem. 2002, 67, 3874.
[43] H. K. Oh, M. H. Ku, H. W. Lee, I. Lee, J. Org. Chem. 2002, 67, 8995.
[44] E. A. Castro, L. Leandro, P. Millan, J. G. Santos, J. Org. Chem. 1999, 64,
1953.
[47] I. Lee, Chem. Soc. Rev. 1995, 24, 571.
[48] A. V. Velikorodov, N. G. Urlyapova, A. D. Daudova, Pharmaceu. Chem. J.
2006, 40, 380.
[49] J. D. Moseley, R. F. Sankey, O. N. Tang, J. P. Gilday, Tetrahedron 2006, 62,
4685.
[50] D. J. Knapton, T. Y. Meyer, J. Org. Chem. 2005, 70, 785.
[51] Ed.: J. W. Moore, R. G. Pearson, Kinetics and Mechanism, (3rd edn).
Wiley, New York, 1981.
[45] H. J. Koh, O. S. Kim, H. W. Lee, I. Lee, J. Phys. Org. Chem. 1997, 10, 725.
[46] H. K. Oh, J. S. Ha, D. D. Sung, I. Lee, J. Org. Chem. 2004, 69, 8219.
J. Phys. Org. Chem. 2008, 21 1014–1019
Copyright ß 2008 John Wiley & Sons, Ltd.
www.interscience.wiley.com/journal/poc