Kinetics and mechanism of the aminolysis of dimethyl and methyl phenyl phosphinic chlorides with anilines

Article abstract of DOI:10.1002/poc.1478

The reactions of dimethyl phosphinic chloride (1) and methyl phenyl phosphinic chloride (2) with X-anilines have been studied kinetically in acetonitrile at 15.0 and 55.0 °C, respectively. The deuterium kinetic isotope effects (KIEs) involving deuterated aniline nucleophiles (XC ₆H₄ND₂) are also reported for the same reactions. The obtained KIEs for 1 are secondary inverse (k_H/k _D=0.703-0.899< 1), while those for 2 are primary normal (k _H/k_D=1.62-2.10> 1). A concerted mechanism involving predominantly backside nucleophilic attack is proposed for the anilinolysis of 1. A concerted mechanism involving predominantly frontside attack via a hydrogen-bonded four-center-type transition state is proposed for the anilinolysis of 2. The degree of steric hindrance is the major factor that determines both the reactivity of the phosphinates and the direction of the nucleophilic attack on the phosphinates. Copyright

Full text of DOI:10.1002/poc.1478

Research Article
Received: 11 September 2008,
Revised: 14 October 2008,
Accepted: 15 October 2008,
Published online in Wiley InterScience: 11 December 2008
(www.interscience.wiley.com) DOI 10.1002/poc.1478
Kinetics and mechanism of the aminolysis of
dimethyl and methyl phenyl phosphinic
chlorides with anilines
Nilay Kumar Deya, Md. Ehtesham Ul Hoquea, Chan Kyung Kima,
Bon-Su Leea and Hai Whang Leea
*
The reactions of dimethyl phosphinic chloride (1) and methyl phenyl phosphinic chloride (2) with X-anilines have been
studied kinetically in acetonitrile at 15.0 and 55.0 8C, respectively. The deuterium kinetic isotope effects (KIEs)
involving deuterated aniline nucleophiles (XC6H4ND2) are also reported for the same reactions. The obtained KIEs for
1 are secondary inverse (kH/kD ¼ 0.703–0.899 < 1), while those for 2 are primary normal (kH/kD ¼ 1.62–2.10 > 1). A
concerted mechanism involving predominantly backside nucleophilic attack is proposed for the anilinolysis of 1. A
concerted mechanism involving predominantly frontside attack via a hydrogen-bonded four-center-type transition
state is proposed for the anilinolysis of 2. The degree of steric hindrance is the major factor that determines both the
reactivity of the phosphinates and the direction of the nucleophilic attack on the phosphinates. Copyright ß 2008
John Wiley & Sons, Ltd.
Supporting information may be found in the online version of this article.
Keywords: deuterium kinetic isotope effect; anilinolysis; dimethyl phosphinic chloride; methyl phenyl phosphinic chloride;
steric effect; frontside attack
mainly on deuterium primary normal kinetic isotope effects (KIEs)
and cross-interaction constants.[13–15]
INTRODUCTION
Phosphoryl transfer reactions are known to proceed via two main
types of mechanisms: a stepwise mechanism involving a trigonal
In this work, we investigate the aminolysis of dimethyl
phosphinic chloride [1; Me2P(O)Cl] and methyl phenyl phosphinic
chloride [2; MePhP(O)Cl] with substituted anilines (XC6H4NH2) in
acetonitrile at 15.0 and 55.0 8C, respectively (Eqn (1)). The same
reactions were repeated using the corresponding deuterated
anilines (XC6H4ND2). This work aims to clarify the phosphoryl
transfer mechanism, as well as to compare the anilinolysis of
diphenyl phosphinic chloride (3),[9] dimethyl chlorophosphate [4;
(MeO)2P(O)Cl],[12] diethyl chlorophosphate [5; (EtO)2P(O)Cl],[12]
aryl ethyl chlorophosphate (6),[8] and aryl phenyl chloropho-
sphate [7; (YPhO)(PhO)P(O)Cl].[16]
bipyramidal pentacoordinate (TBP-5C) intermediate and
a
concerted mechanism via a single TBP-5C transition state
(TS).[1,2] When the nucleophile attacks the reaction center from
the side opposite the leaving group (backside attack), the
configuration is inversed. However, when the nucleophile attacks
from the leaving group side (frontside attack), the configuration is
retained. When backside and frontside nucleophilic attacks occur
simultaneously, the relative extents of these reaction pathways
lead to products with inversion or retention of the configuration.
The relative extents of the pathways depend on the nucleophile,
the leaving group and the reaction conditions.[3,4]
In our preceding papers, frontside nucleophilic attack was
suggested to take place in the following reactions: aryl
bis(4-methoxyphenyl) phosphates [(4-MeOPhO)2P(O)OPhZ] with
less basic pyridines,[5] aryl phenyl isothiocyanophosphates
[(YPhO)(PhO)P(O)NCS] with more basic pyridines,[6] aryl phenyl
chlorothiophosphates [(YPhO)(PhO)P(S)Cl] with anilines,[7] aryl
ethyl chlorophosphates [6; (YPhO)(EtO)P(O)Cl] and aryl ethyl
chlorothiophosphates [(YPhO)(EtO)P(S)Cl] with anilines,[8] diphe-
nyl phosphinic chloride [3; Ph2P(O)Cl] with anilines,[9] diphenyl
thiophosphinic chloride [Ph2P(S)Cl] with more basic pyridines[10]
and anilines,[11] dimethyl chlorothionophosphate [(MeO)2P(S)Cl]
with more basic anilines,[12] and diethyl chlorothionophosphate
[(EtO)2P(S)Cl] with anilines.[12] These deductions were based
R1R2PðOÞCl þ 2XC6H4NL2
MeCN
ꢀ! R1R2PðOÞNLC6H4X þ XC6H4NLþ3 Clꢀ
(1)
*
Correspondence to: H. W. Lee, Department of Chemistry, Inha University, 253
Yonghyundong, Namgu, Incheon 402-751, Korea.
E-mail: hwlee@inha.ac.kr
a
N. K. Dey, M. E. U. Hoque, C. K. Kim, B.-S. Lee, H. W. Lee
Department of Chemistry, Inha University, Incheon 402-751, Korea
J. Phys. Org. Chem. 2009, 22 425–430
Copyright ß 2008 John Wiley & Sons, Ltd.

N. K. DEY ET AL.
1: R1 ¼ R2 ¼ Me at 15.0 8C
2: R1 ¼ Me; R2 ¼ Ph at 55.0 8C
L ¼ H or D
ligands and the NBO charge on the reaction center. The
anilinolysis rate of 2 is 80 times faster than that of 3. The rate of 1
is 57 times faster than that of 2 and the rate of 1 is 4520 times
faster than that of 3. Therefore, it is clear that the rate dramatically
increases upon replacing the phenyl ligand by the methyl ligand.
X ¼ 4-MeO, 4-Me, 3-Me, H, 3-MeO, 4-Cl, 3-Cl
A plot of logkH (for the unsubstituted aniline) against the
P
Taft steric constants [ Es ¼ 0.00 (1), ꢀ2.48 (2), and ꢀ4.96 (3),
obtained with Es ¼ 0.00 (Me) and ꢀ2.48 (Ph)][23–24] according to
Eqn (3) for the three phosphinates (1, 2, and 3[9]) shows good
linearity, giving d ¼ 0.737 (r ¼ 0.9999).
RESULTS AND DISCUSSION
The observed pseudo-first-order rate constants (kobsd) were
found to follow Eqn (2) for all of the reactions under
pseudo-first-order conditions with a large excess of aniline
nucleophile.
X
log kHðDÞ ¼ d
Es þ C
(3)
kobsd ¼ k0 þ kHðDÞ½X ꢀ Anꢁ
(2)
Buncel and coworkers[25–27] reported that the second-
order rate constants, kꢀEtO, for the ethanolysis of the phos-
Me2P(O)(OPh-4-NO2),
and Ph2P(O)(OPh-4-NO2) give relative rates of 235: 69: 1. These
The k0 values were negligible (k0 ¼ 0) in acetonitrile. The
second-order rate constants (kH(D)) were determined for at least
five concentrations of anilines ([XꢀAn]). The linear plots of Eqn (2)
suggest that there is no base-catalysis or noticeable side
reactions and that the overall reaction is described by Eqn (1).
The kH and kD values are summarized in Tables 1 and 2, together
with the deuterium KIEs (kH/kD) and the Hammett rX and
phinates,
MePhP(O)(OPh-4-NO2),
are inconsistent with what would be expected when considering
P
the inductive effects of the ligands. A plot of logkꢀEtO against Es
( ¼ 0.00, ꢀ2.48, and ꢀ4.96, respectively: same values as in 1, 2 and
3) for the three phosphinates is roughly linear, giving d ¼ 0.478
(r ¼ 0.953). This leads to the conclusion that the relative
reactivities of the phosphinates are mainly determined by steric
factors. The considerably larger magnitudes of d ( ¼ 0.737) value
in the present work compared to that (d ¼ 0.478) of 4-nitrophenyl
phosphinate derivatives may be ascribed to the sizes of the
nucleophiles. In other words, the steric congestion for the
relatively larger aniline nucleophile would be much greater than
that for the ethanol nucleophile.
¨
Bronsted bX selectivity parameters. The magnitudes of the rX and
bX values for the reactions of 1 and 2 with the deuterated anilines
are somewhat smaller than those for the reactions of these
compounds with the anilines. The same tendency was observed
for the anilinolysis of diphenyl phosphinic chloride (3),[9] diphenyl
thiophosphinic chloride,[11] dimethyl and diethyl chloro-
phosphates (4 and 5),[12] and dimethyl and diethyl chlorothio-
nophosphates.[12]
As shown in Fig. 1, the natural bond order (NBO) charges,
using the B3LYP/6-311þG(d,p) level,[20] on reaction center P are
1.793 (for 1), 1.821 (for 2), and 1.844 (for 3).[9] (Cartesian
coordinates and absolute energies of 1, 2, and 3 are given in the
Supporting Information.) These values are consistent with what
would be expected when considering the inductive effects of the
The second-order rate constants, relative rates, NBO charges on
¨
reaction center P, KIEs, and Bronsted bX ( ¼ bnuc) values for the
anilinolysis of 1–7 in acetonitrile at 55.0 8C are summarized in
Table 3. This table shows that the NBO charges on P reaction
centers (or the electrophilicities of the substrates) do not seem to
play an important role in determining the reactivities of the P ¼ O
substrates, suggesting that there are great steric effects on the
anilinolysis rates of the P ¼ O systems. The large magnitudes of
P
P
P
ligands:
sI(1) ¼ ꢀ0.02,
sI(2) ¼ þ0.11, and
sI(3) ¼ þ0.24,
obtained with sI ¼ ꢀ0.01 (Me) and þ0.12 (Ph).[21] Solely con-
sidering the inductive effects of the ligands, the reactivities of the
substrates should increase in the following order: 1 < 2 < 3.
However, the sequence of the second-order rate constants of the
anilinolysis (C6H5NH2) in acetonitrile at 55.0 8C, 1[22] >> 2 >> 3, is
contrary to the expectations for the inductive effects of the
¨
the Bronsted bX ( ¼ 0.88–1.69) values for the anilinolysis of
the studied reaction systems (1–7) suggest extensive bond
formation in the TS. These values are considerably larger than
those of the following other phosphoryl transfer reactions in
which the reactions proceed by concerted mechanism: pyridi-
Table 1. Second-order rate constants (kH(D) ꢂ 10 Mꢀ1 sꢀ1) and selectivity parametersa for the reactions of dimethyl phosphinic
chloride (1) with XC6H4NH2 and XC6H4ND2 in acetonitrile at 15.0 8C
X
kH (ꢂ 10 Mꢀ1 sꢀ1
)
kD (ꢂ 10 Mꢀ1 sꢀ1
)
kH/kD
4-MeO
4-Me
3-Me
H
3-MeO
4-Cl
3-Cl
429 ꢃ 8
477 ꢃ 5
0.899 ꢃ 0.019b
0.853 ꢃ 0.027
0.823 ꢃ 0.016
0.789 ꢃ 0.025
0.759 ꢃ 0.014
0.732 ꢃ 0.024
0.703 ꢃ 0.025
163 ꢃ 3
191 ꢃ 5
70.0 ꢃ 1.2
16.1 ꢃ 0.4
7.58 ꢃ 0.08
1.97 ꢃ 0.06
0.574 ꢃ 0.015
85.1 ꢃ 0.7
20.4 ꢃ 0.4
9.99 ꢃ 0.15
2.69 ꢃ 0.03
0.816 ꢃ 0.020
ꢀrX
4.59 ꢃ 0.20 (r ¼ 0.995)
1.62 ꢃ 0.10 (r ¼ 0.990)
4.42 ꢃ 0.19 (r ¼ 0.995)
1.56 ꢃ 0.10 (r ¼ 0.990)
bX
a The s and pKa (in water) values were taken from References [17] and [18], respectively.
b Standard error { ¼ 1/kD[(DkH)2 þ (kH/kD)2 ꢂ (DkD)2]1/2 [19]
}
.
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Copyright ß 2008 John Wiley & Sons, Ltd.
J. Phys. Org. Chem. 2009, 22 425–430

DIMETHYL AND METHYL PHENYL PHOSPHINIC CHLORIDES
Table 2. Second-order rate constants (kH(D) ꢂ 102 Mꢀ1 sꢀ1) and selectivity parametersa for the reactions of methyl phenyl
phosphinic chloride (2) with XC6H4NH2 and XC6H4ND2 in acetonitrile at 55.0 8C
X
kH (ꢂ 102 Mꢀ1 sꢀ1
)
kD (ꢂ 102 Mꢀ1 sꢀ1
)
kH/kD
4-MeO
4-Me
3-Me
H
3-MeO
4-Cl
3-Cl
56.1 ꢃ 1.4
26.7 ꢃ 0.3
16.2 ꢃ 0.2
2.10 ꢃ 0.06b
2.08 ꢃ 0.06
2.04 ꢃ 0.05
2.03 ꢃ 0.06
1.76 ꢃ 0.04
1.67 ꢃ 0.05
1.62 ꢃ 0.03
33.7 ꢃ 0.9
18.4 ꢃ 0.4
13.8 ꢃ 0.4
6.24 ꢃ 0.12
3.35 ꢃ 0.09
1.46 ꢃ 0.02
9.01 ꢃ 0.10
6.80 ꢃ 0.04
3.54 ꢃ 0.05
2.01 ꢃ 0.03
0.900 ꢃ 0.010
ꢀrX
2.49 ꢃ 0.04 (r ¼ 0.999)
0.88 ꢃ 0.02 (r ¼ 0.999)
2.28 ꢃ 0.03 (r ¼ 0.999)
0.81 ꢃ 0.02 (r ¼ 0.999)
bX
a The s and pKa (in water) values were taken from References [17] and [18], respectively.
b Standard error { ¼ 1/kD[(DkH)2 þ (kH/kD)2 ꢂ (DkD)2]1/2 [19]
}
.
nium-N-phosphonate with pyridines (0.53);[28] 3-methoxy
pyridino-N-phosphate with pyridines (0.17);[29] isoquinoli-
no-N-phosphonate with pyridines (0.15);[30] phosphorylated
3-methoxypyridine with primary amines (0.19);[31] acetyl phos-
phate dianion with pyridines (0.10);[32] 4-nitrophenyl diphenyl
phosphate with phenoxides (0.53);[33] 2,4-dinitrophenyl diphenyl
phosphate with phenoxides (0.12);[34] O,O-dimethyl-O-(3-methyl-
4-nitrophenyl) phosphorothioate with phenoxides (0.49);[35]
2-aryloxy-2-oxo-1,3,2-dioxaphosphorinans with various oxya-
nions (0.32–0.48);[36] 2,4-dinitrophenyl methyl phosphate mono-
anion with primary amines (0.31);[37] and bis-2,4-dinitrophenyl
phosphate monoanion with pyridines (0.54).[38] For the studied
phosphoryl transfer reactions, the large bX values seem to be the
characteristic for the anilinolysis of phosphates and phosphinates
with the Cl leaving group. Large bX values imply extensive bond
formation in the TS or a late TS.
In our previous work on the anilinolysis of 7, a backside
nucleophilic attack concerted mechanism with a late, product-
like TS (TS II) was proposed on the basis of the large rX (and bX)
values, the large negative cross-interaction constant (rXY
¼
ꢀ1.31) and the considerably small values of the secondary
inverse KIEs (kH/kD ¼ 0.61–0.87) with deuterated aniline nucleo-
philes.[16] A concerted mechanism involving predominantly
backside nucleophilic attack in the TS (TS II) was also proposed
for the anilinolysis of 4 and 5 based on the secondary inverse
KIEs.[12] On the other hand, for the anilinolysis of 6, a concerted
Figure 1. B3LYP/6-311þG(d,p)[20] geometries and NBO charges of 1, 2, and 3[9] in the gas phase. The anilinolysis (C6H5NH2) rate ratios in acetonitrile at
55.0 8C are displayed next to the arrows.
J. Phys. Org. Chem. 2009, 22 425–430
Copyright ß 2008 John Wiley & Sons, Ltd.
www.interscience.wiley.com/journal/poc

N. K. DEY ET AL.
Table 3. Summary of the second-order rate constants, relative rate ratios, NBO charges on reaction center P, kinetic isotope effects
¨
(KIEs) and Bronsted bX values for the anilinolysis of R1R2P(O)Cl in acetonitrile at 55.0 8C
a
b
No.
R1
R2
kH (ꢂ 104 Mꢀ1 sꢀ1
)
krel
NBO charge of P
kH/kD
bX
References
This work
This work
1c
2
Me
Me
MeO
EtO
YPhO
Ph
YPhO
Me
Ph
MeO
EtO
EtO
Ph
782 00d
1380
42.8
28.2
20.0
8777
155
4.8
3.2
2.2
1.9
1
þ1.793
þ1.821
þ2.226
þ2.236
þ2.233f
þ1.844
þ2.230f
0.703–0.899
1.62–2.10
0.798–0.979
0.714–0.919
1.10–1.28
1.62
0.88
0.96
1.06
1.13
1.69
1.36
[12]
4
5
[12]
[8]
6e
3
[9]
17.3
8.91
1.42–1.82
0.71–0.77
7e
PhO
[16]
a For the reactions of the unsubstituted aniline, X ¼ H. For compounds 6 and 7, Y ¼ H.
b krel ¼ kR1,R2/kPhO,PhO (for the reactions of the unsubstituted aniline).
c The kH/kD and bX values are at 15.0 8C.
d Extrapolated value at 55.0 8C[22]
.
e The kH/kD and bX values are for the anilinolysis of unsubstituted substrate (Y ¼ H).
f Y ¼ H.
mechanism involving a partial frontside attack via a hydro-
gen-bonded four-center-type TS (TS I) was suggested for several
reasons, mainly based on the primary normal KIEs.[8]
kD ¼ 0.899) to weaker one (X ¼ 3-Cl; kH/kD ¼ 0.703), i.e., the
degree of bond formation is larger for the weaker nucleophile.
The same tendencies were observed for the anilinolysis of 4,[12]
5,[12] and 7[16] in which the proposed mechanism is SN2 with
backside nucleophilic attack via TBP-5C TS. The smaller kH/kD
value for a weaker nucleophile may coincide with greater degrees
of bond cleavage and bond making, since the negative charge on
the reaction center P should be smaller for the weaker
nucleophile. This is expected from the More O’Ferrall–Jencks
diagram.[45–46]
The anilinolysis of 2 yields the primary normal KIEs (kH/
kD ¼ 1.62–2.10), as opposed to the secondary inverse KIEs of 1
(kH/kD ¼ 0.703–0.899). This implies partial deprotonation in TS I
which involves the formation of a hydrogen bond between the Cl
leaving group and the hydrogen (deuterium) atom of the
N—H(D) moiety of the aniline. Predominantly frontside nucleo-
philic attack (four-center-type TS I over the four-membered ring
strain) was also proposed for the anilinolysis of 3,[9] mainly based
on the primary normal KIEs (kH/kD ¼ 1.42–1.82). Partial participa-
tion of four-center-type TS for the anilinolysis of 6[8] was based on
the relatively small primary normal KIEs (kH/kD ¼ 1.10–1.28).
Taking the relatively small Cl leaving group into account, these
results can be rationalized by the following steric effects: (i) the
two large phenyl ligands in 3 prohibit backside attack by the
aniline nucleophile toward the Cl leaving group, thereby resulting
in frontside attack and primary KIEs.[9] (ii) the single phenyl and
methyl ligands in 2 still prohibit the backside attack by the
aniline, thereby resulting in primary KIEs. (iii) however, the two
methyl ligands in 1 permit space available for backside
nucleophilic attack, resulting in the secondary inverse KIE. (iv)
the larger kH/kD value of 2 than that of 3, despite the larger
In the present anilinolysis studies, the KIEs for 1 are secondary
inverse (kH/kD ¼ 0.703–0.899; relatively small values), whereas the
KIEs for 2 are primary normal (kH/kD ¼ 1.62–2.10).[39] In an SN2
mechanism, a secondary inverse KIE (kH/kD < 1) is ascribed to an
increment in the vibrational frequencies of the N—L (L ¼ H or D)
in the TS II. This, in turn, results from the increased steric crowding
that occurs during the bond making process.[40–43] As a
nucleophile attacks the reaction center, the two N—L vibrations
(both bending and stretching modes) are sterically hindered and
force constants (and hence the vibrational frequencies) increase
in the TS. This results in a secondary inverse KIE in all SN2-type
reactions. The magnitudes of secondary inverse KIEs reflect the
degree of steric hindrance and hence the degree of bond
formation; the smaller the secondary inverse KIE, the greater the
extent of bond formation. By contrast, a primary normal KIE (kH/
kD > 1) indicates that partial deprotonation of the aniline
nucleophile occurs by hydrogen bonding in the rate-limiting
step.[44] More hydrogen bond formation will result in a greater
degree of deprotonation in the TS, and as a consequence, a
greater kH/kD value.
¨
Bronsted bX value ( ¼ 1.69) of 3 than that (bX ¼ 0.88) of 2, may be
due to less steric hindrance in 2 than in 3 for frontside attack. As
shown in Table 2, the degree of deprotonation in the TS I of 2 is
proportional to the nucleophilicity of the aniline. The same was
observed for the anilinolysis of 3, i.e., the stronger nucleophile
leads to the greater primary KIE. It should be noted that
the observed primary KIE is smaller than the real one due to
the formation of the hydrogen bond between only one of the
hydrogen (deuterium) atom of the two N—H(D) moieties and the
Therefore, the secondary inverse KIEs in 1, kH/kD ¼ 0.703–0.899,
imply that the steric congestion in TS II is severe due to the
backside nucleophilic attack toward the Cl leaving group and that
the extent of bond formation is great. In other words, the TS is
very late. The degree of steric crowding in the TS increases as the
nucleophile changes from a stronger nucleophile (X ¼ 4-MeO; kH/
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Copyright ß 2008 John Wiley & Sons, Ltd.
J. Phys. Org. Chem. 2009, 22 425–430

DIMETHYL AND METHYL PHENYL PHOSPHINIC CHLORIDES
—
Cl leaving group, since the other hydrogen (deuterium) atom will
give rise to the secondary inverse KIE (kH/kD < 1).
115.2, 119.2, 119.3, 129.7, 130.0, 131.8, 37.7 (C C, aromatic);
—
31P NMR (162 MHz, DMSO-d6) d 39.9–40.0 (1P, d, J ¼ 16.2 Hz,
P ¼ S); m/z, 183 (Mþ); (found: C 59.1, H 7.7, N 7.8; C9H14NOP
requires C 59.0, H 7.7, N 7.7%).
The reactivities of the P ¼ O substrates mainly depend on the
degree of steric hindrance as mentioned earlier. The reaction rate
of 3[9] (which has two phenyl ligands) is almost twice that of 7[16]
(which has two phenoxy ligands), because the phenoxy group is
bulkier than the phenyl group. The sequence of reaction rates in
Table 3 seems to be in accordance with the degree of steric
hindrance. However, the anilinolysis of 7 proceeds via backside
nucleophilic attack despite its two bulky phenoxy groups, while
the reaction of 3 proceeds via frontside attack. Furthermore, the
anilinolysis of 6[8] (which has single ethoxy and phenoxy ligands)
proceeds via backside and frontside attack. These results were
substantiated as follows. The intervening oxygen atom between
the reaction center P atom and the phenyl ring in 7 may render
enough space to permit backside attack. By contrast, the two
phenyl rings directly bonded to the reaction center in 3 inhibit
backside attack. The fast rotation of the ethyl group of 6, more or
less, sterically inhibits backside attack, thereby resulting in a
partial frontside attack.[8] Therefore, in comparison with 2 and 3,
smaller primary normal KIEs are obtained.
ðCH3ÞðC6H5ÞPð¼ OÞNHC6H4 ꢀ 4 ꢀ OCH3
Purple gummy solid, 1H NMR (400 MHz, CDCl3) d 1.77, 1.80 (3H,
ss, P-CH3), 3.72 (3H, s, OCH3), 4.96 (1H, d, J ¼ 8.4 Hz, NH), 6.73 (d,
J ¼ 8.8 Hz, 2H, phenyl), 6.96 (2H, d, J ¼ 8.8 Hz, phenyl), 7.47 (2H, t,
J ¼ 8.8 Hz, phenyl), 7.52 (1H, t, J ¼ 8.8 Hz, phenyl), 7.86 (2H, d,
J ¼ 8.8 Hz, phenyl); 13C NMR (100 MHz, CDCl3) d 16.2–17.1 (CH3, s),
55.5 (OCH3), 114.6, 115.4, 120.6, 121.2, 128.3, 131.5, 132.1, 133.1,
155.2 (C C, aromatic); 31P NMR (162 MHz, CDCl3) d 31.9 (s, 1P,
—
—
P ¼ O); m/z 261 (Mþ); (found:
C 64.0, H 6.1, N, 5.7;
C14H16NO2P requires C 64.3, H 6.2, N 5.4%).
Acknowledgements
This work was supported by a grant from the Korea Research
Foundation (KRF-2008-314-C00207).
EXPERIMENTAL
REFERENCES
Materials
[1] R. F. Hudson, Structure and Mechanism in Organophosphorus Chem-
istry, Academic Press, London, 1965, Chapter 3.
[2] A. Williams, Concerted Organic and Bio-organic Mechanisms, CRS
Press, Boca Raton, 2000, Chapter 6.
[3] C. R. Hall, T. D. Inch, Tetrahedron 1980, 36, 2059–2095.
[4] R. J. P. Corriu, J. P. Dutheil, G. F. Lanneau, J. Am. Chem. Soc. 1984, 106,
1060–1065.
[5] H. W. Lee, A. K. Guha, C. K. Kim, I. Lee, J. Org. Chem. 2002, 67, 2215–2222.
[6] K. K. Adhikary, H. W. Lee, I. Lee, Bull. Korean Chem. Soc. 2003, 24, 1135–
1140.
Dimethyl and methyl phenyl phosphinic chlorides (97%) and
HPLC-grade acetonitrile (water content < 0.005%) were used
without further purification for kinetic studies. Anilines were
redistilled or recrystallized before use. Deuterated anilines were
prepared by heating the anilines with D2O and one drop of HCl
catalyst at 85 8C for 72 h. After numerous attempts, the anilines
were more than 98% deuterated, as confirmed by 1H NMR
analysis.
[7] M. E. U. Hoque, S. Dey, A. K. Guha, C. K. Kim, B. S. Lee, H. W. Lee, J. Org.
Chem. 2007, 72, 5493–5499.
Kinetic procedure
[8] M. E. U. Hoque, N. K. Dey, C. K. Kim, B. S. Lee, H. W. Lee, Org. Biomol.
Chem. 2007, 5, 3944–3950.
Rates were measured conductometrically as described pre-
viously.[16] For the present work, the following concentrations
were used: [substrate 1] ¼ 1 ꢂ 10ꢀ4 M and [XꢀAn] ¼ 4–6 ꢂ
10ꢀ3 M; [substrate 2] ¼ 2 T 10ꢀ4 M and [XꢀAn] ¼ 1–9 ꢂ 10ꢀ2 M.
We tried at least five concentrations of anilines. Each pseudo-
first-order rate constants value (kobsd) was averaged from the
values obtained from three separate runs, which were repro-
ducible within ꢃ3%.
[9] M. E. U. Hoque, H. W. Lee, Bull. Korean Chem. Soc. 2007, 28, 936–940.
[10] M. E. U. Hoque, N. K. Dey, A. K. Guha, C. K. Kim, B. S. Lee, H. W. Lee, Bull.
Korean Chem. Soc. 2007, 28, 1797-1802.
[11] N. K. Dey, I. S. Han, H. W. Lee, Bull. Korean Chem. Soc. 2007, 28, 2003–
2008.
[12] N. K. Dey, M. E. U. Hoque, C. K. Kim, B. S. Lee, H. W. Lee, J. Phys. Org.
Chem. 2008, 21, 544–548.
[13] I. Lee, Chem. Soc. Rev. 1990, 9, 317–333.
[14] I. Lee, Adv. Phys. Org. Chem. 1992, 27, 57–117.
[15] I. Lee, H. W. Lee, Collect. Czech. Chem. Commun. 1999, 64, 1529–1550.
[16] A. K. Guha, H. W. Lee, I. Lee, J. Chem. Soc. Perkin Trans. 1999, 2, 765–
769.
[17] C. Hansch, A. Leo, R. W. Taft, Chem. Rev. 1991, 91, 165–195.
[18] A. Streitwieser, Jr, C. H. Heathcock, Introduction to Organic Chemistry
(3rd edn), Macmillan, New York, 1996, 693.
[19] T. B. Crumpler, J. H. Yoh, Chemical Computations and Errors, John
Wiley, New York, 1940, 178.
[20] W. J. Hehre, L. Random, P. V. R. Schleyer, J. A. Pople, Ab Initio Molecular
Orbital Theory, Wiley, New York, 1986, Chapter 4.
[21] M. Charton, Prog. Phys. Org. Chem. 1987, 16, 287–315.
[22] The kH value of 7.82 Mꢀ1 sꢀ1 at 55.0 8C was calculated by extrapol-
ation in the Arrhenius plot (r ¼ 0.99938) with kinetic data: kH ¼ 0.776
(0.0 8C), 1.01 (5.0 8C), and 1.61 Mꢀ1 sꢀ1 (15.0 8C).
Product analysis
Dimethyl phosphonic chloride and methyl phenyl phosphinic
chloride were reacted with excess 4-methylaniline and
4-methoxyaniline for more than 15 half-lives at 15 and 55.0 8C
in acetonitrile, respectively. The 4-methyl and 4-methoxy aniline
hydrochloride salts were separated by filtration. Analytical and
spectroscopic data of the products gave the following results:
ðCH3Þ2Pð¼ OÞNHC6H4 ꢀ 4 ꢀ CH3
[23] R. W. Taft, In Steric Effect in Organic Chemistry, (Ed.: M. S. Newman),
1
Wiley, New York, 1956, Chapter 3.
[24] A. Williams, Free Energy Relationship in Organic and Bio-organic
Chemistry, RSC, Cambridge, UK, 2003, Chapter 7.
[25] I. Onyido, K. Albright, E. Buncel, Org. Biomol. Chem. 2005, 3, 1468.
[26] E. J. Dunn, E. Buncel, Can. J. Chem. 1989, 67, 1440–1448.
Brown solid, mp 172–174 8C, H NMR (400 MHz, DMSO-d6) d
1.62–1.70 (6H, m, CH3), 2.23–2.27 (3H, d, J ¼ 16.0 Hz, CH3),
4.84–4.86 (1H, d, J ¼ 8.0 Hz, NH), 6.61–7.26 (4H, m, phenyl);
13C NMR (100 MHz, DMSO-d6) d 16.3–17.2 (CH3, s), 20.6 (CH3, s),
J. Phys. Org. Chem. 2009, 22 425–430
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N. K. DEY ET AL.
[27] E. J. Dunn, R. T. Moir, E. Buncel, J. G. Purdon, R. A. B. Bannard, Can. J.
Chem. 1990, 68, 1837–1845.
[38] A. J. Kirby, A. G. Varvoglis, J. Chem. Soc. (B) 1968, 135–141.
[39] The value of kH/kD ¼ 2.10 for the reaction of 2 with 4-methoxyaniline
is the largest one that we have ever observed in the phosphoryl
transfer reactions.
[40] J. A. Barnes, I. H. Williams, J. Chem. Soc. Chem. Commun. 1993, 1286–
1287.
[41] R. A. Poirier, Y. Wang, K. C. Westaway, J. Am. Chem. Soc. 1994, 116, 2526–
2533.
[42] I. Lee, H. J. Koh, B. S. Lee, H. W. Lee, J. Chem. Soc. Chem. Commun.
1990, 335–336.
[28] A. Williams, J. Am. Chem. Soc. 1985, 107, 6335–6339.
[29] M. T. Skoog, W. P. Jencks, J. Am. Chem. Soc. 1983, 105, 3356–3357.
[30] N. Bourne, A. Williams, J. Am. Chem. Soc. 1984, 106, 7591–7596.
[31] M. T. Skoog, W. P. Jencks, J. Am. Chem. Soc. 1984, 106, 7597–7606.
[32] D. Herschlag, W. P. Jencks, J. Am. Chem. Soc. 1989, 111, 7587–7596.
[33] S. A. Ba-Saif, M. A. Waring, A. Williams, J. Am. Chem. Soc. 1990, 112,
8115–8120.
[34] S. A. Ba-Saif, M. A. Waring, A. Williams, J. Chem. Soc. Perkin Trans. 1991,
2, 1653–1659.
[35] B. A. Gregersen, X. Lopez, D. M. York, J. Am. Chem. Soc. 2003, 125,
7178–7179.
[43] I. Lee, Chem. Soc. Rev. 1995, 24, 223–229.
[44] L. Melander, W. H. Saunders, Jr, Reaction Rates of Isotopic Molecules,
Wiley, New York, 1981, Chapter 5.
[36] S. A. Khan, A. J. Kirby, J. Chem. Soc. (B) 1970, 1172–1182.
[37] A. J. Kirby, M. J. Younas, J. Chem. Soc. (B) 1970, 1165–1172.
[45] R. A. More O’Ferrall, J. Chem. Soc. B 1970, 274–277.
[46] W. P. Jencks, Chem. Rev. 1972, 72, 705–718.
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Copyright ß 2008 John Wiley & Sons, Ltd.
J. Phys. Org. Chem. 2009, 22 425–430