Reactions of 1-Arylbenziodoxolones with Azide Anion: Experimental and Computational Study of Substituent Effects

Article abstract of DOI:10.1002/ejoc.201701595

New substituted 1-arylbenziodoxolones were prepared and their reactivity with azide anion as a nucleophile was investigated. It was found that independent of the presence of substituents, all reactions of 1-arylbenziodoxolones proceed as nucleophilic substitution of the iodonium leaving group in the electron-deficient benziodoxolone benzene ring. The presence of bulky substituents in the ortho position of the aryl ring slows the reaction down, while the presence of a moderately electron-withdrawing bromine substituent in para position to the iodine atom in the benziodoxolone ring moderately increases the rate of substitution. The presence of a strongly electron-withdrawing nitro group in the para position to the iodine atom in the benziodoxolone ring dramatically increases the rate of substitution. These observations are in agreement with the electronic requirements for internal nucleophilic substitution in the benziodoxole ring. A quantum-chemical computational study of the possible reaction paths is in agreement with the observed effects of substituents on the reactivity of arylbenziodoxolones in this reaction.

Full text of DOI:10.1002/ejoc.201701595

A Journal of
Accepted Article
Title: Reactions of 1-Arylbenziodoxolones with Azide Anion:
Experimental and Computational Study of Substituent Effects
Authors: Mekhman Yusubov, Natalia Soldatova, Pavel Postnikov,
Rashid Valiev, Dmitry Svitich, Roza Yusubova, Akira
Yoshimura, Thomas Wirth, and Viktor Zhdankin
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To be cited as: Eur. J. Org. Chem. 10.1002/ejoc.201701595
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10.1002/ejoc.201701595
European Journal of Organic Chemistry
FULL PAPER
Reactions of 1-Arylbenziodoxolones with Azide Anion:
Experimental and Computational Study of Substituent Effects
Mekhman S. Yusubov,*[a] Natalia S. Soldatova,[a] Pavel S. Postnikov,[a] Rashid R. Valiev,[b] Dmitry Y.
Svitich,[a] Roza Y. Yusubova,[a] Akira Yoshimura,[a] Thomas Wirth,[c] and Viktor V. Zhdankin*[d]
Abstract: New substituted 1-arylbenziodoxolones were prepared
and their reactivity with azide anion nucleophile was investigated. It
was found that independent on the presence of substituents, all
reactions of 1-arylbenziodoxolones proceed as nucleophilic
substitution of the iodonium leaving group in the electron-deficient
benziodoxolone benzene ring. The presence of bulky substituents in
the ortho-position of the aryl ring slowers the reaction, while the
presence of a moderately electron-withdrawing bromine substituent
in the para-position to iodine in the benziodoxolone ring moderately
increases the rate of substitution. The presence of a strongly
electron-withdrawing nitro group in the para-position to iodine in the
benziodoxolone ring dramatically increases the rate of substitution.
These observations are in agreement with the electronic
requirements for internal nucleophilic substitution in the
benziodoxole ring. A quantum-chemical computational study of the
possible reaction paths is in agreement with the observed effects of
substituents on the reactivity of arylbenziodoxolones in this reaction.
iodonium salts bearing the anionic carboxylate moiety in ortho-
position to the iodonium group. The zwitterionic structure of 1-
arylbenziodoxolones has been confirmed by X-ray structural
analysis.[5] In particular, the observed bond distance between
the carboxylic oxygen atom and the iodonium cation is about 2.5
Å, which is indicative of a significant ionic character of this bond
as shown by resonance contributors in Figure 1.[5] The presence
of the internal I•••O interaction causes a lower electrophilic
character of the iodonium moiety and a reduced reactivity of
arylbenziodoxoles toward nucleophiles in comparison with the
noncyclic iodonium salts, Ar2I+X–. The zwitterionic structure of 1-
phenylbenziodoxolone is emphasized by the common name of
this compound known as diphenyliodonium-2-carboxylate.
Diphenyliodonium-2-carboxylate is a classical reagent that is
commonly used for the generation of benzyne under heating or
UV-irradiation.[6]
O
O
O–
I+
O
I
2.5 Å
Introduction
A
A
R
R
B
In recent years, organohypervalent iodine compounds have
emerged as versatile and environmentally benign reagents for
organic synthesis.[1] Aryliodonium salts, Ar2I+X–, belong to an
important class of organohypervalent iodine(III) derivatives with
broad applications in organic synthesis,[2] polymer chemistry,[1a]
biological studies,[1a] and positron emission tomography.[3] The
chemistry of diaryliodonium salts is a hot area of current
research. Diaryliodonium salts are especially useful reagents for
transition metal-catalyzed[4] or metal-free[2] arylations of carbon
and heteroatom nucleophiles.
B
R'
R'
Figure 1. Resonance presentation of the structure of 1-arylbenziodoxolones.
Despite
a
significant current interest in 1-substituted
as atom-transfer reagents for
benziodoxoles
trifluoromethylations, azidations and halogenations,[7] the
reactivity of 1-arylbenziodoxoles as electrophilic arylating
reagents remains essentially unexplored. Previously, we have
demonstrated that the unsubstituted 1-phenylbenziodoxolone 1
has a very low reactivity towards nucleophiles.[5b] In particular,
compound 1 is completely unreactive toward sodium azide in
aqueous acetonitrile under reflux conditions. However, the
introduction of a substituent in the benziodoxole ring A ortho to
the iodine atom, leads to a significant increase in reactivity. The
reaction of 7-methyl-1-phenylbenziodoxolone 2 with sodium
azide under similar conditions is complete in 30 min with
complete conversion to 2-azido-3 methylbenzoic acid 3 (Scheme
1).[5b]
1-Arylbenziodoxolones can be formally classified as internal
[a]
Prof. Dr. M. S. Yusubov, Ms. N. S. Soldatova, Dr. P. S. Postnikov,
Dr. D. Y. Svitich, Prof. Dr. R. Y. Yusubova, Prof. Dr. A. Yoshimura
The Tomsk Polytechnic University 634050 Tomsk (Russia)
E-mail: yusubov@mail.ru
[b]
[c]
[d]
Dr. R. Valiev
Tomsk State University 634050 Tomsk (Russia)
E-mail: valiev@phys.tsu.ru
Prof. Dr. Thomas Wirth
School of Chemistry, Cardiff University
Park Place, Cardiff, CF10 3AT (UK)
Prof. Dr. V. V. Zhdankin
Department of Chemistry and Biochemistry
University of Minnesota Duluth, MN 55812 (USA)
E-mail: vzhdanki@d.umn.edu
http://www.d.umn.edu/~vzhdanki/
Supporting information for this article is given via a link at the end of
the document.
This article is protected by copyright. All rights reserved.

10.1002/ejoc.201701595
European Journal of Organic Chemistry
FULL PAPER
O
O
The present paper is aimed at further investigation of the
role of substituents in aromatic rings A and B on the reactivity of
1-arylbenziodoxolones with nucleophiles. In particular, we
attempted to clarify the role of substituents in ring B in the
absence of the activating ortho substituent in ring A. Because of
the very low reactivity of the ortho unsubstituted benziodoxoles
(Scheme 1), we have also investigated activation of ring A by
introduction of the electron-withdrawing substituents (Br or NO2)
in the para position to iodine. Experimental observations have
been verified by computational studies of the possible reaction
paths.
NaN3, MeCN–H2O, reflux, 1.5 h
I
A
no reaction
0% conversion
Ph
1
O
O
O
OH
3
2
4
NaN3, MeCN–H2O, reflux, 0.5 h
100% conversion
1I
N3
+
PhI
5
A
Ph
6
7 CH3
CH3
2
3
90% yield
Scheme 1. Reactivity of 1-phenylbenziodoxolone
phenylbenziodoxolone 2 toward azide anion.
1 and 7-methyl-1-
Results and Discussion
Such a dramatic effect was explained by the increased
bulkiness of the aromatic ring A, forcing it to stay predominantly
in the equatorial position of the trigonal bipyramidal intermediate
5 (Scheme 3).[5b,8] In the intermediate 4 formed by the initial
Synthesis of substituted 1-arylbenziodoxolones
and reactivity studies
We have synthesized a series of unsubstituted and 5-bromo-
substituted 1-arylbenziodoxolones 7a-h starting from 2-
iodobenzoic acids 6a or 6b by a one-pot two-step procedure
outlined in Scheme 3. In the initial step, iodobenzoic acid 6 is
oxidized by Oxone in H2SO4 to the corresponding iodine(III)
species, which are converted in situ to the final products 7 by
treatment with the appropriate arene. The starting 5-bromo-2-
iodobenzoic acid 6b can be readily prepared from the
commercially available 2-iodobenzoic acid 6a by bromination
with NBS in H2SO4 at 60 oC.
–
addition of nucleophile N3 to the iodonium center, the most
electron-deficient ligands, the azide and the benzoate ring A,
occupy the axial positions. Ligand coupling, which proceeds as
the SNAr substitution reaction between the axial ligand N3 and
the aryl group in equatorial position,[8] is unlikely to occur in the
intermediate
4 due to the electron–rich character of the
equatorial phenyl ring B. However, since the equatorial positions
are roomier than the axial positions, the bulkier ortho-substituted
group would be forced to occupy the equatorial position,
switching the equilibrium toward the intermediate 5. Ligand
coupling in the intermediate 5 leads to a reductive elimination of
O
–
O
PhI and transfer of the nucleophile N3 to the ortho–substituted
O
I
OH
I
1. Oxone, H2SO4
2. arene, CH2Cl2
electron–deficient aryl group A situated in the equatorial position
(Scheme 2).
R5
R5
R4
56-74%
R1
6a: R5 = H
6b: R5 = Br
(eq)
N3
I
7a-h
R2
R3
I+
B
O–
B
7a: R1 = R2 = R4 = R5 = H, R3 = CH3
7b: R1 = R3 = R5 = H, R2 = R4 = CH3
7c: R2 = R5 = H, R1 = R3 = R4 = CH3
7d: R1 = R2 = R4 = R5 = H, R3 = Cl
7e: R5 = Br, R1 = R2 = R4 = H, R3 = CH3
7f: R5 = Br, R1 = R3 = H, R2 = R4 = CH3
7g: R5 = Br, R2 = H, R1 = R3 = R4 = CH3
7h: R5 = Br, R1 = R2 = R4 = H, R3 = Cl
NaN3
Me
O
Me
CO2Na
(ax)
A
A
4
2
pseudorotaion
Scheme 3. Synthesis of 1-arylbenziodoxolones 7a-h.
NaO2C
O
CO2Na
N3
I
N3
I
ligand coupling
5-Nitro-substituted
1-arylbenziodoxolones
7i-k
were
A
+
A
B
prepared in two steps starting from 2-iodobenzoic acid 6a
(Scheme 4). high temperature nitration/oxidation of 2-
Me
(eq)
Me
A
B
5
iodobenzoic acid with HNO3/H2SO4 produced 1-hydroxy-5-
nitrobenziodoxolone 8,[9] which was converted to products 7i-k
by treatment with the appropriate arene in the presence of triflic
acid.
(ax)
preferred conformation:
the bulkier ligand in equatorial position
Scheme 2. Explanation of enhanced reactivity of ortho-substituted
benziodoxolone 2 toward azide anion.
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10.1002/ejoc.201701595
European Journal of Organic Chemistry
FULL PAPER
O
O
4) The presence of
a
moderately electron-withdrawing
O
I
O
HNO3, H2SO4
120 oC, 1.5 h
bromine substituent in the para-position to iodine in ring A
(compounds 7e-7h) moderately increases the rate of substitution.
5) The presence of a strongly electron-withdrawing nitro
group in the para-position to iodine in ring A (compounds 7i-7k)
dramatically increases the rate of substitution. This observation
is in agreement with the electronic requirements for internal
nucleophilic substitution in ring A. Such a dramatic increase in
reactivity can also be explained by change of the mechanism to
a classical SNAr substitution via of a Meisenheimer intermediate.
arene, TfOH
43-56%
6a
R4
O2N
O2N
I
82%
OH
R1
8
7i-k
R2
R3
7i: R1 = R2 = R4 = H, R3 = CH3
7j: R1 = R3 = H, R2 = R4 = CH3
7k: R2 = H, R1 = R3 = R4 = CH3
Scheme 4. Synthesis of 1-aryl-5-nitrobenziodoxolones 7i-k.
Table 1. Reactions of compounds 7 with NaN3 in DMSO-d6 at 80 oC.[a]
Reactivity studies were performed by heating 1-
arylbenziodoxolones 7 with a NaN3 solution in DMSO-d6 to 80 oC
in an NMR tube. According to NMR, each reaction mixture
contained only products of nucleophilic substitution of iodine in
the electron-deficient aromatic ring A (Scheme 5) along with
aryliodides 10 and unreacted compounds 7. The reaction of
unsubstituted 1-phenylbenziodoxolone 1 (see Scheme 1) under
Compound 7 Conversion
[%][b,c]
Compound 7 Conversion
[%][b,c]
O
O
O
O
Br
I
CH3
61
34
26
I
these conditions (NaN3, DMSO, 80 oC,
4 h) gave 16%
7f
7a
conversion to 2-azidobenzoic acid. Conversions of substituted
arylbenziodoxolones 7 to products 9 after 4 h heating are listed
in Table 1. Representative isolated yields of the azidation
products 9b and 9c are very close to the conversion values for
the corresponding substrates 7h and 7i (Table 1). Examples of
actual NMR spectra of reaction mixtures are provided in the
supporting information.
H3C
CH3
O
O
I
O
O
I
Br
CH3
CH3
CH3
H3C
18
7g
7b
H3C
O
O
I
68 (70)d
Br
O
O
O
O
I
R4
O
I
7h
ONa
N3
R5
I
R4
NaN3, DMSO-d6
80 oC, 4 h
R1
+
Cl
R5
CH3
CH3
12
R1
R2
R3
O
H3C
O
7
10
9
R2
R3
7c
O2N
I
Products 9 were isolated as acids after acidic work-up
9a: R5 = H; 9b: R5 = Br; 9c: R5 = NO2
99 (95)e
7i
Scheme 5. Reactions of 1-arylbenziodoxolones 7 with azide anion.
CH3
O
O
O
I
O
I
41
O2N
CH3
Analysis of conversion data in Table 1 allows us to make the
following qualitative conclusions about reactivity of 1-
arylbenziodoxolones with a nucleophile:
99
7d
7j
Cl
H3C
1) Independent on the presence of substituents, all reactions
of 1-arylbenziodoxolones occur as nucleophilic substitution of
the iodonium leaving group in the electron-deficient aromatic
ring A.
2) The presence of bulky substituents in the ortho-position of
ring B (compounds 7b, 7c, 7f, and 7g) slows the reaction down.
This observation is in agreement with the general mechanism
shown in Scheme 2: a bulkier ring B favors intermediate 4, in
which internal nucleophilic substitution is unlikely.
O
O
O
I
O
O2N
Br
I
CH3
CH3
70
99
H3C
7k
7e
CH3
[a] Reactions were performed by heating 1-arylbenziodoxolones 7 with NaN3
solution in DMSO-d6 to 80 oC for 4 h. [b] Conversion was measured by NMR.
[c] Only products 9, 10 and unreacted starting material 7 were present in each
reaction mixture. [d] Isolated yield of azide 9b after 5 h heating. [e] Isolated
yield of azide 9c.
3) The presence of the electronegative chlorine substituent
in the para-position of ring
B (compounds 7d and 7h)
moderately increases the rate of substitution.
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10.1002/ejoc.201701595
European Journal of Organic Chemistry
FULL PAPER
different (Figure 2). In the case of the first reaction path, we
observed an essential formation of a bond between azide-anion
and iodine and carbon of ring A (TS1). In contrast, the transition
state of reaction path 2 (TS2) assumed the formation of a bond
between azide and carbon of ring B (Figure 2).
In order to further clarify these experimental results we
performed computational studies of the possible reaction paths
of this reaction.
I
R4
O
O–
N3
Computational evaluation
R1
+
R5
O
We calculated the reaction pathways of arylbenziodoxolones
and azide anions in DMSO at 80 C. Due to inadequate results
R2
R3
O
I
o
10
path 1
path 2
9
of COSMO[10] and PCM[11] solvation models with ionic
compounds, all calculation were carried out in the gas phase at
353 K. It should be noted that semiempirical AM1 method
demonstrated good qualitative results[12,13] and even often
R5
R4
–
+
N3
R1
R4
O
N3
O–
R2
R3
R1
comparable with the density functional results[14,15]
,
too.
+
R5
I
7
R2
R3
Therefore the geometry optimization and energy calculations
were carried out using AM1 method in Gaussian 09 software
confirmed by the comparison of geometric parameters of salts 7
with X-ray crystal data[5b] (supporting information).
12
11
Scheme 6. Possible reaction paths.
We calculated the energies for the two possible reaction
pathways (Scheme 6). In the initial step, the ion-dipole complex
(IDC) is formed (Figure 2). It should be noted that IDCs for all
The energetic profiles of reaction paths 1 and 2 for the salts
7h and 7g are presented on Figure 3. Despite the slight
differences between geometries of IDC and TS of salts 7h and
7g the energetic profiles are similar (Figure 3). The observed
regularities have been preserved for all salts 7a-k (Table 2). It
should be noted, that the provided energies were calculated
relative to IDC energies.
compounds have
a lower energy than starting materials,
associated, probably, with the formation of two close contacts of
the azide anion with carbon and iodine atoms. The geometry of
calculated complex is similar for all salts (SI); the negligible
discrepancies have been observed only for salt 7g (Figure 2).
The IDC transforms to the appropriate azides through the
transition states TS1 and TS2. According to calculation results,
the geometry of transition states for both reaction paths is
Figure 2. The calculated structures of ion-dipole complex (IDC) and transitions states (TS1 and TS2) for 7h and 7g
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10.1002/ejoc.201701595
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Figure 4. The correlation between conversion and
calculated barriers of reaction (path 1)
Figure 3. The energy profiles of reaction of 7h and 7g
The calculated energies and barriers explained the observed
selectivity of process: the differences of energies between IDC
and TS for the reaction path 1 are obviously smaller than the
barriers for reaction path 2. Moreover, the conversion of starting
materials has a good correlation with energy barriers with R =
0.96 (Figure 4). The quantum-chemical calculations confirmed
the observed effects of substituents in ring A and B. Thus, the
smallest barrier of substitution has been observed for the NO2-
substituted salts 7i-7k and the largest for 7a-d (Table 2), which
is in agreement with electron-withdrawing effects of substituents.
In contrast, the electron-donating substituents decrease the
conversion and increase the energy barriers. The effect is most
noticeable for the mesitylene derivatives 7c, 7g. In case of salt
7k the negative effect of mesitylene ring is negligible and we
An intriguing effect of the chlorine substituent in ring B has
been observed. The presence of electronegative substituent
decreases the energy barriers down to
2 kсal/mol and,
consequently, increases the reaction rate and conversion with
high selectivity (7d, 7f).
Thus, the quantum-chemical evaluation confirmed the
observed effects of substituents on the reactivity of
arylbenziodoxolones. The computed low-energy structures of
IDC and TS are not in exact agreement with the intermediates 4
and 5 shown in Scheme 2. It should be noted that the widely
adopted ligand coupling mechanism (Scheme 2) has been
developed exclusively for the noncyclic iodonium salts, Ar2IX.[8]
The observed distortion is probably explained by the presence of
a significant I•••O interaction in the benziodoxole ring forcing it to
achieved full conversion of starting materials during 240 minutes, stay in a planar configuration.
but the energy barrier was slightly larger (1 – 1.5 kсal/mol), than
salts 7i-j (Table 2).
Table 2. Relative energies (kcal/mol) of starting materials, IDC (complexes), products 9+11 and 11+12, activation energies Ea (AM1 level of theory, 353 К).
Starting
Product
Product
Ea1
Ea2
Starting
Substrates
IDC
Substrates
materials
(9+10)
(11+12)
(TS1-IDC)
(TS2-IDC)
materials
2.85
2.58
1.61
4.33
3.97
3.73
2.81
4.35
7.04
6.26
5.14
0
0
0
0
0
0
0
0
0
0
0
-86.09
-86.52
-87.48
-84.73
-89.96
-90.37
-91.26
-89.84
-96.3
-80.2
-80.8
11.8
11.96
12.74
10.61
9.43
21.42
23.85
18.59
19.52
19.92
22.26
16.88
17.01
17.7
2.85
2.58
1.61
4.33
3.97
3.73
2.81
4.35
7.04
6.26
5.14
7a
7b
7c
7d
7e
7f
7a
7b
7c
7d
7e
7f
-80.96
-78.91
-83.54
-84.12
-84.21
-83.5
9.57
10.45
7.23
7g
7h
7i
7g
7h
7i
-88.51
-89.66
-88.38
4.93
-97.27
-97.79
4.46
19.36
14.13
7j
7j
6.06
7k
7k
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10.1002/ejoc.201701595
European Journal of Organic Chemistry
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CH2Cl2 (4 mL) and ArH (1.5-3.0 mmol) were added. The magnetic stirring
of the resulting mixture was continued at room temperature for 3-5 h. The
reaction mixture was recooled to 5 oC and CH2Cl2 (3-5 mL) and then a
saturated aqueous solution of NaHCO3 were added by small portions
until pH 8.0. The organic layer was separated, and the aqueous layer
was additionally extracted with CH2Cl2 (5 mL). The organic extracts were
combined, dried with Na2SO4, the solvent was evaporated and the
crystalline product was dried in vacuum. Additional purification of
products 7a-h can be performed by crystallization from water.
Conclusions
We have demonstrated that independent on the presence of
substituents, reactions of 1-arylbenziodoxolones with azide
anion occur as nucleophilic substitution of the iodonium leaving
group in the electron-deficient benziodoxole ring. The presence
of bulky substituents in the ortho position of the aryl ring slowers
the reaction, while the presence of a moderately electron-
withdrawing bromine substituent in the para-position to iodine in
in the benziodoxole ring moderately increases the rate of
substitution. The presence of a strongly electron-withdrawing
nitro group in the para position to iodine in the benziodoxole ring
dramatically increases the rate of substitution. This observation
is in agreement with the electronic requirements for internal
nucleophilic substitution in the benziodoxole ring. A quantum-
chemical computational study of the possible reaction paths
confirmed the observed effects of substituents on the reactivity
of arylbenziodoxolones in this reaction.
1-Phenyl-1,2-benziodoxol-3-(1H)-one (1). The reaction of 2-
iodobenzoic acid 6a (248 mg, 1.0 mmol), Oxone (400 mg, 0.65 mmol),
H2SO4 (total 0.8 mL) and benzene (0.2 mL) according to the general
procedure afforded 288 mg (88%) of product 7a monohydrate, isolated
as off-white crystals; mp 221-222 °C (from water) (lit.[5b] mp 221-222 oC).
1H NMR (500 MHz, CDCl3) δ 8.38 (dd, J = 7.5, 1.5 Hz, 1H), 8.01 (dd, J =
8.0, 1.0 Hz, 2H), 7.75 (t, J = 7.5 Hz, 1H), 7.59 (t, J = 7.5 Hz, 2H), 7.53 (t,
J = 7.5 Hz, 1H), 7.37 (td, J = 7.5, 1.5 Hz, 2H), 6.74 (d, J = 8.0 Hz,
1H).13C NMR (125 MHz, CDCl3) δ 166.84, 137.26, 133.54, 133.43,
132.49, 132.44, 131.75, 130.45, 126.45, 115.73, 115.40.
1-(4-Methylphenyl)-1,2-benziodoxol-3-(1H)-one (7a). The reaction of 2-
iodobenzoic acid 6a (248 mg, 1.0 mmol), Oxone (400 mg, 0.65 mmol),
H2SO4 (total 0.8 mL) and toluene (0.2 mL) according to the general
procedure afforded 288 mg (81%) of product 7a monohydrate, isolated
as off-white crystals; mp 217-219 °C (from water); 1H NMR (CDCl3, 500
MHz): δ 8.36 (dd, J = 1.5, 7.5 Hz, 1 H), 7.88 (d, J = 8.0 Hz, 2 H), 7.53 (m,
1 H), 7.38 (m, 3 H), 6.76 (d, J = 8.5 Hz, 1 H), 2.50 (s, 3 H); 13C NMR
(CDCl3, 125 MHz): δ 166.7, 143.6, 137.2, 133.5, 133.4, 132.7, 132.6,
130.6, 126.1, 115.6, 111.1, 21.8; Anal. Calcd for C14H13IO3: C, 47.21; H,
3.68; I, 35.63. Found: C, 47.23; H, 3.59; I, 35.66.
Experimental Section
General: 2-Iodobenzoic acid, all aromatic precursors, and other reagents
and solvents were from commercial sources and used without further
purification from freshly opened containers. NMR spectra were recorded
at 300, 400 and 500 MHz (1H NMR) and 75, 100 and 125 MHz (13
NMR). Chemical shifts (δ) are reported in parts per million. Mass
spectrometric measurements were performed by the EPSRC Mass
Spectrometry Service Centre, Swansea University or by R. Jenkins/R.
Hick/S. Waller at Cardiff University. Ions were generated by the
atmospheric pressure chemical ionisation (APCI), Electrospray (ES) or
Electron Ionisation (EI).
C
1-(2,5-Dimethylphenyl)-1,2-benziodoxol-3-(1H)-one (7b). The reaction
of 2-iodobenzoic acid 6a (248 mg, 1.0 mmol), Oxone (400 mg, 0.65
mmol), H2SO4 (total 0.8 mL) and p-xylene (0.2 mL) according to the
general procedure afforded 293 mg (83%) of product 7b, isolated as
o
white crystals; mp 214-214.5 C (from ethanol-water 1:1); 1H NMR (D2O,
5-Bromo-2-iodobenzoic acid (6b). A mixture of 1.0 g (4.03 mmol) of 2-
iodobenzoic acid 6a, 900 mg (5.05 mmol) of N-bromosuccinimide and 8.0
mL H2SO4 was heated at 60 oC and stirred for 2 h. After completion of
reaction, the mixture was cooled to room temperature and poured into
ice-cold water with stirring. The light yellow solid was crystallized from
mixture ethanol - water 1:1, filtered and dried to afford the desired
500 MHz): δ 8.78 (dd, J = 1.5, 7.5 Hz, 1 H), 8.45 (s, 1H), 8.20 (t, J = 7.5
Hz, 1 H), 8.06 (s, 2 H), 7.60 (m, 1 H), 8.01 (dt, J = 1.5, 7.5 Hz, 1 H), 7.33
(d, J = 7.5 Hz, 1 H), 2.98 (s, 3 H), 2.88 (s, 3H); 13C NMR (CDCl3, 100
MHz): δ 166.7, 139.8, 139.6, 139.0, 138.9, 134.4, 133.7, 133.1, 131.3,
131.0, 124.4, 118.3, 114.4, 24.6, 20.8 ppm; HRMS (AP+) Calcd for
C15H14IO2 [M+H+] m/z 353.0039. Found: 353.0056.
o
product 6b as white crystals (1.14 g, 86.5% yield), mp 162-163 C (lit.[16]
mp 161-163 oC). 1H NMR (CDCl3, 300 MHz): δ 8.15 (d, J = 2.4 Hz, 1 H),
7.91 (d, J = 8.7 Hz, 1 H), 7.34 (dd, J = 2.4, 8.4 Hz, 1 H).
1-(2,4,6-Trimethylphenyl)-1,2-benziodoxol-3-(1H)-one
(7c).
The
reaction of 2-iodobenzoic acid 6a (248 mg, 1.0 mmol), Oxone (400 mg,
0.65 mmol), H2SO4 (total 0.8 mL) and 1,3,5-trimethylbenzene (0.15 mL,
1.1 mmol) according to the general procedure afforded 300 mg (78%) of
product 7c monohydrate, isolated as off-white crystals; mp 220-222 oC
(from ethanol-water – 1:2) (lit.[5b], mp 223-223.5 oC); 1H NMR (CD3OD,
500 MHz): δ 8.31 (dd, J =1.5, 7.5 Hz, 1 H), 7.66 (m, 1H), 7.49 (ddd, J =
1.5, 7.0, 9.0 Hz), 1H), 7.29 (s, 2H), 6.79 (d, J= 8.5 Hz, 1 H), 2.53 (s, 6H),
2.43 (s, 3 H); 13CNMR (CD3OD, 125 MHz): δ 170.2, 145.7, 145.0, 135.7,
135.4, 133.9, 132.2, 131.0, 127.5, 120.4, 114.3, 26.6, 21.4.
General procedure for preparation of 1-arylbenziodoxolones (1 and
7a-h). Following reported procedure[5b] the finely crushed, solid 2-
iodobenzoic acid 6a or 6b (1.0 mmol) was mixed with powdered Oxone
(400-430 mg, 0.65-0.7 mmol) in a 50 mL round-bottom flask and stirred
without solvent for 5 min using a magnetic stirrer until a homogeneous
reaction mass was formed. Then the reaction mixture was cooled with ice
to 5 oC and, under magnetic stirring, pre-cooled to 5 oC H2SO4 (total 0.8-
1.0 mL) was added by 0.2 mL portions to the center of the reaction
mixture. After addition of each portion of H2SO4 the reaction mass was
mechanically shaken to achieve better mixing; the color of the resulting
mass can vary from pale yellow to brown depending on the intensity of
mixing. After adding all H2SO4, the magnetic stirring was continued for 30
min at room temperature, then the mixture was cooled to 5 oC and
1-(4-Chlorophenyl)-1,2-benziodoxol-3-(1H)-one (7d). The reaction of
2-iodobenzoic acid 6a (248 mg, 1.0 mmol), Oxone (400 mg, 0.65 mmol),
H2SO4 (total 0.8 mL) and chlorobenzene (0.20 mL, 1.97 mmol) according
to the general procedure afforded 215 mg (57%) of product 7d
monohydrate, isolated as off-white crystals: mp 226-226.5 °C (from
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10.1002/ejoc.201701595
European Journal of Organic Chemistry
FULL PAPER
water); 1H NMR (400 MHz, DMSO-d6) δ 8.21 (d, J=8.4 Hz, 2H), 8.14 (d,
J=7.2 Hz, 1H), 7.70 (d, J=8.4 Hz, 2H), 7.62 (t, J=7.2 Hz, 1H), 7.54 (d,
J=7.2 Hz, 1H), 6.75 (d, J=8.4 Hz, 1H). 13C NMR (100 MHz, DMSO-d6) δ
165.7, 139.0, 137.3, 134.2, 133.6, 131.5, 131.4, 130.2, 127.4, 116.0,
115.4. Anal. Calcd for C13H10ClIO3: C, 41.46; H, 2.68; I, 33.70. Found: C,
41.56; H, 2.54; I, 33.82.
General procedure for the syntesis of 5-nitro-1-aryl-1,2-
benziodoxol-3-(1H)-ones (7 i-k)
Suspension of 5-nitro-2-iodosobenzoic acid 8 (309 mg, 1 mmol) in DCM
(8 mL) was added to trifluoromethanesulfonic acid (2 equiv, 0.18 mL) at -
30oC. Reaction mixture was stirred for 10 min, then arene (0.3 mL) was
added. The magnetic stirring of the resulting mixture was continued
overnight at room temperature. Then reaction mixture was washed with
water (3x5 mL). The organic layer was separated, the organic extracts
were combined, dried with Na2SO4, the solvent was evaporated and the
crystalline product was dried in vacuum. Additional purification of
products 7i-k can be performed by crystallization from water.
5-Bromo-1-(4-methylphenyl)-1,2-benziodoxol-3-(1H)-one (7e). The
reaction of 5-bromo-2-iodobenzoic acid 6b (327 mg, 1.0 mmol), Oxone
(400 mg, 0.65 mmol), H2SO4 (total 0.8 mL) and toluene (0.3 mL)
according to the general procedure afforded 371 mg (89%) of product 7e,
isolated as white crystals; mp 215-216 oC (from ethanol-water 1:1) 1H
NMR (300 MHz, CDCl3-CD3OD 10:1) δ 8.32 (d, J=2.4, 1H), 7.74 (d,
J=8.1 Hz, 2H), 7.40 (dd, J=2.4,8.7 Hz, 2H), 7.30 (d, J=8.4 Hz, 2H), 6.49
(d, J=8.7 Hz, 1H), 2.40 (s, 3H).13C NMR (75 MHz, CDCl3) δ 166.4, 144.2,
137.0, 136.6, 135.4, 134. 8, 132.9, 128.1, 125.8, 113.2, 109.7, 21.6.
HRMS (TOF, ES+) m/z: [M+H]+ Calcd. for C14H11O2BrI: 416.8987; Found:
416.8975.
5-Nitro-1-(4-methylphenyl)-1,2-benziodoxol-3-(1H)-one
(7i).
The
reaction of 5-nitro-2-iodosobenzoic acid 8 (309 mg, 1.0 mmol), triflic acid
(0.18 mL), and toluene (0.3 mL) according to the general procedure
afforded 7j 214 mg (56%) of product 7i, isolated as white crystals; mp
213-215 oC 1H NMR (300 MHz, CDCl3) δ 8.99 (d, J=2.7 Hz, 1H), 8.13 (dd,
J=2.7, 9.0 Hz, 1H), 7.93 (d, J=8.1 Hz, 2H), 7.43 (d, J=7.8 Hz, 2H), 6.95 (d,
J=9.0 Hz, 1H), 2.54 (s, 3H). 13C NMR (75 MHz, CDCl3-CD3OD 2:1) δ
165.8, 150.0, 144.4, 136.8, 135.4, 133.0, 128.4, 127.4, 126.4, 121.0,
110.3, 21.4. HRMS (TOF, ES+) m/z: [M+H]+ Calcd. for C14H11NO4I:
383.9733; Found: 383.9727.
5-Bromo-1-(2,5-dimethylphenyl)-1,2-benziodoxol-3-(1H)-one (7f). The
reaction of 5-bromo-2-iodobenzoic acid 6b (327 mg, 1.0 mmol), Oxone
(400 mg, 0.65 mmol), H2SO4 (total 0.8 mL) and p-xylene (0.3 mL)
according to the general procedure afforded 228 mg (53%) of product 7f,
isolated as white crystals; mp 213-214 oC (from ethanol-water 1:1). 1H
NMR (400 MHz, CDCl3) δ 8.47 (d, J=2.4, 1H), 7.83 (s, 1H), 7.47-7.43 (m,
3H), 7.50 (d, J=8.8 Hz, 1H), 2.49 (s, 3H), 2.39 (s, 3H). 13C NMR (100
MHz, CDCl3) δ 165.9, 139.7, 139.0, 136.6, 136.4, 135.9, 135.7, 134.5,
131.3, 127.5, 126.0, 118.4, 113.0, 24.7, 20.8. HRMS (TOF, AP+) m/z:
[M+H]+ Calcd. for C15H13O2BrI: 430.9144; Found: 430.9150.
5-Nitro-1-(2,5-dimethylphenyl)-1,2-benziodoxol-3-(1H)-one (7j). The
reaction of 5-nitro-2-iodosobenzoic acid 8 (309 mg, 1.0 mmol), triflic acid
(0.18ml), p-xylene (0.3 mL) according to the general procedure afforded
246 mg (62%) of product 7j, isolated as white crystals; mp 208-209 oC.
1H NMR (300 MHz, CDCl3-CD3OD 5:1) δ 8.90 (d, J=2.7 Hz, 1H), 8.06 (dd,
J=2.7, 9.0 Hz, 1H), 7.69 (s, 1H), 7.38-7.32 (m, 2H), 6.77 (d, J=8.7 Hz,
1H), 2.33 (s, 3H), 2.24 (s, 3H). 13C NMR (100 MHz, CDCl3-CD3OD 10:1)
δ 165.9, 150.1, 139.9, 139.2, 138.5, 135.8, 134.7, 131.3, 127.9, 127.6,
126.7, 119.8, 117.9, 24.1, 20.3. HRMS (TOF, ES+) m/z: [M+H]+ Calcd.
for C15H13NO4I: 397.9889; Found: 397.9880.
5-Bromo-1-(2,4,6-trimethylphenyl)-1,2-benziodoxol-3-(1H)-one (7g).
The reaction of 5-bromo-2-iodobenzoic acid 6b (327 mg, 1.0 mmol),
Oxone (400 mg, 0.65 mmol), H2SO4 (total 0.8 mL) and mesitylene (0.3
mL) according to the general procedure afforded 275 mg (62%) of
product 7g, isolated as white crystals; mp 221-223 oC (from ethanol-
water 1:1) 1H NMR (500 MHz, CDCl3 – (CD3)2CO 1:5) δ 8.35 (d, J=2.5,
1H), 7.34 (dd, J=2.5, 8.0 Hz, 1H), 7.07 (s, 2H), 6.42 (d, J=8.5 Hz, 1H),
2.45 (s, 6H), 2.34 (s, 3H). 13C NMR (75 MHz, CDCl3) δ 166.1, 144.0,
143.6, 136.4, 136.0, 130.0, 126.6, 125.9, 119.4, 112.6, 26.6, 21.5. HRMS
(TOF, ES+) m/z: [M+H]+ Calcd. for C16H15O2BrI: 444.9300; Found:
444.9303.
5-Nitro-1-(2,4,6-trimethylphenyl)-1,2-benziodoxol-3-(1H)-one
(7k).
The reaction of 5-nitro-2-iodosobenzoic acid 8 (309 mg, 1.0 mmol), triflic
acid (0.18 mL), p-xylene (0.3 mL) according to the general procedure
afforded 312 mg (76%) of product 7k, isolated as white crystals; mp 227-
228 oC. 1H NMR (300 MHz, CDCl3-CD3OD 2:1) δ 9.02 (d, J=2.7 Hz, 1H),
8.25 (dd, J=2.7, 8.7Hz, 1H) , 7.27 (s, 2H), 6.97 (d, J=8.7 Hz, 1H), 2.54 (s,
6H), 2.44 (s, 3H). 13C NMR (100 MHz, CDCl3-CD3OD 2:1) δ 167.2, 151.0,
145.4, 144.1, 137.2, 130.9, 130.7, 128.6, 127.4, 120.03, 119.98, 26.6,
21.5. HRMS (TOF, AP+) m/z: [M+H]+ Calcd. for C16H15NO4I: 412.0046;
Found: 412.0031.
5-Bromo-1-(4-chlorophenyl)-1,2-benziodoxol-3-(1H)-one (7h). The
reaction of 5-bromo-2-iodobenzoic acid 6b (327 mg, 1.0 mmol), Oxone
(400 mg, 0.65 mmol), H2SO4 (total 0.8 mL) and chlorobenzene (0.3 mL)
according to the general procedure afforded 175 mg (40%) of product 7h,
isolated as white crystals; mp 237-238 oC (from methanol-water 1:1). 1H
NMR (400 MHz, DMSO-d6) δ 8.22(d, J=8.4 Hz, 2H), 8.17 (s, 1H), 7.73-
7.70 (m, 3H), 6.66 (d, J=8.4 Hz, 1H). 13C NMR (100 MHz, DMSO-d6) δ
164.2, 138.9, 137.5, 136.4, 136.0, 133.6, 131.5, 129.5, 124.1, 114.9,
114.8. HRMS (TOF, ES+) m/z: [M+H]+ Calcd. for C13H8O2ClBrI: 436.8441,
found: 436.8448.
General procedure for the synthesis of 2-azidobenzoic acid
(9)
1-Arylbenziodoxolones 7 (0.2 mmol) and NaN3 (68 mg, 1 mmol) were
mixed with DMSO (1 mL) and the resulting mixture was heated at 80 oC.
Then the reaction mixture was diluted with water (5 mL) and washed with
CH2Cl2 (3x5 mL). Hydrochloric acid was added to the reaction mixture
until acidic pH. Obtained azide was isolated by extraction with CH2Cl2
(3x5 mL). The organic extracts were dried with Na2SO4, the solvent was
evaporated and the crystalline product 9 (as an acid) was dried in
vacuum.
5-Nitro-2-iodosobenzoic acid (8). Following a reported procedure[9]
,
nitric acid (1.5 mL) was added to 2-iodobenzoic acid 6a (1.0 g, 4.03
mmol, 1 equiv) in concentrated H2SO4 (4.5 mL). The reaction flask was
equipped with a condenser and was heated at 100 °C for 2 h. The
reaction mixture was then poured in ice-water and filtered. The resulting
solid was refluxed in water (50 mL) for 1.5 h and then filtered and
washed with acetone (10 mL) to afford product 8 (1.11 g, 3.58 mmol,
89 %). 1H NMR (300 MHz, CDCl3) δ 8.83 (d, J=2.7 Hz, 1H), 8.30 (d, J=
8.7 Hz, 1H), 8.04 (dd, J=2.7, 8.7 Hz, 1H).
5-Bromo-2-azidobenzoic acid (9b). The reaction mixture of 1-
arylbenziodoxolone 7h (87 mg, 0.2 mmol), NaN3 (68 mg, 1 mmol) and
dry DMSO (1 mL) was heated for 5 h according to the general procedure
affording 34 mg (70%) of product 9b, isolated as white crystals; mp 148-
150 oC. 1H NMR (400 MHz, CDCl3) δ 8.20 (s, 1H), 7.70 (d, J=8.4 Hz, 1H),
7.16 (d, J=8.8 Hz, 1H). 13C NMR (100 MHz, CDCl3) δ 167.48, 139.63,
137.33, 135.98, 122.31, 121.41, 117.86.
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10.1002/ejoc.201701595
European Journal of Organic Chemistry
FULL PAPER
5-Nitro-2-azidobenzoic acid (9c). The reaction mixture of 1-
arylbenziodoxolone 7i (76.6 mg, 0.2 mmol), NaN3 (68 mg, 1 mmol) and
dry DMSO (1 mL) was heated for 10 min according to the general
procedure affording 39.5 mg (95%) of product 9c, isolated as white
crystals; mp 149-150 oC. 1H NMR (400 MHz, CDCl3) δ 8.84 (d, J=2.4 Hz,
1H), 8.37 (dd, J=2.8, 8.8 Hz, 1H), 7.36 (d, J=8.8 Hz, 1H). 13C NMR (126
MHz, CDCl3- DMSO-d6 – 10:1) δ 165.6, 146.6, 144.1, 128.4, 128.1,
123.2, 120.7.
[4]
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N. R. Deprez, M. S. Sanford, Inorg. Chem. 2007, 46, 1924-1935.
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Y. Li, D. P. Hari, M. V. Vita, J. Waser, Angew. Chem., Int. Ed. 2016, 55,
4436-4454.
NMR experiment
DMSO-d6 (0.5 mL) was added to the mixture of 1-arylbenziodoxolones
7a-k (0.05 mmol) and sodium azide (0.25 mmol, 16.2 mg) in NMR tube.
The mixture was heated at 80 oC for 240 min and then NMR spectra
were recorded.
[7]
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a) K. M. Lancer, G. H. Wiegand, J. Org. Chem. 1976, 41, 3360-3364; b)
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c) E. Stridfeldt, E. Lindstedt, M. Reitti, J. Blid, P.-O. Norrby, B. Olofsson,
Chem. - Eur. J. 2017, 23, 13249-13258.
Computational Details
All calculations were carried out using Gaussian 09 revision C. 01.[17] We
used AM1 method for the optimization of equilibriums and transitions of
ground electronic state for the all considered compounds. The cartesian
coordinates of all structures are provided as supplementary material. The
geometry of transition state (TS) for all considered structures and
reaction pathways were obtained using the synchronous transit-fuided
quasi-newton (STQN) method.[18] In this method IDC was used as the
initial structure of reagents.
[9]
J. P. Brand, C. Chevalley, R. Scopelliti, J. Waser, Chem. Eur. J. 2012,
18, 5655-5666.
[10] S. Miertus, E. Scrocco, J. Tomasi, Chem. Phys. 1981, 55, 117-129.
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805.
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J. Phys. Chem. A 2002, 106, 2520-2525.
[13] M. J. S. Dewar, C. Jie, E. G. Zoebisch, Organometallics 1988, 7, 513-
521.
[14] B. S. Jursic, J. Mol. Struct.: THEOCHEM 1995, 358, 139-143.
[15] M. J. S. Dewar, E. G. Zoebisch, E. F. Healy, J. J. P. Stewart, J. Am.
Chem. Soc. 1985, 107, 3902-3909.
Acknowledgements
This work was supported by the Russian Science Foundation
(RSF-17-73-20066).
[16] M. O. Kitching, T. E. Hurst, V. Snieckus, Angew. Chem., Int. Ed. 2012,
51, 2925-2929.
[17] Gaussian 09, Revision C.01, M. J. Frisch, G. W. Trucks, H. B. Schlegel,
G. E. Scuseria, M. A. Robb, J. R. Cheeseman, G. Scalmani, V. Barone,
G. A. Petersson, H. Nakatsuji, X. Li, M. Caricato, A. Marenich, J. Bloino,
B. G. Janesko, R. Gomperts, B. Mennucci, H. P. Hratchian, J. V. Ortiz,
A. F. Izmaylov, J. L. Sonnenberg, D. Williams-Young, F. Ding, F.
Lipparini, F. Egidi, J. Goings, B. Peng, A. Petrone, T. Henderson, D.
Ranasinghe, V. G. Zakrzewski, J. Gao, N. Rega, G. Zheng, W. Liang,
M. Hada, M. Ehara, K. Toyota, R. Fukuda, J. Hasegawa, M. Ishida, T.
Nakajima, Y. Honda, O. Kitao, H. Nakai, T. Vreven, K. Throssell, J. A.
Montgomery, Jr., J. E. Peralta, F. Ogliaro, M. Bearpark, J. J. Heyd, E.
Brothers, K. N. Kudin, V. N. Staroverov, T. Keith, R. Kobayashi, J.
Normand, K. Raghavachari, A. Rendell, J. C. Burant, S. S. Iyengar, J.
Tomasi, M. Cossi, J. M. Millam, M. Klene, C. Adamo, R. Cammi, J. W.
Ochterski, R. L. Martin, K. Morokuma, O. Farkas, J. B. Foresman, D. J.
Fox, Gaussian, Inc., Wallingford CT, 2016.
Keywords: iodine • hypervalent iodine • iodonium •
benziodoxole • computational chemistry
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and Synthetic Application of Polyvalent Iodine Compounds, John Wiley
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Yoshimura, V. V. Zhdankin, Chem. Rev. 2016, 116, 3328-3435; d) T.
Dohi, Y. Kita, Curr. Org. Chem. 2016, 20, 580-615; e) S. V. Kohlhepp, T.
Gulder, Chem. Soc. Rev. 2016, 45, 6270-6288; f) R. M. Romero, T. H.
Woeste, K. Muñiz, Chem. Asian J. 2014, 9, 972-983; h) M. Ochiai, J.
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M. S. Yusubov, D. Y. Svitich, M. S. Larkina, V. V. Zhdankin, ARKIVOC
2013, (i), 364-395.
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10.1002/ejoc.201701595
European Journal of Organic Chemistry
FULL PAPER
Entry for the Table of Contents (Please choose one layout)
Layout 1:
FULL PAPER
O
I
R4
O–
Several new substituted 1-
Key Topic*
R1
+
arylbenziodoxolones were prepared
and their reactivity with azide anion
as a nucleophile was investigated
by experimental and computational
studies.
R5
N3
M. S. Yusubov,* N. S. Soldatova, P.
S. Postnikov, R. R. Valiev, D. Y.
Svitich, R. Y. Yusubova, A.
R2
R3
O
O
I
path 1
R5
A
R4
Yoshimura, T. Wirth, V. V. Zhdankin*
–
R1
+
N3
B
Page No. – Page No.
R2
R3
X
path 2
R1 - R4 = H, CH3, Cl
R5 = H, Br, NO2
Reactions of 1-
Arylbenziodoxolones with Azide
Anion: Experimental and
Computational Study of Substituent
Effects
O
N3
R4
O–
R1
+
R5
I
R2
R3
NOT OBSERVED
*reactivity of 1-arylbenziodoxolones
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