Preparation and X-ray structural study of dibenziodolium derivatives

Article abstract of DOI:10.1021/acs.joc.5b00741

New experimental procedures for the preparation of dibenziodolium salts by oxidative cyclization of 2-iodobiphenyl in the presence of appropriate strong acids are described. Particularly useful is a convenient one-pot synthesis of dibenziodolium hydrogen sulfate from 2-iodobiphenyl using Oxone as an inexpensive and environmentally safe oxidant. Dibenziodolium hydrogen sulfate, bis(triflyl)imidate, or triflate can be readily converted to various other dibenziodolium derivatives (chloride, bromide, thiocyanate, azide, cyanide, phenylsulfinate) by anion exchange. Structures of key products have been established by single-crystal X-ray diffraction analysis. Particularly interesting is the X-ray structure of dibenziodolium thiocyanate, which represents the first example of a structurally characterized hypervalent iodine compound with a relatively short iodine-sulfur secondary bond distance.

Full text of DOI:10.1021/acs.joc.5b00741

Article
pubs.acs.org/joc
Preparation and X‑ray Structural Study of Dibenziodolium
Derivatives
Pavel S. Postnikov,‡ Olga A. Guselnikova,‡ Mekhman S. Yusubov,*,‡,§ Akira Yoshimura,†
Victor N. Nemykin,*,† and Viktor V. Zhdankin*,†
†Department of Chemistry and Biochemistry, University of Minnesota Duluth, Duluth, Minnesota 55812, United States
‡The Tomsk Polytechnic University, 634050 Tomsk, Russia
§The Siberian State Medical University 634050 Tomsk, Russia
S
* Supporting Information
ABSTRACT: New experimental procedures for the prepara-
tion of dibenziodolium salts by oxidative cyclization of 2-
iodobiphenyl in the presence of appropriate strong acids are
described. Particularly useful is a convenient one-pot synthesis
of dibenziodolium hydrogen sulfate from 2-iodobiphenyl using
Oxone as an inexpensive and environmentally safe oxidant.
Dibenziodolium hydrogen sulfate, bis(triflyl)imidate, or triflate
can be readily converted to various other dibenziodolium
derivatives (chloride, bromide, thiocyanate, azide, cyanide,
phenylsulfinate) by anion exchange. Structures of key products
have been established by single-crystal X-ray diffraction analysis. Particularly interesting is the X-ray structure of dibenziodolium
thiocyanate, which represents the first example of a structurally characterized hypervalent iodine compound with a relatively short
iodine−sulfur secondary bond distance.
Scheme 1. Synthetic Approaches to Dibenziodolium Salts
1. INTRODUCTION
Hypervalent iodine compounds have emerged as versatile and
environmentally benign reagents for organic synthesis.1−18
Iodonium salts belong to a particularly useful class of hypervalent
iodine derivatives due to their useful reactivity and broad
practical applications as radical initiators,2 biologically active
compounds,2 and reagents for positron emission tomography.19
Five-membered cyclic iodonium salts, derivatives of the iodolium
heterocyclic system, are especially interesting because of the
enhanced stability and applications in biological studies.2 For
example, dibenziodolium chloride (which is commonly known
under the name of diphenyleneiodonium chloride or DPI) has
found numerous applications in biological studies.20−40 In
particular, DPI is a potent hypoglycaemic agent at a dose as
low as 4 mg/kg body weight.20 DPI inhibits gluconeogenesis in
isolated rat hepatocyctes,21 causes swelling of rat liver
mitochondria,22 induces cardiomyopathy,23 induces mitochon-
drial myopathy,24,25 and inhibits the superoxide production of
neutrophils,26 as well as nitric oxide synthase.27 In modern
biochemical and pharmacological research, DPI is commonly
used as a NADPH oxidase inhibitor.28−40
Typical synthetic approaches to dibenziodolium salts are
outlined in Scheme 1. Dibenziodolium iodide 2 was originally
prepared by Mascarelli and Benati in 1909 by diazotization of
2,2′-diaminodiphenyl 1 with sodium nitrite in a hydrochloric acid
solution followed by addition of potassium iodide.41 A similar
diazotization reaction starting from 2-amino-2′-iododiphenyl 3
affords dibenziodolium as hexafluorophosphate 4 or tetrafluor-
oborate 5.42 The third method involves peracetic oxidation of 2-
iodobiphenyl 6 to an iodine(III) intermediate 7, which cyclizes to
dibenziodolium sulfate 8 in acidic solution and is finally isolated
Received: April 3, 2015
© XXXX American Chemical Society
A
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as the chloride salt 9.43 A recent modification of the approach to
dibenziodolium salts starting from 2-iodobiphenyl employs m-
CPBA instead of peracetic acid and trifluoromethanesulfonic
acid in place of sulfuric acid.44,45
Dibenziodolium salts have a relatively high thermal stability.
For example, tetrafluoroborate salt 5 melts at 239−240 °C
without decomposition; however, the X-ray structural data do
not support any aromatic character of the iodolium ring.46 On
the basis of the available literature data, it can be stated that
iodine is not capable of forming conjugated cyclic systems with
aromatic stabilization because of the large atom size and the
semi-ionic nature of the hypervalent I−C, I−N, and I−O bonds.2
Moreover, the high level computational studies using adaptive
natural density partitioning bond modeling technique (AdNDP)
reveal that the double bond between iodine atom and other
elements does not exist.47 Despite the lack of aromatic
conjugation, five-membered heterocyclic iodine compounds
have a considerably higher thermal stability as compared to
their acyclic analogues. The greater stability of five-membered
iodine−oxygen heterocycles enabled the preparation and
isolation of otherwise unstable iodine(III) derivatives with I−
OOR, I−N3, I−CF3, and other substituents.2 A computational
study on the reactivity of dibenziodolium ions with nucleophiles
was recently published by de Magalhaes, Luthi, and Togni.48
̃
̈
2. RESULTS AND DISCUSSION
In this Article, we describe experimental procedures for the
preparation of dibenziodolium hydrogen sulfate, bis(triflyl)-
imidate, and triflate by oxidative cyclization of 2-iodobiphenyl in
the presence of the corresponding strong acids. Dibenziodolium
salts of strong acids can be further converted to numerous other
dibenziodolium derivatives by anion exchange.
In the search for optimized preparation of dibenziodolium
derivatives, we have initially investigated oxidative cyclization
reactions of 2-iodobiphenyl using trifluoromethanesulfonic acid
(TfOH) and bis(trifluoromethane)sulfonimide (Tf2NH), both
of which are strong acids. Both reactions readily proceed at room
temperature affording the respective triflate 10 and bis(triflyl)-
imidate 11 in good yields (Scheme 2). The preparation of triflate
10 by a similar procedure was previously reported by Wen and
coauthors.44,45
Figure 1. Perspective view of dibenziodolium bis(triflyl)imidate 11
(pseudopolymorph 11a) with 50% ellipsoid probability. Solvent
chloroform molecule is omitted for clarity. Selected distances [Å] and
angles [deg] for 11a: I(1)−C(1) = 2.096(6), I(1)−C(8) = 2.100(6),
N(1)−S(1) = 1.595(6), N(1)−S(2) = 1.577(6), C(1)−I(1)−C(8) =
82.7(3), S(1)−N(1)−S(2) = 125.0(4).
forms dimers as a main structural motif (Figure 1). The first
coordination sphere of hypervalent iodine centers in 11a is close
to square planar geometry and has CCNO configuration. Iodine
atom has two typical (∼2.1 Å) I−C bonds and two relatively
short intermolecular contacts with bis(triflyl)imide anion. One of
these short contacts is between the iodine and oxygen O(4) atom
(∼3.04 Å), while the second is between iodine and the nitrogen
atom of anion (∼3.06 Å). The torsion angle N(1)−O(4)−
C(1)−C(8) is 11.74°, which is reasonable close to the square
planar configuration around iodine center. The hydrogen atom
of chloroform forms two hydrogen bonds with O(1) (∼2.39 Å)
and O(3) (∼2.45 Å) oxygen atoms located at two different
anions. Interconnected by the solvent molecules, dimers are
arranged along the crystallographic b-axis. The second
pseudopolymorph of 11 (pseudopolymorph 11b) crystallizes
in monoclinic unit cell and has no solvent molecules in the
structure (Figure 2). This pseudopolymorph has polymeric
nature with polymeric chains aligned along crystallographic a-
axis. Each chain consists of repeated units of two independent
dibenziodolium cations, which interact with two neighboring
bis(triflyl)imide anions each. In both independent dibenziodo-
lium cations, iodine centers were found in square-planar
geometry with very small O(8)−O(4)−C(13)−C(20) (2.62°)
and O(3)−O(7)−C(1)−C(8) (0.68°) torsion angles. Iodine
centers in both crystallographically independent molecules have
a CCOO first coordination sphere, which is different from
CCNO coordination of triclinic pseudopolymorph 11a. Again,
all covalent I−C bonds were found in the typical range. The
Scheme 2. Preparation of Dibenziodolium Triflate and
Bis(triflyl)imidate by Oxidative Cyclization of 2-
Iodobiphenyl Using m-CPBA as Oxidant
The structure of dibenziodolium bis(triflyl)imidate 11 was
established by single-crystal X-ray crystallography (Figures 1 and
2). Two different pseudopolymorphs of the product 11 were
studied by X-ray crystallography. The first pseudopolymorph
(11a) was crystallized from chloroform and has a molecule of
solvent per molecule of salt. It crystallizes in triclinic unit cell and
B
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crystalline solid by filtration of the reaction mixture after addition
of ice-cold water.
Dibenziodolium salts of strong acids 10, 11, and 13 can be
further converted to other dibenziodolium derivatives by anion
exchange. We have found that the treatment of a methanolic
solution of dibenziodolium sulfate, triflate, or bis(triflyl)imidate
in methanol with an aqueous solution of an appropriate inorganic
salt results in immediate precipitation of a new dibenziodolium
derivative. Using this simple and general procedure, we were able
to prepare various other dibenziodolium derivatives 14a−f
(Table 1).
Table 1. Preparation of Dibenziodolium Derivatives by Anion
a
Exchange
b
entry
substrate
M+X−
NaCl
product
yield (%)
1
2
13
13
13
13
10
10
10
10
10
10
11
11
11
11
11
11
14a
14b
14c
14d
14e
14f
85
80
90
75
75
85
75
93
87
80
81
90
85
82
93
NaBr
3
KSCN
NaN3
4
5
PhSO2Na
NaCN
NaCl
6
7
14a
14b
14c
14d
14e
14f
8
NaBr
Figure 2. Perspective view of dibenziodolium bis(triflyl)imidate 11
(pseudopolymorph 11b) with 50% ellipsoid probability. Selected
distances [Å] and angles [deg] for 11b: I(1)−C(1) = 2.094(3), I(1)−
C(8) = 2.102(3), I(2)−C(13) = 2.090(3), I(2)−C(20) = 2.097(3),
N(1)−S(1) = 1.585(3), N(1)−S(2) = 1.578(3), N(2)−S(3) =
1.588(3), S(4)−N(2) = 1.569(3), C(1)−I(1)−C(8) = 82.32(12),
C(13)−I(2)−C(20) = 82.39(12), S(1)−N(1)−S(2) = 123.22(17),
S(4)−N(2)−S(3) = 125.14(17).
9
KSCN
NaN3
10
11
12
13
14
15
16
PhSO2Na
NaCN
NaCl
14a
14b
14c
14d
NaBr
KSCN
NaN3
78
a
b
intermolecular short contacts, however, are significantly different
for the two crystallographically independent dibenziodolium
molecules. Indeed, the first iodine center I(1) has one short
(∼2.96 Å) and one long (∼3.12 Å) intermolecular contact to
O(3) and O(7) oxygen atoms, respectively. Similar intermo-
lecular contacts for the second iodine center, I(2), are much
closer to each other (∼2.90 and ∼2.96 Å for I(2)−O(8) and
I(2)−O(4) contacts, respectively).
At the next step, we have developed a convenient one-pot
synthesis of dibenziodolium hydrogen sulfate from 2-iodobi-
phenyl using Oxone (2KHSO5·KHSO4·K2SO4) as an inex-
pensive and environmentally safe oxidant (Scheme 3). On the
basis of the ESI−MS study of the reactions of ArI with Oxone,10
we assume that the initial oxidation of 2-iodobiphenyl 6 affords
iodine(III) intermediate 12, which cyclizes to dibenziodolium
sulfate 13 upon subsequent treatment with concentrated sulfuric
acid. The final product 13 is isolated in high yield as a pale yellow
For detailed procedures, see the Experimental Section. Yields of
isolated, analytically pure products.
This procedure affords analytically pure products 14 in
generally high yields in the form of thermally stable, white,
microcrystalline, solids. All new products were analyzed by H
1
and 13C NMR, elemental analysis, and structures of products 14c
and 14d were established by single-crystal X-ray crystallography.
X-ray structures of the dibenziodolium derivatives 14c and 14d
are shown in Figures 3 and 4. The X-ray structure of 14c is rather
unique as, for the best of our knowledge, it represents the first
proven short I−S contact. Indeed, it crystallizes in monoclinic
unit cell with iodine centers in close to square-planar geometry
(torsion N(1)−S(1)−C(8)−C(1) angle is 5.17°) and CCNS
coordination. Such geometry formed by two typical (∼2.1 Å)
covalent I−C bonds and two short intermolecular contacts
between iodine center and two thiocyanate anions. One of these
contacts (∼2.79 Å) is between iodine and nitrogen, while the
second (∼3.11 Å) is between iodine and sulfur atoms. Each
thiocyanate anion coordinated to two dibenziodolium centers,
thus forming a polymeric chain along the crystallographic a-axis.
An azido derivative of dibenziodolium, 14d, crystallizes in
monoclinic unit cell and has dimeric structure (Figure 4). Again,
iodine center was found in square-planar geometry (torsion
N(3)−N(1)−C(8)−C(1) angle is 0.98°) and CCNN coordina-
tion. The first coordination sphere of iodine atom consists of two
Scheme 3. One-Pot Synthesis of Dibenziodolium Hydrogen
Sulfate from 2-Iodobiphenyl Using Oxone as Oxidant
C
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We should emphasize that thiocyanate 14c represents the first
structurally characterized example of a hypervalent iodine
compound molecule with a short iodine−sulfur secondary
bonding. The only previously reported compounds of this type
are represented by diaryliodonium thiophenolates49 and diary-
liodonium dithiocarboxylates.50,51 The I···S distance in thio-
cyanate 14c (∼3.11 Å) is significantly shorter than the calculated
sum of van der Waals radii (3.78 Å), but longer than the sum of
the covalent radii for sulfur and iodine (2.37 Å). Several
compounds of monovalent iodine with covalent I−S bond are
known, and a single-crystal X-ray structure of triphenylmethy-
liodosulfane, Ph3CSI, with the sulfur−iodine bond length of
2.406(4) Å has been reported in the literature.52
It should be also noted that azide 14d is the first example of
isolated and structurally characterized azide derivative of an
iodonium salt. Recently, the in situ generation of azide 14d and
its use in the efficient synthesis of triazolophenanthridines have
been reported.45
3. CONCLUSIONS
In summary, we have developed new, convenient experimental
procedures for the preparation of dibenziodolium salts by
oxidative cyclization of 2-iodobiphenyl in the presence of
appropriate strong acids. Particularly useful is a one-pot synthesis
of dibenziodolium hydrogen sulfate from 2-iodobiphenyl using
Oxone as an inexpensive and environmentally safe oxidant.
Dibenziodolium hydrogen sulfate, bis(triflyl)imidate, or triflate
can be readily converted to various other dibenziodolium
derivatives (chloride, bromide, thiocyanate, azide, cyanide,
phenylsulfinate) by anion exchange. Structures of key products,
including the first known examples of stable aryliodonium
thiocyanate and aryliodonium azide, have been established by
single-crystal X-ray diffraction analysis. Particularly interesting is
the X-ray structure of thiocyanate 14c, which represents the first
structurally characterized hypervalent iodine compound with a
relatively short iodine−sulfur secondary bond distance.
Figure 3. Perspective view of dibenziodolium thiocyanate 14c with 50%
ellipsoid probability. Selected distances [Å] and angles [deg] for 14c:
I(1)−C(1) = 2.111(3), I(1)−C(8) = 2.110(4), I(1)−S(1) = 3.111(11),
S(1)−C(13) = 1.639(4), C(13)−N(1) = 1.172(5), S(1)−I(1)−C(1) =
172.84(9), S(1)−I(1)−C(8) = 94.50(10), C(1)−I(1)−C(8) =
81.49(14), S(1)−C(13)−N(1) = 178.8(4).
4. EXPERIMENTAL SECTION
General Experimental Remarks. All reactions were performed
under air atmosphere. 2-Iodobiphenyl and other reagents and solvents
were from commercial sources and used without further purification
from freshly opened containers. NMR spectra were recorded at 500
MHz (1H NMR), 470 MHz (19F NMR), and 125 MHz (13C NMR).
Chemical shifts (δ) are reported in parts per million.
Synthesis of Dibenziodolium Salts by Oxidative Cyclization
of 2-Iodobiphenyl. Preparation of Dibenziodolium Trifluorome-
thanesulfonate (10).44,45 To a stirred solution of 2-iodobiphenyl (0.56
g, 0.35 mL, 2.0 mmol) in anhydrous CH2Cl2 (6 mL) were added m-
CPBA (77%, 0.736 g, 3.2 mol) and trifluoromethanesulfonic acid (0.57
mL, 6.5 mmol). The solution was stirred for 1 h at room temperature,
and then CH2Cl2 was removed using rotary evaporation. Et2O (4 mL)
was added to the remaining solid. The mixture was stirred for 20 min,
and then filtered. The obtained solid was washed with Et2O three times
and dried in a vacuum to provide dibenziodolium trifluoromethanesul-
1
fonate 10 (0.781 g, 91% yield) as a white solid; mp 247−249 °C. H
Figure 4. Perspective view of dibenziodolium azide 14d with 50%
ellipsoid probability. Selected distances [Å] and angles [deg] for 14d:
I(1)−C(1) = 2.108(6), I(1)−C(8) = 2.104(6), N(1)−N(2) = 1.179(9),
N(2)−N(3) = 1.174(8), C(1)−I(1)−C(8) = 81.4(2), N(1)−N(2)−
N(3) = 179.1(7).
NMR (500 MHz, CD3OD): δ 8.32 (d, J = 8.0 Hz, 2H), 8.1 (d, J = 8.0 Hz,
2H), 7.84 (t, J = 8.0 Hz, 2H), 7.68 (t, J = 7.0 Hz, 2H). 13C NMR (125
MHz, CD3OD): δ 142.2, 131.18, 130.9, 130.8, 130.2, 126.9, 119.9 (q,
1JCF = 496.6 Hz). 19F (470 MHz, CD3OD): δ −80.06 (s).
Preparation of Dibenziodolium Bis(trifluoromethane)sulfonimide
(11). To a stirred solution of 2-iodobiphenyl (0.56 g, 0.35 mL, 2.0
mmol) in anhydrous CH2Cl2 (6.0 mL) were added m-CPBA (77%,
0.736 g, 3.2 mmol) and a solution of HNTf2 (1.26 g, 4.5 mmol) in
CH2Cl2 (5.0 mL). The solution was stirred for 24 h at rt, and then the
solvent was removed on a rotary evaporator. Et2O (10 mL) was added to
typical I−C covalent bonds and two almost equivalent short I−N
contacts with two azide anions (∼2.74 and ∼2.75 Å for I(1)−
N(1) and I(1)−N(3) contacts, respectively).
D
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the remaining solid. The mixture was stirred for 20 min, and then
filtered. The obtained solid was washed with Et2O three times, and dried
in a vacuum to provide dibenziodolium bis(trifluoromethane)-
sulfonimide 11 (0.84 g, 75% yield) as a pale yellow solid; mp 148−
149 °C. 1H NMR (500 MHz, CD3OD): δ 8.37 (d, J = 8.0 Hz, 2H), 8.11
(d, J = 8.5 Hz, 2H), 7.86 (t, J = 7.0 Hz, 2H), 7.71 (t, J = 6.5 Hz, 2H). 13C
NMR (125 MHz, CD3OD): δ 142.2, 131.1, 130.9, 130.8, 130.1, 126.9,
120.0 (q, 1JCF = 318.9 Hz). 19F (470 MHz, CD3OD): δ −80.66 (s). Anal.
Calcd for C14H8F6INO4S2: C, 30.07; H, 1.44; I, 22.69; N, 2.5; S, 11.47.
Found: C, 30.09; H, 1.33; I, 22.49; N, 2.46; S, 11.45. Single crystals of
product 11 suitable for X-ray crystallographic analysis were obtained by
slow evaporation of chloroform solution. For details on the crystal
structure of compound 11, see the CIF file in the Supporting
procedure afforded 0.3 g (90%) of dibenziodolium thiocyanate 14c as a
white crystalline solid; mp 239−241 °C. 1H NMR (500 MHz, DMSO-
d6): δ 8.47 (dd, J = 1.0, 7.5 Hz, 2H), 8.21 (d, J = 8.5 Hz, 2H), 7.84 (t, J =
8.0 Hz, 2H), 7.7 (t, J = 8.5 Hz, 2H). 13C NMR (125 MHz, DMSO-d6): δ
142.1, 131.5, 131.2, 130.9, 130.1, 127.5, 123.2. Anal. Calcd for
C13H8INS: C, 46.31; H, 2.39; I, 37.64; N, 4.15; S, 9.51. Found: C,
46.20; H, 2.42; I, 37.82; N, 4.12; S, 9.45. Single crystals of product 14c
suitable for X-ray crystallographic analysis were obtained by slow
evaporation of MeOH solution. For details on the crystal structure of
compound 14c, see the CIF file in the Supporting Information. Selected
crystallographic data for 14c: monoclinic, P21/c, a = 7.8592(3) Å, b =
15.6109(5) Å, c = 9.4890(6) Å, β = 90.895(6)°, V = 1164.06(9), Z = 4, R
(I > 2.0/σ(I)) = 0.0310, Rw (all) = 0.0844, CCDC 1055743.
Dibenziodolium Azide (14d). The reaction of dibenziodolium
hydrogen sulfate 13 with NaN3 (0.195 g) according to the general
procedure afforded 0.24 g (75%) of dibenziodolium azide 14d as a white
crystalline solid; mp 236 °C (with explosive decomposition). 1H NMR
(500 MHz, DMSO-d6): δ 8.43 (d, J = 7.5 Hz, 2H), 8.22 (d, J = 8.5 Hz,
2H), 7.81 (t, J = 7.5 Hz, 2H), 7.66 (t, J = 7.5 Hz, 2H). 13C NMR (125
MHz, DMSO-d6): δ 141.8, 131.2, 131.1, 130.9, 127.0, 123.4. Anal. Calcd
for C12H8IN3: C, 44.88; H, 2.51; I, 39.52; N, 13.09. Found: C, 44.73; H,
2.40; I, 39.41; N, 12.93. Single crystals of product 14d suitable for X-ray
crystallographic analysis were obtained by slow evaporation of MeOH−
water solution. For details on the crystal structure of compound 14d, see
the CIF file in the Supporting Information. Selected crystallographic
Information. Selected crystallographic data for 11a: triclinic, P1, a =
̅
10.2961(3) Å, b = 10.9654(3) Å, c = 11.4803(8) Å, α = 107.119(8)°, β =
105.292(7)°, γ = 104.881(7)°, V = 1113.45(14) Å3, Z = 4, R (I > 2.0/
σ(I)) = 0.0716, Rw (all) = 0.1959, CCDC 1055744. Selected
crystallographic data for 11b: monoclinic, P21/c, a = 11.8176(2) Å, b
= 20.2033(4) Å, c = 14.6196(10) Å, β = 93.472(7)°, V = 3484.1(3) Å3, Z
= 8, R (I > 2.0/σ(I)) = 0.0342, Rw (all) = 0.0913, CCDC 1055745.
Optimized Preparation of Dibenziodolium Hydrogen Sulfate (13)
from 2-Iodobiphenyl Using Oxone As Oxidant. 2-Iodobiphenyl 6 (2
mmol, 0.56 g, 0.35 mL) was mixed with finely powdered Oxone (1.3
mmol, 0.8 g) in a 25 mL round-bottom flask and stirred without solvent
until a homogeneous reaction mass was formed. The reaction mixture
then was cooled with ice to 5 °C, and precooled to 5 °C concentrated
H2SO4 (0.8 mL) was added by 0.2 mL portions to the center of the
reaction mixture under magnetic stirring. 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 gray
depending on the intensity of mixing. After all H2SO4 was added, the
stirring was continued for 1 h at 5 °C and then 1 h at room temperature.
The mixture of water with crushed ice (15.0 mL) then was added to the
reaction mixture. The pale yellow solid was formed immediately. Stirring
was continued until melting of all ice. The solid was filtered off, washed
by cold water (2 × 10.0 mL), and dried under vacuum. Dibenziodolium
hydrogen sulfate 13 was isolated as pale yellow crystals (0.658 g, 87%
yield); mp 260−261 °C (lit.53 >260 °C). 1H NMR (500 MHz,
CD3OD): δ 8.37 (d, J = 8.0 Hz, 2H), 8.17 (d, J = 8.5 Hz, 2H), 7.86 (t, J =
7.5 Hz, 2H), 7.70 (t, J = 7.5 Hz, 2H). 13C NMR (125 MHz, CD3OD): δ
142.1, 130.9, 130.8, 130.3, 126.8, 120.1. Anal. Calcd for C12H9IO4S·
H2O: C, 36.57; H, 2.81; I, 32.19; S, 8.13. Found: C, 36.24; H, 2.64; I,
32.07; S, 8.12.
data for 14d: triclinic, P1, a = 7.4374(6) Å, b = 8.7655(8) Å, c =
̅
9.8437(9) Å, α = 113.251(8)°, β = 92.400(7)°, γ = 111.062(8)°, V =
537.44(10) Å3, Z = 2, R (I > 2.0/σ(I)) = 0.0438, Rw (all) = 0.1225,
CCDC 1055742.
General Procedure for Preparation of Dibenziodonium Salts (14)
from Dibenziodolium Trifluoromethanesulfonate (10). An aqueous
solution of a ligand source (3 mL of solution containing 3.0 mmol of the
ligand source) was added to the solution of dibenziodolium
trifluoromethanesulfonate 10 (1.0 mmol, 0.428 g) in 10.0 mL of
methanol under vigorous stirring. An immediate formation of a white
precipitate was observed. The stirring was continued for 20 min. The
solid was filtered off, washed by cold water (2 × 5.0 mL), and dried
under vacuum.
Dibenziodolium salts 14a−d (X = Cl, Br, SCN, N3) were synthesized
from dibenziodolium trifluoromethanesulfonate according to this
procedure; see Table 1 for the yields.
Dibenziodolium Phenylsulfinate (14e). The reaction of dibenzio-
dolium trifluoromethanesulfonate 10 with sodium phenylsulfinate
(0.492 g, 3.0 mmol) according to the general procedure afforded 0.31
g (75%) of dibenziodolium sulfinate 14e as a white crystalline solid; mp
General Procedure for Preparation of Dibenziodolium Salts from
Dibenziodolium Hydrogen Sulfate (13). An aqueous solution of a
ligand source (3 mL of solution containing 3 mmol of the ligand source)
was added to the solution of dibenziodolium hydrogen sulfate 13 (1
mmol, 0.375 g) in 15.0 mL of methanol under vigorous stirring. An
immediate formation of a white precipitate was observed. Stirring was
continued for 20 min. The solid was filtered off, washed by cold water (2
× 5.0 mL), and dried under vacuum.
1
219−220 °C. H NMR (500 MHz, DMSO-d6): δ 8.40 (t, J = 8.5 Hz,
4H), 7.85 (t, J = 7.5 Hz, 2H), 7.61 (t, J = 8.0 Hz, 4H), 7.37 (t, J = 7.5 Hz,
2H), 7.29 (t, J = 7.0 Hz, 1H). 13C NMR (125 MHz, DMSO-d6): δ 142.0,
131.4, 130.9, 130.7, 128.8, 128.7, 128.4, 126.8, 124.5, 123.2. Anal. Calcd
for C18H13IO2S: C, 51.44; H, 3.12; I, 30.20; S, 7.63. Found: C, 51.06; H,
3.24; I, 30.53; S, 7.51.
Dibenziodolium Chloride (14a). The reaction of dibenziodolium
hydrogen sulfate 13 with NaCl (0.176 g, 3 mmol) according to the
general procedure afforded 0.27 g (85%) of dibenziodolium chloride
14a as a white crystalline solid; mp 345−348 °C with decomposition
(lit.: mp 293−294 °C,54 >310 °C,55 >300 °C56). 1H NMR (500 MHz,
DMSO-d6): δ 8.55 (d, J = 8.5 Hz, 2H), 8.42 (dd, J = 1.5, 8.0 Hz, 2H),
7.79 (t, J = 8.0 Hz, 2H), 7.65 (t, J = 8.0 Hz, 2H). 13C NMR (125 MHz,
DMSO-d6): δ 141.7, 131, 130.8, 130.7, 126.7, 124.5. Anal. Calcd for
C12H8ClI: C, 45.82; H, 2.56; I, 40.35; Found: C, 45.51; H, 2.65; I, 40.35.
Dibenziodolium Bromide (14b).53 The reaction of dibenziodolium
sulfate 1 with NaBr (0.357 g) according to the general procedure
afforded 0.28 g (80%) of dibenziodolium bromide 14b as a white
crystalline solid; mp 335−336 °C. 1H NMR (500 MHz, DMSO-d6): δ
8.53 (d, J = 8.0 Hz, 2H), 8.42 (dd, J = 1.5, 8.0 Hz, 2H), 7.81 (t, J = 7.0 Hz,
2H), 7.66 (d, J = 8.0 Hz, 2H). 13C NMR (125 MHz, DMSO-d6): δ 141.6,
131.1, 130.99, 130.95, 126.8, 124.1. Anal. Calcd for C12H8BrI: C, 40.15;
H, 2.25; I, 35.35. Found: C, 39.92; H, 2.27; I, 35.07.
Dibenziodolium Cyanide (14f). The reaction of dibenziodolium
trifluoromethanesulfonate 10 with sodium cyanide (0.147 g, 3.0 mmol)
according to the general procedure afforded 0.25 g (85%) of
dibenziodolium cyanide 14f as a white crystalline solid; mp 166−168
°C (with explosive decomposition). 1H NMR (500 MHz, CD3OD): δ
8.32 (d, J = 8.0 Hz, 2H), 8.16 (d, J = 8.0 Hz, 2H), 7.81 (t, J = 7.5 Hz, 2H),
7.65 (t, J = 8.0 Hz, 2H). 13C NMR (CD3OD, 125 MHz): δ 141.8, 130.6,
130.2, 133.1, 126.3, 121.5, 121.1. Anal. Calcd for C13H8IN·1/2H2O: C,
49.71; H, 2.89; I, 40.40; N, 4.46. Found: C, 50.04; H, 2.70; I, 40.86; N,
4.48. The presence of 1/2H2O in cyclic iodonium derivatives is a
common phenomenon confirmed by X-ray structural data.57
General Procedure for Preparation of Dibenziodonium Salts (14)
from Dibenziodolium Bis(trifluoromethane)sulfonimidate (11). A
solution of the ligand source (5.0 mL, containing 3.0 mmol of the ligand
source) in 7.5 mL of methanol/water mixture (2:1 v/v) was added to the
solution of dibenziodolium bis(trifluoromethane)sulfonimidate 11 (1
mmol, 0.428 g) in 7.5 mL of methanol/water mixture (2:1 v/v) under
vigorous stirring. Immediate formation of a white precipitate was
Dibenziodolium Thiocyanate (14c). The reaction of dibenziodo-
lium hydrogen sulfate 13 with KSCN (0.291 g) according to the general
E
DOI: 10.1021/acs.joc.5b00741
J. Org. Chem. XXXX, XXX, XXX−XXX

The Journal of Organic Chemistry
Article
observed. The stirring was continued for 20 min. The solid was filtered
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Dibenziodolium salts 14a−f (X = Cl, Br, SCN, N3, CN, OSOPh)
were synthesized from dibenziodolium bis(trifluoromethane)-
sulfonimidate 11 according to this procedure; see Table 1 for the yields.
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ASSOCIATED CONTENT
■
S
* Supporting Information
X-ray data for compounds 11, 14c, and 14d (CIF files) and
copies of NMR spectra for all compounds. The Supporting
Information is available free of charge on the ACS Publications
website at DOI: 10.1021/acs.joc.5b00741.
AUTHOR INFORMATION
■
Corresponding Authors
*yusubov@mail.ru
*vnemykin@d.umn.edu
*vzhdanki@d.umn.edu
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
This work was supported by a research grant from the National
Science Foundation (CHE-1262479). M.S.Y. and P.S.P. are also
thankful to the Ministry of Education and Science of Russian
Federation (project “Science” no. 4.2569.2014/K).
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