Preparation and X-ray structural study of 1-arylbenziodoxolones

Article abstract of DOI:10.1021/jo400212u

Various 1-arylbenziodoxolones can be conveniently prepared from 2-iodobenzoic acid and arenes by a one-pot procedure using Oxone (2KHSO ₅·KHSO₄·K₂SO₄) as an inexpensive and environmentally safe oxidant. This procedure is also applicable for the synthesis of the 7-methylbenziodoxolone ring system using 2-iodo-3-methylbenzoic acid as starting compound. Structures of four 1-arylbenziodoxolone derivatives were established by single-crystal X-ray diffraction analysis. An enhanced reactivity of 1-aryl-7-methylbenziodoxolones toward nucleophiles compared to unsubstituted 1-arylbenziodoxolones has been found.

Full text of DOI:10.1021/jo400212u

Article
pubs.acs.org/joc
Preparation and X‑ray Structural Study of 1‑Arylbenziodoxolones
Mekhman S. Yusubov,*,‡ Roza Y. Yusubova,‡ Victor N. Nemykin,*,† and Viktor V. Zhdankin*,†
†Department of Chemistry and Biochemistry, University of Minnesota Duluth, Duluth, Minnesota, 55812, United States
‡The Siberian State Medical University and The Tomsk Polytechnic University, 634050 Tomsk, Russia
S
* Supporting Information
ABSTRACT: Various 1-arylbenziodoxolones can be conven-
iently prepared from 2-iodobenzoic acid and arenes by a one-
pot procedure using Oxone (2KHSO5·KHSO4·K2SO4) as an
inexpensive and environmentally safe oxidant. This procedure
is also applicable for the synthesis of the 7-methylbenziodox-
olone ring system using 2-iodo-3-methylbenzoic acid as
starting compound. Structures of four 1-arylbenziodoxolone
derivatives were established by single-crystal X-ray diffraction analysis. An enhanced reactivity of 1-aryl-7-methylbenziodoxolones
toward nucleophiles compared to unsubstituted 1-arylbenziodoxolones has been found.
acid, trifluoromethanesulfonic acid, and benzene in CH2Cl2 at
80 °C followed by addition of aqueous ammonia.9 This procedure
has a limited practical value due to the use of expensive reagents
and harsh reaction conditions under elevated pressure in a sealed
flask.
In this paper, we describe an optimized general procedure for a
convenient one-pot preparation of 1-arylbenziodoxolones from
2-iodobenzoic acid and various arenes using Oxone
(2KHSO5·KHSO4·K2SO4) as an inexpensive and environ-
mentally safe oxidant. This procedure is also applicable for the
synthesis of the 7-methylbenziodoxolone ring system using
2-iodo-3-methylbenzoic acid 7 as starting compound. Structures
of key products have been established by single crystal X-ray
diffraction. We also report an enhanced reactivity of 1-aryl-7-
methylbenziodoxolones toward nucleophiles compared to
nonsubstituted 1-arylbenziodoxolones.
1. INTRODUCTION
Hypervalent iodine reagents have emerged as versatile and
environmentally benign reagents for various synthetically useful
oxidative transformations.1 Particularly useful are hypervalent
iodine five-membered heterocycles, known under collective
name “benziodoxoles”.2 The most important representatives of
this class of compounds are 2-iodoxybenzoic acid (IBX)1k,l and
2-iodosylbenzoic acid (IBA),2 which have found broad synthetic
application as common oxidants. Recently, numerous new iodine-
substituted derivatives of benziodoxoles have been prepared, and
their utility as “atom transfer” reagents has been demonstrated.2a
Especially important are the benziodoxole derivatives bearing a
C-substituent on iodine, such as 1-trifluoromethylbenziodoxoles,
which are useful reagents for electrophilic trifluoromethylation of
nucleophilic substrates,3 and alkynylbenziodoxoles, excellent
acetylene-transfer reagents.2a
Despite a significant recent interest in the carbon-substituted
benziodoxoles, the chemistry and structural features of the most
stable compounds of this structural class, 1-arylbenziodoxoles remain
almost uninvestigated. 1-Phenyl-1,2-benziodoxole-3(1H)-one 2a,
commonly known under the names of 1-phenylbenziodoxolone or
diphenyliodonium-2-carboxylate, is the most important representa-
tive of arylbenziodoxoles. 1-Phenylbenziodoxolone 2a is a classical
reagent that is commonly used for the generation of benzyne under
heating or UV irradiation.4,5 It has also found synthetic application for
the preparation of o-substituted benzoic acids, which serve as
important intermediate products in the synthesis of various
biologically active compounds.6 Phenylbenziodoxolone 2a is
commercially available or can be prepared by the oxidation of
2-iodobenzoic acid 1 with potassium persulfate followed by addition
of benzene according to the procedure published in Organic Syntheses
(Scheme 1).4 The original procedure was first reported in 1960 by
Beringer and Lillien,7 and it has also been used for the synthesis of
substituted phenylbenziodoxoles 3−6.5d,e,8
2. RESULTS AND DISCUSSION
We have developed an optimized general procedure for one-pot
preparation of 1-arylbenziodoxolones on the basis of a modified
procedure for preparation of product 1a published in Organic
Syntheses.4 The key differences consist of the use of Oxone instead of
potassium persulfate at the first step and a modified product isolation
procedure using NaHCO3 as a base. These modifications result in an
increased yield of product 1a (up to 92% of crude product or 88%
after additional recrystallization from water) and allow facile
preparation of various new 1-arylbenziodoxolones (Table 1).
This procedure affords analytically pure products 2 in
generally high yields in the form of thermally stable, white,
microcrystalline solids. Lower yields (40−62%) are observed in
the case of sterically hindered substrates (entries 8, 14, and 15).
In the reactions of 2-iodo-3-methylbenzoic acid 7, a significant
darkening at the end of reaction was observed that required
More recently, Merritt and Olofsson reported a modified
procedure for the synthesis of phenylbenziodoxole in 66% yield by
a one-pot reaction of 2-iodobenzoic acid with m-chloroperoxybenzoic
Received: February 4, 2013
Published: March 12, 2013
© 2013 American Chemical Society
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Scheme 1. Known 1-Arylbenziodoxolones
additional treatment of the reaction mixture with activated carbon.
nucleophiles proceed only at temperatures above 80 °C and require
the presence of copper catalysts.6c The low reactivity of
arylbenziodoxolones compared to the noncyclic diaryliodonium
salts1h can be explained by a significant stabilization of the cyclic
halonium ions due to the strong intramolecular hypervalent
halogen−oxygen interaction12 in the benziodoxole ring. It would
be interesting to compare the reactivity of 1-phenylbenziodoxolone
2a with 1-phenyl-7-methylbenziodoxolone 2n, which has a methyl
group in the ortho position to the phenyliodonium group. It has
been previously observed that the o-methyl-substituted aromatic
ring in a nonsymmetrical diaryliodonium salt shows enhanced
reactivity toward nucleophiles (the so-called “ortho-effect”), which is
explained by the effect of steric factors on configuration of the
reaction intermediate.13
We have investigated the reactions of benziodoxolones 2a and 2n
with sodium azide in aqueous acetonitrile under reflux conditions
(Scheme 2). While compound 2a was inert under these conditions
after 1.5 h, the ortho-substituted 1-phenyl-7-methylbenziodoxolone
2n was completely converted to the azide 8 and iodobenzene just in
30 min. The product of substitution 8 was isolated as an off-white
microcrystalline precipitate from the aqueous solution after removal
of PhI and addition of HCl. Furthermore, 1-phenyl-7-methyl-
benziodoxolone 2n demonstrated high reactivity even toward such a
poor nucleophile as water. Refluxing the solution of compound
2n in aqueous acetonitrile for 1 h resulted in complete conversion to
3-methylsalicylic acid 9 and iodobenzene after 1 h (Scheme 2).
We assume that the dramatic enhancement of reactivity
observed in the reactions of 1-phenyl-7-methylbenziodoxolone
2n with nucleophiles is explained by the increased bulkiness of
the aromatic ligand, forcing it to stay predominantly in the
equatorial position of the trigonal bipyramidal intermediate
(Scheme 3).13 In the trigonal bipyramidal intermediate A formed
by the initial addition of nucleophile X:− to the iodonium center,
the most electron-deficient ligands, X and the benzoate group,
occupy the axial positions. Ligand coupling, which proceeds
as the SNAr substitution reaction between the axial ligand X and
the aryl group in equatorial position,13 is unlikely to occur in the
intermediate A because of the electron-rich character of the
equatorial phenyl ligand. However, since the equatorial positions are
roomier than the axial positions, it is reasonable that a bulkier ortho-
substituted group would be forced to occupy the equatorial position,
switching the equilibrium toward the intermediate B. Ligand
coupling in the intermediate B leads to a reductive elimination of
PhI and transfer of the nucleophile to the ortho-substituted electron-
deficient aryl group situated in the equatorial position (Scheme 3).
1
All new products were analyzed by H and 13C NMR, elemental
analysis, and structures of products 2b, 2g, 2n, and 2o were
established by single-crystal X-ray crystallography (Figure 1).
X-ray data of products 2b, 2g, 2n, and 2o demonstrate the
presence of complex intra- and/or intermolecular interactions typical
for hypervalent iodine compounds. All products were crystallized
using water (water/methanol in the case of 2o) as a solvent. In
compounds 2g and 2n, solvent molecules were not observed in the
unit cells, while water or water and methanol molecules were
observed in the unit cells of products 2b and 2o. The following
similarities were observed in the crystal structures of compounds 2b,
2g, 2n, and 2o: (i) iodine(III) centers have classic distorted (O−I−C
angles varies between 162.57° and 169.19°) T-shape conformation;
(ii) iodine−carbon bond length in the iodine−arylcarboxylate
fragment (2.130−2.152 Å) is always longer compared to the corres-
ponding iodine−carbon bond length in the iodine−aryl fragment
(2.096−2.126 Å); (iii) iodine centers are involved in the formation of
the five−membered C−I−O−C−C benziodoxole ring (iodine−
oxygen bond length varies between 2.482 and 2.559 Å); (iv) iodine
centers form secondary intermolecular contacts with oxygen atoms of
either solvent molecules or oxygen atoms of carboxylic group in
neighboring molecules; (v) C−I−C angles in compounds with less
sterically demanding arylcarboxylate substituents (compounds 2b,
92.4° and 2g, 93.4°) are close to that observed earlier in parent
1-phenylbenziodoxole 1a (95.2°),10 while the same angle in more
sterically crowded compounds 2n and 2o are significantly larger
(99.38° and 100.74°, respectively); (vi) degree of coplanarity of the
C−I−O−C−C fragment and the parent benzene ring depends on
the steric properties of the arylcarboxylate part of the molecule.
Indeed, in compounds 2b and 2g, which are derived from
unsubstituted iodosylbenzoic acid, the C−C−C(O)−O torsion
angles are close to zero (6.11° and 2.12°, respectively) resulting in a
nearly coplanar arrangement of the iodine−containing five−
membered and parent six−membered fragments. Introduction of
methyl group in the position 3 of iodosylbenzoic acid fragment, on
the other hand, results in significant distortion of C−C−C(O)−O
torsion angle (11.81° for 2n and 18.51° for 2o) and thus deviation of
the C−I−O−C−C fragment from plane of the six-membered
benzene ring.
It was previously established that the reactions of 1-
phenylbenziodoxolone 2a with nucleophiles (e.g., amines)
proceed exclusively in the benziodoxolone ring with substitution
of PhI and formation of the respective o-substituted benzoic
acids.6 This reactivity pattern is in agreement with general
regioselectivity of the reactions of nonsymmetrical iodonium salts
with nucleophiles, in which substitution occurs predominantly in
the more electron-deficient aromatic ring.11 It is also known from
the literature that the reactions of 1-phenylbenziodoxolone 2a with
3. CONCLUSIONS
In summary, we have developed a convenient procedure for the
preparation of various 1-arylbenziodoxolones from 2-iodobenzoic
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a
Table 1. Preparation of 1-Arylbenziodoxolones 1a−o
a
b
For detailed procedures, see the Experimental Section Yields of recrystallized, analytically pure products.
acid and arenes by a one-pot procedure using Oxone as an
inexpensive and environmentally safe oxidant. This procedure is
also applicable for the synthesis of the 7-methylbenziodoxolone
ring system starting from 2-iodo-3-methylbenzoic acid 7.
Structures of four 1-arylbenziodoxole derivatives were established
by single-crystal X-ray diffraction analysis. An enhanced reactivity
of 1-aryl-7-methylbenziodoxolones toward nucleophiles has been
found and rationalized similarly to the “ortho-effect” previously
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Scheme 3. Explanation of Enhanced Reactivity of Ortho-
Substituted Benziodoxolone 2n
Figure 1. Perspective view of 1-arylbenziodoxolones 2b, 2g, 2n, and 2o
with 50% ellipsoid probability. Selected distances (Å) and angles (deg)
for 2b (two independent molecules in the unit cell): I(1)−C(1)
2.126(7), 2.135(6); I(1)−O(1) 2.518(5), 2.509(5); I(1)−C(8)
2.115(5), 2.113(6); C(8)−I(1)−O(1) 164.01(19), 165.2(2); C(1)−
I(1)−C(8) 91.3(2), 93.5(3). 2g: I(1)−C(1) 2.130(10); I(1)−O(1)
2.491(7); I(1)−C(8) 2.096(10); C(8)−I(1)−O(1) 166.8(3); C(1)−
I(1)−C(8) 93.4(4). 2n (three independent molecules in the unit cell):
I(1)−C(1) 2.151(4), 2.151(4), 2.154(4); I(1)−O(1) 2.494(3),
2.482(3), 2.471(3); I(1)−C(9) 2.123(4), 2.127(4), 2.129(4); C(9)−
I(1)−O(1) 169.60(16), 167.52(15), 170.46(17); C(1)−I(1)−C(9)
99.90(17), 98.10(17), 100.13(17). 2o (four independent molecules in
the unit cell): I(1)−C(1) 2.136(5), 2.126(4), 2.141(5), 2.142(4); I(1)−
O(1) 2.566(3), 2.595(4), 2.503(4), 2.571(3); I(1)−C(9) 2.117(4),
2.118(5), 2.122(5),2.120(4); C(9)−I(1)−O(1) 160.24(14),
162.98(15), 164.87(16), 162.19(4); C(1)−I(1)−C(9) 100.05(16),
99.76(18), 101.74(18), 101.40(16).
in a 100 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 °C and, under magnetic stirring,
precooled to 5 °C. H2SO4 (total 3.2 mL) was added via syringe 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 all H2SO4 was added, the
magnetic stirring was continued for 30 min at room temperature, the mixture
was cooled to 5 °C, and CH2Cl2 (4 mL) and ArH (4.0−11.0 mmol) were
added. The magnetic stirring of the resulting mixture was continued at 5 °C
for 1 h and then at room temperature for 2 h. The reaction mixture was
recooled to 5 °CandCH2Cl2 (10 mL), and then a saturated aqueous solution
of NaHCO3 was added in small portions until pH 8.0. The organic layer was
separated, and the aqueous layer was additionally extracted with CH2Cl2
(10 mL). The organic extracts were combined and dried with Na2SO4, the
solvent was evaporated, and the crystalline product was dried in vacuum.
Additional purification of products 2 can be performed by crystallization from
water.
Scheme 2. Reactions of 1-Phenylbenziodoxolones with
Nucleophiles
1-Phenyl-1H-1λ3-benzo[b]iodo-3(2H)-one (2a). The reaction of
2-iodobenzoic acid 1 (1.00 g, 4.033 mmol), Oxone (1.6 g, 2.6 mmol),
H2SO4 (total 3.2 mL), and benzene (0.8 mL) according to the general
procedure afforded 1.27 g (92%) of crude product 2a, isolated as an off-
white crystalline solid, which was further purified by crystallization from
water to give 1.21 g (88%) of 1-phenyl-1H-1λ3-benzo[b]iodo-3(2H)-
one monohydrate: mp 221−222 °C (from water) (lit.5a mp 220 °C of
monohydrate); 1H NMR (CDCl3, 500 MHz) δ 8.36 (dd, J = 1.5, 7.5 Hz,
1 H), 7.99 (dd, J = 1.0, 7.5 Hz, 2 H), 7.73 (m, 1 H), 7.57 (m, 2 H), 7.52
(m, 1 H), 7.35 (ddd, J = 1.5, 7.0, 8.5 Hz, 1 H), 6.72 (d, J = 8.5 Hz, 1 H);
13C NMR (CDCl3, 125 MHz) δ 166.8, 137.2, 133.5, 133.4, 132.5, 132.4,
131.7, 130.4, 126.4, 115.7, 115.4.
1-(4-Methylphenyl)-1H-1λ3-benzo[b]iodo-3(2H)-one (2b).
The reaction of 2-iodobenzoic acid 1 (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
2b 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. Single crystals of product 2b suitable for X-ray
crystallographic analysis were obtained by slow crystallization from
water. For details on crystal structure of compound 2b see the CIF file in
Supporting Information.
observed in the reactions of nonsymmetrical diaryliodonium salts
with nucleophiles.
4. EXPERIMENTAL SECTION
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 500 MHz (1H NMR) and 125 MHz (13C NMR). Chemical
shifts (δ) are reported in parts per million.
General Procedure for Preparation of 1-Arylbenziodoxo-
lones (2a−o). The finely crushed, solid 2-iodobenzoic acid 1 or 7
(4.033 mmol) was mixed with powdered Oxone (1.5−1.6 g, 2.4−2.6 mmol)
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1-(4-Propylphenyl)-1H-1λ3-benzo[b]iodo-3(2H)-one (2c). The
reaction of 2-iodobenzoic acid 1 (248 mg, 1.0 mmol), Oxone (400 mg,
0.65 mmol), H2SO4 (total 0.8 mL), and propylbenzene (0.2 mL)
according to the general procedure afforded 353 mg (94%) of product
2c·1/2H2O, isolated as off-white crystals: mp 180−182 °C (from water);
1H NMR (CD3OD, 500 MHz) δ 8.24 (dd, J = 1.5, 7.5 Hz, 1 H), 8.03
(d, J = 8.0 Hz, 2 H), 7.60 (m, 1 H), 7.47 (m, 3 H), 6.84 (dd, J = 1.0,
8.5 Hz, 1 H), 2.75 (t, J = 7.5 Hz, 2 H), 1.72 (sep, J = 7.5 Hz, 2 H), 1.00
(t, J = 7.5 Hz, 3 H); 13C NMR (CD3OD, 125 MHz) δ 170.1, 149.8,
138.8, 135.3, 134.6, 133.9, 133.4, 131.9, 128.8, 116.3, 112.1, 39.0, 25.6,
14.2. Anal. Calcd for C16H15IO2·1/2H2O: C, 51.22; H, 4.53; I, 33.82.
Found: C, 51.07; H, 4.24; I, 33.90.
color to dark cherry was observed. After that, 5.0 mL of CH2Cl2 was
added, and the organic layer was separated from aqueous acidic solution.
The treatment of organic layer according to general procedure afforded
156 mg (40%) of product 2h·1/2H2O, isolated as off-white crystals: mp
1
221.5−222.5 °C (from water); H NMR (CD3OD, 500 MHz) δ 8.31
(dd, J = 1.5, 7.5 Hz, 1 H), 7.66 (ddd, J = 0.5, 1.0, 7.5 Hz, 1 H), 7.48 (ddd,
J = 1.0, 1.5, 6.5 Hz 1 H), 7.37 (s, 1H), 6.80 (dd, J = 1.0, 8.5 Hz, 1 H), 2.51
(s, 6 H), 2.41 (s, 6 H); 13C NMR (CD3OD, 125 MHz) δ 170.2, 140.4,
138.0, 137.7, 135.7, 135.4, 133.8, 132.1, 128.0, 126.6, 114.4, 24.1, 21.6.
Anal. Calcd for C17H17IO2•1/2H2O: C, 52.46; H, 4.66; I, 32.60. Found:
C, 52.43; H, 4.68; I, 32.85.
1-(4-Chlorophenyl)-1H-1λ3-benzo[b]iodo-3(2H)-one (2i). The
reaction of 2-iodobenzoic acid 1 (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 2i monohydrate, isolated as off-white crystals: mp 226−226.5 °C
(from water); 1H NMR (CD3OD, 500 MHz) δ 8.26 (dd, J = 1.5, 8.0 Hz, 1
H), 8.13 (d, J = 8.5 Hz, 2 H), 7.65 (m, 3 H), 7.53 (m, 1 H), 6.89
(d, J = 8.0 Hz, 1 H); 13C NMR (CDCl3, 125 MHz) 167.3, 139.1, 138.8,
133.5, 132.4, 132.0, 130.4, 126.7, 116.2, 113.8. Anal. Calcd for C13H10ClIO3:
C, 41.46; H, 2.68; I, 33.70. Found: C, 41.56; H, 2.54; I, 33.82.
1-(4-tert-Butylphenyl)-1H-1λ3-benzo[b]iodo-3(2H)-one (2d).
The reaction of 2-iodobenzoic acid 1 (248 mg, 1.0 mmol), Oxone
(400 mg, 0.65 mmol), H2SO4 (total 0.8 mL), and tert-butylbenzene
(0.2 mL) according to the general procedure afforded 312 mg (82%) of
product 2d, isolated as off-white crystals: mp 233.5−234 °C (from
water) (lit.5d mp 248 °C); 1H NMR (CD3OD, 500 MHz) δ 8.27 (dd, J =
1.5, 7.5 Hz, 1 H), 8.05 (d, J = 8.5 Hz, 2 H), 7.71 (d, J = 8.5 Hz, 2 H), 7.63
(ddd, J = 1.0, 7.5 Hz, 1 H), 7.50 (m, 1 H), 6.87 (dd, J = 1.0, 8.5 Hz, 1 H),
1.41 (s, 9 H); 13C NMR (CD3OD, 125 MHz) δ 170.0, 158.3, 138.6,
134.8, 133,5, 131.91, 131.90, 131.89, 130.4, 128.8, 116.3, 112.1, 36.4,
31.6. Anal. Calcd for C17H17IO2: C, 53.70; H, 4.51; I, 33.38. Found: C,
53.85; H, 4.46; I, 33.43.
1-(4-Bromophenyl)-1H-1λ3-benzo[b]iodo-3(2H)-one (2j). The
reaction of 2-iodobenzoic acid 1 (248 mg, 1.0 mmol), Oxone (400 mg,
0.65 mmol), H2SO4 (total 0.8 mL), and bromobenzene (0. Twenty mL,
1.91 mmol) according to the general procedure afforded 350 mg (83%) of
product 2j monohydrate, isolated as off-white crystals: mp 222−222.5 °C
(from water); 1H NMR (CD3OD, 500 MHz) δ 8.25 (dd, J = 1.5, 7.5 Hz,
1 H), 8.03 (d, J = 8.5 Hz, 2 H), 7.80 (d, J = 8.5 Hz, 2 H), 7.62
(m, 1 H), 7.51 (m, 1 H), 6.88 (d, J = 8.5 Hz, 1 H); 13C NMR (CDCl3, 125
MHz) 170.0, 140.4, 136.3, 135.5, 134.6, 133.4, 132.0, 129.0, 128.8, 116.3,
114.7. Anal. Calcd for C13H10BrIO3: C, 37.09; H, 2.39; I, 30.14. Found: C,
37.02; H, 2.24; I, 29.92.
1-(4-Octylphenyl)-1H-1λ3-benzo[b]iodo-3(2H)-one (2e). The
reaction of 2-iodobenzoic acid 1 (248 mg, 1.0 mmol), Oxone (400 mg,
0.65 mmol), H2SO4 (total 0.8 mL), and octylbenzene (0.25 mL, 1.13
mmol) according to the general procedure afforded 396 mg (89%) of
product 2e·1/2H2O, isolated as off-white crystals: mp 123−124 °C
(from water); 1H NMR (CD3OD, 500 MHz) δ 8.27 (d, J = 7.5 Hz, 1 H),
8.03 (d, J = 6.5 Hz, 2 H), 7.64 (m,1 H), 7.49 (m, 3 H), 6.86 (d, J = 8.5 Hz,
1 H), 2.78 (t, J = 7.5 Hz, 2 H), 1.70 (m, 2 H),1.34 (m, 10H), 0.91 (t, J =
7.5 Hz, 3 H); 13C NMR (CD3OD, 125 MHz) δ 170.2, 150.2, 138.8,
135.4, 134.6, 133.4, 133.3, 131.9, 128.9, 116.3, 112.0, 37.0, 33.2, 32.5,
30.7, 30.54, 30.49, 23.9, 14.6. Anal. Calcd for C21H25IO2·1/2H2O: C,
56.63; H, 5.90; I, 28.49. Found: C, 56.30; H, 6.11; I, 27.85.
1-(4-Iodophenyl)-1H-1λ3-benzo[b]iodo-3(2H)-one (2k). The
reaction of 2-iodobenzoic acid 1 (248 mg, 1.0 mmol), Oxone (400 mg,
0.65 mmol), H2SO4 (total 0.8 mL), and iodobenzene (0. Fifteen mL,
1.35 mmol) according to the general procedure afforded 428 mg (91%)
of product 2k, isolated as off-white crystals: mp 224−225.5 °C (from
water); 1H NMR (CD3OD, 500 MHz) δ 8.27 (dd, J = 1.5, 7.5 Hz, 1 H),
8.02 (d, J = 8.5 Hz, 2 H), 7.88 (d, J = 8.5 Hz, 2 H), 7.65 (m, 1 H), 7.54
(ddd, J = 1.5, 6.0, 8.5 Hz, 1 H), 6.90 (d, J = 8.5 Hz, 1 H); 13C NMR
(CD3OD, 125 MHz) 170.2, 142.4, 140.2, 135.6, 134.4, 133.4, 132.0,
129.1, 116.3, 115.4, 101.2. Anal. Calcd for C13H8I2O2: C, 34.70; H, 1.79;
I, 56.40. Found: C, 34.76; H, 1.59; I, 56.67.
1-(4-Tridecylphenyl)-1H-1λ3-benzo[b]iodo-3(2H)-one (2f).
The reaction of 2-iodobenzoic acid 1 (248 mg, 1.0 mmol), Oxone
(400 mg, 0.65 mmol), H2SO4 (total 0.8 mL) and 1-phenyltridecane
(0.30 mL, 1.01 mmol) according to the general procedure afforded 443
mg (86%) of product 2f·1/2H2O, isolated as off-white crystals: mp 126−
127 °C (from water); 1H NMR (CD3OD, 500 MHz) δ 8.28 (dd, J = 1.5,
7.5 Hz, 1 H), 8.03 (d, J = 8.0 Hz, 2 H), 7.64 (ddd, J = 1.0, 7.5, 8.0 Hz,1
H), 7.49 (m, 3 H), 6.87 (d, J = 8.0 Hz, 1 H), 2.78 (t, J = 7.5 Hz, 2 H), 1.71
(m, 2 H), 1.34 (m, 20 H), 0.90 (t, J = 7.0 Hz, 3 H); 13C NMR (CD3OD +
CDCl3, 125 MHz) δ 169.9, 149.94, 149.93, 138.5, 133.19, 133.18,
131.75, 131.74, 128.6, 116.1, 111.4, 36.9, 33.0, 32.2, 30.69, 30.67, 30.63,
30.6, 30.44, 30.38, 30.37, 30.2, 23.7, 14.6. Anal. Calcd for
C26H35IO2·1/2H2O: C, 60.58; H, 7.04; I, 24.62. Found: C, 60.92; H,
6.94; I, 24.52.
1-(4-(4-Carboxybutyl)phenyl)-1H-1λ3-benzo[b]iodo-3(2H)-
one (2l). The reaction of 2-iodobenzoic acid 1 (248 mg, 1.0 mmol),
Oxone (400 mg, 0.65 mmol), H2SO4 (total 0.8 mL), and 5-phenyl-
pentanoic acid (178 mg, 1.0 mmol) in 1.0 mL CH2Cl2 was carried out
according to the general procedure. The isolation of the product was
performed by the following workup: the reaction mixture was neutralized
by NaHCO3 to pH 6.0, the precipitate was filtered, washed with water,
and dried to afford 352 mg (83%) of product 2l, isolated as off-white
1-(2,4,6-Trimethylphenyl)-1H-1λ3-benzo[b]iodo-3(2H)-one
(2g). The reaction of 2-iodobenzoic acid 1 (248 mg, 1.0 mmol), Oxone
(400 mg, 0.65 mmol), H2SO4 (total 0.8 mL), and 1,3,5-trimethylben-
zene (0.15 mL, 1.1 mmol) according to the general procedure afforded
300 mg (78%) of product 2g monohydrate, isolated as off-white crystals:
1
crystals: mp 234.5−235.5 °C (from water); H NMR (CD3OD, 500
MHz) δ 8.28 (dd, J = 2.0, 8.5 Hz, 1 H), 8.02 (m, 2 H), 7.63 (m, 1 H), 7.49
(m, 3 H), 6.87 (d, J = 7.55 Hz, 1 H), 2.81 (t, J = 7.5 Hz, 2 H), 2.35 (t, J =
7.5 Hz, 2 H), 1.76 (m, 2 H), 1.68 (m, 2 H); 13C NMR (CD3OD, 125
MHz) 177.3, 170.1, 149.7, 138.9, 135.3, 134.8, 133.4, 133.3, 131.9, 128.8,
116.3, 112.3, 36.6, 34.8, 31.7, 25.7. Anal. Calcd for C18H17IO4: C, 50.96;
H, 4.04; I, 29.91. Found: C, 50.92; H, 4.02; I, 29.91.
mp 223−223.5 °C (from water) (lit.5a mp 213−214 °C); H NMR
1
(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. Single crystals of product 2g suitable for X-ray crystallographic
analysis were obtained by slow crystallization from water. For details on
crystal structure of compound 2g see the CIF in the Supporting
Information.
1-(4-(4-(Methoxycarbonyl)butyl)phenyl)-1H-1λ3-benzo[b]-
iodo-3(2H)-one (2m). The reaction of 2-iodobenzoic acid 1 (248 mg,
1.0 mmol), Oxone (400 mg, 0.65 mmol), H2SO4 (total 0.8 mL), and
methyl-5-phenylpentanoate (215 mg, 1.12 mmol) in 1.0 mL CH2Cl2
according to the general afforded 406 mg (89%) of product 2m·1/2H2O,
isolated as off-white crystals: mp 132.5−134 °C (from water); 1H NMR
(CDCl3, 500 MHz) δ 8.43 (dd, J = 1.5, 7.5 Hz, 1 H), 7.91 (d, J = 8.0 Hz,
2 H), 7.59 (m, 1 H), 7.43 (m, 3 H), 6.80 (d, J = 8.5 Hz, 1 H), 3.69
(s, 3 H), 2.76 (t, J = 7.0 Hz, 2 H), 2.38 (t, J = 6.5 Hz, 2 H), 1.73 (m, 4 H);
13C NMR (CDCl3, 125 MHz) 173.8, 167.7, 148.1, 137.4, 134.3, 133.0,
1-(2,3,5,6-Tetramethylphenyl)-1H-1λ3-benzo[b]iodo-3(2H)-
one (2h). The reaction of 2-iodobenzoic acid 1 (248 mg, 1.0 mmol),
Oxone (400 mg, 0.65 mmol), and H2SO4 (total 0.8 mL) was performed
according to the general procedure. Then a solution of 1,2,4,5-
tetramethylbenzene (140 mg, 1.05 mmol) in 2.0 mL of CH2Cl2 was
added by 0.1 mL portions and stirred at 5 °C for 30 min; a change of the
132.2, 130.8, 126.6, 115.4, 110.2, 51.6, 35.6, 33.7, 30.4, 24.5. Anal. Calcd
3771
dx.doi.org/10.1021/jo400212u | J. Org. Chem. 2013, 78, 3767−3773

The Journal of Organic Chemistry
Article
for C19H21IO4·1/2H2O: C, 51.02; H, 4.51; I, 28.37. Found: C, 50.87; H,
4.43; I, 28.45.
AUTHOR INFORMATION
Corresponding Author
*E-mail: yusubov@mail.ru, vnemykin@d.umn.edu, vzhdanki@
d.umn.edu.
■
1-Phenyl-7-methyl-1H-1λ3-benzo[b]iodo-3(2H)-one (2n). The
reaction of 2-iodo-3-methylbenzoic acid 7 (262 mg, 1.0 mmol), Oxone
(400 mg, 0.65 mmol), H2SO4 (total 0.8 mL), and benzene (0.4 mL)
according to the general procedure afforded 270 mg of product 2n as
dark brown solid. Treatment of this solid with activated carbon in
boiling water afforded 185 mg (52%) of product 2n monohydrate,
isolated as off-white crystals: mp 170−172 °C (from water); 1H NMR
(CD3OD, 500 MHz) δ 8.10 (m, 2 H), 7.98 (dd, J = 1.5, 7.5 Hz, 1 H),
7.67 (m, 1 H), 7.51 (m, 3 H), 7.43 (dd, J = 0.5, 7.5 Hz, 1 H), 2.03 (s, 3
H); 13C NMR (CD3OD, 125 MHz) δ 171.5, 142.4, 140.7, 137.3, 136.9,
133.3, 132.8, 132.5, 131.0, 119.6, 118.0, 25.4. Anal. Calcd for C14H13IO3:
C, 47.21; H, 3.68; I, 35.63. Found: C, 47.38; H, 3.65; I, 35.72. Single
crystals of product 2n suitable for X-ray crystallographic analysis were
obtained by slow crystallization from water. For details on the crystal
structure of compound 2n, see the CIF in the Supporting Information.
1-(2,4,6-Trimethylphenyl)-7-methyl-1H-1λ3-benzo[b]iodo-
3(2H)-one (2o). The reaction of 2-iodo-3-methylbenzoic acid 7 (314
mg, 1.2 mmol), Oxone (412 mg, 0.67 mmol), H2SO4 (total 0.85 mL),
and 1,3,5-trimethylbenzene (0.2 mL, 1.44 mmol) according to the
general procedure afforded 360 mg of product 2o as a dark brown solid.
Treatment of this solid with activated carbon in boiling water afforded
282 mg (62%) of 1o, isolated after crystallyzation from water as off-
white crystals: mp 148.5−150.5 °C (from water/methanol); 1H NMR
(CD3OD, 500 MHz) δ 8.06 (d, J = 0.5 Hz, 1 H), 7.52 (m, 1 H), 7.41
(d, J = 7.5 Hz, 1 H), 7.18 (s, 2 H), 2.50 (s, 6 H), 2.37 (s, 3 H), 1.86
(s, 3 H); 13C NMR (CD3OD, 125 MHz) δ 171.2, 145.2, 144.0, 142.1, 140.1,
137.5, 132.1, 131.7, 131.1, 122.6, 118.3, 26.7, 23.5, 21.2. Anal. Calcd for
C17H17IO2: C, 53.70; H, 4.51; I, 33.38. Found: C, 53.75; H, 4.48; I, 33.61.
Single crystals of product 2o suitable for X-ray crystallographic analysis
were obtained by slow crystallization from water/methanol. For details on
the crystal structure of compound 2o, see the CIF in the Supporting
Information.
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
This work was supported by research grants from the National
Science Foundation (Nos. CHE-1009038 and 1262479). M.S.Y.
and V.V.Z. are also thankful to the Government of Russia for
support of their cooperative research program (FCP,
GK11.519.11.5010, Zayavka 2011-1.9-519-024-070, Russian
Foundation for Basic Research No. 12-03-00978-a, and a Grant
from the Government of Russia 2012-220-03-9803).
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ASSOCIATED CONTENT
■
S
* Supporting Information
X-ray data for compounds 2b, 2g, 2n, and 2o (CIF) and copies of
NMR spectra for all compounds. This material is available free of
charge via the Internet at http://pubs.acs.org.
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