Carboxyl radical-assisted 1,5-aryl migration through Smiles rearrangement

Article abstract of DOI:10.1039/c6ob01758d

We report herein, a silver(i)-catalyzed Smiles rearrangement of 2-aryloxy- or 2-(arylthio)benzoic acids to provide aryl-2-hydroxybenzoate or aryl-2-mercaptobenzoate dimer, respectively, through 1,5-aryl migration from oxygen or sulfur to carboxylate oxygen. Mechanistically, the aryl ether moiety undergoes an intramolecular ipso attack by the carboxyl radical followed by a C-O or C-S bond cleavage. Aryl-2-mercaptobenzoates undergo oxidative dimerization through a thiol moiety in situ.

Full text of DOI:10.1039/c6ob01758d

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Carboxyl Radical-Assisted 1,5-Aryl Migration through Smiles
Rearrangement
Asik Hossian,a,b and Ranjan Janaa,b*
Received 00th January 20xx,
Accepted 00th January 20xx
We report herein, a silver(I)-catalyzed Smiles rearrangement of 2-aryloxy- or 2-(arylthio)benzoic acids to provide aryl-2-
hydroxybenzoate or aryl-2-mercaptobenzoate dimer respectively through 1,5-aryl migration from oxygen or sulfur to
carboxylate oxygen. Mechanistically, the aryl ether moiety undergoes an intramolecular ipso attack by the carboxyl radical
followed by a C-O or C-S bond cleavage. Aryl-2-mercaptobenzoates undergoes oxidative dimerization through thiol moiety
in situ.
DOI: 10.1039/x0xx00000x
www.rsc.org/
utilized for the decarboxylative Minisci-type arylation with benzoic
acid derivatives.12 Intrigued by these earlier reports we were
Introduction
interested to develop
a
silver-catalyzed decarboxylative
dibenzofuran synthesis from 2-aryloxybenzoic acids in an
intramolecular fashion. Interestingly, we observed 1,5-aryl
migration through Smile-type rearrangement in lieu of expected
decarboxylative dibenzofuran formation (Scheme 1). Since radical
aryl migration is a useful tool in organic synthesis,13 we were
interested to develop this rearrangement reaction. From literature,
a persulfate-mediated uncontrolled 1,5-aryl migration/oxidative
dimerization cascade in water was reported.14 Surprisingly, in our
present study, the 1,5-aryl migratory product formed
predominantly and a trace amount (<5%) of dimerization product
was observed in electrospray ionization (ESI) mass spectrometry of
the crude reaction mixture (see the Electronic Supplementary
Information). A copper-catalyzed domino aryl migration/C-O/C-N
bond formation for the synthesis of dibenzoxazepinones,15 and a
base-promoted 1,5-aryl migration through Smiles rearrangement
were reported.16 But, the later protocol is limited to the
nicotinamides only where the phenolic hydroxyl group is stabilized
by the ortho pyridinyl nitrogen. We report herein, a silver(I)-
catalyzed 1,5-aryl migration of 2-aryloxybenzoic acids via C-O/C-S
bond cleavage and C-O bond formation cascade. The corresponding
Scheme 1. Divergent syntheses from ortho-substituted benzoic
acids
The rearrangement reactions provide concise routes to the atom-
economic synthesis in organic chemistry.1 In this vein, the Smiles
rearrangement offers a unique opportunity to the synthesis of
privileged medicinal scaffolds originally through an intramolecular
nucleophilic aromatic substitution.2 Varieties of Smiles
rearrangement such as Truce-Smiles,3 Ugi-Smiles4 have been
explored for the multi-component reactions (MCR) in medicinal
chemistry. However, the potential of radical-Smiles rearrangement
has been realized recently.5 Notably, the Zard group explored a
peroxide-mediated radical-Smiles rearrangement to access aryl- or
pyridylacetic acid derivatives from N-(α-xanthyl)acetanilides or N-
(α-xanthyl)acetylaminopyridines
respectively.6
Recently,
a
photoredox-catalyzed synthesis of a difluoro-substituted spirocyclic
ORL-1 antagonist through radical-Smiles rearrangement was
reported by the Stephenson group which provides an alternative
and practical route with easily available starting materials at
industrially relevant scale and catalyst loading.7
Carboxylic acids have been explored as inexpensive, readily
available, air and moisture stable cross-coupling partner.8 The
Glorius group reported
intramolecular C-H arylation to afford dibenzofuran using 2-
aryloxybenzoic Alternatively, silver(I)-catalyzed
acids.9
a palladium-catalyzed decarboxylative
Pd cat., Ag2CO3
decarboxylative Pschorr-type cyclization to afford fluorenone was
reported by the Greaney group.10 The Baran group also employed
this Ag(I)/K2S2O8 catalytic system for the generation of aryl radicals
from boronate counterpart which has been trapped intra- and
intermolecularly.11 Recently, similar catalytic system has been
X = O, decar boxylative
O
ref . 9
O
OH
AgI cat., K2S2O8
X
X = (C=O), decar boxylative
ref . 10
O
O
AgI cat., K2S2O8
O
X = O, S, Smiles rearrangement
XH
1,5-aryl migration
this work
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thioethers provided the rearranged product with disulfide bond aAll reactions were carried out in 0.1 mmol scale. bYields refer to
formation under this oxidative condition.
here are overall isolated yields. c3.0 equiv of K2S2O8 was used.
Results and discussion
rigorous optimization. Interestingly, salicylic acid formation through
hydrolysis of the Smiles rearrangement product was not observed
under the reaction condition.
To optimize the reaction conditions, 2-phenoxybenzoic acid was
chosen as a model substrate. Initially, catalytic amount of silver(I)
nitrate in the presence of 3.0 equiv of K2S2O8 afforded the Smiles
rearrangement product in 34% yield. Decreasing the amount of
oxidant to 1.5 equiv, the yield was further improved. However,
other common oxidants such as aq. tert-butyl hydroperoxide,
(diacetoxyiodo)benzene (PIDA), benzoyl peroxide even ammonium
persulfate were not effective for this transformation. Similarly,
other silver salts, palladium(II)triflate, iron(III)acetylacetonato,
nickel(II)triflate, copper(II)acetate, tetrabutylammonium iodide
were proved to be inferior catalysts compare to silver(I) nitrate
Gratifyingly, the yield was improved with the addition of sodium
trifluoroacetate as a base. After screening several bases, ultimately
potassium trifluoroacetate provided the migratory product in good
yields (for details see the Electronic Supplementary Information).
Acetonitrile was the solvent of choice since other solvents such as
dichloroethane, N,N-dimethylformamide, toluene etc. afforded no
or inferior yields. A substantial amount of decomposition product
formation was observed which we could not eliminate even after
Next we explored the substrate scope under the optimized reaction
condition. The starting materials were synthesized through
a
copper-catalyzed cross-coupling of 2-halobenzoic acid and phenol
or thiophenol derivatives. A wide range of substrates underwent
Smiles rearrangement to provide 1,5-aryl migratory products.
Several substituents on the phenol component such as alkyl (2g, 2k,
2p, Scheme 2), aryl (2h, Scheme 2), alkoxyl (2e, 2f, 2l, 2n, Scheme
2), chloro (2c, 2m, 2u, Scheme 2), bromo (2d, Scheme 2), and fluoro
(2b, Scheme 2), were well tolerated under the reaction conditions.
Interestingly, substrates derived from 1-, and 2- naphthols (2i, 2j,
2q, Scheme 2) also furnished the migratory products in good yields.
Similarly, substitutions on the benzoic acid moiety such as fluoro
(2o-2q, Scheme 2), chloro (2r, Scheme 2), and nitro groups (2s-2u,
Scheme 2) were also survived. A representative structure of the
migratory product has been unambiguously characterized by X-ray
crystallography also (2t). But, electron-rich benzoic acid such as 5-
methoxy-2-phenoxybenzoic acid, 1v was unreactive under the
Scheme 2. Substrate scope with diarylethersa,b
Table 1. Optimization of the reaction conditionsa,b
entry catalyst
(5 mol %)
oxidant
base
yield
(%)b
(1.5 equiv)
(2.0 equiv)
1c
AgNO3
AgNO3
AgNO3
AgNO3
AgNO3
AgNO3
AgOAc
Ag2CO3
Pd(TFA)2
Fe(acac)3
Ni(OTf)2
Cu(OAc)
TBAI
K2S2O8
-
34
44
0
2
K2S2O8
-
3
aq. TBHP
(NH4)2S2O8
PhI(OAc)2
(PhCOO)2
K2S2O8
-
4
-
27
0
5
-
6
-
trace
34
36
trace
36
35
25
30
50
7
-
8
K2S2O8
-
9
K2S2O8
-
10
11
12
13
14
K2S2O8
-
K2S2O8
-
K2S2O8
-
K2S2O8
-
AgNO3
K2S2O8
CF3CO2Na
15
16
17
AgNO3
-
K2S2O8
K2S2O8
-
CF3CO2K
CF3CO2K
CF3CO2K
64
37
0
AgNO3
2 | J. Name., 2012, 00, 1-3
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aThe reaction was carried out in 0.1 mmol scale, 0.05 M. bYield refer We performed several control experiments to understand the
to here is the average isolated yield of at least two experiments. mechanism of this unexpected result. Generation of aryl radical
cThe reaction was performed in 0.5 mmol scale.
through the decomposition of aryl diazonium salts and aryl
boronates is energetically favourable process which occurs
spontaneously at mild conditions.18,11 But generation of aryl radical
through decarboxylation is a high energetic process which occurs at
elevated temperature.12 In the case of 2-aroylbenzoic acid, the
incipient radical generated through decarboxylation is stabilized by
the ortho- ketone group.10 In contrast, in this present study, the
incipient radical is destabilized by the ortho ether moiety. This is
consistent with our previous observation that ortho, ortho
dimethoxy carboxylic acid does not decarboxylate with silver(I)
catalyst whereas palladium catalyst is effective.19 Previously,
Ag(I)/K2S2O8 catalytic system has been utilized for the C-H
carboxylation in the biaryl system.20 However, in this case C-H
insertion of the carboxyl radical is not favoured due to the
formation of seven membered ring. Instead, an ipso attack to the
ether carbon is favoured and a concomitant homolytic C-O bond
cleavage may occur. Typically, reductive cleavage of inert
diarylether linkage is possible by nickel catalyst.21 However, simple
diarylether or 2-aryloxybenzamides did not furnish any product
under this optimized condition. Therefore, 2-carboxylic acid was
found to be crucial for the reaction to occur. The reaction was
completely arrested with the addition of radical scavengers such as
2.0 equiv of 2,2,6,6-tetramethylpiperidinyl-1-oxy (TEMPO) or 4.0
equiv of butylated hydroxytoluene (BHT) (Scheme 4a). Therefore,
the reaction may proceed through a radical mechanism. The
involvement of radical mechanism is further supported by the fact
that the reaction also proceeds with persulfate in the absence of
silver(I)nitrate to provide the desired product in moderate yield
(entry 16, Table 1).14,17 In order to gain insight further, we
performed a cross-over experiment. While an equimolar mixture of
1e and 1t was subjected to the reaction conditions no cross-over
products were detected in 1H NMR as well as (ESI) mass
spectrometry (Scheme 4b) (see the ESI). It suggests that the
reaction condition. However, it was difficult to predict the influence
of the electronic nature of the substituents since a substantial
amount of decomposition products was observed. Unfortunately,
the yield of the products was decreased to some extent at higher
scale. For example, in a reaction at 0.5 mmol scale, 1a provided 50%
yield of the desired product 2a (Scheme 2). Similarly, 2c and 2e
were isolated in 40% and 48% yields respectively at 0.5 mmol scale.
Phenyl ether of nicotinic acid, 1w also did not provide any desired
product. Interestingly, the corresponding benzamide in place of
benzoic acid did not afford any desired product which indicates a
distinct reaction mechanism to the base-promoted anionic Smiles
rearrangement.16 The desired product was hydrolyzed to provide
corresponding salicylic acid (6a) and phenol in an alcoholic sodium
hydroxide solution (see the Electronic Supplementary Information).
On the accomplishment of Smiles rearrangement of 2-
aryloxybenzoic acids, we were interested to examine the migratory
event of the corresponding thioethers. Under the optimized
conditions, the corresponding migratory product with disulfide
bond 4a was isolated albeit in moderate yield and a substantial
amount of starting material was recovered. Gratifyingly, excellent
to good yield of the corresponding Smiles rearrangement product
was isolated by simply omitting the base from the standard reaction
conditions. From 1H NMR and mass spectroscopy it was also
confirmed that the free thiol groups underwent oxidative
homocoupling to furnish disulfide linkage in situ. This rearranged
disulfide product was also observed as a byproduct (15%) in the
persulfate mediated oxidation of diphenyl sulfide-2-carboxylic
acids.17 Gratifyingly, under our optimized condition, a number of 2-
arylmarcapto benzoic acids with different substituents provided the
1,5-aryl migratory products followed by oxidative homocoupling
products in good to high yields (Scheme 3). Unfortunately, 5-
methoxy-2-(phenylthio)benzoic acid was unreactive under the
reaction condition. The disulfide linkage was easily reduced to the
corresponding thiols (5a) with triphenylphosphine (see the
Electronic Supplementary Information).
Scheme 4. Control experiments
Scheme 3. Substrate scope with diarylthioethersab
aThe reaction was carried out in 0.2 mmol scale, 0.05 M. bYield refer
to here is the average isolated yield of at least two experiments.
Investigation of the reaction mechanism
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reaction may involve an intramolecular rearrangement for 1,5-aryl measured using EI (magnetic sector, positive ion) and ESI (Q-TOF,
migration.
positive ion) techniques. Infrared (IR) spectra were recorded on
Fourier transform infrared spectroscopy; only intense peaks were
reported.
General experimental procedure for the preparation of 2-
phenoxybenzoic acids, Scheme 2.23
From the control experiments and substitution pattern of the
observed products, we postulated the reaction mechanism. In the
presence of catalytic silver(I) salt and stoichiometric persulfate
anion the carboxyl radical I (Scheme 5) is generated. Instead of
decarboxylation the carboxyl radical then undergoes an ipso attack
to the arylether moiety II (Scheme 5). A concomitant homolytic C-O
bond cleavage occurs which lead to the formation of aryl ester
through 1,5 aryl migration IV (Scheme 5). The incipient phenoxyl
radical may abstract a hydrogen atom from solvent or reaction
medium to give the final migratory product 2c (Scheme 5). This
phenomenon is well-established in the previous literature.14,22
Additionally, the reaction in nitromethane also provides the
migratory product 2a in lower (48%) yield. However, the exact
nature of hydrogen whether it is a proton or hydride is not clear at
this moment. In the case of thioethers, the homocoupling product
may occur through the thiyl radical dimerization. The dimerization
also may occur from the final migratory thiol product under the
oxidative reaction conditions. To probe, when monomer of 4a was
subjected to the reaction conditions it furnished the dimerised
product 4a in quantitative yield. However, the possibility of thiyl
radical dimerization is also plausible.
To an oven-dried 100 mL round bottom flask equipped with
magnetic stir bar, 2-halo benzoic acid (6.2 mmol, 1.0 equiv) was
added in 50 mL of dimethylformamide (DMF), followed by phenol
(12.4 mmol, 2.0 equiv), 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU)
(2.6 mL, 18.6 mmol, 3.0 equiv), pyridine (0.1 mL), copper(0) (52 mg,
0.81 mmol), and copper(I) iodide (53 mg, 0.28 mmol). The reaction
mixture was heated to 160 oC under nitrogen atmosphere. After
consumption of the starting materials as indicated by TLC (typically
2 h) the reaction mixture was cooled and acidified with 3N HCl until
no more precipitate was formed. The resulting precipitates and
reaction mixture were extracted with dichloromethane (60 mL) and
cold water (70 mL). The organic layer was washed with cold water
(20 mL x 3) and brine (10 mL), dried over anhydrous Na2SO4 and the
solvent was evaporated under reduced pressure. The crude product
was purified by column chromatography using ethyl acetate/hexane
as eluent to afford the desired white solid product.
2-Phenoxybenzoic acid, 1a, Scheme 2.23 The same general
procedure was followed by using 2-iodo benzoic acid (1.55 g, 6.2
mmol, 1.0 equiv) and Phenol (1.20 g, 12.4 mmol, 2.0 equiv). Column
chromatography (SiO2, eluting with 7:3 hexane/ethyl acetate)
afforded the desired product as a white solid, (1.14 g, 86%), mp
107-109 oC. 1H NMR (300 MHz, DMSO-d6): δ 12.84 (brs, 1H), 7.81 (d,
J = 7.8 Hz, 1H), 7.54 (td, J = 8.1 Hz, 1.8 Hz, 1H), 7.33 (t, J = 8.4 Hz,
2H), 7.24 (t, J = 7.5 Hz, 1H), 7.06 (t, J = 7.2 Hz, 1H), 6.98 (d, J = 8.1
Hz, 1H), 6.88 (d, J = 8.4 Hz, 2H); 13C NMR (75 MHz, DMSO-d6): δ
166.6, 157.5, 154.9, 133.5, 131.4, 129.9, 124.6, 124.0, 122.8, 121.0,
117.6.
Scheme 5. Plausible mechanism of 1,5-aryl migration
2-(4-Fluorophenoxy)benzoic acid, 1b, Scheme 2.9 The same general
procedure was followed by using 2-iodo benzoic acid (1.55 g, 6.2
mmol, 1.0 equiv) and 4-fluorophenol (1.40 g, 12.4 mmol, 2.0 equiv).
Column chromatography (SiO2, eluting with 7:3 hexane/ethyl
acetate) afforded the desired product as a white solid, (1.12 g,
78%), mp 142-144 oC. 1H NMR (300 MHz, DMSO-d6): δ 12.91 (brs,
1H), 7.82 (dd, J = 7.8 Hz, 1.8 Hz, 1H), 7.56 (td, J = 8.4 Hz, 1.8 Hz, 1H),
7.15-7.29 (m, 3H), 6.93-7.00 (m, 3H); 13C NMR (75 MHz, DMSO-d6):
δ 166.6, 157.9 (d, J = 237.8 Hz), 155.2, 153.5 (d, J = 2.2 Hz), 133.6,
131.4, 124.3, 124.0, 120.6, 119.5 (d, J = 8.2 Hz), 116.4 (d, J = 23.2
Hz).
Conclusions
In conclusion, we have developed a silver(I)-catalyzed selective 1,5-
aryl migration of 2-aryloxy- or 2-(arylthio)benzoic acids through
radical Smiles rearrangement. This unexpected aryl translocation
occurs through an intramolecular ipso attack of the carboxyl radical
to the arylether instead of expected intramolecular decarboxylative
arylation to afford dibenzofuran. Subsequently, inert C-O bond
cleavage of the diaryl ether occurs selectively. The corresponding
thioethers also furnished the migratory products with disulfide
linkage under this oxidative condition. We anticipate that the
present catalytic system could be useful for the selective C-O bond
cleavage in biomass conversion.
2-(4-Chlorophenoxy)benzoic acid, 1c, Scheme 2. The same general
procedure was followed by using 2-iodo benzoic acid (1.55 g, 6.2
mmol, 1.0 equiv) and 4-chlorophenol (1.60 g, 12.4 mmol, 2.0 equiv).
Column chromatography (SiO2, eluting with 7:3 hexane/ethyl
acetate) afforded the desired product as a white solid, (1.3 g, 84%),
mp 115-117 oC. 1H NMR (300 MHz, DMSO-d6): δ 7.85 (dd, J = 7.5 Hz,
1.5 Hz, 1H), 7.60 (td, J = 8.1 Hz, 1.8 Hz, 1H), 7.36-7.41 (m, 2H), 7.31
(td, J = 8.1 Hz, 0.6 Hz, 1H), 7.08 (d, J = 8.1 Hz, 1H), 6.87-6.92 (m, 2H);
13C NMR (75 MHz, DMSO-d6): δ 166.4, 156.7, 154.3, 133.8, 131.6,
129.7, 126.5, 124.74, 124.67, 121.6, 119.0; IR (neat): υmax 1690,
1484, 1313, 1244, 1091, 826 cm-1; HRMS (ESI, m/z) calcd. for
C13H9ClO3Na [M + Na]+: 271.0138; found: 271.0130.
Experimental section
General information
2-(4-Bromophenoxy)benzoic acid, 1d, Scheme 2.9 The same
general procedure was followed by using 2-iodo benzoic acid (1.55
g, 6.2 mmol, 1.0 equiv) and 4-bromophenol (1.2 g, 12.4 mmol, 2.0
equiv). Column chromatography (SiO2, eluting with 7:3
hexane/ethyl acetate) afforded the desired product as a white solid,
(1.27 g, 70%), mp 118-120 oC. 1H NMR (300 MHz, DMSO-d6): δ 12.94
Melting points were determined in open end-capillary tubes and
are uncorrected. TLC was performed on silica gel plates (silica gel
60, f254), and the spots were visualized with UV light (254 and 365
nm) and KMnO4 stain. 1H and 13C NMR spectra were recorded in
CDCl3 using TMS as the internal standard. HRMS (m/z) were
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(brs, 1H), 7.86 (d, J = 6.9 Hz, 1H), 7.60 (t, J = 7.5 Hz, 1H), 7.50 (d, J = 2-(o-Tolyloxy)benzoic acid, 1k, Scheme 2.9 The same general
8.7 Hz, 2H), 7.32 (t, J = 7.5 Hz, 1H), 7.09 (d, J = 8.1 Hz, 1H), 6.84 (d, J procedure was followed by using 2-iodo benzoic acid (1.55 g, 6.2
= 9.0 Hz, 2H); 13C NMR (75 MHz, DMSO-d6): δ 166.3, 157.2, 154.2, mmol, 1.0 equiv) and o-cresol (1.3 mL, 12.4 mmol, 2.0 equiv).
133.8, 132.6, 131.6, 124.7, 121.7, 119.3, 114.2.
Column chromatography (SiO2, eluting with 7:3 hexane/ethyl
2-(4-Methoxyphenoxy)benzoic acid, 1e, Scheme 2.9 The same acetate) afforded the desired product as a white solid, (990 mg,
general procedure was followed by using 2-iodo benzoic acid (1.55 70%), mp 122-124 oC. 1H NMR (300 MHz, DMSO-d6): δ 12.86 (brs,
g, 6.2 mmol, 1.0 equiv) and 4-methoxyphenol (1.54 g, 12.4 mmol, 1H), 7.81 (dd, J = 7.8 Hz, 1.5 Hz, 1H), 7.50 (td, J = 8.7 Hz, 1.8 Hz, 1H),
2.0 equiv). Column chromatography (SiO2, eluting with 6:4 7.30 (d, J = 7.2 Hz, 1H), 7.15-7.22 (m, 2H), 7.06 (t, J = 7.5 Hz, 1H),
hexane/ethyl acetate) afforded the desired product as a white solid, 6.80 (d, J = 8.1 Hz, 1H), 6.73 (d, J = 7.8 Hz, 1H), 2.30 (s, 3H); 13C NMR
o
(1.29 g, 85%), mp 143-145 C. 1H NMR (300 MHz, DMSO-d6): δ 7.77 (75 MHz, DMSO-d6): δ 167.1, 156.0, 155.0, 133.8, 131.8, 128.9,
(dd, J = 7.5 Hz, 1.5 Hz, 1H), 7.48 (td, J = 8.4 Hz, 1.5 Hz, 1H), 7.17 (t, J 127.7, 124.0, 123.8, 123.4, 119.2, 118.4, 16.2.
= 7.5 Hz, 1H), 6.89-6.95 (m, 4H), 6.84 (d, J = 8.1 Hz, 1H), 3.72 (s, 3H); 2-(2-Methoxyphenoxy)benzoic acid, 1l, Scheme 2. The same
13C NMR (75 MHz, DMSO-d6): δ 167.1, 156.4, 155.5, 150.3, 133.4, general procedure was followed by using 2-iodo benzoic acid (1.55
131.3, 123.8, 123.1, 120.0, 119.2, 115.2, 55.6.
g, 6.2 mmol, 1.0 equiv) and 2-methoxyphenol (1.54 g, 12.4 mmol,
2-(4-(Benzyloxy)phenoxy)benzoic acid, 1f, Scheme 2. The same 2.0 equiv). Column chromatography (SiO2, eluting with 6:4
general procedure was followed by using 2-iodo benzoic acid (1.55 hexane/ethyl acetate) afforded the desired product as a white solid,
g, 6.2 mmol, 1.0 equiv) and 4-(benzyloxy)phenol (2.48 g, 12.4 mmol, (1.09 g, 72%), mp 114-116 oC. 1H NMR (300 MHz, DMSO-d6): δ 12.82
2.0 equiv). Column chromatography (SiO2, eluting with 6:4 (brs, 1H), 7.77 (d, J = 7.5 Hz, 1H), 7.43 (t, J = 7.2 Hz, 1H), 7.09-7.21
hexane/ethyl acetate) afforded the desired product as a white solid, (m, 3H), 6.92-6.98 (m, 2H), 6.65 (d, J = 8.4 Hz, 1H), 3.74 (s, 3H); 13
C
(1.47 g, 74%), mp 153-155 oC. 1H NMR (300 MHz, DMSO-d6): δ 12.85 NMR (75 MHz, DMSO-d6): δ 166.8, 156.5, 151.0, 144.1, 133.2,
(brs, 1H), 7.78 (dd, J = 7.5 Hz, 1.2 Hz, 1H), 7.31-7.52 (m, 6H), 7.18 (t, 131.2, 125.3, 122.3, 122.2, 121.2, 120.8, 117.0, 113.5, 55.7; IR
J = 7.5 Hz, 1H), 7.02 (d, J = 9.0 Hz, 2H), 6.92 (d, J = 9.0 Hz, 2H), 6.87 (neat): υmax 1666, 1494, 1306, 1260, 749 cm-1; HRMS (ESI, m/z)
(d, J = 8.4 Hz, 1H), 5.07 (s, 2H); 13C NMR (75 MHz, DMSO-d6): δ calcd. for C14H12O4Na [M + Na]+: 267.0633; found: 267.0628.
166.8, 156.3, 154.5, 150.4, 137.1, 133.3, 131.3, 128.5, 127.9, 127.8, 2-(3-Chlorophenoxy)benzoic acid, 1m, Scheme 2. The same general
123.7, 123.0, 119.9, 119.2, 116.0, 69.7; IR (neat): υmax 1684, 1503, procedure was followed by using 2-iodo benzoic acid (1.55 g, 6.2
1311, 1216, 1019, 784 cm-1; HRMS (ESI, m/z) calcd. for C20H16O4Na mmol, 1.0 equiv) and 3-chlorophenol (1.33 mL, 12.4 mmol, 2.0
[M + Na]+: 343.0946; found: 343.0950.
2-(p-Tolyloxy)benzoic acid, 1g, Scheme 2.9 The same general hexane/ethyl acetate) afforded the desired product as a white solid,
equiv). Column chromatography (SiO2, eluting with 7:3
o
1
procedure was followed by using 2-iodo benzoic acid (1.55 g, 6.2 (1.09 g, 71%), mp 98-100 C. H NMR (300 MHz, DMSO-d6): δ 12.97
mmol, 1.0 equiv) and p-cresol (1.34 g, 12.4 mmol, 2.0 equiv). (brs, 1H), 7.88 (d, J = 7.8 Hz, 1H), 7.63 (t, J = 7.5 Hz, 1H), 7.32-7.39
Column chromatography (SiO2, eluting with 7:3 hexane/ethyl (m, 2H), 7.14 (d, J = 7.8 Hz, 2H), 6.92 (s, 1H), 6.83 (dd, J = 8.4 Hz, 2.1
acetate) afforded the desired product as a white solid, (1.13 g, Hz, 1H); 13C NMR (75 MHz, DMSO-d6): δ 166.2, 158.9, 153.8, 133.9,
o
1
80%), mp 122-124 C. H NMR (300 MHz, DMSO-d6): δ 7.80 (dd, J = 133.8, 131.6, 131.2, 125.0, 124.9, 122.5, 122.1, 117.0, 115.7; IR
7.8 Hz, 1.5 Hz, 1H), 7.52 (td, J = 8.4 Hz, 1.5 Hz, 1H), 7.22 (td, J = 7.5 (neat): υmax 1693, 1593, 1468, 1417, 1239, 913, 763 cm-1; HRMS
Hz, 0.6 Hz, 1H), 7.16 (d, J = 8.1 Hz, 2H), 6.93 (d, J = 8.1 Hz, 1H), 6.82 (ESI, m/z) calcd. for C13H9ClO3Na [M + Na]+: 271.0138; found:
(d, J = 8.4 Hz, 2H), 2.27 (s, 3H); 13C NMR (75 MHz, DMSO-d6): δ 271.0134.
166.7, 155.5, 155.0, 133.4, 132.1, 131.3, 130.3, 124.2, 123.5, 120.3, 2-(3-Methoxyphenoxy)benzoic acid, 1n, Scheme 2.24 The same
118.0, 20.3.
general procedure was followed by using 2-iodo benzoic acid (1.55
4-Diphenyl-2-phenoxybenzoic acid, 1h, Scheme 2. The same g, 6.2 mmol, 1.0 equiv) and 3-methoxyphenol (1.54 g, 12.4 mmol,
general procedure was followed by using 2-iodo benzoic acid (1.55 2.0 equiv). Column chromatography (SiO2, eluting with 6:4
g, 6.2 mmol, 1.0 equiv) and 4-phenylphenol (2.11 g, 12.4 mmol, 2.0 hexane/ethyl acetate) afforded the desired product as a white solid,
o
1
equiv). Column chromatography (SiO2, eluting with 7:3 (1.14 g, 75%), mp 118-120 C. H NMR (300 MHz, DMSO-d6): δ 7.82
hexane/ethyl acetate) afforded the desired product as a white solid, (d, J = 7.5 Hz, 1H), 7.57 (t, J = 7.2 Hz, 1H), 7.21-7.30 (m, 2H), 7.03 (d,
(1.48 g, 82%), mp 149-151 oC. 1H NMR (300 MHz, DMSO-d6): δ 12.94 J = 8.1 Hz, 1H), 6.67 (dd, J = 8.1 Hz, 1.2 Hz, 1H), 6.49 (s, 1H), 6.42 (d,
(brs, 1H), 7.86 (d, J = 7.5 Hz, 1H), 7.58-7.65 (m, 5H), 7.44 (t, J = 7.5 J = 8.1 Hz, 1H), 3.72 (s, 3H); 13C NMR (75 MHz, DMSO-d6): δ 166.6,
Hz, 2H), 7.28-7.35 (m, 2H), 7.10 (d, J = 8.1 Hz, 1H), 6.97 (d, J = 8.4 160.7, 158.7, 154.7, 133.4, 131.4, 130.4, 124.6, 124.1, 121.2, 109.6,
Hz, 2H); 13C NMR (75 MHz, DMSO-d6): δ 167.0, 157.8, 155.1, 140.0, 108.5, 103.9, 55.3.
135.2, 134.2, 132.0, 129.4, 128.6, 127.6, 126.9, 125.2, 124.8, 122.0, 4-Chloro-2-phenoxybenzoic acid, 1r, Scheme 2. The same general
118.0; IR (neat): υmax 1689, 1482, 1312, 1220, 758 cm-1; HRMS (ESI, procedure was followed by using 2,4-dichlorobenzoic acid (1.18 g,
m/z) calcd. for C19H14O3Na [M + Na]+: 313.0841; found: 313.0838.
6.2 mmol, 1.0 equiv) and Phenol (1.2 g, 12.4 mmol, 2.0 equiv).
2-(Naphthalen-3-yloxy)benzoic acid, 1i, Scheme 2.9 The same Column chromatography (SiO2, eluting with 7:3 hexane/ethyl
general procedure was followed by using 2-iodo benzoic acid (1.55 acetate) afforded the desired product as a white solid, (462 mg,
g, 6.2 mmol, 1.0 equiv) and naphthalen-2-ol (1.79 g, 12.4 mmol, 2.0 30%), mp 155-157 oC. 1H NMR (300 MHz, DMSO-d6): δ 7.86 (d, J =
equiv). Column chromatography (SiO2, eluting with 7:3 8.1 Hz, 1H), 7.32-7.42 (m, 3H), 7.15 (t, J = 7.2 Hz, 1H), 6.99 (t, J = 7.8
hexane/ethyl acetate) afforded the desired product as a white solid, Hz, 3H); 13C NMR (75 MHz, DMSO-d6): δ 157.0, 156.7, 156.6, 137.8,
o
(1.31 g, 80%), mp 118-120 C. 1H NMR (300 MHz, DMSO-d6): δ 7.94 133.8, 130.5, 124.4, 124.1, 120.7, 118.6, 100.0; IR (neat): υmax 1675,
(d, J = 9.0 Hz, 1H), 7.89 (d, J = 7.5 Hz, 2H), 7.77 (d, J = 7.8 Hz, 1H), 1591, 1482, 1308, 1229, 919 cm-1; HRMS (ESI, m/z) calcd. for
7.60 (t, J = 8.1 Hz, 1H), 7.39-7.49 (m, 2H), 7.25-7.35 (m, 2H), 7.20 (s, C13H9ClO3Na [M + Na]+: 271.0138; found: 271.0125.
1H), 7.12 (d, J = 8.4 Hz, 1H); 13C NMR (75 MHz, DMSO-d6): δ 166.6, 5-Nitro-2-phenoxybenzoic acid, 1t, Scheme 2. The same general
155.6, 154.8, 134.0, 133.8, 131.6, 130.0, 129.6, 127.7, 127.0, 126.7, procedure was followed by using 2-bromo-5-nitrobenzoic acid (1.52
124.72, 124.67, 124.4, 121.5, 119.3, 112.1.
g, 6.2 mmol, 1.0 equiv) and Phenol (1.2 g, 12.4 mmol, 2.0 equiv).
Column chromatography (SiO2, eluting with 6:4 hexane/ethyl
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acetate) afforded the desired product as a white solid, (804 mg, NMR (150 MHz, CDCl3): δ 168.9, 162.2, 150.1, 136.5, 130.3, 129.6,
50%), mp 160-162 oC. 1H NMR (600 MHz, DMSO-d6): δ 8.58 (d, J = 126.4, 121.6, 119.4, 117.8, 111.8.
3.0 Hz, 1H), 8.33 (dd, J = 9.0 Hz, 3.0 Hz, 1H), 7.48 (t, J = 7.8 Hz, 2H), 4-Fluorophenyl 2-hydroxybenzoate, 2b, Scheme 2. The same
7.27 (t, J = 7.8 Hz, 1H), 7.14 (t, J = 7.8 Hz, 2H), 7.00 (d, J = 9.0 Hz, general
procedure
was
followed
by
using
2-(4-
1H); 13C NMR (150 MHz, DMSO-d6): δ 165.3, 161.5, 155.3, 142.3, fluorophenoxy)benzoic acid (23.5 mg, 0.1 mmol, 1.0 equiv), silver
130.9, 129.0, 127.4, 125.6, 123.8, 120.3, 119.2; IR (neat): υmax 1691, nitrate (0.9 mg, 0.005 mmol), potassium persulfate (40.5 mg, 0.15
1614, 1479, 1348, 1257, 745 cm-1; HRMS (ESI, m/z) calcd. for mmol, 1.5 equiv) and potassium trifluoroacetate (30.5 mg, 0.2
C13H9NO5Na [M + Na]+: 282.0378; found: 282.0401.
mmol, 2.0 equiv). Column chromatography (SiO2, eluting with 96:4
2-(4-Chlorophenoxy)-5-nitrobenzoic acid, 1u, Scheme 2. The same hexane/ethyl acetate) afforded the desired product as a colourless
1
general procedure was followed by using 2-bromo-5-nitrobenzoic oil, (12.5 mg, 54%). H NMR (600 MHz, CDCl3): δ 10.45 (s, 1H), 8.08
acid (1.52 g, 6.2 mmol, 1.0 equiv) and 4-chlorophenol (1.60 g, 12.4 (dd, J = 7.8 Hz, 1.2Hz, 1H), 7.55-7.58 (m, 1H), 7.19-7.21 (m, 2H),
mmol, 2.0 equiv). Column chromatography (SiO2, eluting with 6:4 7.14-7.17 (m, 2H), 7.06 (d, J = 8.4 Hz, 1H), 7.00 (t, J = 7.8 Hz, 1H); 13
C
hexane/ethyl acetate) afforded the desired product as a white solid, NMR (150 MHz, CDCl3): δ 168.9, 162.2, 160.5 (d, J = 244.5 Hz), 145.8
(838 mg, 46%), mp 159-161 oC. 1H NMR (600 MHz, DMSO-d6): δ 8.60 (d, J = 3.0 Hz), 136.6, 130.3, 123.1 (d, J = 7.5 Hz), 119.5, 117.9, 116.3
(d, J = 2.4 Hz, 1H), 8.35 (dd, J = 9.0 Hz, 3.0 Hz, 1H), 7.50-7.53 (m, (d, J = 24.0 Hz), 111.6; IR (neat): υmax 3230, 1692, 1504, 1300, 1182,
2H), 7.15-7.18 (m, 2H), 7.11 (d, J = 9.0 Hz, 1H); 13C NMR (150 MHz, 1064, 757 cm-1; HRMS (ESI, m/z) calcd. for C13H9FO3Na [M + Na]+:
DMSO-d6): δ 165.1, 160.9, 154.5, 142.7, 130.7, 129.3, 129.1, 127.5, 255.0433; found: 255.0451.
124.1, 121.8, 120.1; IR (neat): υmax 1707, 1478, 1345, 845 cm-1; 4-Chlorophenyl 2-hydroxybenzoate, 2c, Scheme 2.26 The same
HRMS (EI, m/z) calcd. for C13H8ClNO5Na [M]+: 315.9989; found: general
procedure
was
followed
by
using
2-(4-
315.9986.
chlorophenoxy)benzoic acid (25.0 mg, 0.1 mmol, 1.0 equiv), silver
5-methoxy-2-phenoxybenzoic acid, 1v, Scheme 2. The same nitrate (0.9 mg, 0.005 mmol), potassium persulfate (40.5 mg, 0.15
general procedure was followed by using 2-bromo-5- mmol, 1.5 equiv) and potassium trifluoroacetate (30.5 mg, 0.2
methoxybenzoic acid (1.43 g, 6.2 mmol, 1.0 equiv) and Phenol (1.2 mmol, 2.0 equiv). Column chromatography (SiO2, eluting with 96:4
g, 12.4 mmol, 2.0 equiv). Column chromatography (SiO2, eluting hexane/ethyl acetate) afforded the desired product as a white solid,
o
1
with 6:4 hexane/ethyl acetate) afforded the desired product as a (15 mg, 60%), mp 98-100 C. H NMR (300 MHz, CDCl3): δ 10.39 (s,
white solid, (760 mg, 50%), mp 142-144 oC. 1H NMR (300 MHz, 1H), 8.05 (dd, J = 8.1 Hz, 1.5 Hz, 1H), 7.52-7.58 (m, 1H), 7.42 (d, J =
DMSO-d6): δ 7.26-7.31 (m, 3H), 7.15 (dd, J = 8.7 Hz, 2.4 Hz, 1H), 8.7 Hz, 2H), 7.16 (d, J = 9.0 Hz, 2H), 7.04 (d, J = 8.4 Hz, 1H), 6.97 (t, J
6.97-7.04 (m, 2H), 6.80 (d, J = 7.8 Hz, 2H), 3.78 (s, 3H); 13C NMR (75 = 7.8 Hz, 1H); 13C NMR (75 MHz, CDCl3): δ 168.6, 162.2, 148.5,
MHz, DMSO-d6): δ 166.3, 158.8, 155.6, 147.6, 129.8, 126.0, 123.8, 136.7, 131.8, 130.3, 129.7, 123.0, 119.6, 117.9, 111.5; IR (neat): υmax
122.1, 119.5, 116.5, 115.3, 55.7; IR (neat): υmax 1692, 1598, 1482, 3256, 1686, 1486, 1304, 1195, 755 cm-1; HRMS (ESI, m/z) calcd. for
1275, 1218, 746 cm-1; HRMS (ESI, m/z) calcd. for C14H12O4Na [M + C13H9ClO3Na [M + Na]+: 271.0138; found: 271.0145.
Na]+: 267.0633; found: 267.0635.
The experimental procedure for the preparation of compound 1o, general
1p, 1q, 1j, 1s, 1w, 3a, 3b, 3c, 3d, 3e and 3f see the Electronic bromophenoxy)benzoic acid (29.5 mg, 0.1 mmol, 1.0 equiv), silver
Supplementary Information (ESI). nitrate (0.9 mg, 0.005 mmol), potassium persulfate (40.5 mg, 0.15
4-Bromophenyl 2-hydroxybenzoate, 2d, Scheme 2. The same
procedure was followed by using 2-(4-
General experimental Procedure for the carboxyl radical-assisted mmol, 1.5 equiv) and potassium trifluoroacetate (30.5 mg, 0.2
1,5-aryl migration through Smiles rearrangement using 2- mmol, 2.0 equiv). Column chromatography (SiO2, eluting with 96:4
Phenoxybenzoic acids, Scheme 2.
hexane/ethyl acetate) afforded the desired product as a white solid,
To an oven-dried 15 mL sealed tube, a mixture of 2-phenoxybenzoic (13.5 mg, 46%), mp 67-69 oC. H NMR (600 MHz, CDCl3): δ 10.40 (s,
acids (0.1 mmol, 1.0 equiv), silver nitrate (0.9 mg, 0.005 mmol), 1H), 8.07 (dd, J = 8.4 Hz, 1.2 Hz, 1H), 7.55-7.60 (m, 3H), 7.13 (d, J =
potassium persulfate (40.5 mg, 0.15 mmol, 1.5 equiv) and 9.0 Hz, 2H), 7.06 (d, J = 8.4 Hz, 1H), 6.99 (t, J = 7.2 Hz, 1H); 13C NMR
potassium trifluoroacetate (30.5 mg, 0.2 mmol, 2.0 equiv) was (150 MHz, CDCl3): δ 168.5, 162.2, 149.1, 136.7, 132.7, 130.3, 123.4,
taken and dry MeCN (2.0 mL) was added to it. After flushing with 119.5, 117.9, 111.5; IR (neat): υmax 3221, 1689, 1506, 1299, 1188,
nitrogen, the vessel was sealed with a screw cap. The reaction 1067, 755 cm-1; HRMS (EI, m/z) calcd. for C13H9BrO4 [M]+: 291.9735,
1
o
mixture was allowed to stir for 36 h at 130 C. After completion (as 293.9715; found: 291.9738, 293.9727.
indicated by TLC), the reaction mixture was cooled to room 4-Methoxyphenyl 2-hydroxybenzoate, 2e, Scheme 2.26 The same
temperature. Then the reaction mixture was poured into water (20 general
procedure
was
followed
by
using
2-(4-
mL) and extracted with ethyl acetate (20 mL). The organic layer was methoxyphenoxy)benzoic acid (24.5 mg, 0.1 mmol, 1.0 equiv), silver
washed with water (10 mL) and brine (10 mL), dried over anhydrous nitrate (0.9 mg, 0.005 mmol), potassium persulfate (40.5 mg, 0.15
Na2SO4 and the solvent was evaporated under reduced pressure. mmol, 1.5 equiv) and potassium trifluoroacetate (30.5 mg, 0.2
The crude product was purified by column chromatography using mmol, 2.0 equiv). Column chromatography (SiO2, eluting with 95:5
ethyl acetate/hexane as eluent to afford the desired product.
hexane/ethyl acetate) afforded the desired product as a colourless
1
Phenyl 2-hydroxybenzoate, 2a, Scheme 2.25 The same general oil, (14.5 mg, 60%). H NMR (600 MHz, CDCl3): δ 10.56 (s, 1H), 8.09
procedure was followed by using 2-phenoxybenzoic acid (21.5 mg, (dd, J = 7.8 Hz, 1.8 Hz, 1H), 7.54-7.57 (m, 1H), 7.13-7.16 (m, 2H),
0.1 mmol, 1.0 equiv), silver nitrate (0.9 mg, 0.005 mmol), potassium 7.06 (dd, J = 8.4 Hz, 0.6 Hz, 1H), 6.96-7.00 (m, 3H), 3.85 (s, 3H); 13
C
persulfate (40.5 mg, 0.15 mmol, 1.5 equiv) and potassium NMR (150 MHz, CDCl3): δ 169.3, 162.1, 157.6, 143.4, 136.4, 130.3,
trifluoroacetate (30.5 mg, 0.2 mmol, 2.0 equiv). Column 122.4, 119.4, 117.8, 114.6, 111.9, 55.6; IR (neat): υmax 3221, 1689,
chromatography (SiO2, eluting with 96:4 hexane/ethyl acetate) 1506, 1299, 1188, 1067, 755 cm-1; HRMS (EI, m/z) calcd. for
afforded the desired product as a colourless oil, (14 mg, 64%). 1H C14H12O4 [M]+: 244.0736; found: 244.0738.
NMR (600 MHz, CDCl3): δ 10.53 (s, 1H), 8.10 (d, J = 7.8 Hz, 1H), 7.56 4-(Benzyloxy)phenyl 2-hydroxybenzoate, 2f, Scheme 2. The same
(t, J = 8.4 Hz, 1H), 7.48 (t, J = 8.4 Hz, 2H), 7.34 (t, J = 7.2 Hz, 1H),7.24 general
(d, J = 8.4 Hz, 2H), 7.07 (d, J = 8.4 Hz, 1H), 7.00 (t, J = 7.2 Hz, 1H); 13
procedure
was
followed
by
using
2-(4-
C
(benzyloxy)phenoxy)benzoic acid (32.0 mg, 0.1 mmol, 1.0 equiv),
6 | J. Name., 2012, 00, 1-3
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silver nitrate (0.9 mg, 0.005 mmol), potassium persulfate (40.5 mg, mg, 0.005 mmol), potassium persulfate (40.5 mg, 0.15 mmol, 1.5
0.15 mmol, 1.5 equiv) and potassium trifluoroacetate (30.5 mg, 0.2 equiv) and potassium trifluoroacetate (30.5 mg, 0.2 mmol, 2.0
mmol, 2.0 equiv). Column chromatography (SiO2, eluting with 95:5 equiv). Column chromatography (SiO2, eluting with 96:4
hexane/ethyl acetate) afforded the desired product as a white solid, hexane/ethyl acetate) afforded the desired product as a colourless
1
(19.5 mg, 61%), mp 98-100 oC. 1H NMR (600 MHz, CDCl3): δ 10.56 (s, oil, (16.4 mg, 62%). H NMR (600 MHz, CDCl3): δ 10.52 (s, 1H), 8.32
1H), 8.09 (dd, J = 7.8 Hz, 1.8 Hz, 1H), 7.56 (td, J = 8.4 Hz, 1.2 Hz, 1H), (dd, J = 7.8 Hz, 1.8 Hz, 1H), 7.93-7.96 (m, 2H), 7.86 (d, J = 8.4 Hz,
7.47 (d, J = 7.2 Hz, 2H), 7.43 (t, J = 7.2 Hz, 2H), 7.37 (t, J = 7.2 Hz, 1H), 7.62-7.64 (m, 1H), 7.54-7.59 (m, 3H), 7.40 (dd, J = 7.8 Hz, 1.2
1H), 7.14-7.16 (m, 2H), 7.05-7.07 (m, 3H), 6.99 (t, J = 7.8 Hz, 1H), Hz, 1H), 7.12 (dd, J = 8.4 Hz, 0.6 Hz, 1H), 7.08 (td, J = 7.8 Hz, 1.2 Hz,
5.11 (s, 2H); 13C NMR (150 MHz, CDCl3): δ 169.2, 162.1, 156.9, 143.6, 1H); 13C NMR (150 MHz, CDCl3): δ 169.0, 162.3, 146.0, 136.7, 134.7,
136.7, 136.4, 130.3, 128.6, 128.1, 127.5, 122.4, 119.4, 117.8, 115.6, 130.4, 128.1, 126.8, 126.72, 126.67, 126.6, 125.4, 121.0, 119.6,
111.9, 70.4; IR (neat): υmax 3264, 1693, 1505, 1299, 1196, 749 cm-1; 118.2, 118.0, 111.7; IR (neat): υmax 3231, 2927, 1693, 1481, 1296,
HRMS (ESI, m/z) calcd. for C20H16O4Na [M + Na]+: 343.0946; found: 1205, 761 cm-1; HRMS (ESI, m/z) calcd. for C17H12O3Na [M + Na]+:
343.0938.
287.0684; found: 287.0669.
p-Tolyl 2-hydroxybenzoate, 2g, Scheme 2.26 The same general o-tolyl 2-hydroxybenzoate, 2k, Scheme 2.26 The same general
procedure was followed by using 2-(p-tolyloxy)benzoic acid (23.0 procedure was followed by using 2-(o-tolyloxy)benzoic acid (23.0
mg, 0.1 mmol, 1.0 equiv), silver nitrate (0.9 mg, 0.005 mmol), mg, 0.1 mmol, 1.0 equiv), silver nitrate (0.9 mg, 0.005 mmol),
potassium persulfate (40.5 mg, 0.15 mmol, 1.5 equiv) and potassium persulfate (40.5 mg, 0.15 mmol, 1.5 equiv) and
potassium trifluoroacetate (30.5 mg, 0.2 mmol, 2.0 equiv). Column potassium trifluoroacetate (30.5 mg, 0.2 mmol, 2.0 equiv). Column
chromatography (SiO2, eluting with 96:4 hexane/ethyl acetate) chromatography (SiO2, eluting with 96:4 hexane/ethyl acetate)
afforded the desired product as a colourless oil, (12.5 mg, 54%). 1H afforded the desired product as a colourless oil, (12 mg, 52%). 1H
NMR (600 MHz, CDCl3): δ 10.56 (s, 1H), 8.09 (d, J = 7.8 Hz, 1H), 7.55 NMR (600 MHz, CDCl3): δ 10.56 (s, 1H), 8.13 (dd, J = 7.8 Hz, 1.8 Hz,
(t, J = 8.4 Hz, 1H), 7.26-7.28 (m, 2H), 7.11 (d, J = 8.4 Hz, 2H), 7.06 (d, 1H), 7.57 (td, J = 9.0 Hz, 1.8 Hz, 1H), 7.31-7.33 (m, 1H), 7.29 (d, J =
J = 8.4 Hz, 1H), 6.99 (t, J = 7.8 Hz, 1H), 2.40 (s, 3H); 13C NMR (150 7.8 Hz, 1H), 7.24 (td, J = 7.8 Hz, 1.2 Hz, 1H), 7.15 (d, J = 7.8 Hz, 1H),
MHz, CDCl3): δ 169.1, 162.1, 147.8, 136.4, 136.1, 130.3, 130.1, 7.07 (dd, J = 8.4 Hz, 0.6 Hz, 1H), 7.01 (td, J = 7.8 Hz, 0.6 Hz, 1H), 2.26
121.3, 119.4, 117.8, 111.9, 20.9; IR (neat): υmax 3216, 1690, 1482, (s, 3H); 13C NMR (150 MHz, CDCl3): δ 168.7, 162.2, 148.7, 136.4,
1300, 1193, 757 cm-1; HRMS (EI, m/z) calcd. for C14H12O3 [M]+: 131.3, 130.29, 130.26, 127.1, 126.5, 121.8, 119.5, 117.8, 111.7,
228.0786; found: 228.0778.
16.2; IR (neat): υmax 3214, 2926, 1689, 1584, 1486, 1299, 1165, 753
4-Diphenyl 2-hydroxybenzoate, 2h, Scheme 2. The same general cm-1; HRMS (ESI, m/z) calcd. for C14H12O3Na [M + Na]+: 251.0684;
procedure was followed by using 2-(4-phenylphenoxy)benzoic acid found: 251.0672.
(29.0 mg, 0.1 mmol, 1.0 equiv), silver nitrate (0.9 mg, 0.005 mmol), 2-Methoxyphenyl 2-hydroxybenzoate, 2l, Scheme 2.26 The same
potassium persulfate (40.5 mg, 0.15 mmol, 1.5 equiv) and general
procedure
was
followed
by
using
2-(2-
potassium trifluoroacetate (30.5 mg, 0.2 mmol, 2.0 equiv). Column methoxyphenoxy)benzoic acid (24.5 mg, 0.1 mmol, 1.0 equiv), silver
chromatography (SiO2, eluting with 96:4 hexane/ethyl acetate) nitrate (0.9 mg, 0.005 mmol), potassium persulfate (40.5 mg, 0.15
afforded the desired product as a white solid, (15 mg, 52%), mp mmol, 1.5 equiv) and potassium trifluoroacetate (30.5 mg, 0.2
1
100-102 oC. H NMR (600 MHz, CDCl3): δ 10.53 (s, 1H), 8.12 (d, J = mmol, 2.0 equiv). Column chromatography (SiO2, eluting with 95:5
7.8 Hz, 1H), 7.68 (d, J = 7.8 Hz, 2H), 7.62 (d, J = 7.8 Hz, 2H), 7.58 (t, J hexane/ethyl acetate) afforded the desired product as a white solid,
= 7.8 Hz, 1H), 7.48 (t, J = 7.2 Hz, 2H), 7.39 (t, J = 7.2 Hz, 1H), 7.31 (d, (14 mg, 57%), mp 64-66 oC. 1H NMR (600 MHz, CDCl3): δ 10.51 (s,
J = 8.4 Hz, 2H), 7.08 ( d, J = 8.4 Hz, 1H), 7.01 (t, J = 7.2 Hz, 1H); 13C 1H), 8.13 (dd, J = 7.8 Hz, 1.2 Hz, 1H), 7.54-7.57 (m, 1H), 7.30 (td, J =
NMR (150 MHz, CDCl3): δ 169.0, 162.2, 149.4, 140.2, 139.6, 136.5, 8.4 Hz, 1.8 Hz, 1H), 7.18 (dd, J = 7.8 Hz, 1.2 Hz, 1H), 7.02-7.06 (m,
130.4, 128.8, 128.3, 127.5, 127.1, 121.9, 119.5, 117.8, 111.8; IR 3H), 6.99 (t, J = 7.8 Hz, 1H), 3.85 (s, 3H); 13C NMR (150 MHz, CDCl3):
(neat): υmax 3208, 1688, 1483, 1301, 1178, 757, 691 cm-1; HRMS δ 168.4, 162.0, 151.1, 139.0, 136.3, 130.6, 127.4, 122.8, 120.8,
(ESI, m/z) calcd. for C19H14O3Na [M + Na]+: 313.0841; found: 119.4, 117.7, 112.5, 111.8, 55.9; IR (neat): υmax 3212, 1692, 1499,
313.0856.
1296, 754 cm-1; HRMS (ESI, m/z) calcd. for C14H12O4Na [M + Na]+:
Naphthalen-2-yl 2-hydroxybenzoate, 2i, Scheme 2. The same 267.0633; found: 267.0625.
general procedure was followed by using 2-(naphthalen-3- 3-Chlorophenyl 2-hydroxybenzoate, 2m, Scheme 2. The same
yloxy)benzoic acid (26.5 mg, 0.1 mmol, 1.0 equiv), silver nitrate (0.9 general
procedure
was
followed
by
using
2-(3-
mg, 0.005 mmol), potassium persulfate (40.5 mg, 0.15 mmol, 1.5 chlorophenoxy)benzoic acid (25.0 mg, 0.1 mmol, 1.0 equiv), silver
equiv) and potassium trifluoroacetate (30.5 mg, 0.2 mmol, 2.0 nitrate (0.9 mg, 0.005 mmol), potassium persulfate (40.5 mg, 0.15
equiv). Column chromatography (SiO2, eluting with 96:4 mmol, 1.5 equiv) and potassium trifluoroacetate (30.5 mg, 0.2
hexane/ethyl acetate) afforded the desired product as a white solid, mmol, 2.0 equiv). Column chromatography (SiO2, eluting with 96:4
o
(16.5 mg, 63%), mp 86-88 C. 1H NMR (600 MHz, CDCl3): δ 10.55 (s, hexane/ethyl acetate) afforded the desired product as a colourless
1H), 8.17 (dd, J = 7.8 Hz, 1.2 Hz, 1H), 7.95 (d, J = 9.0 Hz, 1H), 7.91 (d, oil, (9.0 mg, 36%). 1H NMR (300 MHz, CDCl3): δ 10.38 (s, 1H), 8.05
J = 7.8 Hz, 1H), 7.87 (d, J = 7.8 Hz, 1H), 7.71 (d, J = 2.4 Hz, 1H), 7.52- (d, J = 8.1 Hz, 1.8 Hz, 1H), 7.56 (td, J = 8.7 Hz, 1.8 Hz, 1H), 7.39 (t, J =
7.60 (m, 3H), 7.37 (dd, J = 9.0 Hz, 2.4 Hz, 1H), 7.09 (d, J = 8.4 Hz, 1H), 7.8 Hz, 1H), 7.27-7.32 (m, 2H), 7.12-7.15 (m, 1H), 7.05 (d, J = 8.4 Hz,
7.02 (t, J = 7.8 Hz, 1H); 13C NMR (150 MHz, CDCl3): δ 169.1, 162.2, 1H), 6.98 (td, J = 8.4 Hz, 1.2 Hz, 1H); 13C NMR (75 MHz, CDCl3): δ
147.7, 136.5, 133.7, 131.7, 130.4, 129.6, 127.8, 127.7, 126.8, 126.0, 148.5, 162.2, 150.5, 136.7, 134.9, 130.32, 130.27, 126.7, 122.4,
120.9, 119.5, 118.8, 117.9, 111.8; IR (neat): υmax 3252, 1688, 1479, 120.1, 119.6, 117.9, 111.4; IR (neat): υmax 3216, 1675, 1587, 1479,
1297, 1156, 756 cm-1; HRMS (ESI, m/z) calcd. for C17H12O3Na [M + 1304, 753 cm-1; HRMS (ESI, m/z) calcd. for C13H9ClO3Na [M + Na]+:
Na]+: 287.0684; found: 287.0675.
Naphthalen-1-yl 2-hydroxybenzoate, 2j, Scheme 2. The same 3-Methoxyphenyl 2-hydroxybenzoate, 2n, Scheme 2. The same
general procedure was followed by using 2-(naphthalen-1- general procedure was followed by using 2-(3-
yloxy)benzoic acid (26.5 mg, 0.1 mmol, 1.0 equiv), silver nitrate (0.9 methoxyphenoxy)benzoic acid (24.5 mg, 0.1 mmol, 1.0 equiv), silver
271.0138; found: 271.0153.
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nitrate (0.9 mg, 0.005 mmol), potassium persulfate (40.5 mg, 0.15 808 cm-1; HRMS (ESI, m/z) calcd. for C17H11FO3Na [M + Na]+:
mmol, 1.5 equiv) and potassium trifluoroacetate (30.5 mg, 0.2 305.0590; found: 305.0598.
mmol, 2.0 equiv). Column chromatography (SiO2, eluting with 95:5 Phenyl 4-chloro-2-hydroxybenzoate, 2r, Scheme 2. The same
hexane/ethyl acetate) afforded the desired product as a colourless general procedure was followed by using 4-chloro-2-
oil, (8.5 mg, 34%). 1H NMR (300 MHz, CDCl3): δ 10.53 (s, 1H), 8.09 phenoxybenzoic acid (25.0 mg, 0.1 mmol, 1.0 equiv), silver nitrate
(dd, J = 8.1 Hz, 1.5 Hz, 1H), 7.56 (td, J = 8.7 Hz, 1.8 Hz, 1H), 7.37 (t, J (0.9 mg, 0.005 mmol), potassium persulfate (40.5 mg, 0.15 mmol,
= 8.1 Hz, 1H), 7.07 (dd, J = 7.8 Hz, 0.6 Hz, 1H), 7.00 (td, J = 8.1 Hz, 1.5 equiv) and potassium trifluoroacetate (30.5 mg, 0.2 mmol, 2.0
0.9 Hz, 1H), 6.87-6.90 (m, 1H), 6.83 (dd, J = 8.1 Hz, 1.2 Hz, 1H), 6.79 equiv). Column chromatography (SiO2, eluting with 96:4
(t, J = 2.1 Hz, 1H), 3.85 (s, 3H); 13C NMR (75 MHz, CDCl3): δ 168.8, hexane/ethyl acetate) afforded the desired product as a colourless
162.2, 160.6, 151.0, 136.5, 130.3, 130.0, 119.5, 117.8, 113.8, 112.2, oil, (14 mg, 57%). 1H NMR (600 MHz, CDCl3): δ 10.62 (s, 1H), 8.02 (d,
111.8, 107.7, 55.5; IR (neat): υmax 3224, 2927, 1691, 1610, 1486, J = 9.0 Hz, 1H), 7.46-7.49 (m, 2H), 7.34 (t, J = 7.2 Hz, 1H), 7.21-7.23
1143, 760 cm-1; HRMS (ESI, m/z) calcd. for C14H12O4Na [M + Na]+: (m, 2H), 7.09 (d, J = 2.4 Hz, 1H), 6.98 (dd, J = 8.4 Hz, 1.8 Hz, 1H); 13
267.0633; found: 267.0635. NMR (150 MHz, CDCl3): δ 168.4, 162.7, 149.9, 142.3, 131.3, 129.7,
C
Phenyl 4-fluoro-2-hydroxybenzoate, 2o, Scheme 2. The same 126.5, 121.5, 120.2, 118.0, 110.5; IR (neat): υmax 3202, 1693, 1487,
general procedure was followed by using 4-fluoro-2- 1192, 1081, 771 cm-1; HRMS (ESI, m/z) calcd. for C13H9ClO3Na [M +
phenoxybenzoic acid (23.5 mg, 0.1 mmol, 1.0 equiv), silver nitrate Na]+: 271.0138; found: 271.0151.
(0.9 mg, 0.005 mmol), potassium persulfate (40.5 mg, 0.15 mmol, Phenyl 2-hydroxy-4-nitrobenzoate, 2s, Scheme 2. The same
1.5 equiv) and potassium trifluoroacetate (30.5 mg, 0.2 mmol, 2.0 general procedure was followed by using 4-nitro-2-phenoxybenzoic
equiv). Column chromatography (SiO2, eluting with 96:4 acid (26.0 mg, 0.1 mmol, 1.0 equiv), silver nitrate (0.9 mg, 0.005
hexane/ethyl acetate) afforded the desired product as a colourless mmol), potassium persulfate (40.5 mg, 0.15 mmol, 1.5 equiv) and
oil, (13.5 mg, 58%). 1H NMR (600 MHz, CDCl3): δ 10.76 (d, J = 1.2 Hz, potassium trifluoroacetate (30.5 mg, 0.2 mmol, 2.0 equiv). Column
1H), 8.11 (dd, J = 9.0 Hz, 6.6 Hz, 1H), 7.48 (t, J = 8.4 Hz, 2H), 7.34 (t, J chromatography (SiO2, eluting with 9:1 hexane/ethyl acetate)
= 7.8 Hz, 1H), 7.22 (d, J = 7.8 Hz, 2H), 6.75 (dd, J = 10.2 Hz, J = 2.4 Hz, afforded the desired product as a yellowish solid, (13.5 mg, 52%),
1H), 6.72 (td, J = 8.4 Hz, 2.4 Hz, 1H); 13C NMR (150 MHz, CDCl3): δ mp 146-148 oC. 1H NMR (600 MHz, CDCl3): δ 10.75 (s, 1H), 8.29 (d, J
168.3, 167.7 (d, J = 255.0 Hz), 164.3 (d, J = 13.5 Hz), 149.9, 132.6 (d, = 8.4 Hz, 1H), 7.90 (d, J = 1.8 Hz, 1H), 7.81 (dd, J = 8.4 Hz, 1.8 Hz,
J = 12.0 Hz), 129.6, 126.5, 121.6, 108.6 (d, J = 3.0 Hz), 107.8 (d, J = 1H), 7.50 (t, J = 7.2 Hz, 2H), 7.37 (t, J = 7.8 Hz, 1H), 7.24-7.26 (m,
22.5 Hz), 104.6 (d, J = 24.0 Hz); IR (neat): υmax 3180, 1691, 1596, 2H); 13C NMR (150 MHz, CDCl3): δ 167.6, 162.5, 152.5, 149.6, 131.7,
1500, 1259, 1192, 771 cm-1; HRMS (ESI, m/z) calcd. for C13H9FO3Na 129.8, 126.9, 121.3, 116.6, 113.7, 113.3; IR (neat): υmax 1690, 1527,
[M + Na]+: 255.0433; found: 255.0455.
1208, 781 cm-1; HRMS (ESI, m/z) calcd. for C13H9NO5Na [M + Na]+:
p-Tolyl 4-fluoro-2-hydroxybenzoate, 2p, Scheme 2. The same 282.0378; found: 282.0354.
general procedure was followed by using 2-(p-tolyloxy)-4- Phenyl 2-hydroxy-5-nitrobenzoate, 2t, Scheme 2. The same general
fluorobenzoic acid (25.0 mg, 0.1 mmol, 1.0 equiv), silver nitrate (0.9 procedure was followed by using 5-nitro-2-phenoxybenzoic acid
mg, 0.005 mmol), potassium persulfate (40.5 mg, 0.15 mmol, 1.5 (26.0 mg, 0.1 mmol, 1.0 equiv), silver nitrate (0.9 mg, 0.005 mmol),
equiv) and potassium trifluoroacetate (30.5 mg, 0.2 mmol, 2.0 potassium persulfate (40.5 mg, 0.15 mmol, 1.5 equiv) and
equiv). Column chromatography (SiO2, eluting with 96:4 potassium trifluoroacetate (30.5 mg, 0.2 mmol, 2.0 equiv). Column
hexane/ethyl acetate) afforded the desired product as a white solid, chromatography (SiO2, eluting with 9:1 hexane/ethyl acetate)
o
(14.5 mg, 59%), mp 68-70 C. 1H NMR (600 MHz, CDCl3): δ 10.79 (d, afforded the desired product as a yellowish solid, (13 mg, 50%), mp
1
J = 1.8 Hz, 1H), 8.10 (dd, J = 9.0 Hz, 6.6 Hz, 1H), 7.26 (d, J = 8.4 Hz, 149-151 oC. H NMR (600 MHz, CDCl3): δ 11.19 (s, 1H), 9.05 (d, J =
2H), 7.10 (d, J = 8.4 Hz, 2H), 6.74 (dd, J = 10.2 Hz, 2.4 Hz, 1H), 6.71 2.4 Hz, 1H), 8.43 (dd, J = 9.0 Hz, 3.0 Hz, 1H), 7.50 (t, J = 7.8 Hz, 2H),
(td, J = 8.4 Hz, 2.4 Hz, 1H), 2.40 (s, 3H); 13C NMR (150 MHz, CDCl3): δ 7.38 (t, J = 7.8 Hz, 1H), 7.26 (d, J = 7.8 Hz, 2H), 7.18 (d, J = 9.6 Hz,
168.5, 167.6 (d, J = 253.5 Hz), 164.3 (d, J = 15.0 Hz), 147.6, 136.2, 1H); 13C NMR (150 MHz, CDCl3): δ 167.7, 166.6, 149.6, 140.2, 131.1,
132.6 (d, J = 12.0 Hz), 130.1, 121.2, 108.6 (d, J = 3.0 Hz), 107.7 (d, J = 129.8, 127.0, 126.9, 121.3, 118.9, 111.7; IR (neat): υmax 1697, 1624,
24.0 Hz), 104.6 (d, J = 24.0 Hz), 20.9; IR (neat): υmax 3082, 1685, 1514, 1333, 1194, 751 cm-1; HRMS (ESI, m/z) calcd. for C13H10NO5
1600, 1509, 1265, 1188, 767 cm-1; HRMS (ESI, m/z) calcd. for [M + H]+: 260.0559; found: 260.0574.
C14H11FO3Na [M + Na]+: 269.0590; found: 269.0556.
4-Chlorophenyl 2-hydroxy-5-nitrobenzoate, 2u, Scheme 2. The
Naphthalen-2-yl 4-fluoro-2-hydroxybenzoate, 2q, Scheme 2. The same general procedure was followed by using 2-(4-
same general procedure was followed by using 4-fluoro-2- chlorophenoxy)-5-nitrobenzoic acid (29.5 mg, 0.1 mmol, 1.0 equiv),
(naphthalen-3-yloxy)benzoic acid (28.5 mg, 0.1 mmol, 1.0 equiv), silver nitrate (0.9 mg, 0.005 mmol), potassium persulfate (40.5 mg,
silver nitrate (0.9 mg, 0.005 mmol), potassium persulfate (40.5 mg, 0.15 mmol, 1.5 equiv) and potassium trifluoroacetate (30.5 mg, 0.2
0.15 mmol, 1.5 equiv) and potassium trifluoroacetate (30.5 mg, 0.2 mmol, 2.0 equiv). Column chromatography (SiO2, eluting with 9:1
mmol, 2.0 equiv). Column chromatography (SiO2, eluting with 96:4 hexane/ethyl acetate) afforded the desired product as a white solid,
hexane/ethyl acetate) afforded the desired product as a white solid, (13 mg, 45%), mp 148-150 oC. 1H NMR (600 MHz, CDCl3): δ 11.07
(17 mg, 60%), mp 78-80 oC. 1H NMR (600 MHz, CDCl3): δ 10.77 (s, (brs, 1H), 9.02 (d, J = 2.4 Hz, 1H), 8.44 (dd, J = 9.0 Hz, 3.0 Hz, 1H),
1H), 8.17 (dd, J = 9.0 Hz, 6.6 Hz, 1H), 7.95 (d, J = 9.0 Hz, 1H), 7.91 (d, 7.46-7.48 (m, 2H), 7.20-7.23 (m, 2H), 7.18 (d, J = 9.0 Hz, 1H); 13C
J = 7.2 Hz, 1H), 7.86 (d, J = 7.8 Hz, 1H), 7.70 (d, J = 2.4 Hz, 1H), 7.52- NMR (150 MHz, CDCl3): δ 167.4, 166.6, 148.0, 140.2, 132.4, 131.3,
7.57 (m, 2H), 7.36 (dd, J = 9.0 Hz, 2.4 Hz, 1H), 6.77 (dd, J = 10.2 Hz, 129.9, 127.0, 122.7, 119.0, 111.4; IR (neat): υmax 1696, 1482, 1340,
2.4 Hz, 1H), 6.74 (td, J = 8.4 Hz, 2.4 Hz, 1H); 13C NMR (150 MHz, 1196, 723 cm-1; HRMS (EI, m/z) calcd. for C13H8ClNO5 [M]+:
CDCl3): δ 168.5, 167.8 (d, J = 255.0 Hz), 164.4 (d, J = 13.5 Hz), 147.5, 295.0061; found: 295.0059.
133.7, 132.6 (d, J = 10.5 Hz), 131.7, 129.7, 127.8, 127.7, 126.8, General experimental procedure for the carboxyl radical-assisted
126.1, 120.8, 118.8, 108.6 (d, J = 1.5 Hz), 107.8 (d, J = 22.5 Hz), 1,5-aryl migration through Smiles rearrangement using 2-
104.7 (d, J = 2.4 Hz); IR (neat): υmax 1677, 1506, 1262, 1205, 1152, (phenylthio)benzoic acids, Scheme 3.
8 | J. Name., 2012, 00, 1-3
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ARTICLE
To an oven-dried 15 mL sealed tube,
a mixture of 2- 2H), 7.85 (dd, J = 8.4 Hz, 0.6 Hz, 2H), 7.51 (td, J = 8.4 Hz, 1.2 Hz, 2H),
(phenylthio)benzoic acids (0.2 mmol, 1.0 equiv), silver nitrate (1.7 7.34 (td, J = 8.4 Hz, 1.2 Hz, 2H), 7.26 (d, J = 8.4 Hz, 4H), 7.17 (d, J =
mg, 0.01 mmol) and potassium persulfate (81 mg, 0.3 mmol, 1.5 9.0 Hz, 4H), 2.40 (s, 6H); 13C NMR (150 MHz, CDCl3): δ 165.1, 148.3,
equiv) was taken and dry MeCN (4.0 mL) was added to it. After 141.3, 135.8, 133.6, 132.0, 130.0, 126.7, 126.1, 125.6, 121.4, 20.9;
flushing with nitrogen, the vessel was sealed with a screw cap. The IR (neat): υmax 1717, 1504, 1247, 1193, 1031, 736 cm-1; HRMS (ESI,
reaction mixture was allowed to stir for 36 h at 130 oC. After m/z) calcd. for C28H22O4S2Na [M + Na]+: 509.0857; found: 509.0851.
completion (as indicated by TLC), the reaction mixture was cooled Diphenyl 6,6'-disulfanediylbis(3-bromobenzoate), 4e, Scheme 3.
to room temperature. Then the reaction mixture was poured into The same general procedure was followed by using 5-bromo-2-
water (30 mL) and extracted with ethyl acetate (40 mL). The organic (phenylthio)benzoic acid (62.0 mg, 0.2 mmol, 1.0 equiv), silver
layer was washed with water (10 mL x 2) and brine (10 mL), dried nitrate (1.7 mg, 0.01 mmol), potassium persulfate (81 mg, 0.3
over anhydrous Na2SO4 and the solvent was evaporated under mmol, 1.5 equiv). Column chromatography (SiO2, eluting with 9:1
reduced pressure. The crude product was purified by column hexane/ethyl acetate) afforded the desired product as a white solid,
chromatography using ethyl acetate/hexane as eluent to afford the (37.5 mg, 61%), mp 210-212 oC. 1H NMR (600 MHz, CDCl3): δ 8.45 (d,
desired product.
J = 2.4 Hz, 2H), 7.68 (d, J = 9.0 Hz, 2H), 7.62 (dd, J = 9.0 Hz, 2.4 Hz,
Diphenyl 2,2'-disulfanediyldibenzoate, 4a, Scheme 3. The same 2H), 7.47-7.50 (m, 4H), 7.34 (t, J = 7.2 Hz, 2H), 7.27-7.29 (m, 4H); 13
C
general procedure was followed by using 2-(phenylthio)benzoic acid NMR (150 MHz, CDCl3): δ 163.8, 150.3, 140.1, 136.6, 134.7, 129.6,
(46.0 mg, 0.2 mmol, 1.0 equiv), silver nitrate (1.7 mg, 0.01 mmol), 128.0, 127.7, 126.4, 121.5, 119.6; IR (neat): υmax 1726, 1454, 1289,
potassium persulfate (81 mg, 0.3 mmol, 1.5 equiv). Column 1241, 1193, 1077 cm-1; HRMS (ESI, m/z) calcd. for C26H16Br2O4S2Na
chromatography (SiO2, eluting with 9:1 hexane/ethyl acetate) [M + Na]+: 636.8754; found: 636.8748.
afforded the desired product as a white solid, (37.5 mg, 82%), mp Diphenyl 6,6'-disulfanediylbis(3-fluorobenzoate), 4f, Scheme 3.
104-106 oC. 1H NMR (600 MHz, CDCl3): δ 8.34 (dd, J = 7.8 Hz, 1.8 Hz, The same general procedure was followed by using 5-fluoro-2-
2H), 7.86 (dd, J = 8.4 Hz, 0.6 Hz, 2H), 7.53 (td, J = 8.4 Hz, 1.8 Hz, 2H), (phenylthio)benzoic acid (50.0 mg, 0.2 mmol, 1.0 equiv), silver
7.46-7.49 (m, 4H), 7.29-7.36 (m, 8H); 13C NMR (150 MHz, CDCl3): δ nitrate (1.7 mg, 0.01 mmol), potassium persulfate (81 mg, 0.3
164.9, 150.6, 141.4, 133.7, 132.0, 129.6, 126.6, 126.14, 126.07, mmol, 1.5 equiv). Column chromatography (SiO2, eluting with 9:1
125.7, 121.7; IR (neat): υmax 1718, 1488, 1246, 1194, 1036, 743 cm-1; hexane/ethyl acetate) afforded the desired product as a white solid,
HRMS (ESI, m/z) calcd. for C26H18O4S2Na [M + Na]+: 481.0544; (29.5 mg, 60%), mp 153-155 oC. 1H NMR (600 MHz, CDCl3): δ 8.02
found: 481.0548.
(dd, J = 8.4 Hz, 2.4 Hz, 2H), 7.79 (dd, J = 9.0 Hz, 4.8 Hz, 2H), 7.45-
Diphenyl 2,2'-disulfanediylbis(4-fluorobenzoate), 4b, Scheme 3. 7.48 (m, 4H), 7.32 (t, J = 7.2 Hz, 2H), 7.23-7.27 (m, 6H); 13C NMR
The same general procedure was followed by using 4-fluoro-2- (150 MHz, CDCl3): δ 163.9 (d, J = 1.5 Hz), 160.8 (d, J = 246.0 Hz),
(phenylthio)benzoic acid (50.0 mg, 0.2 mmol, 1.0 equiv), silver 150.3, 136.2 (d, J = 3.0 Hz), 129.6, 128.0 (d, J = 7.5 Hz), 127.9 (d, J =
nitrate (1.7 mg, 0.01 mmol), potassium persulfate (81 mg, 0.3 6.0 Hz), 126.4, 121.5, 121.2 (d, J = 22.5 Hz), 118.7 (d, J = 24.0 Hz); IR
mmol, 1.5 equiv). Column chromatography (SiO2, eluting with 9:1 (neat): υmax 1727, 1460, 1243, 1193, 1029, 739 cm-1; HRMS (ESI,
hexane/ethyl acetate) afforded the desired product as a white solid, m/z) calcd. for C26H16F2O4S2Na [M
(33.5 mg, 68%), mp 122-124 oC. 1H NMR (600 MHz, CDCl3): δ 8.37 517.0360.
(dd, J = 8.4 Hz, 6.0 Hz, 2H), 7.55 (dd, J = 9.6 Hz, 2.4 Hz, 2H), 7.45-
+
Na]+: 517.0356; found:
7.48 (m, 4H), 7.31 (t, J = 7.2 Hz, 2H), 7.26-7.27 (m, 4H), 7.02-7.05
(m, 2H); 13C NMR (150 MHz, CDCl3): δ 166.1 (d, J = 256.5 Hz), 164.1,
150.4, 144.8 (d, J = 9.0 Hz), 134.8 (d, J = 9.0 Hz), 129.6, 126.3, 122.8
Acknowledgements
RJ thanks DST, SERB, Govt. of India for Ramanujan fellowship;
award no. SR/S2/RJN-97/2012 and extra mural research grant no.
EMR/2014/000469 for financial support. AH thanks CSIR, for his
fellowship.
(d, J = 3.0 Hz), 121.7, 113.4 (d, J = 22.5 Hz), 113.1 (d, J = 27.0 Hz); IR
(neat): υmax 1720, 1578, 1481, 1250, 1189, 1075, 746 cm-1; HRMS
(ESI, m/z) calcd. for C26H16F2O4S2Na [M + Na]+: 517.0356; found:
517.0336.
Bis(4-chlorophenyl) 2,2'-disulfanediyldibenzoate, 4c, Scheme 3.
The same general procedure was followed by using 2-(4-
chlorophenylthio)benzoic acid (53.0 mg, 0.2 mmol, 1.0 equiv), silver
nitrate (1.7 mg, 0.01 mmol), potassium persulfate (81 mg, 0.3
mmol, 1.5 equiv). Column chromatography (SiO2, eluting with 9:1
hexane/ethyl acetate) afforded the desired product as a white solid,
(33 mg, 63%), mp 160-162 oC. 1H NMR (600 MHz, CDCl3): δ 8.31 (dd,
J = 7.8 Hz, 1.2 Hz, 2H), 7.85 (d, J = 8.4 Hz, 2H), 7.53 (td, J = 8.4 Hz,
1.2 Hz, 2H), 7.43 (d, J = 9.0 Hz, 4H), 7.35 (t, J = 7.2 Hz, 2H), 7.24 (d, J
= 8.4 Hz, 4H); 13C NMR (150 MHz, CDCl3): δ 164.6, 149.0, 141.4,
133.9, 132.1, 131.6, 129.6, 126.2, 126.1, 125.8, 123.1; IR (neat): υmax
1720, 1485, 1248, 1199, 1036, 736 cm-1; HRMS (ESI, m/z) calcd. for
C26H16Cl2O4S2Na [M + Na]+: 548.9765; found: 548.9767.
Di-p-tolyl 2,2'-disulfanediyldibenzoate, 4d, Scheme 3. The same
general procedure was followed by using 2-(p-tolylthio)benzoic acid
(49.0 mg, 0.2 mmol, 1.0 equiv), silver nitrate (1.7 mg, 0.01 mmol),
potassium persulfate (81 mg, 0.3 mmol, 1.5 equiv). Column
chromatography (SiO2, eluting with 9:1 hexane/ethyl acetate)
afforded the desired product as a white solid, (29 mg, 60%), mp
147-149 oC. 1H NMR (600 MHz, CDCl3): δ 8.32 (dd, J = 7.8 Hz, 1.2 Hz,
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