Oxidative-substitution reactions of polycyclic aromatic hydrocarbons with iodine(III) sulfonate reagents

Article abstract of DOI:10.1016/j.tetlet.2006.07.114

Polycyclic aromatic hydrocarbons (PAH) undergo regioselective oxidative-substitution reactions with iodine(III) sulfonate reagents in dichloromethane to give the corresponding aryl sulfonate esters. The use of [hydroxy(tosyloxy)iodo]benzene in conjunction

Full text of DOI:10.1016/j.tetlet.2006.07.114

Tetrahedron Letters 47 (2006) 7011–7015
Oxidative-substitution reactions of polycyclic
aromatic hydrocarbons with iodine(III) sulfonate reagents
Gerald F. Koser,a,* Sanjay Telua and Kenneth K. Laalib
aDepartment of Chemistry, The University of Akron, Akron, OH 44325-3601, USA
bDepartment of Chemistry, Kent State University, Kent, OH 44242, USA
Received 30 June 2006; revised 17 July 2006; accepted 21 July 2006
Abstract—Polycyclic aromatic hydrocarbons (PAH) undergo regioselective oxidative-substitution reactions with iodine(III) sulfo-
nate reagents in dichloromethane to give the corresponding aryl sulfonate esters. The use of [hydroxy(tosyloxy)iodo]benzene in con-
junction with trimethylsilyl isothiocyanate leads to thiocyanation of the PAH nucleus.
ꢀ 2006 Elsevier Ltd. All rights reserved.
The capacity of phenyliodine(III) bis(trifluoroacetate),
PIFA, to promote oxidative-substitution and oxidative-
coupling reactions of electron-rich aromatic compounds
through arene radical–cation intermediates has been
amply demonstrated over the past 15 years. For exam-
ple, PIFA oxidations of aromatic ethers in (CF3)2-
CHOH permit the introduction of selected nucleophiles
into the aromatic nucleus; Eq. 1.1–4 The nature of the
solvent is crucial to the success of these two-electron
oxidation–reduction reactions. It has been shown, for
example, that the use of CH2Cl2 instead of
(CF3)2CHOH reduces the yields of nuclear substitution
products to trace levels or less.2,4
polymethylbenzenes with Me3SiN3,1 nuclear cyanations
of thiophenes, pyrroles, and indoles with Me3SiCN,5
and heterocyclizations of aromatic ethers containing
alkylsulfanyl sidechains.6 When nucleophiles are not
available, oxidative-coupling occurs. Hence, thio-
phenes,7,8 polyalkylbenzenes,9 and aromatic ethers10
are converted to biaryl products with BF3—activated
PIFA in CH2Cl2. Intramolecular coupling reactions of
this type provide access to various benzo-annulated
heterocyclic compounds.11
We know of one reported example of aryl trifluoroace-
tate formation during PIFA oxidations of aromatic
compounds; namely, EPR observation of the 9-triflu-
oroacetoxyanthracene radical–cation when anthracene
was treated with PIFA in trifluoroacetic acid at
ꢀ11 ꢁC.12 Other polycyclic aromatic hydrocarbons such
as pyrene, perylene, pentacene, and 9,10-dimethyl-
anthracene gave unsubstituted radical–cations (ArHÅ+)
under the same conditions.12
OR
Me3SiNu
or
NuH
OR
OR
H
Nu
H
PhI(OCOCF3)2
(CF3)2CHOH
PhI
+
R'
R'
R'
( )n
(n = 1, 2)
(-Nu = -N , -NCS, -SPh, -OAc); NuH = ArSH,
Me3SiNu
O
O
3
H3C
H
In contrast to PIFA, the use of iodine(III) sulfonate re-
agents, ArI(OH)OSO2R, for nuclear oxidations of aro-
matic substrates has been little explored. Indeed,
whereas benzene and toluene are unreactive with PhI(O-
H)OTs, electron-rich aromatics (e.g., anisole, thio-
phenes, trimethylsilylarenes, and trimethylsilylfurans)
undergo electrophilic substitution reactions with ArI-
(OH)OTs, leading to iodonium salts Ar(Ar0)I+ ꢀOTs.13
ð1Þ
The treatment of PIFA with Et2OÆBF3 affords a more
reactive iodine(III) species, and, in this case, CH2Cl2 is
the solvent of choice. These conditions have been em-
ployed for nuclear azidations of naphthalene and
*
We now report that iodine(III) sulfonates undergo
direct oxidative-substitution reactions with polycyclic
Corresponding author. Tel.: +1 330 972 6066; fax: +1 330 972
7370; e-mail: koser@uakron.edu
0040-4039/$ - see front matter ꢀ 2006 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tetlet.2006.07.114

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G. F. Koser et al. / Tetrahedron Letters 47 (2006) 7011–7015
aromatic hydrocarbons. This was discovered when an
attempt to phenyliodinate 2,7-di-tert-butylpyrene (1,
2,7-DTBP) with [hydroxy(tosyloxy)iodo]benzene (2a,
HTIB) gave 1-tosyloxy-2,7-di-tert-butylpyrene (3a) in-
stead. Similar treatment of 2,7-di-tert-butylpyrene with
the phenyl k3-iodanes 2b–2d, containing mesylate
(OMs), (+)-10-camphorsulfonate (OCs), and 2,4-dini-
trobenzenesulfonate (ODNs) ligands, led regioselec-
tively to the 1-sulfonyloxy-2,7-DTBP derivatives 3b–3d
shown in Eq. 2 and Table 1. These reactions proceed
readily in CH2Cl2 at room temperature and do not re-
quire activation of the iodine(III) reagent.
The structures of 3a–d, including the location of the sul-
1
fonate group, are clearly evident by H and 13C NMR
analysis. For example, in addition to two tert-butyl sing-
lets (d 1.59 and 1.73) and one methyl singlet (d 3.43) in
the aliphatic region, the 1H spectrum (300 MHz, CDCl3)
of 3b features a 2H AB multiplet at d 8.02 (H-4 and H-
5), 1H doublets at d 8.13 (J = 9.3 Hz, H-9) and d 8.48
(J = 9.5 Hz, H-10), a 2H ‘singlet’ at d 8.23 (H-6 and
H-8) and a 1H singlet at d 8.28 (H-3).15 Furthermore,
the structures of the tosylate,16 mesylate,17 and cam-
phorsulfonate16 analogs were established unequivocally
by single crystal X-ray analysis.
OSO2R
OH
CH2Cl2
rt
Ph
I
+
OSO2R
ð2Þ
3
1
2
a (-OTs, R = 4-MeC6H4)
b
c
(-OCs, R = (1R)-10-camphoryl)
(-OMs, R = Me)
d
(-ODNs, R = 2,4-(NO2)2C6H3)
OTs
The yields of 3a–d (and all other oxidative-substitution
products) reported herein are based on chromatograph-
ically isolated compounds, sometimes after further puri-
fication by recrystallization. For example, in one
experiment, a mixture of 2,7-DTBP (0.315 g, 1.0 mmol)
and 2a (0.432 g, 1.1 mmol) in CH2Cl2 (20 mL) was stir-
red magnetically under N2 for 45 min at room tempera-
ture. After aqueous workup (H2O; 5% NaHCO3;
MgSO4) and solvent removal, a red oil (0.72 g) contain-
ing PhI was obtained. Column chromatography of the
oil on silica gel with 10–25% CH2Cl2 in hexanes gave
a pale-yellow solid (0.371 g). Recrystallization of this
material from methanol returned 1-tosyloxy-2,7-DTBP
as a white solid; yield, 0.329 g (68%); mp 175.5–
176.5 ꢁC.
CH2Cl2 (150 mL)
PhI(OH)OTs
(0.55 mmol)
+
(0.50 mmol)
21%
ð3Þ
The starting concentrations of 2,7-DTBP in the forego-
ing experiments ranged from about 0.03 to 0.07 M and
provided good yields of the oxidative-substitution prod-
ucts. However, when 2a was added to a 0.05 M solution
of parent pyrene in CH2Cl2, p-toluenesulfonic acid and a
highly insoluble olive-green solid co-precipitated. Treat-
ment of the mixture with acetone (under reflux) allowed
separation of the individual components in 78% (TsOHÆ
H2O) and 75% (by mass) yields, respectively. The
insoluble solid did not melt at temperatures up to
300 ꢁC and, based on comparison of its solid-state 13C
NMR spectrum with that of pyrene,18 appears to be a
mixture of pyrene oligomers. Column chromatography
(silica gel; hexanes, 5–10% EtOAc–hexanes) of the oil
recovered from the filtrate gave 1-tosyloxypyrene in
7% yield. When 2a was allowed to react with a more
dilute solution of pyrene (C0 = 3.3 · 10ꢀ3 M), the oligo-
meric material was still produced, but in this case, 1-
tosyloxypyrene was isolated in 21% yield (Eq. 3) and
identified by single crystal X-ray analysis.16
Table 1. Reactions of 2,7-di-tert-butylpyrene with iodine(III) sulfonate
reagents in CH2Cl2 at rt
Reactantsa (mmol)
CH2Cl2 (mL),
time (h)
OSO2R
Product,
yieldb (%)
1 (1.0), 2a (1.2)
1 (1.0), 2a (1.1)
1 (1.0), 2a (1.1)
1 (1.0), 2b (1.2)
1 (0.64), 2b (0.70)
1 (0.65), 2c (0.72)
1 (0.64), 2c (0.70)
1 (1.0), 2d (1.2)
20, 24
20, 0.75
15, 0.5
15, 17
15, 1.7
15, 17
20, 1.5
30, 3
OTs
OTs
OTs
OMs
OMs
OCs
OCs
ODNs
3a, 82c
3a, 68
3a, 65
3b, 64d
3b, 63
3c, 67e (77)
3c, 50 (59)
3d, 73f
Whether oxidative-substitution reactions of this type ex-
tend to other polycyclic ring systems was tested by the
treatment of anthracene, phenanthrene, and perylene
with selected iodine(III) sulfonate reagents in CH2Cl2.
In these exploratory studies, starting concentrations of
the substrates were in the range 0.02–0.10 M and dilu-
tion effects were not examined. As shown in Table 2,
all three hydrocarbons were converted regioselectively
to the indicated sulfonate derivatives, although the
yields of the 9-anthryl sulfonates were limited by the
a Rounded-off to two significant figures.
b Isolated yields; The yields in parentheses are corrected for recovered
hydrocarbon.
c Anal. Calcd for C31H32O3S: C, 76.82; H, 6.66; found: C, 76.47; H,
6.71;14 mp 180–181 ꢁC.
d Anal. Calcd for C25H28O3S: C, 73.50; H, 6.91; found: C, 73.08; H,
6.93; mp 209–211 ꢁC.
e Anal. Calcd for C34H40O4S: C, 74.96; H, 7.40; found: C, 74.90; H,
7.33; mp 146–150 ꢁC.
f Mp 184–186 ꢁC (dec).

G. F. Koser et al. / Tetrahedron Letters 47 (2006) 7011–7015
7013
Table 2. Reactions of anthracene, phenanthrene, and perylene with iodine(III) sulfonate reagents in CH2Cl2 at rt
Reactantsa (mmol)
CH2Cl2 (mL), time
20, 0.75 h
Product, yieldb (%)
c
O
OTs
, 2a
(1.2)
(1.0)
2
H
21.5
43.5
O
d
OMs
, 2b
50, 3 h
2
H
(1.0)
(1.2)
33
24
e
OTs
, 2a
25, ca. 4 d
60 (66)
(1.0)
(1.2)
f
OMs
, 2b
25, 4 d
54 (62)
(1.0)
(1.2)
g
OCs
, 2c
10, ca. 5 d
41 (55)
(1.0)
(1.2)
h
, 2a
TsO
44 (55)
10, 1 h
(0.50)
(0.60)
a Rounded-off to two significant figures.
b Isolated yields; The yields in parentheses are corrected for recovered hydrocarbon.
c
Mp 164–166 ꢁC.
d
Anal. Calcd for C15H12O3S: C, 66.16; H, 4.44; found: C, 66.13; H, 4.58; mp 176–177 ꢁC.
Anal. Calcd for C21H16O3S: C, 72.39; H, 4.63; found: C, 72.33; H, 4.64; mp 155–156 ꢁC.
Anal. Calcd for C15H12O3S: C, 66.16; H, 4.44; found: C, 66.30; H, 4.52; mp 111–112 ꢁC.
Mp 99.5–101 ꢁC.
e
f
g
h
Mp 200–202 ꢁC (dec).
competing formation of bianthronyl. Phenanthrene re-
acts more slowly with 2 than the other ring systems,
but this had little or no effect on product yields. Finally,
in addition to NMR (1H, 13C) characterization of the
sulfonate products shown in Table 2, single crystal X-
ray structures of the tosylate derivative of perylene
and the mesylate derivatives of anthracene and phenan-
threne were determined.16
accomplished by treatment of the hydrocarbons with
2a (HTIB) in the presence of a 5-fold excess of trimeth-
ylsilyl isothiocyanate. In view of significant bianthronyl
production during direct reactions of anthracene with 2a
and b, the high yield of 9-thiocyanatoanthracene when
Me3SiNCS is available is noteworthy. However, a simi-
lar attempt to prepare the thiocyanate derivative of
phenanthrene was unsuccessful.
The possibility that iodine(III) sulfonate reagents might
be employed without activation in CH2Cl2 for the intro-
duction of external nucleophiles into polycyclic aro-
matic hydrocarbons was demonstrated by the
conversion of anthracene, perylene, and 2,7-DTBP to
the thiocyanato derivatives shown in Table 3. This was
We finally report that PIFA reacts with 2,7-DTBP in
CH2Cl2 to give the trifluoroacetate derivative shown in
Table 3, the structure of which was verified by single
crystal X-ray analysis.17 A mechanism for the oxysulf-
onylation of polycyclic aromatic hydrocarbons with
iodine(III) sulfonate reagents has not yet been

7014
G. F. Koser et al. / Tetrahedron Letters 47 (2006) 7011–7015
Table 3. Thiocyanation and trifluoroacetoxylation of polycyclic aromatic hydrocarbons with iodine(III) reagents in CH2Cl2
Reactantsa (mmol)
CH2Cl2 (mL), time
20c
Product, yieldb (%)
S
C
Nd
,2a, Me3SiNCS
(5.0)
(1.2)
(1.0)
84
S
C
Ne
2a
, Me3SiNCS
,
10, 5 h
(0.60)
(2.5)
48, (65)
(0.50)
S
C
Ng
,2a, Me3SiNCS
10f
(2.5)
(0.50)
(0.60)
89
OCOCF3
, PhI(OCOCF3)2
30, 20 h
10, 2.7 h
(3.5)
(3.1)
(0.50)
73.5
71h
(0.55)
a Rounded-off to two significant figures.
b Isolated yields; The yields in parentheses are corrected for recovered hydrocarbon.
c 1.5 h at 0 ꢁC, overnight at rt.
d Anal. Calcd for C15H9NS: C, 76.56; H, 3.86; found: C, 76.26; H, 4.05; mp 182.5–184 ꢁC.
e HRMS Calcd for C21H11NS+Na: 332.0510; found: 332.0504; mp 180.5–182 ꢁC.
f
0.5 h at 0 ꢁC, 24 h at rt.
g Anal. Calcd for C25H25NS: C, 80.82; H, 6.78; found: C, 80.92; H, 7.11; mp 118–120 ꢁC.
h Anal. Calcd for C26H25F3O2: C, 73.22; H, 5.91; found: C, 72.86; H, 5.88; mp 123–126 ꢁC.
H
H
SET
OSO2R
OH
PhI(OH)OSO2R
+
I
Ph
OSO2R
OH
OSO2R
OSO2R
H
OH
I
H
I
Ph
SET
Ph
PhI + H2O
Scheme 1.
4. Kita, Y.; Takada, T.; Mihara, S.; Whelan, B. A.; Tohma,
H. J. Org. Chem. 1995, 60, 7144–7148.
5. Dohi, T.; Morimoto, K.; Kiyono, Y.; Tohma, H.; Kita, Y.
Org. Lett. 2005, 7, 537–540.
established. However, based on analogy with PIFA, the
radical–cation mechanism shown in Scheme 1 seems
plausible, and is suggested as a preliminary model.
6. Kita, Y.; Egi, M.; Ohtsubo, M.; Saiki, T.; Takada, T.;
Tohma, H. Chem. Commun. 1996, 2225–2226.
7. Tohma, H.; Iwata, M.; Maegawa, T.; Kiyono, Y.;
Maruyama, A.; Kita, Y. Org. Biomol. Chem. 2003, 1,
1647–1649.
8. Dohi, T.; Morimoto, K.; Kiyono, Y.; Maruyama, A.;
Tohma, H.; Kita, Y. Chem. Commun. 2005, 2930–2932.
9. Tohma, H.; Iwata, M.; Maegawa, T.; Kita, Y. Tetrahedron
Lett. 2002, 43, 9241–9244.
References and notes
1. Kita, Y.; Tohma, H.; Inagaki, M.; Hatanaka, K.; Yakura,
T. Tetrahedron Lett. 1991, 32, 4321–4324.
2. Kita, Y.; Tohma, H.; Hatanaka, K.; Takada, T.; Fujita,
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1994, 116, 3684–3691.
3. Kita, Y.; Takada, T.; Mihara, S.; Tohma, H. Synlett 1995,
211–212.
10. Tohma, H.; Morioka, H.; Takizawa, S.; Arisawa, M.;
Kita, Y. Tetrahedron 2001, 57, 345–352.

G. F. Koser et al. / Tetrahedron Letters 47 (2006) 7011–7015
7015
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See pp 244–250 and references cited therein.
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Scand. 1995, 49, 640–644.
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14. The elemental analyses reported herein were performed by
Galbraith Laboratories, Inc., Knoxville, TN; Microanal-
ysis Laboratory, University of Illinois, Urbana, IL; or
Midwest Microlab, LLC, Indianapolis, IN.
15. The proton assignments are based on analysis of the
COSY and NOESY spectra of 3b. The spectra were
recorded by Silapong Baiagern at The University of
Akron on a 400 MHz Spectrometer (Inova 400).
16. Semih Durmus and Wiley J. Youngs; The University of
Akron, unpublished results.
17. Jered C. Garrison and Wiley J. Youngs; The University of
Akron, unpublished results.
18. The solid-state 13C NMR spectra were recorded by Todd
A. Wagler at The University of Akron.