Arylation of diorganochalcogen compounds with diaryliodonium triflates: Metal catalysts are unnecessary

Article abstract of DOI:10.1021/ol503177q

Diaryliodonium triflates transfer an aryl group to the chalcogen atom of organic sulfides, selenides, and tellurides (but not ethers), in the absence of transition-metal catalyst, simply upon heating in chloroform or dichloroethane solution.

Full text of DOI:10.1021/ol503177q

Letter
pubs.acs.org/OrgLett
Arylation of Diorganochalcogen Compounds with Diaryliodonium
Triflates: Metal Catalysts Are Unnecessary
Leanne Racicot, Takahito Kasahara, and Marco A. Ciufolini*
́
Department of Chemistry, The University of British Columbia, 2036 Main Mall, Vancouver, BC V6T 1Z1, Canada
S
* Supporting Information
ABSTRACT: Diaryliodonium triflates transfer an aryl group to
the chalcogen atom of organic sulfides, selenides, and tellurides
(but not ethers), in the absence of transition-metal catalyst, simply
upon heating in chloroform or dichloroethane solution.
iaryliodonium species (λ3-iodanes)1 S-arylate diaryl
sulfides in the presence of a catalytic amount of Cu(II),2
upon reaction with diaryliodanes under much gentler
conditions. Especially electrophilic λ3-iodanes such as (alkynyl)-
aryliodonium agents transfer the alkynyl (but not the aryl)
ligand to diorganochalcogen substrates under mild conditions
and with no need for catalysts, though probably by a
mechanism that differs from the one depicted in Scheme 1.9
Tangentially related to the reaction of interest here is the
uncatalyzed arylation of anilines10 and phosphines.11 The latter
process, however, seemingly proceeds through SET, rather than
nucleophilic, mechanisms.
We now report that diaryliodonium triflates arylate diaryl
chalcogenide substrates under mild conditions and without the
need for metallic catalysts. Thus, Ph3SOTf was formed in 92%
yield upon heating a chloroform- or 1,2-dichloroethane (DCE)
solution of Ph2S and Ph2IOTf to 120 °C (oil bath temperature,
tube sealed with a gasketed Teflon screwcap; Table 1, entries a
and b). Diverse aryl sulfides were found to undergo the
reaction, regardless of whether electron-donating or electron-
withdrawing groups were present on the aromatic rings (Table
1, entries d−f). In all cases, the reaction mixtures remained
D
leading to the formation of triarylsulfonium salts. These
materials find application in diverse areas of contemporary
chemistry.3 On the other hand, it has recently been determined
that diaryliodonium triflates undergo metathesis with particular
aryl iodides in the absence of any metal catalysts, seemingly by
nucleophilic attack of the I atom of the incoming Ar−I onto the
iodonium center, followed by reductive elimination of a
nucleofugal aryl iodide from the resulting complex.4 The S-
atom of an organic sulfide, and indeed the chalcogen atom in a
generic diorgano chalcogenide, would be anticipated to be
much more nucleophilic than the I atom of an aryl iodide. The
question then arises of whether diaryliodonium triflates may
arylate organochalcogen centers in the absence of any metal
catalyst and under mild conditions, leading to triorganochalco-
genonium salts, perhaps by the mechanism of Scheme 1.5 This
process would not be of mere academic interest: a Cu-free
route to triarylsulfonium triflates of technological significance3
could be economically advantageous.
Table 1. Metal-Free S-Arylation of Diaryl Sulfides
Scheme 1. Possible Metal-Free Synthesis of
Triarylchalcogenium Triflates
b
entry
Ar1
Ar2
Ar3
yield of 3 (%)
a
b
c
d
e
f
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
92
c
92
4-BrC6H4−
Ph
96
87
79
85
4-MeOC6H4-
4-BrC6H4−
Ph
4-MeOC6H4−
4−BrC6H4−
4-O2NC6H4−
4-BrC6H4−
Ph
a
In the past, the uncatalyzed arylation of diorganochalcogen
centers with diaryl-λ3-iodanes had been achieved only under
forcing conditions. For instance, Ph2S and Ph2IBF4 reacted in
the absence of catalysts to form Ph3SBF4 but only upon
prolonged heating (35 h) at temperatures above 180 °C (ca.
65% yield).6 Such harsh conditions may not be beneficial to the
survival of more sensitive sulfonium salts. Anionic chalcogen
nucleophiles, such as sulfinates7 and phenoxides,8 are, of course,
considerably more reactive and undergo uncatalyzed arylation
Conditions: 0.1 M solution of Ar2IOTf (1.0 equiv) in (CH2Cl)2, 1.5
equiv of diaryl sulfide, thick-walled glass tube sealed with a Teflon
screwcap and immersed in an oil bath maintained at 120 °C, 15 h.
b
Percent yield after silica gel column chromatography (gradient 10%
c
→ 40% acetone−CH2Cl2) to remove nonpolar byproducts. This
reaction was run in CHCl3 as the solvent.
Received: October 31, 2014
Published: December 10, 2014
© 2014 American Chemical Society
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Letter
colorless throughout the course of the reaction, indicating that
the intervention of charge-transfer complexes, and possibly of
SET events, is unlikely, i.e., that the reaction probably occurs by
a nucleophilic mechanism.
transferred a methyl group to unreacted thioanisole to produce
phenyl dimethylsulfonium triflate 9 and diaryl sulfide 10
(Scheme 2). After 9 h at 120 °C, compounds 8 and 9 were
As observed earlier in the iodonium metathesis case,4
attempts to carry out the reaction in alternative solvents, such
as MeCN, THF, or CH2Cl2, were uniformly unsuccessful.
Furthermore, no S-arylation of Ph2S occurred when Ph2IOTf
was replaced with diphenyliodonium tetrafluoroborate, hexa-
fluorophosphate, tosylate, or chloride (no reaction with the
Scheme 2. Reactions of Thioanisole Substrates
−
−
BF4 or PF6 salts; thermal degradation of the iodonium
species with the TsO− or Cl− salts).
Experiments aiming to probe the aryl group transfer
preference from mixed diaryliodonium species to diphenyl
sulfide revealed a diminished selectivity relative to analogous
iodonium metathesis reactions (Table 2). Still, the triaryl
Table 2. Aryl Group Transfer Selectivity
present in a ratio of 1.0:6.7. Analogous methyl group transfer
steps have been observed during the alkynylation of
thioanisole9 and are attributable to a thermodynamically
favorable displacement of a less nucleophilic diorganosulfur
species (10) by a more nucleophilic one (7). While nonpolar
materials such as 7 and 10 were easily separated from the
mixture of sulfonium salts, the latter was not as readily resolved
into the components and was therefore characterized as such.
In a like manner, 4-bromothioanisole, 11, reacted with Ph2IOTf
to produce sulfonium salt 12, which transferred a methyl group
to unreacted 11 to furnish 13. The rate of this second reaction
was noticeably slower than that of 8 with 7 and prolonged
heating was required to attain a significant degree of conversion
of 12 into 13. After 31 h at 120 °C, MeOTf, 14, also became
apparent in the reaction mixture [1H NMR (CDCl3): δ = 4.2
ppm]. After 48 h at 120 °C, compounds 12, 13, and 14 were
present in a ratio of 1.0:9.1:1.8. We note that the formation of
MeOTf by reaction of triflate ion with a methyl diarylsulfonium
species is documented.2b The foregoing methyl group transfer
reactions are interesting from a physical organic standpoint,12
but in the present context they constitute a complication, which
dissuaded us from carrying out more work with thioanisole or
other aryl alkyl sulfides.
Diphenyl sulfoxide failed to react with Ph2IOTf. Likewise, all
attempts to induce the O-arylation of diphenyl ether, leading to
triaryloxonium salts, met with failure. However, the arylation
reactions of diphenyl selenide and telluride were successful
(Table 3). The reaction of Ph2Se with Ph2IOTf occurred at a
rate comparable to that of Ph2S and produced Ph3SeOTf in
94% yield. In the past, this selenonium species had been
obtained in lower yield from the same starting materials in the
presence of a catalytic amount of copper benzoate.13 This
suggests that Cu salts may actually constitute a liability in the
present case.
c
ratio
b
yield of 5 + 6
entry
Ar1
Ar2
5:6
(%)
a
4-O2NC6H4−
4-MeO2CC6H4− Ph
4-O2NC6H4−
2-thienyl
Ph
1:2.3
1:1.9
1:1.3
1:3.8
1:3.9
98
94
92
82
85
b
c
4-MeOC6H4−
Ph
d
e
2-thienyl
4-MeO2CC6H4−
a
0.1 M solution of Ar2IOTf (1.0 equiv) in (CH2Cl)2, 1.5 equiv of
diphenyl sulfide, thick-walled glass tube sealed with a Teflon screwcap
and immersed in an oil bath maintained at 120 °C, 15 h. Molar ratios
calculated by integration of H NMR spectra of the crude reaction
b
1
c
mixtures. Percent yield after silica gel column chromatography
(gradient 10% → 40% acetone−CH2Cl2) to remove nonpolar
byproducts. The stated value is the sum of the yields of individual
compounds present in the product mixture. A comparison of 1H NMR
spectra of crude and purified reaction mixtures indicated that
insignificant changes in the ratio of sulfonium triflate products had
occurred upon chromatography.
sulfonium triflates arising from displacement of the more
nucleofugal aryl iodide4 were the dominant products. The
lower degree of selectivity observed in these reactions may be
due to the fact that a portion of the diaryl sulfide reacts with the
iodonium species by an SNAr mechanism, on account of the
increased nucleophilic character of divalent sulfur relative to
monovalent iodine. As detailed elsewhere,4 the SNAr mecha-
nism and the metathesis mechanism depicted in Scheme 1
promote opposite aryl group transfer selectivity.
Especially significant interference from the SNAr mechanism
would be anticipated with nitro-substituted iodonium salts.
Indeed, unusually poor selectivity was observed in the reaction
of (4-anisyl)-4-nitrophenyliodonium triflate with diphenyl
sulfide (Table 2, entry c).
The separation of products 5 and 6 proved to be less than
straightforward due to their very similar chromatographic
mobilities. Some separation was achieved for entries a−c but
not for the thienyl sulfonium salts (entries d and e). Therefore,
the yields reported in the table are those of the mixture of 5 and
6 obtained after chromatographic removal of nonpolar
byproducts.
Curiously, the arylation of Ph2Te proceeded at an abnormally
slow rate compared to that of other diphenyl chalcogenides.
Only a 36% conversion (1H NMR) was achieved after 48 h at
120 °C (bath temperature, sealed tube) in DCE, leading to the
isolation of Ph3TeOTf (ca. 30% yield) contaminated with a
byproduct of uncertain structure but seemingly arising through
the reaction of Ph2Te with the solvent.14 While this byproduct
was difficult to separate from Ph3TeOTf, its formation could be
The reaction of bis(4-bromophenyl)iodonium triflate with
thioanisole, 7, initially yielded sulfonium salt 8, which rapidly
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of the same chalcogen centers with other diaryliodonium
species occurs only upon vigorous thermal activation. Such
harsh conditions may promote significant decomposition of the
λ3-iodanes and/or of sensitive sulfonium salts. A mild, metal-
free route to triarylchalcogenonium triflates has thus been
established.20 New opportunities engendered by this develop-
ment are being examined and pertinent results will be disclosed
in due time.
Table 3. Catalyst-Free Arylation of Ph2Se and Ph2Te
b
entry
X
solvent
yield
a
b
c
Se
Se
Te
Te
CHCl3
DCE
94
91
c
DCE
30
d
d
CHCl3
14
ASSOCIATED CONTENT
* Supporting Information
■
a
Conditions: 0.1 M solution of Ph2IOTf (1.0 equiv) in (CH2Cl)2, 1.5
S
equiv of diarylchalcogen, thick-walled glass tube sealed with a Teflon
screwcap and immersed in an oil bath maintained at 120 °C, 24 h for
Experimental procedures and spectra. This material is available
free of charge via the Internet at http://pubs.acs.org.
b
selenides, 48 h for tellurides. Percent yield after silica gel column
chromatography (gradient 10% → 40% acetone−CH2Cl2) to remove
c
d
AUTHOR INFORMATION
Corresponding Author
nonpolar byproducts.. Yield at 36% conversion (see text). Yield at
15% conversion.
■
*E-mail: ciufi@chem.ubc.ca.
Notes
suppressed by carrying out the reaction in CHCl3, whereupon
highly pure Ph3TeOTf was obtained. Under such conditions,
however, the reaction proceeded to a modest 16% conversion
(1H NMR) after 48 h and the product was obtained in 14%
yield after chromatography.
The literature seems to contain no record of this telluronium
species, although two derivatives, (C6F5)3TeOTf15 and (4-
Ph2NC6H4)3TeOTf,16 have been described. Its structure was
therefore ascertained by single-crystal X-ray diffractometry
(Figure 1). A structural feature which is worthy of note is that,
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
We thank the University of British Columbia, the Canada
Research Chair Program, NSERC, CFI, and BCKDF for
financial support. T.K. is a recipient of a UBC FYF Fellowship;
L.R. is a recipient of a Vanier Fellowship. We also thank Dr.
Brian Patrick, of this department, for obtaining the X-ray
structure of Ph3TeOTf.
REFERENCES
■
(1) Reviews on the chemistry of Ar2IX: (a) Zhdankin, V. V.
Hypervalent Iodine Chemistry: Preparation, Structure and Applications of
Polyvalent Iodine Compounds; John Wiley & Sons: Chichester, UK,
2014; Chapters 2 and 3. (b) Yusubov, M. S.; Maskaev, A. V.;
Zhdankin, V. V. ARKIVOC 2011, 370. (c) Silva, L. F., Jr; Olofsson, B.
Nat. Prod. Rep. 2011, 28, 1722. (d) Merritt, E. A.; Olofsson, B. Angew.
Chem., Int. Ed. 2009, 48, 9052.
(2) (a) Crivello, J. V.; Lam, J. H. W. J. Org. Chem. 1978, 43, 3055.
Recent example: (b) Wagner, A. M.; Sanford, M. S. J. Org. Chem. 2014,
79, 2263.
(3) Applications in polymer chemistry: (a) Crivello, J. V. J.
Photopolym. Sci. Technol. 2008, 21, 493. (b) Crivello, J. V. J.
Photopolym. Sci. Technol. 2007, 20, 599. (c) Tanabe, H.; Kawai, T.;
Saitoh, T.; Ichikawa, J. Chem. Lett. 2010, 39, 56. Applications in 18F
radiochemistry: (d) Mu, L.; Fischer, C. R.; Holland, J. P.; Becaud, J.;
Schubiger, P. A.; Schibli, R.; Ametamey, S. M.; Graham, K.; Stellfeld,
T.; Dinkelborg, L. M.; Lehmann, L. Eur. J. Org. Chem. 2012, 889.
Applications in organometallic chemistry: (e) Khalimon, A. Y.; Piers,
W. E.; Blackwell, J. M.; Michalak, D. J.; Parvez, M. J. Am. Chem. Soc.
2012, 134, 9601.
(4) Kasahara, T.; Jang, Y. J.; Racicot, L.; Panagopoulos, D.; Liang, S.
H.; Ciufolini, M. A. Angew. Chem., Int. Ed. 2014, 53, 9673.
(5) For a similar mechanistic proposal, see: Nagaoka, T.; Sueda, T.;
Ochiai, M. Tetrahedron Lett. 1995, 36, 261.
(6) (a) Nesmeyanov, A. N.; Makarova, L. G.; Tolstaya, T. P.
Tetrahedron 1957, 1, 145. (b) Knapczyk, J. W.; McEwen, W. E. J. Am.
Chem. Soc. 1969, 91, 145.
(7) Umierski, N.; Manolikakes, G. Org. Lett. 2013, 15, 188.
(8) (a) Jalalian, N.; Petersen, T. B.; Olofsson, B. Chem.Eur. J. 2012,
18, 14140. (b) Jalalian, N.; Ishikawa, E. E.; Silva, L. F., Jr.; Olofsson, B.
Org. Lett. 2011, 13, 1552. See also: (c) Petersen, T. B.; Khan, R.;
Olofsson, B. Org. Lett. 2011, 13, 3462.
(9) Ochiai, M.; Nagaoka, T.; Sueda, T.; Yan, J.; Chen, D.-W.;
Miyamoto, K. Org. Biomol. Chem. 2003, 1, 1517.
Figure 1. X-ray crystal structure of triphenyltelluronium triflate.
at least in the solid state, the C1−Te−C13 bond angle is
significantly wider (102.6°) than the others (C1−Te−
C7:95.6°; C7−Te−C13:94.0°), while all C−Te bond lengths
are very similar (Te−C1:2.115 Å; Te−C7:2.133 Å; Te−
C13:2.112 Å). The O−Te distances range from 2.894 to2.947
Å,17 indicating that the interaction between the triflate oxygens
and the Te atom is weak and essentially ionic in nature.18
We also note that triaryltelluronium species, which are more
commonly made by reaction of TeCl4 with appropriate
arylmetallic agents, may become of considerable interest in
coordination and transition metal chemistry, given their
recently discovered ability to function as σ-acceptor ligands.19
In summary, diaryliodonium triflates efficiently arylate diaryl
sulfides and selenides under mild conditions, and without any
need for metallic catalysts. In contrast, the uncatalyzed arylation
(10) (a) Carroll, M. A.; Wood, R. A. Tetrahedron 2007, 63, 11349.
On the other hand, the reaction with aliphatic amines is problematic:
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(b) Ptitsyna, O. A.; Pudeeva, M. E.; Reutov, O. A. Dokl. Akad. Nauk.
SSSR 1964, 157, 364.
(11) (a) Ptitsyna, O. A.; Pudeeva, M. E.; Reutov, O. A. Dokl. Akad.
Nauk. SSSR 1966, 168, 595. (b) Ptitsyna, O. A.; Pudeeva, M. E.;
Reutov, O. A. Dokl. Akad. Nauk. SSSR 1965, 165, 582. (c) Ptitsyna, O.
A.; Pudeeva, M. E.; Bel’kevich, N. A.; Reutov, O. A. Dokl. Akad. Nauk.
SSSR 1965, 143, 383. (d) Kampmeyer, J. A.; Nalli, T. W. J. Org. Chem.
1993, 58, 943.
(12) E.g.: (a) Galezowski, W.; Ibrahim, P. N.; Lewis, E. S. J. Am.
Chem. Soc. 1993, 115, 8660. (b) McCortney, B. A.; Jacobson, B. M.;
Vreeke, M.; Lewis, E. S. J. Am. Chem. Soc. 1990, 112, 3554 and
references cited therein.
(13) (a) Kataoka, T.; Watanabe, S.-I.; Yamamoto, K. Tetrahedron
Lett. 1999, 40, 2153. (b) Watanabe, S.-I.; Yamamoto, K.; Itagaki, Y.;
Iwamura, T.; Iwama, T.; Kataoka, T. Tetrahedron 2000, 56, 855.
(14) In addition to Ph3TeOTf, the mass spectra of the product thus
obtained revealed the presence of a cationic species of probable
formula [Ph2TeCH2CH2Cl]+ (unknown of whether as a triflate or
chloride salt), which produced the correct isotopic pattern for the
presence of Te and Cl. The 1H NMR spectrum (Supporting
Information) displayed an AA′BB′ pattern centered at 4.2 ppm and
a distinctive signal at 7.95 ppm. The 13C NMR spectrum (Supporting
Information) exhibited peaks not belonging to Ph3TeOTf at 130, 127,
124, 120, 41, and 36 ppm.
(15) Naumann, D.; Tyrra, W.; Hermann, R.; Pantenburg, I.;
Wickleder, M. S. Zeit. Anorg. Allgem. Chem. 2002, 628, 833.
(16) Minoura, M.; Ishii, H.; Yamamoto, M.; Masaki, Y. Jpn. Kokai
Koho JP2011057637 A 20110324, 2011.
(17) See the Supporting Information for details.
(18) Typical O−Te bond lengths are 1.9−2.0 Å for covalent
interactions: (a) Subndberg, M. R.; Uggla, R.; Laitalainen, T.;
Bergman, J. J. Chem. Soc., Dalton Trans. 1994, 3279. (b) Fleischer,
H.; Schollmeyer, D. Inorg. Chem. 2001, 40, 324. 2.1−2.2 Å for dative
bonding: Hector, A. L.; Jolleys, A.; Levanson, W.; Reid, G. Dalton
Trans. 2012, 41, 10988. 2.18−2.27 Å for Te−O−Te bridging
interactions (ref 18b). Longer O−Te bond lengths (2.762−2.786 Å)
are found in bis((m2-2,4,6-trichlorophenoxo)-(2,2′-biphenylene)(2-
biphenylyl)tellurium) benzene solvate: Sato, S.; Kondo, N.; Furukawa,
N. Organometallics 1995, 14, 5393. They are also found in
(tetraphenylimidodiphosphinato)triphenyltellurium(IV) (2.65−2.93
Å): (d) Drake, J. E.; Silvestru, A.; Yang, J.; Haiduc, I. Inorg. Chim.
Acta 1998, 271, 75. We thank Dr. Brian Patrick, of this department,
for helpful discussions.
(19) Lin, T.-P.; Gabbaï, F. P. Angew. Chem., Int. Ed. 2013, 52, 3864.
(20) For alternative methods for the preparation of triarylsulfonium
salts, see: Miller, R. D.; Renaldo, A. F.; Ito, H. J. Org. Chem. 1988, 53,
5571 and references cited thererein.
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