An efficient ligand exchange reaction of (e)-[β- (trifluoromethanesulfonyloxy)ethenyl](phenyl)iodonium triflates with aryl- and alkynyllithium reagents leading to diaryl- and alkynyliodonium triflates

Article abstract of DOI:10.1055/s-2000-6234

Reaction of (E)-[β-(trifluoromethanesulfonyloxy)- ethenyl](phenyl)iodonium triflates with aryl- and alkynyllithium reagents gave aryl(phenyl)- and alkynyl(phenyl)iodonium triflates in high yields and selectively. These reactions indicate that ligand exchange takes place efficiently at the hypervalent iodine atom and provides another approach to diaryl- and alkynyliodonium salts.

Full text of DOI:10.1055/s-2000-6234

SHORT PAPER
81
An Efficient Ligand Exchange Reaction of (E)-[b-(Trifluoromethane-
sulfonyloxy)ethenyl](phenyl)iodonium Triflates with Aryl- and
Alkynyllithium Reagents Leading to Diaryl- and Alkynyliodonium Triflates
Namig Sh. Pirguliyev,a Valery K. Brel,b* Navruz G. Akhmedov,a Nikolai S. Zefirova,b
aDepartment of Chemistry, Moscow State University, Moscow 119899, Russia
Fax +7(095)9390290
bInstitute of Physiologically Active Compounds of Russian Academy of Sciences, 142432 Moscow Region, Chernogolovka, Russia
FAX: +7(095)9132113; E-mail: brel@ipac.ac.ru
Received 19 August 1999
iodonio group; and (e) the high nucleofugacity of OTf is
very suitable to induce elimination at the stage of ligand
exchange.
Abstract: Reaction of (E)-[b-(trifluoromethanesulfonyloxy)-ethen-
yl](phenyl)iodonium triflates with aryl- and alkynyllithium re-
agents gave aryl(phenyl)- and alkynyl(phenyl)iodonium triflates in
high yields and selectively. These reactions indicate that ligand ex-
change takes place efficiently at the hypervalent iodine atom and
provides another approach to diaryl- and alkynyliodonium salts.
There are only a few successful examples of application
of the ligand exchange reaction7 using vinyliodonium
salts for synthesis of diaryliodonium salts.7,8 Due to the
reasons given above, we considered that (b-trifluo-
romethanesulfonyloxyvinyl)iodonium triflates would un-
dergo ligand exchange effectively. In this paper we report
a direct convenient preparation of diaryl- and alkynyl-
iodonium triflates using (E)-b-triflylvinyliodonium tri-
flates.
Key words: alkynes, aryl halides, hypervalent elements, iodine
Recently much attention has been paid to polyvalent io-
dine(III) compounds in organic synthesis.1 Symmetric
and asymmetric diaryliodonium salts, Ar2I+X- and [ArI-
Ar¢]+X-, and alkynyliodonium salts, RC∫CI+Ar X-,2,3
with a large diversity of inorganic and organic counter-
ions, X-, represent the most important classes of polyva-
lent iodine(III) compounds.2 Diaryliodonium salts are
widely used in organic synthesis as efficient arylating re-
agents for a great variety of nucleophiles, some of them
display biological (e.g. antimicrobial) activity and photo-
chemical properties, and they are also suggested to be ef-
ficient catalysts for radiation-initiated polymerization.1,2
The application of alkynyliodonium salts in organic syn-
thesis cannot be overemphasized.2,3 Thus, new or impor-
tant preparations are being sought in many laboratories.4
Especially, considering the useful properties of salts and
other derivatives of triflic acids,5 the development of a
simple and efficient procedure for the preparation of
diaryl- and alkynyliodonium triflates is a desirable goal.
-OTf
ArI+
H
o
,-78 C
ArI+F -OTf
HC CH
57-91%
H
OTf
1
-78oC
R'Li
Et2O or
PhMe
-LiOTf
R'
I
H
Ar
ArI+R' -OTf
2a-p
-C2H2
H
OTf
Our approach to the synthesis of diaryliodonium salts in-
volved the following steps: (a) preparation of a compound
X-Z-IArX such that Z represents a masking group inert to
R¢Li under the reaction conditions, X, the nucleofugal
group; (b) reaction of X-Z-IArX with 2 equivalents of
R¢Li forming X-Z-IArR¢ (R¢ = Ar¢ or RC∫C); and (c) re-
moval of Z to form [ArIAr¢]+X- or RC∫CI+ArX-. Several
considerations lead to the selection of the-CH=CH-
group as Z and the triflate group as X. There were several
reasons for believing in the possibility of the final ionic
elimination: (a) the analogous compounds, namely (b-
chlorovinyl(iodonium chloride with the base yields acety-
lenes;6 (b) the large size of the IArR¢ group might favor
elimination; (c) the third carbon-iodine bond should be
weak;2 (d) the (b-triflyloxy)vinyliodonium triflates have a
good leaving group, OTf, with the geometry trans to aryl-
The (E)-b-triflylvinyliodonium triflates were prepared by
-
the reaction of [ArI+F OTf] with acetylene in dichlo-
romethane at -78 °C in 57-91% yield.9 Ligand exchange
reaction of these compounds with R¢Li provided the cor-
responding diaryl- and alkynyliodonium triflates in good
yields.
In general, the best yields of iodonium salts were obtained
by the dropwise addition of a solution of the aryl- or alky-
nyllithium in hexane to a solution of the corresponding
alkenyliodonium salts under argon at dry-ice-acetone
temperature. This temperature was then maintained for 1-
3 hours before the reaction mixture was allowed to rise
slowly to room temperature. Stirring of the resulting sus-
pension was then continued for approximately 1-5 hours.
Synthesis 2000, No. 1, 81–83 ISSN 0039-7881 © Thieme Stuttgart · New York

82
N. Sh. Pirguliyev et al.
SHORT PAPER
The availability of low-temperature solvent systems, un- present method is an example of transfer from one class of
reactive toward aryl and alkynyllithium reagents is limit- hypervalent iodine compounds to another.
ed, however, we have compared the reaction in diethyl
ether, toluene, tetrahydrofuran and pentane. Low yields
All reactions were conducted under a dry Ar atmosphere. NMR-
(20-27%) of iodonium salts could be isolated from the re-
actions ran in tetrahydrofuran, but the yields from the re-
actions done in toluene or Et2O were frequently over 60%.
When dry pentane was used as solvent the yields were er-
ratic and usually below 30%. The lithium reagents with
activated aryl residues such as 4-MeOC6H4, 4-EtOC6H4
and 4-AlkC6H4 reacted completely within 1-2 hours.
Weakly deactivated aryllithium reagents such as
HalC6H4Li needed a prolonged reaction time to produce
reasonable yields of the diaryliodonium triflates. Howev-
er, the alkenyliodonium triflates with strongly deactivated
aromatics such as 4-NO2C6H4 did not give the corre-
sponding diaryliodonium triflates. As far as alkynyliodo-
nium salts are concerned, this method is clearly general
for the formation of any alkynyliodonium salt, being lim-
ited only by the possibility of preparation of the alkynyl-
lithium reagents.
spectra were recorded on a Varian VXR-400 spectrometer. 1H
NMR spectra were recorded at 400 MHz, and all chemical shifts (d)
are reported in ppm relative to the solvent peaks (CDCl3: 7.21 ppm
or CD3OD: 3.31 ppm). 13C NMR spectra were recorded at 100
MHz, and all chemical shifts (d) are reported in ppm relative to the
solvent peaks (CD3OD: 49.0 ppm or CDCl3: 77.0 ppm). Mps are un-
corrected. Et2O and THF were purified by literature procedures12
and were distilled over Na/benzophenone.
Diaryliodonium Triflates; General Procedure
A 100 mL flask was charged with toluene (25 mL) or Et2O (25 mL)
and the desired bromoarene or alkyne (8.8 mmol). The mixture was
cooled to -78 °C using a dry ice-acetone bath. A 2.5 M solution of
BuLi in hexanes (4,0 mL, 10,0 mmol) was added with a syringe and
the mixture was stirred at -78 °C for 15 min. Alkenyliodonium tri-
flate 1 (7.5 mmol) was then added all at once and the mixture was
stirred at -78 °C for additional 1-3 h, then the temperature was al-
lowed to warm gradually to r.t. during 1-1.5 h. After stirring at r.t.
for an additional 1-5 h, the reaction mixture was filtered using an
aspirator pump under an Ar stream. After evaporation of the sol-
vent, Et2O was added to crystallize the residue. The solid was fil-
tered, washed with Et2O, and dried in vacuo. Spectral data for newly
prepared diaryliodonium triflates are as follows.
In summary, we have found that ligand exchange reaction
of (E)-b-triflylvinyliodonium triflates with aryl- and alky-
nyllithium reagents is a mild and efficient method for the
preparation of diaryl- and alkynyliodonium salts. The
Table Yields of Iodonium Triflates Prepared
Productc
2a
Ar
R′
Isolated Yieldsa (%)
Mpb (oC) (Lit)
Ph
Ph
84
76
69
63
82
71
87
66
64
78
75
68
56
76
69
71
177−180 (178−180)4c
123−125 (122−125)4b
110−112 (109−111)4b
138−139 (136−138)4b
143−147 (144−148)4b
110−112 (110−111)4b
161−164
2b
2c
Ph
4-CH3C6H4
4-MeOC6H4
2,5-Me2C6H4
4-IC6H4
Ph
2d
2e
Ph
Ph
2f
Ph
4-ClC6H4
4-tert-BuC6H4
4-EtOC6H4
4-CH3C6H4
Ph
2g
Ph
2h
2i
Ph
74−76 (73−75)4b
185−186 (185−187)4c
124−126 (122−125)4b
136−140
4-CH3C6H4
2j
4-CH3C6H4
2k
2l
Ph
Ph
Ph
Ph
Ph
Ph
4-EtC6H4
4-Pri-C6H4
quinolin-3-yl
MeOCH2C≡C
PhC≡C
144−148
2m
2n
2o
176−184
73−74 (72−72)10
82−84 (83)11
2p
n-BuC≡C
67−69 (67−68)11
a Based on ethenyliodonium salts.
b Uncorrected, measured on a micro melting point apparatus.
c Satisfactory microanalyses obtained (C, 0.4%; H, 0.25%).
Synthesis 2000, No. 1, 81–83 ISSN 0039-7881 © Thieme Stuttgart · New York

SHORT PAPER
An Efficient Ligand Exchange Reaction of Aryliodonium Triflates
83
(4-tert-Butylphenyl)(phenyl)iodonium Triflate (2g)
1H NMR (400 MHz, CDCl3): d = 1.28 (s, 9H, Me), 7.35-7.63 (m,
4H, ArH), 7.87-8.10 (m, 5H, ArH).
13C NMR (100 MHz, CDCl3): d = 30.97, 35.30, 109.63, 113.76,
129.55, 132.12, 132.35, 135.14, 135.23, 156.65.
(4) (a) Kitamura, T.; Kotani, M.; Fujiwara, Y. Tetrahedron Lett.
1996, 37, 3721.
(b) Kitamura, T.; Matsuyuki, J.; Nagata, K.; Furuki, R.,
Taniguchi, H. Synthesis 1992, 945.
(c) Stang, P. J.; Zhdankin, V. V.; Tykwinski; R., Zefirov, N.
S. Tetrahedron Lett. 1991, 32, 7497.
(4-Ethylphenyl)(phenyl)iodonium Triflate (2k)
(5) For reviews see: (a) Huang, W.-Y.; Chen, Q.-Y. In The
Chemistry of Sulfonic Acids, Esters and their Derivatives;
Patai, S.; Rappoport, Z., Eds.;Wiley-Interscience: Chichester
1991; Chap. 21, p .903.
1H NMR (400 MHz, CDCl3): d = 1.12 (t, 3H, Me), 2,08 (q, 2H,
CH2), 7,25-7,62 (m, 4H, ArH), 7,92-8,03 (m, 5H, ArH).
13C NMR (100 MHz, CDCl3): d = 14.40, 35.40, 106.10, 118.20,
119.50, 131.61, 131.98, 135.11, 136.62, 141.84.
(b) Moriarty, R. M.; Vaide, R. K. Synthesis 1990, 431.
(c) Stang, P. J.; White, M. R. Aldrichimica Acta 1983, 16, 15.
(d) Howells, R. D.; Mc Cown, J. D. Chem. Rev. 1977, 77, 69.
(e) Stang, P. J.; Hanack, M.; Subramanian, L. R. Synthesis
1982, 85.
(4-Isopropylphenyl)(phenyl)iodonium Triflate (2l)
1H NMR (400 MHz, CDCl3): d = 1.4 (m, 6H, Me), 2.65 (m, 1H,
CH), 7.11-7.67 (m, 4H, ArH), 8.01-8.31 (m, 5H, ArH).
13C NMR (100 MHz, CDCl3): d = 17.85, 29.20, 114.67, 121.65,
129.80, 131.50, 132.04, 132.26, 134.60, 134.95, 142.23, 143.85.
(6) (a) Freidlina, R. Kh.; Brainina, E. M.; Nesmeyanov, A. N.
Bull. Acad. Sci. URSS. Classe Sci. Chim. 1945, 647; Chem.
Abstr. 1946, 40, 4686.
(b) Brainina, E. M.; Freidlina, R. Kh. Bull. Acad. Sci. URSS.
Classe Sci. Chim. 1947, 623; Chem. Abstr. 1948, 42, 5863a.
(7) Oae, S.; Uchida, Y. Acc. Chem. Res. 1991, 24, 202.
(8) (a) Beringer, F. M.; Nathan, R. A. J. Org. Chem. 1970, 35,
2095.
(Quinolin-3-yl)(phenyl)iodonium Triflate (2m)
1H NMR (400 MHz, CD3OD): d = 7.35-7.56 (m, 5H, ArH), 7.79 (t,
1H, J = 5.5 Hz, H-6), 7.96 (t, 1H, J = 6.9 Hz, H-7), 8.01-8.04 (m,
ArH), 8.10 (d, 1H, J = 8.0 Hz, H-5), 8.16 (d, 1H, J = 8.0 Hz, H-8),
9.43 (d, 1H, J = 2.0 Hz, H-4), 9.49 (d, 1H, J = 2.0 Hz, H-2).
13C NMR (100 MHz, CD3OD): d = 111.40, 115.20, 129.90, 130.1,
130.24, 130.70, 131.95, 132.19, 134.4, 143.87, 145.90, 152.80.
(b) Gronowitz, S.; Ander, I. Acta. Chem. Scand. 1975, B29,
513.
(c) Gronowitz, S., Holm, B. J. Heterocycl. Chem. 1977, 14,
281.
(d) Margida, A. J.; Koser, G. F. J. Org. Chem. 1984, 49, 4703.
(e) Kitamura, T.; Kotani, M.; Fujiwara, Y. Tetrahedron Lett.
1996, 37, 3721.
References
(1) (a) Koser, G. F. In The Chemistry of Functional Groups,
Supplement D; Patai, S.; Rappoport, Z., Eds.; Wiley: New
York, 1983; Chap. 18, p. 721 and Chap. 25 p. 1265.
(b) Varvoglis, A. Synthesis 1984, 709.
(9) Kasumov, T. M.; Pirguliyev, N. Sh.; Brel, V. K.; Grishin, Yu.
K.; Zefirov, N. S.; Stang, P. J. Tetrahedron 1997, 53, 13139.
(10) Williamson, B. L.; Stang, P. J.; Arif, A. M. J. Am. Chem. Soc.
1993, 115, 2590.
(c) Moriarty, R. M.; Prakash, O. Acc. Chem. Res. 1986, 19,
244.
(11) Bachi, M. D.; Bar-Ner, N.; Critell, Ch. M.; Stang, P. J.;
Williamson, B. L. J. Org. Chem. 1991, 56, 3912.
(12) Perrin, D. D.; Armarego, W. L. F.; Perrin, D. R. Purification
of Laboratiry chemicals; Pergamon: 1988.
(d) Ochiai, M.; Nagao, Y. Yuki Gosei Kagaku Kyokaishi 1986,
44, 660.
(e) Varvoglis, A. The Organic Chemistry of Polycoordinated
Iodine; VCH: New York, 1992.
(f) Stang, P. J. Angew. Chem. Int. Ed. Engl. 1992, 31, 274.
(2) (a) Sandin, R. B. Chem. Rev. 1943, 32, 249.
(b) Stang, P. J.; Zhdankin, V. V. Chem. Rev. 1996, 96, 1123.
(3) Zhdankin, V. V.; Stang, P. J. Tetrahedron 1998, 54, 10927.
Article Identifier:
1437-210X,E;2000,0,01,0081,0083,ftx,en;P05199SS.pdf
Synthesis 2000, No. 1, 81–83 ISSN 0039-7881 © Thieme Stuttgart · New York