Preparation of resin-bound alkynyl iodonium salts and their application in organic synthesis as alkynyl transfer reagents

Article abstract of DOI:10.1016/S0040-4039(01)01274-6

We have synthesized polymer-supported alkynylphenyl iodonium salts. They served as effective alkynyl transfer reagents for the preparation of acetylenic sulfones; the by-product, polymer supported (4-iodostyrene), could be reactivated for reuse numerous t

Full text of DOI:10.1016/S0040-4039(01)01274-6

TETRAHEDRON
LETTERS
Pergamon
Tetrahedron Letters 42 (2001) 6373–6375
Preparation of resin-bound alkynyl iodonium salts and their
application in organic synthesis as alkynyl transfer reagents
Xian Huanga,b,* and Qing Zhua
aChemistry Department, Xixi Campus, Zhejiang University, Hangzhou 310028, PR China
bNational Key Laboratory of Organometallic Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences,
Shanghai 20032, PR China
Received 11 May 2001; accepted 12 July 2001
Abstract—We have synthesized polymer-supported alkynylphenyl iodonium salts. They served as effective alkynyl transfer
reagents for the preparation of acetylenic sulfones; the by-product, polymer supported (4-iodostyrene), could be reactivated for
reuse numerous times. © 2001 Elsevier Science Ltd. All rights reserved.
Supported reagents on organic polymers have rapidly
become an area of intense research activity.1 One of the
key advantages is the ease of separation from the
product mixture at the end of a reaction, and polymer
recycling. Hypervalent iodine compounds have
attracted wide attention due to their unique chemical
properties.2 During continuing efforts to develop new
polymer supported hypervalent iodine compounds,3–5
we became interested in the synthesis of resin-bound
alkynyl iodonium salts.
to synthesize acetylenic sulfones and phenylbenzotria-
zoles.
The polymer support chosen for immobilization of the
alkynyliodonium salts was commercially available
polystyrene (MW=250,000, Acros). The resin was first
converted into poly[(4-diacetoxyiodo) styrene] by
known methods.9 Poly[(4-diacetoxyiodo) styrene] was
dissolved in CH2Cl2 and p-toluenesulfonic acid added.
After
a few minutes, poly{[4-hydroxy (tosyloxy)-
iodo]styrene} precipitated as a yellow solid. Elemental
analysis showed that the resin contained 1.91 mmol per
gram. This resin and alkynes were refluxed in dry
CHCl3 for a few hours. The resulting solution was
evaporated in vacuo and diethyl ether was added to
precipitate the white polymeric alkynyl iodonium salts10
(Scheme 1). The conversion was established by IR
spectroscopy, by the shifting of the characteristic peaks
of SO2 from 1186 to 1178 cm−1, and the appearance of
a peak at 2156 cm−1 (CꢀC, 1a) or 1364 cm−1 (t-Bu, 1b)
Alkynylphenyl iodonium salts6 are very important
reagents in organic synthesis which can be used to
synthesize heterocycles.7 Above all, they have been
recognized to be useful as synthons of alkynyl cations.8
However, to the best of our knowledge, no examples of
polymer-supported alkynylphenyl iodonium salts have
been reported. In this paper, we report the preparation
of polymer-supported alkynylphenyl iodonium salts,
and their application as alkynyl transfer reagents
Scheme 1.
Keywords: polymeric alkynylphenyl iodonium salts; solid-phase organic synthesis; acetylenic sulfones; phenylethynyl benzotriazole.
* Corresponding author.
0040-4039/01/$ - see front matter © 2001 Elsevier Science Ltd. All rights reserved.
PII: S0040-4039(01)01274-6

6374
X. Huang, Q. Zhu / Tetrahedron Letters 42 (2001) 6373–6375
and 2170 cm−1 (CꢀC, 1b). The functional group loading
was estimated as 1.21 (1a) or 1.41 (1b) mmol/g of resin
by elemental analysis of the sulfur component. The
polymer bound alkynyliodonium salts are stable in air,
and no decomposition was noted over a period of two
weeks at room temperature, but the resin products were
best stored away from direct sunlight and in a refrigerator.
products. The reactions were efficient and high yielding.
(Table 1)
Functionalized benzotriazoles are considered to be
important substances in organic synthesis.14 We prepared
phenylethynyl benzotriazole by using the polystyrene
supported phenyliodonium salts. After the potassium salt
of benzotriazole was dissolved in t-BuOH and CH2Cl2,
1a was added. After stirring the reaction mixture for 24
h, the product mixture was extracted and submitted to
column chromatography on silica gel to give
phenylethynyl benzotriazole.15 (Scheme 3)
Acetylenic sulfones are important well-known synthetic
intermediates.11 Chen et al. reported12 that alkynyl
phenyliodonium salts could be used to synthesize
acetylenic sulfones. On recognition that polymeric
reagents have the same reactivity as their small molecule
counterparts, the polymeric alkynylphenyl iodonium salts
were employed as alkynyl transfer reagents to prepare
acetylenic sulfones13 (Scheme 2).
After the reactions, poly(4-iodostyrene), to which the
polymeric alkynylphenyl iodonium salts had been con-
verted, was dissolved in CH2Cl2 and precipitated by the
addition of ether to purify the resin. The recovered resin
was converted to polymer supported alkynyliodonium
salts according to the above methods. The alkynylation
of sodium sulfonates (2a) with polymer-supported
alkynylphenyliodoniumsalts(1a)wasrepeatedfourtimes
using the same batch of 1a. As seen in Table 2, the yields
remained constant.
To a solution of the sodium sulfinates (2) in water was
added the polymer-supported alkynylphenyl iodonium
salts (1) in CHCl3. The reactions were carried out in the
presence of a catalytic amount of tetraethylammonium
bromide (TEBA) at room temperature. After the reaction
was complete, the organic layer was separated and dried
over anhydrous MgSO4. The solvent was removed under
vacuum and CH3CN was added to the resulting oil to
precipitate poly(4-iodostyrene). The solution was submit-
ted to column chromatography on silica gel to give pure
In conclusion, our research group has first prepared the
polymer-supported alkynylphenyl iodonium salts. They
can serve as effective alkynyl transfer reagents for the
preparation of acetylenic sulfones by a solid-phase
organic synthesis. The regeneration of polymeric hyper-
valent iodine salts that show the same activity as newly
prepared reagents has been discussed. Further applica-
tions of polymeric alkynylphenyl iodonium salts are
under study.
Table 1. S-Alkynylation of sodium sulfinates (2) with
polymer-supported alkynylphenyl iodonium salts (1)
Entry
R
Ar
Time (min)
Yield (%)a
1
2
3
4
5
6
7
8
Ph
t-Bu
Ph
t-Bu
Ph
t-Bu
Ph
Ph
Ph
15
20
15
20
15
20
15
20
61
70
59
65
62
65
64
72
Table 2. Reusability of resin-bound alkynylphenyl iodo-
nium salts
p-CH3C6H4
p-CH3 C6H4
p-Cl C6H4
p-Cl C6H4
m-NO2 C6H4
m-NO2 C6H4
Experiment
Yields using 1a (%)
1
2
3
4
61
59
60
58
t-Bu
a Isolated yields.
Scheme 2.
Scheme 3.

X. Huang, Q. Zhu / Tetrahedron Letters 42 (2001) 6373–6375
6375
Acknowledgements
w (cm−1): 2921, 2156, 1483, 1178, 1031, 1006, 816, 680.
Compound 1b: white powder; 1.1 g; S%: 4.51%; IR (KBr)
w (cm−1): 2922, 2170, 1482, 1364, 1177, 1032, 1005, 815,
681.
Project 29932020 was supported by the National Natu-
ral Foundation of China.
11. (a) Won, B. J.; Dong, Y. O.; Lee, C. M. Tetrahedron
Lett. 2000, 41, 5103; (b) Eisch, J. J.; Aradi, A. A.;
Lucarelli, M. A.; Qian, Y. Tetrahedron 1998, 54, 1169; (c)
Spencer, J.; Pfeffer, M.; DeCian, A.; Fischer, J. J. Org.
Chem. 1995, 60, 1005; (d) Halasta, D. J.; Ackerman, J. H.
J. Org. Chem. 1994, 59, 6184; (e) Huang, D. F.; Shen, T.
Y. Tetrahedron Lett. 1993, 34, 4477.
12. Liu, Z. D.; Chen, Z. C. Synth. Commun. 1992, 22, 1997.
13. Preparation of acetylenic sulfones 3: A solution of poly-
mer-supported alkynylphenyl iodonium salt (1) 1 mmol
in 10 mL CHCl3 was added to a solution of sodium
sulfinate (2) 1 and 0.05 mmol TEBA in 10 mL H2O, and
the mixture stirred at room temperature. After the reac-
tion was complete, the organic layer was separated and
the water layer was extracted with CHCl3 (10 mL×2). The
combined organic layer was washed with water (10 mL×
2) and dried over MgSO4. After removal of the solvent, 5
mL CH3CN was added to separate poly (4-iodostyrene)
and the product. Further purification could be achieved
by column chromatography using 2:1 hexane/
dichloromethane as eluent (Rf=0.2).
14. Katritzky, A. R.; Lan, X. Chem. Soc. Rev. 1994, 363.
15. Preparation of phenylethynyl benzotriazole 4: 1 mmol of
the potassium salt of benzotriazole was dissolved in 10
mL mixed solvent of t-BuOH and CH2Cl2 (1:1), and 1.2
mmol polymer-supported alkynylphenyl iodonium salt 1a
was added to the solution. After stirring for 24 h at room
temperature, the product mixture was poured into 10 mL
water. The organic layer was separated and the aqueous
layer extracted with CHCl3 (10 mL×2). The combined
organic layer was washed with water (10 mL×2), and
dried over MgSO4. After removal of the solvent, 5 mL
CH3COOC2H5 was added to separate poly (4-
iodostyrene) and the product. Further purification could
be achieved by chromatography using 1:1 hexane/
dichloromethane as eluent (Rf=0.26).
References
1. (a) Suto, M. J.; GayoFung, L. M.; Palanki, M. S. S.;
Sullivan, R. Tetrahedron 1998, 54, 4141; (b) Gayo, L. M.;
Suto, M. J. Tetrahedron Lett. 1997, 38, 513; (c) Parlow, J.
J. Tetrahedron Lett. 1996, 37, 5257; (d) Nicholas, E. J.;
Scott, K. A. J. Org. Chem. 2000, 65, 4770.
2. Stang, P. J. Chem. Rev. 1996, 96, 1123.
3. Tago, H.; Abe, S.; Nogami, G.; Yakoyama, M. Bull.
Chem. Soc. Jpn. 1998, 72, 2351.
4. Sket, B.; Zupan, M.; Zupet, P. Tetrahedron 1984, 30,
1603.
5. Huang, X.; Zhu, Q. Synth. Commun. 2001, 31, 111.
6. (a) Tykwinski, R. R.; Stang, P. J.; Persky, N. E. Tetra-
hedron Lett. 1994, 35, 23; (b) Feldman, K. S.; Bruendl,
M. M.; Schildknegt, K. J. Org. Chem. 1995, 60, 7722.
7. (a) Williamson, B. L.; Tykwinski, R. R.; Stang, P. J. J.
Am. Chem. Soc. 1994, 116, 93; (b) Schildknegt, K.;
Bohnstedt, A. C.; Feldman, K. S. J. Am. Chem. Soc.
1995, 117, 7544; (c) Feldman, K. S.; Bruendl, M. M.;
Schildknegt, K. J. Org. Chem. 1996, 61, 5440.
8. (a) Stang, P. J.; Crittel, C. M.; Boudakian, M. M. J. Org.
Chem. 1992, 57, 4305; (b) Tykwinski, R. R.; Stang, P. J.
Tetrahedron 1993, 49, 3043; (c) Liu, Z. D.; Chen, Z. C. J.
Org. Chem. 1993, 58, 1924; (d) Fischer, D. R.;
Williamson, B. L.; Stang, P. J. Synlett 1992, 535.
9. Wang, G. P.; Chen, Z. C. Synth. Commun. 1999, 29,
2859.
10. Preparation of polymer-supported alkynylphenyl iodo-
nium salts 1: To a solution of poly{[4-hydroxy(tosyl-
oxy)iodo]styrene} (2 mmol, 1.05 g) in 10 mL CHCl3,
phenylacetylene (12 mmol, 2.09 g) or t-butylacetylene (8
mmol, 0.66 g) was added. The mixture was refluxed for 1
or 6 h, respectively. After the reaction was complete, the
CHCl3 was evaporated in vacuum to give an oily residue.
Diethyl ether (10 mL) was added to precipitate the prod-
ucts, which were filtered off and washed with ether (10
mL×2) and acetone (10 mL×2) to afford the products.
Compound 1a: white powder; 1.2 g; S%: 3.87%; IR (KBr)
Compound 4: white solid; mp 77–78°C (lit16 77–78°C);
1H NMR (CDCl3): l 7.44–7.52 (m, 4H); 7.64–7.69 (m,
3H); 7.77 (d, J=8 Hz, 1H); IR (film) w (cm−1): 2259,
1611, 1483, 1306, 1286, 1005, 780, 761, 754, 689.
16. Kitamura, T.; Tashi, N.; Tsuda, K.; Fujiwara, Y. Tetra-
hedron Lett. 1998, 39, 3787.
.