Studies on sulfinatodehalogenation: The addition of polyfluoroalkyl iodides to olefins promoted by sodium bisulfite and sodium sulfite

Article abstract of DOI:10.1016/j.jfluchem.2006.10.001

The reaction of polyfluoroalkyl iodides with alkenes or 4-pentenoic acid promoted by sodium bisulfite or sodium sulfite in DMF aqueous solution was realized. The reaction of alkenes gave corresponding adducts, while γ-lactones were obtained in the case of

Full text of DOI:10.1016/j.jfluchem.2006.10.001

Journal of Fluorine Chemistry 128 (2007) 84–86
www.elsevier.com/locate/fluor
Short communication
Studies on sulfinatodehalogenation: The addition of polyfluoroalkyl
iodides to olefins promoted by sodium bisulfite and sodium sulfite
a
a
b
Fanhong Wu a,b, , Xueyan Yang , Zhonghua Wang , Weiyuan Huang
*
a School of Chemistry and Molecular Engineering, East China University of Science and Technology, Shanghai 200237, China
b Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, Shanghai 200032, China
Received 25 July 2006; received in revised form 27 September 2006; accepted 4 October 2006
Available online 10 October 2006
Abstract
The reaction of polyfluoroalkyl iodides with alkenes or 4-pentenoic acid promoted by sodium bisulfite or sodium sulfite in DMF aqueous
solution was realized. The reaction of alkenes gave corresponding adducts, while g-lactones were obtained in the case of 4-pentenoic acid in good
yields.
# 2006 Elsevier B.V. All rights reserved.
Keywords: Polyfluoroalkylation; Sodium bisulfite; Sodium sulfite; Addition reaction; Lactonization
1. Introduction
2. Results and discussion
Recently, the application of fluorinated compounds in
agricultural chemistry, medicinal chemistry, material science
and organic synthesis is growing. Therefore, the development of
new methodologies for selective introduction of fluorinated
functions into organic molecules is of great importance [1]. The
addition reaction of polyfluoroalkyl halides to olefins or
alkynes is traditionally accomplished with photochemical [2],
thermal [3], electrolytic [4], redox systems [5], especially,
sulfur oxy-acid salts, such as sodium dithionite [6], rongalite
[7], thiourea dioxide [8], sodium disulfite [9], and so on, which
is one of the most efficient and versatile methods for the direct
introduction of the fluoroalkyl groups into organic molecules
[10].
2.1. The reaction of polyfluoroalkyl iodides with olefins
Polyfluoroalkyl iodides reacted with olefins in DMF aqueous
solution in the presence of sodium bisulfite or sodium sulfite,
giving the corresponding adducts under mild conditions. The
reaction proceeded readily at 40–60 8C for about 6–7 h. 1.5 eq. of
olefin was used as the optimal amount. It gave the expected
addition products in good yields, providing a new application of
sodium bisulfite or sodium sulfite in polyfluoroalkylation reaction
(Scheme 1). The detailed results were summarized in Table 1.
The addition of polyfluoroalkyl iodides to allyl ether (2h)
gave the radical cyclization products with tetrahydrofuran
structure (Scheme 2), which indicated the involvement of free
radical intermediate.
Sodium bisulfite as well as sodium sulfite was recently
reported to be a sulfinatodehalogenation reagent for poly-
fluoroalkyl iodides and bromides, and the reaction mechanism
was considered to be a radical one [10b,11]. The polyfluor-
oalkyl radical intermediates formed in the reaction could be
trapped by olefins. Here we described the results of the addition
of polyfluoroalkyl iodides to double bonds promoted by sodium
bisulfite and sodium sulfite.
The 1:1 adducts (E/Z) were separated in good yields after
the addition of polyfluoroalkyl iodides to cyclohexene (2i)
(Scheme 3).
However, the addition products of polyfluoroalkyl iodides
with alkynes, for example, 1-hexyne (2j), under similar
conditions were obtained in low yields, because alkynes, as
expected, were less reactive than alkenes (Scheme 4). In case of
acrylonitrile or phenylacetylene, no adducts were formed
except the sulfinates.
In the addition reaction of polyfluoroalkyl iodides with
olefins, both sodium bisulfite and sodium sulfite lead to high
* Corresponding author. Tel.: +86 21 64253530; fax: +86 21 64253074.
E-mail address: wfh@ecust.edu.cn (F. Wu).
0022-1139/$ – see front matter # 2006 Elsevier B.V. All rights reserved.
doi:10.1016/j.jfluchem.2006.10.001

F. Wu et al. / Journal of Fluorine Chemistry 128 (2007) 84–86
85
Scheme 5.
Scheme 1.
Table 2
The lactonization reaction of polyfluoroalkyl iodides with 4-pentenoic acids
initiated by sodium bisulfite or sodium sulfite
Table 1
The addition reaction of polyfluoroalkyl iodides with alkenes initiated by
sodium bisulfite or sodium sulfite
Entry
RfIs
Acids
Initiators
NaHSO3
Lactones
Yields (%)
1
2
3
1a
1b
1d
4
4
4
5a
5b
5d
40
30
43
Entry
RfIs
Olefins
Initiators
NaHSO3
Adducts
Yields (%)
1
2
3
4
5
6
1b
1b
1c
1b
1c
1b
2e
2h
2g
2f
2i
3a
3b
3c
3d
3e
3f
89
78
85
87
81
38
4
1b
4
Na2SO3
5b
40
corresponding g-lactones. Hence, the reaction of 4-pentenoic
acid (4) with polyfluoroalkyl iodides promoted by sodium
bisulfite or sodium sulfite in DMF aqueous solution was
investigated. As a result, the corresponding lactones (5) were
obtained in moderate yields (Scheme 5). The detailed results
were summarized in Table 2.
2j
7
8
1b
1c
1a
1b
1d
1c
1c
2h
2f
2e
2e
2f
2i
Na2SO3
3b
3g
3h
3a
3i
72
75
70
85
80
70
40
9
10
11
12
13
3e
3j
2j
2.3. Mechanism consideration
The formation of the anion radical was relative to the
equilibrium in the bisulfite or sulfite solution shown in Scheme
6 [10]. In aqueous DMF solution, the equilibrium favors the
formation of S2O52À (*). It was supposed that the anion radicals
SO3ꢀÀ and/or SO2ꢀÀ could be formed through the homolysis of
S–S bond similarly to sodium dithionite [6]. Thus, the reaction
was thought to be a single electron transfer (SET) process
Scheme 2.
ꢀÀ
initiated by the anion radicals of SO3 and/or SO2ꢀÀ, as
proposed in Schemes 6 and 7. In the reaction, the
polyfluoroalkyl radical was trapped by olefins, and correspond-
ing adducts or lactones were prepared.
So, it was not difficult to explain why the yields of sodium
bisulfite reaction system were a little higher than that of sodium
Scheme 3.
yields, while the results showed that the yields of the former
were a little higher than that of the latter (Table 1, entries 1/10,
2/7, 5/12). The reason was thought to be related to the
mechanism and would be mentioned infra.
2.2. The reaction of polyfluoroalkyl iodides with
4-pentenoic acid (4)
Scheme 6.
In recent publication of our laboratory [12], it had been
reported that polyfluoroalkyl iodides reacted with 4-pentenoic
acid (4) in the presence of sodium dithionite, giving the
Scheme 4.
Scheme 7.

86
F. Wu et al. / Journal of Fluorine Chemistry 128 (2007) 84–86
evaporation of ether, the crude product was purified over silica
gel to give 3. For the reaction of 1 with 4, 7.5 mol of NaOH was
added to the mixture before the addition of sodium bisulfite or
sodium sulfite.
Acknowledgements
The authors indebt the National Natural Science Foundation
of China and the Shanghai Science and Technology Committee
for the financial support (Grant Nos. 29902001 and
03QB14012).
Scheme 8.
sulfite reaction system (Table 1, entries 1/10, 2/7, 5/12). The
reason was thought to be that the basicity and reductivity of
former system were a little stronger than that of the latter.
The lactones were formed after an intramolecular SN2
reaction of the adducts [12] (Scheme 8).
References
[1] K. Tsuchii, Y. Ueta, N. Kamada, Y. Einaga, A. Nonoto, A. Ogawa,
Tetrahedron Lett. 46 (2005) 7275–7278.
2.4. Conclusions
[2] G.V.D. Tiers, J. Org. Chem. 27 (1962) 2261–2262.
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hedron 20 (1964) 497–506.
In conclusion, a mild and convenient method for poly-
fluoroalkylation promoted by sodium bisulfite and sodium
sulfite was presented. Sodium bisulfite and sodium sulfite can
also be used to initiate the reaction of polyfluoroalkyl iodides
with 4-pentenoic acids. Efforts are in progress to elucidate the
mechanistic details of this reaction and to disclose its scope and
limitations.
[4] P. Calas, P. Moreau, A. Commeyras, J. Chem. Soc. Chem. Commun.
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3. Experimental
The general procedure: to the mixture of 2 (5 mmol), water
(5 mL), DMF (10 mL) and 1 (5 mmol), sodium bisulfite or
sodium sulfite (8 mmol) was added. The mixture was stirred at
40–60 8C for 6–7 h, then extracted with ether for several times.
The combined organic layer was washed with saturated brine
solution and dried over anhydrous sodium sulfate. After