Improved and facile addition reactions of pentafluorosulfanyl bromide

Article abstract of DOI:10.1016/j.tetlet.2008.07.080

A solution of SF₅Br in CCl₃F (0.5-1 M) was utilized to effect the addition of pentafluorosulfanyl bromide (SF₅Br) to olefins. The reaction of the SF₅Br solution in the presence of triethylborane (0.1 equiv) with an olefin over 20 min at 0 °C gave pentafluorosulfanylated compound 2(a-f) in high yield (Table 2). An efficient route for the preparation of synthetically useful SF5-containing esters is also described.

Full text of DOI:10.1016/j.tetlet.2008.07.080

Tetrahedron Letters 49 (2008) 5662–5663
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Tetrahedron Letters
journal homepage: www.elsevier.com/locate/tetlet
Improved and facile addition reactions of pentafluorosulfanyl bromide
a
a
b
b
a,*
Dong Sung Lim , Silvana C. Ngo , Sankar G. Lal , Kristen E. Minnich , John T. Welch
a
Department of Chemistry, University at Albany, SUNY, 1400 Washington Avenue, Albany, NY 12222, USA
Air Products and Chemicals, Inc., Allentown, PA 18195, USA
b
a r t i c l e i n f o
a b s t r a c t
Article history:
5 3
A solution of SF Br in CCl F (0.5–1 M) was utilized to effect the addition of pentafluorosulfanyl bromide
Received 22 February 2007
Revised 11 July 2008
Accepted 15 July 2008
Available online 17 July 2008
(
5 5
SF Br) to olefins. The reaction of the SF Br solution in the presence of triethylborane (0.1 equiv) with an
olefin over 20 min at 0 °C gave pentafluorosulfanylated compound 2(a–f) in high yield (Table 2). An
efficient route for the preparation of synthetically useful SF5-containing esters is also described.
Ó 2008 Elsevier Ltd. All rights reserved.
Several methods for introduction of pentafluorosulfanyl groups
into organic compounds are known. In 1985, Kovacina and
DeMarco disclosed a process for the production of mono-
employed were stable for at least four months under refrigeration
and with protection from light and moisture. The addition of KF to
the reaction mixture had little or no effect on the reaction
1
6b
pentafluorosulfanyl diacetylene polymers. In a report by Winter
(Table 1).
2
and Gard in 2000, the addition of SF
5
Br to an acrylic ester was
In a study of the influence of the solvent on the reaction, it was
found that the use of polar solvents resulted in BrF addition. The
effected in Freon-113 under autologous pressure at 65 °C. In
3
2
001, Winter and Gard reported the reaction of pentafluorosulfa-
products of SF
were employed, with CCl
As SF -containing esters have significant synthetic utility, a
search for the most effective route to the preparation of these com-
pounds was undertaken. SF Br addition reactions were effected
using a SF Br solution (0.5–1 M in CCl F) and triethylborane
5
Br addition dominated when nonpolar solvents
nyl chloride with a terminal olefin in the course of preparing SF
5
-
3
F the preferred solvent (Table 1).
terminated perfluoroalkyl thiols. In this work, where no solvent
was employed, the authors noted that pentafluorosulfanyl bromide
yielded only BrF addition products as established by GC analysis.
However, in 2004, Gard and co-workers4 reported that acrylate
5
5
5
3
systems did react with SF
tions at 65 °C. These workers also were able to effect the addition
of SF Br photochemically to allylic acetates in a closed reaction
5
Br under the same solvent free condi-
(0.1 equiv) in 20 min at 0 °C to form compound 2(a–f) in high
yield (Table 2).
The reaction yielded the SF Br addition products cleanly with
5
no evidence of BrF addition. It should be noted that the order of
addition of reagents and the temperature of the reaction were
8
5
5
vessel under autologous pressure. Subsequently, Dolbier and co-
workers6 reported that triethylborane dramatically improved the
addition reactions of SF
5
C1 to alkynes and alkenes in hexane at
5 5
critical factors in the success of SF Br addition. When the SF Br
temperatures ranging from À30 °C to room temperature. In the
7
patent literature, methods for both the catalyzed and uncatalyzed
Table 1
The influence of solvent on pentafluorosulfanyl bromide addition reactions to
cyclohexene
addition reactions of SF
5
Br in pentane have been described.
The reactions of SF Br have not been widely investigated, and
5
were frequently effected in closed systems such as FEP or metal
reaction vessels. To overcome the inconvenience of such systems
F
SF5
Br
SF Br
5
+
and to avoid vacuum-transfers of SF
dures were developed. As such, we report the use of a standard
solution of SF Br in normal glassware under an inert atmosphere,
5
Br more convenient proce-
Br
A
B
5
Entry
Conditionsa
Solvent
Ab
B
such as argon, at ambient pressure and at 0 °C.
Initially, our investigation into the use of a standard solution of
1
2
3
4
5
6
KF
—
CH
CH
CH
CH
2
2
2
2
Cl
Cl
Cl
Cl
2
2
2
2
9
9
9
9
7
4
1
1
1
1
3
6
SF
SF
5
Br in common glassware gave results similar to those of gaseous
Br addition to the reaction mixture, that is, in dichloromethane,
SF
SF
5
Br(soln in CH
Br(soln in CH
2
Cl
Cl
2
) and KF
5
5
2
2
)
5
BrF addition to the olefins is the major product. The SF Br solutions
KF
—
Pentane
CCl
3
F
a
*
Corresponding author. Tel.: +1 518 442 4455; fax: +1 518 442 3462.
E-mail address: JWelch@uamail.albany.edu (J. T. Welch).
All reactions, 0.1 equiv Et
Product ratio determined by F NMR.
3
B, 1.2 equiv SF
5
Br, temperature À78 °C to rt.
b
19
0
040-4039/$ - see front matter Ó 2008 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tetlet.2008.07.080

D. S. Lim et al. / Tetrahedron Letters 49 (2008) 5662–5663
5663
Table 2
O
O
O
3
Pentafluorosulfanyl bromide addition in CCl F
O
SF Br (1.3 eq / 0.5 - 1 M in CCl F)
DBU / C H6
6
5
3
9
6%
A
B
o
Et B (0.1 eq) / 0 C
SF5
Br
RT / 5 min
SF5
3
Br
Entry
1
A
B
Reaction timea
20
Yieldb
94
2c
3c
O
O
1a
O
DBU / C6H6
RT / 5 min
O
Br
2
a
O
t
-Bu
Ot-Bu
91%
O
SF5
O
SF5
F S
5
2f
3f
O
O
O
Scheme 1.
2
3
4
OMe
SF5
10
20
85
93
OMe 1b
2b
Br
O
Acknowledgment
OEt
Support of this research by Air Products and Chemicals, Inc. is
gratefully acknowledged.
OEt
2
c
1c
SF5
Br
O
Supplementary data
O
OEt
2d
2f
10
10
92
99
Supplementary data associated with this article can be found, in
the online version, at doi:10.1016/j.tetlet.2008.07.080.
OEt
1
d
SF5
Br
References and notes
Br
O
O
O
5
1f
1
.
Kovacina, T. A.; DeMarco, R. A.; Snow, A. W. US Patent 4,535,011, 1985.
2. Winter, R.; Gard, G. L.. J. Fluorine Chem. 2000, 102, 79–87.
Winter, R.; Gard, G. L. J. Fluorine Chem. 2001, 107, 23–30.
O
SF5
3
.
a
4. Winter, R. W.; Dodean, R.; Holmes, L.; Gard, G. L. J. Fluorine Chem. 2004, 125,
In minutes.
Isolated, purified yield.
b
37–41.
5
6
.
.
Winter, R. W.; Gard, G. L. J. Fluorine Chem. 2004, 125, 549–552.
(a) Samia, A.; Dolbier, W. R. Org. Lett. 2002, 4, 3013–3015; (b) Tatina, A. S.;
Dolbier, W. R. Org. Lett. 2004, 6, 2417–2419; (c) Dolbier, W. R.; Ait-Mohand, S.;
Schertz, T. D.; Sergeeva, T. A.; Cradlebaugh, J. A.; Mitani, A.; Gard, G. L.; Winter,
R. W.; Thrasher, J. S. J. Fluorine Chem. 2006, 127, 1302–1310; (d) Dolbier, W. R.;
Mitani, A.; Warren, R. D. Tetrahedron Lett. 2007, 48, 1325–1326.
(a) Lal, G. S.; Minnich, K. E. Patent US 6,479,645, 2002; (b) Lal, G. S.; Minnich, K.
E. Patent US 6,870,068, 2005.
Typical procedure: To a CCl3F solution of SF
added triethylborane (0.1 eq) followed by the slow addition of starting material
1 equiv). After stirring at 0 °C for 10–20 min, the reaction mixture was
quenched with sat. NaHCO3 solution, then extracted with dichloromethane.
The combined organic layers were dried over MgSO and concentrated. The
crude product was purified by Kügelrohr distillation or flash chromatography
to afford the liquid, colorless product in good yield.
5
To solution of triethylborane (0.1 equiv) and SF Cl solution in CCl3F (1.3 equiv)
at À40 °C was added the starting material ester (1 equiv). The mixture was
stirred at temperatures between À40 °C and À30 °C for 1 h, and then the bath
was removed and the mixture stirred for another hour as it warmed to rt. The
reaction was quenched with satd NaHCO
organic extracts were washed with water, brine, dried (MgSO
0. Typical procedure: To a solution of the SF Br adduct (1 equiv) in benzene
10 mL) was added DBU (1.2 equiv). The mixture was stirred for 5–20 min at
solution was added to the solution of starting material and
triethylborane at 0 °C, yields of addition product were low and
accompanied by side products. On the other hand, addition of
7
.
.
the starting material to a stirring solution of SF
triethylborane gave clean products and good yields.
Comparison of the use of SF Br solution with that of SF
done using 1d. Reaction using a freshly prepared solution of SF
in CCl
F was effected initially at À40 °C. While the expected ethyl
-chloro-2-methyl-5-pentafluorosulfanylpentanoate, 2e,
formed, the SF Cl reaction required lower temperatures initially
and also longer reaction times. It should be noted that the SF Cl
stock solution in CCl F is stable at temperatures below the boiling
point of SF
Cl (bp À21 °C).
To extend the utility of the SF
5
Br solution and
8
5
Br (1.3 equiv per mL) at 0 °C was
5
5
Cl was
Cl
(
5
4
3
9
4
was
5
9
.
5
3
5
and extracted with CH
2 2
Cl . The
), and filtered.
3
5
Br addition reaction, we also
4
1
1
5
studied the dehydrobromination reaction of the SF
bromo ester.
As shown in Scheme 1, using DBU, dehydrobromination can be
effected (3c and f) in good yields. In our hands, Schotten–
Baumann conditions using KOH to promote dehydrobromination
failed.
5
-containing
(
room temperature. The reaction mixture was quenched with water, then
extracted with dichloromethane. The combined organic layers were dried over
MgSO4 and concentrated in vacuo. The crude product was purified by flash
chromatography to afford the colorless liquid product in good yield.
1. Smith, M. B.; March, J. March’s Advanced Organic Chemistry; Wiley-Interscience:
Hoboken, NJ, 2007.
10
1
1