A polystyrene-supported triflating reagent for the synthesis of aryl triflates

Article abstract of DOI:10.1016/j.tet.2004.10.108

An insoluble polystyrene-supported triflating reagent has been prepared by suspension co-polymerization of N-(4-vinylphenyl)trifluoromethanesulphonimide, styrene and the JandaJel cross-linker. This reagent, in the presence of triethylamine, allows for the efficient synthesis of aryl triflates from a wide range of phenols in a process that permits the desired product to be isolated from the reaction mixture in essentially pure form via several filtration and concentration operations. Adding to the utility of this reagent is its ability to be easily recovered, regenerated and reused. Both soluble and insoluble bifunctional polymers containing trialkylamine moieties in addition to triflimide groups were also prepared and examined as triflating reagents. Unfortunately these reagents afforded only modest yields of the desired products in representative reactions. Graphical Abstract.

Full text of DOI:10.1016/j.tet.2004.10.108

Tetrahedron 61 (2005) 709–715
A polystyrene-supported triflating reagent for the synthesis
of aryl triflates
*
Cecilia Wan Ying Chung and Patrick H. Toy
Department of Chemistry, The University of Hong Kong, Pokfulam Road, Hong Kong, People’s Republic of China
Received 2 August 2004; revised 19 October 2004; accepted 22 October 2004
Available online 24 November 2004
Abstract—An insoluble polystyrene-supported triflating reagent has been prepared by suspension co-polymerization of N-(4-
vinylphenyl)trifluoromethanesulphonimide, styrene and the JandaJelw cross-linker. This reagent, in the presence of triethylamine, allows
for the efficient synthesis of aryl triflates from a wide range of phenols in a process that permits the desired product to be isolated from the
reaction mixture in essentially pure form via several filtration and concentration operations. Adding to the utility of this reagent is its ability
to be easily recovered, regenerated and reused. Both soluble and insoluble bifunctional polymers containing trialkylamine moieties in
addition to triflimide groups were also prepared and examined as triflating reagents. Unfortunately these reagents afforded only modest yields
of the desired products in representative reactions.
q 2004 Elsevier Ltd. All rights reserved.
1. Introduction
use of N-phenyltrifluoromethanesulfonimide (1)12 (Fig. 1)
in conjunction with controlled microwave heating.13 One
drawback associated with the use of reagent 1 is that it and
its by-products can be difficult to separate from the triflate
product. Therefore, both polar analog 2, which not only aids
in product purification but also accelerates its formation,14
and soluble poly(ethylene glycol)-supported analog 3,15
which can facilitate product isolation, have been reported.
While the former has seen widespread use, the latter has not.
Perhaps, one reason for the lack of use of 3 is that it requires
a precipitation operation before it and its by-products can be
removed by filtration, and thus, it is not very amenable to
use in parallel synthesis or with automation equipment.
Therefore, an insoluble polymer-supported reagent that
does not require a precipitation step prior to filtration might
find broader acceptance and utilization. Herein, we wish to
report the synthesis and use of such a reagent.
The use of polymer-supported reagents and catalysts in
polymer-assisted organic synthesis has become commonplace
since they can reduce product purification to simple filtration
and concentration operations and are potentially easily
recycled.1 A vast array of such reagents and catalysts have
been reported that use both insoluble2 and soluble3 polymers
as their carriers and new ones are continually being developed
in order to broaden the range of reactions in which they are
applicable. In this regard, we have a long-standing interest in
the development of both soluble and insoluble polymer-
supported amine,4 fluorinated ketone,5 phosphine,6 sulfide7
and sulfoxide8 reagents. Thus, in our research we have noticed
that a missing tool from the polymeric reagent toolbox is a
readily accessible and easy to use heterogeneous polymer-
supported reagent that allows for the conversion of phenols to
aryl triflates and isolation of the products via simple filtration
and concentration operations.
Aryl triflates are versatile building blocks in organic
synthesis since they participate in a variety of metal
catalyzed carbonylation and coupling reactions.9,10 Thus,
methods and reagents for the synthesis of aryl (an enol)
triflates are constantly being developed and refined. Recent
developments for their preparation include the use of triflic
anhydride in an aqueous biphasic reaction system,11 and the
Figure 1. Current triflimide reagents.
2. Results and discussion
Keywords: Aryl triflates; JandaJel; Triflimide groups.
* Corresponding author. Tel.: C852 2859 2167; fax: C852 2857 1586;
e-mail: phtoy@hku.hk
The preparation of a polymer-supported triflating reagent
requires an aniline polymer as the base material and many
0040–4020/$ - see front matter q 2004 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2004.10.108

710
C. W. Y. Chung, P. H. Toy / Tetrahedron 61 (2005) 709–715
to the polymerization reaction conditions, it was used to
prepare an insoluble polystyrene reagent. Thus, it was
suspension co-polymerized21 with styrene and the flexible
JandaJelw cross-linker22,23 to afford insoluble 5 (JandaJelw-
NTf2) (Scheme 1). Elemental analysis was used to
determine the loading level of 5 to be 1.6 mmol NTf2 gK1
based on the average analysis results for nitrogen and
sulphur content.
Next, we examined the use of 5 in the preparation of a
variety of aryl triflates derived from phenols (6a–i)
substituted with both electron donating and withdrawing
substituents (Table 1). These reactions were performed in
dichloromethane at room temperature using 2 equiv of both
5 and Et3N. Upon the complete disappearance of 6a–i
according to TLC analysis (4–16 h), the reactions were
filtered to remove the insoluble polymer, concentrated in
vacuo and filtered through a short plug of silica gel. Finally,
removal of the solvent afforded triflates 7a–i in essentially
Scheme 1. Synthesis of reagents 5. Reagents and conditions: (a) Et3N
(3 equiv), Tf2O (2 equiv), anhydrous CH2Cl2, 0 8C. (b) PhCl, AIBN, water,
acacia gum, NaCl, 85 8C.
preparations of such polymers have been reported. These
methods include Schmidt rearrangement of a benzyl azide
resin,16 attachment of an aniline derivative to a preformed
polymer,17 and the incorporation of either 4-vinylaniline18
or N-Boc-4-vinylaniline19 in the polymerization process.
While any of these methods could have provided us with a
suitable polymeric starting material, we choose a more
direct route by preparing a functional monomer20 containing
the desired triflimide functional group and incorporating it
into the polymer during the polymerization process.
1
pure form, as determined by H NMR analysis. As can be
seen in Table 1, all substrates were isolated in good to
excellent yield.24
With our success in synthesizing aryl trifliates containing
carbonyl functional groups (7h–i), we were interested to see
if aryl triflates containing aliphatic alcohols could also be
prepared. Gratifyingly, diols 6j–l afforded the correspond-
ing monotriflates 7j–l in moderate to good yield (Table 2)
when the reactions were performed at 50 8C. The structures
of 7j–k were confirmed by their oxidation to the
corresponding aldehyde and ketone (7h), respectively. It
should be noted that these reactions were quite sluggish
Thus, functional monomer 4 was prepared in 90% yield by
reaction of 4-vinylaniline with 2 equiv of Tf2O in the
presence of excess Et3N. After determining the stability of 4
Table 1. Aryl triflate synthesis
Phenol
Triflate
Yield (%)
74
6a
7a
82
6b
7b
81
91
6c
7c
6d
7d
82
81
6e
6f
6g
7e
7f
99
7g
100
6h
7h
99
6i
7i

C. W. Y. Chung, P. H. Toy / Tetrahedron 61 (2005) 709–715
Table 2. Synthesis of aryl triflates containing aliphatic alcohol groups
711
Phenol
Triflate
Yield (%)
48
6j
7j
90
63
6k
7k
7l
6l
even at elevated temperature and 2–5 days and 4 equiv of 5
were required for the complete consumption of the starting
diol. Furthermore, the formation of 7j–l was accompanied
by numerous uncharacterized impurities and these products
required chromatographic purification. One possible expla-
nation for the requirement of a larger excess of 5 for the
synthesis of 7j–l is that the isolated products may have been
formed by hydrolysis of initially generated ditriflate
molecules. Such a reaction pathway would also explain
the complex crude product mixtures obtained for 7j–l.
Having established that 5 is effective and efficient in
converting a broad range of aryl alcohols into the correspond-
ing triflates, we next examined its recyclability. Thus, we
recovered the polymer (a mixture of 5 and 8) at the end of the
reactions and treated it with Tf2O and Et3N. As can be seen in
Table 3, the same sample of 5 can be reused at least three times
for the conversion of 6h to 7h, with only modest decrease in
efficiency. Considering the small scale of the reactions
performed, we consider the reported yields to be approxi-
mately equivalent. However, the reactions of the later cycles
were somewhat sluggish compared to the initial reaction and
required slightly longer reaction times. Nevertheless, it is
important to note that the reactions were efficient in all cases
and only the desired product was observed.
Scheme 2. Synthesis of bifunctional polymers 9 and 11. Reagents and
conditions: (a) PhCl, AIBN, water, acacia gum, NaCl, 85 8C. (b) PhMe,
AIBN, 85 8C.
of both the amine and triflimide functional groups were
determined by elemental analysis to be 1.3 and
0.8 mmol gK1, respectively, based on nitrogen and sulfur
content. To our knowledge only one other such bifunctional
polymer has been reported in the literature and it contains
both basic pyridine moieties and catalytic 4-dimethylamino-
pyridine groups and it was used in esterification reactions.25
Unfortunately, when 9 was used to convert 6h to 7h, only
trace amounts (!5%) of the desired product were observed
by GC analysis, even after extended reaction times at
elevated temperature.
Table 3. Recycling of 5
Cycle
Yield (%)
In order to gain insight into the failure of 9 to be an efficient
triflating reagent, we prepared the soluble, non-cross-linked
polystyrene (NCPS) reagent 11 by co-polymerization of 4,
10, and styrene (Scheme 2), since it would be easier to
characterize spectroscopically and be a homogeneous
reagent. Analysis of 11 by IR, and 1H and 19F NMR
spectroscopy and comparison of this data with that of 4
indicated that the amine and triflimide groups are compat-
ible with one other in the polystyrene matrix. Even when
both 9 and 11 were subjected to the aqueous suspension
polymerization reaction conditions, only minor signals
indicating N–H bonds were observed in the IR spectra.
Thus, premature cleavage of the triflimide groups was
probably not responsible for the poor results with 9.
Reaction of 6h with 11 also only afforded low yield of 7h
1
2
3
4
100
88
95
92
Lastly, we examined the possibility of incorporating basic
amine moieties into 5 so that the triflation reactions might be
performed without the requirement for a base to be added
and thereby possibly eliminate the need for the filtration
through silica gel to obtain pure product. Thus, bifunctional
polymer 9, which contains not only triflimide moieties, but
also basic trialkylamine groups was prepared by the
inclusion of monomer 104 in a 3:2 ratio compared to 4, in
the polymerization process (Scheme 2). The loading levels

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C. W. Y. Chung, P. H. Toy / Tetrahedron 61 (2005) 709–715
(ca. 8%), indicating that the heterogeneous nature of 9 was
also not responsible for its inefficiency. Thus, some
unknown interaction between the amine and triflimide
functional groups must be responsible for the failure of the
bifunctional polymers 9 and 11 to be useful triflating
reagents.
(100 mL) at K78 8C was added triflic anhydride (15.2 mL,
90.3 mmol). The reaction mixture was stirred at this
temperature for 1 h and then warmed to rt and stirred for
1 h more. At this time, the reaction mixture was diluted with
CH2Cl2 (400 mL) and then washed sequentially with
saturated aqueous NaHCO3 (150 mL) and brine (150 mL).
The organic phase was dried over MgSO4, filtered and
concentrated in vacuo. The crude product was purified by
silica gel chromatography (5% EtOAc/hexanes) to afford 4
as white solid (15.58 g, 90%). 1H NMR (300 MHz, CDCl3)
d 5.43 (d, 1H, JZ10.9 Hz), 5.85 (d, 1H, JZ17.6 Hz), 6.73
(dd, 1H, JZ17.6, 10.9 Hz), 7.35 (d, 2H, JZ8.5 Hz), 7.51 (d,
2H, JZ8.6 Hz). 13C NMR (75 MHz, CDCl3) d 113.3,
113.3–123.3 (JCFZ323.2 Hz), 127.9, 131.1, 131.5, 135.3,
141.8. 19F NMR (376 MHz, CDCl3) d K71.1. IR (KBr,
cmK1): 3073, 1633, 1507, 1122, 741, 661. HR EI-MS: calcd
for C10H7NS2O4F6, 382.9720; found 382.9713.
3. Conclusions
We have prepared the new, insoluble polystyrene-supported
triflimide reagent 5 and demonstrated its usefulness in the
synthesis of a range of aryl triflates, including ones that
contain aliphatic hydroxyl groups. This reagent is recyclable
at least three times with no significant decrease in its
efficiency. Finally, we report the synthesis of bifunctional
polymeric reagents 9 and 11. Unfortunately, these are not as
efficient as 5 is in the preparation of aryl triflates, which may
be due to micro-environmental factors that arise from
bringing the amine and triflimide moieties together in the
same polymer matrix.25
The stability of 4 to the suspension polymerization
conditions was examined by placing it in the acacia solution
described below. This was heated to 85 8C for 20 h. At this
time, TLC analysis indicated only the presence of
unchanged 4. No more highly polar compounds were
observed.
Finally, we have attempted to use 5 in the synthesis of enol
triflates from ketones, and in sample reactions the products
formed required chromatographic purification, as is the case
when 1 and 2 are used. Thus, considering the heterogeneity
of 5 and the prolonged reaction times required compared to
homogeneous small molecule reagents, we found no
advantages to using 5 in enol triflate synthesis and therefore
limited our study to the preparation of aryl triflates.
Significantly, when 5 is used in such applications, the
work-up and isolation of the aryl triflate product is simple,
amenable to being performed in parallel in an automated
fashion and can be completed in a matter of minutes. Thus,
it should be a useful tool in parallel synthesis, where the
ability to simply isolate products with high purity is
essential.
4.1.2. JandaJelw-NTf2 (5). A solution of acacia gum (6.0 g)
and NaCl (3.8 g) in warm deionized water (45 8C, 150 mL)
was placed in a 150 mL flanged reaction vessel equipped
with a mechanical stirrer and deoxygenated by purging with
N2 for 2 h.26 A solution of 4 (5.74 g, 15.0 mmol), styrene
(4.26 g, 41.0 mmol), 1,4-bis(4-vinylphenoxy)butane22d
(0.33 g, 1.1 mmol), and AIBN (0.2 g, 1.3 mmol) in
chlorobenzene (10 mL) was injected into the rapidly stirred
aqueous solution. The resulting suspension was heated at
85 8C for 20 h. At this time the crude polymer was collected
and washed with hot water (3!100 mL) and then placed in
a Soxhlet extractor and washed with THF for 24 h. The
beads were then washed sequentially with diethyl ether
(250 mL), and hexane (250 mL), and then dried in vacuo for
24 h to afford 5 (8.5 g, 85%). IR (KBr, cmK1): 3068, 3029,
1603, 1501, 1128, 760, 701. Elemental analysis was used to
determine the nitrogen content (2.3%) and the sulfur content
4. Experimental
4.1. General
(9.6%), and thus the loading level of 5 was 1.6 mmol gK1
.
All reagents were obtained from the Aldrich, Lancaster or
Acros chemical companies and were used without further
purification. All moisture sensitive reactions were carried
out in dried glassware under a N2 atmosphere. Tetrahydro-
furan was distilled under a N2 atmosphere over sodium and
benzophenone. Dichloromethane was distilled under a N2
atmosphere over calcium hydride. Merck silica gel 60
(230–400 mesh) was used for chromatography. Thin layer
chromatography analysis was performed using glass plates
coated with silica gel 60 F254. Gas chromatographic
analyses were performed using an RTX-5 column with a
Thermo Finnigan Focus chromatograph. NMR spectra were
recorded using either a Bruker DRX 300 or an AV400
spectrometer. Chemical shift data is expressed in ppm with
reference to TMS. HR EI-MS data was recorded on a
Finnigan MAT 96 mass spectrometer.
4.1.3. JandaJelw-(CH2NEt2)NTf2 (9). A solution of acacia
gum (6.0 g) and NaCl (3.8 g) in warm deionized water
(45 8C, 150 mL) was placed in a 150 mL flanged reaction
vessel equipped with a mechanical stirrer and deoxygenated
by purging with N2 for 2 h. A solution of 4 (3.83 g,
10.0 mmol), 104 (2.84 g, 15 mmol), styrene (3.33 g,
32.0 mmol), 1,4-bis(4-vinylphenoxy)butane22d (0.34 g,
1.1 mmol), and AIBN (0.2 g, 1.3 mmol) in chlorobenzene
(10 mL) was injected into the rapidly stirred aqueous
solution. The resulting suspension was heated at 85 8C for
20 h. At this time the crude polymer was collected and
washed with hot water (3!100 mL) and then placed in a
Soxhlet extractor and washed with THF for 24 h. The beads
were then washed sequentially with diethyl ether (250 mL),
and hexane (250 mL), and then dried in vacuo for 24 h to
afford 9 (5.4 g, 54%). IR (KBr, cmK1): 3498, 3027, 1606,
1510, 1145, 761, 700. Elemental analysis was used to
determine the nitrogen content (2.9%) and the sulfur content
(5.0%), and thus the loading levels of the amine and
4.1.1. N-(4-Vinylphenyl)trifluoromethanesulfonimide
(4). To a solution of 4-aminostyrene (5.40 g, 45.2 mmol)
and Et3N (18.8 mL, 135.5 mmol) in anhydrous CH2Cl2

C. W. Y. Chung, P. H. Toy / Tetrahedron 61 (2005) 709–715
713
triflimide groups in 9 were 1.3, and 0.8 mmol gK1
respectively.
,
139.5, 148.0. 19F NMR (376 MHz, CDCl3) d K73.0. HR EI-
MS: calcd for C9H9SO3F3, 254.0224; found 254.0226.
4.2.5. Characterization data for 7e.10e Colorless oil. H
1
4.1.4. NCPS-(CH2NEt2)NTf2 (11). To a solution of styrene
(1.67 g, 16.0 mmol), 10 (1.42 g, 7.5 mmol) and 4 (1.79 g,
5.0 mmol) in toluene (20 mL) was added AIBN (0.024 g,
0.14 mmol). The mixture was purged with N2 for 30 min
and the solution was stirred at 85 8C for 24 h. The solution
was concentrated in vacuo and the residue was taken up in
2 mL of THF. This solution was added dropwise to a
vigorously stirred cold Et2O (0 8C, 200 mL). The white
precipitate was filtered and dried to afford 11 as a white
NMR (300 MHz, CDCl3) d 7.23 (d, 2H, JZ9.0 Hz), 7.43 (d,
2H, JZ9.0 Hz). 13C NMR (75 MHz, CDCl3) d 112.7–125.5
(JCFZ318.9 Hz), 123.1, 130.8, 134.7, 148.3. 19F NMR
(376 MHz, CDCl3) d K72.8. HR EI-MS: calcd for C7H4-
SClO3F3, 259.9522; found 259.9526.
1
4.2.6. Characterization data for 7f.11 Colorless oil. H
NMR (400 MHz, CDCl3) d 7.16 (d, 2H, JZ8.8 Hz), 7.56 (d,
2H, JZ8.9 Hz). 13C NMR (100 MHz, CDCl3) d 117.5–
123.9 (JCFZ318.9 Hz), 122.4, 123.4, 133.8, 148.9. 19F
NMR (376 MHz, CDCl3) d K72.8. HREI-MS: calcd for
C7H4SBrF3O3, 303.9017; found 303.9014.
1
powder (1.6 g, 32%). H NMR (400 MHz, CDCl3) d 1.02–
1.60 (br, 10H), 1.63–2.41 (br, 36H), 2.82–3.32 (br, 4H),
3.81–4.38 (br, 1H), 6.12–7.75 (br, 20H). 19F NMR
(376 MHz, CDCl3) d K71.1. IR (KBr, cmK1): 3504, 3028,
1603, 1506, 1129, 762, 702.
4.2.7. Characterization data for 7g.11 Yellow solid (mp
52–56 8C). 1H NMR (300 MHz, CDCl3) d 7.49 (d, 2H, JZ
8.9 Hz), 8.37 (d, 2H, JZ8.9 Hz). 13C NMR (75 MHz,
CDCl3) d 112.7–125.4 (JCFZ318.9 Hz), 122.9, 126.4,
147.5, 153.5. 19F NMR (376 MHz, CDCl3) d K73.0. HR
EI-MS: calcd for C7H4NSF3O5, 270.9762; found 270.9760.
4.2. General procedure for aryl triflate synthesis using 5
Reagent 5 (0.47 g, 0.75 mmol) and Et3N (0.1 mL,
0.75 mmol) were added to a solution of 6 (0.375 mmol) in
anhydrous CH2Cl2 (5 mL). The reaction mixture was
shaken at rt until TLC analysis indicated the complete
disappearance of 6 (4–16 h). At this time, the resin was
filtered off and the filtrate was concentrated in vacuo. The
resulting residue was then filtered through a plug of silica
gel using CH2Cl2. Removal of the solvent afforded 7 that
4.2.8. Characterization data for 7h.29 Yellow oil. 1H
NMR (300 MHz, CDCl3) d 2.63 (s, 3H), 7.39 (d, 2H, JZ
8.8 Hz), 8.07 (d, 2H, JZ8.9 Hz). 13C NMR (75 MHz,
CDCl3) d 27.0, 112.7–125.4 (JCFZ318.8 Hz), 122.0, 130.9,
137.3, 152.8, 196.4. 19F NMR (376 MHz, CDCl3) d K72.8.
HR EI-MS: calcd for C9H7SO4F3, 268.0017; found
268.0015.
1
was determined to be essentially pure by H NMR.
The syntheses of 7j–l were performed at 50 8C and required
4, 5, and 2 days, respectively, for the complete disappear-
ance of starting material. These products were purified by
silica gel chromatography.
4.2.9. Characterization data for 7i.30 White solid (mp
100–104 8C. H NMR (300 MHz, CDCl3) d 2.62 (s, 3H),
1
3.98 (s, 3H), 7.32 (d, 1H, JZ8.4 Hz), 7.57 (dd, 1H, JZ8.4,
2.0 Hz), 7.65 (d, 1H, JZ1.9 Hz). 13C NMR (100 MHz,
CDCl3) d 26.5, 56.4, 112.3, 114.0–123.5 (JCFZ318.5 Hz),
122.6, 122.5, 137.8, 141.9, 151.7, 196.3. 19F NMR
(376 MHz, CDCl3) d K73.8. HR EI-MS: calcd for
C10H9SO5F3, 298.0123; found 298.0116.
1
4.2.1. Characterization data for 7a.11 Colorless oil. H
NMR (300 MHz, CDCl3) d 7.25–7.29 (m, 2H), 7.34–7.49
(m, 3H). 13C NMR (75 MHz, CDCl3) d 112.8–125.6 (JCF
Z
318.7 Hz), 121.7, 128.8, 130.7, 150.1. 19F NMR (376 MHz,
CDCl3) d K72.9. HR EI-MS: calcd for C7H5SO3F3,
225.9911; found 225.9913.
4.2.10. Characterization data for 7j. Yellow oil. 1H NMR
(300 MHz, CDCl3) d 2.10 (br, 1H), 4.70 (s, 2H), 7.25 (dd,
2H, JZ6.8, 2.2 Hz), 7.43 (d, 2H, JZ8.8 Hz). 13C NMR
(100 MHz, CDCl3) d 64.0, 114.0–123.5 (JCFZ318.8 Hz),
121.4, 128.5, 141.4, 148.8. 19F NMR (376 MHz, CDCl3) d
K72.9. HR EI-MS: calcd for C8H7SO4F3, 256.0017; found
256.0019.
1
4.2.2. Characterization data for 7b.27 Colorless oil. H
NMR (300 MHz, CDCl3) d 3.82 (s, 3H), 6.80 (t, 1H, JZ
2.3 Hz), 6.85–6.94 (m, 2H), 7.33 (t, 1H, JZ8.3 Hz). 13C
NMR (100 MHz, CDCl3) d 55.7, 107.5, 113.3, 114.2,
114.0–123.5 (JCFZ319.0 Hz), 130.6, 150.3, 160.9. 19F
NMR (376 MHz, CDCl3) d K72.9. HR EI-MS: calcd for
C8H7SO4F3, 256.0017; found 256.0019.
For structural proof, 7j was oxidized to the corresponding
aldehyde using PDC (2.5 equiv) in CH2Cl2 at rt for 2 h (83%
1
4.2.3. Characterization data for 7c.11 Colorless oil. H
1
yield). Characterization data for this aldehyde: H NMR
NMR (400 MHz, CDCl3) d 2.37 (s, 3H), 7.15 (d, 2H, JZ
8.6 Hz), 7.23 (d, 2H, JZ8.7 Hz). 13C NMR (100 MHz,
CDCl3) d 20.9, 114.0–123.6 (JCFZ318.8 Hz), 121.0, 130.7,
138.5, 147.6. 19F NMR (376 MHz, CDCl3) d K72.9. HR EI-
MS: calcd for C8H7SO3F3, 240.0068; found 240.0071.
(300 MHz, CDCl3) d 7.47 (d, 2H, JZ8.6 Hz), 8.01 (d 2H,
JZ8.6 Hz), 10.05 (s, 1H). 13C NMR (125 MHz, CDCl3) d
114.9–122.5 (JCFZ318.9 Hz), 122.3, 131.8, 136.0, 153.2,
190.1. 19F NMR (376 MHz, CDCl3) d K72.7. HR EI-MS:
calcd for C8H5SO4F3, 253.9861; found 253.9860.
1
4.2.4. Characterization data for 7d.28 Colorless oil. H
4.2.11. Characterization data for 7k. Yellow oil. 1H NMR
(300 MHz, CDCl3) d 1.49 (d, 3H, JZ6.5 Hz), 2.07 (br, 1H),
4.93 (q, 1H, JZ6.5 Hz), 7.24 (dd, 2H, JZ6.8, 2.0 Hz), 7.45
(dd, 2H, JZ6.8, 1.7 Hz). 13C NMR (100 MHz, CDCl3) d
25.3, 69.4, 114.0–123.5 (JCFZ318.8 Hz), 121.3, 127.2,
NMR (400 MHz, CDCl3) d 2.26 (s, 3H), 2.28 (s, 3H), 6.99
(dd, 1H, JZ8.3, 2.6 Hz), 7.03 (d, 1H, JZ2.4 Hz), 7.17 (d,
1H, JZ8.3 Hz). 13C NMR (75 MHz, CDCl3) d 19.6, 20.2,
112.8–125.6 (JCFZ318.7 Hz), 118.7, 122.4, 131.3, 137.5,

714
C. W. Y. Chung, P. H. Toy / Tetrahedron 61 (2005) 709–715
146.3, 148.6. 19F NMR (376 MHz, CDCl3) d K73.0. HR EI-
MS: calcd for C9H9SO4F3, 270.0174; found 270.0168.
3815–4195. (b) Clapham, B.; Reger, T. S.; Janda, K. D.
Tetrahedron 2001, 57, 4637–4662. (c) Benaglia, M.; Puglisi,
¨
A.; Cozzi, F. Chem. Rev. 2003, 103, 3401–3429. (d) Brase, S.;
Lauterwasser, F.; Ziegert, R. E. Adv. Synth. Catal. 2003, 345,
869–929.
For structural proof 7k was oxidized to 7h using PDC
(2.5 equiv) in CH2Cl2 at rt for 3 h (87% yield). Character-
ization data for this product agreed with that which was
previously observed.
2. (a) Leadbeater, N. E.; Marco, M. Chem. Rev. 2002, 102,
3217–3273. (b) McNamara, C. A.; Dixon, M. J.; Bradley, M.
Chem. Rev. 2002, 102, 3275–3299. (c) Fan, Q.-H.; Li, Y.-M.;
Chan, A. S. C. Chem. Rev. 2002, 102, 3385–3465.
4.2.12. Characterization data for 7l. White solid (mp 32–
35 8C). 1H NMR (400 MHz, CDCl3) d 1.57 (s, 6H), 7.22 (d,
2H, JZ8.9 Hz), 7.56 (d, 2H, JZ8.9 Hz). 13C NMR
3. (a) Toy, P. H.; Janda, K. D. Acc. Chem. Res. 2000, 33,
546–554. (b) Dickerson, T. J.; Reed, N. N.; Janda, K. D. Chem.
Rev. 2002, 102, 3325–3343. (c) Bergbreiter, D. E. Chem. Rev.
2002, 102, 3345–3383.
(75 MHz, CDCl3) d 32.1, 72.6, 112.8–125.5 (JCF
Z
318.7 Hz), 121.3, 126.9, 148.6, 150.0. 19F NMR (376 MHz,
CDCl3) d K72.9. HR EI-MS: calcd for C10H11SO4F3,
284.0330; found 284.0363.
4. Toy, P. H.; Reger, T. S.; Janda, K. D. Org. Lett. 2000, 2,
2205–2207.
5. Kan, J. T. W.; Toy, P. H. Tetrahedron Lett. 2004, 45,
6357–6359.
4.3. Procedure for regeneration and reuse of polymer 5
6. (a) Choi, M. K. W.; He, H. S.; Toy, P. H. J. Org. Chem. 2003,
68, 9831–9834. (b) Zhao, L.-J.; He, H. S.; Shi, M.; Toy, P. H.
J. Comb. Chem. 2004, 6, 680–683.
The polymeric reagent recovered from the aryl triflate
synthesis reactions (a mixture of 5 and 8) was treated with
triflic anhydride (3 equiv) and Et3N (3 equiv) in anhydrous
CH2Cl2 at K78 8C for 1 h and then warmed to room
temperature and stirred for 18 h more. The polymer 5 was
filtered and washed as before.
7. Choi, M. K. W.; Toy, P. H. Tetrahedron 2004, 60, 2875–2879.
8. Choi, M. K. W.; Toy, P. H. Tetrahedron 2003, 59, 7171–7176.
9. For a general review of synthetic transformations involving
aryl triflates, see: Ritter, K. Synthesis 1993, 735–762.
10. (a) For the use of aryl triflates in Stille coupling reactions, see:
Echavarren, A. M.; Stille, J. K. J. Am. Chem. Soc. 1987, 109,
5478–5486. (b) For examples of solid-phase Stille coupling
reactions involving aryl triflates, see: Forman, F. W.; Sucholeiki,
I. J. Org. Chem. 1995, 60, 523–528. (c) For examples of the
synthesis of aryl sulfides from aryl triflates, see: Zheng, N.;
McWilliams, J. C.; Fleitz, F. J.; Armstrong, J. D., III; Volante,
R. P. J. Org. Chem. 1998, 63, 9606–9607. (d) For examples of
aryl triflate arsination, see: Kwong, F. Y.; Lai, C. W.; Chan,
K. S. J. Am. Chem. Soc. 2001, 123, 8864–8865. (e) For
examples of aryl trflate phosphination, see: Kwong, F. Y.; Lai,
C. W.; Yu, M.; Tian, Y.; Chan, K. S. Tetrahedron 2003, 59,
10295–10305. (f) For an example of aryl triflate cyanation,
see: Zhang, A.; Neumeyer, J. L. Org. Lett. 2003, 5, 201–203.
(g) For an example of a B-alkyl Suzuki coupling reaction
involving an aryl triflate, see: Molander, G. A.; Yun, C.-S.;
Ribagorda, M.; Biolatto, B. J. Org. Chem. 2003, 68,
5534–5539. (h) For an example of a Suzuki coupling reaction
involving an aryl triflate, see: Cioffi, C. L.; Spencer, W. T.;
Richards, J. J.; Herr, R. J. J. Org. Chem. 2004, 69, 2210–2212.
(i) For examples of coupling aryl triflates with silicates, see:
Seganish, W. M.; DeShong, P. J. Org. Chem. 2004, 69,
1137–1143. (j) For examples of butatrienyl carbinols coupling
The same sample of 5 was used four times to prepare 7h. For
each triflation cycle, the reaction was monitored by TLC
analysis and the product was purified and characterized as
before.
4.4. Use of polymers 9 and 11 for aryl triflate synthesis
Reagent 9 (2 equiv of –NTf2, 3 equiv of –CH2NEt2) was
used in CH2Cl2, DMF, 1,4-dioxane at rt (70 8C for the later
two solvents) for the conversion of 6h to 7h. Samples of the
reaction solutions were intermittently analyzed by gas
chromatography to determine the extent of reaction. After
up to 5 days, 7h was formed in less than 5% yield under all
reaction conditions.
Reagent 11 (2 equiv of –NTf2, 3 equiv of –CH2NEt2) was
used in CH2Cl2 at rt. After 3 days, analysis by gas
chromatography indicated that 7h was formed in only 8%
yield.
Acknowledgements
´
to aryl triflates to form furans, see: Aurrecoechea, J. M.; Perez,
E. Tetrahedron 2004, 60, 4139–4149.
This research was supported financially by the University of
Hong Kong, and the Research Grants Council of the Hong
Kong Special Administrative Region, P. R. of China
(Project No. HKU 7027/03P). We also thank Mr. Bob
Wandler and the Aldrich Chemical Co. for providing many
of the reagents used in this research.
11. Frantz, D. E.; Weaver, D. G.; Carey, J. P.; Kress, M. H.;
Dolling, U. H. Org. Lett. 2002, 4, 4717–4718.
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