Bismuth triflate-catalyzed addition of allylsilanes to N- alkoxycarbonylamino sulfones: Convenient access to 3-Cbz-protected cyclohexenylamines

Article abstract of DOI:10.1002/adsc.200900710

Bismuth triflate was found to be an efficient catalyst in the Sakurai reaction of allyltrimethylsilanes with N-alkoxycarbonylamino sulfones. The reaction proceeded smoothly with a low catalyst loading of Bi(OTf) ₃·4H₂O (2-5 mol%) to afford the corresponding protected homoallylic amines in very good yields (up to 96%). A sequential allylation reaction followed by ring-closing metathesis delivers 6-8 membered 3-Cbz-protected cycloalkenylamines.

Full text of DOI:10.1002/adsc.200900710

FULL PAPERS
DOI: 10.1002/adsc.200900710
Bismuth Triflate-Catalyzed Addition of Allylsilanes to
N-Alkoxycarbonylamino Sulfones: Convenient Access to
3-Cbz-Protected Cyclohexenylamines
Thierry Olleviera,* and Zhiya Lia
a
Dꢀpartement de chimie, Universitꢀ Laval, Quꢀbec (Quꢀbec), Canada G1V 0A6
Fax : (+1)-418-656-7916; phone: (+1)-418-656-5034; e-mail: thierry.ollevier@chm.ulaval.ca
Received: October 12, 2009; Published online: December 10, 2009
Supporting information for this article is available on the WWW under
http://dx.doi.org/10.1002/adsc.200900710.
Abstract: Bismuth triflate was found to be an effi- action followed by ring-closing metathesis delivers
cient catalyst in the Sakurai reaction of allyltrime- 6–8 membered 3-Cbz-protected cycloalkenylamines.
thylsilanes with N-alkoxycarbonylamino sulfones.
The reaction proceeded smoothly with a low catalyst
loading of BiACHTUNGTRENNUNG(OTf)3·4H2O (2–5 mol%) to afford the Keywords: N-alkoxycarbonylamino sulfones; allyla-
corresponding protected homoallylic amines in very tion; bismuth; ring-closing metathesis; Sakurai reac-
good yields (up to 96%). A sequential allylation re- tion; silanes
Introduction
water produced during imine formation. Very reactive
N-acyliminium species, easily prepared from stable
The development of new methods for the synthesis of precursors, provide an attractive alternative.[2]
homoallylic amines is an important area of synthetic Scheme 1 illustrates the preparation of the N-acyl-
efforts. Homoallylic amines have attracted much syn-
imine precursor from corresponding aldehydes.[2m] N-
ACHTUNGTRENNUNG
thetic effort and enjoy widespread use in natural Alkoxycarbonylimines have been prepared by basic
product and bioactive molecule synthesis.[1] Among treatment of the N-alkoxycarbonylamino sulfones.
the variety of synthetic methods so far reported, the The corresponding N-alkoxycarbonyliminium deriva-
Lewis acid-catalyzed reaction of imines with silyl nu- tives have been prepared by the use of a Lewis acid
cleophiles provides an efficient route for the synthesis (Scheme 1). Over the past years, some elegant synthe-
of such compounds. However, the instability of carba- ses, including Sakurai and Mannich-type reactions,
mate-protected alkylimines has greatly hampered the have been described, using N-alkoxycarbonylamino
development of catalytic reactions. Therefore, meth- sulfones as substrates.[2] We wish to report herein the
ods involving the in situ generation of imines are Bi
highly attractive, among which the one-pot allylation oxycarbonylamino sulfones. Alkoxycarbonyl-protect-
of imines has been proposed. Yet, most Lewis acids ed homoallylic amines were obtained efficiently in
cannot be used in this reaction because they decom- the presence of 2–5 mol% of Bi(OTf)3·4H2O. Recent-
ACHTUNGTREN(UNNG OTf)3·4H2O-catalyzed Sakurai reaction of N-alk-
AHCTUNGTRENNUNG
AHCTUNGTRENNUNG
pose or deactivate in the presence of the amine or ly, synthetic methods involving Lewis acids such as
Scheme 1. Access to acylimines and iminium species from N-alkoxycarbonylamino aminosulfones.
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TiCl4, SnCl4 , GaCl3, or InCl3 have been reported.[3]
However, the use of Ti(IV) and Sn(IV) salts in stoi-
chiometric quantity or in large excess often restricts
their utilization. The moisture sensitivity of these cat-
alysts and the high cost of some of them restrain their
use as well.
Table 1. Metal salt-catalyzed allylation of sulfone 1a with al-
lyltrimethylsilane.[a]
As a part of our ongoing interest in Bi
lyzed reactions involving silyl nucleophiles, we report
herein a general Bi(OTf)3·4H2O-catalyzed method for
ACHTUNGTRENUN(NG III)-cata-
Entry
Catalyst
Yield of 2a [%][b]
AHCTUNGTRENNUNG
[c]
1
2
3
4
5
6
7
8
9
BiCl3
BiBr3
–
–
–
–
the addition of allylsilanes to N-alkoxycarbonylamino
sulfones. Bismuth salts indeed provide a good alterna-
tive as they have recently attracted attention due to
their low toxicity, low cost and environmentally
benign character.[4] Bismuth salts have been reported
as catalysts for the opening of epoxides,[5] Mukaiyama
aldol reactions,[6] Mannich-type and Sakurai reac-
tions,[7] formation and deprotection of acetals,[8] ether-
ification reactions,[9] hydroamination reactions,[10] Frie-
del–Crafts reactions, and Fries and Claisen rearrange-
[c]
[c]
Bi
Bi
Bi
N
[c]
94
35
57
Zn
Sc
N
U
N
71
E
60[d]
[a]
Conditions: benzyl phenyl(phenylsulfonyl)methylcarb-
AHCTUNGTREGaNNNU mate 1a (1.0 equiv.), allyltrimethylsilane (1.5 equiv.),
ments.[11] Bi
ACHTUNGTRENNUNG(OTf)3·4H2O is particularly attractive be-
cause it is commercially available or can be easily pre-
pared from commercially available compounds. We
metal salt (2 mol%) in dry CH2Cl2 at 228C for 5 h.
Isolated yield.
No trace of product according to H NMR.
Reaction time was 6.5 h.
[b]
[c]
[d]
1
recently reported the BiACHTNUGTRNEUNG(OTf)3·4H2O-catalyzed Sa-
kurai reaction of a variety of aldimines generated in
situ using aldehydes, amines, and allylsilane in a
three-component reaction.[12] A weakness of the one- and starting material was recovered (Table 1, en-
pot Sakurai reaction could be the eventual formation tries 1–4). Other metal triflates such as Zn
ACHTUNGTRENNUNG(OTf)2,
of the homoallylic alcohol as a trace by-product. Sc(OTf)3, Ga(OTf)3 or Cu(OTf)2 also catalyzed this
A
R
ACHTUNGTRENNUNG
These results encouraged us to pursue an alternative reaction but decreased yields were obtained (Table 1,
approach using N-alkoxycarbonylamino sulfones as entries 6–9). Interestingly, using allyltributylstannane
stable imine precursors.
In this paper, we wish to disclose our results in this [2 mol% Bi
area: the development of an efficient Bi(OTf)3·4H2O- homoallylic amine 2a (6%), albeit allyltrimethylger-
as the nucleophile under the same conditions
AHCTUNGTRENNUNG
AHCTUNGTRENNUNG
catalyzed reaction of N-alkoxycarbonylamino sulfones mane afforded the homoallylic amine 2a in good yield
with allyltrimethylsilane. The corresponding amines (79%).
were obtained efficiently in the presence of 2–5 mol%
In regard to the success obtained with sulfone 1a
of BiACHTUNGTRENNUNG(OTf)3·4H2O. Since the original communication derived from benzaldehyde, we studied the scope and
of our work,[13] the scope and generality of the reac- limitations of this reaction with respect to the sulfone
tion have been broadened. A large selection of N-alk- employed in the process [Scheme 1, R1 =Ar, Alk,
ACHTUNGTRENNUNG
mechanism are reported.
addition of allyltrimethylsilane to various N-benzyl-
oxycarbonylamino sulfones 1 proceeded readily em-
ploying Bi(OTf)3·4H2O as the Lewis acid [2–5 mol%
Bi(OTf)3·4H2O, CH2Cl2, 228C, 5–48 h]. Generally, the
corresponding homoallylic amines 2 were obtained in
AHCTUNGTRENNUNG
AHCTUNGTRENNUNG
Results and Discussion
ACHTUNGTRENNUNG
Initially, the allylation reaction was studied with the moderate to good yields (Table 2, entries 1–18). Sul-
N-benzyloxycarbonylamino sulfone derived from ben- fones derived from electron-rich aromatic aldehydes,
zaldehyde and Cbz carbamate (Scheme 1, R1 =Ph, including those from o-substituted benzaldehydes, re-
R=Bn). This sulfone was kept as model sulfone for acted smoothly to give the desired product in moder-
our initial studies. Various catalysts were screened for ate to excellent yields (Table 2, entries 1–3). The reac-
the allylation of benzyl phenyl(phenylsulfonyl)methyl- tion worked well with a variety of sulfones derived
carbamate 1a with allyltrimethylsilane in dichlorome- from electron-poor aromatic aldehydes and the corre-
thane (Table 1). Among the various Bi catalysts sponding homoallylic amines 2 were obtained in mod-
tested, Bi
cient one (Table 1, entry 5). BiCl3, BiBr3, Bi
Bi(OCOCF3)3 did not allow the reaction to proceed pared from p-acetylbenzaldehyde and subsequently
ACHTUNGTRENNUNG
AHCTUNGTRENNUNG
ACHTUNGTRENNUNG
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Bismuth Triflate-Catalyzed Addition of Allylsilanes to N-Alkoxycarbonylamino Sulfones
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Table 2. Bi
ACHTUNGTREN(NGNU OTf)3·4H2O-catalyzed allylation of Cbz-amino sulfones 1 with allyl-
trimethylsilane.[a]
allylated to give 2i with complete chemoselectivity entry 11). In addition, heteroaromatic aldehyde-de-
(Table 2, entry 9). The same selectivity was observed rived sulfones could also serve as substrates in this re-
for the reaction starting from 2-oxopropanal (Table 2, action, giving the corresponding homoallylic amines
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Table 2. (Continued)
[a]
Conditions: sulfone
Bi(OTf)3·4H2O (2 mol%) in CH2Cl2 at 228C.
Isolated yield.
1
(1.0 equiv.), allyltrimethylsilane (1.5 equiv.),
AHCTUNGTRENNUNG
[b]
[c]
The reaction was run with 2 mol% Bi
thylsilane at reflux in CH2Cl2.
ACHTUGNRTEN(NUGN OTf)3·4H2O and 5.0 equiv allyltrime-
in moderate yields (Table 2, entry 10).[13] Aliphatic al- with the corresponding allylation product 7, albeit in
dehydes led to moderate to good yields of 2 (Table 2, low yield (16%). Such a cyclic carbamate resulting
entries 11–18). For selected substrates, higher yields from the internal capture of an intermediate b-silyl
could be obtained using a catalyst loading of 5 mol% cation with the Boc group and concomitant loss of
with 5 equiv. of allyltrimethylsilane in dichlorome- isobutylene had already been reported in the litera-
thane at reflux (Table 2, entries 8 and 11).
ture with tert-butoxycarbonylpiperidine derivatives.[14]
Next, the scope of this allylation reaction was eval-
In order to gain further insights into the allylation
uated with other N-alkoxycarbonylamino sulfones. reaction, we decided to explore the mechanistic as-
Under the optimized reaction conditions, the allyla- pects of the Bi(OTf)3·4H2O-catalyzed process in more
AHCTUNGTRENNUNG
tion of ethyl carbamate-derived sulfones 3 was stud- detail. Given that the latter does not occur in the
ied (Table 3). Generally, the allylation of such sul- presence of N1,N1,N8,N8-tetramethylnaphthalene-1,8-
fones afforded good yields of the corresponding ho- diamine proton spongeꢂ [1 equiv. of 1a, 1.5 equiv of
moallylic carbamates 4. Ethyl carbamate derivatives allyltrimethylsilane, 2 mol% of BiACTHNUTRGNE(UNG OTf)3·4H2O,
could then be deprotected using KOH (60 equiv. 6 mol% of proton spongeꢂ, 228C, 28 h, 99% recovery
KOH, EtOH/H2O, reflux, 74 h, 92% 4a’ from 4a). of 1a],[7] or 2,6-di-tert-butylpyridine [(1 equiv. of 1a,
Aromatic aldehyde-derived sulfones reacted smoothly 1.5 equiv. of allyltrimethylsilane, 2 mol% of
to give 4 in moderate to good yields (Table 3, en- BiACTHNUGTRNEUNG(OTf)3·4H2O, 6 mol% of 2,6-di-tert-butylpyridine,
tries 1–5). With N-ethoxycarbonylamino sulfones de- 228C, 19 h, 100% recovery of 1a],[15] but still proceeds
rived from p-chloro- and p-nitrobenzaldehyde, the re- with K2CO3 used as a proton scavenger [1 equiv. of
action did not proceed at room temperature. Upon 1a, 1.5 equiv. of allyltrimethylsilane, 2 mol% of
reflux of dichloromethane and using 5 mol% Bi- Bi
ACTHUNGTREN(NUNG OTf)3·4H2O, 6 mol% K2CO3, 228C, 19 h, 62% of
ACHTUNGTRENNUNG(OTf)3·4H2O and 5 equiv. allyltrimethylsilane, the ex- 2a] does not indicate unambiguously that triflic acid is
pected homoallylic amines 4b and 4c could be ob- involved in the mechanism. Additionally, the allyla-
tained in good yields (Table 3, entries 2 and 3). The tion reaction does not occur using 2 mol% of HOTf
cyclohexylcarboxaldehyde-derived sulfone 3f reacted or Me3SiOTf. However, when HOTf (6 mol%) is used
smoothly to afford the expected product in good yield as the catalyst, the reaction proceeds to afford the ex-
(Table 3, entry 6). Therefore, this Sakurai-type allyla- pected product 2a, indicating that HOTf is also an ef-
tion could be extended to various carbamate-derived fective catalyst for the transformation (1 equiv. of 1a,
sulfones.
When the Boc carbamate-derived sulfone 5 was 228C, 4 h, 67% of 2a). In order to get further evi-
subjected to the Bi(OTf)3·4H2O-catalyzed allylation dence on the role of HOTf as catalyst, the allylation
1.5 equiv. of allyltrimethylsilane, 6 mol% of HOTf,
AHCTUNGTRENNUNG
conditions (Scheme 2), the cyclic carbamate 6 was ob- of sulfones derived from both 3-pyridylcarboxalde-
tained as the major product (36%, dr=82:18), along hyde and 4-N,N-dimethylaminobenzaldehyde was at-
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Bismuth Triflate-Catalyzed Addition of Allylsilanes to N-Alkoxycarbonylamino Sulfones
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Table 3. BiACHTNUTRGNEUNG(OTf)3·4H2O-catalyzed allylation of ethyl carbamate-derived sulfones 3 with allyltrime-
thylsilane.[a]
[a]
Conditions: sulfone 3 (1.0 equiv.), allyltrimethylsilane (1.5 equiv.), BiACHTUNRTGNE(UNG OTf)3·4H2O (2 mol%) in
CH2Cl2 at 228C.
Isolated yield.
[b]
[c]
Reaction was performed in CH2Cl2 at reflux in the presence of Bi
5.0 equiv. allyltrimethylsilane.
ACHTUNGTREN(NGNU OTf)3·4H2O (5 mol%) with
Scheme 2. BiACHTUNGTRENNUNG(OTf)3·4H2O catalyzed allylation of Boc-amino sulfone 5 with allyltrimethylsilane.
tempted, but no conversion in expected homoallylic Bi
amine was observed. Moreover, Me3SiOTf is an effec- ble since Bi
tive catalyst as well when used in 6 mol% (1 equiv. of cult to handle.
ACHTUNGTRENNUNG
AHCTUNGTRENNUNG
1a, 1.5 equiv. of allyltrimethylsilane, 6 mol% of
Encouraged by our previous results, we studied the
Me3SiOTf, 228C, 5 h, 82% of 2a). Since the allylation allylation of bifunctional sulfones derived from di-
reaction does not occur using 2 mol% of HOTf or
ACHTUNGTRENaNUGN ldehydes such as terephthalaldehyde and isophthalal-
Me3SiOTf and since the chemical yields of the dehyde (Scheme 3). When the classical conditions for
6 mol% HOTf- and Me3SiOTf-catalyzed reactions are the preparation of sulfones were used with terephtha-
lower than when using 2 mol% BiACHTUNTGRNEUNG(OTf)3·4H2O (com- laldehyde, an equimolar mixture of mono and double
pare with Table 1, entry 5), a dual mechanism, namely sulfone (1:0.88) was formed. Unexpectedly, when trifl-
Lewis and Brønsted acid catalysis, cannot be ruled ic acid was used instead of formic acid, the double
out. Despite the fact that Bi
ACHTUNGTREN(NGNU OTf)3·4H2O, HOTf, and sulfone derived from terephthalaldehyde was ob-
TMSOTf could co-exist as catalysts, practical use of tained in high yield [5.0 equiv. of PhSO2Na, 5.0 equiv.
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Scheme 3. BiACHTUNGTRENNUNG(OTf)3·4H2O catalyzed allylation of bifunctional substrates.
of BnOC(O)NH2, THF/H2O/HOTf, 708C, 72 h, 87% lowed the smooth formation of 6- and 7-membered
of 8]. Slight modifications of the conditions applied to substituted Cbz carbamates. The corresponding cyclo-
isophthalaldehyde led to the monosulfone 10 as the octene derivative could be obtained using Grubbs II
only product [2.0 equiv. of PhSO2Na, 2.0 equiv. of catalyst. 3-Cbz-protected cyclohexenylamine 14 has
BnOC(O)NH2, THF/H2O/HCO2H, 708C, 72 h, 85% proven to be a valuable precursor of bicyclic ure-
of 10]. Although the allylation of 8 afforded a poor thanes after further cyclization involving electrophilic
yield of double homoallylic carbamate 9 [Scheme 3, halogen atoms.[16]
Eq. (1)], monosulfone 10 could be advantageously
Other protecting groups could be used and Alloc-
used as a key precursor. Chemoselective mono-allyla- derived sulfones 17a and 17b could be allylated using
tion of 10 using 1.5 equiv. of allyltrimethylsilane our standard procedure (Scheme 5). At this point, use
smoothly afforded aldehyde 11 [Scheme 3, Eq. (2)]. of Alloc instead of Cbz as the amine protecting group
Subsequent allylation of the carbonyl group could be did not change the chemoselectivity of the RCM reac-
obtained by using excess of allyltrimethylsilane tion since no RCM was observed with the Alloc
[Scheme 3, Eq. (3). Formation of the double homoal- group (Scheme 5). Compound 18a indeed could not
lylic amine 13 could be possible via a BiACTHNUTRGNEUNG(OTf)3·4H2O- undergo RCM (Hoveyda–Grubbs II, CH2Cl2, reflux,
catalyzed three-component reaction previously re- 65 h, no conversion). On the other hand, Alloc-pro-
ported by our group [Scheme 4, Eq (4)].[12] However, tected terminal diene 18b afforded smoothly protect-
the relative stereochemistry of products 8, 9, 12, 13 ed cyclohexenylamine 19b (10 mol% Grubbs I,
could not be determined.
CH2Cl2, 228C, 16 h, 79%). The latter one could then
Our allylation method allows the straightforward be easily deprotected using standard Pd(0)-catalyzed
formation of high value precursors for RCM. Our ini- procedure.[17]
tial investigations focused on the reaction of terminal
In order to further extend the generality of our
dienes prepared by our methodology with various method, a functionalized allylsilane was also reacted
metathesis catalysts (Scheme 4). Grubbs I catalysts al- with sulfone 1p. Under the same optimized condi-
tions, the corresponding homoallylic amine was ob-
tained and subsequently subjected to ring-closing
metathesis to afford compound 21 (Scheme 6). Albeit
Grubbs II catalyst afforded the compound in moder-
ate yield (64%), only the dimerization product could
be obtained using Grubbs I catalyst (10% Grubbs I,
PhMe, reflux, 16 h, 37% of dimerization product of
21’, 6% of expected product 21).
Our sequential allylation/ring-closing metathesis
methodology was further applied to the preparation
Scheme 4. Ring-closing metathesis of terminal dienes.
of a key intermediate in the synthesis of calvine
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Bismuth Triflate-Catalyzed Addition of Allylsilanes to N-Alkoxycarbonylamino Sulfones
FULL PAPERS
Scheme 5. Allylation of Alloc-derived sulfones and ring closing metathesis of an Alloc-protected homoallylic amine.[a] Purity
1
of starting material 17b was estimated to be 95% by H NMR.
Scheme 6. BiACHTUNGTRENNUNG(OTf)3·4H2O catalyzed allylation using a functionalized allylsilane.
Scheme 7. Synthesis of calvine.
(Scheme 7). Homoallylic amine 2l was obtained in a ene oxide opening with 23b, followed by ring-closing
moderate yield according to our standard conditions into the 7-membered lactone.[19]
(Table 2, entry 12). Cross-metathesis of 2l with methyl
3-oxopent-4-enoate based on Blechertꢃs work afford-
ed compound 22 in a good yield (86% of 22, E/Z= Conclusions
1.7:1).[18,3d] cis-Disubstituted piperidine 23 was ob-
tained with high yield and diastereoselectivity with In summary, we have found that the Sakurai reaction
partial transesterification occurring during the trans- of N-benzyloxycarbonylamino sulfones proceed
formation. Further transformation of 23 into calvine smoothly in the presence of a catalytic amount of
has already been reported in the literature via ethyl- Bi
ACHTUNGTREN(UNNG OTf)3·4H2O. This method offers several advantag-
es including mild reaction conditions, low catalyst
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Thierry Ollevier and Zhiya Li
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nologies (FQRNT, Quꢀbec, Canada), the Canada Foundation
for Innovation, and Universitꢀ Laval. We thank Rhodia
(Lyon, France) and Sidech s.a. (Tilly, Belgium) for generous
gifts of chemicals.
loading (2–5 mol%), and no formation of by-products.
Moreover, our process involves an environmentally
benign, cheap, and easy to handle catalyst. The
amines, already protected as Cbz derivatives, are
smoothly obtained under mild conditions. Ring-clos-
ing metathesis allowed for rapid construction of di-
verse cyclic compounds with various carbamate sub-
stitution. Because of its numerous benefits, the
BiACHTUNGTRENNUNG(OTf)3·4H2O protocol should find utility in the syn-
thesis of biologically active compounds. Research is
under way to demonstrate other significant applica-
tions of this BiACHTUNGTRENNUNG(OTf)3·4H2O-catalyzed reactions with
silyl nucleophiles.
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Experimental Section
General Procedure for the Bi
Sakurai Reaction
ACHTUNGTREN(NUNG OTf)3·4H2O-Catalyzed
Under an inert atmosphere of argon, allyltrimethylsilane
(0.75 mmol) was added dropwise to solution of
Bi(OTf)3·4H2O (2 mol%) and N-alkoxycarbonylamino sul-
a
ACHTUNGTRENNUNG
fone 1 (0.5 mmol) in dry CH2Cl2 (1.5 mL) at 228C. The mix-
ture was stirred until the reaction was completed as indicat-
ed by TLC. The reaction was quenched with distilled H2O
and extracted with EtOAc. The combined organic phases
were washed with H2O, saturated aqueous NaCl, dried over
MgSO4, and concentrated under vacuum (rotary evapora-
tor). The crude product was purified by column chromatog-
raphy (eluent hexanes/EtOAc 92:8 to 85:15, or toluene).
Spectral data for 1a,[20f] 1l,[20h] 2a,[20a] 2c,[20a] 2e,[20a] 2g,[12]
2i,[20b] 2l,[20i] 2m,[20c] 2n,[20a] 2o,[20c] 2p,[20j] 3a,[20d] 4a,[20a] 4a’,[20l]
5,[20e] 7,[20g] 14,[20j] 15,[20k] 18a,[20m] and 19[20n] agree with those
previously reported in the literature.
Benzyl 1-[4-(trifluoromethyl)phenyl]but-3-enyl-carbamate
(2g):[12] Using the gneral procedure above with the reagents
benzyl phenylsulfonyl(4-(trifluoromethyl)phenyl)methylcar-
bamate 1g (225 mg, 0.5 mmol), allyltrimethylsilane (120 mL,
0.75 mmol), BiACHTUNGTRENNUNG(OTf)3·4H2O (7.0 mg, 2 mol%). The reaction
was stirred for 43 h at 228C. The crude product was purified
by silica gel chromatography (hexanes/EtOAc=90:10) to
afford 2g as a white solid; yield: 102 mg (58%); Rf =0.78
1
(hexanes/EtOAc=70:30); mp 65–678C; H NMR (400 MHz,
CDCl3): d=7.54 (d, J=8.0 Hz, 2H), 7.14–7.41 (m, 7H), 5.60
(tdd, J=10.6, 9.1, 7.1 Hz, 1H), 5.28 (d, J=7.2 Hz, 1H),
4.95–5.16 (m, 4H), 4.72–4.88 (m, 1H), 2.37–2.55 (m, 2H);
13C NMR (100 MHz, CDCl3): d=155.8, 146.3, 136.4, 133.1,
129.7 (q, J=32.6 Hz), 128.7, 128.5, 127.8, 126.7, 125.8 (q, J=
3.8 Hz), 124.3 (q, J=272.7 Hz), 119.4, 67.2, 54.3, 41.1;
19F NMR (376 MHz, CDCl3): d=À62.86; IR (KBr): n=
3283, 1717, 1644 cmÀ1; HR-MS: m/z=350.1362, calcd. for
C19H18F3NO2 [M+H]+: 350.1368.
Nadeau, V. Desyroy, BismuthACTHNUTRGENUGN(III) Trifluoromethanesul-
fonate, in: Electronic Encyclopedia of Reagents for Or-
ganic Synthesis, (Ed.: P. L. Fuchs), John Wiley and
Sons, Chichester.
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Acknowledgements
This work was financially supported by the Natural Sciences
and Engineering Research Council of Canada (NSERC), the
Fonds Quꢀbꢀcois de la Recherche sur la Nature et les Tech-
3258
asc.wiley-vch.de
ꢁ 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Adv. Synth. Catal. 2009, 351, 3251 – 3259

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3259