Regio- and stereoselective heck α-arylation of cinnamyl alcohols

Article abstract of DOI:10.1055/s-0028-1087912

The Heck reaction of cinnamyl alcohols with aryl iodides has been investigated using n-Bu₄NOAc as the base in toluene. Under these conditions, the reaction affords regio- and stereoselectively (Z)-2,3-diarylallylic alcohols in moderate to good yields. Experimental evidence suggests that the observed selectivity in formation of the vinylic substitution products is kinetic in origin under these conditions and that both the base and the solvent play a key role. Georg Thieme Verlag Stuttgart.

Full text of DOI:10.1055/s-0028-1087912

620
LETTER
Regio- and Stereoselective Heck a-Arylation of Cinnamyl Alcohols
a
-Arylat
l
ion of
C
a
innamyl
A
r
lcohols ia Ambrogio, Sandro Cacchi,* Giancarlo Fabrizi, Antonella Goggiamani, Simona Sgalla
Dipartimento di Chimica e Tecnologie del Farmaco, Università degli Studi ‘La Sapienza’, P. le A. Moro 5, 00185 Rome, Italy
Fax +39(06)49912780; E-mail: sandro.cacchi@uniroma1.it
Received 3 November 2008
phenylated ketones as the main products with (E)-1,3-
diphenyl-2-propen-1-ol and (E)-4-phenyl-3-buten-2-ol
and a nonregioselective formation of phenylated alde-
hydes with crotyl alcohol.5 The cis- and trans-crotyl alco-
Abstract: The Heck reaction of cinnamyl alcohols with aryl iodides
has been investigated using n-Bu4NOAc as the base in toluene. Un-
der these conditions, the reaction affords regio- and stereoselective-
ly (Z)-2,3-diarylallylic alcohols in moderate to good yields.
Experimental evidence suggests that the observed selectivity in for- hols were shown to undergo enantioselective phenylation
mation of the vinylic substitution products is kinetic in origin under
these conditions and that both the base and the solvent play a key
role.
to afford the corresponding b-phenyl aldehyde in low
yield and ee using iodobenzene, Pd(dba)2, and phosphin-
ite-oxazoline ligands derived from D-glucosamine in the
presence of Ag2CO3.6 Recently, the reaction of the parent
Key words: palladium, arylation, cinnamyl alcohols, Heck reaction
cinnamyl alcohol with aryl halides has been investigated
in molten salts, showing that a-arylation is preferentially
The palladium-catalyzed reaction of aryl halides with al- observed under these conditions.7 However, a few exam-
lylic alcohols unsubstituted at the b-carbon has been ex- ples were investigated and, in addition, the use of molten
tensively investigated in the past years1 and, depending on salts as the reaction medium may be inconvenient when
reaction conditions, has been shown to represent a useful scaling up is needed or in industrial applications. There-
tool for the preparation of b-aryl aldehydes and ketones or fore, the development of a simple and effective protocol
cinnamyl alcohol derivatives (Scheme 1). The new C–C to control the regio- and stereochemistry of this reaction
bond is usually formed at the b-position with high regio- would be desirable.
selectivity.
In this context, based on our long-standing interest in the
Heck reactions of substituted olefins and our results in the
arylation of a,b-unsaturated ketones,8 methyl cinna-
O
mates,9 acrolein dimethyl acetal,10 the THP derivative of
Ar
R
OH
allyl alcohol,11 and domino Heck reaction–cyclization
processes12 in the presence of n-Bu4NOAc (which was
found to play a key role in controlling the regio- and/or
stereoselectivity of these reactions), we became interested
in investigating more in detail this chemistry using the
same base. Herein we report the results of this study.
Pd catalyst
Pd catalyst
ArX
OH
R
Ar
R
R = H, alkyl
Scheme 1
Cinnamyl alcohols were prepared in 70–80% overall
yields by a process involving a Heck reaction of aryl ha-
lides with methyl acrylate followed by treatment of the
crude mixture containing the vinylic substitution product
with DIBAL-H.13
In contrast, the arylation of allylic alcohols containing a b-
substituent has attracted much less attention and, after the
pioneering and independent work of Heck2 and Chalk3 de-
scribing the formation of mixtures of arylated carbonyl
derivatives in the reaction of halobenzenes with allylic al-
cohols bearing a terminal methyl group, there is little
known on this chemistry. For example, treatment of cin-
namyl alcohol with excess iodobenzene under an inert at-
mosphere or in the presence of air afforded mixtures of
arylated products.4 Formation of arylated cinnamyl alco-
hol and carbonyl derivatives was observed and the latter
were isolated as the main components. The reaction
showed also a strong tendency to generate the new C–C
bond preferentially at the b-carbon under both conditions,
though it appears to be more marked in the presence of air.
The Heck arylation of b-substituted allylic alcohols with
iodobenzene in molten n-Bu4NBr was reported to give b-
Preliminary investigation into the process utilized 4-iodo-
anisole, a model of electron-rich aryl iodides, and cin-
namyl alcohol. Reactions were carried out by using
phosphine-free Pd(OAc)2 as source of Pd(0) species. The
product distributions obtained under a variety of condi-
tions suggested that several competing processes were op-
erating, including the arylation at the a- and b-olefinic
carbons and oxidation processes. Some of the most signif-
icant results are summarized in Table 1.
Under Jeffery conditions14 a mixture of a- and b-aryl de-
rivatives was obtained with a slight preference for form-
ing the new C–C bond at the b-carbon (Table 1, entry 1).
Aldehydes 6a and 7a were isolated in 42% overall yield,
5a (the likely precursor of 6a) was not detected, and the
arylated derivatives at the a-carbon 3a and 4a (its oxida-
SYNLETT 2009, No. 4, pp 0620–0624
x
x.
x
x.
2
0
0
9
Advanced online publication: 16.02.2009
DOI: 10.1055/s-0028-1087912; Art ID: G34208ST
© Georg Thieme Verlag Stuttgart · New York

LETTER
a-Arylation of Cinnamyl Alcohols
621
tion product) were isolated in 31% overall yield. Alde- These outcomes suggest that both the base and the solvent
hyde products were the main components. The absence of can play a key role in controlling the regiochemistry of the
detectable amounts of 5a seems to imply that its oxidation carbopalladation step and that in the presence of n-
under these reaction conditions is faster than that of 3a. Bu4NOAc and toluene the phenyl substituent exerts a
The stereochemistry of 3a and 4a was assigned by NOE stronger directing effect than the hydroxyl group does. A
experiments.
possible explanation is that the acetate ligand bound to
palladium in a bidentate mode, as suggested by computa-
tional studies,11 combined with an apolar solvent prevents
the hydroxyl group from establishing a Pd–O bond in the
p-complex preceding the formation of the carbopallada-
tion adduct, thus inhibiting a coordination-controlled ad-
dition step. It follows that the reaction of the cinnamyl
alcohol with the s-aryl palladium complex formed in situ
affords the p-complex A that is converted into the vinylic
substitution products via the transition states B or C, with
the transition state B being favored by the fact that it min-
imizes steric strain by locating the aryl residue on the less
hindered end of the carbon–carbon double bond
(Scheme 2).
Using Et3N as the base provided poor results. Both in
DMF and in toluene the reaction afforded complex mix-
tures of aldehyde products, including condensed deriva-
tives that we have not further investigated: 3a (Table 1,
entry 2) and 3a and 6a (Table 1, entry 3) were the sole
products that could be clearly detected and isolated, albeit
in low yields.
Notably, when the reaction was performed in the presence
of n-Bu4NOAc in DMF, a marked preference for the ary-
lation at the a-carbon was observed, the a- to b-arylation
ratio being 1.96 (Table 1, entry 4) as compared to 0.74 un-
der Jeffery conditions (Table 1, entry 1). The arylated cin-
namyl alcohol 3a was isolated in 43% yield as single
stereoisomer. Switching to n-Bu4NOAc in toluene in-
creased the a- to b-arylation ratio to 4.86 and 3a was iso-
lated in a satisfactory 60% yield (Table 1, entry 6). No
evidence of its stereoisomer formation was attained.
It seems that using n-Bu4NOAc in toluene has also the ad-
ditional beneficial effect of limiting the oxidation process-
es. We have made only a partial investigation of the
oxidation leading to the formation of 4a and 6a.15 Their
Table 1 The Influence of Solvents, Bases, and Additives in the Palladium-Catalyzed Reaction of 4-Iodoanisole and Ethyl 4-Iodobenzoate
with Cinnamyl Alcohola
ArI
+
Ph
OH
1
2
Ar
Ar
H
H
Ar
Ar
Ar
O
+
+
+
+
Ph
Ph
Ph
O
Ph
Ph
OH
O
OH
H
3
4
5
6
7
Entry
Aryl iodide 2
Solvent
Base
Additive
Time (h)
Yield (%)
b-Arylation
a-Arylation
3
4
5
6
7
1
2
3
4
5
6
7
4-MeOC6H4I
(2a)
DMF
DMF
toluene
DMF
DMF
NaHCO3
Et3N
Et3N
n-Bu4NOAc
n-Bu4NOAc
n-Bu4NOAc
n-Bu4NOAc
n-Bu4NCl
–
–
–
7.5
24c
24d
3
8
3
22
27
11
43
49
60
62
9
4
10
8
–
trace
23
19
–
–
8
4
4
4
9
12
24
7
–
4
–
3
5
n-Bu4NCl
toluene
toluene
n-Bu4NCl
3
–
10
8
9
10
4-EtO2CC6H4I
(2b)
toluene
toluene
toluene
n-Bu4NOAc
n-Bu4NOAc
n-Bu4NOAc
–
28
30
57
52
3
8
–
–
–
–
–
–
–
n-Bu4NCl
n-Bu4NCl
28
6
40e,f
–
11
a Unless otherwise stated, reactions were carried out under an argon atmosphere at 90 °C on a 0.732 mmol scale using cinnamyl alcohol (1
equiv), 4-iodoanisole or ethyl 4-iodobenzoate (1.5 equiv), Pd(OAc)2 (0.03 equiv), base (2 equiv), and of n-Bu4NCl (1 equiv, when added) in
solvent (2 mL).
b Yields are given for isolated products.
c Aldehydes 4, 6, and 7 were obtained in 19% overall yield.
d Cinnamyl alcohol was recovered in 48% yield.
e In the presence of 2 equiv of n-Bu4NCl.
f In the presence of 3 equiv of 4-EtO2CC6H4I.
Synlett 2009, No. 4, 620–624 © Thieme Stuttgart · New York

622
I. Ambrogio et al.
LETTER
Ar2I
+
Ar1
OH
To determine whether the stereochemical outcome of the
reaction might involve a kinetic-controlled process –
which includes a regioselective syn-carbopalladation fol-
lowed by a syn-b-elimination of HPdX species – or a ther-
modynamic process with an equilibration step following
the initial elimination reaction, we carried out the follow-
ing experiments. Cinnamyl alcohol and 4-iodoanisole
were treated with n-Bu4NOAc in toluene in the presence
of a pure sample of 3b (Scheme 4, path a). The product
distribution and the overall yield of the arylation reaction
were similar to those reported in Table 1, entry 6. Com-
pound 3b was recovered in almost quantitative yield and
its stereochemistry was maintained. A similar result was
obtained with the E-isomer 3b¢ (Scheme 4, path b), pre-
pared via Heck arylation of (Z)-3-phenyl-2-propen-1-ol21
with ethyl 4-iodobenzoate under our standard conditions.
Pd(OAc)2
Bu4NOAc
toluene
Me
O
O
Pd Ar2
Ar1
OH
A
Me
OH
Me
O
O
Ar2
Pd
O
O
Pd Ar2
Ar1
Ar1
OH
B (favored)
C (disfavored)
These results [including the formation of 3b¢ from (Z)-3-
phenyl-2-propen-1-ol] support the notion that under our
conditions no stereochemical isomerization takes place
after the b-elimination of HPd from carbopalladation ad-
ducts and that the stereoselectivity is consequently origi-
nated during the vinylic substitution process.
OH
Ar2
Ar1
OH
Ar1
Ar2
Scheme 2
OMe
formation via the reaction shown in Scheme 3 (path a)16
appears unlikely because the reaction of 4-iodoanisole
and cinnamyl alcohol under the conditions shown in entry
6 (Table 1) yielded only trace amounts of anisole, one of
the products of the oxidation process. Even the involve-
ment of atmospheric oxygen17 was ruled out on the ground
that careful deoxygenation of the reaction mixture did not
produce appreciable changes in the reaction outcome. It
seems therefore that oxidation products are generated
through the oxidative addition of the corresponding allylic
alcohols to Pd(0) species followed by the elimination of
HPdH18,19 (Scheme 3, path b) or (for compound 6a) a pal-
ladaoxetane intermediate20 (Scheme 3, path c).
+
Ph
OH
I
C6H4-4-CO2Et
Ph
Ph
OH
C6H4-4-CO2Et
OH
3b
a
b
3b'
3b (recovered in almost
quantitative yield)
3b' (recovered in almost
quantitative yield)
a
+
+
H
XPdAr2
arylation products
of cinnamyl alcohol
arylation products
of cinnamyl alcohol
HAr2
+
R
OPdAr
or
– HX
– Pd(0)
PdH
R
R
O
O
Scheme 4
b
H
Pd(0)
Ar1
OH
R
OH
R
OPdH
– HPdH
When ethyl 4-iodobenzoate – a model of electron-poor
aryl iodides – was treated with cinnamyl alcohol under the
best conditions found for 4-iodoanisole, the correspond-
ing vinylic substitution derivative 3b was isolated only in
30% yield (Table 1, entry 8). Addition of ligands such as
bipyridine, tris(2,4,6-trimethoxyphenyl)phosphine, P(t-
Bu3)3 [added to the reaction mixture as HP(t-Bu3)3BF4
salt]22 or utilization of the Herrmann catalyst gave unsat-
isfactory results. A remarkable increase of the yield was
observed instead by adding n-Bu4NCl (Table 1, entry 9).
We then came back to 4-iodoanisole to investigate wheth-
er the addition of n-Bu4NCl could give 3a in higher yield.
However, no distinctive advantages were observed. In
contrast, the desired product was isolated in lower yield
along with a significant amount of oxidation products in
Ar2
c
Ar2
XPdAr2
Ar1
Ar1
OH
O
Pd
PdX
Ar1
H
Ar1
Ar2
O
Ar2
OPdH
– HPdH
R = Ar1CH=CH
Scheme 3
Synlett 2009, No. 4, 620–624 © Thieme Stuttgart · New York

LETTER
a-Arylation of Cinnamyl Alcohols
623
Table 2 The Palladium-Catalyzed Reaction of Cinnamyl Alcohols with Aryl Iodidesa
Entry
Cinnamyl alcohol 1
Aryl iodide 2
Time (h)
Yield (%) of
(Z)-2,3-diarylallylic alcohol 3b
1
2
(1a)
(1b)
4-MeOC6H4I
2a
2b
3
3a
3b
60
57
Ph
OH
1a
4-EtO2CC6H4I
4-MeOC6H4I
28c
F3C
OH
3
2a
24
3c
79
4
5
1b
1b
4-EtO2CC6H4I
PhI
2b
2c
24
24
3d
3e
51
52
OH
6
(1c)
(1d)
4-MeOC6H4I
2a
24
3f
54
HO
7
8
1c
3-MeC6H4I
2d
2a
22
24
3g
3h
56
47
OH
4-MeOC6H4I
9
1d
1d
3-MeOC6H4I
4-FC6H4I
2e
2f
32
29
3i
3j
46
44
10
OH
11
12
13
(1e)
(1f)
4-MeOC6H4I
4-MeC6H4I
4-MeC6H4I
2a
2g
2g
54
22
26
3k
3l
60
52
58
MeO
1e
OH
3m
Cl
14
15
1f
3-MeOC6H4I
4-FC6H4I
2e
2f
30
48
3n
3o
68
56
1f
a Unless otherwise stated, reactions were carried out under an argon atmosphere at 90 °C on a 0.732 mmol scale using cinnamyl alcohol
(1 equiv), aryl iodide (1.5 equiv), Pd(OAc)2 (0.03 equiv), and n-Bu4NOAc (2 equiv) in toluene (2 mL).
b Yields are given for isolated products.
c In the presence of 1 equiv of n-Bu4NCl.
DMF (Table 1, entry 5) whereas in toluene the yield of 3a experimental evidence suggest that the observed selectiv-
was only slightly higher (Table 1, entry 7). In addition, ity in formation of the vinylic substitution products is
even the reaction of ethyl 4-iodobenzoate with 1b did not kinetic in origin under these conditions and that both the
afford better results in the presence of n-Bu4NCl. There- base and the solvent play a key role in controlling the
fore, apart from the reaction of ethyl 4-iodobenzoate with reaction outcome. Although yields are only moderate to
cinnamyl alcohol, we decided to omit n-Bu4NCl when we good, reaction conditions are simple, and the process may
next extended the reaction to other aryl iodides and cin- provide an easy access to this class of compounds.
namyl alcohols.23 Nevertheless, it might be advisable to
evaluate each time the effectiveness of using n-Bu4NCl.
Acknowledgment
The results of our preparation studies are summarized in
Table 2. Under our ‘optimal’ conditions, the reaction af-
fords regio- and stereoselectively (Z)-2,3-diarylallylic al-
cohols in moderate to good yields with a variety of
cinnamyl alcohols and electron-rich, electron-poor, and
neutral aryl iodides.
Work carried out in the framework of the National Project ‘Stereo-
selezione in Sintesi Organica. Metodologie ed Applicazioni’ sup-
ported by the Ministero dell’Università e della Ricerca Scientifica e
Tecnologica and by the University ‘La Sapienza’.
References and Notes
In conclusion, we have shown that the reaction of cin-
namyl alcohols with aryl iodides in the presence of n-
Bu4NOAc in toluene affords the corresponding a-arylated
derivatives regio- and stereoselectively. Several pieces of
(1) For a recent review, see: Muzart, J. Tetrahedron 2005, 61,
4179.
(2) Melpolder, J. B.; Heck, R. F. J. Org. Chem. 1976, 41, 265.
(3) Chalk, A. J.; Magennis, S. A. J. Org. Chem. 1976, 41, 273.
Synlett 2009, No. 4, 620–624 © Thieme Stuttgart · New York

624
I. Ambrogio et al.
LETTER
(4) Bagnell, L.; Kreher, U.; Strauss, C. R. Chem. Commun.
2001, 29.
(5) Bouquillon, S.; Ganchegui, B.; Estrine, B.; Hénin, F.;
Muzart, J. J. Organomet. Chem. 2001, 634, 153.
NMR (376.5 MHz, CDCl3): d = –62.8. MS: m/e (rel. int.) =
202 (3) [M+], 133 (12), 69 (100), 57 (21), 51 (18).
(14) (a) Jeffery, T. J. Chem. Soc., Chem. Commun. 1984, 1287.
(b) Jeffery, T. Tetrahedron Lett. 1985, 26, 2667.
(6) Yonehara, K.; Mori, K.; Hashizume, T.; Chung, K.-G.; Ohe,
K.; Uemura, S. J. Organomet. Chem. 2000, 603, 40.
(7) Calò, V.; Nacci, A.; Monopoli, A.; Ferola, V. J. Org. Chem.
2007, 72, 2596.
(8) Amorese, A.; Arcadi, A.; Bernocchi, E.; Cacchi, S.; Cerrini,
S.; Fedeli, W.; Ortar, G. Tetrahedron 1989, 45, 813.
(9) Battistuzzi, G.; Cacchi, S.; Fabrizi, G. Synlett 2002, 439.
(10) (a) Battistuzzi, G.; Cacchi, S.; Fabrizi, G. Org. Lett. 2003, 5,
777. (b) Battistuzzi, G.; Cacchi, S.; Fabrizi, G.; Bernini, R.
Synlett 2003, 1133.
(15) For recent reviews on the palladium-catalyzed oxidation of
alcohols, see: (a) Muzart, J. Tetrahedron 2003, 59, 5789.
(b) Stoltz, B. M. Chem. Lett. 2004, 33, 362. (c) Sigman,
M. S.; Jensen, D. R. Acc. Chem. Res. 2006, 39, 221.
(16) Tamaru, Y.; Yamada, Y.; Inoue, K.; Yamamoto, Y.;
Yoshida, Z.-I. J. Org. Chem. 1983, 48, 1286.
(17) Blackburn, T. F.; Shwartz, J. J. Chem. Soc., Chem. Commun.
1977, 157.
(18) Rao, V. S.; Perlin, A. S. J. Org. Chem. 1982, 47, 367.
(19) One of the referees suggested that the alcohols 3 and 5 are
probably partly present as alkoxides (formed via
(11) Ambrogio, I.; Fabrizi, G.; Cacchi, S.; Henriksen, S. T.;
Fristrup, P.; Tanner, D.; Norrby, P.-O. Organometallics
2008, 27, 3187.
deprotonation by the acetate anions) that can either react
with HPdOAc or HPdI formed in the Heck reaction to
generate HPdOCH2R. b-Hydride elimination generates the
corresponding aldehyde and HPdH.
(12) (a) Battistuzzi, G.; Cacchi, S.; De Salve, I.; Fabrizi, G.;
Parisi, L. M. Adv. Synth. Catal. 2005, 347, 308.
(b) Battistuzzi, G.; Bernini, R.; Cacchi, S.; De Salve, I.;
Fabrizi, G. Adv. Synth. Catal. 2007, 349, 297.
(13) Typical Procedure for the Preparation of Cinnamyl
Alcohols – Preparation of 1b
(20) Cacchi, S.; Ciattini, P. G.; Morera, E.; Ortar, G. Tetrahedron
Lett. 1992, 33, 3073.
(21) (Z)-3-Phenyl-2-propen-1-ol was prepared via selective
hydrogenation of 3-phenyl-2-propyn-1-ol according to the
method described by: Denis, J.-N.; Greene, A. E.; Serra,
A. A.; Luche, M.-J. J. Org. Chem. 1986, 51, 46.
(22) Netherton, M.; Fu, G. C. Org. Lett. 2001, 3, 4295.
(23) Typical Procedure for the Preparation of (Z)-a-Aryl-
cinnamyl Alcohols – Preparation of 3c
A Carousel Reaction Tube (Radley Discovery), equipped
with a magnetic stirrer, was charged with 1-(trifluoro-
methyl)-3-iodobenzene (1.0 g, 3,68 mmol), methyl acrylate
(993 mL, 11,02 mmol), Et3N (1.53 mL, 11.02 mmol), and
Pd(OAc)2 (24.8 mg, 0.11 mmol) in DMF (4 mL). The
reaction mixture was warmed at 80 °C and stirred at the same
temperature for 1.5 h under argon. After cooling, the
reaction mixture was diluted with EtOAc, washed twice with
a NaCl solution, dried over Na2SO4, and concentrated under
reduced pressure. The residue was dissolved in toluene (4
mL), the resultant solution was cooled at –78 °C, DIBAL-H
(1 M in hexane, 8 mL, 8.08 mmol) was added, and the
reaction mixture was stirred at this temperature for 2 h under
argon. After this time the reaction mixture was warmed at
r.t., diluted with EtOAc, washed twice with a NaCl solution,
dried over Na2SO4, and concentrated under reduced
pressure. The residue was purified by chromatography on
SiO2 (n-hexane–EtOAc, 60:40) to afford 522 mg (70%
yield) of 1b as oil. IR (neat): 3343, 2925, 1440, 1332, 1124
cm–1; 1H NMR (400.13 MHz, CDCl3): d = 7.63 (s, 1 H), 7.55
(d, J = 7.6 Hz, 1 H), 7.50 (d, J = 7.7 Hz, 1 H), 7.45 (t, J = 7.6
Hz, 1 H), 6.67 (d, J = 16.0 Hz, 1 H), 6.45 (dt, J1 = 16.0 Hz,
J2 = 5.4 Hz, 1 H), 4.37 (t, J = 4.3 Hz, 2 H), 1.61 (br s, 1 H).
13C NMR (100.6 MHz, CDCl3): d = 137.6, 131.1 (q, J = 33.0
Hz), 130.7, 129.6, 129.4, 129.1, 124.20 (q, J = 3.7 Hz),
A Carousel Reaction Tube (Radley Discovery), equipped
with a magnetic stirrer, was charged with 1b (60 mg, 0.297
mmol), 4-iodanisole (104 mg, 0.445 mmol), Pd(OAc)2 (2
mg, 0.009 mmol), and n-Bu4NOAc (179 mg, 0.594 mmol) in
toluene (1 mL). The reaction mixture was warmed to 90 °C
and stirred at the same temperature for 24 h under argon.
After this time the reaction mixture was diluted with EtOAc,
washed twice with a NaCl solution, dried over Na2SO4, and
concentrated under reduced pressure. The residue was
purified by chromatography on SiO2 (n-hexane–EtOAc,
85:15) to afford 72 mg (79% yield) of 3c. Mp 80–82 °C. IR
(KBr): 3297, 2923, 1606, 1513, 1330 cm–1. 1H NMR (400.13
MHz, CDCl3): d = 7.68 (s, 1 H), 7.63 (d, J = 8.0 Hz, 1 H),
7.56–7.54 (m, 4 H), 6.68 (d, J = 12.0 Hz, 2 H), 6.92 (s, 1 H),
4.67 (s, 2 H), 3.86 (s, 3 H), 1.58 (br s, 1 H). 13C NMR (100.6
MHz,CDCl3): d = 159.6, 141.0, 137.8, 132.3, 132.0, 130.7
(q, J = 32.0 Hz), 128.7, 128.1, 127.7, 125.6 (q, J = 3.8 Hz),
124.0 (q, J = 272.6 Hz), 123.7 (q, J = 3.8 Hz), 114.1, 60.1,
55.2. 19F (376.5 MHz, CDCl3): d = –62.6. MS: m/e (rel. int.):
308 (4) [M+], 145 (4), 89 (12), 77 (16), 59 (100), 51 (26).
124.2 (q, J = 272.3 Hz), 123.19 (q, J = 3.8 Hz), 63.4. 19
F
Synlett 2009, No. 4, 620–624 © Thieme Stuttgart · New York

Copyright of Synlett is the property of Georg Thieme Verlag Stuttgart and its content may not
be copied or emailed to multiple sites or posted to a listserv without the copyright holder's
express written permission. However, users may print, download, or email articles for
individual use.