General reaction conditions for the palladium-catalyzed vinylation of aryl chlorides with potassium alkenyltrifluoroborates

Article abstract of DOI:10.1021/jo901681s

(Chemical Equation Presented) Activated and deactivated aryl and heteroaryl chlorides are efficiently cross-coupled with potassium vinyl- and alkenyltrifluoroborates using 4-hydroxyacetophenone oxime derived palladacycle as precatalyst in 1 to 3 mol % Pd loading, Binap as ligand, and Cs ₂CO₃ as base in DMF at 120°C. The reactions can also be performed using Pd(OAc)₂ as Pd(0) source, although with lower efficiency. Bidentate ligands such as Binap and dppp can be used, the former being the best choice. Only in the case of deactivated aryl chlorides should the reaction temperature be increased to 160°C to achieve good yields. The corresponding cross-coupled compounds, such as styrenes, stilbenes, and alkenylarenes, are obtained in good yields and with high regio- and diastereoselectivity. 2009 American Chemical Society.

Full text of DOI:10.1021/jo901681s

pubs.acs.org/joc
General Reaction Conditions for the Palladium-Catalyzed Vinylation of
Aryl Chlorides with Potassium Alkenyltrifluoroborates
ꢀ
Emilio Alacid and Carmen Najera*
´
ꢀ
Departamento de Quımica Organica, Facultad de Ciencias, and Instituto de Sıntesis Organica (ISO),
ꢀ
´
Universidad de Alicante, Apdo. 99, 03080-Alicante, Spain
cnajera@ua.es
Received July 31, 2009
Activated and deactivated aryl and heteroaryl chlorides are efficiently cross-coupled with potassium
vinyl- and alkenyltrifluoroborates using 4-hydroxyacetophenone oxime derived palladacycle as
precatalyst in 1 to 3 mol % Pd loading, Binap as ligand, and Cs2CO3 as base in DMF at 120 °C. The
reactions can also be performed using Pd(OAc)2 as Pd(0) source, although with lower efficiency.
Bidentate ligands such as Binap and dppp can be used, the former being the best choice. Only in the
case of deactivated aryl chlorides should the reaction temperature be increased to 160 °C to achieve
good yields. The corresponding cross-coupled compounds, such as styrenes, stilbenes, and alkeny-
larenes, are obtained in good yields and with high regio- and diastereoselectivity.
Introduction
intended, the trivinylboroxine-pyridine complex must be
used exclusively reacting with aryl iodides and bromides, due
to its rather low reactivity and stability.5 Potassium organo-
trifluoroborates have emerged as an excellent alternative to
boronic acids and boronate esters due to their stability and
versatility in cross-coupling reactions.6 Several types of
potassium organotrifluoroborates such as aryl,7 cycloalkyl,8
dialkylaminomethyl,9 and alkoxymethyl10 derivatives
have been successfully employed for the coupling of aryl
and heteroaryl chlorides. However, attempted cross-coupling
During the last 10 years, considerable progress has been
achieved in the palladium-catalyzed cross-coupling reactions
of activated and deactivated aryl chlorides with organobor-
on compounds leading to biaryls.1 However, alkenylation
reactions devoted to the synthesis of styrenes, stilbenes,
alkenylarenes, and related alkenylheterocycles using aryl
and heteroaryl chlorides remain challenging.2 Few examples
have been described using bulky N-heterocyclic carbenes3 or
an electron-rich ferrocenylphosphine4 as ligands for the
reaction of alkenylboronic acids with aryl chlorides to afford
stilbenes and alkenylarenes. When simple vinylations are
(5) (a) Kerins, F.; O’Shea, D. F. J. Org. Chem. 2002, 67, 4968–4971.
(b) Mantel, M. L. H.; Sobjerg, L. S.; Huynh, T. H. V.; Ebran, J.-P.; Lindhardt,
A. T.; Nielsen, N. C.; Skrydstrup, T. J. Org. Chem. 2008, 73, 3570–3573.
ꢀ
(c) Alacid, E.; Najera, C. J. Organomet. Chem. 2009, 649, 1658–1665.
^
288–325. (b) Doucet, H. Eur. J. Org. Chem. 2008, 2013–2030. (c) Molander,
G. A.; Ellis, N. Acc. Chem. Res. 2007, 40, 275–286. (d) Stefani, H. A.; Cella,
R.; Vieira, A. S. Tetrahedron 2007, 63, 3623–3658. (e) Molander, G. A.;
^
Figueroa, R. Aldrichimica Acta 2005, 38, 49–56. (f) Darses, S.; Genet, J.-P.
Eur. J. Org. Chem. 2003, 4313–4327.
(7) (a) Ito, T.; Iwai, T.; Mizuno, T.; Ishino, Y. Synlett 2003, 1435–1438.
(b) Border, T. E.; Buchwald, S. L. Org. Lett. 2004, 6, 2649–2652. (c) Kudo,
N.; Perseghini, M.; Fu, G. Angew. Chem., Int. Ed. 2006, 45, 1282–1284.
*To whom correspondence should be addressed. Fax: þ34 965903549.
E-mail: cnajera@ua.es.
(6) For reviews, see: (a) Darses, S.; Genet, J.-P. Chem. Rev. 2008, 108,
(1) For recent reviews, see: (a) Lipshutz, B. H.; Ghoral, S. Aldrichimica
Acta 2008, 41, 59–72. (b) Martin, R.; Buchwald, S. L. Acc. Chem. Res. 2008,
41, 1461–1473. (c) Alonso, F.; Beletskaya, I. P.; Yus, M. Tetrahedron 2008,
64, 3047–3101. (d) Yin, L.; Liebscher, J. Chem. Rev. 2007, 107, 133–173.
(e) Phan, N. T. S.; Van Der Sluys, M.; Jones, C. W. Adv. Synth. Catal. 2006,
348, 609–679. (f) Corbet, J. P.; Mignani, G. Chem. Rev. 2006, 106, 2651–2710.
(g) Nicolaou, K. C.; Bulger, P. G.; Sarlah, D. Angew. Chem., Int. Ed. 2005, 44,
4442–4489. (h) Metal-Catalyzed Cross-Coupling Reactions; De Meijere, A.,
Diederich, F., Eds.; Wiley-VCH: Weinheim, Germany, 2004. (i) Miura, M.
Angew. Chem., Int. Ed. 2004, 43, 2201–2203. (j) Littke, A. F.; Fu, G. C. Angew.
Chem., Int. Ed. 2002, 41, 4176–4211.
€
(d) Lysen, M.; Kohler, K. Synthesis 2006, 692–698. (e) O’Brien, C. J.;
Kantchen, A. A. B.; Valente, C.; Hadei, N.; Chass, G. A.; Lough, A.;
Hopkinson, A. C.; Organ, M. G. Chem.;Eur. J. 2006, 12, 4743–4748.
ꢀ
(f) Alacid, E.; Najera, C. Org. Lett. 2008, 10, 5011–5014. (g) Savall, B. M.;
(2) For a review, see: Denmark, S. E.; Butler, C. R. Chem. Commun. 2009,
20–33.
Fontimayor, J. R. Tetrahedron Lett. 2008, 49, 6667–6669.
(8) (a) Dreher, S. D.; Dormer, P. G.; Sandrock, D. L.; Molander, G. A.
J. Am. Chem. Soc. 2008, 130, 9257–9259. (b) Molander, G. A.; Gormisky,
P. E. J. Org. Chem. 2008, 73, 7481–7485.
(9) Molander, G. A.; Gormisky, P. E.; Sandrock, D. L. J. Org. Chem.
2008, 73, 2052–2057.
(10) Molander, G. A.; Canturk, B. Org. Lett. 2008, 10, 2135–2138.
(3) (a) Song, C.; Ma, Y. D.; Chai, Q.; Ma, C.; Jiang, W.; Andrus, M. B.
Tetrahedron 2005, 61, 7438–7446. (b) Navarro, O.; Marion, N.; Mei, J. G.;
Nolan, S. P. Chem.;Eur. J. 2006, 12, 5142–5148.
(4) Thimmaiah, M.; Zhang, X.; Fang, S. Tetrahedron Lett. 2008, 49,
5605–5607.
DOI: 10.1021/jo901681s
r
Published on Web 10/02/2009
J. Org. Chem. 2009, 74, 8191–8195 8191
2009 American Chemical Society

ꢀ
Alacid and Najera
JOCArticle
TABLE 1. Reaction Conditions Optimization for Cross-Coupling of 4-Chloroacetophenone with Potassium Vinyl- and Styryltrifluoroboratesa
entry
R
cat. (mol % Pd)
ligand (mol %)
base
solvent
time
30 mind
14 h
no.
yield (%)b
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
Ph
Ph
Ph
Ph
Ph
1 (2)
1 (2)
1 (3)
1 (3)
1 (3)
1 (3)
1 (3)
1 (3)
1 (3)
1 (3)
1 (3)
1 (3)
Pd(OAc)2 (3)
PdCl2 (3)
1 (1)
K2CO3
K2CO3
K2CO3
Cs2CO3
Cs2CO3
Cs2CO3
Cs2CO3
Cs2CO3
Cs2CO3
Cs2CO3
Cs2CO3
Cs2CO3
Cs2CO3
Cs2CO3
Cs2CO3
Cs2CO3
Cs2CO3
Cs2CO3
Cs2CO3
Cs2CO3
Cs2CO3
Cs2CO3
Cs2CO3
H2Oc
H2Oc
H2Oc
H2Oc
DMF
DMF
DMF
DMF
DMF
DMF
DMF
DMF
DMF
DMF
DMF
DMF
DMF
DMF
DMF
DMF
DMF
DMF
DMF
2aa
2aa
2aa
2aa
2aa
2aa
2aa
2aa
2aa
2aa
2aa
2aa
2aa
2aa
2aa
2aa
2aa
2aa
2ab
2ab
2ab
2ab
2ab
25
10
45
(S)-Binap (6)
(S)-Binap (6)
Ph3P (9)
(S)-Binap (6)
(S)-Binap (6)
Ph3P (9)
XantPhos (6)
Ruphos (6)
dppf (6)
30 mind
30 mind
30 mind
30 midd
18 h
57
62e
74f
99 (89)
81 (68)
0
18 h
18 h
18 h
18 h
18 h
18 h
18 h
18 h
20 h
18 h
18 h
16 h
18 h
18 h
18 h
18 h
0
0
93
dppp (6)
(S)-Binap (6)
(S)-Binap (6)
(S)-Binap (2)
dppp (2)
(S)-Binap (2)
(S)-Binap (2)
(S)-Binap (6)
(S)-Binap (6)
(S)-Binap (6)
(S)-Binap (6)
(S)-Binap (6)
96
85
80g
66
1 (1)
Pd(OAc)2 (1)
PdCl2 (1)
1 (3)
Pd(OAc)2 (3)
PdCl2 (3)
1 (1)
57h
29i
91
99
92
86
42
Pd(OAc)2 (1)
aReaction conditions: 4-chloroacetophenone (32 μL, 0.25 mmol), CH2dCHBF3K (40 mg, 0.3 mmol), cat. (see column), ligand (see column), base
b
1
(0.75 mmol) and solvent (1 mL) at 120 °C under Ar. Isolated yield of the crude product determined by H NMR. In parentheses, yield after flash
chromatography. cTBAB (0.25 mmol) was added. dHeating in a microwave reactor (30 W, 14.5 psi) with air stream cooling. e3% of 4,40-bisacetylstilbene
f
g
h
was obtained. 2% of 4,40-bisacetylstilbene was also obtained. 3% of 4,40-bisacetylstilbene and 2% of acetophenone were obtained. 2% of 4,40-
bisacetylstilbene and 4% of acetophenone were obtained. i1% of 4,40-bisacetylstilbene and 6% of acetophenone were obtained.
of potassium vinyltrifluoroborate with aryl chlorides only
succeeded with 4-chloroacetophenone using the combina-
tion PdCl2 (2 mol %) and RuPhos (6 mol %) as catalyst,
Cs2CO3 as base in THF/H2O (9:1) at 85 °C during 22 h.11
Under these conditions, the corresponding 4-acetylstyrene
was obtained in 65% yield and the formation of the homo-
coupled 4,40-bisacetylbiphenyl and Heck’s product 4,40-bi-
sacetylstilbene was also observed.
Recently, we have described the cross-coupling of po-
tassium vinyl- and alkenyltrifluoroborates with aryl and
heteroaryl bromides using 1 mol % Pd loading of
4-hydroxyacetophenone oxime derived palladacycle or
Pd(OAc)2 as precatalysts, K2CO3 as base, and TBAB as
additive under water reflux to afford styrenes, stilbenoids,
and alkenylarenes.12 However, these phosphine-free reac-
tion conditions failed with aryl chlorides. We report here
the first alkenylation reaction of aryl and heteroaryl chlor-
ides with potassium vinyl and alkenyltrifluoroborates
using palladacycle 1 and (S)-Binap as catalysts in organic
solvents.
Results and Discussion
Initial studies were performed with 4-chloroacetophenone
and potassium vinyltrifluoroborate using 1 mol % of com-
plex 1 as catalyst (Table 1). Using the same reaction condi-
tions as those previously reported for aryl bromides,12
K2CO3 as base and tetra-n-butylammonium bromide
(TBAB) in refluxing water under conventional or microwave
heating, very low yields of the coupling product 2aa were
obtained (Table 1, entries 1 and 2). A higher yield (up to
57%) was observed after addition of 6 mol % of a bidentate
phosphane, such as (S)-Binap (6 mol %) and 1 (3 mol % Pd)
as catalysts and K2CO3 or Cs2CO3 as base (Table 1, entries 3
and 4), although the reaction failed under MW heating when
aqueous THF10 or dioxane was used as solvents. The rest of
the experiments were performed using Cs2CO3 (3 equiv) as
base. When DMF was used as solvent in the presence of
triphenylphosphane and (S)-Binap, 62 and 74% yields of
2aa were obtained, respectively (Table 1, entries 5 and 6),
whereas quantitative crude yields were obtained using
(S)-Binap under conventional heating after 18 h reaction
time (Table 1, entry 7). The same reaction was performed
with racemic Binap, affording product 2aa in 97% crude
yield.13 When the reaction was performed with 2 mol % of a
complex generated by a 1:1 palladacycle/Binap mixture, the
reaction afforded product 2aa in only 41% yield. A lower
crude yield (81%) was observed when triphenylphosphane
(11) Molander, G. A.; Brown, A. R. J. Org. Chem. 2006, 71, 9681–9686.
ꢀ
(12) Alacid, E.; Najera, C. J. Org. Chem. 2009, 74, 2321–2327.
(13) The use of (S)-Binap instead of racemic Binap was due its availability
in large quantities in our lab.
8192 J. Org. Chem. Vol. 74, No. 21, 2009

ꢀ
Alacid and Najera
JOCArticle
TABLE 2. Cross-Coupling of Aryl and Heteroaryl Chlorides with Potassium Alkenyltrifluoroboratesa
J. Org. Chem. Vol. 74, No. 21, 2009 8193

ꢀ
Alacid and Najera
JOCArticle
TABLE 2. Continued
aReaction conditions: organic chloride (0.25 mmol), alkenylBF3K (0.3 mmol), Cs2CO3 (249 mg, 0.75 mmol), complex 1 (see column), and DMF
(1 mL) at 120 °C under Ar. bIsolated yield after flash chromatography. In parentheses, yield determined by 1H NMR of the crude product. c3% of
regioisomeric 2-(4-acetylphenyl)dec-1-ene (3ac) was obtained. d5% of 2-(1-naphthyl)styrene was obtained. e3% of 2-(1-naphthyl)dec-1-ene (3db) was
obtained. fAt 160 °C. g4% of 4,40-dimethoxystilbene was obtained. h2% of anisole was obtained. i8% of 2-(4-methoxyphenyl)styrene (3eb) was obtained.
j7% of 2-(4-methoxyphenyl)dec-1-ene (3ec) was obtained. k6% of 2,20-dichlorostilbene was obtained.
was used instead of Binap under conventional thermal
conditions (Table 1, entry 8). In both cases, product 2aa
was isolated in 89 and 68% yield after purification (Table 1,
compare entries 7 and 8). The role of Binap seems to be
important as stabilizer of the in situ generated Pd(0) atoms,
whereas the palladacycle is less prone to generate Pd(0) when
coordinated by the ligand.
(Table 2). In the case of the coupling of 4-chloroacetophe-
none and potassium vinyltrifluoroborate, a 2 mol % Pd
loading was used, affording 2aa in 82% isolated yield
(Table 2, entry 1), the loading of Pd(OAc)2 being increased
to 3 mol % in order to achieve similar yields (Table 2,
entry 2). In the case of potassium (E)-styryl- and (E)-dec-
1-enyltrifluoroborate (3 mol % of Pd), products 2ab and 2ac
were regio- and stereoselectively obtained, respectively,
either with palladacycle 1 or with Pd(OAc)2 (Table 2, entries
3 or 4 and 5 or 6). 4-Benzoylchlorobenzene gave styrene 2ba
and stilbene 2bb in high yields using similar conditions than
with 4-chloroacetophenone (Table 2, entries 7 and 8). After
the coupling of 4-chlorobenzonitrile and 1-naphthyl chlor-
ide, the corresponding styrenes 2ca and 2da, stilbenes 2cb
and 2db, and dec-1-enylbenzenes 2cc and 2dc, respectively,
were obtained in good yields under the same reaction con-
ditions (Table 2, entries 9-14). In several cases, deactivated
4-chloroanisole, 3,5-dimethoxychlorobenzene, and 2-chlor-
otoluene needed to be heated at 160 °C in order to achieve
higher yields than when working at 120 °C (Table 2, entries
15-23). In the vinylation of 4-chloroanisole with potassium
vinyltrifluoroborate, the use of Pd(OAc)2 provided lower
yield than when using complex 1 (Table 2, compare entries 15
and 16). When potassium styryl- or dec-1-enyltrifluorobo-
rates were used as nucleophilic partners, less than 8% of the
regioisomeric products 3 was also obtained (Table 2, entries
5, 6, 13, 14, 17, and 18). In the cross-coupling of 4-chlor-
oanisole and 2-chlorotoluene with vinyltrifluoroborate,
less than 6% of the Heck products, 4,40-dimethoxy- and
4,40-dimethylstilbene, respectively, was obtained (Table 2,
entries 15 and 22).
On the other hand, this coupling failed in the presence of
phosphanes such as XantPhos, Ruphos, and dppf (Table 1,
entries 9-11), with dppp affording slightly lower yield than
Binap (Table 1, entry 12), whereas Pd(OAc)2 and PdCl2 gave
96 and 85% yields, respectively (Table 1, entries 13 and 14).
When the Pd loading using palladacycle 1 was decreased to
1 mol % and (S)-Binap or dppp to 2 mol %, yields of 80 and
66% for product 2aa, respectively, were obtained, corrobor-
ating that Binap is a better bidentate ligand than dppp
(Table 1, entries 15 and 16). In the case of Pd(OAc)2 or
PdCl2 (1 mol %) and (S)-Binap (2 mol %) as ligand, product
2aa was obtained in much lower 57 and 29% yields, respec-
tively (Table 1, entries 17 and 18). Potassium (E)-styryltri-
fluoroborate was cross-coupled with 4-chloroacetophenone
using palladacycle 1, Pd(OAc)2, or PdCl2 with a 3 mol % Pd
loading, affording steroselectively (E)-4-acetylstilbene (2ab)
in high yields (>91%) (Table 1, entries 19-21). However, a
much lower yield was obtained when the Pd loading was
1 mol % using Pd(OAc)2 than complex 1 (Table 1, compare
entries 22 and 23).
Different activated and deactivated aryl chlorides and
heterocyclic chlorides were cross-coupled with potassium
vinyl and alkenyltrifluoroborates using these optimized re-
action conditions: palladacycle 1 or Pd(OAc)2 and (S)-Binap
(1:2) as a catalytic mixture and Cs2CO3 as base under
Ar, DMF as solvent and conventional heating at 120 °C
Heteroaryl chlorides were also used as coupling partners
with the corresponding potassium alkenyltrifluoroborates.
8194 J. Org. Chem. Vol. 74, No. 21, 2009

ꢀ
Alacid and Najera
JOCArticle
Thus, 3-chloropyridine was alkenylated with potassium
vinyl, (E)-styryl, and (E)-dec-1-enyltrifluoroborates to pro-
vide products 2ha, 2hb, and 2hc, respectively, in moderate
yields (Table 2, entries 24-26). 4-Chloro-2-methylquinoline
gave good yields of the corresponding vinyl and styryl
derivatives 2ia and 2ib (Table 2, entries 27 and 28). Under
the same reaction conditions, 5-chlorofurfural was cross-
coupled with potassium vinyl- and (E)-styryltrifluoroborate
giving products 2ja and 2jb in good yields (Table 2, entries 29
and 30).
128.6, 126.4, 116.8, 26.7; MS m/z 146 (Mþ, 42), 131 (100),
103 (64).
General Procedure for the Cross-Coupling of Potassium Styr-
yltrifluoroborate with with Organic Chlorides [4-Acetylstilbene
(2ab) as Example]. A glass tube was charged with palladium
catalyst (3 mol % of Pd), (S)-Binap (9.3 mg, 6 mol %),
potassium (E)-styryltrifluoroborate (60 mg, 0.3 mmol), and
Cs2CO3 (249 mg, 0.75 mmol) and sealed with a septum. The
mixture was purged by alternating five cycles of evacuation and
inert gas introduction, and then, N,N-dimethylformamide not
dry (1 mL) and 4-chloroacetophenone (0.032 mL, 0.25 mmol)
were added, heating the mixture at 120 °C (bath temperature).
When the reaction was stopped and cooled at room tempera-
ture, the mixture was diluted with 10 mL of water and the
product was extracted in diethyl ether (2 ꢀ 15 mL). The
combined organic layers were washed with water (4 ꢀ 15 mL)
and dried over anhydrous MgSO4. The solvent was removed
under vacuum, and the product was purified by flash chroma-
tography in hexane/ethyl acetate 95:5 to afford 47 mg of
4-acetylstilbene (85% yield).
Conclusions
It can be concluded that the oxime-derived palladacycle 1
or Pd(OAc)2 can be very efficient precatalysts for the cross-
coupling reaction of potassium vinyl and alkenyltrifluoro-
borates with a wide range of aryl and heteroaryl chlorides
when Binap is added as a ligand. These types of cross-
coupling must be performed in the presence of Cs2CO3 as
base and in DMF as solvent at temperatures of 120 or 160 °C
and with less than 3 mol % Pd loading.
(E)-4-Acetylstilbene (2ab): Colorless solid; Rf 0.20 (hexane/
ethyl acetate 9:1); mp 139-141 °C; IR (KBr) ν 3010, 2945, 2895,
1707, 1603, 1518, 1366, 1355, 1261, 1184 cm-1 1H NMR
;
(CDCl3, 300 MHz) δ 7.95 (d, 2H, J = 8.5 Hz), 7.58 (d, 2H,
J = 8.3 Hz), 7.56-7.53 (m, 2H), 7.41-7.38 (m, 2H), 7.33-7.30
(m, 1H), 7.23 (d, 2H, J = 16.3 Hz), 7.12 (d, 2H, J = 16.3 Hz),
2.60 (s, 3H); 13C NMR (CDCl3, 75 MHz) δ 197.6, 142.1, 136.8,
136.1, 131.6, 129.0, 128.9, 128.4, 127.6, 126.9, 126.6, 26.7; MS m/
z 223 (Mþ þ 1, 11), 222 (Mþ, 65), 208 (17), 207 (100), 179 (22),
178 (66), 177 (10), 176 (13).
Most of the compounds are all known, and some of them are
commercially available (a list of which can be found in the
Supporting Information).
Experimental Section
General Procedure for the Cross-Coupling of Potassium Alke-
nyltrifluoroborates with Organic Chlorides [4-Vinylacetophenone
(2aa) as Example]. A glass tube was charged with palladium
catalyst (2 mol % of Pd), (S)-Binap (6.2 mg, 4 mol %),
potassium vinyltrifluoroborate (40 mg, 0.3 mmol), and Cs2CO3
(249 mg, 0.75 mmol) and sealed with a septum. The mixture was
purged by alternating five cycles of evacuation and inert gas
introduction, and then, not dry N,N-dimethylformamide (1 mL)
and 4-chloroacetophenone (0.032 mL, 0.25 mmol) were added
and the mixture heated at 120 °C (bath temperature). When the
reaction was stopped and cooled at room temperature, the
mixture was diluted with 10 mL of water and the product was
extracted in diethyl ether (2 ꢀ 15 mL). The combined organic
layers were washed with water (4 ꢀ 15 mL) and dried over
anhydrous MgSO4. The solvent was removed under slight
vacuum, and the product was purified by flash chromatography
in pentane/diethyl ether 95:5 obtaining 30 mg of 4-vinylaceto-
phenone (82% yield).
Acknowledgment. Dedicated to Professor Benito Alcaide
on occasion of his 60th birthday. This work was financially
ꢀ
supported by the Ministerio de Educacion y Ciencia (MEC)
of Spain (Grants CTQ2004-00808/BQU, CTQ2007-62771/
BQU, and Consolider INGENIO 2010, CSD200700006), the
Generalitat Valenciana (PROMETEO/2009/039), and the
University of Alicante. E.A. thanks the MEC for a predoc-
toral fellowship. We thank Medalchemy S. L. for a generous
gift of (S)-Binap.
40-Vinylacetophenone (2aa): Oil; Rf 0.45 (hexane/ethyl acetate
10:1); IR (film) ν 3029, 2926, 1683, 1611, 1265 cm-1
;
1H NMR (CDCl3, 300 MHz) δ 7.93 (d, 2H, J = 8.4 Hz), 7.49
(d, 2H, J = 8.2 Hz), 6.76 (dd, 1H, J = 17.6 and 10.9 Hz),
5.90 (d, 1H, J = 17.6 Hz), 5.41 (d, 1H, J = 10.9 Hz), 2.59 (s, 3H);
13C NMR (CDCl3, 75 MHz) δ 197.7, 142.2, 136.4, 136.0, 128.8,
Supporting Information Available: Physical and spectral
data, as well as the 1H NMR and 13C NMR spectra of known
compounds are included. This material is available free of
charge via the Internet at http://pubs.acs.org.
J. Org. Chem. Vol. 74, No. 21, 2009 8195