Palladium-catalyzed cross-coupling reaction of allyl acetates with pinacol aryl- and vinylboronates

Article abstract of DOI:10.1016/S0040-4039(03)00980-8

Pinacol boronates 2 couple efficiently with allyl acetates 1 in the presence of a palladium catalyst prepared in situ from PdCl₂ and TFP to give the coupled products 3 in moderate to good yields under mild conditions.

Full text of DOI:10.1016/S0040-4039(03)00980-8

TETRAHEDRON
LETTERS
Pergamon
Tetrahedron Letters 44 (2003) 4311–4314
Palladium-catalyzed cross-coupling reaction of allyl acetates with
pinacol aryl- and vinylboronates
Giorgio Ortar*
Dipartimento di Studi Farmaceutici e Istituto di Chimica Biomolecolare del C.N.R., Sezione di Roma, Universit a` ‘La Sapienza’,
00185 Roma, Italy
Received 1 April 2003; accepted 16 April 2003
Abstract—Pinacol boronates 2 couple efficiently with allyl acetates 1 in the presence of a palladium catalyst prepared in situ from
PdCl and TFP to give the coupled products 3 in moderate to good yields under mild conditions. © 2003 Elsevier Science Ltd.
2
All rights reserved.
Aryl- and vinylboronic acid pinacol esters, which are
most conveniently prepared by direct borylation of aryl
1
and vinyl halides or triflates, represent an useful alter-
native to the corresponding boronic acids in the
2
Suzuki–Miyaura cross-coupling reaction. Their use
may be particularly advantageous when the isolation of
free boronic acids requires additional protection-depro-
tection steps or in the presence of functionalities incom-
patible with the traditional route to boronic acids from
Grignard or lithium reagents and trialkyl borates.
Compared to the impressive development of the
Suzuki–Miyaura coupling, only scanty attention has
been paid in the past to the use of organoboron3
reagents in palladium-catalyzed allylic substitutions
and, to the best of my knowledge, there are so far no
reports on the utilization of pinacol boronates in such
Scheme 1.
model substrates. The results are summarized in Table
1
.
a
Table 1. Reaction of 1a with 2a under various conditions
4
Solvent/T (°C) Yield (%)b
Entry
Catalyst
Base
reactions. Recently, Balme et al. have developed a
novel catalytic system [PdCl (TFP) ] working quite
2
2
1
2
3
4
5
6
7
8
9
Pd(PPh3)4
Pd(PPh3)4
K PO
THF/60
THF/60
THF/60
THF/60
DMF/60
THF/60
DMF/60
MeOH/rt
MeOH/rt
MeOH/rt
MeOH/rt
46
43
54
9
69
13
15
82
3
4
effectively in cross-coupling reactions of allyl acetates
with a variety of arylboronic acids in conjunction with
Cs CO
2
3
Pd(PPh3)4
CsF
CsF
CsF
–
–
KF
–
5
a fluoride source. Encouraged by this result, I have
Pd dba
2
3
examined the effectiveness of pinacol boronates in pal-
ladium-catalyzed allylation reactions and I report
herein that pinacol aryl- and vinylboronates (2) are
indeed good substrates for the coupling reaction with
allyl acetates (1) (Scheme 1).
Pd(PPh3)4
Pd(PPh3)4
Pd(PPh3)4
c
c
PdCl /2TFP
2
PdCl
/2TFP
Traces
45
Traces
2
10
1
PdCl /2PPh
KF
KF
2
3
d
1
PdCl /dppf
Some reaction conditions were briefly explored, using
2
cinnamyl acetate (1a) and 1-naphthylboronate (2a) as
a
All reactions were carried out with 1 mol% of the catalyst, 1.3 equiv.
of 2a and 1.3 equiv. of CsF or 2.6 equiv. of K PO , Cs CO and KF
for 4 h (entries 1–7) or 24 h (entries 8–11).
Isolated yields.
TFP refers to tri-2-furylphosphine.
dppf refers to 1,1%-bis(diphenylphosphino)ferrocene.
3
4
2
3
Keywords: allylation; boron and compounds; coupling reactions; Pd
catalyst.
b
c
*
Tel.: +39649913612; fax: +396491491; e-mail: giorgio.ortar@
uniroma1.it
d
0
040-4039/03/$ - see front matter © 2003 Elsevier Science Ltd. All rights reserved.
doi:10.1016/S0040-4039(03)00980-8

4
312
G. Ortar / Tetrahedron Letters 44 (2003) 4311–4314
a
Table 2. Palladium-catalyzed cross-coupling of allyl acetates 1 with pinacol boronates 2

G. Ortar / Tetrahedron Letters 44 (2003) 4311–4314
4313
The use of a fluoride salt, as already adopted by Balme,
to promote transmetalation ensuring essentially non
basic conditions and thus avoiding some typical prob-
lems encountered in Suzuki–Miyaura couplings, was
found superior to that of other inorganic bases. The
best yields of 3a were obtained under the optimized
conditions developed by Balme for arylboronic acids
8001–8006; (d) Firooznia, F.; Gude, C.; Chan, K.; Mar-
copulos, N.; Satoh, Y. Tetrahedron Lett. 1999, 40, 213–216
and references cited therein; (e) Giroux, A.; Han, Y.;
Prasit, P. Tetrahedron Lett. 1997, 38, 3841–3844; (f)
Ishiyama, T.; Itoh, Y.; Kitano, T.; Miyaura, N. Tetra-
hedron Lett. 1997, 38, 3447–3450.
6
3. (a) Cort e´ s, J.; Moreno-Ma n˜ as, M.; Pleixats, R. Eur. J.
Org. Chem. 2000, 239–243; (b) Uozumi, Y.; Danjo, H.;
Hayashi, T. J. Org. Chem. 1999, 64, 3384–3388; (c)
Moreno-Ma n˜ as, M.; Pajuelo, F.; Pleixats, R. J. Org.
Chem. 1995, 60, 2396–2397; (d) Miyaura, N.; Yamada, K.;
Suginame, H.; Suzuki, A. J. Am. Chem. Soc. 1985, 107,
972–980; (e) Legros, J.-Y.; Fiaud, J.-C. Tetrahedron Lett.
1990, 31, 7453–7456.
(
entry 8).
The protocol was successfully extended to a variety of
allyl acetates and of pinacol aryl- and vinylboronates
(
Table 2). In a typical procedure (entry 1), a stirred
solution of cinnamyl acetate (1a, 176 mg, 1 mmol),
PdCl (1.8 mg, 0.01 mmol), TFP (4.6 mg, 0.02 mmol) in
2
MeOH (3 mL) was flushed with N for 10 min at room
4. A nickel-catalyzed coupling of a 1,3-disubstituted allyl
carbonate with a borate prepared in situ from pinacol
phenylboronate and MeLi has been described: Kobayashi,
Y.; Mizojiri, R.; Ikeda, E. J. Org. Chem. 1996, 61, 5391–
5399.
2
temperature. Then, KF (151 mg, 2.6 mmol) and a
solution of 1-naphthylboronate (2a, 330 mg, 1.3 mmol)
in MeOH (2 mL) were added and the mixture was
stirred 24 h at room temperature under N . The reac-
2
tion mixture was then diluted with brine and extracted
with ether. The organic phase was washed with brine,
dried (Na SO ), and evaporated. Chromatography of
5. Bouyssi, D.; Gerusz, V.; Balme, G. Eur. J. Org. Chem.
2002, 2445–2448.
6. It is generally assumed that organoboron reagents add to
2
4
3
b,d
the residue (289 mg) on silica gel (9 g) using hexane as
p-allylpalladium complexes via attack at the metal.
See
eluent afforded 199 mg (82%) of (E)-3-(1-naphthyl)-1-
also: Chung, K.-G.; Uemura, M.; Uemura, S. J. Chem.
7
phenyl-1-propene (3a).
Soc., Perkin Trans. 1 2000, 15–18.
7
. Characterization data of coupling products 3. 3a: mp
9
The coupling reactions proceeded generally within 24 h
at room temperature and were compatible with both
electron-withdrawing and -donating groups. Sterically
hindered substrates (2b,h) were also tolerated. Products
74–75°C (lit. mp 74–75°C); IR 3077, 3009, 1597, 1497,
−
1
1
1448, 1396, 1214, 966 cm ; H NMR l 3.98 (2H, d,
13
J=4.8 Hz), 6.41–6.53 (2H, m), 7.15–8.04 (12H, m);
C
NMR l 36.35, 123.78, 125.34, 125.41, 125.70, 125.87,
126.15, 126.85, 128.23, 128.47, 128.63, 131.08, 131.80,
133.65, 135.99, 137.22. 3b: oil; IR 3064, 2927, 1600, 1494,
3
arose from exclusive attack at the less substituted allyl
terminus. No evidence was found in entries 9–12 that
the reaction products had suffered some isomerization
of the allylic double bond into conjugation with the
aromatic moiety. In the case of geranyl (1d) and neryl
−
1
1
1448, 967 cm ; H NMR l 2.31 (3H, s), 3.50 (2H, d,
13
J=4.8 Hz), 6.26–6.39 (2H, m), 7.12–7.33 (9H, m);
C
NMR l 19.37, 36.77, 125.81, 126.15, 126.77, 128.21,
128.27, 128.95, 129.95, 130.63, 136.11, 137.25, 137.94. 3c:
mp 36–37°C; IR 3022, 2949, 1715, 1607, 1438, 1413, 1281,
(
1e) acetates, a limited erosion of the stereochemical
integrity of the double bond occurred (entries 11, 12).
This result, which has precedents in the palladium-cata-
lyzed cross-coupling reactions of allyl substrates with
8
−
1 1
1113, 964 cm ; H NMR l 3.55 (2H, d, J=6.6 Hz), 3.87
(3H, s), 6.28 (1H, td, J=15.6, 6.6 Hz), 6.42 (1H, d,
J=15.6 Hz), 7.15–7.33 (7H, m), 7.95 (2H, d, J=8.4 Hz);
3e
tetraphenylborate anion and organotin nucleophiles,
13
seems to indicate that the transmetalation step of the
p-allylpalladium intermediates with the boronate pro-
ceeds with a rate comparable to that of the syn/anti-iso-
merization reaction.
C NMR l 39.17, 51.86, 125.92, 127.07, 127.76, 127.97,
128.30, 128.43, 129.59, 131.57, 136.93, 145.33, 166.71. 3d:
mp 130–131°C; IR 3288, 3026, 1656, 1598, 1496, 1409,
−
1 1
1369, 1316, 1266, 1022, 966 cm ; H NMR l 2.10 (3H, s),
3
6
7
.46 (2H, d, J=6.3 Hz), 6.28 (1H, td, J=15.9, 6.3 Hz),
.40 (1H, d, J=15.9 Hz), 7.13 (2H, d, J=8.5 Hz), 7.16–
13
.34 (5H, m), 7.42 (2H, d, J=8.5 Hz), 8.02 (1H, br s);
C
References
NMR l 24.29, 38.60, 120.15, 125.86, 126.86, 128.25,
1
28.82, 128.90, 130.75, 135.82, 135.95, 137.15, 168.50. 3e:
3c
1
. (a) Ishiyama, T.; Ishida, K.; Miyaura, N. Tetrahedron
mp 33–34°C (lit. oil); IR 2929, 2833, 1607, 1510, 1298,
−
1
1
2
001, 57, 9813–9816; (b) Murata, M.; Oyama, T.; Watan-
1243, 1178, 1032, 965 cm ; H NMR l 3.46 (2H, d,
J=6.3 Hz), 3.75 (3H, s), 6.29 (1H, td, J=15.9, 6.3 Hz),
6.39 (1H, d, J=15.9 Hz), 6.82 (2H, d, J=8.7 Hz), 7.09–
7.33 (7H, m); C NMR l 38.37, 55.13, 113.70, 125.86,
126.79, 128.24, 129.35, 129.42, 130.49, 131.91, 137.28,
157.79. 3f: oil; IR 3438, 3010, 2982, 1742, 1709, 1498,
1367, 1166, 966 cm ; H NMR l 1.41 (9H, s), 3.02 (1H,
dd, J=14.0, 6.1 Hz), 3.09 (1H, dd, J=14.0, 5.7 Hz), 3.51
(2H, d, J=6.6 Hz), 3.71 (3H, s), 4.57 (1H, m), 4.99 (1H, d,
J=8.1 Hz), 6.32 (1H, td, J=15.6, 6.6 Hz), 6.43 (1H, d,
J=15.6 Hz), 7.05 (2H, d, J=7.8 Hz), 7.16 (2H, d, J=7.8
abe, S.; Masuda, Y. J. Org. Chem. 2000, 65, 164–168; (c)
Murata, M.; Oyama, T.; Watanabe, S.; Masuda, Y. Syn-
thesis 2000, 778–780; (d) Takahashi, K.; Takagi, J.;
Ishiyama, T.; Miyaura, N. Chem. Lett. 2000, 126–127; (e)
Murata, M.; Watanabe, S.; Masuda, Y. J. Org. Chem.
997, 62, 6458–6459; (f) Ishiyama, T.; Murata, M.;
Miyaura, N. J. Org. Chem. 1995, 60, 7508–7510.
. (a) Gravett, E. C.; Hilton, P. J.; Jones, K.; P e´ ron, J.-M.
Synlett 2003, 253–255; (b) Kotha, S.; Lahiri, K.;
Kashinath, D. Tetrahedron 2002, 58, 9633–9695 and refer-
ences cited therein; (c) Takagi, J.; Takahashi, K.;
Ishiyama, T.; Miyaura, N. J. Am. Chem. Soc. 2002, 124,
13
−
1 1
1
2
13
Hz), 7.19–7.37 (5H, m); C NMR l 28.25, 37.87, 38.88,
52.08, 54.35, 79.76, 125.89, 126.89, 128.26, 128.60, 128.84,

4
314
G. Ortar / Tetrahedron Letters 44 (2003) 4311–4314
1
3
1
29.19, 130.90, 133.56, 137.18, 138.66, 154.81, 172.05. 3g:
J=8.4 Hz), 8.09 (1H, br s); C NMR l 24.29, 39.52,
115.53, 120.12, 128.74, 135.76, 135.86, 137.13, 168.56. 3j:
mp 123–125°C; IR 3436, 3009, 2933, 2859, 1686, 1594,
−
1 1
oil; IR 2918, 2836, 1600, 1493, 1452, 1435, 967 cm ; H
NMR l 1.70–2.33 (6H, m), 2.70–2.80 (1H, m), 2.88 (2H,
d, J=6.9 Hz), 5.58 (1H, m), 6.23 (1H, td, J=15.6, 6.9
Hz), 6.41 6.41 (1H, d, J=15.6 Hz), 7.15–7.37 (10H, m);
−
1
1
1515, 1411, 1367, 1311, 1246, 1143 cm ; H NMR l
1.45–2.08 (6H, m), 2.12 (3H, s), 3.35 (1H, m), 5.66 (1H,
dd, J=10.0, 2.0 Hz), 5.87 (1H, m), 7.13 (2H, d, J=8.7
1
3
C NMR l 29.63, 30.51, 34.06, 40.58, 41.57, 122.09,
26.22, 126.30, 127.13, 127.21, 128.59, 128.73, 128.86,
31.36, 136.67, 137.90, 147.35. 3h: mp 106–109°C; IR
1
3
1
1
Hz), 7.41 (2H, d, J=8.7 Hz); C NMR l 21.02, 24.81,
24.94, 32.50, 41.18, 120.09, 127.89, 128.15, 129.83, 135.65,
142.48, 168.49. 3k: oil; IR 3048, 2969, 2916, 1597, 1509,
−
1
3
033, 2939, 2848, 1730, 1451, 1372, 1250, 1031, 962 cm ;
1
−1 1
H NMR l 0.83 (3H, s), 0.97–2.10 (15H, m), 1.06 (3H, s),
1449, 1396, 1377, 1214, 1108 cm ; H NMR l 1.58 (3H,
s, E-isomer), 1.62 (3H, s, Z-isomer), 1.65 (3H, s, E-iso-
mer), 1.69 (3H, s, Z-isomer), 1.75 (3H, s, Z-isomer), 1.78
(3H, s, E-isomer), 2.04–2.26 (4H, m), 3.77 (2H, d, J=6.6
Hz), 5.08 (1H, m, E-isomer), 5.17 (1H, m, Z-isomer),
5.39 (1H, t, J=6.9 Hz), 7.29–8.01 (7H, m).
8. Casta n˜ o, A. M.; Echavarren, M. Tetrahedron Lett. 1996,
37, 6587–6590.
2
.03 (3H, s), 2.33 (2H, d, J=7.2 Hz), 2.89 (2H, d, J=5.7
Hz), 4.61 (1H, m), 5.38 (2H, m), 6.26 (1H, td, J=15.9,
13
6
.9 Hz), 6.42 (1H, d, J=15.9 Hz), 7.16–7.37 (5H, m);
C
NMR l 15.74, 19.21, 20.71, 21.37, 27.74, 30.46, 31.13,
3
7
1
1.55, 34.53, 36.79, 36.90, 38.11, 46.43, 50.57, 57.05,
3.80, 122.27, 123.01, 125.78, 126.67, 128.24, 130.67,
37.54, 139.71, 143.52, 153.75, 170.17. 3i: mp 85–88°C
10
(lit. mp 89–92°C); IR 3290, 1663, 1601, 1556, 1511,
9. Ross, D. R.; Waight, E. S. J. Chem. Soc. 1965, 6710–
6717.
−
1 1
1
407, 1370, 1321, 1264, 993, 916 cm ; H NMR l 2.12
(
5
3H, s), 3.32 (2H, d, J=6.6 Hz), 5.02–5.08 (2H, m),
.85–5.99 (1H, m), 7.09 (2H, d, J=8.4 Hz), 7.42 (2H, d,
10. Yokoyama, Y.; Ito, S.; Takahashi, Y.; Murakami, Y.
Tetrahedron Lett. 1985, 26, 6457–6460.