Rhodium-catalyzed coupling of sodium tetraphenylborate with acid anhydrides in the presence or absence of norbornene

Article abstract of DOI:10.1016/S0022-328X(01)01439-5

Treatment of sodium tetraphenylborate with aliphatic or aromatic acid anhydrides in the presence of a rhodium catalyst gives the corresponding alkyl (or aryl) phenyl ketones in good yields. In the presence of norbornene, tandem three-component coupling products, 2-acyl-3-phenylnorbornanes are obtained.

Full text of DOI:10.1016/S0022-328X(01)01439-5

Journal of Organometallic Chemistry 648 (2002) 297–301
www.elsevier.com/locate/jorganchem
Rhodium-catalyzed coupling of sodium tetraphenylborate with
acid anhydrides in the presence or absence of norbornene
Kazuaki Oguma, Masahiro Miura *, Tetsuya Satoh, Masakatsu Nomura
Department of Applied Chemistry, Faculty of Engineering, Osaka Uni6ersity, Suita, Osaka 565-0871, Japan
Received 29 October 2001; accepted 9 November 2001
Abstract
Treatment of sodium tetraphenylborate with aliphatic or aromatic acid anhydrides in the presence of a rhodium catalyst gives
the corresponding alkyl (or aryl) phenyl ketones in good yields. In the presence of norbornene, tandem three-component coupling
products, 2-acyl-3-phenylnorbornanes are obtained. © 2002 Published by Elsevier Science B.V.
Keywords: Rhodium catalyst; Organoboron compounds; Acid anhydrides; Cross-coupling
pling system via rhodium catalysis to produce certain
aromatic ketones could be developed by adding acid
anhydride to the reaction in Scheme 1. Consequently,
we first examined the direct coupling of arylboron
compounds with acid anhydrides in order to obtain
appropriate conditions for the ketone synthesis, and
then, the reaction in the presence of norbornene was
investigated. It has been found that (a) the former
reaction using sodium tetraphenylborate efficiently pro-
ceeds to afford the corresponding phenyl ketones
(Scheme 3), and (b) the latter gives 2-acyl-3-phenylnor-
bornanes as the principal products along with the ke-
tones (Scheme 4). These results are reported herein.
1
. Introduction
Organoboron compounds are versatile reagents in
the palladium-catalyzed coupling reaction with organic
halides that is the well-known Suzuki–Miyaura reac-
tion [1]. Recently, arylboron compounds including aryl-
boronic acids and tetraaryl borates also have proved to
be effective arylating reagents in rhodium catalysis. For
example, polar alkenes such as enones [2], alkenylphos-
phonates [3] and nitroalkenes [4] undergo conjugate
arylation. Mizoroki–Heck type coupling or hydroaryla-
tion occurs with styrenes or related alkenes [5]. The
latter reaction proceeds with alkynes [6]. Aldehydes [7]
and imines [8] are nucleophilically arylated.
We reported that arylboronic acids undergo a unique
‘merry-go-round’ type multiple alkylation up to four
times upon treatment with norbornene (Scheme 1) [9].
The reaction involves mono- to tetraalkyl-substituted
arylrhodium(I) species as the principal intermediates
whose protonolysis leads to the products. On the other
hand, we also found that alkenes react with acid anhy-
drides in the presence of a rhodium catalyst under
hydrogen to give hydroacylated products (Scheme 2)
Scheme 1.
[10]. The reaction proceeds via oxidative addition of the
anhydrides to intermediary alkylrhodium(I) species.
Thus, we considered that a new three-component cou-
*
Corresponding author. Fax: +81-6-68797362.
E-mail address: miura@ap.chem.eng.osaka-u.ac.jp (M. Miura).
Scheme 2.
0022-328X/02/$ - see front matter © 2002 Published by Elsevier Science B.V.
PII: S0022-328X(01)01439-5

298
K. Oguma et al. / Journal of Organometallic Chemistry 648 (2002) 297–301
2. Results and discussion
and dppp further improved the reaction efficiency (en-
tries 3 and 4). Thus, 3a was obtained in 133% yield
using dppp, suggesting that more than one phenyl
group in 1 could be utilized. Dioxane and DMF as
solvents were not effective (entries 5 and 6).
2
.1. Reaction of sodium tetraphenylborate (1) with
acetic anhydride (2a)
We first examined the reaction using phenylboronic
acid, potassium phenyl(trifluoro)borate [11] and sodium
tetraphenylborate (1) as phenylating reagents in the
presence of acetic anhydride (2a). The former two
species could not couple with 2a, although during the
performance of this work, related palladium-catalyzed
coupling reactions of arylboronic acids with acid anhy-
drides [12,13], aryl trifluoroacetates [14] and benzoic
acid thioesters [15] were reported. However, the borate
2.2. Reaction of 1 with 6arious acid anhydrides 2
Shown in Table 2 are the results for the reaction of 1
(1 mmol) with anhydrides 2b–f (2 mmol) using dppp as
ligand in toluene. The reactions of 1 with linear
aliphatic anhydrides 2b and 2c proceeded as well as that
with 2a to give ketones 3b and 3c in good yields.
Isobutyric anhydride (2d) could also be used. Benzoic
anhydrides 2e and 2f efficiently reacted to afford ben-
zophenones 3e and 3f. Interestingly, using crotonic
anhydride (2g) gave a mixture of (E)-1-phenyl-2-buten-
1-one (3g) and 1,3-diphenylbutan-1-one (3g%). The for-
mation of the diphenylated compound 3g% implies that
conjugate phenylation can also occur under the present
conditions. By prolonging reaction time, 3g% could be
obtained as the major product.
1
was found to react with 2a efficiently to give ace-
tophenone (3a).
Table 1 summarizes the results under different condi-
tions. When 1 (1 mmol) was treated with 2a (3 mmol)
in the presence of [RhCl(cod)] (0.01 mmol) and PPh3
2
(
0.04 mmol) in toluene at 100 °C for 2 h, the ketone 3a
was produced in 51% yield (entry 1). Using a bulky
phosphine P(t-Bu) in place of PPh gave a somewhat
3
3
better yield (entry 2). Bidentate ligands such as dppf
2.3. Reaction of 1 with acid anhydrides 2 in the
presence of norbornene (4)
When 1 (1 mmol) was treated together with 2a (3
mmol) and 4 (1 mmol) in the presence of [RhCl(cod)]2
and dppp in toluene at 100 °C for 2 h, exo-2-acetyl-
exo-3-phenylbicyclo[2.2.1]heptane (5a) was produced in
Scheme 3.
4
7% yield as the three-component coupling product
together with ketone 3a (62%) (Scheme 4 and entry 1 in
Table 3). Using 2a (1 mmol) and 4 (3 mmol) selectively
gave 5a, but the yield was considerably low (entry 2). In
this case, the formation of di-, tri- and tetranorbornyl-
benzenes was also observed (see Scheme 1). However,
other possible compounds such as 1:1:2 coupling
product of 1, 2a and 4 and further alkylated ketones
were not detected. Increasing both the amounts of 2a
and 4 afforded more than 60% yield of 5a (entries 3 and
Scheme 4.
Table 1
a
Reaction of sodium tetraphenylborate (1) with acetic anhydride (2a)
5
).
As expected, the reactions of 1 with 2b, 2e and 2f
gave the corresponding exo-2-acyl-exo-3-phenylbicy-
clo[2.2.1]heptane 5b, 5e and 5f, respectively (entries
6
–8). Note that 5f was obtained with a high yield of
b
Entry
Ligand
Solvent
Yield of 3a (%)
126%, although the reaction was relatively slow.
1
2
3
4
5
6
PPh3
P(t-Bu)3
dppf
dppp
dppp
dppp
Toluene
Toluene
Toluene
Toluene
Dioxane
DMF
51
79
91
133
63
0
2
.4. Reaction scheme
A plausible mechanism for the formation of ketones
3 and 5 is illustrated in Scheme 5. The first step may
involve the generation of phenylrhodium(I) species A
by transmetalation [16]. Then, oxidative addition of 2
to give acylphenylrhodium(III) intermediate B followed
by reductive elimination affords 3. In the presence of 4,
insertion of it into the phenylꢀrhodium bond of A in an
a
The reaction was carried out at 100 °C for 2 h under N using 1
2
(1 mmol), 2a (3 mmol), [RhCl(cod)2]2 (0.01 mmol) and ligand (0.04
mmol for monodentate ligand or 0.02 mmol for bidentate ligand).
b
Determined by GC analysis [(mmol of 3a/mmol of 1)×100].

K. Oguma et al. / Journal of Organometallic Chemistry 648 (2002) 297–301
299
Table 3
exo-fashion to produce alkylrhodium intermediate C.
Then, oxidative addition of 2 to give acylalkylrhodiu-
m(III) intermediate D occurs and the subsequent reduc-
Reaction of sodium tetraphenylborate 1 with acid anhydride 2a, 2b,
a
2
e, and 2f in the presence of norbornene (4)
tive elimination affords
5 [17,18]. As proposed
previously [9], intramolecular rhodation via CꢀH cleav-
age in C to give rhodacycle E and the successive
reductive
elimination
affords
2-(2-norbornyl)-
phenylrhodium species F. Subsequently, the insertion–
cyclorhodation–reductive elimination process occurs
up to three times, resulting in the formation of multiply
alkylated benzenes (Scheme 1).
The formation of 5 along with 3 in the presence of 4
implies that the transformation of A to C competes
with that to B. The lack of 1:1:2 coupling product of 1,
2
and 4 and further alkylated ketones even using an
excess amount of 4 (e.g. entry 4 in Table 3) suggests
that the oxidative addition giving D is more favorable
than the formation of F via E. The observed high
selectivity of 5f could be attributed to the fact that the
oxidative addition of 2f to A is relatively slow due to
the presence of the electron-donating methoxy sub-
stituent. Even in this case, no trace of products derived
Table 2
Reaction of sodium tetraphenylborate 1 with various acid anhydride
a
2
a
The reaction was caried out at 100 °C for 2 h under N using 1 (1
2
mmol), 2a (2 mmol), [RhCl(cod)]2 (0.01 mmol) and dppp (0.02
mmol).
b
Determined by GC analysis [(mmol of product/mmol of 1)×100].
Value in parenthesis is yield after chromatographic purification.
c
Di-, tri-, and tetranorbornylbenzenes were also produced in 33, 19
and 17% yields, respectively.
d
Reaction for 24 h.
from F or more alkylated species was observed. This
leads us to deduce that another factor inhibiting the
formation of them intervenes. However, the details are
not clear at the present stage.
3
. Experimental
3.1. General
1
13
H- and C-NMR spectra were recorded at 400 and
00 MHz, respectively, for CDCl solutions. MS analy-
1
3
sis was made by EI. GC analysis was carried out using
a silicone OV-17 glass column (i.d. 2.6 mm×1.5 m).
All the starting materials were commercially available
and used as received. The solvents employed were
a
The reaction was caried out at 100 °C under N using 1 (1 mmol),
a (2 mmol), [RhCl(cod)]2 (0.01 mmol) and dppp (0.02 mmol).
Determined by GC analysis [(mmol of 3/mmol of 1)×100].
2
2
b

300
K. Oguma et al. / Journal of Organometallic Chemistry 648 (2002) 297–301
purified by standard methods before use. The following
experimental procedure may be regarded as typical in
methodology and scale.
ses confirmed the formation of exo-2-acetyl-exo-3-
phenylbicyclo[2.2.1]heptane (5a) and acetophenone (3a)
in 60 and 68% yields, respectively. The product mixture
was fractionated by column chromatography on silica
3.2. Reaction of sodium tetraphenylborate (1) with
gel. Elution with hexane–Et O (99.2:0.8, v/v) gave com-
2
heptanoic anhydride (2c)
pound 5a (118 mg, 55%).
A mixture of 1 (342 mg, 1 mmol), 2c (484 mg, 2
3.4. Products
mmol), [RhCl(cod)] (4.9 mg, 0.01 mmol), dppp (8.3
2
mg, 0.02 mmol) and 1-methylnaphthalene (ca. 100 mg,
internal standard) in toluene (5 cm ) was stirred at 100
Compounds 3a, 3b, 3d–f were identified by compari-
son with the corresponding commercial samples. The
analytical data of other products are given below.
3
°
C under nitrogen for 24 h. After cooling, the reaction
1
mixture was extracted with Et O and dried over sodium
1-Phenylheptan-1-one (3c) [19]: oil; H-NMR l 0.89
2
sulfate. GC and GC–MS analyses confirmed the for-
mation of 1-phenylheptan-1-one (3c) in 133% yield. The
product (224 mg, 118%) was also isolated by column
chromatography on silica gel using hexane–diethyl
ether (99.8:0.2, v/v) as eluent.
(t, 3H, J=7.0 Hz), 1.27–1.42 (m, 6H), 1.70–1.77 (m,
2H), 2.96 (t, 2H, J=7.3 Hz), 7.45 (t, 2H, J=7.3 Hz),
7.55 (t, 1H, J=7.3 Hz), 7.96 (d, 2H, J=7.3 Hz);
13
C-NMR l 14.00, 22.49, 24.30, 29.01, 31.63, 38.59,
128.00, 128.50, 132.81, 137.08, 200.56; MS m/z 190
+
(
M ).
(E)-1-Phenyl-2-buten-1-one (3g) [20]: oil; H-NMR l
2.00 (dd, 3H, J=1.5, 6.6 Hz), 6.90 (qd, 1H, J=1.5,
5.4 Hz), 7.08 (qd, 1H, J=6.6, 15.4 Hz), 7.46 (t, 2H,
J=7.3 Hz), 7.55 (t, 1H, J=7.3 Hz), 7.93 (d, 2H,
1
3.3. Reaction of sodium tetraphenylborate (1) with
acetic anhydride (2a) in the presence of norbornene (4)
1
A mixture of 1 (342 mg, 1 mmol), 2a (306 mg, 3
1
3
mmol), 4 (282 mg, 3 mmol), [RhCl(cod)] (4.9 mg, 0.01
J=7.3 Hz); C-NMR l 18.58, 127.53, 128.48 (over-
lapped), 132.56, 137.90, 145.04, 190.78; MS m/z 146
2
mmol), dppp (8.3 mg, 0.02 mmol) and 1-methylnaph-
+
thalene (ca. 100 mg, internal standard) in toluene (5
(M ).
3
cm ) was stirred at 100 °C under nitrogen for 2 h. After
1,3-Diphenylbutan-1-one (3g%) [21]: m.p. 71–72 °C;
H-NMR l 1.34 (d, 3H, J=6.9 Hz), 3.18 (dd, 1H,
1
cooling, the reaction mixture was extracted with Et O
2
and dried over sodium sulfate. GC and GC–MS analy-
J=8.3, 16.7 Hz), 3.30 (dd, 1H, J=5.8, 16.3 Hz),
3
4
7
4
1
.42–3.55 (m, 1H), 7.17–7.21 (m, 1H), 7.25–7.32 (m,
H), 7.44 (t, 2H, J=7.3 Hz), 7.54 (t, 1H, J=7.3 Hz),
13
.93 (d, 2H, J=8.0 Hz); C-NMR l 21.85, 35.56,
7.02, 126.26, 126.85, 128.05, 128.51, 128.54, 132.95,
+
37.20, 146.56, 199.07: MS m/z 224 (M ).
exo-2-Acetyl-exo-3-phenylbicyclo[2.2.1]heptane (5a)
1
[
22]: oil; H-NMR l 1.19–1.27 (m, 1H), 1.36–1.43 (m,
2
H), 1.50 (s, 3H), 1.58–1.62 (m, 2H), 2.24 (d, 1H,
J=10.3 Hz), 2.36 (s, 1H), 2.55 (s, 1H), 3.00 (d, 1H,
J=10.3 Hz), 3.20 (d, 1H, J=10.3 Hz), 7.16–7.18 (m,
1
3
3
3
1
H), 7.22–7.26 (m, 2H); C-NMR l 28.43, 31.13,
1.24, 37.11, 38.42, 43.50, 52.63, 62.51, 126.40, 128.22,
28.33, 142.34, 209.82; MS m/z 214 (M ).
+
exo-2-Phenyl-3-propionylbicyclo[2.2.1]heptane (5b):
1
oil; H-NMR l 0.46 (t, 3H, J=7.0 Hz), 1.22–1.26 (m,
1
H), 1.35–1.43 (m, 2H), 1.58–1.65 (m, 2H), 1.75–1.96
(
m, 2H), 2.29–2.34 (m, 1H), 2.35 (s, 1H), 2.52 (s, 1H),
2
7
7
6
2
.99 (d, 1H, J=10.3 Hz), 3.17 (d, 1H, J=10.3 Hz),
13
.12–7.16 (m, 3H), 7.20–7.26 (m, 2H); C-NMR l
.00, 28.50, 31.21, 37.25, 37.41, 38.53, 43.38, 52.75,
1.31, 126.28, 128.23, 128.30, 142.46, 212.17; MS m/z
+
28 (M ). Anal. Found: C, 84.16; H, 8.84. Calc. for
C H O: C, 84.16; H, 8.83%.
16
20
exo-2-Benzoyl-exo-3-phenylbicyclo[2.2.1]heptane (5e)
1
[
17]: m.p. 87–88 °C; H-NMR l 1.40–1.52 (m, 3H),
1
.69–1.75 (m, 2H), 2.42–2.48 (m, 2H), 2.69 (s, 1H),
Scheme 5.
3.29 (d, 1H, J=10.3 Hz), 3.84 (d, 1H, J=10.3 Hz),

K. Oguma et al. / Journal of Organometallic Chemistry 648 (2002) 297–301
301
6
.88–6.96 (m, 5H), 7.21 (t, 2H, J=7.3 Hz), 7.34 (t, 1H,
References
13
J=7.3 Hz), 7.54 (t, 2H, J=7.3 Hz); C-NMR l 28.94,
3
1
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MS m/z 276 (M ).
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3
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