An improved Suzuki-Miyaura cross-coupling reaction for the synthesis of fluorine-substituted 3-biaryl-1-ferrocenyl-2-propen-1-one

Article abstract of DOI:10.1055/s-2005-921748

We studied the Pd(0)-catalyzed Suzuki-Miyaura cross-coupling reaction and obtained an improved procedure with shorter reaction times and higher conversions. We investigated two methods stepwise addition of reagents and addition of all the reagents at the

Full text of DOI:10.1055/s-2005-921748

PAPER
123
An Improved Suzuki–Miyaura Cross-Coupling Reaction for the Synthesis of
Fluorine-Substituted 3-Biaryl-1-ferrocenyl-2-propen-1-one
F
luorine-Substitute
i
d3-B
i
n
aryl-1-ferroc
g
enyl-2-prope
-
n-1-onebao Song,* Ru-xiang Lin, Ming-yu Teng, Jie Zhang, Chun-an Ma
The State Key Laboratory Breeding Base of Green Chemistry Synthesis Technology, College of Chemical Engineering and Materials
Science, Zhejiang University of Technology, Hangzhou 310014, P. R. of China
E-mail: songqb@yahoo.com
Received 18 April 2005; revised 5 July 2005
to the introduction of a fluorine atom or trifluoromethyl
Abstract: We studied the Pd(0)-catalyzed Suzuki–Miyaura cross-
group into organic molecules because these compounds
coupling reaction and obtained an improved procedure with shorter
exhibit particularly high physiological activities and re-
reaction times and higher conversions.
markable physical properties.10
We investigated two methods stepwise addition of reagents and ad-
dition of all the reagents at the same time. We found that the reac- Following our previous work,9 due to the unsatisfactory
tion rate of the former is faster than the latter. Methanol was shown
conversion (generally below 80%) and long reaction
to be the optimum solvent for the reaction, however with an alcohol
times (general nearly 20 hours), we have further examined
as the solvent the reaction was complete in under 1.5 hours. This im-
the role of solvents and the effect of changing the order of
proved methodology was applied to the synthesis of novel fluorine-
reagent addition to enhance the rate of the Suzuki cross-
substituted 3-biaryl-1-ferrocene-propene-1-ones, which were syn-
coupling reaction for the synthesis of novel fluorine-sub-
thesized in good yields.
stituted 3-biaryl-1-ferrocenyl-2-propen-1-one (Scheme
Keywords: Suzuki cross-coupling reaction, Pd(0) catalyst, alcohol
solvents, ferrocene derivatives, biaryl
1).
Firstly, we investigated the influence the order of addition
of reagents had on the reaction. The best results were ob-
tained when the reaction was carried out as follows: sol-
vent (one third of the total volume), an arylboronic acid,
and sodium carbonate (10% in water) were successively
added to the flask, and refluxed for five minutes; then
Pd(0) catalyst, a halide, and the remaining solvent was
added to the above mixture in sequence. The reaction rate
was improved by adding the reagents stepwise compared
with mixing all the reagents at once. For example, the re-
action time of 1-ferrocenyl-3-(4¢-bromo)phenyl-2-pro-
pen-1-one (4a) with 3,4,5-trifluorophenyl boronic acid
(5a) in methanol was shortened from eight hours to 30
minutes (Table 1, entries 12 and 27, Scheme 2). Recently,
Hassan, Smith, and Aliprantis11 reported that an arylbo-
ronic acid was transformed into trihydroxyarylboronate
In the past few years, more and more interest has focused
on the design of new compounds incorporating the fer-
rocene skeleton owing to their potential applications as
NLO chromophores,1 as liquid crystal materials,2 in elec-
trochemistry,3 in polymer chemistry,4 and in materials
chemistry5,6 to name but a few. It has been well estab-
lished that molecular structures with differences between
ground state and excited state dipole moments and large
transition moments have large second-order nonlinear op-
tics.7 Molecules with p-donor–acceptor interactions such
as ferrocene or its derivatives show promise in nonlinear
optics,8 thus biaryl ferrocenyl organic compounds have
been synthesized due to their extended molecular conju-
gation.9 More recently there has been much effort devoted
–
[ArB(OH)3 ] before transmetallation, and it was supposed
O
3
O
O
H
O
Br
Pd(0)
Fc
Ac2O
Fc
FcH
Ar
Br
Fc
ArB(OH)2
NaOH
H3PO4
1
2
4
5
6
F
F
F
F
F
F
Fc = ferrocenyl, Ar =
F
,
,
Scheme 1
SYNTHESIS 2006, No. 1, pp 0123–0127
0
6
.
0
1
.2
0
0
6
Advanced online publication: 16.12.2005
DOI: 10.1055/s-2005-921748; Art ID: F07105SS
© Georg Thieme Verlag Stuttgart · New York

124
Q.-b. Song et al.
PAPER
that this anion was the reactive species rather than the neu-
tral arylboronic acid. We hypothesize in our experiments
–
that ArB(OH)2 was fully transformed into ArB(OH)3 be-
Table 1 Suzuki Cross-Coupling Reaction of 1-Ferrocenyl-3-(4¢-
bromophenyl)- 2-propen-1-one with 3,4,5-Trifluorophenylboronic
Acid with Pd(0) Catalysta
fore transmetallation by the method described. As trans-
metallation is the key step in the Suzuki cross-coupling
reaction, the increase in the rate of the reaction can be at-
tributed to the generation of the trihydroxyarylboronate
(Table 1).
Entry Temperature Time
(h)
Solvent b
Conversion
(%)
(°C)
110
100
90
78
78
78
95
95
60
54
66
66
76
76
66
66
78
66
66
90
78
100
66
66
80
80
66
1
2
1.0
DMF
96
76
80
64
48
80
65
83
57
42
96
100
45
98
25
62
89
35
75
95
0
1.0
2.5
DMF
Secondly, the role of the solvent was investigated. It can
be seen that polar solvents such as alcohols, DMF, THF,
and acetone are superior to non-polar solvents such as
benzene and toluene in this reaction, a trend which has
been observed by others.14 It is possible that, in polar sol-
vents, the solvent, aqueous base solution, catalyst, and
substrate formed a homogeneous solution, which leads to
a much-increased probability of collision and thus re-
markably improved the speed of the reaction. As the sol-
ubility of the reaction components was better in methanol
than in the other alcohols tested, the lower yields obtained
in Table 1, entries 13, 15 and 18 may be explained by low-
er homogeneity of the reaction mixture. It was also ob-
served that a faster reaction rate occurred in protic
solvents rather than in polar aprotic solvents, this can be
seen in particular with methanol when the reaction was
complete in 30 minutes under reflux (Table 1, entry 12).
3
DMF
4
2.5
DMF
5
4.0
Benzene
Benzene
Toluene
Toluene
THF
6
24.0
4.0
7
8
16.5
4.0
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27d
4.0
Acetone
MeOH
MeOH
EtOH
0.25
0.50
0.25
1.0
In an aqueous system, the reaction time was substantially
increased, however, a reasonable yield was achieved with
tetramethylammonium chloride as the phase-transfer cat-
alyst (Table 1, entries 24, 25, and 26). DMSO was found
to be unsuitable for the reaction (Table 1, entries 21–23);
even a small amount of DMSO was found to inhibit the re-
action (MeOH–DMSO, 30:1). It was supposed that the
catalyst was poisoned by low-valence sulfur in DMSO.
EtOH
0.5
i-PrOH
i-PrOH
i-PrOH
PrOH
2.5
1.0
0.5
2.5
PrOH
Finally, the relationship between solvent or temperature
and byproducts was investigated. At 80 °C and above
byproducts started to appear and accumulated as the tem-
perature increased. However, with DMF as the solvent,
unidentified, insoluble byproducts were observed even
below 78 °C.
0.25
PrOH
24.0
DMSO
DMSO
MeOH–DMSO (5:1)
H2O–EtOAc (15:2)c
H2Oc
24.0
24.0
24.0
14.0
43.5
8.0
0
0
Due to the advantages of stepwise addition, we applied it
to a general Suzuki cross-coupling reaction of aryl halides
and arylboronic acids and found that the reaction rate was
much improved (Table 2).
57
35
69
80
H2Oc
Thus, taking into account cost, byproducts formed, and
the reaction rate, we expanded the synthetic utility of this
methodology. Six novel fluorine-substituted organome-
tallic compounds were synthesized using the above meth-
odology (Scheme 2, Table 3). 3-Biaryl-1-ferrocenyl-2-
propene-1-ones, were formed by stepwise addition of re-
agents in methanol. The reaction rate increased when one
third of the volume of methanol, arylboronic acid, and so-
dium carbonate were refluxed for five minutes, and then
the other reagents (catalyst, halide, and remaining metha-
nol) were added. Byproducts were not observed when the
addition was carried out in this way.
MeOH
a 1-Ferrocenyl-3-(4′-bromophenyl)-2-propen-1-one (20 mg), 3,4,5-
trifluorophenyl boronic acid (11.6 mg), aq solution Na2CO3 (2 M, 0.2
mL), solvent (15 mL), Pd(PPh3)4 (3 mmol%). Stepwise addition un-
der a N2 atmosphere.
b All solvents were used as received.
c Phase-transfer catalyst (C4H9)4N+Cl– (70% in water; 5%) was added.
d All materials were mixed at the same time under a N2 atmosphere.
Synthesis 2006, No. 1, 123–127 © Thieme Stuttgart · New York

PAPER
Fluorine-Substituted 3-Biaryl-1-ferrocenyl-2-propen-1-one
125
Table 2 Suzuki Cross-Coupling Reaction of Halides and Boronic Acida
Entry
1b
Time (h)
1.5
Halide
Boronic acid
Conversion (%)
98
O
O
B(OH)2
Br
2c
3b
4c
5b
6c
7b
4.0
90
95
92
90
89
90
B(OH)2
Br
Br
Br
0.25
1.0
CHO
CHO
B(OH)2
B(OH)2
B(OH)2
B(OH)2
B(OH)2
1.0
O
O
Br
Br
3.0
0.25
Br
Br
8c
6.5
65
B(OH)2
9b
0.25
1.0
85
80
Br
Br
B(OH)2
B(OH)2
10c
a Aryl bromide (20 mg), boronic acid (1.1 equiv), Na2CO3 (3.8 equiv), solvent (8 mL), Pd(PPh3)4 (3 mmol%), reflux, MeOH, under N2 atmo-
sphere.
b Stepwise addition of reagents.
c Reagents added at the same time.
O
O
Table 3 Pd(0)-Catalyzed Suzuki Cross-Coupling Reaction of 1-
Ferrocenyl- 3-(4¢/2¢)-bromophenyl)-2-propen-1-one with Fluorine-
Substituted Arylboronic Acidsa
Fc
Fc
Br
Ar
4a
Entry
Bromide Substrate Product Tempera- Conver-
ture (°C) sion (%)b
6a, 6b, 6c
Pd(0)
ArB(OH)2
1
2
3
4
5
6
4a
4a
4a
4b
4b
4b
5a
5b
5c
5a
5b
5c
6a
6b
6c
6d
6e
6f
66
66
66
66
66
66
98
94
96
97
93
96
O
Ar
O
Br
Fc
Fc
4b
6d, 6e, 6f
Fc = ferrocenyl
F
F
F
F
(HO)2B
F
ArB(OH)2
=
(HO)2B
a Halide (1 mmol), arylboronic acid (1.2 mmol), aq soln Na2CO3 (2
M; 3.8 mmol), MeOH (40 mL), Pd(PPh3)4 (3 mmol%), 1 h. Stepwise
addition of reagents under a N2 atmosphere.
(HO)2B
F
F
5b
5c
5a
b Determined by HPLC.
Scheme 2
1H and 13C NMR spectra were performed on a Mercury Plus 400
MHz NMR spectrometer in CDCl3 with TMS as an internal refer-
ence. IR spectra were record on a Bruker Vector-22 spectrometer as
KBr pellets. Mps were determined with a X-4 digital display binoc-
ular microscope and were uncorrected. EtOH (95%) was used.
Acetylferrocene,12 3,4,5-trifluorophenylboronic acid, 3,4-difluoro
phenylboronic acid, and 3,5-difluorophenylboronic acid,13a,b and
Pd(0)13c were prepared by known procedures.
Synthesis 2006, No. 1, 123–127 © Thieme Stuttgart · New York

126
Q.-b. Song et al.
PAPER
1-Ferrocenyl-3-[2¢-bromophenyl]-2-propen-1-one (4a); Typical
Procedure
3-[4¢-(3¢¢,4¢¢-Difluorophenyl)phenyl]-1-ferrocenyl-2-propen-1-
one (6c)
Acetylferrocene (2; 5.7 g, 25 mmol) was dissolved in EtOH (20
mL), p-bromobenzaldehyde (3a; 4.8 g, 26 mmol) in EtOH (6 mL)
was added with stirring. Stirring was continued for 0.5 h until all the
solid had dissolved. A solution of EtOH (20 mL), H2O (20 mL), and
NaOH (2.0 g, 50 mmol) was added dropwise under stirring at r.t. A
reddish precipitate appeared after 1 h, and continued to form, even-
tually preventing stirring after 2 h. When the reaction was complete
(TLC) the mixture was poured into H2O (200 mL) and HCl (2 M)
was added until the pH of the solution reached 7. The reaction was
cooled, filtered, the solid was washed with H2O (3 × 20 mL), and
dried in vacuo. The crude product was recrystallized (CHCl3) to
give 4a as dark claret crystals (8.1 g, 96%); mp 111–113 °C; Rf 0.36
(EtOAc–petroleum ether, 1:8).
Yield: 85% (0.364 g); red crystals; mp 178–179 °C; Rf 0.34 (petro-
leum ether–EtOAc, 6:1).
IR (KBr): 3090, 1652, 1594, 1499, 1376, 1265, 1079, 981, 817, 771,
547 cm–1.
1H NMR (400 MHz, CDCl3): d = 7.83 (d, 1 H, J = 15.6 Hz), 7.73
(d, 2 H, J = 8.4 Hz), 7.59 (d, 2 H, J = 7.2 Hz), 7.46–7.40 (m, 1 H),
7.36–7.33 (m, 1 H), 7.29–7.22 (q, 1 H), 7.19 (d, 1 H, J = 15.2 Hz),
4.94 (s, 2 H), 4.62 (s, 2 H), 4.23 (s, 5 H).
13C NMR (100 MHz, CDCl3): d = 192.82, 150.55 (dd, C3¢¢ or C4¢¢,
J = 246.6, 12.9 Hz), 150.17 (dd, C4¢¢ or C3¢¢, J = 248.0, 12.1 Hz),
140.57, 139.87, 137.31 (t, C1¢¢, J = 5.3 Hz), 134.70, 128.84, 127.36,
123.48, 122.95 (dd, C6¢¢, J = 6.5, 3.8 Hz), 117.69 (d, C2¢¢ or C5¢¢,
J = 17.5 Hz), 115.89 (d, C5¢¢ or C2¢¢, J = 17.4 Hz), 81.08, 72.88,
70.12, 69.73.
Fluorine-Substituted 3-Biaryl-1-ferrocenyl-2-propen-1-ones 6;
General Procedure
Anal. calcd for C25H18F2FeO: C, 70.11; H, 4.24. Found: C, 70.08;
H, 4.20.
A 100-mL three-necked round-bottomed flask was charged with
arylboronic acid (5; 1.2 mmol), MeOH (10 mL), and an aq solution
of Na2CO3 (2 M; 2 mL) under a N2 atmosphere. The mixture was
heated to reflux and stirred vigorously; after 5 min halide 4 (1
mmol), Pd(PPh3)4 (0.03 mmol), and MeOH (30mL) were added, un-
der a N2 atmosphere. After the reaction was complete (TLC), the re-
action mixture was cooled to r.t. and the solvents were removed in
vacuo to give the crude product. The crude product was purified by
column chromatography (neutral alumina; petroleum ether–
EtOAc, 4:1→20:1; the first red band was the starting material and
the second red band was the product). The second fraction was con-
centrated in vacuo to give pure 6.
3-[2¢-(3¢¢,4¢¢,5¢¢-Trifluorophenyl)phenyl]-1-ferrocenyl-2-pro-
pen-1-one (6d)
Yield: 82% (0.367 g); red crystals, mp 171–172 °C; Rf 0.41 (petro-
leum ether–EtOAc, 6:1).
IR (KBr): 3075, 1649, 1588, 1531, 1449, 1367, 1239, 1045, 832,
767, 488 cm–1.
1H NMR (400 MHz, CDCl3): d = 7.80 (br, 1 H), 7.71 (d, 1 H,
J = 15.6 Hz), 7.47 (br, 2 H), 7.32 (br, 1 H), 7.03 (d, 1 H, J = 20.8
Hz), 7.00–6.98 (m, 2 H), 4.86 (s, 2 H), 4.60 (s, 2 H), 4.21 (s, 5 H).
13C NMR (100 MHz, CDCl3): d = 192.58, 150.92 (dd, C3¢¢,5¢¢
,
3-[4¢-(3¢¢,4¢¢,5¢¢-Trifluorophenyl)phenyl]-1-ferrocenyl-2-pro-
pen-1-one (6a)
Yield: 76% (0.340 g); red crystals; mp 182–183 °C; Rf 0.35 (petro-
leum ether–EtOAc, 6:1).
J = 251.1, 9.9 Hz), 139.96, 139.44 (dt, C4¢¢, J = 250.7, 15.3Hz),
138.49, 136.15 (m, C1¢¢), 133.49, 130.28, 129.80, 128.64, 127.15,
125.42, 113.97 (d, C2¢¢,6¢¢, J = 19.6 Hz), 80.46, 72.90, 70.07, 69.71.
Anal. calcd for C25H17F3FeO: C, 67.29; H, 3.84. Found: C, 67.22;
H, 3.77.
IR (KBr): 3080, 1651, 1537, 1506, 1455, 1252, 1076, 1039, 821,
746, 531 cm–1.
1H NMR (400 MHz, CDCl3): d = 7.82 (d, 1 H, J = 15.6 Hz), 7.74
(d, 2 H, J = 8.0 Hz), 7.57 (d, 2 H, J = 8.0 Hz), 7.23 (d, 2 H, J = 7.2
Hz), 7.17 (d, 1 H, J = 15.2 Hz), 4.94 (s, 2 H), 4.63 (s, 2 H), 4.24 (s,
5 H).
3-[2¢-(3¢¢,5¢¢-Difluorophenyl)phenyl]-1-ferrocenyl-2-propen-1-
one (6e)
Yield: 84% (0.361 g); red crystals; mp 138–139 °C; Rf 0.44 (petro-
leum ether–EtOAc, 6:1).
13C NMR (100 MHz, CDCl3): d = 192.74, 151.43 (dq, C3¢¢,5¢¢
,
IR(KBr): 3075, 1648, 1587, 1449, 1376, 1240, 1081, 986, 830, 762,
548 cm–1.
J = 253.4, 9.9 Hz), 139.62, 139.53 (dt, C4¢¢, J = 251.0, 15.2 Hz),
139.41, 136.37 (m, C1¢¢), 135.28, 128.91, 127.30, 123.56, 110.97
(dd, C2¢¢,6¢¢, J = 16.0, 6.1 Hz), 80.50, 72.92, 70.13, 69.75.
1H NMR (400 MHz, CDCl3): d = 7.80 (m, 1 H), 7.74 (d, 1 H,
J = 15.6 Hz), 7.49–7.46 (m, 2 H), 7.36–7.33 (m, 1 H), 7.01 (d, 1 H,
J = 15.6 Hz), 6.91–6.83 (m, 3 H), 4.85 (s, 2 H), 4.59 (s, 2 H), 4.20
(s, 5 H).
Anal. calcd for C25H17F3FeO: C, 67.29; H, 3.84. Found: C, 67.20;
H, 3.78.
13C NMR (100 MHz, CDCl3): d = 192.90, 162.73 (dd, C3¢¢,5¢¢
J = 248.0, 12.9 Hz), 143.52 (t, C1¢¢, J = 9.3 Hz), 140.69, 138.80,
133.51, 130.26, 129.72, 128.52, 127.30, 125.87, 112.83 (dd, C2¢¢,6¢¢
J = 19.0, 6.8 Hz), 103.07 (t, C4¢¢, J = 25.0 Hz), 80.68, 72.88, 70.09,
69.72.
,
3-[4¢-(3¢¢,5¢¢-Difluorophenyl)phenyl]-1-ferrocenyl-2-propen-1-
one (6b)
Yield: 88% (0.375 g); red crystals; mp 162–163 °C; Rf 0.38 (petro-
leum ether–EtOAc, 6:1).
,
IR (KBr): 3088, 1655, 1596, 1458, 1377, 1241, 1081, 987, 829, 760,
542 cm–1.
Anal. calcd for C25H18F2FeO: C, 70.11; H, 4.24. Found: C, 69.92;
H, 4.12.
1H NMR (400 MHz, CDCl3): d = 7.83 (d, 1 H, J = 15.6 Hz), 7.74
(d, 2 H, J = 7.2 Hz), 7.62 (d, 2 H, J = 7.6 Hz), 7.17 (d, 1 H, J = 14.8
Hz), 7.16–7.14 (d, 2 H, J = 5.6 Hz), 6.83 (t, 1 H, J = 7.6 Hz), 4.94
(s, 2 H), 4.62 (s, 2 H), 4.24 (s, 5 H).
3-[2¢-(3¢¢,4¢¢-Difluorophenyl)phenyl]-1-ferrocenyl-2-propen-1-
one (6f)
Yield: 89% (0.380 g); red crystals; mp 134–135 °C; Rf 0.42 (petro-
leum ether–EtOAc, 6:1).
13C NMR (100 MHz, CDCl3): d = 193.66, 163.67 (dd, C3¢¢,5¢¢
,
J = 246.5, 12.9 Hz), 143.84 (t, C1¢¢, J = 9.4 Hz), 140.60, 140.04,
135.68, 129.19, 127.78, 124.36, 110.17 (dd, C2¢¢,6¢¢, J = 18.6, 7.0
Hz), 103.30 (t, C4¢¢, J = 25.0 Hz), 81.90, 73.26, 70.45, 70.05
IR: 3095, 1649, 1586, 1450, 1312, 1261, 1080, 987, 823, 762, 548
cm–1.
1H NMR (400 MHz, CDCl3): d = 7.80 (br, 1 H), 7.74 (d, 1 H,
J = 16.0 Hz), 7.46 (br, 2 H), 7.35 (br, 1 H), 7.24–7.19 (m, 2 H),
Anal. calcd for C25H18F2FeO: C, 70.11; H, 4.24. Found: C, 69.96;
H, 4.15.
Synthesis 2006, No. 1, 123–127 © Thieme Stuttgart · New York

PAPER
Fluorine-Substituted 3-Biaryl-1-ferrocenyl-2-propen-1-one
127
7.17–7.00 (m, 1 H), 7.02 (d, 1 H, J = 15.6 Hz), 4.85 (s, 2 H), 4.59
(s, 2 H), 4.20 (s, 5 H).
(6) Iyoda, M.; Okobe, T.; Katada, M.; Kuwatani, Y. J.
Organomet. Chem. 1996, 569, 225.
(7) (a) Green, M. L. H.; Green, S. R.; Thompson, M. E.; Bandy,
J. A.; Bloor, D.; Konlinsky, P. V.; Jones, R. J. Nature
(London) 1987, 330, 360. (b) Calabrese, J. C.; Cheng, L. T.;
Green, J. C.; Marder, S. R.; Tam, W. J. Am. Chem. Soc.
1991, 113, 7227.
(8) Rodríguez, J.-G.; Pleite, S. J. Organomet. Chem. 2001, 637,
230.
(9) (a) Song, Q.-B.; Lin, R.-X.; Shen, T.-H. Synth. Commun.
2004, 34, 2223. (b) Song, Q.-B.; Li, X.-N.; Shen, T.-H.;
Yang, S.-D.; Qiang, G.-R.; Wu, X.-L.; Ma, Y.-X. Synth.
Commun. 2003, 33, 3935.
13C NMR (100 MHz, CDCl3): d = 192.69, 150.01 (dm, J = 247.7
Hz), 140.91, 139.10, 138.42 (s, C1¢¢), 137.11, 133.49, 130.48,
129.72, 128.20, 127.12, 125.96 (s, C6¢¢), 118.66 (dd, C2¢¢ or C5¢¢,
J = 17.4, 8.7 Hz), 117.23 (d, C5¢¢ or C2¢¢, J = 17.4 Hz), 80.34, 72.80,
70.04, 69.68.
Anal. calcd for C25H18F2FeO: C, 70.11; H, 4.24. Found: C, 70.02;
H, 4.13.
References
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