Improved Suzuki-Miyaura reactions of aryldiazonium salts with boronic acids by tuning palladium on charcoal catalyst properties

Article abstract of DOI:10.1002/adsc.200800783

An improved Suzuki-Miyaura cross-coupling reaction of aryldiazonium tetrafluoroborates with boronic acids catalyzed by a highly active palladium catalyst supported on charcoal is described as an extremely practical and efficient protocol. A properties-activity study of various catalysts clearly established that the optimal catalytic activity was obtained with palladium nanoparticles having a low oxidation degree and uniformly dispersed on the charcoal. The optimized reaction conditions allow the cross-coupling to proceed at room temperature without any base and ligand in technical grade methanol. Although the catalyst could not be recycled, the low palladium contamination of the solvent and product after a simple filtration of the palladium on charcoal (Pd/C) renders the present protocol competitive and safer for the environment compared to more conventional homogeneous conditions. We have highlighted the efficiency of this novel protocol by a short synthesis of the fungicide Boscalid

Full text of DOI:10.1002/adsc.200800783

UPDATES
DOI: 10.1002/adsc.200800783
Improved Suzuki–Miyaura Reactions of Aryldiazonium Salts
with Boronic Acids by Tuning Palladium on Charcoal Catalyst
Properties
a,
a
b
FranÅois-Xavier Felpin, * Eric Fouquet, and Cꢀcile Zakri
a
Universitꢀ de Bordeaux, CNRS, Institut des Sciences Molꢀculaires, 351 Cours de la Libꢀration, 33405 Talence, France
Fax : (+33)-5-4000-6286; e-mail: fx.felpin@ism.u-bordeaux1.fr
Universitꢀ de Bordeaux, CNRS, Centre de Recherche Paul Pascal, Avenue Schweitzer, 33600 Pessac, France
b
Received: December 17, 2008; Revised: February 4, 2009; Published online: February 13, 2009
Abstract: An improved Suzuki–Miyaura cross-cou-
pling reaction of aryldiazonium tetrafluoroborates
with boronic acids catalyzed by a highly active pal-
ladium catalyst supported on charcoal is described
as an extremely practical and efficient protocol. A
properties-activity study of various catalysts clearly
established that the optimal catalytic activity was
obtained with palladium nanoparticles having a low
oxidation degree and uniformly dispersed on the
charcoal. The optimized reaction conditions allow
the cross-coupling to proceed at room temperature
without any base and ligand in technical grade
methanol. Although the catalyst could not be recy-
cled, the low palladium contamination of the sol-
vent and product after a simple filtration of the pal-
ladium on charcoal (Pd/C) renders the present pro-
tocol competitive and safer for the environment
compared to more conventional homogeneous con-
ditions. We have highlighted the efficiency of this
novel protocol by a short synthesis of the fungicide
around the world which has led to highly efficient
procedures.
[
4]
On the other hand, the progress of modern sustain-
able chemistry has become a major concern to solve
many environmental issues we must face. In this con-
text, we recently started a program aimed at the de-
velopment of easy-to-handle palladium-catalyzed re-
[
5]
actions. Our approach is based on the use of robust
and inexpensive heterogeneous catalysts employing
non-anhydrous and non-degassed conditions. We also
revisited the chemistry of aryldiazonium salts as
[
6]
highly reactive aryl halide surrogates. For instance,
we recently published an easy to handle protocol for
the cross-coupling reactions of boronic acids with ar-
[
5d]
yldiazonium salts catalyzed by Pd(0)/C. The proce-
dure allows selective and fast reactions (5–30 min)
under ligandless and base-free conditions in technical
grade methanol at 508C. However, the cross-coupling
worked best with a rather high loading (5 mol% Pd)
of a not well-defined commercially available palladi-
um catalyst. Considering that a fine-tuning of catalyst
properties could considerably improve the catalytic
efficiency and thereby solve the loading issues, we en-
gaged in a property-activity relationship study of vari-
ꢁ
Boscalid .
Keywords: aryldiazonium tetrafluoroborates; palla-
dium on activated charcoal; practical cross-cou-
pling; sustainable chemistry; Suzuki–Miyaura reac-
tion
[
7]
ous Pd/C catalysts.
In this paper we established that the properties of
Pd/C catalysts dramatically influence the reaction out-
come. Our newly designed protocol allows cross-cou-
pling at 258C under ligandless and base-free condi-
tions with loading as low as 0.1–0.9 mol% Pd.
Introduction
Palladium-catalyzed cross-coupling reactions have Results and Discussion
profoundly impacted the development of organic
[
1]
chemistry these last decades. The Suzuki–Miyaura In this study we examined four catalysts differing by
cross-coupling reaction is probably one of the most their oxidation degree [i.e., Pd(0) or Pd(II)] and the
relevant palladium-mediated methods for CÀC bond Pd distribution over charcoal (i.e., eggshell or uni-
formation that allows the coupling of aryl and vinyl form). An eggshell distribution means that palladium
[
2]
halides with boron compounds. The pioneering stud- nanoparticles are distributed close to the surface of
[
3]
ies of Suzuki and Miyaura have been followed by an the charcoal. A uniform distribution means that palla-
impressive amount of work from laboratories all dium nanoparticles are homogeneously dispersed in
Adv. Synth. Catal. 2009, 351, 649 – 655
ꢂ 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
649

FranÅois-Xavier Felpin et al.
UPDATES
Table 1. Optimization studies.
Figure 1. Cross-coupling reaction of diazonium salt 1a with
4
-chlorophenylboronic acid 2a catalyzed by 0.1 mol% Pd
(
catalyst A) in MeOH (258C, 12 h) at various concentra-
tions.
yield drops drastically to 46% with more diluted con-
ditions (0.05M) while concentrated solutions were
less damaging. It has been observed that more diluted
conditions favour the de-diazotization pathway lead-
ing to unwanted by-products.
With the carefully optimized conditions in hand, we
compared catalysts A–D with different heterogeneous
and homogeneous palladium sources (Figure 2). Im-
[
[
a]
b]
Concentration of the diazonium salt.
Cat. A: Pd(0)/C-uniform; Cat. B: Pd(0)/C-eggshell; Cat.
C: Pd(II)/C-uniform; Cat. D: Pd(II)/C-eggshell.
Yields are an average of at least two runs
[
c]
the charcoal. The support has a BET surface area of pressively, catalyst A showed a significantly high cata-
2
À1
approximately 800 m g . In addition, all the catalysts lytic activity that overpassed all other catalysts tested
were ligandless and were selected at a constant load- in this study. Catalyst A gave 3a with even higher
ing (i.e., 5 wt.% Pd on charcoal) and with 50% water yield than Pd ACHTUNGTRENN(UNG OAc) (catalyst G), the widely used ho-
2
[
8]
content for safety issues.
As reported in Table 1, our preliminary studies led tions.
us to consider the Pd/C-catalyzed cross-coupling of 2- With the realization of an optimized protocol, the
methoxy-3-nitrobenzenediazonium tetrafluoroborate scope and limitations of this cross-coupling were in-
a and 4-chlorobenzeneboronic acid 2a in undistilled vestigated (Table 2). A variety of substituted biphen-
mogeneous catalyst for such cross-coupling reac-
[
7]
1
technical grade MeOH at 258C under air and with no yls was efficiently prepared under mild conditions
external additives (base and ligand). Interestingly, the with a low loading of palladium. All aryldiazonium
four catalysts studied (catalysts A–D) were all active tetrafluoroborates were easily accessed by reacting
for this cross-coupling with 1 mol% Pd although cata-
lyst C was slightly less active. In contrasting, lowering
the loading to 0.1 mol% Pd significantly highlighted
the performance of catalyst A in comparison to the
other three catalysts B–D (entry 9 versus entries 10–
12). From those preliminary studies it was clear that
the optimal catalytic activity was obtained with palla-
dium nanoparticles having a low oxidation [Pd(0)]
degree and uniformly dispersed on the charcoal. We
also experienced that for most cross-couplings studied
in this work, it was preferable to use 1.5 equivalents
of the diazonium salt. Lowering the quantity of diazo-
nium salts to 1.2 equivalents could slightly alter the
yield due to de-diazotization pathways (entry 13).
The impact of the diazonium salt concentration on
the yield of the cross-coupling leading to 3a was also
studied (Figure 1). From that work, we noticed that
Figure 2. Cross-coupling reaction of diazonium salt 1a with
-chlorophenylboronic acid 2a catalyzed by 0.1 mol% Pd
catalysts A–G) in MeOH at 258C for 12 h. Cat. E: Pd/C
4
(
[6a]
the reaction was best conducted with a diazonium salt (catalyst used in refer. ), Cat. F: Pd(0)/BaCO , Cat. G: Pd-
3
concentration in the range of 0.1–0.2M. Indeed, the
ACHTUNGTRENNUNG( OAc)
2
650
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ꢂ 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Adv. Synth. Catal. 2009, 351, 649 – 655

Improved Suzuki–Miyaura Reactions of Aryldiazonium Salts with Boronic Acids
UPDATES
Table 2. Scope of the cross-coupling.
[
[
a]
b]
Yields are an average of two runs.
No reaction.
the corresponding anilines with sodium nitrite and partners was not prohibitive for the success of the re-
[
9]
tetrafluoroboric acid. Importantly, the prepared ar- action. Indeed, it has been reported that 2-nitrobenze-
yldiazonium tetrafluoroborates showed excellent sta- nediazonium salts failed to participate in the Suzuki
bility over years when stored at À208C. Diazonium reaction with arylboronic acids with 10 mol%
[
6f]
electrophiles compete favourably with less reactive Pd ACTHUNGTERNN(UGN OAc) in methanol. This failure has been ascri-
2
and more expensive halogenated electrophiles as ex- bed to the high redox potentials and a preference for
[
10]
emplified by reported industrial applications.
To homolytic de-diazonization pathways. However,
our delight, the use of 2-nitrobenzenediazonium salt recent reports overcome this failure by the use of a
[
11]
1
d and 4-nitrobenzenediazonium salt 1e as coupling C -symmetrical thiourea as ligand, non-protic con-
2
Adv. Synth. Catal. 2009, 351, 649 – 655
ꢂ 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
asc.wiley-vch.de
651

FranÅois-Xavier Felpin et al.
UPDATES
Scheme 1.
[6k]
[5b]
ditions or other sources of palladium. The meth- solution at the end of the reaction as indicated by
odology is tolerant to a variety of electronically differ- ICP-MS analyses. For a deeper understanding of the
ent substituents. Importantly, ortho- and especially or- deactivation during the recycling process we investi-
tho,ortho’-disubstitued biphenyls can be prepared in gated the catalyst evolution by transmission electron
good yields while still maintaining the low loading of microscopy (TEM). As shown in Figure 3, a signifi-
the catalyst (entry 10). These results are in sharp cant increase of the average of particle size from
contrast with few reports that describe the inability 20 nm to 120 nm occurred during the reaction and
of diazonium salts to participate in such cross-cou- was correlated with the strong deactivation of the cat-
[6e,f]
plings.
It should be noted that mesityldiazonium alyst. This observation supports a homogeneous
salt 1g remained reluctant to participate in the cross- mechanism where catalytically active palladium nano-
[
6b]
coupling as already observed by GenÞt et al.
particles are leached from the support and latter re-
We further explored the catalyst recycling for the precipitated onto the charcoal at the end of the cata-
[12]
preparation of biphenyl 3f (Scheme 1). Unfortunately, lytic cycle as already observed by other groups.
after the first run, the reused catalyst showed a strong However, the extremely mild conditions (258C) used
deactivation leading to a modest yield of compound in this study ruled out a temperature-induced leaching
3
f.
that could most likely occur during the oxidative addi-
The inability to recycle the catalyst could not be at- tion of the diazonium salt.
tributed to a lower loading of palladium nanoparticles
on the charcoal since only 3% of soluble palladium a short and highly efficient synthesis of Boscalid 5 a
The power of our protocol was then highlighted by
ꢁ
species (based on 100% introduced) remained in the new fungicide marketed by BASF company
Figure 3. TEM images of the fresh catalyst A (left) and the reused catalyst A (right) at the same magnification.
652
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Adv. Synth. Catal. 2009, 351, 649 – 655

Improved Suzuki–Miyaura Reactions of Aryldiazonium Salts with Boronic Acids
UPDATES
ꢁ
Scheme 2. Short synthesis of Boscalid .
ꢁ
(
Scheme 2). Boscalid 5 is used to control a range of Experimental Section
plant pathogens in broadacre and horticultural crops.
Although the patent application does not fully de- General Remarks
[
13]
ꢁ
scribe its synthesis, Boscalid 5 is currently one of
Chemical shifts from proton and carbon NMR spectra are
the largest industrial applications of the Suzuki–
Miyaura reaction (ca. 1000 tons/year). Spivey et al.
reported a synthesis of the fungicide based on a Pd-
reported in ppm relative to the CDCl peak at 7.26 ppm
3
[
14]
1
13
(
H) or 77.0 ppm ( C). Infrared (IR) spectra were recorded
as neat samples on NaCl plates or with KBr pellets. The
catalyzed reaction of an arylgermane to form the bi- transmission electron microscopy (TEM) images have been
[15]
phenyl core. Very recently, Heinreich et al. report- performed with a Hitachi H-600 microscope. The catalysts
ed a novel synthesis of Boscalid based on a original were dispersed into methanol and samples of the solution
[
16]
have been taken and air-dried onto standard Formar/
carbon-coated copper support grids. The micrographs of this
work have been realised with the same magnification.
free-radical biaryl cross-coupling.
As pointed out before, the cross-coupling of 2-ni-
trobezenediazonium tetrafluoroborate 1d with 4-
chlorobenzeneboronic acid 2a gave a high yield of 3e
Yields refer to isolated material determined to be pure by
NMR spectroscopy and thin layer chromatography (TLC),
unless specified otherwise in the text. Diazonium salts used
in this study were all known and prepared as described in
the literature. Pd/C catalysts were commercially available
(
95%) under extremely mild conditions (258C). A
practical and particularly efficient iron-mediated re-
duction of the nitro group furnished 4 in 97% yield.
ꢁ
Targeted Boscalid 5 was finally obtained from the from Evonik Degussa GmbH, Business Line Catalysts. An
coupling of biphenylamine 4 with nicotinoyl chloride eggshell distribution means that palladium nanoparticles are
7
(prepared from commercially available 2-chloroni- distributed close to the surface of the charcoal. A uniform
distribution means that palladium nanoparticles are homo-
cotinic acid 6). The three-steps synthesis proceeds
with an exceptional 87% overall yield and could po-
tentially be carried out on a larger scale.
geneously dispersed in the charcoal.
General Procedure for the Preparation of Biphenyl
To a solution of diazonium salt (1.5 mmol) in MeOH
Conclusions
(
15 mL) were added ArB(OH) (1 mmol) and 5% Pd(0)/C
2
(
0.1–0.9 mol%, see Table 2). The resulting mixture was
In summary, we have developed a practical, efficient stirred for 12 h at 258C and then filtered and concentrated
and general protocol for the cross-coupling of aryl- under reduced pressure. The crude was purified by flash
chromatography to give the corresponding cross-coupled
ACHTUNGTRENNUNGd iazonium tetrafluoroborate salts with boronic acids
product.
catalyzed by a well-defined Pd/C catalyst. The
method has a wide substrate scope and provides bi-
phenyls under particularly mild conditions without
any additional additives (base and ligand). A short
and efficient synthesis of the antifungal Boscalid
supports the usefulness of our protocol. We anticipat-
4
-Chloro-2’-methoxy-3’-nitrobiphenyl (3a): Purification by
flash chromatography (10% EtOAc-petroleum ether) gave a
white solid; mp 1278C [Lit.
[17]
120–1228C]. IR (KBr): n=
À1
1
1
3
7
584, 1615, 2844, 2922, 2980, 3090 cm ; H NMR (CDCl ,
00 MHz): d=3.94 (s, 3H), 7.04 (d, 1H, J=7.5 Hz), 7.40–
.48 (m, 4H), 8.19 (d, 1H, J=2.2 Hz), 8.25 (dd, 1H, J=2.2,
3
ꢁ
1
3
ed that this methodology could be of interest for me- 7.5 Hz); C NMR (CDCl , 75 MHz): d=56.3, 110.8, 125.1,
3
dicinal, as well as, process chemists.
126.1, 128.5, 130.1, 130.7, 134.1, 134.5, 141.5, 161.3; MS (EI):
Adv. Synth. Catal. 2009, 351, 649 – 655
ꢂ 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
asc.wiley-vch.de
653

FranÅois-Xavier Felpin et al.
UPDATES
3
5
37
+
35
m/z=265 (M, Cl), 265 (M, Cl), 264 (M+H , Cl), 266
(
4
6H, J=6.9 Hz), 2.99 (sep, 1H, J=7.3 Hz), 3.87 (s, 3H), 7.00
(d, 2H, J=8.5 Hz), 7.32 (d, 2H, J=8.1 Hz), 7.51–7.58 (m,
+
37
M+H , Cl).
-Methoxy-4’-nitrobiphenyl (3b): Purification by flash
chromatography (5% EtOAc-petroleum ether) gave
yellow solid; mp 1068C [Lit. 107–1088C]. IR (KBr): n=
930, 2968, 3052 cm ; H NMR (CDCl , 250 MHz): d=3.88
1
3
4H); C NMR (CDCl , 75 MHz): d=24.0, 33.7, 55.3, 114.1,
3
a
126.6, 126.8, 127.0, 133.7, 138.3, 147.3, 158.9; HR-MS (elec-
[
18]
+
trospray): m/z=249.1252, calcd. for C16
H
18ONa (M+Na ):
À1
1
2
249.1250.
3
(
s, 3H), 7.02 (dt, 2H, J=3.1, 8.9 Hz), 7.58 (dt, 2H, J=3.1,
2-Bromo-2’-methylbiphenyl (3j): Purification by flash
8
9
1
.9 Hz), 7.69 (dt, 2H, J=2.4, 9.2 Hz), 8.27 (dt, 2H, J=2.4,
chromatography (100% petroleum ether) gave a colorless
13
À1
1
.2 Hz); C NMR (CDCl , 75 MHz): d=55.4, 114.6, 124.1,
oil. IR (neat): n=1465, 2922, 3018, 3057 cm ; H NMR
(CDCl , 250 MHz): d=2.12 (s, 3H), 7.11–7.15 (m, 1H),
7.19–7.40 (m, 6H), 7.64–7.69 (m, 1H); C NMR (CDCl ,
3
3
27.0, 128.5, 131.0, 146.5, 147.2, 160.4; MS (EI): m/z=229
3
1
3
(
M).
-Methoxy-4-nitrobiphenyl (3c): Purification by flash
2
62.5 MHz): d=19.8, 123.7, 125.5, 127.2, 127.9, 128.7, 129.2,
129.8, 130.8, 132.5, 135.9, 141.1, 142.6; MS (EI): m/z=248
chromatography (10% EtOAc-petroleum ether) followed by
recrystallization (Et O-petroleum ether) gave a pale yellow
solid; mp 908C [Lit. 90–918C]. IR (KBr): n=1625, 2949,
3
3
8
1
79
(
M, Br), 246 (M, Br).
2
[
19]
À1
1
014, 3064, cm ; H NMR (CDCl , 250 MHz): d=4.00 (s, 2-Amino-4’-Chlorobiphenyl (4)
3
H), 7.17 (d, 1H, J=8.9 Hz), 7.35–7.49 (m, 3H), 7.53–7.57
To a solution of 4-chloro-2’-nitrobiphenyl 3e (211 mg,
0.91 mmol) in EtOH (3 mL) was added Fe powder (154 mg,
.75 mmol), NH Cl (29 mg, 0.54 mmol) and H O (1 mL).
(
m, 2H), 7.77 (dd, 1H, J=2.5, 8.9 Hz), 8.09 (d, 1H, J=
13
2
1
2
.4 Hz); C NMR (CDCl , 50 MHz): d=56.6, 113.9, 124.0,
3
2
4
2
26.7, 127.8, 129.0, 132.5, 133.8, 138.3, 152.2; MS (EI): m/z=
29 (M).
The resulting mixture was stirred for 1 h at 858C, then,
cooled to room temperature, extracted with CH Cl (3ꢃ)
2
2
4-Methoxy-2’-nitrobiphenyl (3d): Purification by flash
and dried over MgSO4. Filtration over
a microfilter
chromatography (5% EtOAc-petroleum ether) gave
yellow solid; mp 628C [Lit. 62–648C]. IR (KBr): n=1611,
2
(
a
[20]
(0.45 mm) and concentration under reduced pressure gave 4
as a pale yellow solid which was used in the next step with-
À1
1
844, 2920, 3010 cm ; H NMR (CDCl , 250 MHz): d=3.85
3
out further purification; yiled: 176 mg (96%); mp 458C. IR
s, 3H), 6.96 (dt, 2H, J=3.1, 8.8 Hz), 7.26 (dt, 2H, J=2.8,
.9 Hz), 7.41–7.48 (m, 2H), 7.56–7.62 (m, 1H), 7.80 (dd, 1H,
À1
(
KBr): n=1482, 1615, 2925, 3028, 3063, 3376, 3462 cm ;
8
1
H NMR (CDCl , 250 MHz): d=3.70 (br s, 2H), 6.77 (dm,
13
3
J=1.8, 8.6 Hz). C NMR (CDCl , 75 MHz): d=55.3, 114.2,
3
1
H, J=7.9 Hz), 6.84 (dt, 1H, J=1.2, 7.5 Hz), 7.10 (dm, 1H,
1
24.0, 127.7, 129.1, 129.4, 131.9, 132.1, 135.8, 149.4, 159.7;
MS (EI): m/z=229 (M).
-Chloro-2’-nitrobiphenyl (3e): Purification by flash chro-
matography (5% EtOAc-petroleum ether) gave a yellow
13
J=7.5 Hz), 7.17–7.21 (m, 1H), 7.42 (s, 4H); C NMR
(
CDCl , 75 MHz): d=124.2, 128.5, 128.9, 129.2, 131.8, 132.5,
3
35
4
1
34.4, 135.2, 149.0; MS (EI): m/z=203 (M, Cl), 205 (M,
37
Cl), 168 (MÀHCl).
[21]
solid; mp 648C [Lit.
2
2
618C]. IR (KBr): n=1530, 1609,
À1
1
866, 3068 cm ; H NMR (CDCl , 250 MHz): d=7.25 (dm,
3
ꢀ
Boscalid (5)
H, J=8.7 Hz), 7.41 (dm, 2H, J=8.7 Hz), 7.51 (app dt, 1H,
J=1.6, 8.1 Hz), 7.62 (app dt, 1H, J=1.4, 7.5 Hz), 7.88 (dd,
A solution of chloronicotinic acid (210 mg, 1.34 mmol) in
benzene (7 mL) was treated with (COCl)2 (0.23 mL,
2.68 mmol) and two drops of DMF. After 1 h of stirring at
room temperature, the resulting mixture was concentrated
under reduced pressure and dissolved in THF (5 mL). To
this mixture was added a solution of aniline (170 mg,
1
3
1
1
H, J=1.2, 7.9 Hz); C NMR (CDCl , 75 MHz): d=124.2,
3
28.5, 128.9, 129.2, 131.8, 132.5, 134.4, 135.2, 149.0; MS (EI):
35
37
m/z=233 (M, Cl), 235 (M, Cl), 197 (MÀCl).
-Carboxymethyl-2’-nitrobiphenyl (3f): Purification by
flash chromatography (10% EtOAc-petroleum ether) gave a
white solid; mp 1448C [Lit.
1
2
4
[
22]
145–1478C]. IR (KBr): n=
0.84 mmol) in THF (5 mL) followed by Et N (0.23 mL,
3
À1
1
609, 1718, 2952, 3002, 3072 cm ; H NMR (CDCl3,
1.68 mmol). The reaction mixture was stirred for 1 h at
room temperature and concentrated under vacuum. Purifi-
cation by flash chromatography (40% EtOAc-petroleum
ether) gave 5 as a white solid; yield: 270 mg (94%); mp
1438C. IR (KBr): n=1652, 2850, 3023, 3171, 3254,
50 MHz): d=3.95 (s, 3H), 7.61–7.66 (m, 1H), 7.68 (d, 2H,
J=8.3 Hz), 7.92–7.95 (m, 1H), 8.14 (d, 2H, J=8.3 Hz),
1
3
8
.21–8.25 (m, 1H), 8.46 (app t, 1H, J=2.0 Hz); C NMR
(
CDCl , 50 MHz): d=50.2, 122.0, 122.8, 127.1, 129.9, 130.1,
3
À1
1
130.4, 133.1, 141.6, 142.8, 148.7, 166.5; MS (EI): m/z=257
3288 cm ; H NMR (CDCl , 250 MHz): d=7.28–7.48 (m,
3
(
M), 226 (MÀOCH ).
8H), 8.10 (dd, 1H, J=2.0, 7.7 Hz), 8.17 (br s, 1H), 8.39 (d,
3
1
3
3
,4-Dimethoxy-3’-trifluoromethylbiphenyl (3g): Purifica-
1H, J=8.7 Hz), 8.42 (dd, 1H, J=2.0, 4.8 Hz); C NMR
(CDCl , 75 MHz): d=122.1, 122.8, 125.3, 128.8, 129.2, 130.2,
tion by flash chromatography (10% EtOAc-petroleum
3
ether) gave a pale yellow oil. IR (neat): n=2838, 2939,
130.7, 131.0, 132.2, 134.2, 134.4, 136.2, 140.0, 146.6, 151.2,
À1
1
3
3
1
7
002 cm ; H NMR (CDCl , 250 MHz): d=3.94 (s, 3H),
162.5; HR-MS (electrospray): m/z=365.0202, calcd. for
3
+
.97 (s, 3H), 6.97 (d, 1H, J=6.9 Hz), 7.09 (d, 1H, J=
.9 Hz), 7.16 (dd, 1H, J=1.6, 6.9 Hz), 7.50–7.58 (m, 2H),
.73 (d, 1H, J=6.0 Hz), 7.79 (s, 1H); MS (EI): m/z=282
C
18
H N
12
2
ONaCl
2
(M+Na ): 365.0218.
(
M); HR-MS (electrospray): m/z=305.0768, calcd. for
+
C H O F Na (M+Na ): 305.0765.
Acknowledgements
15
13
2 3
4-Methoxy-4’-isopropylbiphenyl (3i): Purification by flash
chromatography (2% EtOAc-petroleum ether) gave a white
This work was supported by the “Universitꢀ de Bordeaux”
and the “Centre National de la Recherche Scientifique
(CNRS).” Evonik Degussa GmbH, Business Line Catalysts
solid; mp 958C. IR (KBr): n=1497, 1605, 2834, 2868, 2961,
À1
1
2
996, 3028 cm ; H NMR (CDCl , 250 MHz): d=1.33 (d,
3
654
asc.wiley-vch.de
ꢂ 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Adv. Synth. Catal. 2009, 351, 649 – 655

Improved Suzuki–Miyaura Reactions of Aryldiazonium Salts with Boronic Acids
UPDATES
is gratefully acknowledged for the gift of Pd/C catalysts. We
thank M. Olivier Brugier (Universitꢀ de Montpellier, UMR
Geosciences/Analytical Platform AETE) for ICP-MS analy-
ses. We also aknowledge Mrs Odile Babot, Mrs Marie-
Hꢀlꢁne Lescure, Mrs Isabelle Ly and Dr. Marion Zanese
41, 6721–6724; i) M. L. Nelson, M. Y. Ismail, L. McIn-
tyre, B. Bhatia, P. Viski, P. Hawkins, G. Rennie, D. An-
dorsky, D. Messersmith, K. Stapleton, J. Dumornay, P.
Sheahan, A. K. Verma, T. Warchol, S. B. Levy, J. Org.
Chem. 2003, 68, 5838–5851; j) C.-Y. Liu, A. Gavryush-
in, P. Knochel, Chem. Asian J. 2007, 2, 1020–1030;
k) J. T. Kuethe, Karla. G. Childers, Adv. Synth. Catal.
(
University of Bordeaux) for helpful assistance.
2
008, 350, 1577–1586.
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Adv. Synth. Catal. 2009, 351, 649 – 655
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asc.wiley-vch.de
655