Palladium-catalyzed cross-coupling of trimethoxysilylbenzene with aryl bromides and chlorides using phosphite ligands

Article abstract of DOI:10.1016/j.tetlet.2006.10.017

Phosphites were employed as ligands in palladium-catalyzed Hiyama coupling reactions. The optimized reaction conditions were equimolar amounts (5 mol % each) of Pd(acac)₂ and phosphite 1 in p-xylene at 80 °C with TBAF as an additive. This catalyst system exhibited high activities in the reactions with trimethoxysilylbenzene and aryl bromides that have electron-donating or electron-withdrawing groups. In the case of aryl chlorides, substrates possessing electron-withdrawing groups gave the coupled products in high yields.

Full text of DOI:10.1016/j.tetlet.2006.10.017

Tetrahedron Letters 47 (2006) 8673–8678
Palladium-catalyzed cross-coupling of trimethoxysilylbenzene
with aryl bromides and chlorides using phosphite ligands
Jinhun Ju,a Hyungoog Nam,a Hyun Min Jungb and Sunwoo Leea,*
aDepartment of Chemistry, Chonnam National University, 300 Yongbong-dong, Buk-gu, Gwangju 500-757, Republic of Korea
bAdvanced Materials Division, Korea Research Institute of Chemical Technology, 100 Jang-dong, Yuseong-gu,
Daejeon 305-600, Republic of Korea
Received 13 September 2006; revised 2 October 2006; accepted 5 October 2006
Abstract—Phosphites were employed as ligands in palladium-catalyzed Hiyama coupling reactions. The optimized reaction condi-
tions were equimolar amounts (5 mol % each) of Pd(acac)2 and phosphite 1 in p-xylene at 80 °C with TBAF as an additive. This
catalyst system exhibited high activities in the reactions with trimethoxysilylbenzene and aryl bromides that have electron-donating
or electron-withdrawing groups. In the case of aryl chlorides, substrates possessing electron-withdrawing groups gave the coupled
products in high yields.
Ó 2006 Elsevier Ltd. All rights reserved.
Palladium-catalyzed carbon–carbon bond formation
reactions are useful tools to construct molecules such
as materials and drugs in modern chemistry.1 In partic-
ular, for the formation of sp2 carbon and sp2 carbon
bonds, several types of cross-coupling reactions have
been developed based on the transmetallations of a vari-
ety of hard or soft organometallic nucleophiles such as
the Kumada,2 Negishi,3 Stille,4 Suzuki,5 Hiyama,6 Sono-
gashira,7 and other related couplings.8,9 Among them,
the Suzuki and the Stille reactions are the most studied
and utilized. However, they have several disadvantages
for practical organic synthesis. Stille coupling requires
a large excess of a toxic tin reagent and the removal of
the tin byproduct. By using boronic acids, the Suzuki
reaction allows the problems which stem from the
reagent toxicity to be solved, but boronic acids are diffi-
cult to synthesize and purify.10 Therefore, Hiyama cou-
pling reactions using organosilicon reagents have been
developed and utilized in organic synthesis. The organo-
silicon reagents used as reactants in Hiyama reactions
are available at low cost or are very easily prepared,
nontoxic, and are very stable to other functionalities
and to the reaction conditions.
In palladium-catalyzed coupling reactions, in order to
accomplish cross-coupling with a high efficiency, most
studies have focused on the development of suitable
ligands, for example, sterically bulky alkyl phos-
phines4c,5c,d,8f–h,9d,f,g,i or carbene-type ligands.5e,9d,e Re-
cently, there have been several reports on the
extension of these methods to aryl chlorides, which are
the most challenging substrates.1b,4c,5c–e,8f,h,9d,g How-
ever, alkyl phosphine ligands have a drawback from
the viewpoint of their practical application. They are
sensitive to oxygen and moisture, and so they require
an inert environment.4c,5d In addition, most of these li-
gands are not commercially available, and of those that
are, many are quite expensive. Although carbene-type li-
gands are more stable than alkyl phosphines, they must
be synthesized through multi-steps.5e
In contrast to the well-developed phosphine ligands,
phosphite ligands have received relatively little atten-
tion, despite the fact that phosphites have an advantage
in terms of their stability towards air and moisture.
There have been a few examples of the use of phosphites
as ligands in Hiyama cross-coupling reactions.6h,p On
the other hand, phosphites have been more widely used
as anti-oxidants in polymer chemistry than as ligands in
transition metal-catalyzed chemistry.11 They are com-
mercially available, very inexpensive and very stable.
Therefore, our attention was drawn to those of them,
which have sterically hindered groups (Fig. 1), so that
Keywords: Palladium; Phosphite; Organosilicon; Hiyama coupling;
Aryl bromides; Aryl chlorides.
*
Corresponding author. Tel.: +82 62 530 3385; fax: +82 62 530
3389; e-mail: sunwoo@chonnam.ac.kr
0040-4039/$ - see front matter Ó 2006 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tetlet.2006.10.017

8674
J. Ju et al. / Tetrahedron Letters 47 (2006) 8673–8678
tBu
tBu
O P
tBu
O
O
O
O
Me
P
O
Me
tBu
tBu
O
O
tBu
tBu
P
O
tBu
1
tBu
tBu
tBu
O
O
P O
tBu
tBu
O P
tBu
3
O
O
2
Figure 1. Phosphite ligands.
they can be employed as ligands. Herein, we report on
the subject of Hiyama cross-coupling reactions using
phosphite ligands.
seen from Table 2, the use of p-xylene as a solvent in
the place of NMP led to a dramatically increased yield
of the coupled product (entry 5). Other kinds of solvent,
such as DMF, 1,4-dioxane and toluene, were not suit-
able for the coupling reactions. The reactions using
phosphites 2 and 3 in p-xylene instead of NMP resulted
in yields of 82% and 75%, respectively (entries 6 and 7).
Among the palladium sources tested, Pd(acac)2 was the
best. When Pd(OAc)2 or [PdCl(allyl)]2 were used, the
coupled product was obtained in a very low yield
(entries 8 and 9). Pd2(dba)3 and Pd(CH3CN)2Cl2
showed moderate yields (entries 10 and 11). These results
implied that the oxidation state of the palladium source
was not the key factor in the reactions. The most suit-
able palladium/ligand molar ratio was 1:1, even though
phosphite 1 has two phosphorus atoms (entries 12 and
13). When the amount of catalyst used was less than
1 mol %, very low yields of the cross-coupled adducts
were obtained (entries 16 and 17). In addition, the use
of TBACl, TBABr or CsF to replace TBAF as an addi-
tive resulted in no coupled product being obtained (en-
tries 20–22). However, the use of an aqueous solution
of NaOH afforded the coupled product with a 76% yield
(entry 23). Masuda and co-workers reportedly used the
system of NaOH and phosphite, P(OiPr)3, in Hiyama
coupling reactions.6h
In order to investigate the activity of the ligands in
Hiyama reactions, we first carried out the coupling reac-
tions of 4-bromotoluene and trimethoxysilylbenzene in
the presence of a palladium catalyst with a variety of
phosphite and phosphine ligands. Considering the
availability of the many kinds of silane compounds, we
chose aryltrialkoxysilane.6d–n The phosphite ligands
were purchased from Adeka and used without further
purification.12 Table 1 summarizes our results from the
screening of the ligands. Among the phosphite ligands
examined, phosphite 1 was found to be the best, giving
the desired product in a 68% yield (entry 1). However,
phosphite 3, which has shown good activities in several
palladium-catalyzed coupling reactions, gave a lower
yield than phosphite 1 (entry 3).13 Arylphosphine
ligands including chelating type ones gave yields of less
than 60% yield, and the yield of the coupled product was
found to decrease with increasing steric hindrance of the
ligand. DeShong and co-workers reported similar
results.6d
These results encouraged us to further optimize the reac-
tion conditions in the presence of phosphite 1 by using
different solvents and palladium sources as well as
changing the ratio of ligand to palladium. As can be
We compared the reaction rates of phosphite ligands
1, 2 and 3 in the Hiyama cross-coupling reactions.
Table 1. Screening of ligands for the reaction of 4-bromotoluene and trimethoxysilylbenzenea
5% Pd(acac)2/Ligand
(MeO)3Si
TBAF(2eq)
Me
Br
Me
NMP
80oC
Entry
Ligand
Yieldb (%)
Entry
Ligand
Yieldb (%)
1
2
3
4
1
68
57
59
55
5
6
7
8
dpped
PPh3
P(o-tol)3
P(Mes)3
48
60
55
43
2
3
dppfc
a Reaction conditions: 1.0 mmol aryl halide, 1.2 mmol PhSi(OMe)3, 3.0 ml solvent.
b The yield was determined by GC by comparison to an internal standard (naphthalene).
c 1,10-Bis(diphenylphosphino)ferrocene.
d 1,2-Bis(diphenylphosphino)ethane.

J. Ju et al. / Tetrahedron Letters 47 (2006) 8673–8678
8675
Table 2. Optimization of conditions for Hiyama coupling of 4-bromotoluene and trimethoxysilylbenzenea
Pd / Phosphite
(MeO)3Si
Additive
Solvent
+
Me
Br
Me
Entry
Palladium
Pd (mol %)
L
Pd/L
Solvent
Additive
Temperature (°C)
Time (h)
Yieldb (%)
1
2
3
4
5
6
7
8
Pd(acac)2
Pd(acac)2
Pd(acac)2
Pd(acac)2
Pd(acac)2
Pd(acac)2
Pd(acac)2
Pd(OAc)2
[PdCl(allyl)]2
Pd2(dba)3
Pd(CH3CN)2Cl2
Pd(acac)2
Pd(acac)2
Pd(acac)2
Pd(acac)2
Pd(acac)2
Pd(acac)2
Pd(acac)2
Pd(acac)2
Pd(acac)2
Pd(acac)2
Pd(acac)2
Pd(CH3CN)2Cl2
5
5
5
5
5
5
5
5
5
5
5
5
5
2.5
1
0.1
0.01
5
1
1
1
1
1
2
3
1
1
1
1
1
1
1
1
1
1
2
3
1
1
1
1
1/1
1/1
1/1
1/1
1/1
1/1
1/1
1/1
1/1
1/1
1/1
1/0.5
1/2
1/1
1/1
1/1
1/1
1/1
1/1
1/1
1/1
1/1
1/1
NMP
DMF
TBAF
TBAF
TBAF
TBAF
TBAF
TBAF
TBAF
TBAF
TBAF
TBAF
TBAF
TBAF
TBAF
TBAF
TBAF
TBAF
TBAF
TBAF
TBAF
TBACl
TBABr
CsF
80
80
80
80
80
80
80
80
80
80
80
80
80
80
80
140
140
80
80
80
80
80
80
4
4
4
4
4
4
4
4
4
4
4
4
4
6
8
12
12
4
68
70
76
76
99
82
75
11
10
63
65
85
56
95
60
8
<1
85
Dioxane
Toluene
p-Xylene
p-Xylene
p-Xylene
p-Xylene
p-Xylene
p-Xylene
p-Xylene
p-Xylene
p-Xylene
p-Xylene
p-Xylene
p-Xylene
p-Xylene
p-Xylene
p-Xylene
p-Xylene
p-Xylene
p-Xylene
Dioxane
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
5
5
5
5
4
8
8
8
75
NRc
NRc
NRc
76
5
NaOH
8
a Reaction conditions: 1.0 mmol aryl halide, 1.2 mmol PhSi(OMe)3, 3.0 ml solvent.
b The yield was determined by GC by a comparison to an internal standard (naphthalene).
c No reaction: only starting materials were appeared in GC.
after 2.5 h. The maximum yield obtained with this
ligand was 75%.
100
80
60
40
20
0
On the basis of these results, we next investigated the
scope of the Hiyama coupling reactions using phos-
phite 1 as the ligand for a series of aryl bromides and
chlorides possessing different steric and electronic prop-
erties. These studies showed that equimolar amounts of
Pd(acac)2 and phosphite 1 (5 mol % each) in p-xylene at
80 °C with TBAF as an additive formed the coupled
compound in a high yield in less than 4 h.
1
2
3
As shown in Table 3, the coupling reaction is tolerant of
functional groups in the case of aryl bromides. The reac-
tions with both electron-withdrawing and electron-
donating substituents gave the desired biaryl products
in moderate to excellent yields. Bromobenzene and aryl
bromides having alkyl substituents at the para position
showed almost quantitative yields (entries 1–3). Bromo-
naphthalene and aryl bromides with amino substituents
at the para position also gave the corresponding cross-
coupled products in excellent yields (entries 4 and 5).
The substrates with ortho mono substituents also
cross-coupled to afford the desired biaryls in high yields
(entry 6). However, the more hindered 2-phenylbromo-
benzene and 2,4,6-trimethylbromobenzene coupled to
give the corresponding biaryls in low yield (entries 7
and 8). 3-Methoxy, 4-methoxy, 4-nitro substituted aryl
0
1
2
3
4
5
Time (h)
Figure 2. Reaction profile for the Hiyama cross-coupling reaction of 4-
bromotoluene and trimethoxysilylbenzene using ligand 1 (j), 2 (d)
and 3 (m).
As shown in Figure 2, ligand 1 afforded the coupled
product with an almost quantitative yield within
4 h. Comparable catalytic activity could also be
obtained with ligand 2, although the yield did not
exceed 90% even after 8 h. Ligand 3 required an
induction period and showed only 10% yield even

8676
J. Ju et al. / Tetrahedron Letters 47 (2006) 8673–8678
Table 3. Hiyama cross-coupling reactions with arylbromides and trimethoxysilylbenzene by catalyst 1a
5% Pd(acac)2/phosphite 1
Br
(MeO)3Si
TBAF(2eq)
+
p-xylene
80 oC
R
R
Entry
1
ArBr
Conversion (%)
100
Yieldb (%)
98
Entry
ArBr
Conversion (%)
100
Yieldb (%)
70
Br
MeO
Br
Br
9
Br
Br
2
3
100
100
99
98
10
11
100
100
77
83
Me
tBu
MeO
Br
O2N
Me
Br
Br
4
100
100
97
95
98
95
32
9
12
13
14
15
16
100
100
66
87
93
35
11
25
O
Br
Br
5
MeO
Me2N
Me
O
Br
f 6
N
Br
Me
Me
Br
Br
7
43
38
N
S
Me
Me
Br
8
15
32
Br
Ph
a Reaction conditions: 1.0 equiv of aryl halide, 1.2 equiv of PhSi(OMe)3, 5 mol % 1, 5 mol % Pd(acac)2, 2.0 equiv of TBAF, p-xylene (0.3 M).
b The isolated yields of compounds are an average of at least two runs. All compounds are characterized by comparison of 1H and 13C NMR spectra
with authentic samples or literature data.
bromides reacted to give the products in moderate yields
(entries 9–11). Carbonyl group substituted aryl bro-
mides showed good yields (entries 12 and 13). We found
that this catalyst/ligand system was not suitable for the
coupling of heteroaryl halide such as bromopyridines
and bromothiophenes. 2-Bromopyridine gave the cou-
pled product in a 35% yield and 3-bromopyridine
showed a yield of 11%. 2-Bromothiophene also gave
a yield of 25% (entries 14–16). Their yields were
little improved when the reactions were carried out at
120 °C.
electron-donating ones (entries 5–7). There were only a
few examples that moderate yields were observed with
aryl chlorides and aryltrialkoxysilanes in the Hiyama
cross-coupling reactions.6f,j,n
In conclusion, we showed that phosphite ligand 1 co-
ordinated catalyst exhibited the highest activities in
the palladium-catalyzed Hiyama coupling reactions.
To the best of our knowledge, phosphite 1 has never before
been used as a ligand in palladium-catalyzed cross-cou-
pling reactions. This is the first example in which phos-
phite 1 is used as a ligand. We found that the palladium
source, solvent and additive are also important to obtain
the coupled products in high yields. This catalytic sys-
tem can be used without resorting to dry reagents or
anaerobic conditions. In addition, considering the very
low cost of arylphosphites as ligands and the stability
of arylsiloxanes as substrates, this method should be
of a great value as a convenient route to functionalized
unsymmetrical biaryl compounds.
Encouraged by the above success, we extended our work
to aryl chlorides, which are more challenging substrates.
However, as shown in Table 4, 4-chloro acetophenone
and 4-chlorophenyl acetic acid coupled to afford the cor-
responding biaryl products in good yields (entries 1 and
4). As in the case of the arylbromides, Pd(acac)2 was the
best palladium source. Low yields were observed with
aryl chlorides having electron neutral substituents or

J. Ju et al. / Tetrahedron Letters 47 (2006) 8673–8678
8677
Table 4. Hiyama cross-coupling reactions with arylchlorides and trimethoxysilylbenzene by catalyst 1a
5% Pd(acac)2/phosphite 1
Cl
(MeO)3Si
TBAF(2eq)
+
p-xylene
120 oC
R
R
Entry
1
ArCl
Conversion (%)
100
Yieldc (%)
93
Entry
ArCl
Conversion (%)
35
Yieldc (%)
Cl
5
27
25
Cl
Cl
2a
3b
4
42
11
32
7
6
7
34
18
Me
O
OMe
Cl
HO
100
78
15
O
Cl
Me
a Pd2(dba)3.
b Pd(OAc)2.
c The isolated yields of compounds are an average of at least two runs. All compounds are characterized by comparison of 1H and 13C NMR spectra
with authentic samples or literature data.
Coupling Reactions; de Meijere, A., Diederich, F., Eds.;
Wiley-VCH: Weinheim, 2004; Vol. 2, pp 163–216; Based
on silicon compound aryl trialkoxysilanes; (e) Mowery,
M. E.; DeShong, P. Org. Lett. 1999, 1, 2137–2140; (f) Lee,
H. M.; Nolan, S. P. Org. Lett. 2000, 2, 2053–2055;
(g) Correia, R.; DeShong, P. J. Org. Chem. 2001, 66,
7159–7165; (h) Murata, M.; Shimazaki, R.; Watanabe, S.;
Masuda, Y. Synthesis 2001, 2231–2233; (i) McElroy, W.
T.; DeShong, P. Org. Lett. 2003, 5, 4779–4782; (j) Wolf,
C.; Lerebours, R.; Tanzini, E. H. Synthesis 2003, 2069–
2073; (k) Seganish, W. M.; DeShong, P. J. Org. Chem.
2004, 69, 6790–6795; (l) Wolf, C.; Lerebours, R. Org. Lett.
2004, 6, 1147–1150; (m) Li, J.-H.; Deng, C.-L.; Liu, W.-J.;
Xie, Y.-X. Synthesis 2005, 3039–3044; (n) Murata, M.;
Yoshida, S.; Nirei, S.-i.; Watanabe, S.; Masuda, Y. Synlett
2006, 118–120; aryl silatranes; (o) Riggleman, S.; Desh-
ong, P. J. Org. Chem. 2003, 68, 8106–8109; aryl trialkyl
silanes; (p) Hatanaka, Y.; Hiyama, T. J. Org. Chem. 1988,
53, 918–920; (q) Pierrat, P.; Gros, P.; Fort, Y. Org. Lett. 2005,
7, 697–700; (r) Jayanth, E. T.; Jeganmohan, M.; Ching,
C.-H. Org. Lett. 2005, 7, 2921–2924; organochlorosilanes;
(s) Gouda, K.-i.; Hagiwara, E.; Hatanaka, Y.; Hiyama, T.
J. Org. Chem. 1996, 61, 7232–7233; silanols; (t) Denmark,
S. E.; Sweis, R. F. Org. Lett. 2002, 4, 3771–3774;
(u) Hirabayashi, K.; Mori, A.; Kawashima, J.; Suguro,
M.; Nishihara, Y.; Hiyama, T. J. Org. Chem. 2000, 65,
5342–5349; (v) Denmark, S. E.; Baird, J. D. Org. Lett.
2004, 6, 3649–3652; (w) Denmark, S. E.; Ober, M. H. Org.
Lett. 2003, 5, 1357–1360; triallyl(aryl)silanes; (x) Sahoo,
A. K.; Oda, T.; Nakao, Y.; Hiyama, T. Adv. Synth. Catal.
2004, 346, 1715–1727; allyldialkylsilanes; (y) Nokami, T.;
Tomida, Y.; Kamei, T.; Itami, K.; Yoshida, J.-i. Org. Lett.
2006, 8, 729–731; (z) Seganish, W. M.; DeShong, P.
J. Org. Chem. 2004, 69, 1137–1143; bis(catechol)silicate;
Mowery, M. E.; DeShong, P. J. Org. Chem. 1999, 64,
3266–3270.
Acknowledgement
This work was supported by the Korea Research Foun-
dation Grant funded by the Korean Government
(MOEHRD, Basic Research Promotion Fund) (KRF-
2005-003-C00107).
References and notes
1. For leading references, see: (a) Negishi, E. Handbook of
Organopalladium Chemistry for Organic Synthesis; Wiely:
New York, 2002; (b) Littke, A. F.; Fu, G. C. Angew.
Chem., Int. Ed. 2002, 41, 4176–4211.
2. (a) Tamao, K.; Sumitani, K.; Kumada, M. J. Am. Chem.
Soc. 1972, 94, 4374–4376; (b) Phan, N. T. S.; Brown, D.
H.; Styring, P. Green Chem. 2004, 6, 526–532.
3. (a) Negishi, E. Acc. Chem. Res. 1982, 15, 340–348; (b)
Negishi, E.; Anastasia, L. Chem. Rev. 2003, 103, 1979–
2018.
4. (a) Milstein, D.; Stille, J. K. J. Am Chem. Soc. 1978, 100,
3636–3638; (b) Stille, J. K. Angew. Chem., Int. Ed. Engl.
1986, 25, 508–524; (c) Littke, A. F.; Fu, G. C. Angew.
Chem., Int. Ed. 1999, 38, 2411–2413; (d) Garcia-Martinez,
J. C.; Lezutekong, R.; Crooks, R. M. J. Am. Chem. Soc.
2005, 127, 5097–5103.
5. (a) Miyaura, N.; Suzuki, A. Chem. Rev. 1995, 95, 2457–
2483; (b) Suzuki, A. J. Organomet. Chem. 1999, 576, 147–
168; (c) Wolfe, J. P.; Singer, R. A.; Yang, B. H.;
Buchwald, S. L. J. Am. Chem. Soc. 1999, 121, 9550–
9561; (d) Littke, A. F.; Dai, C.; Fu, G. C. J. Am. Chem.
Soc. 2000, 122, 4020–4028; (e) Navarro, O.; Oonishi, Y.;
Kelly, R. A.; Stevens, E. E.; Briel, O.; Nolan, S. P. J.
Organomet. Chem. 2004, 689, 3722–3727.
6. Review: (a) Hiyama, T. In Metal-catalyzed Cross-coupling
Reactions; Diederich, F., Stang, J., Eds.; Wiley-VCH:
Weinheim, 1998; pp 421–453; (b) Hiyama, T.; Shirakawa,
E. Top. Curr. Chem. 2002, 219, 61–85; (c) Denmark, S. E.;
Sweis, R. F. Acc. Chem. Res. 2002, 35, 835–845; (d)
Denmark, S. E.; Sweis, R. F. In Metal-Catalyzed Cross-
7. (a) Sonogashira, K.; Tohda, Y.; Hagihara, N. Tetra-
hedron Lett. 1975, 16, 4467–4470; (b) Sonogashira, K.
J. Organomet. Chem. 2002, 653, 46–49; (c) Beletskaya, I.
P.; Cheprakov, A. V. Chem. Rev. 2000, 100, 3009–
3066.

8678
J. Ju et al. / Tetrahedron Letters 47 (2006) 8673–8678
8. Hartwig–Buchwald amination; (a) Guram, A. S.; Rennels,
1478; (d) Lee, S.; Hartwig, J. F. J. Org. Chem. 2001, 66,
3402–3415; (e) Lee, S.; Beare, N. A.; Hartwig, J. F. J. Am.
Chem. Soc. 2001, 123, 8410–8411; (f) Jorgensen, M.; Lee,
S.; Liu, X.; Wolkowski, J. P.; Hartwig, J. F. J. Am. Chem.
Soc. 2002, 124, 12557–12565; (g) Beare, N. A.; Hartwig,
J. F. J. Org. Chem. 2002, 67, 541–555; (h) Culkin, D. A.;
Hartwig, J. F. Acc. Chem. Res. 2003, 36, 234–245;
(i) Hama, T.; Culkin, D. A.; Hartwig, J. F. J. Am. Chem.
Soc. 2006, 128, 4976–4985.
R. A.; Buchwald, S. L. Angew. Chem., Int. Ed. Engl. 1995,
34, 1348–1350; (b) Louie, J.; Hartwig, J. F. Tetrahedron
Lett. 1995, 36, 3609–3612; (c) Wolfe, J. P.; Wagaw, S.;
Buchwald, S. L. J. Am. Chem. Soc. 1996, 118, 7215–7216;
(d) Driver, M. S.; Hartwig, J. F. J. Am. Chem. Soc. 1996,
118, 7217–7218; (e) Driver, M. S.; Hartwig, J. F. J. Am.
Chem. Soc. 1997, 119, 8232–8245; (f) Hamann, B. C.;
Hartwig, J. F. J. Am. Chem. Soc. 1998, 120, 7369–7370;
(g) Hartwig, J. F.; Kawatsura, M.; Hauck, S. I.; Shaugh-
nessy, K. H.; Alcazar-Roman, L. M. J. Org. Chem. 1999,
64, 5575–5580; (h) Wolfe, J. P.; Buchwald, S. L. Angew.
Chem., Int. Ed. 1999, 38, 2413–2416; (i) Yin, J.; Buchwald,
S. L. J. Am. Chem. Soc. 2002, 124, 6043–6048;
(j) Schlummer, B.; Scholz, U. Synth Catal. 2004, 346,
1599–1626.
10. Hall, D. G. Boronic Acids: Preparation and Applications in
Organic Synthesis and Medicine; Wiley-VCH: Weinheim,
2005; pp 1–99.
11. Yamazaki, T.; Sguchi, T. J. Polym. Sci. Part A: Polym.
Chem. 2000, 38, 3092–3099.
12. ADK trade name; 1 (PEP-36Ò), 2 (PEP-24GÒ), 3 (2112Ò),
all phosphites were checked by NMR. 31P NMR 1: d
123.66, 2: d 117.70, 3: d 131.05.
9. Hartwig–Buchwald arylation of carbonyl compounds;
(a) Palucki, M.; Buchwald, S. L. J. Am. Chem. Soc.
1997, 119, 11108–11109; (b) Hamann, B. C.; Hartwig, J. F.
J. Am. Chem. Soc. 1997, 119, 12382–12383; (c) Kawatsura,
M.; Hartwig, J. F. J. Am. Chem. Soc. 1999, 121, 1473–
13. (a) Zapf, A.; Beller, M. Chem. Eur. J. 2000, 6, 1830–1833;
(b) Bedford, R. B.; Hazelwood, S. L.; Limmert, M. E.;
Albisson, A.; Draper, S. M.; Scully, P. N.; Coles, S. J.;
Hursthouse, M. B. Chem. Eur. J. 2003, 9, 3216–3227.