Palladium-catalyzed monoselective halogenation of C-H bonds: Efficient access to halogenated arylpyrimidines using calcium halides

Article abstract of DOI:10.1002/adsc.200900778

A wide variety of ortho-halogenated arylpyrimidines were prepared with high monoselectivity and functional-group tolerance by using calcium halides as crucial halogenating agents and cupric trifluoroacetate as oxidant in the presence of air.

Full text of DOI:10.1002/adsc.200900778

COMMUNICATIONS
DOI: 10.1002/adsc.200900778
À
Palladium-Catalyzed Monoselective Halogenation of C H Bonds:
Efficient Access to Halogenated Arylpyrimidines using Calcium
Halides
Bingrui Song,a Xiaojian Zheng,a Jun Mo,a and Bin Xua,*
a
Department of Chemistry, Shanghai University, 99 Shangda Road, Shanghai 200444, Peopleꢀs Republic of China
Fax : (+86)-21-6613-2797; phone: (+86)-21-6613-2065; e-mail: xubin@shu.edu.cn
Received: November 9, 2009; Published online: February 5, 2010
Supporting information for this article is available on the WWW under
http://dx.doi.org/10.1002/adsc.200900778.
Abstract: A wide variety of ortho-halogenated aryl-
pyrimidines were prepared with high monoselectivi-
ty and functional-group tolerance by using calcium
halides as crucial halogenating agents and cupric
trifluoroacetate as oxidant in the presence of air.
ly needed to reach a high yield and monoselectivity.[6]
Thus, developing highly efficient and selective catalyt-
ic systems for C H halogenation with diverse direct-
À
ing groups and expanding the substrate scope to elec-
tron-deficient substrates remain a challenge.[9]
Given the importance of pyrimidine derivatives in
materials and medicinal chemistry,[10] the development
of readily available halogenated arylpyrimidines in a
monoselective manner would find significant use in
the preparation of this class of molecules.[1] To contin-
ue our research interest aiming at the efficient con-
struction of nitrogen-containing heterocycles,[11] we
À
Keywords: arylpyrimidines; C H activation; elec-
tron-deficient substrates; halogenation; palladium;
selectivity
À
herein report a highly ortho-monoselective C H halo-
Aryl or heteroaryl halides, as important starting mate- genation of arylpyrimidines, using calcium halides as
rials to construct complex structures and notable crucial halogenating agents and cupric trifluoroace-
structural motifs in natural products and manufac- tate as oxidant in the presence air (Scheme 1).
tured drugs,[1] were traditionally obtained by electro-
We initiated our study with electron-deficient sub-
philic aromatic substitution[2] or through directed strate 1a in the presence of CuCl2 or NCS,[6f] how-
ortho-lithiation.[3] The drawbacks of some of these ever, low yield and monoselectivity of 2a were ob-
methods lie in their low selectivity or tedious and served (Table 1, entries 1–3). Use of CaCl2 and
[6e]
somewhat dangerous procedures.
CuACTHNGUTRE(NNUG OTFA)2 in acetic acid led to improvements of
Considerable progress has been made during the both yield and monoselectivity (entry 6 vs. entries 3–
À
past decades in the C H activation reaction directed 5), although a long reaction time was needed to reach
by functional groups.[4,5] Recently, ortho-halogenated completion. To our delight, CaCl2 (6.0 equiv.) and
arenes were selectively synthesized by metal-cata- Cu
lyzed halogenation of C H bonds. High yields and choice in the presence of Pd
monoselectivities among them could be achieved with HOAc, and gave ortho-mono-chlorinated product 2a
N
[6]
À
N
assistance of some directing groups, including am- in 89% yield in 5 h (entry 7). Further screens concern-
ACHTUNGTRENNUNG
ides,[6a,e] pyridines,[6c,f,g] carboxylic acids,[6d] and oxazol- ing oxidants (entries 8–11), chlorinating agents (en-
ACHTUNGTRENNUNG
ines.[6h] Generally, substrates with electron-donating tries 12–14), palladium resources (entries 15 and 16)
properties will give high monoselectivity and particu-
larly for those substrates with ortho- or meta-substitu-
tion in the aryl ring.[6d,f,g] However, only few examples
involving electron-deficient substrates were well
[7]
À
documented for the C H activation reaction and
even less examples were successfully investigated
using pyrimidine as directing group,[5a,d–f,i] which may
be due to the formation of a double metalation com-
plex.[8] Furthermore, a long reaction time was normal- Scheme 1. Monoselective halogenation of arylpyrimidines.
Adv. Synth. Catal. 2010, 352, 329 – 335
ꢁ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
329

Bingrui Song et al.
COMMUNICATIONS
À
Table 1. Reaction optimization for the C H halogenation.
Entry
Oxidant (equiv.)
MClx (equiv.)
Solvent
Time [h]
Conversion [%]
Yield [%][a] of 2a/3a
1[b]
2[b]
3[c]
4
5
6
7
8
9
10
11
12
13
14
15[d]
16[e]
17
18
19[f]
/
/
NCS (1.2)
NCS (1.2)
CuCl2 (2.0)
CuCl2 (2.0)
NCS (2.0)
CaCl2 (2.0)
CaCl2 (6.0)
CaCl2 (6.0)
CaCl2 (6.0)
CaCl2 (6.0)
CaCl2 (6.0)
CuCl2 (6.0)
NaCl (6.0)
LiCl (6.0)
HOAc
MeCN
DCE
12
72
72
48
24
48
5
48
72
72
72
4
100
90
65
80
100
85
100
58
0
63
50
100
81
95
100
100
100
0
68/27
66/24
35/6
58/21
60/29
74/11
89/6
50/4
0
53/2
47/2
74/24
61/21
65/32
76/15
54/26
76/16
0/0
Cu
Cu
Cu
Cu
Cu
Cu
G
R
E
ACHTUNGTRENNUNG
N
N
HOAc
HOAc
HOAc
HOAc
HOAc
HOAc
HOAc
HOAc
HOAc
HOAc
HOAc
HOAc
HOAc
HOAc
HOAc
HOAc
BQ (1.0)
K2S2O8 (1.0)
Oxone (1.0)
Cu
Cu
Cu
Cu
Cu
Cu
/
R
N
N
E
N
R
48
48
6
CaCl2 (6.0)
CaCl2 (6.0)
CaCl2 (6.0)
CaCl2 (6.0)
CaCl2 (6.0)
5
40
48
2
Cu
A
100
50/50
[a]
Isolated yield. BQ=benzoquinone, Cu
cinimide.
208C, under N2.
ACHTUNGERTN(NUNG OTFA)2 =cupric trifluoroacetate, DCE=1,2-dichloroethane, NCS=N-chlorosuc-
[b]
[c]
[d]
[e]
[f]
Pd
PdCl2 (5 mol%) was used.
Pd(dba)2 (5 mol%) was used.
Under O2.
ACHTUNGTRENNUNG(OAc)2 (10 mol%) was used at 908C under N2.
ACHTUNGTRENNUNG
and the catalytic amount of CuACTHNUTRGEN(UNG OTFA)2 (entry 17) should be noted that the strongly electron-deficient
gave no better results. When the reaction was con- nitro group-containing substrate 1j, which was rarely
À
ducted in the absence of Cu
achieved (entry 18), while low monoselectivity was afford monochlorinated product 2j selectively in 74%
G
obtained with the reaction under oxygen instead of yield (entry 10). However, for those electron-rich sub-
air (entry 19).
strates without ortho- or meta-substitution on the aryl
The broad substrate scope is summarized in Table 2 ring, an important issue arose. The reaction was less
and most of the reactions could be finished within selective under the conditions employed in Table 2,
several hours. In general, this reaction was compatible giving rise to the ortho-dichlorinated products 3q and
in high yields and excellent monoselectivities with 3r exclusively (entries 17 and 18), and thus hampered
functionalized substrates bearing para- (entries 1–6), its wider application in organic synthesis.
meta- (entries 7–10), ortho- (entries 11 and 12), and
Screening reactions were next carried out to settle
poly-substitutions (entries 13–15) on the aryl ring, as this problem (Table 3) and we found that high mono-
well as a pyrimidine-directed naphthalene derivative selectivity and yield could be achieved by addition of
(entry 16). Arylpyrimidines containing both electron- acetic anhydride as co-solvent (Table 3, entry 6). This
À
donating (entries 7, 8 and entries 11–15) and electron- C H halogenation was accelerated by oxygen with
withdrawing groups (entries 1–4 and entries 9 and 10) low selectivity (entry 10), and retarded dramatically
afforded monoselective products predominately. It in a nitrogen atmosphere (entry 11). When the reac-
330
asc.wiley-vch.de
ꢁ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Adv. Synth. Catal. 2010, 352, 329 – 335

À
Palladium-Catalyzed Monoselective Halogenation of C H Bonds
[a]
À
Table 2. Highly selective C H chlorination of arylpyrimidines.
Entry
Substrate
No.: R
Product
No.
Time [h]
Yield [%][b] of mono/di
1
2
3
4
5
6
7
8
1a: 4-CO2Et
1b: 4-CF3
1c: 4-Ac
1d: 4-OTs
1e: 4-Cl
2a
2b
2c
2d
2e
2f
2g
2h
2i
5
6
5
4
5
4
1
1
89/6
89/4
82/0
91/3
96/4
82/9
86/0
91/0
92/8
74/0
80/0
89/0
1f: 4-F
1g: 3-Me
1h: 3-OMe
1i: 3-CHO
1j: 3-NO2
1k: 2-Me
1l: 2-OMe
9
6
24
1
10[c]
11
12
2j
2k
2l
12
13
14
1m
2m
3
85/0
72/0
1n
2n
14
15
1o
2o
12
89/0
16
17
1p
1q
1r
2p
3q
3r
3
7
6
93/0
0/96
0/97
18
[a]
Conditions: PdACHTUNGTRENNUNG(OAc)2 (5 mol%), CuACHTUNTGRNE(NUGN OTFA)2 (1 equiv.), CaCl2 (4.0–8.0 equiv.) in HOAc, 1108C, under air.
[b]
[c]
Isolated yield.
Pd(OAc)2 (10 mol%) was used with conversion of 76%.
ACHTUNGTRENNUNG
À
tion was conducted in acetic acid or acetic anhydride
alone, dichlorinated product 3r was obtained in 97% tron-rich substrates with less steric hindrance on the
The results of C H halogenation for those elec-
yield (entry 12) or the starting material 1r decom- aryl rings are summarized in Table 4. Substrates with-
posed during the reaction (entry 13).
out substituents (entry 1) or bearing electron-rich sub-
Adv. Synth. Catal. 2010, 352, 329 – 335
ꢁ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
asc.wiley-vch.de
331

Bingrui Song et al.
COMMUNICATIONS
Table 3. Optimization of conditions for 2-p-tolylpyrimidines.
Entry
Oxidant (equiv.)
MClx (equiv.)
Solvent
Time [h]
Conversion [%]
Yield [%][a] of 2r/3r
1[b]
/
/
NCS
NCS
HOAc
CH3CN
DCE
Dioxane
HOAc/Ac2O
HOAc/Ac2O
HOAc/Ac2O
HOAc/Ac2O
HOAc/Ac2O
HOAc/Ac2O
HOAc/Ac2O
HOAc
24
48
48
48
3
3
8
3
4.5
1.5
12
6
93
75
79
55
100
100
100
100
100
100
100
100
–
76/15
65/9
42/34
46/6
83/17
90/9
63/37
84/15
69/28
81/16
89/9
2[b,c]
3[c]
Cu
Cu
Cu
Cu
Cu
Cu
Cu
Cu
Cu
Cu
Cu
G
E
E
R
R
N
T
ACHTUNGTRENNUNG
CuCl2
CuCl2
CaCl2
CaCl2
CuCl2
CaCl2
CaCl2
CaCl2
CaCl2
CaCl2
CaCl2
4[d]
5[e]
6[e]
7[e]
8[e,f]
9[e,g]
10[e,h]
11[e,i]
12
ACHTUNGTRENNUNG
E
A
0/97
0/0
13[j]
Ac2O
3
[a]
Isolated yield.
1.05 equiv. of NCS was used.
At 908C.
At 1008C.
HOAc/Ac2O=1.2:1.
PdCl2 (5 mol%) was used.
PdACHTUNGTRENNUNG(dba)2 (5mol%) was used.
Under O2.
Under N2.
1r decomposed.
[b]
[c]
[d]
[e]
[f]
[g]
[h]
[i]
[j]
stituents at the para-position gave monochlorinated rule out the possible existence of a Pd
products in high yields (entries 2 and 3). In particular, ate during the reaction. Cu(OTFA)2 and air are used
high yields of ortho-mono-chlorinated products 2t[12] as co-oxidant to complete the catalytic cycle.
and 2u could be achieved selectively for dual phenyl- In summary, a palladium-catalyzed direct ortho-C
ACHTUNGTREN(NGNU III) intermedi-
AHCTUNGTRENNUNG
À
substituted pyrimidines (entries 4 and 5). Remarkably, H halogenation of arylpyrimidines was developed
a highly monoselective bromination was also smooth- using commonly available calcium halides as crucial
ly realized in high yields using CaBr2 as brominating halogenating agents and cupric trifluoroacetate as oxi-
reagent (entries 6–10), which validates the reaction as dant in the presence of air. Highly monoselective
a practically convenient method for both chlorination ortho-halogenation was achieved and most of the re-
and bromination.
actions were finished within several hours. The char-
To probe the mechanism, reactions were carried acteristics of high monoselectivity and excellent func-
out to obtain the possible active catalytic complex. tional-group tolerance will give the described reaction
The palladium complex 5[13] was obtained in 90% a broad utility in organic synthesis. Further insights
yield from substrate 1q and a stoichiometric amount into the mechanism, reaction scope, and the applica-
of PdACHTUNGTRENNUNG(OAc)2 in HOAc, which would afford palladacy- tions for other directing groups are now under investi-
cle 6 in 92% yield on treatment with 4.0 equiv. of gation in our laboratory, and will be reported in due
CaCl2 under mild conditions. Both complexes 5 and 6 course.
could promote the selective formation of 2q from 1q
in high yields (Scheme 2), indicating that palladacy-
cles 5 or 6 might be the active species during the reac-
tion. The present monoselective halogenation via C
Experimental Section
À
H bond activation may go through either Pd(0)-
Pd(II)[14] or Pd(II)-Pd(IV)[6b,15] intermediates. Recent-
ly, Ritter and Power have shown for the first time that
Typical Procedure for Palladium-Catalyzed ortho
Halogenation of Arylpyrimidines
a PdACHTUNGTRENNUNG(III) complex is responsible for the conversion of
a C H bond to a C Cl bond, we currently cannot CuCAHTUNGTRENNNUG
The arylpyrimidine (1.0 equiv.), Pd
ACHTUNGRTEN(NUNG OAc)2 (5 mol%),
[16]
À
À
(OTFA)2 (1.0–2.0 equiv.), and CaCl2 (4.0–6.0 equiv.) or
332
asc.wiley-vch.de
ꢁ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Adv. Synth. Catal. 2010, 352, 329 – 335

À
Palladium-Catalyzed Monoselective Halogenation of C H Bonds
[a]
À
Table 4. Selective C H chlorination and bromination of arylpyrimidines.
Entry
1
Substrate
No.
Product
No.
Time [h]
4.5
Yield [%][b] of mono/di
1q
2q
92/8
2
3
1r
1s
2r
2s
3
90/9
89/9
3.5
4
5
1t
2t
2
9
88/0
90/6
1u
2u
6
7
8
9
1g
1h
1k
1m
1p
4g
4h
4k
4m
4p
5
3
5
3
4
86/0
95/0
78/0
74/0
95/0
10
[a]
Conditions: PdACHTUNGTRENNUNG(OAc)2 (5 mol%), CuACHTUNTGRNEN(GUN OTFA)2 (1.0–2.0 equiv.), CaCl2 (4.0–8.0 equiv.) in HOAc/Ac2O (1.2:1), or CaBr2
(6.0–8.0 equiv.) in HOAc, 1108C, under air.
Isolated yield.
[b]
Adv. Synth. Catal. 2010, 352, 329 – 335
ꢁ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
asc.wiley-vch.de
333

Bingrui Song et al.
COMMUNICATIONS
Scheme 2. Monoselective halogenation of 2-phenylpyrimidine using palladium complexes 5 and 6.
CaBr2 (6.0 equiv.) were combined in a 25-mL round-bottom
flask, HOAc or HOAc/Ac2O (v/v=1.2:1) was added, and
the mixture was heated at 1108C for 3–24 h under air. The
solvent was removed under vacuum. The residue was diluted
with saturated NaHCO3 solution (15 mL), and the mixture
was extracted with EtOAc (3ꢂ15 mL), washed with brine,
dried over Na2SO4, and concentrated under vacuum. The
obtained crude product was purified using column chroma-
tography on silica gel (EtOAc/petroleum ether) to give the
corresponding products.
[2] For reviews, see: a) R. Taylor, Electrophilic Aromatic
Substitution, Wiley, New York, NY, 1990; b) P. B.
De La Mare, Electrophilic Halogenation, Cambridge
University, Cambridge, 1976.
[3] a) V. Snieckus, Chem. Rev. 1990, 90, 879; b) D. W.
Young, D. L. Comins, Org. Lett. 2005, 7, 5661;
c) M. W. B. McCulloch, R. A. Barrow, Tetrahedron Lett.
2005, 46, 7619; d) T. K. Pradhan, A. De, J. Mortier, Tet-
rahedron 2005, 61, 9007.
À
[4] For reviews, see: a) G. Dyker, Handbook of C H
Transformations, Wiley-VCH, Weinheim, 2005; b) J. C.
Lewis, R. G. Bergman, J. A. Ellman, Acc. Chem. Res.
2008, 41, 1013; c) Y. J. Park, J.-W. Park, C.-H. Jun, Acc.
Chem. Res. 2008, 41, 222; d) D. Alberico, M. E. Scott,
M. Lautens, Chem. Rev. 2007, 107, 174; e) R. G. Berg-
man, Nature 2007, 446, 391; f) K. Godula, D. Sames,
Science 2006, 312, 67; g) F. Kakiuchi, N. Chatani, Adv.
Synth. Catal. 2003, 345, 1077; h) J. A. Labinger, J. E.
Bercaw, Nature 2002, 417, 507; i) V. Ritleng, C. Sirlin,
M. Pfeffer, Chem. Rev. 2002, 102, 1731; j) C. G. Jia, T.
Kitamura, Y. Fujiwara, Acc. Chem. Res. 2001, 34, 633.
[5] For selective references, see: a) Z.-H. Guan, Z.-H.
Ren, S. M. Spinella, S. C. Yu, Y.-M. Liang, X.-M.
Zhang, J. Am. Chem. Soc. 2009, 131, 729; b) J. A.
Jordan-Hore, C. C. C. Johansson, M. Gulias, E. M.
Beck, M. J. Gaunt, J. Am. Chem. Soc. 2008, 130, 16184;
c) S. B. Herzon, J. F. Hartwig, J. Am. Chem. Soc. 2008,
130, 14940; d) L. V. Desai, K. J. Stowers, M. S. Sanford,
J. Am. Chem. Soc. 2008, 130, 13285; e) J. Norinder, A.
Matsumoto, N. Yoshikai, E. Nakamura, J. Am. Chem.
Soc. 2008, 130, 5858; f) K. Cheng, B. B. Yao, J. L. Zhao,
Y. H. Zhang, Org. Lett. 2008, 10, 5309; g) L. J. Gooßen,
K. S. M. Salih, M. Blanchot, Angew. Chem. 2008, 120,
8620; Angew. Chem. Int. Ed. 2008, 47, 8492; h) J.-J. Li,
T.-S. Mei, J.-Q. Yu, Angew. Chem. 2008, 120, 6552;
Angew. Chem. Int. Ed. 2008, 47, 6452; i) K. L. Hull,
M. S. Sanford, J. Am. Chem. Soc. 2007, 129, 11904; j) Y.
Tamura, M. Matsuura, T. Kochi, M. Sato, N. Chatani, F.
Kakiuchi, J. Am. Chem. Soc. 2007, 129, 9858; k) L. Ac-
kermann, A. Althammer, R. Born, Angew. Chem. 2006,
118, 2681; Angew. Chem. Int. Ed. 2006, 45, 2619;
l) W. C. P. Tsang, N. Zheng, S. L. Buchwald, J. Am.
Chem. Soc. 2005, 127, 14560; m) V. G. Zaitsev, D. Sha-
Supporting Information
Experimental details, spectroscopic characterization data,
1
copies of the H NMR, 13C NMR and 19F NMR spectra for
all compounds and X-ray crystal structure for compound 2t
are given in the supporting information file.
Acknowledgements
We thank the National Natural Science Foundation of China
(No. 20672071 and 20972093), Shanghai Pujiang Program
(No. 07pj14043), and Shanghai Municipal Education Com-
mission (No. J50102 and 10YZ06) for financial support. The
authors thank Prof. Hongmei Deng for spectral support.
References
[1] a) A. de Meijere, F. Diederich, Metal-Catalyzed Cross-
Coupling Reactions, Wiley-VCH Verlag GmbH & Co.
KGaA, Weinheim, Germany, 2004; b) J. F. Hartwig,
Handbook of Organopalladium Chemistry for Organic
Synthesis, Wiley-Interscience, New York, 2002; c) K. C.
Nicolaou, P. G. Bulger, D. Sarlah, Angew. Chem. 2005,
117, 4516; Angew. Chem. Int. Ed. 2005, 44, 4442; d) J.
Hassan, M. Sꢃvignon, C. Gozzi, E. Schulz, M. Lemaire,
Chem. Rev. 2002, 102, 1359; e) A. F. Littke, G. C. Fu,
Angew. Chem. 2002, 114, 4350; Angew. Chem. Int. Ed.
2002, 41, 4176.
334
asc.wiley-vch.de
ꢁ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Adv. Synth. Catal. 2010, 352, 329 – 335

À
Palladium-Catalyzed Monoselective Halogenation of C H Bonds
bashov, O. Daugulis, J. Am. Chem. Soc. 2005, 127,
13154; n) F. Kakiuchi, S. Kan, K. Igi, N. Chatani, S.
Murai, J. Am. Chem. Soc. 2003, 125, 1698.
and references cited therein; d) K. Itami, D. Yamazaki,
J.-I. Yoshida, J. Am. Chem. Soc. 2004, 126, 15396.
[11] a) B. Xu, A. Stephens, G. Kirschenheuter, A. Greslin,
X. Cheng, J. Sennelo, M. Cattaneo, M. L. Zighetti, A.
Chen, S.-A. Kim, H. S. Kim, N. Bischofberger, G.
Cook, K. A. Jacobson, J. Med. Chem. 2002, 45, 5694;
b) B. Song, S. Wang, C. Sun, H. Deng, B. Xu, Tetrahe-
dron Lett. 2007, 48, 8982; c) C. Sun, B. Xu, J. Org.
Chem. 2008, 73, 7361; d) W. C. Ye, J. Mo, T. K. Zhao,
B. Xu, Chem. Commun. 2009, 3246.
[12] CCDC 739066 contains the supplementary crystallo-
graphic data for compound 2t of this paper. These data
can be obtained free of charge from The Cambridge
Crystallographic Data Centre via www.ccdc.cam.ac.uk/
data_request/cif.
[6] For selective examples, see: a) X. S. Wang, T.-S. Mei, J.-
Q. Yu, J. Am. Chem. Soc. 2009, 131, 7520; b) N. D.
Ball, M. S. Sanford, J. Am. Chem. Soc. 2009, 131, 3796;
´
c) X. D. Zhao, E. Dimitrijevic, V. M. Dong, J. Am.
Chem. Soc. 2009, 131, 3466; d) T.-S. Mei, R. Giri, N.
Maugel, J.-Q. Yu, Angew. Chem. 2008, 120, 5293;
Angew. Chem. Int. Ed. 2008, 47, 5215; e) X. B. Wan,
Z. X. Ma, B. J. Li, K. Y. Zhang, S. K. Cao, S. W. Zhang,
Z. J. Shi, J. Am. Chem. Soc. 2006, 128, 7416; f) D. Ka-
lyani, A. R. Dick, W. Q. Anani, M. S. Sanford, Org.
Lett. 2006, 8, 2523; g) X. Chen, X.-S. Hao, C. E. Good-
hue, J.-Q. Yu, J. Am. Chem. Soc. 2006, 128, 6790; h) R.
Giri, X. Chen, J.-Q. Yu, Angew. Chem. 2005, 117, 2150;
Angew. Chem. Int. Ed. 2005, 44, 2112.
[13] L. F. Krylova, I. G. Lukyanova, Metall. Khim. 1992, 5,
390.
[7] Y.-H. Zhang, B.-F. Shi, J.-Q. Yu, J. Am. Chem. Soc.
[14] For selected references involving a Pd(II) complex,
see: a) D. A. Watson, M. Su, G. Teverovskiy, Y. Zhang,
J. Garcꢅa-Fortanet, T. Kinzel, S. L. Buchwald, Science
2009, 325, 1661; b) J. F. Hartwig, Inorg. Chem. 2007, 46,
1936; c) A. H. Roy, J. F. Hartwig, Organometallics 2004,
23, 1533; d) A. H. Roy, J. F. Hartwig, J. Am. Chem.
Soc. 2003, 125, 13944.
[15] For a selected reference involving a Pd(IV) complex,
see: S. R. Whitfield, M. S. Sanford, J. Am. Chem. Soc.
2007, 129, 15142.
2009, 131, 5072, and references cited therein.
[8] a) J.-P. Djukic, C. Michon, D. Heiser, K.-G. N. Kyritsa-
kas-Grꢄber, A. de Cian, K. H. Dçtz, M. Pfeffer, Eur. J.
Inorg. Chem. 2004, 2107; b) G. B. Caygill, P. J. Steel, J.
Organomet. Chem. 1990, 395, 375.
[9] D. Kalyani, A. R. Dick, W. Q. Anani, M. S. Sanford,
Tetrahedron 2006, 62, 11483.
[10] a) G. M. Blackburn, M. J. Gait, Nucleic Acids in
Chemistry and Biology, 2nd edn., Oxford University
Press, Oxford, 1996; b) J. A. Joule, K. Mills, Heterocy-
clic Chemistry, Blackwell Publishing, Cambridge, 4th
edn., 2000, p 194; c) H. Sasabe, T. Chiba, S.-J. Su, Y.-J.
Pu, K. Nakayama, J. Kido, Chem. Commun. 2008, 5821,
[16] For a selected reference involving a PdACTHNURTGNEU(GN III) complex,
see: D. C. Power, T. Ritter, Nature Chemistry 2009, 1,
302.
Adv. Synth. Catal. 2010, 352, 329 – 335
ꢁ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
asc.wiley-vch.de
335