Palladium-catalyzed oxidative carbonylative coupling reactions of arylboronic acids with styrenes to chalcones under mild aerobic conditions

Article abstract of DOI:10.1002/asia.201100630

Do the coupling: A palladium-catalyzed oxidative carbonylative coupling process of arylboronic acid with styrenes to chalcone has been developed. The reactions proceed under mild conditions using air as the terminal oxidant reagent.

Full text of DOI:10.1002/asia.201100630

COMMUNICATION
DOI: 10.1002/asia.201100630
Palladium-Catalyzed Oxidative Carbonylative Coupling Reactions of
Arylboronic Acids with Styrenes to Chalcones under Mild Aerobic
Conditions
Xiao-Feng Wu, Helfried Neumann, and Matthias Beller*[a]
Palladium-catalyzed coupling reactions represent an im-
portant toolbox for the functionalization of arenes.[1] Among
the various types of coupling processes, catalytic carbonyla-
tion reactions allow for the straightforward preparation of
aromatic carboxylic acid derivatives both on the laboratory
and industrial scale.[2] Whilst palladium-catalyzed carbonyla-
tions of aryl halides have been well-established over the last
three decades,[3] the related oxidative carbonylations consti-
tute a conceptually alternative methodology, which has been
scarcely studied. In general, in such reactions two nucleo-
philes are carbonylatively coupled together in the presence
of a suitable oxidant.[4,5] Notably, the formation of the re-
spective arylpalladium(II) complex as a crucial intermediate
can be achieved under milder conditions, because the relat-
ed oxidative addition to aryl halides is difficult in the pres-
ence of CO.
Organoboron compounds are amongst the most-promi-
nent carbon nucleophiles applied in palladium-catalyzed
coupling reactions, especially for Suzuki–Miyaura reac-
tions.[6] The first oxidative methoxycarbonylation of alkenyl-
boron compounds was reported by Suzuki and co-workers
as early as 1981.[7a,b] Later on, Uemura and co-workers
showed the methoxycarbonylation of phenylboronic acid in
diaryl-2-propen-1-ones (chalcones),[8] we had the idea that
oxidative vinylations might also be possible (Scheme 1).
Scheme 1. Synthesis of chalcones: Carbonylative vinylation of aryl hal-
ides versus oxidative carbonylations.
It is well-accepted that chalcones constitute an important
class of natural products belonging to the flavonoid family
of compounds. They display manifold biological activities,
including anti-cancer, anti-inflammatory, anti-oxidant, cyto-
toxic, anti-microbial, analgesic, anti-pyretic, anti-hepatotox-
ic, anti-malarial, and anti-allergic properties.[9] Furthermore,
the reactive a,b-unsaturated carbonyl system has served in a
numbers of reactions as a key intermediate.[10] Thus, in con-
tinuation of our previous work on carbonylation reactions,[11]
herein, we report the first oxidative carbonylative vinylation
reactions of arylboronic acids and a general procedure for
the synthesis of chalcones under mild conditions. Important-
ly, these reactions proceed base-free at low temperatures
with air as the terminal oxidant and no excess of styrene are
needed.
methanol in the presence of [PdACHTNUTRGNEUNG(PPh3)4] and NaOAc as the
catalytic system. They obtained methyl benzoate in 58%
yield together with benzophenone and biphenyl.[7c,d] More
recently, Yamamoto reported the oxidative alkoxycarbony-
lation of arylboronates using a PdACTHNUTRGNEU(NG OAc)2/PPh3 catalyst and
a stoichiometric amount of benzoquinone as the oxidant.[7f]
The desired products were obtained in good yields, and
DFT as well as MP2 calculations were carried out to under-
stand the reaction mechanism. Notably, Lei and co-workers
developed an elegant methodology using air as a benign oxi-
dant in the presence of NEt3 as the base.[7g]
To the best of our knowledge, apart from simple alcohols
no other coupling partners have been applied in oxidative
carbonylations of organoboron compounds to date. Based
on our recent work on the carbonylative synthesis of 1,3-
At the start of our investigations, we chose the coupling
of phenylboronic acid with styrene and CO as a model
system. As shown in Table 1, reactions were proceeded
cleanly in the presence of PdACHTNUTRGNENG(U OAc)2 and various ligands at
808C using air as the final oxidant (Table 1). No reaction
was observed in the absence of stabilizing ligands or in the
presence of nitrogen or monophosphine ligands (Table 1, en-
tries 1–4). A trace of chalcone was detected when DPPM
was used as the ligand (Table 1, entry 5). Gratifyingly, the
product yield was improved to 29% and 33% by using
DPPE and DPPP as ligands, respectively (Table 1, entries 6
and 7). However, no yield or low yields were obtained when
DPPB, DPPPe, DPPF, DPEphos, and Xantphos were used
(Table 1, entries 8–12).
[a] X.-F. Wu, Dr. H. Neumann, Prof. Dr. M. Beller
Leibniz-Institut fꢀr Katalyse e.V. an der
Universitꢁt Rostock
Albert-Einstein-Strasse 29a
18059 Rostock (Germany)
Fax : (+49)381-1281-5000
E-mail: matthias.beller@catalysis.de
Thus, we used DPPP as our standard ligand for further
optimization of the reaction conditions (Table 2). Notably,
the solvent had a significant effect on the product yield;
282
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Chem. Asian J. 2012, 7, 282 – 285

Table 1. Palladium-catalyzed oxidative carbonylation of phenylboronic
acid: The effect of ligands.[a]
yield, respectively (Table 2, entries 7 and 8). Lowering the
catalyst loading to 1 mol% palladium still resulted in good
product yield (86%) at 608C (Table 2, entry 10).
After finding suitable reaction conditions for the oxidative
carbonylation of our model system, we investigated the
scope of the reaction for various arylboronic acids (Table 3).
Simple methyl-, methoxy-, phenyl-, and phenoxy-substituted
Entry
Ligand (mol%)
Yield [%][b]
1
2
–
0
0
Phen (2)
Table 3. Palladium-catalyzed oxidative carbonylation: Variation of aryl-
boronic acids.[a]
3
4
5
6
7
8
9
10
11
12
PPh3 (4)
0
0
1
29
33
3
0
0
BuPAd2 (4)
DPPM (2)
DPPE (2)
DPPP (2)
DPPB (2)
DPPPe (2)
DPPF (2)
DPEphos (2)
Xantphos (2)
Entry
1
Arylboronic acid
Product
Yield [%][b]
95
0
0
[a] PhB(OH)2 (1.0 mmol), styrene (1.0 mmol), DMF (2 mL), PdACTHNUTRGNEUNG(OAc)2
(2 mol%), ligand, air (5 bar), CO (5 bar), 808C, 20 h. [b] Yield was deter-
mined by GC using hexadecane as internal standard. Phen: 1,10-phenan-
throline; DPPM: 1,1-bis(diphenylphosphino)methane; DPPE: 1,2-bis(di-
phenylphosphino)ethane; DPPP: 1,3-bis(diphenyl-phosphino)propane;
DPPB: 1,4-bis(diphenylphosphino)butane; DPPPe: 1,5-bis(diphenylphos-
phino)pentane; DPPF: 1,1’-bis(diphenyl-phosphino)ferrocene; DPEphos:
(oxydi-2,1-phenylene)bis(diphenyl-phosphine); Xantphos: 4,5-bis(diphe-
nylphosphino)-9,9-dimethyl-xanthene.
2
3
4
5
6
7
8
83
80
95
65
89
88
81
Table 2. Palladium-catalyzed oxidative carbonylation of phenylboronic
acid: Optimization of the reaction parameters.[a]
Entry
Solvent
Yield [%][b]
1
2
NMP
DMAc
10
46
3
4
5
6
7
8
9
10
11
DMSO
1,4-dioxane
Toluene
CH3CN
DMSO
DMSO
DMSO
DMSO
DMSO
79
13
10
18
97[c]
95[d]
52[e]
86[f]
37[g]
9
80
[a] PhB(OH)2 (1 mmol), styrene (1 mmol), solvent (2 mL), PdACTHNUTRGNEUNG(OAc)2
(2 mol%), DPPP (2 mol%), air (5 bar), CO (5 bar), 808C, 20 h. [b] Yield
was determined by GC using hexadecane as internal standard. [c] 608C.
10
11
12
91
65
68
[d] 408C. [e] 258C. [f] 608C, Pd
ACHTUNGRTEN(NUNG OAc)2 (1 mol%), DPPP (1 mol%).
[g] 608C, Pd(OAc)2 (0.5 mol%), DPPP (0.5 mol%).
ACHTUNGTRENNUNG
whilst 1-methyl-2-pyrrolidone (NMP) gave only 10% of 1,3-
diphenyl-2-propen-1-one, this yield was improved to 46% in
N,N-dimethylacetamide (DMAc; Table 2, entry 2). To our
delight, chalcone was formed in 79% in dimethyl sulfoxide
(DMSO; Table 2, entry 3). Notably, this solvent has been
shown to be optimal for other palladium-catalyzed oxida-
tions, too.[12] All other more common solvents resulted in
lower yields (Table 2, entries 4–6). Lowering the reaction
temperature improved the product yield further: at 608C
and 408C, the chalcone was afforded in 97% and 95%
13
75
[a] ArB(OH)2 (1 mmol), styrene (1 mmol), DMSO (2 mL), PdACHTUNGTRENNUNG(OAc)2
(2 mol%), DPPP (2 mol%), air (5 bar), CO (5 bar), 608C, 20 h. [b] Yield
was determined by GC using hexadecane as internal standard; average of
two runs.
Chem. Asian J. 2012, 7, 282 – 285
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283

M. Beller et al.
COMMUNICATION
arylboronic acids as well as 2-naphthalenylboronic acid re-
sulted in good to excellent yields of the corresponding chal-
cones (65–95%; Table 3, entries 1-5). Fluoride-, chloride-,
and even bromide-substituted phenylboronic acids gave 80–
89% of chalcones (Table 3, entries 6–9). Similarly, the tri-
fluoromethoxy-decorated phenylboronic acid was successful-
ly coupled with styrene in 91% yield (Table 3, entry 10). In-
terestingly, more-sensitive substrates were also transformed
into their desired chalcones in good yields (65–75%;
Table 3, entries 11–13). At this point it should be noted that
carbonylative vinylations of the corresponding aryl halides
failed in our previous work.[8]
Finally, the oxidative carbonylation of various styrenes
was also tested with phenylboronic acid. As shown in
Table 4, both electron-donating and electron-withdrawing
substituents were tolerated on the aromatic scaffold. How-
ever, in the cases of 2-vinylpyridine and 4-vinylpyridine, no
reaction occurred under our standard conditions. It appears
that there is no clear correlation between the product yield
and the electronic nature of the styrene.
A possible mechanism for the oxidative vinylation of aryl-
boronic acids is proposed in Scheme 2. Initially, we assume a
transmetalation of the arylboronic acid with the active palla-
dium(II) complex. After coordination and insertion of CO,
the corresponding acyl palladium species is formed. Then,
Scheme 2. Proposed reaction mechanism.
coordination and insertion of styrene to the acyl palladium
centre should take place. The terminal product is produced
after elimination with the concomitant generation of a palla-
dium hydride complex. This latter complex is regenerated to
the active species in the presence of air, which finishes the
catalytic cycle.
In conclusion, a general and efficient palladium-catalyzed
oxidative-carbonylative coupling of arylboronic acids with
various styrenes has been developed to afford chalcones.
The reaction proceed under mild conditions; air been ap-
plied as a terminal oxidant reagent. No additional additives
were needed, 20 different chalcones have been synthesized
in 55–97% yield.
Table 4. Palladium-catalyzed oxidative carbonylation of phenylboronic
acids: Variation of the styrene.[a]
Entry
1
Styrene
Product
Yield [%][b]
97
Experimental Section
General Comments
2
3
4
5
6
72
55
63
90
58
All reactions were prepared under an air atmosphere. DMSO, PdACHTUNGTRENNUNG(OAc)2,
and DPPP were purchased from Aldrich and used as received. Gas chro-
matography was performed on an Agilent HP-5890 instrument with a
FID detector and HP-5 capillary column (polydimethylsiloxane with 5%
phenyl groups, 30 m, 0.32 mm i.d., 0.25 mm film thickness) using argon as
the carrier gas. Gas chromatography–mass analysis was carried out on an
Agilent HP-5890 instrument with an Agilent HP-5973 Mass Selective De-
tector (EI) and HP-5 capillary column (polydimethylsiloxane with 5%
phenyl groups, 30 m, 0.25 mm i.d., 0.25 mm film thickness) using helium
as the carrier gas.
Typical Procedure for Oxidative-Carbonylative Coupling of Arylboronic
Acids with Styrenes
PdACTHNUTRGNE(UGN OAc)2 (2 mol%) and DPPP (2 mol%), PhB(OH)2 (1 mmol) were
transferred into a vial (4 mL reaction volume) equipped with a septum, a
small cannula, and a stirring bar. DMSO (2 mL) and styrene (1 mmol)
were injected into the vial by syringe under air. Then, the vial was placed
in an alloy plate, which was transferred into a 300 mL autoclave of the
4560 series from Parr Instruments under an air atmosphere. Then, the au-
toclave was pressurized with air (5 bar) and CO (5 bar) and the reaction
was performed for 20 h at 608C. After the reaction, the autoclave was
cooled down to room temperature and the pressure was released careful-
ly. Hexadecane (0.1 mmol) to the reaction mixture and a part of the mix-
ture was analyzed by GC and GC-MS analysis.
7
88
[a] PhB(OH)2 (1 mmol), styrene (1 mmol), DMSO (2 mL), PdACTHNUTRGNEUNG(OAc)2
(2 mol%), DPPP (2 mol%), air (5 bar), CO (5 bar), 608C, 20 h. [b] Yield
was determined by GC using hexadecane as internal standard; average of
two runs.
284
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Chem. Asian J. 2012, 7, 282 – 285

Palladium-Catalyzed Oxidative Carbonylative Coupling Reactions
[7] a) N. Miyaura, A. Suzuki, Chem. Lett. 1981, 879–882; b) N. Yama-
shita, S. Hyuga, S. Hara, A. Suzuki, Tetrahedron Lett. 1989, 30,
6555–6558; c) T. Ohe, K. Ohe, S. Uemura, N. Sugita, J. Organomet.
Chem. 1988, 344, C5–C7; d) C. S. Cho, T. Ohe, S. Uemura, J. Orga-
nomet. Chem. 1995, 496, 221–226; e) Q. J. Zhou, K. Worm, R. E.
Dolle, J. Org. Chem. 2004, 69, 5147–5149; f) Y. Yamamoto, Adv.
Synth. Catal. 2010, 352, 478–492; g) Q. Liu, G. Li, J. He, J. Liu, P.
Li, A. Lei, Angew. Chem. 2010, 122, 3443–3446; Angew. Chem. Int.
Ed. 2010, 49, 3371–3374.
Acknowledgements
The authors thank the state of Mecklenburg-Vorpommern and the
BMBF for financial support.
Keywords: arylboronic acid · carbonylation · chalcones ·
oxidative coupling · palladium
[8] a) X. F. Wu, H. Neumann, M. Beller, Angew. Chem. 2010, 122,
5412–5416; Angew. Chem. Int. Ed. 2010, 49, 5284–5288; b) X. F.
Wu, H. Neumann, A. Spannenberg, T. Schulz, H. Jiao, M. Beller, J.
Am. Chem. Soc. 2010, 132, 14596–14602; c) X. F. Wu, H. Jiao, H.
Neumann, M. Beller, ChemCatChem 2011, 3, 726–733.
[1] For recent reviews, see: a) F. Alonso, I. P. Beletskaya, M. Yus, Tetra-
hedron 2008, 64, 3047–3101; b) I. P. Beletskaya, A. V. Cheprakov, J.
Organomet. Chem. 2004, 689, 4055–4082; c) P. Rollet, W. Kleist, V.
Dufaud, L. Djakovitch, J. Mol. Catal. A 2005, 241, 39–51; d) A.
Zapf, M. Beller, Chem. Commun. 2005, 431–440; e) A. Frisch, M.
Beller, Angew. Chem. 2005, 117, 680–695; Angew. Chem. Int. Ed.
2005, 44, 674–688; f) C. Torborg, M. Beller, Adv. Synth. Catal. 2009,
351, 3027–3043; g) A. Zapf, M. Beller, Top. Catal. 2002, 19, 101–
109; h) C. E. Tucker, J. G. de Vries, Top. Catal. 2002, 19, 111–118;
i) R. Jana, T. P. Pathak, M. S. Sigman, Chem. Rev. 2011, 111, 1417–
1492; j) N. Selander, K. J. Szabꢃ, Chem. Rev. 2011, 111, 2048–2076;
k) A. Molnꢄr, Chem. Rev. 2011, 111, 2251–2320; l) X. F. Wu, P. An-
barasan, H. Neumann, M. Beller, Angew. Chem. 2010, 122, 9231–
9234; Angew. Chem. Int. Ed. 2010, 49, 9047–9050.
[2] For reviews on palladium-catalyzed carbonylations, see: a) A.
Brennfꢀhrer, H. Neumann, M. Beller, Angew. Chem. 2009, 121,
4176–4196; Angew. Chem. Int. Ed. 2009, 48, 4114–4133; b) A.
Brennfꢀhrer, H. Neumann, M. Beller, ChemCatChem 2009, 1, 28–
41; c) Carbonylation of Benzyl- and Aryl-X Compounds: M. Beller
in Applied Homogeneous Catalysis with Organometallic Compounds,
2nd ed., (Eds.: B. Cornils, W. A. Herrmann), Wiley-VCH, 2002,
Weinheim, pp. 145–156; d) R. Skoda-Fçldes, L. Kollꢄr, Curr. Org.
Chem. 2002, 6, 1097–1119; e) M. Beller, B. Cornils, C. D. Frohning,
C. W. Kohlpaintner, J. Mol. Catal. A 1995, 104, 17–85; f) R. Grigg,
S. P. Mutton, Tetrahedron 2010, 66, 5515–5548.
[3] For selected examples of palladium-catalyzed carbonylations of aryl
halides, see: a) A. Schoenberg, I. Bartoletti, R. F. Heck, J. Org.
Chem. 1974, 39, 3318–3326; b) A. Schoenberg, R. F. Heck, J. Org.
Chem. 1974, 39, 3327–3331; c) A. Schoenberg, R. F. Heck, J. Am.
Chem. Soc. 1974, 96, 7761–7764; d) H. Neumann, A. Brennfꢀhrer,
P. Groß, T. Riermeier, J. Almena, M. Beller, Adv. Synth. Catal.
2006, 348, 1255–1261; e) S. Klaus, H. Neumann, A. Zapf, D. Strꢀb-
ing, S. Hꢀbner, J. Almena, T. Riermeier, P. Groß, M. Sarich, W.-R.
Krahnert, K. Rossen, M. Beller, Angew. Chem. 2006, 118, 161–165;
Angew. Chem. Int. Ed. 2006, 45, 154–158; f) A. Brennfꢀhrer, H.
Neumann, S. Klaus, T. Riermeier, J. Almena, M. Beller, Tetrahedron
2007, 63, 6252–6258; g) J. McNulty, J. J. Nair, A. Robertson, Org.
Lett. 2007, 9, 4575–4578; h) J. R. Martinelli, T. P. Clark, D. A.
Watson, R. H. Munday, S. L. Buchwald, Angew. Chem. 2007, 119,
8612–8615; Angew. Chem. Int. Ed. 2007, 46, 8460–8463; i) A.
Brennfꢀhrer, H. Neumann, M. Beller, Synlett 2007, 2537–2540; j) H.
Neumann, A. Brennfꢀhrer, M. Beller, Chem. Eur. J. 2008, 14, 3645–
3652; k) A. Sergeev, A. Spannenberg, M. Beller, J. Am. Chem. Soc.
2008, 130, 15549–15563.
[9] a) D. N. Dhar, The Chemistry of Chalcones and Related Compound-
s,Wiley, New York, 1981, p. 213; b) R. J. Anto, K. Sukumaran, G.
Kuttan, M. N. A. Rao, V. Subbaraju, R. Kuttan, Cancer Lett. 1995,
97, 33–37; c) W. M. Weber, L. A. Hunsaker, S. F. Abcouwer, L. M.
Deck, D. L. V. Jagt, Bioorg. Med. Chem. 2005, 13, 3811–3820;
d) W. M. Weber, L. A. Hunsaker, C. N. Roybal, E. V. Bobrovnikova-
Marjon, S. F. Abcouwer, R. E. Royer, L. M. Deck, D. L. V. Jagt,
Bioorg. Med. Chem. 2006, 14, 2450–2461; e) A. Modzelewska, C.
Pettit, G. Achanta, N. E. Davidson, P. Huang, S. R. Khan, Bioorg.
Med. Chem. 2006, 14, 3491–3495; f) Z. Nowakowska, Eur. J. Med.
Chem. 2007, 42, 125–137; g) B. P. Bandgar, S. S. Gawande, R. G.
Bodade, J. V. Totre, C. N. Khobragade, Bioorg. Med. Chem. 2010,
18, 1364–1370.
[10] For selected examples, see: a) L. Xu, C. Xia, X. Hu, Chem.
Commun. 2003, 2570–2571; b) K. Y. Koltunov, S. Walspurger, J.
Sommer, Tetrahedron Lett. 2005, 46, 8391–8394; c) Y. Liang, D.
Dong, Y. Lu, Y. Wang, W. Pan, Y. Chai, Q. Liu, Synthesis 2006,
3301–3304; d) A. Mꢀller, R. Stꢀrmer, B. Hauer, B. Rosche, Angew.
Chem. 2007, 119, 3380–3382; Angew. Chem. Int. Ed. 2007, 46, 3316–
3318; e) Y. Wang, J. Ye, X. Liang, Adv. Synth. Catal. 2007, 349,
1033–1036; f) A. S. S. Sido, S. Chassaing, M. Kumarraja, P. Pale, J.
Sommer, Tetrahedron Lett. 2007, 48, 5911–5914; g) A. Saito, M.
Umakoshi, N. Yagyu, Y. Hanzawa, Org. Lett. 2008, 10, 1783–1785;
h) K. Murugan, S. Srimurugan, C. Chen, Chem. Commun. 2010, 46,
1127–1129; i) M. Sugiura, N. Sato, Y. Sonoda, S. Kotani, M. Nakaji-
ma, Chem. Asian J. 2010, 5, 478–481; j) J. Wang, X. Wang, Z. Ge, T.
Cheng, R. Li, Chem. Commun. 2010, 46, 1751–1753.
[11] a) X. F. Wu, H. Neumann, M. Beller, Adv. Synth. Catal. 2011, 353,
788–792; b) X. F. Wu, P. Anbarasan, H. Neumann, M. Beller,
Angew. Chem. 2010, 122, 7474–7477; Angew. Chem. Int. Ed. 2010,
49, 7316–7319; c) X. F. Wu, H. Neumann, M. Beller, Chem. Asian J.
2010, 5, 2168–2172; d) X. F. Wu, H. Neumann, M. Beller, Chem-
CatChem 2010, 2, 509–513; e) X. F. Wu, H. Neumann, M. Beller,
Chem. Eur. J. 2010, 16, 9750–9753; f) X. F. Wu, H. Neumann, M.
Beller, Chem. Eur. J. 2010, 16, 12104–12107; g) X. F. Wu, H. Neu-
mann, M. Beller, Tetrahedron Lett. 2010, 51, 6146–6149; h) X. F.
Wu, B. Sundararaju, H. Neumann, P. H. Dixneuf, M. Beller, Chem.
Eur. J. 2011, 17, 106–110.
[12] For selected examples on oxidation reactions in DMSO, see:
a) K. C. Nicolaou, D. L. F. Gray, T. Montagnon, S. T. Harrison,
Angew. Chem. 2002, 114, 1038–1042; Angew. Chem. Int. Ed. 2002,
41, 996–1000; b) K. C. Nicolaou, Y. L. Zhong, P. S. Baran, J. Am.
Chem. Soc. 2000, 122, 7596–7597; c) B. A. Steinhoff, S. R. Fix, S. S.
Stahl, J. Am. Chem. Soc. 2002, 124, 766–767; d) K. P. Peterson,
R. C. Larock, J. Org. Chem. 1998, 63, 3185–3189; e) R. C. Larock,
T. R. Hightower, J. Org. Chem. 1993, 58, 5298–5300; f) R. C.
Larock, T. R. Hightower, L. A. Hasvold, K. P. Peterson, J. Org.
Chem. 1996, 61, 3584–3585; g) R. C. Larock, T. R. Hightower, G. A.
Kraus, P. Hahn, D. Zheng, Tetrahedron Lett. 1995, 36, 2423–2426;
h) M. Rçnn, J.-E. Bꢁckvall, P. G. Andersson, Tetrahedron Lett. 1995,
36, 7749–7752.
[4] For selected recent examples of palladium-catalyzed coupling reac-
tions of two nucleophiles, see: a) Y. Zhao, L. Jin, P. Li, A. Lei, J.
Am. Chem. Soc. 2008, 130, 9429–9433; b) L. Jin, Y. Zhao, H. Wang,
A. Lei, Synthesis 2008, 649–654; c) Y. Zhao, H. Wang, X. Hou, Y.
Hu, A. Lei, H. Zhang, L. Zhu, J. Am. Chem. Soc. 2006, 128, 15048–
15049.
[5] For excellent reviews on palladium-catalyzed oxidative coupling re-
actions, see: a) C. Liu, H. Zhang, W. Shi, A. Lei, Chem. Rev. 2011,
111, 1780–1824; b) W. Shi, C. Liu, A. Lei, Chem. Soc. Rev. 2011, 40,
2761–2776; c) C. Liu, L. Jin, A. Lei, Synlett 2010, 2527–2536.
[6] For a review on organoboron compounds, see: D. V. Partyka, Chem.
Rev. 2011, 111, 1529–1595.
Received: July 19, 2011
Published online: September 20, 2011
Chem. Asian J. 2012, 7, 282 – 285
ꢂ 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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