Paper
Organic & Biomolecular Chemistry
hydrogen atom linked to the β-C of products. However, the
dideuterated product 5d-d2 was found to be the dominant
product along with trace amounts of monodeuterated products
when a control experiment was conducted with deuterium-
labeled phenyl acetylene (2b-d1) (Scheme 2, eqn (2)). This
result clearly indicates that the hydrogen atom linked to the
β-C of products was derived from the alkyne substrates.
Notes and references
1 For selected reviews and a book, see: (a) A. Brennführer,
H. Neumann and M. Beller, Angew. Chem., Int. Ed., 2009,
48, 4114; (b) A. Brennführer, H. Neumann and M. Beller,
ChemCatChem, 2009, 1, 28; (c) C. F. J. Barnard, Organo-
metallics, 2008, 27, 5402; (d) L. Kollár, Modern Carbonyla-
tion Methods, Wiley-VCH, Weinheim, 2008.
A
plausible mechanism of the palladium-catalyzed
carbonylative addition of aryl bromides to terminal arylalkynes
is shown in Scheme 3. The oxidative addition of aryl bromide
1 to a Pd(0) species12 with a bidentate ligand generated in situ
is hypothesized to produce a cationic arylpalladium inter-
mediate A.13 Subsequent coordination and insertion of CO
would lead to the formation of a cationic acylpalladium inter-
mediate B. Then, the coordination and insertion of alkyne sub-
strate 2 would occur to generate a cationic alkenylpalladium
intermediate C. Protonation of the intermediate C with sub-
strate 2 would produce the desired chalcone 3 or 4 and an
alkynylpalladium intermediate D. Finally, reductive elimin-
ation of intermediate D could occur to regenerate a Pd(0)
species and produce an alkynyl bromide, which would react
with iPr2NEt to form a quaternary ammonium salt.14
2 (a) J. McNulty, J. J. Nair and A. Robertson, Org. Lett., 2007,
9, 4575; (b) P. Berger, A. Bessmernykh, J.-C. Caille and
S. Mignonac, Synthesis, 2006, 3106; and references therein.
3 (a) W. Yang, W. Han, W. Zhang, L. Shan and J. Sun, Synlett,
2011, 2253, and references therein; (b) A. Schoenberg,
I. Bartoletti and R. F. Heck, J. Org. Chem., 1974, 39, 3318.
4 (a) X.-F. Wu, H. Neumann and M. Beller, Chem. – Eur. J.,
2012, 18, 419; (b) X.-F. Wu, H. Neumann and M. Beller,
Chem. – Eur. J., 2010, 16, 9750; (c) J. McNulty, J. J. Nair,
M. Sliwinski and A. J. Robertson, Tetrahedron Lett., 2009,
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D. M. M. Freckmann, T. E. Barder and S. L. Buchwald,
J. Org. Chem., 2008, 73, 7102; and references therein;
(e) X. Wu and M. Larhed, Org. Lett., 2005, 7, 3327.
In summary, we have developed a new type of palladium-
catalyzed carbonylation reaction for the construction of chal-
cones using aryl bromides and terminal arylalkynes as sub-
strates in the presence of the bidentate ligand DPPB in DMF.
The features of the novel and general catalytic method pre-
sented in the current paper include the commercial availability
of the precatalyst, ligand and substrates as well as mild reac-
tion conditions, experimental simplicity and a broad substrate
scope. The formation of cationic intermediate B plays a key
role in this type of carbonylation. Further studies focusing on
the theoretical explanation of the reaction mechanism and on
the extension of the reaction scope using heteroatom-contain-
ing substrates are underway.
5 (a) A. S. Singh, B. M. Bhanage and J. M. Nagarkar, Tetra-
hedron Lett., 2011, 52, 2383; and references therein;
(b) A. Brennfuhrer, H. Neumann and M. Beller, Synlett,
2007, 2537; and references therein.
6 (a) H. Neumann, A. Brennführer and M. Beller, Chem. –
Eur. J., 2008, 14, 3645; (b) H. Neumann, A. Brennführer and
M. Beller, Adv. Synth. Catal., 2008, 350, 2437;
(c) S. Z. Zheng, L. W. Xu and C. G. Xia, Appl. Organomet.
Chem., 2007, 21, 772; (d) T. Ishiyama, H. Kizaki, T. Hayashi,
A. Suzuki and N. Miyaura, J. Org. Chem., 1998, 63, 4726;
(e) Y. Hatanaka, S. Fukushima and T. Hiyama, Tetrahedron,
1992, 48, 2113; and references therein; (f) K. Kikukawa,
K. Kono, F. Wada and T. Matsuda, Chem. Lett., 1982, 35.
7 (a) A. Park, K. Park, Y. Kim and S. Lee, Org. Lett., 2011, 13,
944; and references therein; (b) X.-F. Wu, H. Neumann and
M. Beller, Chem. – Eur. J., 2010, 16, 12104; and references
therein.
We are grateful to the National Natural Science Foundation
of China (no. 21173032 and 21372035) for financial support.
8 (a) X.-F. Wu, H. Neumann, A. Spannenberg, T. Schulz,
H. Jiao and M. Beller, J. Am. Chem. Soc., 2010, 132, 14596;
(b) X.-F. Wu, H. Neumann and M. Beller, Angew. Chem., Int.
Ed., 2010, 49, 5284.
9 For selected recent papers, see: (a) S. Zhang, Y. Wang,
X. Feng and M. Bao, J. Am. Chem. Soc., 2012, 134, 5492;
(b) B. Peng, S. Zhang, X. Yu, X. Feng and M. Bao, Org. Lett.,
2011, 13, 5402; (c) B. Peng, X. Feng, X. Zhang, S. Zhang and
M. Bao, J. Org. Chem., 2010, 75, 2619; (d) S. Lu, Z. Xu,
M. Bao and Y. Yamamoto, Angew. Chem., Int. Ed., 2008, 47,
4366.
10 For selected methodologies to obtain chalcones, see:
(a) Claisen–Schmidt condensation: B. Krishnakumar,
R. Velmurugan and M. Swaminathan, Catal. Commun.,
2011, 12, 375; and references therein; (b) M. Rueping,
T. Bootwicha, H. Baars and E. Sugiono, Beilstein J. Org.
Chem., 2011, 7, 1680; (c) K. Miura, K. Yamamoto,
Scheme 3 Proposed mechanism of the palladium-catalyzed carbonyl-
ative addition to alkynes.
7236 | Org. Biomol. Chem., 2014, 12, 7233–7237
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