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COMMUNICATION
Journal Name
branched (Markovnikov) product. Access to the cationic
intermediate noted in Scheme 4 is facilitated by use of the
trifluoroactate anion, which may be readily displaced by an
alkene.18 Electronic effects are not sufficient to explain the present
results, however, because bidentate ligands lacking the methyl
groups exhibit little selectivity for the branched product (cf. Scheme
3). Thus, the high regioselectivity is best rationalized by synergistic
electronic and steric effects, whereby the methyl groups in the
dmphen ligand sterically inhibit formation of the linear coupling
product, as depicted in Scheme 5.
6
7
8
9
15076; (b) J. H. Delcamp, A. P. Brucks and MDO. CI:.1W0.1h0it3e9,/JC.5ACmC.0C5h3e12mA.
Soc., 2008, 130, 11270; (c) E. W. Werner and M. S. Sigman, J. Am.
Chem. Soc., 2010, 132, 13981; (d) E. W. Werner and M. S. Sigman, J.
Am. Chem. Soc., 2011, 133, 9692.
For examples of branched-selective Heck coupling with minimally
biased substrates, such as allyl and homoallyl alcohols, see: (a) K.
Olofsson, M. Larhed and A. Hallberg, J. Org. Chem., 1998, 63, 5076;
(b) J. Mo, L. Xu, J. Ruan, S. Liu and J. Xiao, Chem. Commun., 2006,
3591.
(a) L. N. Qin, X. F. Ren, Y. P. Lu, Y. X. Li and J. R. Zhou, Angew. Chem.,
Int. Ed., 2012, 51, 5915; (b) L. N. Qin, H. Hirao and J. R. Zhou, Chem.
Commun., 2013, 49, 10236. For α-arylation of vinylarenes, see: Y. J.
Zou, L. N. Qin, X. F. Ren, Y. P. Lu, Y. X. Li and J. R. Zhou, Chem. Eur. J.,
2013, 19, 3504.
+
+
S. Z. Tasker, A. C. Gutierrez and T. F. Jamison, Angew. Chem., Int. Ed.,
2014, 53, 1858.
N
N
N
N
Pd
R
Pd
H
vs.
10 For Ni-catalyzed branched-selective benzylation of alkenes, see: (a)
R. Matsubara, A. C. Gutierrez and T. F. Jamison, J. Am. Chem. Soc.,
2011, 133, 19020; (b) E. A. Standley and T. F. Jamison, J. Am. Chem.
Soc., 2013, 135, 1585.
11 (a) A. N. Campbell and S. S. Stahl, Acc. Chem. Res., 2012, 45, 851. (b)
Y. Izawa, C. Zheng and S. S. Stahl, Angew. Chem., Int. Ed., 2013, 52,
3672; (c) D. Wang, Y. Izawa and S. S. Stahl, J. Am. Chem. Soc., 2014,
136, 9914.
Ar
Ar
H
R
R
PdL
PdL
R
Ar
Ar
Linear products
Branched products
Scheme 5. Transition state structures showing the steric contributions to
12 C. Zheng, D. Wang and S. S. Stahl, J. Am. Chem. Soc., 2012, 134,
16496.
branched vs. linear product formation.
13 For leading previous applications of dmphen as a ligand in oxidative
and non-oxidative Heck reactions, see refs. 3b, 3c, 4a and the
following: (a) W. Cabri, I. Candiani, A. Bedeschi and R. Santi, Synlett,
1992, 871; (b) W. Cabri, I. Candiani and A. Bedeschi, J. Org. Chem.,
1993, 58, 7421. (c) P. A. Enquist, P. Nilsson, P. Sjoeberg and M.
Larhed, J. Org. Chem., 2006, 71, 8779; (d) P. A. Enquist, J. Lindh, P.
Nilsson and M. Larhed, Green Chem., 2006, 8, 338; (e) K. S. Yoo, C. H.
Yoon and K. W. Jung, J. Am. Chem. Soc., 2006, 128, 16384; (f) J.
O'Neill, K. S. Yoo and K. W. Jung, Tetrahedron Lett., 2008, 49, 7307;
(g) A. Nordqvist, C. Bjoerkelid, M. Andaloussi, A. M. Jansson, S. L.
Mowbray, A. Karlen and M. Larhed, J. Org. Chem., 2011, 76, 8986.
14 For selected examples, see: (a) R. Corberán, N. W. Mszar and A. H.
Hoveyda, Angew. Chem. Int. Ed., 2011, 50, 7079; (b) R. Zhu and S. L.
Buchwald, Angew. Chem. Int . Ed., 2013, 52, 12655; (c) X. Sun, L.
Zhou, C.-J. Wang and X. Zhang, Angew. Chem. Int. Ed., 2007, 46,
2623; (d) J. Chen, B. Cheng, M. Cao and Z. Lu, Angew. Chem. Int. Ed.,
2015, 54, 4661.
In this study, we have identified a readily accessible PdII catalyst
system for aerobic oxidative coupling of arylboronic acids and
electronically unbiased alkenes. The catalyst enables highly
regioselective formation of α-substituted vinylarenes with
substrates bearing diverse functional groups. The ease of operation
and broad substrate scope make this method readily accessible and
highly appealing for synthetic applications.
We are grateful for financial support from the NIH (R01
GM67173), Shanghai Institute of Organic Chemistry (SIOC
Postdoctoral Fellowship for CWZ) for financial support of this work.
Notes and references
15 For selected examples, see: (a) S. P. Cook, A. Polara and S. J.
Danishefsky, J. Am. Chem. Soc., 2006, 128, 16440; (b) M. B. Johansen
and M. A. Kerr, Org. Lett., 2008, 10, 3497; (c) T. Ozawa, M.
Kanematsu, H. Yokoe, M. Yoshida and K. Shishido, J. Org. Chem.,
2012, 77, 9240; (d) M. Wu and D. Ma, Angew. Chem. Int . Ed., 2013,
52, 9759.
16 Similar reactivity has been observed previously, for examples, see
refs 3c-3d, 4b-4c and the following: (a) W. Cabri, I. Candiani, A.
Bedeschi and R. Santi, J. Org. Chem., 1990, 55, 3654; (b) T. M.
Gøgsig, J. Kleimark, S. O. N. Lill, S. Korsager, A. T. Lindhardt, P.-O.
Norrby and T. Skrydstrup, J. Am. Chem. Soc., 2012, 134, 443.
17 Y. Izawa, D. Pun and S. S. Stahl, Science, 2011, 333, 209.
18 The ability of trifluoroacetate to promote formation of a cationic
intermediate relative to acetate as an anionic ligand was the subject
of considerable focus in the following study: A. B. Weinstein and S. S.
Stahl, Angew. Chem. Int. Ed., 2012, 51, 11505.
1
For reviews, see: (a) A. B. Dounay and L. E. Overman, Chem. Rev.,
2003, 103, 2945; (b) M. Shibasaki, E. M. Vogl and T. Ohshima, Adv.
Synth. Catal., 2004, 346, 1533; (c) K. C. Nicolaou, P. G. Bulger and D.
Sarlah, Angew. Chem., Int. Ed., 2005, 44, 4442.
For reviews, see: (a) R. F. Heck, Acc. Chem. Res., 1979, 12, 146; (b)
W. Cabri and I. Candiani, Acc. Chem. Res., 1995, 28, 2; (c) P. Nilsson,
K. Olofsson and M. Larhed, In The Mizoroki-Heck Reaction; Oestreich,
M., Ed.; John Wiley & Sons: Chichester, 2009, pp 133-162; (d) B.
Karimi, H. Behzadnia, D. Elhamifar, P. F. Akhavan, F. K. Esfahani and
A. Zamani, Synthesis, 2010, 1399.
(a) Y. C. Jung, R. K. Mishra, C. H. Yoon and K. W. Jung, Org. Lett.,
2003, 5, 2231; (b) M. M. S. Andappan, P. Nilsson and M. Larhed,
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Li, O. Saidi and J. Xiao, J. Am. Chem. Soc., 2008, 130, 2424; (e) J.
Ruan, J. A. Iggo, N. G. Berry and J. Xiao, J. Am. Chem. Soc., 2010, 132,
16689.
2
3
4
5
See refs 3d, 3e and the following: (a) P. Harrison and G. Meek
Tetrahedron Lett., 2004, 45, 9277; (b) M. M. S. Andappan, P. Nilsson,
H. V. Schenck and M. Larhed, J. Org. Chem., 2004, 69, 5212; (c) J.
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Hansen and T. Skrydstrup, J. Org. Chem., 2005, 70, 5997; (e) J. Mo
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H. A. Dieck and R. F. Heck, J. Am. Chem. Soc., 1974, 96, 1133.
4 | J. Name., 2012, 00, 1-3
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