Organic & Biomolecular Chemistry
Communication
using 10 mmol (1.18 g) of allylbenzene 1a resulted in 1.24 g of
the product 2a (eqn (2)).
Conclusions
In summary, we have successfully developed a palladium-cata-
lyzed tandem isomerization–Wacker oxidation of terminal
alkenes, with several advantages such as mild conditions,
simple oxidants, short reaction times and predictability. These
features make this procedure a useful tool for synthetic che-
mists in the preparation of aryl ethylketones.
ð1Þ
ð2Þ
Acknowledgements
We thank the Natural Science Foundation of China
(
(
81102823), the Guangdong Natural Science Foundation
2014A030310342) and the Youth Training Program of
To get more information about the reaction mechanism,
substrate 1a was treated with 5 mol% Pd(OAc) , 1 equiv. of
2
Southern Medical University (PY2013N009) for financial
support.
TsOH, and 3 equiv. of TBHP(aq) in MeCN at room temperature
for 3 hours, and β-methylstyrene was obtained in a 13% yield
(eqn (3)). The reaction of β-methylstyrene under the standard
reaction conditions afforded 2a in a 98% yield (eqn (4)). These
results suggest that β-methylstyrene generated by alkene iso-
merization is an intermediate in the process.
Notes and references
9
1
For recent examples, see: (a) B. Weiner, A. Baeza,
T. Jerphagnon and B. L. Feringa, J. Am. Chem. Soc., 2009,
1
31, 9473; (b) B. W. Michel, J. R. McCombs, A. Winkler and
M. S. Sigman, Angew. Chem., Int. Ed., 2010, 131, 9473;
c) M. A. Bigi and M. C. White, J. Am. Chem. Soc., 2013, 135,
831.
ð3Þ
ð4Þ
(
7
2
(a) J. Smidt, W. Hafner, R. Jira, J. Sedlmeier, R. Sieber,
R. Rüttinger and H. Kojer, Angew. Chem., 1959, 71, 176;
(
b) J. Smidt, Chem. Ind., 1962, 54; (c) J. Smidt, W. Hafner,
R. Jira, R. Sieber, J. Sedlmeier and A. Sabel, Angew. Chem.,
Int. Ed., 1962, 1, 80; (d) J. Tsuji, H. Nagashima and
H. Nemoto, Org. Synth., 1990, 7, 137; (e) M. J. Gaunt,
J.-Q. Yu and J. B. Spencer, Chem. Commun., 2001, 1844;
From these observations, a plausible mechanism is shown
in Scheme 2. The tert-butyl peroxidepalladium(II) complex I
initially coordinates β-methylstyrene generated by alkene iso-
(
f) L. Hintermann, in Transition Metals for Organic Syn-
thesis, ed. M. Beller and C. Bolm, Wiley-VCH, Wein-
heim, 2004, p. 279; (g) J. A. Keith and P. M. Henry,
Angew. Chem., Int. Ed., 2009, 48, 9038; (h) I. W. C.
E. Arends and R. A. Sheldon, in Modern Oxidation
Methods, ed. J.-E. Bäckvall, Wiley-VCH, Weinheim, 2nd
edn, 2010, ch, 5.
9
merization which is promoted by TsOH to give II. Next,
peroxymetalation gives the pseudopalladacyclic species III,
which can decompose with heterolytic O–O bond cleavage to
7
,10
give the methyl ketone product 2a.
3
4
For reviews, see: (a) J. Tsuji, Synthesis, 1984, 369;
(
b) J. M. Takacs and X.-T. Jiang, Curr. Org. Chem., 2003, 7,
369; (c) C. N. Cornell and M. S. Sigman, Inorg. Chem., 2007,
46, 1903; (d) M. S. Sigman and E. W. Werner, Acc. Chem.
Res., 2012, 45, 874; (e) B. W. Michel and M. S. Sigman,
Aldrichimica Acta, 2012, 44, 55.
For the aldehyde formation through Wacker oxidation, see:
(
a) J. Chen and C.-M. Che, Angew. Chem., Int. Ed., 2004, 43,
950; (b) G. K. Friestad, T. Jiang and A. K. Mathies, Org.
Lett., 2007, 9, 777; (c) J. Muzart, Tetrahedron, 2007, 63,
505; (d) G. Jiang, J. Chen, H. Y. Thu, J. S. Huang, N. Zhu
and C. M. Che, Angew. Chem., Int. Ed., 2008, 47, 6638;
e) B. Weiner, A. Baeza, T. Jerphagnon and B. L. Feringa,
4
7
(
J. Am. Chem. Soc., 2009, 131, 9473; (f) P. J. Choi, J. Sperry
and M. A. Brimble, J. Org. Chem., 2010, 75, 7388; (g) P. Teo,
Scheme 2 Plausible mechanism.
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