7170
S. Lin, X. Lu / Tetrahedron Letters 47 (2006) 7167–7170
Supplementary data
N
N
ArB(OH)2
Pd(II)
O
Experimental procedure and characterization data for
compounds 1–16 are provided. Supplementary data
associated with this article can be found, in the online
Ar
D
N
N
N
N
A
Pd(II)
References and notes
Pd(II)
Ar
H2O
O
O
C
1. Anastas, P. T.; Williamson, T. Green Chemistry-Frontiers in
Benign Chemical Syntheses and Processes; Oxford Univer-
sity Press: Oxford, 1998.
Ar
2. (a) Aqueous Phase Organometallic Catalysis—Concepts and
Applications; Cornils, B., Herrmann, W. A., Eds.; Wiley-
VCH: Weinheim, Germany, 1998; (b) Li, C.-J.; Chan, T.-H.
Organic Reactions in Aqueous Media; John Wiley & Sons:
New York, 1997; (c) Li, C.-J. Chem. Rev. 2005, 105, 3095;
(d) Li, C.-J.; Chen, L. Chem. Soc. Rev. 2006, 35, 68.
3. (a) Rossiter, B. E.; Swingle, N. Chem. Rev. 1992, 92, 771;
(b) Sibi, M. P.; Manyem, S. Tetrahedron 2000, 56, 8033;
(c) Krause, N.; Hoffmann-Ro¨der, A. Synthesis 2001, 171;
(d) Hayashi, T.; Yamasaki, K. Chem. Rev. 2003, 103,
2829.
N
N
O
Pd(II)
B
Ar
Scheme 2. Mechanism of the Pd(II) catalyzed conjugate addition
reaction.
4. (a) Nishikata, T.; Yamamoto, Y.; Miyaura, N. Angew.
Chem., Int. Ed. 2003, 42, 2768; (b) Nishikata, T.; Yamam-
oto, Y.; Miyaura, N. Organometallics 2004, 23, 4317.
5. Lu, X.; Lin, S. J. Org. Chem. 2005, 70, 9651.
6. (a) Lu, X. Topics in Catalysis 2005, 35, 75; (b) Zhao, L.; Lu,
X.; Xu, W. J. Org. Chem. 2005, 70, 4059; (c) Zhao, L.; Lu,
X. Org. Lett. 2002, 4, 3903.
followed by insertion of the olefin into the carbon–palla-
dium bond giving palladium enolate B or C. b-H elimi-
nation of the C–Pd bond in B is suppressed in the
presence of bpy and protonolysis of B in water gives
the corresponding conjugate addition product
D
with the regeneration of divalent palladium species
making the catalytic cycle possible.
7. Typical procedure for the conjugate addition of phenylbo-
ronic acid to 2-cyclohexen-1-one: To a schlenk tube,
phenylboronic acid (153 mg, 1.25 mmol), 2-cyclohexen-1-
one (48 mg, 0.5 mmol), Pd(OAc)2 (5.6 mg, 0.025 mmol),
bpy (15.6 mg, 0.10 mmol), sodium laurylsulfonate (20 mg)
and distilled water (1.0 mL) were added. The mixture was
stirred and heated at 60 °C for two days until the substrate
disappeared as monitored by TLC. The reaction mixture
was extracted with Et2O. The combined ether solution was
washed with saturated NaCl, dried (MgSO4) and concen-
trated. The residue was purified by flash chromatography
(EtOAc: petroleum ether 1:20) to give the product 1 with
92% yield as a colorless oil. 1H NMR (300 MHz, CDCl3): d
7.40–7.17 (m, 5H), 3.09–2.94 (m, 1H), 2.30–2.66 (m, 4H),
2.22–2.01 (m, 2H), 1.94–1.68 (m, 2H); IR (KBr): m 2939,
2867, 1710, 1497, 1452, 1224, 756, 700 cmꢀ1; MS (70 eV,
EI) m/z (%): 175 (M++1), 174 (M+), 131, 117 (100), 104, 91,
78, 42.
In conclusion, we developed a palladium–bipyridine cat-
alyzed conjugate addition of arylboronic acids to a,b-
unsaturated carbonyl compounds in aqueous media.
The addition of surface active agent made the reaction
system more homogeneous and improved the yields.
Moderate to excellent yields of conjugate addition prod-
ucts were obtained even for the reactions of a,b-unsatu-
rated esters.
Acknowledgements
We thank the National Natural Sciences Foundation of
China (20472099) and Chinese Academy of Sciences for
financial Support.