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Palladacycle A or A’ was oxidized with hydrogen per-
oxide and the high-valent palladium complex B might
be formed.[6c] After that, Pd(IV) intermediate B was
converted to compound C via reductive elimination.
Ultimately, the hydroxylated product was released
from C by ligand exchange, and A or A’ was regener-
À
ated as the result of C H activation of the substrate.
On the other hand, 2-(2-chlorophenyl)pyridine was
À
formed as the by-product probably because C Cl re-
ductive elimination occurred from Pd(IV) intermedi-
ate B.[14]
2
À
In conclusion, we have developed a direct C(sp )
H hydroxylation using palladium(II) chloride and hy-
drogen peroxide. This novel reaction is interesting be-
cause it uses hydrogen peroxide as the terminal oxi-
dant, and the combination of aqueous H2O2 and palla-
dium catalyst. Further investigations of the reaction
mechanism are now in progress in our laboratory.
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Experimental Section
General Procedure
2-Phenylpyridine (0.3 mmol), PdCl2 (0.03 mmol), and 35%
aqueous H2O2 (1.5 mmol) in 4-methyl-2-pentanone (1 mL)
in a two-necked flask was stirred at 1008C in an oil bath.
The reaction mixture was filtered through a celite pad and
washed with EtOAc. The solution was treated with 0.5M
aqueous Na2S2O3 and then the organic layer was dried over
MgSO4 and concentrated under vacuum. Purification of the
crude product by flash chromatography on silica gel provid-
ed the desired product.
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