Notes
Bull. Korean Chem. Soc. 2014, Vol. 35, No. 11 3367
and used as received. The courses of all reactions were
Table 2. β-Cyclodextrin catalyzed oxidation of aldehydes with
1
monitored by TLC using silica gel plates. Standard H-NMR
H2O2/PTSA
a
spectra were recorded in CDCl3 by the Varian Gemini 2000
(300 MHz) spectrometer with tetramethylsilane (TMS) as an
internal reference. Mass spectra were recorded with a Micro-
mass Autospec spectrometer. All products were known and
Entry
Aldehyde
PhCHO
Acid
PhCOOH
Yield (%)
1
2
3
4
5
6
7
8
9
98
85
88
78
91
80
91
92
80
84
83
77
82
80
70
72
4-CH3C6H4CHO
3-CH3OC6H4CHO
4-CH3OC6H4CHO
4-BrC6H4CHO
4-CH3C6H4COOH
3-CH3OC6H4COOH
4-CH3OC6H4COOH
4-BrC6H4COOH
4-ClC6H4COOH
2,4-(Cl)2C6H4COOH
4-FC6H4COOH
1
identified by comparison of their H-NMR spectra with
those of reported literature data.
General Procedure. To a solution of 30% hydrogen per-
oxide (5.0 mmol) was added aldehyde (1.0 mmol), PTSA
(1.0 mmol) and β-cyclodextrin (0.1 mmol). The reaction
4-ClC6H4CHO
2,4-(Cl)2C6H4CHO
4-FC6H4CHO
o
mixture was stirred for 15 h at 50 C. After cooling to room
2-Naphtaldehyde
2-Naphtoic acid
temperature, the reaction mixture was dissolved in the solu-
tion of 10% aqueous sodium bicarbonate, extracted into
diethyl ether (2 × 25 mL), and washed with water. The aque-
ous layer was acidified to pH 3 with 2 M hydrochloric acid.
The product was extracted with dichloromethane (2 × 25
mL) and dried over magnesium sulfate. Evaporation of organic
layer under reduced pressure gave the desired carboxylic
acid.
10 C6H5CH2CHO
C6H4CH2COOH
11 C6H5CH(CH3)CHO C6H4CH(CH3)COOH
12 C6H5CH2CH2CHO
13 PhCH=CHCHO
14 C5H9CHO
C6H4CH2CH2COOH
PhCH=CHCOOH
C5H9COOH
15 C6H11CHO
C6H11COOH
16 CH3(CH2)6CH2CHO CH3(CH2)6CH2COOH
a
Isolated yield.
Acknowledgments. This research was supported by the
Chung-Ang University excellent freshman scholarship grants
in 2014.
protocol and the results are summarized in Table 2. As shown
in the Table 2, aromatic alcohols with electron donating and
electron withdrawing substituents in aromatic rings provided
equally high yields of the corresponding carboxylic acids. In
addition, acid sensitive methoxy groups on the aromatic
rings or double bond in trans-cinnamaldehyde were not
affected at the present reaction conditions (entries 3-4, 13).
Previously similar hydrogen peroxide mediated methods in
acidic conditions failed to give satisfactory yields of such
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20
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24
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All aldehydes, β-cyclodextrin, PTSA, and 30% hydrogen
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peroxide were obtained from commercial source (Aldrich)