J. Org. Chem. 1984,49, 4740-4741
Acid-Catalyzed Oxidation of Benzaldehydes to
Phenols by Hydrogen Peroxide
(...)When a solution of 2-methoxybenzaldehyde (a) (5.0 g,
36.7 mmol) and 31% aqueous H2O2 (5.3 g, 48 mmol) in
methanol (50 mL) was stirred with sulfuric acid (0.5 mL)
at room temperature for 24 h, 2-methoxyphenol was
produced in a 94% yield. Similarly, a wide variety of other
benzaldehydes 1 were oxidized to the corresponding phe-
nols and/or methyl benzoates as cited in Table I(...)
Table I. Acid-Catalyzed Oxidation of Benzaldehydes by Hydrogen Peroxide(a)
run benzaldehyde time, h yield%(c)
phenol ester
a 2-methoxy 24 94
b 3-methoxy 68 68
c 4-methoxy 24 90
d 2,3-dimethoxy 63 30 14
e 2,4-dimethoxy 14 90
f 3,4-dimethoxy 5 60
g 2,3,4-trimethoxy 1 97
h 2,4,5-trimethoxy 4 89
i 2,4,6-trimethoxy 2 89
j 3,4-methylenedioxy 24 67 8
k 4-methyl 24 (b) 28 51
l 4-chloro 24 (b) 87
m 4-nitro 12 (b) 80
(a)Unless otherwise stated, benzaldehyde 1 (5 mmol) and 31%
H20z (6.4 mmol) were stirred in the presence of HzS04 (0.1 mL) in
methanol (10 mL) under an argon atmosphere a t room tempera-
ture. (b)The reaction mixture was heated a t refluxing temperature.
(c)All the products were isolated by chromatography (Si02).
