HTML by Metanoid and Rhodium
A wide variety of benzaldehydes were oxidized to phenols by H2O2 in acidic methanol.
| Run | Benzaldehyde | Time | Yieldc | |
| Phenol | Ester | |||
a |
2-methoxy | 24 h | 93% |
|
b |
3-methoxy | 68 h | 68% |
|
c |
4-methoxy | 24 h | 90% |
|
d |
2,3-dimethoxy | 63 h | 30% |
14% |
e |
2,4-dimethoxy | 14 h | 90% |
|
f |
3,4-dimethoxy | 5 h | 60% |
|
g |
2,3,4-trimethoxy | 1 h | 97% |
|
h |
2,4,5-trimethoxy | 4 h | 89% |
|
i |
2,4,6-trimethoxy | 2 h | 89% |
|
j |
3,4-methylenedioxy | 24 h | 67% |
8% |
k |
4-methyl | 24 hb | 28% |
51% |
l |
4-chloro | 24 hb | 87% |
|
m |
4-nitro | 24 hb | 80% |
|
a. Unless otherwise stated, benzaldehyde 1 (5 mmol) and 31% H2O2 (6.4 mmol) were stirred in the presence of H2SO4 (0.1 mL) in MeOH (10 mL) under Ar at room temp.
b. The reaction mixture was heated at refluxing temperature.
c. All the products were isolated by chromatography (SiO2).
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 phenols and/or methyl benzoates as cited in Table I.