(Hive Bee)
01-12-03 16:44
No 397551
(Rated as: excellent)
The Bayer-Villiger Oxidation of Aromatic Aldehydes and Ketones with H2O2 Catalyzed by Selenium Compounds – A Convenient Method for the Preparation of Phenols
This paper describes preparation of several phenols from the corresponding aromatic aldehydes. Here is one of them:
Preparation of p-MeO phenol from p-anisaldehyde
p-anisaldehyde (50 mmol) is dissolved in CH2Cl2 (100mL) and 2-NO2C6H4SeSeC6H4NO2-2 (2 mmol) and 30% H2O2 (13mL, 128 mmol) are added. The mixture is stirred magnetically at room temperature (water bath) for 30 minutes. Insoluble catalyst is removed by filtration and washed with CH2Cl2 (20mL) and water (20mL). It can be reused after drying. To the filtrate and washings, water (100mL) is added, and the layers are separated after shaking. The organic layer is washed subsequently with 10% NaHSO3 solution (100mL), 10% Na2CO3 solution (100mL), water (100mL) and dried over Na2SO4. 4-methoxyphenol is obtained by alkaline hydrolysis of the residue. Yield: 93%.
Reference: Synthesis, 1989, No. 3, pp 167
I'm dreaming of the white crystals.
(Hive Bee)
01-13-03 18:02
No 397799
Do you have any further information about the used catalyst? It doesn't look something I can acquire by sending an order fax to Sigma-Aldrich (or any other chem supplier), so I was wondering if:
1. the catalyst is easily prepared;
2. other selenium catalysts (I was thinking of e.g. SeO2) can be applied instead?
All by all, another nice finding which adds to the beautiful diversity of organic chemistry.
Ave Hive, synthetisandi te salutant!
(Hive Bee)
01-14-03 02:12
No 397922
(Rated as: excellent)
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).
(Hive Bee)
01-14-03 08:40
No 398023
Sulfuric acid and hydrogen peroxide... Well, if that's all I'm sure it's a very nice alternative :) Especially the anisaldehyde yielding nearly quantitative yields of p-MeO-phenol might be interesting for some bees.
Ave Hive, synthetisandi te salutant!
(Hive Bee)
01-23-03 15:27
No 400815
GC_MS: The paper says you can use SeO2 (2 mmol), but the reaction time is then increased to 34 h.
I'm dreaming of the white crystals.
(Hive Addict)
01-18-04 22:29
No 483223
Just acid and peroxide? I'm finding it hard to believe it's that simple. Though I doubted the oxone method at first too. How is the phenol isolated from the acidic peroxide solution? Solvent? Is the medium neutralized, diluted, etc or anything before the phenol is extracted?
Also I want to know if anybody has the full article on rhodiums 4-methoxyphenol page....
The oxidation of 4-methoxybenzaldehyde using the system hydrogen peroxide-boric acid-sulfuric acid gave 4-methoxyphenol in 97% yield [3]
[3]Synth. Commun. 29, pp. 3781-3791 (1999)
(Hive Addict)
01-19-04 23:55
No 483401
Demorol-- I see that the reaction time is increased to 34hrs, but what are the yields of the 34hr SeO2? The same or nearly as high?
(Hive Bee)
01-20-04 11:32
No 483507
Yield of 2,5-dimethoxyphenol after 34 hours is 92%, so I guess SeO2 could be used as an alternative.
(Hive Bee)
01-21-04 00:20
No 483627
another route to phenols is HBr catalyzed air oxidation of aromatic compounds linked to a alkyl group at a secondary carbon, for instance cumene reacts under these conditions to give phenol and acetone.(i beleive the reaction conditions involve bubbling air through solvent at around 70C for several days)
if one had a need to economically prepare bulk phenol from otc substances, one could presumably perform this air oxidation on polystyrene dissloved in an appropriate solvent.
(Moderator)
01-31-04 14:11
No 485689
(Rated as: good read)
The article requested in Post 483223 (sYnThOmAtIc: "What, thats it?", Novel Discourse):
Synth. Commun. 29, pp. 3781-3791 (1999)
Chemistry is our Covalent Bond
(Hive Addict)
02-01-04 18:53
No 485855
Well piss on me..
I appreciate the article Lugh, but again I have been shot inbetween the eyes. The only pratical method is referenced from (3) J. Org. Chem. for the methanol based system. THF isn't pratical here. I'm getting an attitude twitch in the eye. I seem to remember a similar problem in the Lange demethylation. The cited method for the HCL demethylation there was a reference of another paper as well.
I really need to find a good library. Paying $25 dollars to see a switch in solvents is pathetic..
Anybody have access to free Journal of Organic Chemistry? If you do and are reasonably able to help, please post the reference #3 J. Org. Chem. 1984, 49, 4740. I found the document online but they want $25 dollars for it??
(Active Asperger Archivist)
02-01-04 19:35
No 485857
there is an entire sticky thread devoted to the retrival of such documents. "wanted references" - just do a search. place a request, watch your article appear before your very eyes. ok, so maybe it isn't quite that simple, but a JOC article shouldn't be any problem for the bees around here.
Act quickly or not at all.
(Hive Addict)
02-01-04 19:53
No 485858
I don't think my insignificant interests would motivate many people here to help me. I'm not a very well liked bee. I think that forum is reserved for important posts that have a high value to this place.
Yeah and thanks again Lugh
(Chief Bee)
02-02-04 11:37
No 486027
The sticky thread is for everyone, just so that requests aren't going to be forgotten in the noise.
Acid-catalyzed oxidation of benzaldehydes to phenols by hydrogen peroxide
Masakatsu Matsumoto, Kisako Kobayashi, Yasushi Hotta
J. Org. Chem. 49, 4740-4741 (1984) (../rhodium/pdf /acidic.h2o2.
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