demorol
(Hive Bee)
01-12-03 16:44
No 397551
      Phenols from aldehydes
(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.
 
 
 
 
    GC_MS
(Hive Bee)
01-13-03 18:02
No 397799
      catalyst     

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!
 
 
 
 
    Captain_Mission
(Hive Bee)
01-14-03 02:12
No 397922
      I think you might prefer this:
(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).

 
 
 
 
    GC_MS
(Hive Bee)
01-14-03 08:40
No 398023
      nice     

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!
 
 
 
 
    demorol
(Hive Bee)
01-23-03 15:27
No 400815
      GC_MS: The paper says you can use SeO 2 , but...     

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.
 
 
 
 
    sYnThOmAtIc
(Hive Addict)
01-18-04 22:29
No 483223
      What, thats it?     

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)
 
 
 
 
    sYnThOmAtIc
(Hive Addict)
01-19-04 23:55
No 483401
      Hey you!     

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?
 
 
 
 
    demorol
(Hive Bee)
01-20-04 11:32
No 483507
      Yield of 2,5-dimethoxyphenol after 34 hours is     

Yield of 2,5-dimethoxyphenol after 34 hours is 92%, so I guess SeO2 could be used as an alternative.
 
 
 
 
    stratosphere
(Hive Bee)
01-21-04 00:20
No 483627
      another route to phenols is HBr catalyzed air...     

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.
 
 
 
 
    lugh
(Moderator)
01-31-04 14:11
No 485689
      Article Retrieved
(Rated as: good read)
    

The article requested in Post 483223 (sYnThOmAtIc: "What, thats it?", Novel Discourse):

Synth. Commun. 29, pp. 3781-3791 (1999)



smile

Chemistry is our Covalent Bond
 
 
 
 
    sYnThOmAtIc
(Hive Addict)
02-01-04 18:53
No 485855
      Well god$@*!&% F#(($ING Dam s%!t     

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??
 
 
 
 
    Aurelius
(Active Asperger Archivist)
02-01-04 19:35
No 485857
      Wanted References     

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.
 
 
 
 
    sYnThOmAtIc
(Hive Addict)
02-01-04 19:53
No 485858
      Yeah, but     

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 wink
 
 
 
 
    Rhodium
(Chief Bee)
02-02-04 11:37
No 486027
      Acid-catalyzed oxidation of benzaldehydes     

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.dakin-rxn.pdf)

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