Author Topic: Hydroxymethylation of Phenols.  (Read 3358 times)

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amine

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Hydroxymethylation of Phenols.
« on: September 17, 2004, 08:12:00 PM »
According to

Post 525531

(demorol: "2,5-DMBA from 1,4-DMB in 89% yield", Novel Discourse)
1,4-dimethoxybenzene is converted to the benzaldehyde via oxidative hydroxymethylation.

It appears the hydroxylmethylation is done with H2SO4 and Paraformaldehyde.  I'm wondering if this step had to be performed on its own, without the addition of DDQ, would one be able to get the corresponding alcohol. (using a phenol or maybe even something like anisole?)

If this is indeed the case the resulting alcohol can be distilled and oxidized via the DMSO route.

It would be interesting to see what would occur if Paraform,  HBr and the phenolic compound were left to react in DMSO. Since the HBr fits both the utility as a catalyst for the DMSO oxidation and the acid donor required for hydroxymethylation.

Any thoughts or suggestions on this topic would be greatly appreciated.


Nicodem

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Phenols are way too reactive to be ...
« Reply #1 on: September 18, 2004, 11:42:00 AM »
Phenols are way too reactive to be monohydroxymethylated in acidic conditions. They tend to react further and if heat is applied or there is too much acid they form a polymer of the bakelite type (the first plastic polymer known and used).
Even 1,4-dimethoxybenzene is so reactive that you get a large amount of dimeric side products when halomethylating - that is one of the reason why so little catalytic sulphuric acid is used in the example from Demorol's post. Sulphuric acid could dehydrate the hydroxymethyl intermediate and 1,4-dimethoxybenzene into a dimere. While in halomethylations once you get the halogen on the benzylic cation the resulting compound is more stable, in the benzylalcohols and sulphuric acid you always have electrophylic benzylic cations present:

Ph-CH2-OH  +  H+   <==>   Ph-CH2+  +  H2O

It would be interesting to see what would occur if Paraform,  HBr and the phenolic compound were left to react in DMSO. Since the HBr fits both the utility as a catalyst for the DMSO oxidation and the acid donor required for hydroxymethylation.

A few months ago Ning brought up this idea for the 1,4-dimethoxybenzene formylation in a PM.
I told him it might bee possible but that you should bee sure that DMSO/acid does not oxidize the paraformaldehide. I still don't know the answer and unfortunately I don't have any DMSO at the moment.