technologist
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Benzaldehyde
I am looking for a synthetic route (Of course commercially cheaper) to produce p-hydroxy Benzaldehyde.
May start from Banzaldehyde or Toluene
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chemrox
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Riemer-Tiemann reaction from phenol
"When you let the dumbasses vote you end up with populism followed by autocracy and getting back is a bitch." Plato (sort of)
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smuv
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@chemrox the Riemer-Tiemann reaction would give mostly an ortho product.
Technologist maybe you should look into anethole, which can be converted to p-methoxy-benzaldehyde. Although not exactly what you are asking for, but
since it seems you are looking to make a 4-substituted phenylethylamine analogue, it maybe ok.
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technologist
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Dear SMUV
I think it will be easier if I go for addition of Aldehyde group to Phenol at para position compared to going for Hydroxy group in benzaldehyde.
What is your view. Actually looking for cheapest route for 4-hydroxy benzaldehyde.
Should start from any simple & cheaper molecule.
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chemrox
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@SMUV- that's right, the intermediate keto pulls e's from the pi bond adjacent so the product is ortho .. I wasn't thinking ..
and I was also thinking the fellow should do some reading on his own before asking everyone to do these for him. Once he's tried a few things and
wants some help .. then he should ask.
"When you let the dumbasses vote you end up with populism followed by autocracy and getting back is a bitch." Plato (sort of)
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smuv
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Actually chemrox...you are kind of right. Last night I stumbled upon some Riemer-Tiemann formylation reactions where the ratio of para to ortho
isomers was reversed. The article was written in Chinese so I was only able to view an abstract but apparently the presence of tertiary amines
greatly changes the regioselectivity of this reaction.
Huaxue Xuebao, 46(2), 155-8; 1988
| Quote: | Abstract
In the presence of a tertiary amine, phenols underwent an abnormal Reimer-Tiemann reaction, i.e., the ratio of the para- and ortho-products was
reversed. For example, phenol gave 60% yield of p-hydroxybenzaldehyde, 7% yield of o-hydroxybenzaldehyde and 1% of tarry materials. Whereas in the
absence of the tertiary amines, the yield of para-, ortho-, and tarry materials under the optimum conditions were 8-11, 38-45 and 20% resp. The
conditions of the abnormal Reimer-Tiemann reaction were studied in detail and a mechanism was proposed. o-Methylphenol, and o-methoxyphenol underwent
the above abnormal Reimer-Tiemann reaction similarly. |
Edit another interesting one
Journal of Molecular Catalysis A: Chemical, 130(3), L205-L207; 1998
| Quote: | In the presence of b-cyclodextrin and its derivatives, the photo-Reimer–Tiemann reaction of phenols with chloroform
proceeded smoothly with high selectivity for the formation of 4-hydroxy benzaldehydes. |
The active ingredient in Febreze is cyclodextrin. The 3 isomers could easily be seperated by fractional crystallization as their solubilities in
water vary greatly. In 50% MeOH w/ potassium carbonate as a base there is a 75% selectivity of the para product.
I will note however that the source of this research is a little iffy "Division of Tea Technology, UPASI Tea Research Institute, Valparai 642 127,
India".
[Edited on 7-12-2007 by smuv]
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