5-bromvanillin
| Structural formula | |||||||||||||||||||
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| General | |||||||||||||||||||
| Surname | 5-bromvanillin | ||||||||||||||||||
| other names |
3-bromo-4-hydroxy-5-methoxybenzaldehyde |
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| Molecular formula | C 8 H 7 BrO 3 | ||||||||||||||||||
| Brief description |
whitish powder |
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| properties | |||||||||||||||||||
| Molar mass | 231.04 g mol −1 | ||||||||||||||||||
| Physical state |
firmly |
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| density |
1.6062 g cm −3 (25 ° C ) |
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| Melting point | |||||||||||||||||||
| solubility |
almost insoluble in water, soluble in sodium hydroxide , pyridine and DMF |
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| As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions . | |||||||||||||||||||
5-bromovanillin formed during the bromination of vanillin and is an important building block molecule ( English building block ) for the production of syringaldehyde , 3,4,5-trimethoxybenzaldehyde , 3,4,5-trimethoxycinnamic acid or propionic acid 3,4,5-trimethoxyphenyl , from which z. B. the antibiotic trimethoprim or the hallucinogen mescaline are accessible.
presentation
In the synthesis of 5-bromovanillin, conversion of the vanillin used as completely as possible is critical, since the separation of the unreacted starting material from the product requires considerable purification. For the preparation, bromine is reacted with vanillin in hydrobromic acid at a maximum of 5 ° C., 5-bromovanillin being obtained in quantitative yield as light yellow crystals.
In an alternative preparation in which hydrobromic acid and excess bromine are avoided, the bromination takes place in a two-phase system 1,2-dichloroethane / sulfuric acid at 45 ° C. Vanillin is converted with bromine in the presence of hydrogen peroxide in order to oxidize the hydrobromic acid formed during the bromination to bromine and thus return it to the reaction. 5-bromovanillin is obtained in 91-92% yield and in purities over 99% (remaining vanillin content below 0.5%).
In a comparatively simple variant, it is reacted with bromine in a methanolic vanillin solution at 0 to 20 ° C. and 5-bromvanillin is isolated as yellowish crystals in 95% yield.
properties
5-bromovanillin is obtained as a yellowish crystalline powder, which is insoluble in water, but as a phenolic compound dissolves well in alkalis such as sodium hydroxide solution and alcoholates to form the phenolate.
use
By reacting with sodium hydroxide in the presence of small amounts of copper powder, the bromine atom in 5-bromovanillin can be exchanged for a hydroxyl group to form 3-methoxy-4,5-dihydroxybenzaldehyde. Methylation with dimethyl sulfate yields 3,4-dimethoxy-5-hydroxybenzaldehyde, a positional isomer of syringaldehyde , regioselectively .
5-Bromvanillin is a key building block for the synthesis of the naturally widespread syringaldehyde (3,5-dimethoxy-4-hydroxybenzaldehyde), an important precursor for trimethoprim.
Web links
Individual evidence
- ↑ a b c d data sheet 5-bromvanillin from Sigma-Aldrich , accessed on March 9, 2016 ( PDF ).
- ^ Carl L. Yaws: Thermophysical Properties of Chemicals and Hydrocarbons, 2nd Edition . Elsevier Inc., 2014, ISBN 978-0-323-28659-6 .
- ↑ Entry on 5-bromovanillin at TCI Europe, accessed on March 9, 2016.
- ↑ a b c P.S. Manchard, PS Belica, HS Wong: Synthesis of 3,4,5-Trimethoxybenzaldehyde . In: Synth. Commun. tape 20 , no. 17 , 1990, pp. 2659-2666 , doi : 10.1080 / 00397919008051474 .
- ↑ a b Patent US3855306 : Process for the preparation of 2,4,5-trimethoxymethoxybenzaldehyde. Applied on March 27, 1972 , published on December 17, 1974 , applicant: Hoffmann-La Roche Inc., inventor: PA Wehrli.
- ↑ VL Afanas'eva, AV Lyubeshkin, SS Kovaleva, MR Bagreeva, OS Anisimova, RG Glushkov: Oxidative bromination of vanillin . In: Pharm. Chem. J. Band 21 , no. 11 , 1987, pp. 805-809 , doi : 10.1007 / BF01151189 .
- ^ JE Ellis, SR Lenger: A convenient synthesis of 3,4-dimethoxy-5-benzaldehyde . In: Synth. Commun. tape 28 , no. 9 , 1998, pp. 1517-1524 , doi : 10.1080 / 00397919808006854 .
- ^ A. Kleemann, J. Engel, B. Kutscher, D. Reichert: Pharmaceutical Substances - Syntheses, Patents and Applications of the most relevant APIs, 5th Edition . Thieme, 2009, ISBN 978-3-13-179275-4 .