 
            Trimethoprim synthesis
- Product Name:Trimethoprim
- CAS Number:738-70-5
- Molecular formula:C14H18N4O3
- Molecular Weight:290.32

All of the other syntheses begin with 3,4,5-trimethoxybenzaldehyde. According to one of them, condensation of 3,4,5-trimethoxybenzaldehyde with 3-ethoxy- or 3-anilinopropionitrile gives the corresponding benzylidene derivative (33.1.52), which upon direct reaction with guanidine gives trimethoprim.

Trimethoprim has also been synthesized by condensing 3,4,5-trimethoxybenzaldehyde with malonic acid dinitrile in a Knoevenagel reaction, which forms the derivative (33.1.53), which is partially reduced to the enamine (33.1.54) by hydrogen using a palladium on carbon catalyst, which upon being reacted with guanidine is transformed into trimethoprim.

Finally, trimethoprim can be synthesized in a manner that also uses a Knoevenagel condensation of 3,4,5-trimethoxybenzaldehyde as the first step, but this time with ethyl cyanoacetate, which gives an ylidene derivative (33.1.55). The double bond in this product is reduced by hydrogen over a palladium on carbon catalyst, giving 3,4,5-trimethoxybenzylcyanoacetic ester (33.1.56). Reacting this in a heterocyclization reaction with guanidine gives the desired trimethoprim.
![2,6-diamino-5-[(3,4,5-trimethoxyphenyl)methyl]-1H-pyrimidin-4-one](/CAS/20180601/GIF/37389-83-6.gif) 
                        
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Yield:-
Steps:
                    Multi-step reaction with 2 steps
1: PCl5; POCl3 / 4 h / Heating
2: H2; AcOH / 10 percent Pd/C / H2O
                
References:
Bose, D. Subhas;Narsaiah, A. Venkat [Journal of Chemical Research - Part S,2001,# 1,p. 36 - 38]
![2,4-Dichloro-5-[3,4,5-trimethoxybenzyl]pyrimidine](/CAS/GIF/55694-05-8.gif) 
                        
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![2,4-Pyrimidinediamine, 6-(methylthio)-5-[(3,4,5-trimethoxyphenyl)methyl]-](/CAS/20210305/GIF/39667-16-8.gif) 
                        
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