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ChemicalBook CAS DataBase List Trimethoprim
738-70-5

Trimethoprim synthesis

6synthesis methods
Trimethoprim, 2,4-diamino-5-(3,4,5-trimethoxybenzyl)pyrimidine (33.1. 51), is synthesized in various ways. The first scheme of synthesis begins with ethyl ester of 3,4,5-trimethoxydehydrocinnamic acid, which is formylated with ethyl formate using sodium as a base to make an enol of the semialdehyde 3,4,5-trimethoxybenzylmalonic ester (33.1.49), which undergoes a heterocyclization reaction with guanidine to make 2-amino- 4-hydroxy-5-(3,4,5-trimethoxybenzyl)pyrimidine (33.1.50). Subsequent replacement of the hydroxyl group in the resulting product with chlorine using phosphorous oxychloride and then with an amino group using ammonia gives the desired trimethoprim.

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.
-

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]

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