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A general and mild method for the synthesis of 2,4-diamino-5-benzylpyrimidines was achieved by the Friedel-Crafts reaction between 2-(methoxymethylene)-3-methoxypropanenitrile (10) and an activated aromatic substrate followed by treatment with guanidine. The method is illustrated by a synthesis of ormetoprim (2) in 75% overall yield from 3,4-dimethoxytoluene (12). Efficient syntheses of trimethoprim (1) and 2 were also accomplished via prior base-catalyzed 1,3-prototropic isomerization of cinnamonitriles 19 and 20, respectively, followed by condensation with guanidine

A general and mild method for the synthesis of 2,4-diamino-5-benzylpyrimidines was achieved by the Friedel-Crafts reaction between 2-(methoxymethylene)-3-methoxypropanenitrile (10) and an activated aromatic substrate followed by treatment with guanidine. The method is illustrated by a synthesis of ormetoprim (2) in 75% overall yield from 3,4-dimethoxytoluene (12). Efficient syntheses of trimethoprim (1) and 2 were also accomplished via prior base-catalyzed 1,3-prototropic isomerization of cinnamonitriles 19 and 20, respectively, followed by condensation with guanidine

The copper [I]-catalyzed exchange of bromine by methoxide in 5-bromovanillin and in 3,5-dibromo-4-hydroxybenzaldehyde provides an efficient method for preparing 3,5-dimethoxy-4-hydroxybenzaldehyde, from which 3,4,5-trimethoxybenzaldehyde is obtained by methylation with dimethylsulfate.

4-Methylbenzoesauremethylester (I) wird in Gegenwart von Aluminiumchlorid zum 3,5-Dibromester (II) bromiert und dann in Pyridin mit Natriummethylat in Gegenwart von Kupfer(I)- Chlorid zum 3,5-Dimethoxyester umgesetzt.