IMPROVED METHOD FOR PREPARING 5-[2-ETHOXY-5-(4-METHYLPIPERAZIN-1-YLSULFONYL)PHENYL]-1-METHYL-N-PROPYL-1, 6-DIHYDRO-7H-PYRAZIL[4,3-D]PYRIMIDINE-7-ONE Russian patent published in 2004 - IPC

FIELD: organic chemistry, chemical technology, pharmacy.

SUBSTANCE: invention relates to the improved method for preparing 5-[2-(ethoxy-5-(4-methylpiperazin-1-ylsulfonyl)-phenyl]-1-methyl-3-n-propyl-1,6-dihydro-7H-pyrazol[4,3-d]pyrimidine-7-one of the formula (I)

and its pharmaceutically acceptable salts. Method involves interaction of compound of the formula (II)

wherein R₁ and R₂ means hydrogen atom, or R₁ means hydrogen atom and R₂ means methyl group with a mixture of formic acid and formaldehyde in the presence of tetrabulyl ammonium bromide in the ratio tetrabutyl ammonium bromide to the parent compound from 1:60 to 1:130 but preferably 1:100. Also, invention proposes a method for preparing 5-[2-ethoxy-5-(4-methylpiperazin-1-ylsulfonyl)-phenyl]-1-methyl-3-n-propyl-1,6-dihydro-7H-pyrazol[4,3-d]pyrimidine-7-one of the formula (I) and its pharmaceutically acceptable salts by interaction of compound of the formula (II) wherein R₁ means methyl group; R₂ means hydrogen atom with formic acid and formaldehyde or dimethylsulfate in the presence of tetrabutyl ammonium bromide in the ratio tetrabutyl ammonium bromide to the parent compound from 1:60 to 1:130 but preferably 1:10 and if necessary in the presence of a base, such as sodium hydroxide, potassium hydroxide and potassium carbonate. Invention provides enhancing purity of the end compound.

EFFECT: improved preparing method.

6 cl, 7 ex