High purity butoconazole nitrate with specified particle size and a process for preparation of thereof

One object of the invention is high purity butoconazole nitrate of the formula (I) (chemical name: 1-[4-(4-chlorophenyl)-2-(2,6-dichlorophenylthio)-n-butyl]-imidazole nitrate) containing maximum 0.1 wt % of chemical impurities, wherein at last 95 % of the particles of the substance are below 75 µm by diameter, whereas at least 99 % of the particles are below 250 µm by diameter. Another object of the invention is a process for the preparation of butoconazole nitrate starting from 1-chloro-4-chlorophenyl-2-butanol and imidazole to yield a compound of the formula (IV), reacting said compound of formula (IV) with thionyl chloride to give a compound of the formula (V) and reacting the obtained compound of the formula (V) with 2,6-dichlorothiophenol, performing said reaction steps in such a manner that the first step is carried out in a mixture of a water immiscible solvent and an aqueous solution of an alkali metal hydroxide or carbonate in the presence a phase transfer catalyst; the second step is accomplished in 1,2-dichloroethane solvent in the presence of dimethylformamide, whereas 1-1.2 mol of thionyl chloride reactant is used based on the amount of the compound of the formula (IV); and the third steps is performed without isolation of the product (VI) from the solution obtained, but to said solution nitric acid is added to give the butoconazole nitrate salt. Still another object of the invention is a process for the preparation of the compound with the above specified particle size starting from crude butoconazole nitrate in such a manner that the starting material is dissolved in a mixture of methanol and methyl isobutyl ketone of 1 - 1.5 : 1 ratio (v/v), this solution is then added to methyl isobutyl ketone cooled to a temperature between 5 °C and -15 °C and the product obtained is isolated. A pharmaceutical composition comprising as active ingredient high purity butoconazole nitrate of specified particle size in admixture with known auxiliaries is also within the scope of the invention.