Method for synthesizing 5-chloro-1-aryl-4-(4,5-dicyano-1h-imidazol-2-yl)-3-alkyl-1h-pyrazole derivatives

A method for synthesizing 5-chloro-1-aryl-4-(4,5 -dicyano- 1H-imidazol -2-yl)-3-alkyl-1H-pyrazol compounds of the formula (I):

• wherein:
• R1 to R5, which are identical or different, each represent a group selected from the group consisting of:
• a hydrogen atom,
• a halogen atom, and
• a radical corresponding to the formula -(X)n-R7, in which X represents a group selected from the group consisting of oxygen, sulfur, sulfinyl radical and sulfonyl radical;
• n is 0 or 1;
• and R7 represents a linear or branched, saturated or unsaturated alkyl radical optionally substituted with one or more halogen atoms, which are identical or different, the alkyl radical comprising 1 to 4 carbon atoms;
• R6 represents a linear or branched, saturated or unsaturated alkyl radical comprising from 1 to 6 carbon atoms, optionally substituted with one or more halogen atoms, which are identical or different, which method comprises the steps of:
• (a) converting a pyrazolin-5-one compound of the formula (II) to a 1-aryl-3-alkyl-4-carboxaldehyde-5-chloropyrazol compound of the formula (IV) in one step by a Vilsmeier treatment in the presence of POCl3 and DMF,
• (b) converting the aldehyde of the formula (IV) to a 1-aryl-3-alkyl-4-[(2-amino-1,2-dicyanoethenylimino)methyl]-5-chloropyrazole compound of the formula (V) by condensing the aldehyde of the formula (IV) with diaminomaleonitrile, and
• (c) oxidatively cyclizing the imine of the formula (V) with a hypochiorite to produce the compound of the formula I as shown below: