Electrochemical synthesis of pyrazolines and pyrazoles

A process for preparing compounds of general formula (I)

• in which is a single or double bond;
• R1 is alkyl, —C(O)O-alkyl, cycloalkyl, aryl, or heterocyclyl, in each case substituted or unsubstituted;
• R2 is alkyl, —C(O)O-alkyl, cycloalkyl, aryl, or heterocyclyl, in each case substituted or unsubstituted;
• R3 is alkyl, —C(O)O-alkyl, —C(O)O-aryl, —C(O)N-(alkyl)2, —CN, —P(O)(O-alkyl)2, cycloalkyl, aryl, or heterocyclyl, in each case substituted or unsubstituted, or H;
• R4 is present if is a single bond and R4 is alkyl, —C(O)O-alkyl, C(O)O-aryl, cycloalkyl, aryl, or heterocyclyl, in each case substituted or unsubstituted, or H;
• or R3 and R4 together with the carbon atom in the compounds of the formula (I) linking R3 and R4 form a substituted or unsubstituted cycloalkyl or heterocyclyl;
• R5 is alkyl, —C(O)O-alkyl, cycloalkyl, aryl, or a heterocyclyl, in each case substituted or unsubstituted, or H;
• or R4 and R5 together with the carbon atoms in the compounds of the formula (I) linking R4 and R5 with each other form a cycloalkyl or heterocyclyl, in each case substituted or unsubstituted;
• or R1 and R5 together with the carbon atoms in the compounds of the formula (I) linking R1 and R5 form a cycloalkyl or heterocyclyl, in each case substituted or unsubstituted;
• characterized in that compounds of general formula (II)
• where R1 and R2 have the same definition as in the general formula (I) are reacted in an electrochemical reaction in the presence of an iodide source with a compound of formula (III) or (IV)
• where R3, R4 and R5 have the same definition as in the general formula (I).