Process for producing carbonyl hydrazones

A method for producing a compound of the formula (I) or its salt:

• wherein each of R1 and R2 is hydrogen, unsubstituted or substituted alkyl, unsubstituted or substituted alkenyl, unsubstituted or substituted alkynyl, unsubstituted or substituted aryl, OR3, COR3, or cyano;
• R3 is unsubstituted or substituted alkyl, unsubstituted or substituted alkenyl, unsubstituted or substituted alkynyl, unsubstituted or substituted aryl, or unsubstituted or substituted heteroaryl;
• R1 and R2 may combine together with the adjacent carbon atom of ═CR1R2 to form an unsubstituted or substituted cyclic ring;
• each of R4 and R5 is hydrogen, unsubstituted or substituted alkyl, unsubstituted or substituted alkenyl, unsubstituted or substituted alkynyl, unsubstituted or substituted aryl, unsubstituted or substituted heteroaryl, NR6R7, OR8 or SR9;
• each of R6, R7, R8 and R9 is hydrogen, unsubstituted or substituted alkyl, unsubstituted or substituted alkenyl, unsubstituted or substituted alkynyl, unsubstituted or substituted aryl, or unsubstituted or substituted heteroaryl, unsubstituted or substituted alkylcarbonyl, unsubstituted or substituted alkenylcarbonyl, unsubstituted or substituted alkynylcarbonyl, unsubstituted or substituted arylcarbonyl, or unsubstituted or substituted heteroarylcarbonyl;
• R4 and R5 may combine together with the adjacent skeleton of C/N bond to form a heterocyclic ring;
• which comprises rearranging a compound of the formula (II) or its salt:
• wherein R1, R2, R4 and R5 are as defined above.