Method for preparation of benzimidazole derivatives

A method for preparing benzimidazole derivatives, the method comprising:

• 1) preparing a compound represented by formula 2 below by reacting a compound represented by formula 3 below with a monovalent copper catalyst in a presence of a ligand represented by formula 4 below or a stereoisomer thereof;
• 2) preparing a compound represented by formula 5 below by reacting a compound represented by formula 2 below;
• and
• 3) preparing a compound represented by formula 1 below by reacting a compound represented by formula 5 below, acetyl chloride, and a compound represented by formula 6 below in a presence of a base,
• wherein,
• R1 is C1-4 alkyl or phenyl, wherein at least one H of the C1-4 alkyl and phenyl may be substituted with halogen or C1-4 alkyl,
• R2 is H, C1-4 alkyl or acetyl, wherein at least one H of the acetyl may be substituted with halogen,
• R3 and R4 are each independently selected from the group consisting of H, C1-4 alkyl and C3-7 cycloalkyl, or together form a 3- to 7-membered alicyclic ring, wherein at least one H of the C1-4 alkyl, C3-7 cycloalkyl and the formed 3- to 7-membered alicyclic ring may be substituted with halogen, and
• R5 is H, C1-4 alkyl or acetyl.