合成路线1

Reaction of 2-chloronicotinic acid (I) with an ethanolic solution of potassium tert-butoxide affords 2-ethoxynicotinic acid (II), which is further converted to the corresponding ethyl ester (III) by alkylation with iodoethane in the presence of Cs2CO3. Nitration of (III) employing ammonium nitrate and trifluoroacetic anhydride leads to ethyl 2-ethoxy-5-nitropyridine-3-carboxylate (IV). This is then reduced to the aminopyridine (V) by catalytic hydrogenation over Raney Ni. Diazotization of amine (V), followed by treatment with SO2 and CuCl2 gives rise to the sulfonyl chloride (VI). Acid chloride (VI) is subsequently coupled to N-ethylpiperazine (VII), producing sulfonamide (VIII). Alkaline hydrolysis of ethyl ester (VIII) yields the intermediate pyridinecarboxylic acid (IX)