合成路线1

Wittig reaction between 2-nitrobenzyltriphenylphosphonium bromide (I) and pyridine-4-carboxaldehyde (II) provided the olefin adduct (IIIa-b) as a mixture of geometric isomers. After, nitro group reduction employing SnCl2, the desired E-isomer (VII), was isolated from the reaction mixture by fractional crystallization. In an alternative approach to intermediate (VII), condensation between 2-nitrobenzaldehyde (IV) and 4-picoline (V) in refluxing acetic anhydride furnished the E-olefin (VI), which was subsequently reduced with SnCl2 to the desired aniline (VII). Acylation of amine (VII) with 4-methoxybenzenesulfonyl chloride (VIII) in pyridine gave sulfonamide (IX). Subsequent oxidation of the pyridine ring to the corresponding N-oxide (X) was accomplished by treatment with peracetic acid at 70 C. The sulfonamide N was finally acetylated in boiling acetic anhydride.