合成路线1

The title compound has been obtained by several related ways: The reaction of 2-chloro-3-nitropyridine (I) with methylboronic acid by means of Pd(PPh3)4 and K2CO3 in hot dioxane gives 2-methyl-3-nitropyridine (III), which is condensed with dimethylformamide dimethylacetal (IV) to yield 2-[2-(dimethylamino)vinyl]-3-nitropyridine (V). The oxidation of (V) by means of NaIO4 affords 3-nitropyridine-2-carbaldehyde (VI), which is condensed with semicarbazide (VII) to provide the corresponding semicarbazone (VIII). Finally, the nitro group of (VIII) is reduced with SnCl2 or Na2S to furnish the target 3-aminopyridine-2-carbaldehyde semicarbazone. 2-Methyl-3-nitropyridine (III) can also be obtained by condensation of 2-chloro-3-nitropyridine (I) with diethyl malonate (II) by means of Na, followed by decarboxylative hydrolysis with H2SO4 at 125 C. The direct oxidation of 2-methyl-3-nitropyridine (III) with SeO2 in dioxane gives carbaldehyde (VI), which is treated with ethyleneglycol (IX) and Ts-OH to yield the cyclic acetal (X). The reduction of (X) with H2 over Pd/C in ethanol affords 3-aminopyridine-2-carbaldehyde ethylene ketal (XI), which is treated with semicarbazide (VI) and HCl to afford the target 3-aminopyridine-2-carbaldehyde semicarbazone. The condensation of 2-chloro-3-nitropyridine (I) with tributyl vinyl tin (XII) Pd(PPh3)4 and PPH3 in refluxing toluene gives 3-nitro-2-vinylpyridine (XIII), which is oxidized with O3 and Me2S in methanol to yield 3-nitropyridine-2-carbaldehyde (VI). This compound is condensed with semicarbazide (VII) and reduced to the target compound as already described.