The synthesis process of 2-mercapto-5-methoxyimidazo［4

5-b］pyridine

a crucial intermediate of tenatoprazole which is a new proton pump inhibitor

was studied.2

6-Dichloropyridine as raw material was nitrated by nitric acid/sulfuric acid

and after amination 2-amino-3-nitro-6-chloropyridine was obtained.It then reacted with sodium methoxide to give 2-amino-3-nitro-6-methoxypyridine and the intermediate was reduced by H2 with Raney Ni as catalyst to give 2

3-diamino-6-methoxypyridine.Finally cyclization was finished with carbon bisulfide to give the title compound.The optimal reaction conditions and yield(temperature

time

molar yield) were as follows: nitration

110℃

8 h

79.3%; amination

room temperature

10 h

87.6%; methoxylation

65℃

30min

98.7%; reduction

70℃

3 h; cyclization

reflux

4 h

72.4% (two steps).The melting point of the title compound was the same as that reported in literature

and its structure was confirmed by 1H NMR.