[kea1118]

Hi All,

I've been trying to figure out the mechanism of action for the following steps for the synthesis of esomeprazole/Nexium. For the first photo I understand up to the nitration but I'm lost as to how the nitro group functions as a leaving group. As for the second photo, I just haven't been able to find any literature sources hinting at the mechanism for the creation of an imidazole via potassium ethyl xanthogenate so if you have source or could explain it that would be awesome too. Any help would be greatly appreciated!

Thank you in advance,

[AWK]

Nitration needs HNO₃. Nitro group in 4-nitropyridine-N-oxides can be easily replaced. Read something about properties of pyridine-N-oxides.

[kea1118]

Thank you - do you have any source suggestions?

[AWK]

Look at advanced organic chemistry textbook or search internet or your library for sorce references.

[phth]

People are using the pyridine-N-oxide functional group for umpolung.  This is a common strategy used to synthesize substituted pyridines.  Substituted pyridines behavior with substituents in the ortho and para position behave unlike an aromatic system: e.g. pyridioxal forms extremely unstable immines.... putting an oxide there will put a fractional negative charge in the ortho/para poisition which is unfavorable with a normal pyridine functional group (wants to have a positive charge there). Clayden greeve and warrens textbook cover this topic.

What do you know about the stability of carbonates?