# Pyridine synthesis by tin(II) chloride reduction of 5-nitronorbornene

What is the reaction mechanism here?

I guess the $$\ce{SnCl2}$$ reduces $$\ce{NO2}$$ to $$\ce{NH2}$$ but then what happens?

• I'm thinking there is a retro-Diels-Alder in there somewhere – Waylander Aug 4 at 11:05
• Can you please show me how exactly, I tried didn’t work – lidya Aug 4 at 15:36
• If I knew exactly I would post an answer. I do not have database access to find the paper where this is reported. – Waylander Aug 4 at 15:39
• @Waylander A side-note about the speculated occurrence of a retro-DA, I'm sceptical; because in the starting material, I count 12, but in the product only 11 carbon atoms. – Buttonwood Aug 4 at 21:11
• @Buttonwood Count again! There are 13 in the SM – Waylander Aug 4 at 22:15

• I already upvoted your answer. But I'm curious about the elimination of acetaldehyde. What is the driving force? Is that mean $\beta$-amino acids are prone to leave $\ce{CO2}$? – Mathew Mahindaratne Aug 9 at 17:00
• Might not. Otherwise, the last elimination step would have been reversible. I think gaining aromatically is a very good point for the elimination. In my experience, I didn't find any decomposition of $\beta$-amino acids during their synthesis. – Mathew Mahindaratne Aug 9 at 21:33