[Mahmedgamel]

Kindly, I need an explanation for this problem.

[rolnor]

Whats your thoughts?

[Mahmedgamel]

The fourth option will be, I think, Because HMTA will do insertion of CHO group in third position, then cyclization will happen by abstraction of that proton which near to the CO2Et group then elimination of water and aromatization generated. There was a CO2Et missing in the forth option in that image. I attached a new image Kindly have a look at that.

[rolnor]

I think its correct

[Mahmedgamel]

Thanks.

[rolnor]

Its missing one step, the decarboxylation, so 3 could be right.

[Mahmedgamel]

I think CHO group insertion will not happen at C2. It will happen at C3 due to the stable resonance structure, and the octet of the pyridine ring will be affected by resonance.
Then, if given hydrolysis and heat, the product will be the fourth option, as shown in image 500. But that image was cropped to the CO2Et in the fourth option. So I think the fourth option is correct. As shown in image 501, hydrolysis and heat are not given in question.