The major product formed in the following reaction sequence is

Concept:

• Organolithium reagents contain carbon–lithium (C-Li) bonds. 
• The large difference in electronegativity between the carbon atom and the lithium atom results in highly ionic Carbon−Lithium bonds.
• Because of the polar nature of the C−Li bond, organolithium reagents can act as good nucleophiles as well as strong bases.

Explanation:

• The reaction pathway is shown below:

• From the above reaction, we see that in the first step, the organolithium reagent (^tBuLi) will act as a strong base and will abstract an acidic -H from the pyridine derivative.
• In the last step of the reaction, the resulting carbanion will react with the generated I2 in the reaction medium to give the final product.
• In the reaction medium ICH₂CH₂I will form I₂.

Conclusion:

• Hence, the major product formed in the following reaction sequence is

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