Hard nucleophiles (organometallic, amide, lithium aluminum hydride) attack position 2 of the pyridine ring, giving rise to nucleophilic addition reactions. In the event that a final oxidation stage occurs, with loss of hydride, we can speak of nucleophilic substitution.

a) Addition of organometallics

an organometallic pyridine 01

Rearomatization of the ring is possible by adding an oxidant that removes "H2"

an organometallic pyridine 02

b) Addition of amide. Chichibabin's reaction

an pyridine chichibabin 01


an pyridine chichibabin 02

The sodium amide formed is protonated in the final stage of aqueous workup.

an pyridine chichibabin 03

c) Addition of hydrides

Lithium aluminum hydride adds hydrides to the 2-position of pyridine.
an hydrides 01
The weaker nucleophiles (cyanide, hydroxide, methoxide) fail to attack the 2-position of the pyridine, but do react on pyridinium salts, thanks to the greater polarity of the 2-position.
an hydrides 02