27. Heterocycles

Draw the structures of products A, B, and C in the following reaction sequence. Select final product.

Pyrrolopyridines are a group of fused heterocycles where a pyrrole ring is fused with a pyridine ring. Nitration of the following pyrrolopyridine produces the 7-nitro product while the 5-nitro product is not seen. Draw resonance structures to show why the 5-nitro product is not formed. (Hint: Draw 5 resonance structures).