Question

Question. Using any necessary reagents, show how you can accomplish the following multistep synthesis.

Short answer

Benzene undergoes Freidel-crafts acylation in first step which forms acylated product and on reduction with zinc-amalgam and hydrogen chloride, we get another product which on nitration reaction forms product in which nitro group is at para position due to directive influence of alkyl group which is attached at another para position in the ring. Then, on reduction with iron and hydrogen chloride, the nitro group changes to amino group and required product gets formed.

Formation of the product

Step-by-step solution

Step-1. Explanation of part (a):

Benzene undergoes Freidel-crafts acylation in first step which forms acylated product and on reduction with zinc-amalgam and hydrogen chloride, we get another product which on nitration reaction forms product in which nitro group is at para position due to directive influence of alkyl group which is attached at another para position in the ring. Then, on reduction with iron and hydrogen chloride, the nitro group changes to amino group and required product gets formed.

Formation of the product

Step-2. Explanation of part (b):

The given reactant undergoes Hofmann elimination reaction in which first step is methylation reaction which forms quaternary amine, which further on reaction with silver oxide followed by heat undergoes elimination reaction and least substituted double bond gets formed which is the Hofmann product.

Formation of the product

Step-3. Explanation of part (c):

The given reactant undergoes nitration reaction in first step which puts nitro group at para position due to directive influence of phenyl group. Then, on reduction with iron, hydrogen chloride mixture, the nitro group gets converted to amino group, which further undergoes acetylation reaction followed by Friedel-crafts alkylation reaction. The ethyl group after Friedel-crafts alkylation reaction gets substituted at ortho position due to directive influence of
-NHCOCH₃ group. Then, on hydrolysis, -NHCOCH₃ changes to amino group which on diazotisation and reaction with CuCN forms a product which on further reduction with lithium aluminum hydride forms the required product.