ISSUE:

Hello, could someone please give me a graphic example of a retrosynthesis or synthesis route of cetirizine and explain that reaction mechanism in the comments? I can't find much information about the explanation of the topic and I need to learn it for a future university project: C please.

Hi Alex,
I propose the following solution to your problem, I attach the following retrosynthetic analysis and its corresponding synthesis, we will use the following reactions:
1.-Friedel Crafts acylation of benzene using 4-chlorobenzoic acid chloride.
2.-Alkylation of piperazine using a reductive alkylation, which is based on the formation of an imine and its subsequent reduction using sodium cyanoborohydride.
3.-Alkylation of the resulting amine using oxirane in THF (nucleophilic substitution)
4.-Alkylation of the resulting alcohol using ethyl chloroacetate (nucleophilic substitution)
5.- Hydrolysis of the methyl ester using the Krapcho reaction (nucleophilic substitution)