Question: Identify F in the following reaction sequence. F was converted in several steps to the antidepressant paroxetine (trade name Paxil; see also Problem 9.9).

A reaction route, generally useful in the drug and agrochemical industry, which gives the most effective method for the synthesis of complex compounds is called organic synthesis.

The organic synthesis of a molecule includes all the reactions and starting materials that can be used in the synthesis of that compound.

The most effective route is determined from the yield of the compound and the availability of reactants under given reaction conditions.

Paroxetine is an antidepressant that affects the brain that may be unbalanced. The molecular formula of paroxetine is ${\mathrm{C}}_{19}{\mathrm{H}}_{20}{\mathrm{FNO}}_3$.

It is used to treat severe depression disorders, panic disorder, OCD, PTSD, and other nervous disorders.

It belongs to a class of compounds called selective serotonin reuptake inhibitors and is synthesized from 1-benzyl-4-piperidone.

In the first step, the oxygen reacts with electron-deficient methane sulfonyl chloride to replace the proton with the methyl group.

Reaction with thionyl chloride

The phenylmethanamine acts as a nucleophile and attacks the electrophilic carbon which causes a substitution reaction.

Reaction with phenylmethanamine

This is followed by an intramolecular acyl substitution reaction. In this reaction, the nitrogen attacks the carbonyl carbon of the ester group causing the removal of the methoxy group.

Rearrangement to form F

The final product obtained after rearrangement is the compound F (${\mathrm{C}}_{19}{\mathrm{H}}_{20}{\mathrm{FNO}}_3$ ).