Ritalin is a central nervous system stimulant used primarily in the treatment of attention-deficit/hyperactivity disorder (ADHD) and narcolepsy. It acts by increasing dopamine and norepinephrine levels in the brain through inhibition of their reuptake.
Structurally, Ritalin contains a phenyl ring connected to a piperidine ring through a carbon bearing an ester functional group. The molecule contains several important functional groups and stereochemical features commonly encountered in medicinal chemistry and pharmaceutical synthesis.
Because of its structure, Ritalin is often discussed in the context of electrophilic aromatic substitution, such as Friedel-Crafts acylation, acyl chloride formation using thionyl chloride, Darzens condensation reactions, ester hydrolysis and esterification, as well as transformations involving nitrogen-containing heterocycles.
In the following practice problem, we will focus on the synthesis of Ritalin. In particular, we will examine how the aromatic precursor is functionalized through Friedel-Crafts acylation, how thionyl chloride is used in the preparation of reactive intermediates, and how the Darzens condensation is employed in the construction of key carbon-carbon bonds en route to the final target molecule.
As with all examples in this section, this discussion is presented solely for educational purposes and is not intended to represent a practical or real-world method of preparation.
Practice
Add the missing intermediates and reagents in the following synthesis of Ritalin. Draw curved arrow mechanisms for all the steps for the conversion of intermediate 3-5.
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