C-N Bond Formation by Consecutive Continuous-Flow Reductions towards A Medicinally Relevant Piperazine Derivative

Area of Science:

• Organic Chemistry
• Process Chemistry
• Pharmaceutical Synthesis

Background:

• Cariprazine is an important antipsychotic drug.
• Efficient synthesis of its key intermediate is crucial for pharmaceutical production.
• Current synthetic methods may lack efficiency or scalability.

Purpose of the Study:

• To develop a continuous-flow method for C-N bond formation.
• To optimize a two-step reduction process for cariprazine intermediate synthesis.
• To enhance the efficiency and scalability of pharmaceutical intermediate production.

Main Methods:

• A two-step continuous-flow reduction sequence was designed.
• Selective ester reduction using Diisobutylaluminium hydride (DIBAL-H) in a miniature alternating diameter reactor.
• Reductive amination via catalytic hydrogenation using 5% Platinum on Carbon (Pt/C).
• At-line extraction was employed to manage aluminum salt byproducts.

Main Results:

• A novel continuous-flow method for C-N bond formation was successfully developed.
• The two-step reduction procedure demonstrated efficient synthesis of the cariprazine intermediate.
• Integration of selective ester reduction and reductive amination in a flow system was achieved.
• At-line extraction effectively prevented byproduct precipitation, ensuring process continuity.

Conclusions:

• The developed continuous-flow method offers an efficient route for synthesizing the key intermediate of cariprazine.
• This approach enhances pharmaceutical manufacturing by enabling scalable and streamlined production.
• The integration of novel reactor technology and byproduct management represents a significant advancement in process chemistry.