Catalytic HF Shuttling between Fluoroalkanes and Alkynes

Area of Science:

• Organic Chemistry
• Catalysis
• Fluorination Chemistry

Background:

• Alkynes are versatile building blocks in organic synthesis.
• Fluorinated compounds possess unique properties valuable in materials science and pharmaceuticals.
• Efficient and selective fluorination methods are crucial for accessing novel fluorinated molecules.

Purpose of the Study:

• To develop a novel catalytic system for the hydrofluorination of alkynes.
• To investigate the use of boron trifluoride etherate (BF₃⋅OEt₂) as a catalyst for HF transfer.
• To explore the scope and limitations of this new fluorination methodology.

Main Methods:

• Catalytic hydrofluorination of terminal and internal alkynes using BF₃⋅OEt₂.
• Mechanistic investigations employing Density Functional Theory (DFT) calculations and probe experiments.
• Application of the catalytic system to the recycling of poly(vinylidene difluoride) (PVDF).

Main Results:

• BF₃⋅OEt₂ effectively shuttles HF equivalents from fluoroalkanes to alkynes.
• Aliphatic alkynes yield difluoroalkanes, while diarylalkynes selectively form fluoroalkenes.
• The reaction tolerates various functional groups, including halogens, protected amines, esters, and thiophenes.
• Mechanistic studies indicate BF₃ acts as a Lewis acid and OEt₂ mediates proton transfer.
• Proof-of-concept for PVDF recycling was demonstrated.

Conclusions:

• BF₃⋅OEt₂ is a novel and effective catalyst for alkyne hydrofluorination.
• The developed method offers selective access to valuable difluoroalkanes and fluoroalkenes.
• The catalytic system's functional group tolerance and potential for polymer recycling highlight its significance.