Atom-Efficient Synthesis of Alkynylfluoroborates Using BF₃ -Based Frustrated Lewis Pairs

Area of Science:

• Organometallic Chemistry
• Synthetic Organic Chemistry
• Boron Chemistry

Background:

• Boron trifluoride is a Lewis acid, but its reactivity is often limited.
• C-H borylation is a key transformation for introducing boron functional groups.
• Alkynylboron compounds are valuable synthetic intermediates.

Purpose of the Study:

• To develop a new method for C(sp)-H borylation of terminal acetylenes.
• To synthesize novel tri- and tetraalkynylboron compounds.
• To establish an efficient and atom-economical route to alkynylfluoroborates.

Main Methods:

• Formation of a Lewis acid-base pair between 1,2,2,6,6-pentamethylpiperidine (PMP) and boron trifluoride.
• Reaction of the PMP-BF3 pair with terminal acetylenes for C(sp)-H borylation.
• Recovery of PMP from tetrafluoroborate salt byproduct using aqueous NaOH.

Main Results:

• Successful C(sp)-H borylation of terminal acetylenes was achieved.
• Previously unknown tri- and tetraalkynylboron compounds were synthesized.
• Trialkynylfluoroborates were shown to be effective surrogates in C-C coupling reactions.
• Efficient recovery of the PMP amine catalyst was demonstrated.

Conclusions:

• The PMP-BF3 Lewis acid-base pair enables a novel C(sp)-H borylation pathway.
• This methodology provides a straightforward and atom-efficient synthesis of useful alkynylfluoroborates.
• The developed approach facilitates the generation of valuable boron-containing organic compounds.