Difluoromethane as a precursor to difluoromethyl borates

Area of Science:

• Organic Chemistry
• Organometallic Chemistry
• Green Chemistry

Background:

• Difluoromethane (CF2H2) is an environmentally friendly refrigerant with potential as a difluoromethyl (CF2H-) source.
• The low acidity and instability of the difluoromethyl anion have hindered its use as a chemical feedstock.

Purpose of the Study:

• To develop a method for deprotonating difluoromethane (CF2H2) and stabilizing the resulting difluoromethyl anion (CF2H-).
• To enable the use of CF2H2 as a difluoromethylating agent in organic synthesis.

Main Methods:

• A Lewis pair approach was employed to deprotonate CF2H2.
• The generated CF2H- was captured as a stable R3B-CF2H- adduct.
• A base-free Suzuki reagent was developed using the R3B-CF2H- adduct for palladium-mediated difluoromethylation.

Main Results:

• Successful deprotonation and stabilization of CF2H- were achieved using the Lewis pair strategy.
• The R3B-CF2H- adduct demonstrated utility as a reagent in palladium-catalyzed Suzuki-type difluoromethylation.
• The difluoromethylation reaction proceeded via a templated CF2H- transfer mechanism.

Conclusions:

• The Lewis pair method overcomes the limitations of CF2H2's weak acidity and conjugate base instability.
• This work establishes a novel and efficient route for difluoromethylation using an abundant and eco-friendly feedstock.
• The developed methodology broadens the synthetic utility of difluoromethane in organic chemistry.