Convenient and reliable synthetic methods for difluoromethylborates have been established. The intermediary generated difluoromethylsilicate species from TMSCF 2 H (TMS = trimethylsilyl) and potassium tert-butoxide were allowed to react with pinBPh (Me 4 C 2 O 2 BPh) in the presence of 18-crown-6 to give the corresponding borate compound [pinB(Ph)CF 2 H] À K + (18-crown-6) as an air-and moisture-tolerant solid. The unambiguously determined crystal structure of [pinB(Ph)CF 2 H] À K + (18-crown-6) revealed that the difluoromethylborate unit partially coordinated on the potassium ion. Reaction of [pinB(Ph)CF 2 H]-K + (18-crown-6) with potassium difluoride (KHF 2) in acetic acid enabled substitution of the pinacol unit and phenyl group with fluorides, and gave (difluoromethyl)trifluoroborate [F 3 BCF 2 H]-K + (18-crown-6) in a good yield. The crystal structure of air-and moisturetolerant [F 3 BCF 2 H]-K + (18-crown-6), which would be a promising reagent for synthesis of various difluoromethylboron species, showed a polyrotaxane-like polymeric structure based on the K•••F interactions between the K + (18-crown-6), CF 2 H, and BF 3 units.

Lithium 1,3‐bis(2,6‐diisopropylphenyl)‐1,3,2‐diazaborolidinyl‐2‐uide activates the C−F linkage of fluoroform (CF3H) to provide air‐stable difluoromethylborane compounds. Computational analysis of SN2‐type transition state for the C−F bond activation of fluoroform with boryllithium clarifies the mechanism involving the lithium dimeric species in the pre‐reaction complex. FAMT (=3‐fluoro‐l‐α‐methyl‐tyrosine)‐based difluoromethyl‐BNCT (boron neutron capture therapy) drug candidates is thus produced by the present C−F bond activation.