Synthesis of K[4-ROC6F4BF3] from potassium pentafluorophenyltrifluoroborate and O-nucleophiles

A new route to potassium polyfluoroaryltrifluoroborates, K[4-ROC6F4BF3], consisting in the nucleophilic alkoxydefluorination of K[C6F5BF3] with MOR (M = K, Na) in a polar aprotic solvent is suggested. Reaction of K[C6F5BF3] with KO-t-Bu proceeds smoothly at 25 °C in DME, but the attempted alkoxydefluorination of K[C6F5BF3] with other NaOR at 30 °C in DME failed. A series of K[4-ROC6F4BF3] (R = Me, Et, Pr, i-Pr, Bu, PhCH2) is prepared using the corresponding sodium alkoxides in DMF at 130 °C in 80–90% isolated yield. Salt K[4-CH2CHCH2OC6F4BF3] is prepared at 100 °C whereas at 130 °C formation of 2,3,5,6-C6F4HOCH2CHCH2 occurs. Salt K[4-PhOC6F4BF3] is obtained in 82% yield using KOPh (2 equivalents) in DMSO at 130 °C.