Synthesis of potassium 4-(1-azol-1-yl)-2,3,5,6-tetrafluorophenyltrifluoroborates from K[C6F5BF3] and alkali metal azol-1-ides. The dramatic distinction in nucleophilicity of alkali metal azol-1-ides and dialkylamides

• Nucleophilic substitution of fluorine atom in K[C6F5BF3] with alkali metal azol-1-ides in polar aprotic solvent (DMF, DMSO) at 60–130 °C gives potassium 4-azolino-2,3,5,6-tetrafluorophenyltrifluoroborates, K[4-AzC6F4BF3] (AzH = pyrrole, pyrazole, imidazole, indole, and benzimidazole).
• Diethylamine and morpholine as well as the corresponding sodium amides do not react with K[C6F5BF3] under the same conditions while at 150 °C pentafluorobenzene and R2NC6F4H forms.
• In any cases the N-nucleophiles attack a carbon atom in the para-position to BF3 group of K[C6F5BF3].

Nucleophilic substitution of fluorine atom in K[C6F5BF3] with alkali metal azol-1-ides in polar aprotic solvent (DMF, DMSO) at 60–130 °C gives potassium 4-(azol-1-yl)-2,3,5,6-tetrafluorophenyltrifluoroborates, K[4-AzC6F4BF3] (AzH = pyrrole, pyrazole, imidazole, indole, and benzimidazole). Unexpectedly, diethylamine and morpholine do not react with K[C6F5BF3] under the same conditions while pentafluorobenzene and R2NC6F4H form at 150 °C. Reaction of K[C6F5BF3] with Na[NR2] in diglyme or DMSO proceeds similar way. The assumed reason is the relatively low nucleophilicity of both secondary amines and alkali metal dialkylamides which results in destructive by-reaction with K[C6F5BF3] rather than in its aminodefluorination. This is confirmed by the competitive nucleophilic aminodefluorination of a model substrate, C6F5Ph, with sodium indolide/sodium morpholinide.

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