Sodium Butylated Hydroxytoluene: A Functional Group Tolerant,Eco-Friendly Base for Solvent-Free,Pd-Catalysed Amination

NaBHT (sodium 2,6-di-tert-butyl-4-methylphenolate), a strong, but hindered and lipophilic base, has been effectively paired with similarly lipophilic, high-reactivity Pd-NHC (N-heterocyclic carbene) catalysts to produce an ideal combination for performing solvent-free (melt) cross-coupling amination. The mild nucleophilicity of NaBHT, coupled with the anti-oxidant properties of its conjugate acid byproduct, BHT means the process seems to have no functional group incompatibilities. Highly effective coupling of base-sensitive and redox-active functional groups was observed in all cases with only 0.1–0.2 mol percent catalyst. Comparisons using the standard base for this reaction, KOtBu, led to poor couplings or complete degradation in most applications – only NaBHT works.