Description
Aniline, m-nitroaniline, p-chloroaniline, p-bromoaniline and o-bromoaniline were N-alkylated with octyl trifluoroborate in tert-butanol solvent. TLC, gas chromatograph and LCMS-MS helped to clarify the exist of the monosubstituted N-octylaniline products. The crude product was filtered and purified from column chromatography using diethyl ether and hexane solvent mixture (1:10) to isolate monosubstituted N-octylaniline products from the mixture of remained unreacted reactants. The monosubstituted N-octylaniline products were characterized by 1H, 13 C NMR and IR spectroscopy after purification. Based on previous literatures, the plausible mechanism was proposed. During the pre-stirring time, octyl trifluoroborate and cupric acetate were dissolved in the solvent. After stirring for a period of time, aniline was added to the reactants mixture and it generated copper(II) aniline species by the nucleophile coordination. And then, alkylcopper(II) aniline intermediate from cupric acetate and an octyl trifluoroborate was formed by transmetalation. After this step, during the remained reaction hours, oxidation and reductive elimination of the copper catalyst with air were performed to give the cross-coupling product. In this step, alkylcopper(II) aniline was oxidized to the corresponding alkylcopper(III) aniline by supply air or/and cupric acetate and then followed by reductive elimination which formed the copper(I) species and alkylaniline products. The yield of each product was various from 22% to 69% by the different substitute groups in aniline. The following reaction conditions were examined to improve the yield: reaction time, stoichiometry of reactants, order (of addition), temperature, catalysts, solvents, base and oxidants.
