Palladium-Catalyzed N-Arylation of Bis(ortho-substituted aryl)amines: an Efficient Method for Preparing Sterically Congested Triarylamines

Abstract

Bis(ortho-substituted aryl)amines were arylated on the nitrogen atom with various haloarenes in high yields using the palladium catalyst, which was generated from palladium(II) acetate and tri(tert-butyl)phosphine.

Key words

amination - arylation - cross-coupling - homogeneous catalysis - palladium

References and Notes

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17

Typical Procedure for the N-Arylation of Bis( ortho -substituted aryl)amines 2
Under a nitrogen atmosphere, a haloarene 1 or 4 (1.5 mmol) was added to a mixture of (t-Bu)₃P (4.1 mg, 20 µmol), Pd(OAc)₂ (2.2 mg, 10 µmol), NaOt-Bu (144 mg, 1.5 mmol), and a diarylamine 2 (1.0 mmol) in toluene (2.0 mL). The reaction mixture was stirred at 120 ˚C for 2-24 h, cooled to r.t., diluted with H₂O, and then extracted with EtOAc. The combined organic layer was washed with brine, dried over Na₂SO₄, and then evaporated under reduced pressure. The residue was purified with a flash column chromatography (EtOAc-hexane) to give the desired triarylamine 3.

22

The competitive experiment using an equimolar mixture of 1g and 1i afforded 3g and 3i by a ratio of 48:52. See details in the Supporting Information.

23

The competitive experiment using an equimolar mixture of 2a and 2c afforded 3a and 3k by a ratio of 32:68. See details in the Supporting Information.