Microwave‐Assisted Copper Promoted N‐Arylation of Amines with Aryl Boronic Acids/Salts on a KF–Alumina Surface

Abstract

An experimentally simple microwave‐assisted solvent‐free N‐arylation of primary amines with sodium tetraphenylborate or arylboronic acids, promoted by inexpensive cupric acetate, on the surface of KF–alumina is reported. The reaction is selective for mono‐N‐arylation, and a variety of functional groups are tolerated in the process.

Keywords:

• N‐Arylation
• Cupric acetate
• Tetraphenylborate salt
• Arylboronic acids
• KF–alumina
• Microwaves

Acknowledgment

We gratefully acknowledge financial assistance from the Department of Science and Technology, New Delhi (Grant No. SP/S1/G13/97). P.D. is a Junior Research Fellow under this project.

Notes

^aRepresentative experimental procedure: A mixture of p‐bromoaniline (172 mg, 1 mmol), phenylboronic acid (244 mg, 2 mmol), and anhydrous cupric acetate (200 mg, 1 mmol) was intimately mixed with KF–alumina9a (1 g) and irradiated using a household microwave oven at 160 W for 10 min. After cooling, the solid mass was placed on a column of silica gel and eluted with petroleum‐ether:ethyl acetate (49:1) to afford (p‐bromophenyl)phenylamine as colorless flakes (181 mg, 73%); m.p. 84–86°C; ¹H‐NMR (CDCl₃, 300 MHz): δ 6.88 (d, 2H, J = 8.8 Hz), 6.87–6.93 (m, 1H), 6.99–7.02 (m, 2H), 7.20 (d, 2H, J = 8.8 Hz), 7.18–7.29 (m, 2H); ¹³C‐NMR (CDCl₃, 75 MHz): δ 114.7, 120.1, 120.9, 123.6, 131.0, 131.1, 133.8, 143.7.