Synlett 2011(12): 1769-1773  
DOI: 10.1055/s-0030-1260932
LETTER
© Georg Thieme Verlag Stuttgart ˙ New York

Synthesis of Tetra-ortho-Substituted Biaryls Using Aryltriolborates

Gao-Qiang Li, Yasunori Yamamoto*, Norio Miyaura
Division of Chemical Process Engineering, Graduate School of Engineering, Hokkaido University, Sapporo 060-8628, Japan
Fax: +81(11)7066560; e-Mail: yasuyama@eng.hokudai.ac.jp;
Further Information

Publication History

Received 11 April 2011
Publication Date:
05 July 2011 (online)

Abstract

Tetra-ortho-substituted biaryls were synthesized by cross-coupling between 2,6-disubstituted bromoarenes and aryltriolborates possessing substituents at ortho carbon. The use of a copper(I) halide such as CuCl (20 mol%) with a palladium catalyst was found to be highly effective to give such sterically hindered biaryls in good yields.

22

General Procedure for the Synthesis of ortho -Substituted Biaryls
The aryl bromide (0.5 mmol), aryl triolborate (0.75 mmol), Pd(OAc)2 (5 mol%), BIPHEP (5.5 mol%), and CuCl (0.1 mmol) were placed in a flash under nitrogen atmosphere. Anhyd DMF (5 mL) was added. The mixture was stirred at 80 ˚C for 14 h. After cooling to r.t., the crude mixture was filtered through a plug of Celite and washed with Et2O. The filtrate was then concentrated in vacuo to afford the crude product, which was further purified by chromatography on silica gel with hexanes-EtOAc (99:1 to 10:1).