Economical and Readily Accessible Preparation of ,-Disubstituted Arylboronates through Palladium-Catalyzed Borylation of Haloarenes.

Miyaura borylation, that is, palladium-catalyzed cross-coupling between bromoarenes and diboron, offers a versatile method for preparing arylboronates; however, a costly and inaccessible catalyst has been required for synthesizing highly congested arylboronates with the method. Here the Pd(OAc)-tri(4-methoxyphenyl)phosphine catalyst was found to work as an efficient catalyst for the sterically demanding borylation. A broad range of ,-disubstituted bromoarenes were converted into the corresponding arylboronates in high yields by using the palladium catalyst with CsCO in EtOAc at 80 °C.