Versatile Catalysts for the Suzuki Cross-Coupling of Arylboronic Acids with Aryl and Vinyl Halides and Triflates under Mild Conditions
Through the use of Pd 2 (dba) 3 /P( t -Bu) 3 as a catalyst, a wide range of aryl and vinyl halides, including chlorides, undergo Suzuki cross-coupling with arylboronic acids in very good yield, typically at room temperature; through use of Pd(OAc) 2 /PCy 3, a diverse array of aryl and vinyl triflates react cleanly at room temperature. Together, these two catalyst systems cover a broad spectrum of commonly encountered substrates for Suzuki couplings. Furthermore, they display novel reactivity patterns, such as the selective cross-coupling by Pd 2 (dba) 3 /P( t -Bu) 3 of an aryl chloride in preference to an aryl triflate, and they can be used at low loading, even for reactions of aryl chlorides. Preliminary mechanistic work indicates that a palladium monophosphine complex is the active catalyst in the cross-coupling of aryl halides.