Experimental and computational studies have consistently indicated that direct transmetalation of the organic group from a boronic acid to a palladium halide complex occurs with impractical energy barriers. As a consequence, stoichiometric activators, most typically a base, are generally needed to accelerate transmetalation in catalytic processes. Evidence will be presented that this elementary step can in fact occur directly and rapidly at room temperature. Key to this development is the high reactivity inherent to low-coordinate Pd complexes ligated by tri(1-adamantyl)phosphine. Experimental data establish a distinct mechanistic pathway for these transmetalation reactions that does not involve a nucleophilic intermediate. Efforts to exploit this transmetalation process in a catalytic context will also be described for direct Suzuki-Miyaura coupling with acutely base-sensitive polyfluoroarylboronic acids that rapidly decompose by protodeboronation under classic coupling conditions.<br/>

Direct boronic acid transmetalation to a Pd(II) halide

254th National Meeting (2017)

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