Palladium(0) versus nickel(0) catalysis in selective functional-group-tolerant sp(3)-sp(3) carbon-carbon bond formations

Abstract

We have uncovered Pd(0)-catalyzed intermolecular nonsymmetrical Suzuki-Miyaura-type sp(3)-sp(3) C-C bond formations between allyl carbonates and nontoxic allyl, allenyl, or propargyl boronates. This report represents the first use of these types of boronic esters in this particular context. The present transformations proceeded with high selectivity under remarkably mild conditions, and various functional groups including an aldehyde function proved to be compatible. In addition, several boronates were found to display very unusual reactivity patterns; the higher reactivity of boron as apposed to silicon was clearly demonstrated as well. Finally, the inherent problem of beta-hydride elimination associated with intermediary allyl-Pd species was addressed by employing a commercially available Ni(0) catalyst.