Page 1 - Organogold Reactivity with Palladium, Nickel, and Rhodium: Transmetalation, Cross-Coupling, and Dual Catalysis

Organogold Reactivity with Palladium, Nickel,
and Rhodium: Transmetalation, Cross-Coupling,

and Dual Catalysis

JOSHUA J. HIRNER, YILI SHI, AND SUZANNE A. BLUM*
Department of Chemistry, University of California, Irvine, California 92697-2025,
United States
RECEIVED ON FEBRUARY 26, 2011

CONSPECTUS

sing two transition metals to simultaneously catalyze a reaction can offer distinct opportunities for reactivity and selectivity
U when compared to using single-metal catalyst systems. Creating dual transition metal catalytic systems is complicated,
however, by challenges in predicting compatible reactivities and designing turnover pathways for both metals. In this Account, we
describe our development of dual-metal catalysis reactions involving gold and a second transition metal.
The unique rearrangement intermediates accessible through gold-only catalysis, which exploits the soft Lewis acidity of Au(I),
make gold an attractive partner for dual-metal catalysis reactions. Because of the complexity of achieving simultaneous turnover of
two catalysts and predicting compatibilities, our approach has been to first gain a fundamental understanding of the reactivity of
the two metals with each other, both in stoichiometric and monocatalyzed reactions. To this end, we have investigated the
combined reactivity of organogold compounds with palladium, nickel, and rhodium.
We narrate the intricacies of turning over two catalysts simultaneously and thereby illuminate the valuable role of fundamental
studies in identifying the optimal conditions to promote desirable two-metal reactivity and compatibility. Transmetalation, redox
reactivity, and new mechanisms for dual-metal catalytic turnover were probed from this standpoint. We have applied the
knowledge gained through these studies to the development of reactions that are dual-catalyzed by gold and palladium, as well as
nickel- and rhodium-catalyzed reactions of organogold compounds. More broadly, these new reactions expand the reactivity
available to catalytic organogold intermediates via trapping and functionalization reactions with other transition metals.
Our investigations reveal strategies useful for designing dual-metal reactions with gold. First, the versatility of gold as a
transmetalation partner suggests that many potential methods may exist to intercept catalytic organogold intermediates with a
second transition metal. Second, ligands on both metals should be selected carefully in order to prevent catalyst deactivation.
Finally, reactions must be designed such that any oxidative steps involving the second metal outcompete undesired reactions with
redox-active organogold compounds. We believe that the application of these principles will allow for the design of a diverse set of
dual-catalyzed functionalizations befitting the wide variety of gold-catalyzed transformations already established.

I. Introduction These rearrangement reactions make use of the soft Lewis
We have focused our efforts toward dual-catalyzed trans- acidity of gold(I) to install a wide range of molecular motifs.
formations 15 combining gold catalysis with the unique re- These gold-only catalyzed reactions proceed through a
6
activity of a second transition metal. Gold is an attractive common class of intermediates that contain goldcarbon
partner for dual-catalyzed reactions due to the unique rear- σ-bonds. 79 Despite the diversity of products accessible
rangementproductsaccessiblethroughgold-onlycatalysis. 79 with gold catalysis, the functionalization of the intermediate
Vol. 44, No. 8 ’ 2011 ’ 603–613 ’ ACCOUNTS OF CHEMICAL RESEARCH ’ 603
Published on the Web 06/06/2011 www.pubs.acs.org/accounts
10.1021/ar200055y & 2011 American Chemical Society