An aerobic linear allylic C—H amination reaction under Pd(II) catalysis is reported, which makes use of an O<sub>2</sub> coupled multistep electron transfer platform. Through the intermediacy of a cobalt co-catalyst that reacts selectively with O<sub>2</sub>, catalytic quantities of Pd-selective benzoquinone oxidant (BQ) are used to affect Pd(0)/Pd(II) turnover. With this new system, dramatic decreases in Pd(II) catalyst loadings are now possible (from 10 mol% down to 5-2.5 mol%), while maintaining efficient reactivity and higher or comparable yields of C—H aminated products as compared to previous systems operating under higher catalyst loadings and stoichiometric BQ. Additionally, these reactions are performed under mild conditions of temperature and pressure, and require only one equivalent of terminal olefin substrate. Kinetic experiments aimed at understanding this improved reaction efficiency have demonstrated that the initial rate of the reaction decreases as the concentration of BQ is increased. These results suggest an inhibitory effect wherein elevated concentrations of BQ may compete for key ligand/substrate binding and prevent efficient catalysis.

Efficient aerobic linear allylic C-H amination: Overcoming benzoquinone inhibition

251st National Meeting (2016)

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