Traditional approaches to the design of synthetically useful transition metal catalysts typically involve variation of ligand steric and electronic properties to fine tune catalyst activity (i.e. rate) and selectivity.  However, this approach can fail to promote one competing reaction pathway over another when the underlying chemical mechanisms are similar.  While investigating transformations of unsaturated molecules catalyzed by structurally tunable gold acyclic diaminocarbene (Au-ADC) complexes, we observed trends in reaction rate and selectivity that were best explained as the result of through-space electrostatic influences of ADC ligand substituents.  Significant effects on the rates of intermolecular alkyne hydroamination reactions and the selectivities of enyne cylizations were seen when the ADC ligand conformation permitted close approach of electron-poor arene rings to the gold center.  Similar through-space influences were found to enhance enantioselectivity in gold-catalyzed intramolecular cycloisomerizations of allenes containing internal nucleophiles.  Computational and experimental evidence to distinguish between through-bond electronic effects and through-space electrostatic effects will be presented.<br/>

Through-space ligand effects on reaction rate and selectivity in gold(acyclic diaminocarbene)-catalyzed organic transformations

255th National Meeting (2018)

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