Dirhodium(II) paddlewheel complexes have high utility in diazo-mediated cyclopropanation reactions and ethyl diazoacetate (EDA) is one of the most commonly used diazo compounds in this reaction. Despite its widespread usage, selectivity issues persist when EDA is used in cyclopropanation reactions. In this study, we report our efforts to use tethered thioether ligands to tune the reactivity and selectivity of Rh(II)-carbene mediated cyclopropanation of olefins with ethyl diazoacetate. Methods will be described that enabled the synthesis of a family of achiral and chiral Rh(II) complexes in which tethered thioether moieties were coordinated to axial sites of the complex. The complexes were then used in EDA-mediated cyclopropanation reactions in order to (1) minimize deleterious diazo dimerization, (2) allow the use of equimolar amounts of EDA and olefin, and (3) enhance asymmetric induction. Spectroscopic investigation, structure-activity correlation studies, and computational analysis provided insight into the role that tethered axial coordination plays in the reaction.

Tuning Rh(II) catalysts through tethered axial coordination: Towards selective Rh(II)-catalyzed cyclopropanation with ethyl diazoacetate

ACS Fall 2021

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