Dirhodium paddlewheel catalysts have seen extensive use in diazo-mediated reactions wherein they catalyze the formation of a cyclopropane group through a rhodium-carbene intermediate from an olefin. However, these reactions have been hindered by the 5-10 equivalents of olefin required for the reaction to give suitable yields, negating their use on more functionalized substrates. In this study, cyclopropanation of ethyl diazoacetate and one equivalent of styrene is accomplished using novel dirhodium paddlewheel catalysts containing an equatorial-axial ligand tether. Thiocarbamoyl benzoate (TCB) dirhodium paddlewheel complexes were synthesized and used in the cyclopropanation reaction, enabling the use of one equivalent while obtaining comparable yields and minimizing unwanted dimerization of the diazo. Reaction conditions were optimized to give the best possible yields and various functionalized substrates were screened with promising results. Using these novel dirhodium catalysts, diazo-mediated cyclopropanations may be conducted at a more efficient and economical rate.

Novel dirhodium paddlewheel catalysts: Synthesis and application towards diazo-mediated cyclopropanation reactions

2019 Spring National Meeting

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