Resumen de Exploiting Carvone To Demonstrate Both Stereocontrol and Regiocontrol: 1,2- vs 1,4-Addition of Grignard Reagents and Organocuprates
Thai Phat Truong, Sophia J. Bailey, Alexandra E. Golliher, Erika Y. Monroy, Uttar K. Shrestha, William A. Maio
The ability of certain organometallic reagents to react via 1,2- or 1,4-addition to an α,β-unsaturated ketone is a fundamental example of regioselectivity at the second-year undergraduate organic level. The following two experiments were designed to demonstrate this preference by exploiting carvone as an inexpensive chiral, nonracemic substrate. The first, intended for a typical undergraduate audience, makes use of phenylmagnesium bromide; the second calls for the manufacture of lithium dimethylcuprate from a stock solution of methyl lithium and copper(I) iodide and is envisioned to be carried out by upper-division students. Importantly, due to the chiral nature of carvone, these addition reactions are highly stereoselective and will provide an opportunity for students to revisit stereochemistry. Also discussed are several thoughts on assessment of student learning as well as an easy to adopt protocol that details reaction setup, aqueous workup, purification, waste management, and the analysis of products using 1H NMR spectroscopy.
