Abstract
In nature, chrysanthemum flowers naturally produce pyrethrin, a naturally occurring insecticide. A key feature of its chemical structure is a three-membered ring called cyclopropane. Synthesizing cyclopropane rings in the laboratory presents challenges, as a catalyst is required to facilitate the reaction. As a metal catalyst, dirhodium(II) tetraacetate has been used since 1976. Based on the structure of rhodium acetate bis-tolunitrile, one compound has a methyl group in the meta position and the other has a methyl in the para position. The hypothesis was that the meta-tolunitrile complex would facilitate the synthesis of cis-cyclopropane over trans-cyclopropane. The two isomers of rhodium acetate tolunitrile were synthesized by reacting rhodium acetate with meta-tolunitrile or para-tolunitrile in an alcoholic solution. The resulting rhodium acetate bis-tolunitrile product crystallized out of solution. These dirhodium compounds were used as catalysts for cyclopropanation reactions using ethyl diazoacetate and styrene. The resulting cyclopropane products were analyzed using GC-MS. We discovered that the meta-tolunitrile and para-tolunitrile adducts yielded identical cis and trans percentages. Furthermore, a blank control reaction performed without the dirhodium complex yielded the same results. This suggests that the reaction proceeds via a thermal pathway under these conditions, and that the axial nitrile ligands do not provide a detectable electronic benefit to the stereoselectivity.
Start Time
15-4-2026 9:00 AM
End Time
16-4-2026 10:00 AM
Room Number
219
Presentation Type
Oral Presentation
Presentation Subtype
UG Orals
Presentation Category
Science, Technology, and Engineering
Student Type
Undergraduate Student
Faculty Mentor
Sandy Eagle
Synthesis and Evaluation of Dirhodium(II) Acetate Tolunitrile Complexes as Catalysts in Cyclopropanation Reactions
219
In nature, chrysanthemum flowers naturally produce pyrethrin, a naturally occurring insecticide. A key feature of its chemical structure is a three-membered ring called cyclopropane. Synthesizing cyclopropane rings in the laboratory presents challenges, as a catalyst is required to facilitate the reaction. As a metal catalyst, dirhodium(II) tetraacetate has been used since 1976. Based on the structure of rhodium acetate bis-tolunitrile, one compound has a methyl group in the meta position and the other has a methyl in the para position. The hypothesis was that the meta-tolunitrile complex would facilitate the synthesis of cis-cyclopropane over trans-cyclopropane. The two isomers of rhodium acetate tolunitrile were synthesized by reacting rhodium acetate with meta-tolunitrile or para-tolunitrile in an alcoholic solution. The resulting rhodium acetate bis-tolunitrile product crystallized out of solution. These dirhodium compounds were used as catalysts for cyclopropanation reactions using ethyl diazoacetate and styrene. The resulting cyclopropane products were analyzed using GC-MS. We discovered that the meta-tolunitrile and para-tolunitrile adducts yielded identical cis and trans percentages. Furthermore, a blank control reaction performed without the dirhodium complex yielded the same results. This suggests that the reaction proceeds via a thermal pathway under these conditions, and that the axial nitrile ligands do not provide a detectable electronic benefit to the stereoselectivity.
