Date of Graduation
Master of Science in Chemistry
DFT, gold (III), propargylic acetate, carene, natural products
Organic Chemistry | Physical Chemistry
Propargylic acetates can lead to complex transformations upon exposure to a gold catalyst. Gold catalyzed transformations also allow for simple synthesis of a number of natural products. Gold (III)-cycloisomerization of a 5-acetoxy-1,6-enyne is reported to proceed through two pathways that differ in the order of major events: cyclization followed by ester migration (“cyclization first”) or the reverse (“migration first”). Both pathways could theoretically proceed in either order. This rearrangement is called the Ohloff-Rautenstrauch rearrangement and has high regio- and stereocontrol affording a bicylo[4.1.0]heptane carbon substructure. This rearrangement allows for the synthesis of the carene class of natural products. Computational modeling determining the mechanism and preference for the pathways in the gas- and solvent-phase (dichloroethane, IEFPCM) are described herein. Structures for the pathways are found using the B2PLYP/6-31G(d)-LANL2DZ model chemistry while energies are found at the B2PLYP-D3/def2TZVP//B2PLYP/6-31G(d)-LANL2DZ level. Both pathways feature multiple steps with low energy barriers. Highest-energy structures for both pathways are close in energy (ΔΔE‡ = 2.8 kcal/mol for solvent phase). Turnover frequency for each pathway are calculated suggesting that the cyclization first pathway may dominate.
© Jeremy M. Hines
Hines, Jeremy M., "Electronic Structure Evaluation of Competing Pathways in the Gold(III)-Catalyzed Ohloff-Rautenstrauch Cyclosimerization Converting Propargylic Acetates to Carene-like Natural Products" (2017). MSU Graduate Theses. 3111.