Date of Graduation

Summer 2017

Degree

Master of Science in Chemistry

Department

Chemistry

Committee Chair

Matthew Siebert

Keywords

DFT, gold (III), propargylic acetate, carene, natural products

Subject Categories

Organic Chemistry | Physical Chemistry

Abstract

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.

Copyright

© Jeremy M. Hines

Open Access

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