Physical Sciences and Mathematics Commons^™

Studies Directed Toward The Synthesis Of Germacranolides Via [2+2] Cycloaddition Followed By Ring Expansion/Elimination Of Β-Lactones, Bryan E. Yates

Masters Theses

Exposure of α-trimethylsilyl β-lactones to magnesium bromide or boron trifluoride etherate in diethyl ether solvent resulted in the smooth generation of β,γ-unsaturated acid derivatives in good yield and isomeric purity. It is believed that this reaction occurs via the formation of a stable tertiary carbocation at the γ-carbon resulting from cleavage of the carbon-oxygen sigma bond due to the complexation of the Lewis acid with the ring oxygen atom. Rapid loss of an adjacent electrofuge then furnishes the unsaturated acids. The β-lactone precursors were prepared by a [2+2] cycloaddition of an aldehyde and an alkyl trimethylsilyl ketene. This method was …

Butenolide Synthesis Via Cation-Initiated Ring Expansion/Elimination Of Β-Lactones, Jianhua Huang

Masters Theses

An area of recent research in the Black research group is an exploration of the potential of cation-initiated β-lactone ring expansions, accompanied by the elimination of a proton or other electrofuge, as a protocol for the synthesis of multisubstituted butenolides.

Γ-Bromo β-lactones were prepared via bromolactonization of the appropriate β,Γ-unsaturated acids under basic conditions. The nucleofugal bromine atom on the Γ-carbon was then employed to effect carbocation formation adjacent to the lactone ring oxygen atom; the most efficacious reagent combination was found to be silver nitrate in refluxing acetic acid. Generation of this cation initiated a migration of the β-lactone …

A Novel Synthesis Of Cyclic And Acyclic 3-Alkenoic Acids Via Ionization/Elimination Of Β-Lactones, Stephen Lucas Maluleka

Masters Theses

Exposure of spiro β-lactones and 3-substituted 4,4-dialkyl oxetan-2-ones to magnesium bromide in diethyl ether solvent resulted in the smooth generation of β,γ-unsaturated acid derivatives in high yield and isomeric purity. It is believed that this reaction occurs via the formation of a stable tertiary carbocation at the β-carbon resulting from cleavage of the carbon-oxygen sigma bond due to the complexation of magnesium cation with the ring oxygen atom. Rapid loss of an adjacent proton then furnishes the unsaturated acids. The β-lactone precursors were prepared by the dehydration of β-hydroxy acid derivatives (obtained from the condensation of ketones with acetic acid …