Degree Name
Master of Science (MS)
Semester of Degree Completion
1992
Thesis Director
T. Howard Black
Abstract
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 ring oxygen atom to the Γ-position, whereupon loss of the α-proton produced butenolides in 30 to 75% yield.
Successful implementation of this conceptually novel strategy will provide a versatile and expedient route for the synthesis of butenolides bearing a wide range of substitution patterns.
Cycloaddition of α-trimethylsilylketene (TMS ketene) to aldehydes bearing carbocation progenitors in the α-position provided α-trimethylsilyl β-lactones which were then examined as substrates for the ring expansion/elimination sequence. In contrast to aldehydes, ketones were transformed into α,β-unsaturated acids under the same conditions.
Recommended Citation
Huang, Jianhua, "Butenolide Synthesis via Cation-Initiated Ring Expansion/Elimination of β-Lactones" (1992). Masters Theses. 1970.
https://thekeep.eiu.edu/theses/1970
