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Updated: Aug 8, 2026

A Two-Step Protocol for Umpolung Functionalization of Ketones Via Enolonium Species
Published on: August 16, 2018
Competing isomerizations: a combined experimental/theoretical study of phenylpentenone isomerism
Zhongyi Wang1, Andrew G H Wee, Steven S Hepperle
1Department of Chemistry and Biochemistry, University of Regina, Regina, Saskatchewan S4S 0A2, Canada.
Abstract:
The possible competition of Z/E versus hydrogen-shift isomerization in (E)-5-phenyl-3-penten-2-one (E-1) and (E)-5-phenyl-4-penten-2-one (E-2) was studied, both experimentally and theoretically. Iodine-catalyzed isomerization experiments and computational modeling studies show that the equilibrated system consists predominantly of E-1 and E-2, with E-2 in moderate excess, and with no detectable amounts of the Z (cis) diastereoisomers. Density functional theory (DFT) calculations corroborated the free energy difference (Delta(r) and Delta(r) were -0.7 and -1.1 kcal mol(-1), respectively), and computations of Boltzmann-weighted (1)H NMR spectra were found to be useful in confirming the assignment of the isomers. The relevance of this equilibrium to earlier work on double-bond stabilization is discussed.
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