The Photochemical Reactivity of Conjugated Enolates

The photochemical reactivity of conjugated enolates was investigated, transforming them from thermally reactive intermediates into photochemically active species. Chromoselective irradiation was employed to enable novel enolate-based transformations. A spontaneous dearomatising ring-closure, previously reported by the Clayden group, was leveraged to generate conjugated enolates in situ, which were irradiated to afford enantioselective cycloheptatrienes.

Photochemical benzyl migrations of acyclic trienolates were observed, yielding multiple regioisomers through radical mechanisms. Ring-contraction and migration of lactam enolates were also studied, affording substituted cyclopropanes and cyclobutanes in high yields and selectivities. Dienolates provided the cleanest and most efficient reactivity under mild irradiation.

Internal chromophore positioning in lactam systems led to electrocyclic ring openings instead of contractions, producing diverse stereoisomers. Preliminary work on quinoline- and pyrrole-based enolates was initiated, though successful reactivity was not yet achieved. Overall, new photochemical methodologies were developed, offering versatile routes to complex molecular architectures and expanding the synthetic utility of enolates.

• Mortimer, JE

• e University of Bristol

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