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Updated: Apr 24, 2026

A Two-Step Protocol for Umpolung Functionalization of Ketones Via Enolonium Species
Published on: August 16, 2018
Annulation reactions of allenyl esters: an approach to bicyclic diones and medium-sized rings
Bilal A Bhat1, Samantha L Maki, Elijah J St Germain
1Medicinal Chemistry Division, Indian Institute of Integrative Medicine (CSIR) , Sanatnagar, Srinagar-190005, India.
Abstract:
A flexible approach to construct sterically congested bicyclo-alkenedione frameworks is reported. Under the action of potassium carbonate, α-sulphonyl cycloalkanones are added to functionalized allenyl esters, leading to a lactone intermediate that is subsequently reduced to initiate an intramolecular aldol cyclization to [3.2.1], [3.3.1], and [4.3.1] bicycles. Oxidation then affords bicyclic diones in good three-step yields. Under exceptionally mild conditions, these bicycles are converted to highly functionalized medium-sized rings through a Grob-type fragmentation.
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