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Updated: Aug 18, 2026

A Two-Step Protocol for Umpolung Functionalization of Ketones Via Enolonium Species
Published on: August 16, 2018
Deconjugative conversion of alpha-alkynyl esters to alpha,alpha-disubstituted beta-alkynyl esters
Salvatore D Lepore1, Yuanjun He
1Department of Chemistry, Florida Atlantic University, Boca Raton, FL 33431-0991, USA. slepore@fau.edu
Abstract:
We report the development of a method for the conversion of a variety of conjugated alpha-alkynyl esters to alpha,alpha-disubstituted beta-alkynylesters through the use of strong amide bases. Studies indicate that the second equivalent of base leads to the dianion intermediate. Optimal conditions included the use of 2 equiv of lithium diisopropylamide in THF with HMPA as the cosolvent followed by trapping with a variety of carbon electrophiles. Trapping with bis-electrophiles leads to spiro cycloalkane products.
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Alkynes to Aldehydes and Ketones: Hydroboration-Oxidation
One of the convenient methods for the preparation of aldehydes and ketones is via hydration of alkynes. Hydroboration-oxidation of alkynes is an indirect hydration reaction in which an alkyne is treated with borane followed by oxidation with alkaline peroxide to form an enol that rapidly converts into an aldehyde or a ketone. Terminal alkynes form aldehydes, whereas internal alkynes give ketones as the final product.

