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Updated: Jun 10, 2026

Metal-free Synthesis of Ynones from Acyl Chlorides and Potassium Alkynyltrifluoroborate Salts
Published on: February 24, 2015
Differentiating mechanistic possibilities for the thermal, intramolecular [2 + 2] cycloaddition of allene-ynes
Matthew R Siebert1, Joshua M Osbourn, Kay M Brummond
1Department of Chemistry, University of California-Davis, One Shields Avenue, Davis, California 95616, USA.
Abstract:
Intramolecular [2 + 2] cycloaddition reactions of allene-ynes offer a quick and efficient route to fused bicyclic ring structures. Insights into the mechanism and regiochemical preferences of this reaction are provided herein on the basis of the results of quantum chemical calculations (B3LYP/6-31+G(d,p)) and select experiments; both indicate that the reaction likely proceeds through a stepwise diradical pathway where one radical center is stabilized through allylic delocalization. The influences of the length of the tether connecting the alkyne and allene and substituent effects are also discussed.
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