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Updated: Sep 18, 2025
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Electrochemical Synthesis of Disubstituted Alkynes from Dihydrazones
Subhabrata Dutta1, Jacob Kayser2, Siegfried R Waldvogel1,3
1Department of Electrosynthesis, Max-Planck-Institute for Chemical Energy Conversion, Stiftstraße 34-36, 45479 Mulheim an der Ruhr, Germany.
Abstract:
A simple, straightforward, scalable, and sustainable electrochemical transformation of dihydrazones to alkynes via anodic oxidation has been developed. The protocol operates under galvanostatic conditions in a commercially available undivided cell utilizing reusable carbon-based electrodes. This methodology enables the efficient synthesis of a broad range of alkynes with moderate to excellent yield. The successful demonstration of gram-scale synthesis, along with a consistent electrode reusability profile, underlines the synthetic utility and preparative potential of the approach.
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Related Concept Videos
02:34Preparation of Alkynes: Dehydrohalogenation
Alkynes can be prepared by dehydrohalogenation of vicinal or geminal dihalides in the presence of a strong base like sodium amide in liquid ammonia. The reaction proceeds with the loss of two equivalents of hydrogen halide (HX) via two successive E2 elimination reactions.
02:47Alkynes 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.
02:40Alkynes to Aldehydes and Ketones: Acid-Catalyzed Hydration
Analogous to alkenes, alkynes also undergo acid-catalyzed hydration. While the addition of water to an alkene gives an alcohol, hydration of alkynes produces different products such as aldehydes and ketones.
02:35Electrophilic Addition to Alkynes: Hydrohalogenation
02:38Electrophilic Addition to Alkynes: Halogenation
Halogenation is another class of electrophilic addition reactions where a halogen molecule gets added across a π bond. In alkynes, the presence of two π bonds allows for the addition of two equivalents of halogens (bromine or chlorine). The addition of the first halogen molecule forms a trans-dihaloalkene as the major product and the cis isomer as the minor product. Subsequent addition of the second equivalent yields the tetrahalide.
02:24Reduction of Alkynes to cis-Alkenes: Catalytic Hydrogenation
Like alkenes, alkynes can be reduced to alkanes in the presence of transition metal catalysts such as Pt, Pd, or Ni. The reaction involves two sequential syn additions of hydrogen via a cis-alkene intermediate.