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Updated: Feb 4, 2026

Preparation of SNS CobaltII Pincer Model Complexes of Liver Alcohol Dehydrogenase
Published on: March 19, 2020
Regiocontrol in the cobalt-catalyzed hydrosilylation of alkynes
Guojiao Wu1, Uttam Chakraborty, Axel Jacobi von Wangelin
1Department of Chemistry, University of Hamburg Martin Luther King Pl. 6, 20146 Hamburg, Germany. axel.jacobi@uni-hamburg.de.
Abstract:
Hydrofunctionalizations of unsaturated hydrocarbons are key strategies for the synthesis of functionalized building blocks. Here, we report highly versatile cobalt-catalyzed hydrosilylations of alkynes that operate with minute amounts of the inexpensive, bench-stable pre-catalyst Co(OAc)2·4H2O under mild conditions (0.1-1 mol%, THF, r.t., 1 h). Near-perfect regiocontrol/stereocontrol was induced by the choice of the ligand: bidentate phosphines afforded (E)-β-vinylsilanes; α-vinylsilanes formed with bipyridine ligands.
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Alkynes 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.
Nomenclature of Alkynes
Acid-Catalyzed Ring-Opening of Epoxides
Base-Catalyzed Ring-Opening of Epoxides
Acidity of 1-Alkynes
The acidic strength of hydrocarbons follows the order: Alkynes > Alkenes > Alkanes. The strength of an acid is commonly expressed in units of pKa — the lower the pKa, the stronger the acid. Among the hydrocarbons, terminal alkynes have lower pKa values and are, therefore, more acidic. For example, the pKa values for ethane, ethene, and acetylene are 51, 44, and 25, respectively, as shown here.
Preparation 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.