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Updated: Jun 12, 2025
Imine Metathesis by Silica-Supported Catalysts Using the Methodology of Surface Organometallic Chemistry
Published on: October 18, 2019
Unconventional Insertions of Internal Alkynes into a Mixed-Valent Silaiminyl-Silylene
Da Jin1, Xiaofei Sun1, Alexander Hinz1
1Institute of Inorganic Chemistry (AOC), Karlsruhe Institute of Technology (KIT), Kaiserstr. 12, Karlsruhe 76131, Germany.
Abstract:
The reactivity of a mixed-valent silaiminyl-silylene [LSi-Si(NDipp)L] (L = PhC(NBu)2, Dipp = 2,6-Pr-C6H3) toward various substituted internal alkynes was investigated. In contrast to previous reports that primarily yield [Si(μ-C2)Si]-modified rings via 1,2-addition of two silylenes in the center of the molecule, our study reveals a novel reaction pathway. The introduction of [R1-C≡C-R2] (R1 = Ph or SiMe3, R2 = Ph or C≡CSiMe3) gave unconventional insertion into one of the amidinate ligands, followed by migration of the {NBu} group to bridge two Si atoms. This results in the formation of diverse expanded silacycles.
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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.
02:39Nomenclature of Alkynes
02:27Preparation of Alkynes: Alkylation Reaction
Alkylation of terminal alkynes with primary alkyl halides in the presence of a strong base like sodium amide is one of the common methods for the synthesis of longer carbon-chain alkynes. For example, treatment of 1-propyne with sodium amide followed by reaction with ethyl bromide yields 2-pentyne.
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