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Updated: Oct 2, 2026
A Microwave-Assisted Direct Heteroarylation of Ketones Using Transition Metal Catalysis
Published on: February 16, 2020
Alkyne-Assisted Stereospecific Skeletal Rearrangement via Nonclassical Carbocations
Rajan Kumar Kharwar1, Kaushalendra Patel1, Noam Orbach1
1Schulich Faculty of Chemistry and the Resnick Sustainability Center for Catalysis, Technion-Israel Institute of Technology, Haifa, Israel.
Abstract:
We report stereospecific nucleophilic substitutions of homopropargylic alcohols enabled by anchimeric assistance from an alkyne. Upon activation, neighboring-group participation of the alkyne generates a nonclassical cyclopropylidenemethyl cation. The transformation provides access to densely-substituted tertiary homopropargyl fluorides with broad functional-group tolerance and efficient chirality transfer from enantioenriched alcohols. Computational studies support the involvement of the nonclassical cationic intermediate. The calculations further indicate that alkyne-derived nonclassical cations are less stabilized than their alkene analogues.
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02:34Regioselectivity and Stereochemistry of Acid-Catalyzed Hydration
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.
01:10α-Alkylation of Ketones via Enolate Ions
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.
02:27Preparation 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.
02:38Electrophilic 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.