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Related Concept Videos

Preparation of Alkynes: Alkylation Reaction02:27

Preparation of Alkynes: Alkylation Reaction

Introduction
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.
Electrophilic Addition to Alkynes: Halogenation02:38

Electrophilic Addition to Alkynes: Halogenation

Introduction
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.
Alkynes to Aldehydes and Ketones: Hydroboration-Oxidation02:47

Alkynes to Aldehydes and Ketones: Hydroboration-Oxidation

Introduction
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.
Reduction of Alkynes to cis-Alkenes: Catalytic Hydrogenation02:24

Reduction of Alkynes to cis-Alkenes: Catalytic Hydrogenation

Introduction
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.
Radical Reactivity: Intramolecular vs Intermolecular01:33

Radical Reactivity: Intramolecular vs Intermolecular

Radical reactions can occur either intermolecularly or intramolecularly. In an intermolecular radical reaction, a nucleophilic radical adds to an electrophilic alkene or vice versa. In such reactions, the radical and generally the alkene, which is also called the radical trap, are two different molecules. Additionally, for such intermolecular reactions to occur, the radical trap must be active, present in an excess concentration, and the radical starting material must have a weak carbon–halogen...
Preparation of Alkynes: Dehydrohalogenation02:34

Preparation of Alkynes: Dehydrohalogenation

Introduction
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.

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Related Experiment Video

Updated: Jun 14, 2026

Metal-free Synthesis of Ynones from Acyl Chlorides and Potassium Alkynyltrifluoroborate Salts
09:58

Metal-free Synthesis of Ynones from Acyl Chlorides and Potassium Alkynyltrifluoroborate Salts

Published on: February 24, 2015

New xanthate-based radical cyclization onto alkynes.

Laurent El Kaïm1, Laurence Grimaud, Luis D Miranda

  • 1Laboratoire Chimie et Procédés, UMR 7652, Ecole Nationale Supérieure des Techniques Avancées, 32 Bd Victor, 75015 Paris, France. laurent.elkaim@ensta.fr

Chemical Communications (Cambridge, England)
|April 10, 2010
PubMed
Summary
This summary is machine-generated.

A novel reductive cyclization strategy overcomes limitations in radical cyclization for alkynes. This method efficiently synthesizes exomethylene lactams using xanthates derived from Ugi reactions.

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Solid-phase Synthesis of [4.4] Spirocyclic Oximes
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Metal-free Synthesis of Ynones from Acyl Chlorides and Potassium Alkynyltrifluoroborate Salts
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[(DPEPhos)(bcp)Cu]PF6: A General and Broadly Applicable Copper-Based Photoredox Catalyst
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Solid-phase Synthesis of [4.4] Spirocyclic Oximes
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Solid-phase Synthesis of [4.4] Spirocyclic Oximes

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Area of Science:

  • Organic Chemistry
  • Synthetic Chemistry

Background:

  • Radical cyclization involving xanthate transfer on alkynes presents challenges.
  • Existing methods often fail to achieve desired outcomes.

Purpose of the Study:

  • To develop a new reductive cyclization strategy for synthesizing exomethylene lactams.
  • To overcome the limitations of previous radical cyclization approaches.

Main Methods:

  • Utilized a stoichiometric amount of dilauroyl peroxide in isopropanol for reductive cyclization.
  • Prepared xanthate starting materials via a Ugi 4-component reaction with propargylamine.

Main Results:

  • Successfully achieved reductive cyclization of xanthates on alkynes.
  • Synthesized exomethylene lactams in good yields.
  • Demonstrated a viable alternative to failed radical cyclization pathways.

Conclusions:

  • The new reductive cyclization strategy is effective for synthesizing exomethylene lactams.
  • This approach provides a reliable method when traditional radical cyclizations fail.