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Published on: November 30, 2022
Copper-catalysed bromoalkynylation of arynes
Takami Morishita1, Hiroto Yoshida, Joji Ohshita
1Department of Applied Chemistry, Graduate School of Engineering, Hiroshima University, Higashi-Hiroshima 739-8527, Japan.
Copper catalysts enable arynes to insert into bromoalkyne C-Br bonds, yielding (alkynyl)bromoarenes. This provides a direct route for synthesizing these valuable organic compounds.
Area of Science:
- Organic Chemistry
- Catalysis
- Synthetic Methodology
Background:
- Arynes are highly reactive intermediates crucial in organic synthesis.
- Bromoalkynes are versatile building blocks containing both alkyne and carbon-bromine functionalities.
- Copper catalysis is widely employed for facilitating various organic transformations.
Purpose of the Study:
- To develop a novel synthetic method for preparing (alkynyl)bromoarenes.
- To investigate the insertion of arynes into the C(sp)-Br sigma-bond of bromoalkynes.
- To explore the utility of copper catalysts in this transformation.
Main Methods:
- Reaction of arynes with bromoalkynes.
- Utilization of a copper catalyst.
- Purification and characterization of the resulting products.
Main Results:
- Successful insertion of arynes into the C(sp)-Br sigma-bond of bromoalkynes was achieved.
- The reaction proceeded in a straightforward manner under copper catalysis.
- (Alkynyl)bromoarenes were obtained in good yields.
Conclusions:
- A new and efficient method for synthesizing (alkynyl)bromoarenes has been established.
- Copper-catalyzed aryne insertion into bromoalkynes offers a valuable synthetic strategy.
- This methodology expands the toolkit for constructing complex organic molecules.
Related Concept Videos
Alkynes 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.
Electrophilic 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.
Reduction 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.
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Preparation 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.
Radical Substitution: Allylic Bromination
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