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Updated: Apr 15, 2026

Preparation of a Corannulene-functionalized Hexahelicene by CopperI-catalyzed Alkyne-azide Cycloaddition of Nonplanar Polyaromatic Units
Published on: September 18, 2016
Gold-catalyzed intermolecular annulations using alkynes as two-carbon synthons for the construction of aromatic and
Xiao-Qian Zhang1, Ningbo Li1, Pathan Mosim Amin1
1School of Chemistry, MOE Key Laboratory for Nonequilibrium Synthesis and Modulation of Condensed Matter, Xi'an Key Laboratory of Sustainable Energy Materials Chemistry, Xi'an Jiaotong University (XJTU), Xi'an, 710049, China. yongliangzhang@xjtu.edu.cn.
Abstract:
Gold-catalyzed intermolecular annulations employing alkynes as two-carbon synthons provide a powerful strategy for the modular construction of both aromatic and non-aromatic ring systems. These transformations typically proceed under mild conditions with high selectivity, enabling efficient and predictable access to a broad range of complex heterocycles, including pyrroles, indoles, quinolines, carbazoles, furans, oxazoles, and other azole derivatives, as well as saturated and partially unsaturated heterocycles such as dihydrofurans, and tetrahydropyridine frameworks. This Feature Article summarizes and reviews the representative work in this flourishing field, with emphasis on reaction design, mechanistic insights, and selectivity control, and highlights the broad synthetic potential of these processes. Despite significant advances, challenges remain, particularly the limited number of asymmetric variants and the underexplored non-aromatic scaffolds, highlighting opportunities for further development.
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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.
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.
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.
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.
Electrophilic Addition to Alkynes: Hydrohalogenation
Nucleophilic Aromatic Substitution: Elimination–Addition
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