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Updated: Sep 6, 2026

Metal-free Synthesis of Ynones from Acyl Chlorides and Potassium Alkynyltrifluoroborate Salts
Published on: February 24, 2015
Three-Component Difluoroalkylative Alkynylation of [3.1.1]Propellane Enables Modular Bicyclo[3.1.1]heptane Synthesis
Pan Huang1, Huifang Ma1, Lianmin Yang2
1School of Chemistry and Chemical Engineering, Yangzhou University, Siwangting Road 180, Yangzhou225002, China.
Abstract:
Bicyclo[3.1.1]heptane (BCHep) is a rigid three-dimensional bioisostere of meta-substituted benzene, yet functionalized derivatives remain scarce. We report a copper-promoted three-component difluoroalkylative alkynylation of [3.1.1]propellane with terminal alkynes and bromodifluoroacetates, enabling simultaneous installation of a gem-difluoro group and a versatile alkyne handle at the bridgehead. This one-step transformation provides modular access to difunctionalized BCHep scaffolds under mild conditions with broad functional group tolerance and offers opportunities for late-stage diversification of complex molecules.
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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.
Preparation of Alkynes: Dehydrohalogenation
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.
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.
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.
Nomenclature of Alkynes
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.