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Updated: Dec 29, 2025
Facile Preparation of 2Z,4E-Dienamides by the Olefination of Electron-deficient Alkenes with Allyl Acetate
Published on: June 21, 2017
Dehydrative Cross-Coupling of Allylic Alcohols with Alkynes
Peizhong Xie1, Zuolian Sun1, Shuangshuang Li1
1School of Chemistry and Molecular Engineering, Institute of Advanced Synthesis , Nanjing Tech University , Nanjing 211816 , P. R. China.
Abstract:
A highly efficient Pd/Ca catalytic system for the directly dehydrative cross-coupling of allylic alcohols with terminal alkynes was developed. This calcium salt cocatalyst facilitates the oxidative addition of the palladium catalyst (1 mol %) to the C-OH bond. Then, the in situ-generated hydroxide ion deprotonates the terminal alkynes to promote the formation of the allylalkynylpalladium intermediate, liberating water as the only byproduct. This proposed mechanism is also supported by density functional theory calculations. An anticancer agent was prepared from inexpensive starting materials on a 10 g scale.
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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.
02:35Acid-Catalyzed Dehydration of Alcohols to Alkenes
02:34Preparation 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.
02:24Reduction 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.
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.