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Updated: May 22, 2025

Facile Preparation of 2Z,4E-Dienamides by the Olefination of Electron-deficient Alkenes with Allyl Acetate
Published on: June 21, 2017
Catalytic Schmittel-Type [2+2] Cycloaddition of γ-Alkynyl Diazoacetates with Terminal Alkynes for Accessing
Hao Wei1, Yan Zhang1, Nan-Nan Wang1
1School of Chemistry & Materials Science, Jiangsu Normal University, Xuzhou 221116, China.
Abstract:
Instead of the conventional [4+2] cycloaddition, a regioselective Schmittel-type [2+2] cycloaddition of yne-allene esters, generated in situ from copper-catalyzed dediazotized coupling of γ-alkynyl diazoacetates with terminal alkynes, is reported, enabling a bicyclization process to produce a diverse array of C1-arylated cyclobuta[a]indenes in moderate to good yields. The protocol features wide functional group compatibility, mild reaction conditions, and experimental simplicity, holding significant potential for building new tricyclic cyclobutenes.
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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.
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.