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Updated: Jun 13, 2026
Efficient Construction of Drug-like Bispirocyclic Scaffolds Via Organocatalytic Cycloadditions of α-Imino γ-Lactones and Alkylidene Pyrazolones
Published on: February 7, 2019
Facile Assembly of Structurally Diverse 2H-Pyrans Enabled by Chloropalladation-Initiated Carboetherification of
Fanghua Mao1, Bowen Wang1, Zhengwang Chen2
1Key Laboratory of Functional Molecular Engineering of Guangdong Province, School of Chemistry and Chemical Engineering, South China University of Technology, Guangzhou 510640, China.
Abstract:
3,6-Dihydro-2H-pyran heterocyclic framework is one of the currently developed heterocyclic building blocks in both pharmaceutical chemistry and organic synthesis, but with significant challenges. To overcome these challenges, herein, we report a robust synthetic methodology of palladium-catalyzed carboetherification of alkenes with alkynols for accessing polyfunctionalized 3,6-dihydro-2H-pyrans under aerobic oxidative conditions. In particular, this synthetic approach features excellent functional group compatibility, mild reaction conditions, and good step- and atom-economy. Additionally, an array of functional groups such as halogen group, ester, nitrile, aldehyde, phenoxy, and aromatic heterocycles were nicely tolerated, affording the synthetically challenging 2H-pyran derivatives in moderate-to-good yields. Notably, the practicability of this protocol is further verified by gram-scale synthesis and the late-stage diversification of pharmaceuticals and biologically active molecules.
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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.
02:24Reduction 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.
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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.
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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.