DDQ-Mediated Oxidative [5+2] Cycloaddition Reactions of Isochroman-4-ones with Alkynes
Long Liang1, Sen Yang1, Xiao-Guo Zhang2
1School of Chemistry and Chemical Engineering, Hefei University of Technology, 193 Tunxi Road, Hefei 230009, China.
Abstract:
A DDQ (2,3-dichloro-5,6-dicyano-1,4-benzoquinone)-mediated oxidative [5+2] cycloaddition of isochroman-4-ones with alkynes has been described. This strategy provides an alternative method for the generation of the key benzopyrylium ylides as dipoles and affords structurally diverse benzo-fused 8-oxabicyclo[3.2.1]octanes in moderate to good yields. Mechanistic studies disclosed that the generation of benzopyrylium ylides is a radical-based process.
More Related Videos
Related Concept Videos
[4+2] Cycloaddition of Conjugated Dienes: Diels–Alder Reaction
Cycloaddition Reactions: Overview
Oxidation-Reduction Reactions
Cycloaddition Reactions: MO Requirements for Thermal Activation
Cycloaddition Reactions: MO Requirements for Photochemical Activation
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.


