Discovery and Development of a Three-Component Oxidopyrylium [5 + 2] Cycloaddition
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- 作者：Michael P. D’Erasmo ; Christine Meck ; Chad A. Lewis ; Ryan P. Murelli
- 刊名：Journal of Organic Chemistry
- 出版年：2016
- 出版时间：May 6, 2016
- 年：2016
- 卷：81
- 期：9
- 页码：3744-3751
- 全文大小：392K
- 年卷期：0
- ISSN：1520-6904
文摘
α-Hydroxy-γ-pyrone-based oxidopyrylium cycloaddition reactions are useful methods for accessing a highly diverse range of oxabicyclo[3.2.1]octane products. Intermolecular variants of the reaction require the formation of a methyl triflate-based pre-ylide salt that upon treatment with base in the presence of alkenes or alkynes leads to α-methoxyenone-containing bicyclic products. Herein, we describe our discovery that the use of ethanol-stabilized chloroform as solvent leads to the generation of α-ethoxyenone-containing bicyclic byproducts. This three-component process was further optimized by gently heating a mixture of a purified version of the oxidopyrylium dimer in the presence of an alcohol prior to addition of a dipolarophile. Using this convenient procedure, several new oxidopyrylium cycloaddition products can be generated in moderate yields. We also highlight the method in a tandem ring-opening/debenzylation method for the generation of α-hydroxytropolones.