Iodine-Mediated Solvent-Controlled Selective Electrophilic Cyclization and Oxidative Esterification of o-Alkynyl Aldehydes: An Easy Access to Pyranoquinolines, Pyranoquinolinones, and Isocumari

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• 作者：Akhilesh K. Verma ; Vineeta Rustagi ; Trapti Aggarwal ; Amit P. Singh
• 刊名：Journal of Organic Chemistry
• 出版年：2010
• 出版时间：November 19, 2010
• 年：2010
• 卷：75
• 期：22
• 页码：7691-7703
• 全文大小：1128K
• 年卷期：v.75,no.22(November 19, 2010)
• ISSN：1520-6904

文摘

Chemoselective behavior of iodine in different solvents in the electrophilic iodocyclization of o-alkynyl aldehydes is described. o-Alkynyl aldehydes 3a−t on reaction with I₂ in CH₂Cl₂ with appropriate nucleophiles provides pyrano[4,3-b]quinolines 4a−f, via formation of cyclic iodonium intermediate Q; however, using alcohols as a solvent as well as nucleophile, o-alkynyl esters 5a−y were obtained selectively in good to excellent yields via formation of hypoiodide intermediate R. Subsequently, o-alkynyl esters were converted in to pyranoquinolinones 6a−i and isocoumarin 6j by electrophilic iodocyclization. This developed oxidative esterification provides a novel access for the chemoselective synthesis of esters 5q−u from aldehydes 3n−p without oxidizing primary alcohol present in the substrate.