Convenient and Highly Efficient Routes to 2 H‐Chromene and 4‐Chromanone Derivatives: Iodine‐Promoted and p‐Toluenesulfonic Acid Catalyzed Cascade Cyclizations of Propynols |
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Authors: | Dr Yi‐Feng Qiu Yu‐Ying Ye Xian‐Rong Song Xin‐Yu Zhu Fang Yang Bo Song Jia Wang Hui‐Liang Hua Yu‐Tao He Ya‐Ping Han Xue‐Yuan Liu Prof Dr Yong‐Min Liang |
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Institution: | State Key Laboratory of Applied Organic Chemistry, Lanzhou University, Lanzhou 730000 (China) |
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Abstract: | A convenient strategy is presented for the easy preparation of a series of 2 H‐chromenes under mild conditions through iodocyclization of readily accessible propynols. In addition, various 4‐chromanones can be synthesized through a p‐toluenesulfonic acid catalyzed cascade cyclization with high efficiency (yields up to 99 %). Our developed reaction systems are proven to have good functional‐group applicability and can be scaled up to gram quantities in satisfactory yields. These systems also provide a new synthetic strategy for two types of important flavonoid skeleton without using costly and toxic metal catalysts. Additionally, the resulting halides could be further exploited in subsequent palladium‐catalyzed coupling reactions, so these compounds could act as potential intermediates for the construction of some valuable drug molecules. |
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Keywords: | Brø nsted acids cyclization flavonoids iodine propynols synthetic methods |
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