Convenient and Highly Efficient Routes to 2
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‐Chromene and 4‐Chromanone Derivatives: Iodine‐Promoted and
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‐Toluenesulfonic Acid Catalyzed Cascade Cyclizations of Propynols
A convenient strategy is presented for the easy preparation of a series of 2H‐chromenes under mild conditions through iodocyclization of readily accessible propynols. In addition, various 4‐chromanones can be synthesized through a p‐toluenesulfonicacidcatalyzedcascadecyclization with high efficiency (yields up to 99 %). Our developed reaction systems are proven to have good functional‐group applicability