title: Convenient and highly efficient routes to 2 H-chromene and 4-chromanone derivatives: iodine-promoted and p-toluenesulfonic acid catalyzed cascade cyclizations of propynols.
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.
authors.affiliation: State Key Laboratory of Applied Organic Chemistry, Lanzhou University, Lanzhou 730000 (China).
authors.forename: Yi-Feng
authors.initials: YF
authors.lastname: Qiu
authors.forename: Yu-Ying
authors.initials: YY
authors.lastname: Ye
authors.forename: Xian-Rong
authors.initials: XR
authors.lastname: Song
authors.forename: Xin-Yu
authors.initials: XY
authors.lastname: Zhu
authors.forename: Fang
authors.initials: F
authors.lastname: Yang
authors.forename: Bo
authors.initials: B
authors.lastname: Song
authors.forename: Jia
authors.initials: J
authors.lastname: Wang
authors.forename: Hui-Liang
authors.initials: HL
authors.lastname: Hua
authors.forename: Yu-Tao
authors.initials: YT
authors.lastname: He
authors.forename: Ya-Ping
authors.initials: YP
authors.lastname: Han
authors.forename: Xue-Yuan
authors.initials: XY
authors.lastname: Liu
authors.forename: Yong-Min
authors.initials: YM
authors.lastname: Liang
keywords: Brønsted acids; cyclization; flavonoids; iodine; propynols; synthetic methods