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[摘要]：Studies on the phenylselenoetherification of some Delta(4)-alkenols in the presence of pyridine and some Lewis acids are described. All alkenols underwent intramolecular cyclization yielding corresponding tetrahydrofuran or tetrahydropyran derivatives. Yield and diastereomeric ratio of the cyclic products depend on counterion of selenylating reagent used. We found that external additives, such as pyridine and some Lewis acids coordinating to the electrophilic and/or nucleophilic species are used to control the course of cyclizations with high degrees of efficiency and improve the level of stereoinduction. |
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