Facile synthesis of highly functionalized six-membered heterocycles via PPh3-catalyzed [4+2] annulations of activated terminal alkynes and hetero-dienes: scope, mechanism, and application |
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| Authors: | Qiongmei Zhang |
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| Institution: | Key Laboratory for Advanced Materials and Institute of Fine Chemicals, East China University of Science and Technology, Shanghai 200237, China |
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| Abstract: | A novel 4+2] annulation between activated terminal alkynes and aza-dienes or oxo-dienes has been developed with the use of triphenylphosphine catalyst (20 mol %), which provides a facile method for synthesis of the corresponding highly functionalized dihydropyridines or dihydropyrans in good to excellent yields. The reaction mechanism has also been established, consisting formal hetero-Diels-Alder reaction catalyzed by PPh3 and 1,3]-proton transfer, which exhibits a large isotopic effect. |
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| Keywords: | PPh3 Catalysis Hetero-diene [4+2] Annulations Heterocycle H-Transfer |
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