Sodium dithionite initiated regio- and stereoselective radical addition of polyfluoroalkyl iodide with norbornene analogs |
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| Authors: | Fanhong Wu Fanhua Xiao Yongjia Shen |
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| Institution: | a College of Chemistry and Pharmaceutics, East China University of Science and Technology, Shanghai 200237, China
b Key Laboratory of Organofluorine Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, Shanghai 200032, China |
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| Abstract: | Sodium dithionite initiated free-radical addition of polyfluoroalkyl iodides (2m-2s) with norbornene 1a and its derivatives, such as norbornene-2-carboxylates 1b and 1c, and norbornene-2-carboxylic acids 1d and 1e was investigated. In all the cases, the addition of RF group was stereoselectively delivered at exo-position and the predominant configuration of products was trans. Under the similar condition, norbornene-2-carboxylic ethyl ester 1b reacted with 2p to give 6-exo-RF-5-endo-iodo adduct 3bp and 5-exo-RF-6-endo-iodo adduct 5bp in the ratio of 4:1. While 1c, which has a heavy crowded group in the 2-endo-position, gave 6-exo-RF-5-endo-iodo adduct 3cp and polyfluoroalkylated product 4cp retaining the trans-configuration and the exo-orientation of RF group. The fluoroalkylation-lactonization reaction occurred in the reaction of norbornene-2-endo-carboxylic acids 1d and 1e with polyfluoroalkyl iodides to afford the corresponding fluoroalkylated γ-lactone products (7dp-7ds, and 7em-7er). The configuration of the products was further confirmed by 2D NMR and X-ray diffraction analyses for the first time. |
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