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Stereochemical Investigation of the Products of the Photoinduced Perfluoroalkylation–Dimerization of Anthracene

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posted on 18.09.2015, 00:00 by Emiko Nogami, Takashi Yamazaki, Toshio Kubota, Tomoko Yajima
The photoinduced perfluoroalkylation of anthracene has been shown to provide 9,9′,10,10′-tetrahydro-10,10′-diperfluoroalkyl-9,9′-bianthracenes in over 70% yields, each perfluoroalkyl iodide producing three diastereomers. The structures of all three diastereomers (cis,cis, cis,trans, and trans,trans isomers) have been elucidated by both NMR and X-ray crystallographic analyses. Most notably, an X-ray crystallographic analysis has revealed that the trans,trans diastereomer having the two trifluoromethyl groups in 10,10′-positions adopts a 74° twisted relationship of the two dihydroanthracene rings. Furthermore, each of the two trans,trans isomers 2a,b has been shown to exist as a mixture of new types of atropisomers and the energy barrier for the interconversion of the two atropisomers has been estimated to be 12 kcal/mol by variable-temperature NMR analysis.