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Cerium(IV) based oxidative free radical cyclization of active methylene compounds with some cyclic alkenes: A useful annulation method for terpene functionalization
- Světlík, Jan, Tureček, František, Hartwich, Katarzyna, Kozieł, Krzysztof, Pakulski, Paweł, Pałasz, Aleksandra, Kalinowska-Tłuścik, Justyna, Cież, Dariusz
- Tetrahedron 2019 v.75 no.18 pp. 2652-2663
- alkenes, ammonium, camphene, carvone, cerium, chemical bonding, cyclization reactions, enantiomers, free radicals, stereoselectivity
- Ceric ammonium nitrate-mediated oxidative cyclizations of CH-acids with terpenes and terpene like substrates were investigated. Dimedone, acetylacetone, and methyl nitroacetate were condensed with pinene, norbornene, nopol, camphene, and carvone and the reaction stereoselectivity was examined. Condensation with endocyclic double bonds in pinene and nopol displayed stereoselectivity, resulting in the formation of pure enantiomers. Condensation with exocyclic double bonds in camphene and carvone produced enantiomer mixtures. The mechanism of the intramolecular annulation in a nopol derivative is discussed with the help of DFT and ab initio calculations.