Electrochemical Dehydrogenative Cyclization Of 1,3-dicarbonyl Compounds

Last several decades have witnessed a considerable progress of carbon-centered radicals,among which,1,3-dicarbonyl compound based radicals are widely used in organic synthesis.These electrophilic C-centered radicals can be obtained through single electron oxidation of 1,3-dicarbonyl compounds using stoichiometric metal or non-metal oxidants,which produce waste and bring potential danger to industrial scale synthesis.Electrochemical generation of this type of C-centered radicals doesn't require additional oxidants,and therefore,avoids the formation of reagent-associated waste.More importantly,organic electrosynthesis is highly controllable and the chemoselectivity or progress of the reaction can be precisely controlled by adjusting the potential or current.This dissertation focuses on the electrochemical generation of C-centered radicals from 1,3-dicarbonyl compounds and their applications in dehydrogenative cyclization reactions.First,we have employed cost-effective Cp2Fe for the synthesis of C3-fluorinated oxindoles through cross-dehydragenative coupling of C(sp3)-H and C(sp2)-H bonds from malonate amides(Scheme 1).Under the mild electrochemical conditions,3-fluorooxindoles are formed in high efficiency with broad substrate scope.The synthetic usefulness of the electrochemical method is further highlighted by its easy scalability and the diverse transformations of the electrolysis product.Scheme 1.Electrosynthesis of 3-fluorooxindolesThe intramolecular C(sp3)-H/C(sp2)-H cross-coupling of 1,3-dicarbonyl compounds through Cp2Fe-catalyzed electrochemical oxidation has also been employed for the synthesis of 3,4-dihydro-1H-quinolin-2-ones(Scheme 2).The electrochemical method is not only with high efficiency and good yield but insensitive to the electronic properties of N-phenyl rings.Scheme 2.Electrosynthesis of 3,4-dihydro-1H-quinolin-2-ones...