Ring constructions by the use of fluorine substituent as activator and controller

Abstract

By using the properties of fluorine such as electronic effects and leaving-group ability, two types of ring-forming reactions have been achieved starting from fluoroolefins: (i) fluorinated vinyl ketones with a vinyl and/or an aryl group, which undergo fluorine-directed and/or -activated Nazarov, Friedel-Crafts, and tandem cyclizations in their combination to construct highly functionalized and fused ring systems and (ii) gem-difluoroolefins bearing a nucleophilic center on the carbon δ to the flourines undergo intramolecular substitution for the fluorine via "anti-Baldwin" 5-endo-trig closures leading to ring-fluorinated heterocycles. Throughout these reactions, fluorines function as an activator of the substrates and a controller over the reaction pathways.