Ring constructions by the use of fluorine substituent as activator
and controller*
Junji Ichikawa
Department of Chemistry, Graduate School of Science,
The University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
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
d 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.
*Lecture presented at the 13th International
Conference on Organic Synthesis (ICOS-13), Warsaw, Poland, 1-5 July
2000.
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