New Fluorination Scheme

A common way to chirally fluorinate organic compounds is to use a technique called asymmetric phase-transfer catalysis with a chiral cation catalyst. Now, a team has made the charge-inverted version of that reaction—asymmetric phase-transfer catalysis with a chiral anion catalyst—a reality. In the reaction, the chiral anion catalyst uses anion exchange to shepherd a highly polar, cationic, solid fluorinating reagent into a nonpolar solvent, where the reagent induces a cyclization reaction that adds fluorine to alkene substrates in a highly enantio- and diastereoselective way. “The method generates heterocyclic products with two stereogenic centers, including a carbon-fluorine stereocenter that would be very difficult to construct “otherwise,” note the method’s developers, F. Dean Toste and coworkers at the University of California, Berkeley (Science, DOI: 10.1126/science.1213918). The “extremely powerful” reaction could provide “convenient access to a range of novel chiral fluorinated compounds with potential applications in biology, medicinal chemistry, and materials chemistry,” writes Mikiko Sodeoka of Japan’s RIKEN in a commentary about the work.