Page 9 - PERIODIC Magazine Issue 6

The chemistry of the aluminyl species also depends on the
identity of the counterion, much in the manner of organic
nucleophiles, and hence a range of compounds with varied
reactivities are being targeted. This current research is just
the tip of the iceberg of what could be achieved through
these new findings.

Gouverneur Group
Using hydrogen bonding and phase transfer catalysis
to deliver fluorides enantioselectively

and hydrogen bonding, which involves in this case
plucking the fluoride anion from its salt, leaving it free to
react with a target molecule in solution.

Both experimental and computational studies were
performed to design the optimal catalyst for the
The presence of fluorine in pharmaceutical and transformation, with the research team ultimately
agrochemical compounds can have significant beneficial deciding on a tridentate chiral bis-urea catalyst. Due to
effects on their chemical and biological properties – the chirality of the optimal catalyst, the reaction is biased
including stability, lipophilicity, and bioavailablity. It is towards producing one of the two mirror-image products
estimated that approximately 25% of pharmaceuticals and (enantiomers). This is called enantioselective catalysis
agrochemicals currently on the market contain fluorine. as one enantiomer is preferentially synthesized over the
other.
Natural fluoro-organic compounds are very rare, so
progress in these areas relies on fluorination protocols Professor Gouverneur and co-workers have successfully
in synthetic organic chemistry. Novel methodologies to carried out a highly efficient enantioselective ring opening
achieve this important goal are therefore constantly in of various episulfonium ions. In this reaction, the catalyst
need. Inorganic alkali metal fluoride plays three major roles. It brings the fluoride from the
salts (such as KF or CsF) are easy-
to-handle and safe thus potentially
making them excellent fluoride
sources. However, because of their
insolubility in organic solvents, their
use in organic synthesis, especially
asymmetric catalysis, has been
limited.

A research team led by Professor
Véronique Gouverneur has found
a way to release fluoride ions from
these strong ionic bonds, so that
these inexpensive fluoride salts can
be used as nucleophilic reagents.
The key to the method’s success is
the combination of two well-rooted
concepts. These are phase-transfer
catalysis, in which a reagent is
relocated from one phase to another,

9
Periodic
The Magazine of the Department of Chemistry