Au(I)- and Pd(II)-NHC catalysis : novel approaches towards the synthesis of fluoroarenes/alkenes and ketone derivatives
Abstract
The preparation of organic molecules utilising synthetically simple and
economical strategies is nowadays a big field of study in chemistry. As part of this
exciting area of study, this thesis presents a group of new methodologies involving the
transformation of simple organic compounds into valuable fluorinated molecules
(fluoroarenes and fluoroalkenes) or ketone derivatives. These competitive alternatives to
traditional methods exploit the use of transition metal-NHC catalysts (NHC = Nheterocyclic
carbene), with particular interest in Au(I) complexes.
The exploration of the use of arylsulfonic acids as substrates for the preparation
of fluoroarenes was investigated for the first time. Our studies have obtained the first
experimental proof of the fluorination of such substrates through either C-S or C-H
activation. Preliminary optimisation and mechanistic studies for these reactions have
been conducted, obtaining important information that is currenly being used by our
research group to further unravel the synthetic value of arylsulfonic acids for aromatic
C(sp2)-F bond formation.
The use of terminal alkynes as substrates for the synthesis of complex organic
molecules has also been exploited. Five new reactions and six sequential methods have
been optimised. First, a new Au-catalysed protocol for the iodination of terminal
alkynes was reported. This was followed by the individual study on two addition
reactions (hydrofluorination and hydration), leading to new synthetic approaches to
iodinated fluoroalkenes and ketones, respectively. Finally, these derivatives were further
functionalised using coupling chemistry promoted by Pd(II)-NHC catalysts, accessing
trisubstituted fluoroalkenes and functionalised ketones. All these reactions were
compatible with sequential applications after minor changes, providing fast and easy
functionalisation techniques that avoid the isolation of any intermediate, and maintain
high performance and selectivity. These methods emphasise the highly convenient use
of TM-NHC catalysts as versatile tools for organic synthesis.
Type
Thesis, PhD Doctor of Philosophy
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