Synthesis and Comparison of the Reactivity of Allyl Fluorides and ...

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Chapter Four
The reaction of TREAT HF was conducted in the same way, and after 1 hour, the 1 H NMR
spectrum revealed peaks attributable to PPh3, dba, triethylamine and (135). Whilst the 19 F
NMR exhibited peaks at -129.2, -165.3 and -151.9 ppm, which are all observed when a 19 F
NMR spectrum of TREAT HF is conducted on its own in CDCl3. Mass spectrometry also
confirmed the presence of (135) with a signal at m/z 805. After 24 hours the peaks in both
1 H and 19 F NMR spectra were relatively unchanged, as was the mass spectrum. Therefore,
work up followed by a final analysis of the spectroscopic data revealed that none of the
desired allylic fluoride product was present. The only new peaks were in the 1 H NMR
spectrum, and were the same as previously observed with TASF and HF.pyridine, which
were not associated with starting material or desired product and therefore difficult to
interpret.
Though several different sources of fluoride were reacted with (135), none formed the
corresponding allylic fluoride successfully. All reactions were conducted at room
temperature, and therefore the disappointing results concur with the single report of
Togni. [25] The fact that the reaction was unsuccessful could be attributed to several factors,
firstly that the reaction equilibrium favoured the formation of Pd allyl as this was
thermodynamically more favourable than the corresponding allylic fluoride and therefore,
even if the desired product was forming, due to the reaction equilibrium it was short lived
and swiftly formed the Pd allyl starting material again. It could also be that the reaction
mixture needed to be heated in order to initiate the desired reaction to occur, or that the
reaction needed colder reaction temperatures in order for the product to form. These are all
factors that could be further investigated in order to fully explore and understand the
reaction mechanism occurring.
4.3 Conclusions
The palladium (II) chloro-bridged dimers (125) and (126) were reacted with sodium acetyl-
acetonate to form the desired product, however, their isolation from the co-product (144),
which had been identified by X-ray crystallography, proved problematic. Therefore,
alternative routes were investigated which afforded the desired products in reaction with
dimethyl malonate. It was observed that reaction of sodium dimethyl malonate with bis[�-
chloro-bis(butenyl-(1,2,3-�)-oxy) methyl) benzene]dipalladium (126) occurred at the less
hindered carbon, whilst reaction with bis[�-chloro-bis(butenyl-(1,2,3-�)-benzoate]
dipalladium (125) afforded the product, where nucleophilic attack had occurred at the more
hindered carbon. Pd cationic complexes derived from allylic fluorides and allylic chlorides