My PhD dissertation - Institut Fresnel

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The preparation of the latter phosphine revealed an additional feature of the use of
triethyl phosphites. In the case of bulky substituents, the possibility to fine-tune the reaction
conditions in order to substitute selectively each ethoxy group one by one depending on the
temperature provides an additional advantage of the use of phosphites, since it is hardly
feasible with phosphorus trichloride. Comparative study could have been made to parallel the
results obtained by means of various phosphites, however, since triethyl phosphite gave the
best yields for the first phosphines prepared, the whole series was done in that manner. On the
other hand, in order to establish the efficiency and reliability of the use of phosphites as
phosphorus sources, the yield of products obtained by this method were compared to those
reported in the literature using either organomagnesiums or organolithiums reagents with
phosphorus trichloride (see Table 1). As the use of phosphites proved to give comparable or
better results than those reported in the literature, this reagent could be used to prepare newly
designed furyl and pyrrolyl phosphines.
2.2 Preparation of Trifurylphosphines
Recently, a great attention in furyl phosphines, especially (2-furyl)phosphines
has been evident in the literature because of their increasing use in homogeneous catalysis
[ 87 - 90 ]
. Bristol-Myers researchers could show in 1988 that the use of furylphosphines
instead of the usual triphenylphosphine could significantly increase the rate and yields of
the Stille cross-coupling reaction for some deactivated chlorinated substrates [87 - 89] . V.
Farina et al. [87] postulated that the use of less coordinating, poorer donating phosphine
ligands should render the Pd(II)-Allyl intermediate more electrophilic and hence more
reactive in the rate determining transmetalation step. In view to this series of results, P.
Savignac, F. Mathey et al. [65] prepared a water soluble diphenylfurylphosphine derivative
for biphasic catalysis but failed in preparing a tris(2-furyl)phosphine from phosphorus
trichloride when the furan was substituted in position-5 by a chlorine or a bromine.
The parent tris(2-furyl)phosphine was prepared by various research groups with low
[ ]
yields (30% to 40%) using either phosphorus trichloride 91 [ ]
or phosphorus tribromide 92 . A.J.
Zapata and A.C. Rondon explained the low yields obtained by occurrence of undesirable
side reactions due to the high reactivity of the 2-furyllithium involved. They could raise
the yield of tris(2-furyl)phosphine to 74% by transmetalating the reactive lithiated species
with cerium(III) chloride and treating it with phosphorus trichloride. The preparation of
valuable trifurylphosphines ligands by the "phosphite route" was performed with
[ ] 86 ,