Abstract
M.Sc.
The objective of the project described in this dissertation was the preparation of a
range of bulky electron-rich phosphine ligands making use of the directed ortho
metallation (DoM) methodology developed in our labs. These ligands would then
be employed in the Suzuki and Heck reactions of aryl bromides and aryl
chlorides.
A range of phosphinic amides were synthesised with various structural
differences. These phosphinic amides all showed high activity in the DoM
reaction when using TMSCl and MeI as electrophiles, by successfully
incorporating TMS and Me groups in the ortho-positions of these phosphinic
amide systems. A phosphonic amide was also synthesised and used in the DoM
reaction, and also successfully incorporated TMS and Me in the ortho-position of
this system. The success of these reactions was encouraging and provided a
route to incorporate a phosphine on the ortho-position of these phosphinic amide
and phosphonic amide systems by using a range of phosphine electrophiles
Ar2PCl.
The route was versatile and various electrophiles were used to prepare
phosphine ligands with varying electronic and steric properties. These
electrophiles were prepared from PCl3 and the corresponding Grignard reagent.
Vaska-type complexes and phosphine selenium coupling constants were used to
determine the electronic and stereo-electronic characteristics of the prepared
ligands.
The phosphine ligands prepared in this project making use of our DoM
methodology were tested in the Suzuki cross-coupling reactions and Heck
arylation reactions of aryl bromides and aryl chlorides and showed good
reactivity with most of the substrates used. An advantage of the ligands prepared
is that these ligands are oxidatively and hydrolytically stable