DoM chemistry in the preparation of phosphine ligands for Pd-catalysed reactions

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 stabl