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Title: Primary phosphine analogues of BINAP, QUINAP, and [2.2] PHANEPHOS : their stability and reactivity
Author: Abelairas Edesa, Manuel F.
ISNI:       0000 0004 5919 3409
Awarding Body: Newcastle University
Current Institution: University of Newcastle upon Tyne
Date of Award: 2015
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Primary phosphines have a notorious reputation for being highly air–sensitive and sometimes pyrophoric. They can undergo thermal decomposition, possess a pungent odour and are often toxic. They are however highly useful for preparing phosphorus–containing motifs, allowing access to compounds which are difficult to synthesise through different methodologies. We recently reported the successful isolation of air–stable, chiral monodentate primary phosphines, which were used as precursors in the synthesis of ligands for use in asymmetric catalysis. The stability of these primary phosphines is thought to be a result of extended π–conjugation in their binaphthyl backbone. A number of important catalytic processes require bidentate phosphine ligands. We therefore sought to build upon our previous work, and have prepared a range of enantiopure bidentate primary phosphines, to be used as precursors in the synthesis of novel ligand libraries. In Chapter 2, we introduce methodologies to access a diphosphonate ester–containing 1,1'-binaphthyl framework in both its racemic and chiral forms. For this, copper–catalysed Ullmann C–C homocouplings, Suzuki–Miyaura C–C cross–couplings, and organotin–mediated aryl radical trapping methods were evaluated. Subsequently, the chiral diprimary phosphine, BINAPH2, was synthesised and air–stability studies were performed. Functionalisation of the two –PH2 groups allowed us to access a range of bidentate phosphine ligands with different stereoelectronic properties. Rhodium(I) complexes of the ligands were tested in asymmetric catalytic hydrogenation and hydroformylation reactions of benchmark prochiral substrates. Following on from our work with bidentate P,P–ligands, Chapter 3 describes our efforts to synthesise the novel, heterofunctionalised QUINAP–based primary phosphine QUINAPH2. P,N–chelating ligands were subsequently made and the solid and solution state stabilities of the primary phosphine were studied. Finally, in Chapter 4 we report the synthesis of mono– and bidentate [2.2]paracyclophane– based phosphine ligands, derived from their primary phosphine precursors. Monodentate [2.2]paracyclophanyl primary phosphines possessing varying degrees of conjugation in the backbone were synthesised and their air–stabilities compared to those predicted by our DFT model. The pseudo-ortho substituted bidentate primary phosphine, [2.2]PHANEPH2, was also synthesised, and used to access a series of ligands. These were tested in rhodium(I)–catalysed hydrogenation reactions of prochiral alkenes.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available