Study On Palladium-catalyzed Coupling Of Allenylphosphine Oxides With N-tosylhydrazones

Transition-metal-catalyzed cross-coupling reactions with N-tosylhydrazones have been developed rapidly during the past decades.The diazo substrates can be generated in situ from N-tosylhydrazones in the presence of base,which are very easy to form metal carbine with transition metals.Metal carbene is a common intermediate for the construction of new C-C,C-N and other chemical bonds.On the other hand,π-allyl-palladium species are easily formed form allenylphosphine oxides under basic conditions,which could react with nucleophiles smoothly to construct novel chemical bonds.In this thesis,we focus on a palladium-catalyzed coupling of allenylphosphine oxides with N-tosylhydrazones to construct novel phosphinyl compounds,which might be precursors for synthesizing potential bioactive molecules.The palladium catalyzed coupling of different kinds of N-tosylhydrazones and allenylphosphine oxides to construct novel phosphinyl compounds are discussed in detail.Two aspects are mainly included:1.A palladium-catalyzed coupling of allenylphosphine oxides with N-tosylhydrazones was developed leading to novel phosphinyl[3]dendralenes,and a plausible mechanism was proposed.In the presence of palladium catalyst,7r-allyl-palladium species were formed from allenylphosphine oxides.Subsequently,the decomposition of N-tosylhydrazones toward carbene species is in-situ captured by the intermediate.The final coupling product is obtained through migratory insertion and β-hydride elimination.The compounds were isolated and characterized by 1H-NMR,13C-NMR,31P-NMR,HR-MS,IR,m.p.,among which 37 compounds were reported for the first time.Single crystal structures revealed the dimensional orientation of multiple double bonds are acyclic branched polyolefins in phosphinyl[3]dendralenes.The coupling product was further applied to an intramolecular cyclization and selective oxidation reaction.2.A palladium-catalyzed two-component coupling of allenylphosphine oxides with conjugated N-tosylhydrazones toward pyrazolemethylene-substituted phosphinyl allenes was conducted.The results show that the pyrazole compound is formed from the in situ generated N-tosylhydrazones in the presence of base.As a good nucleophile,it can react with the π-allyl-palladium intermediates to form pyrazolemethylene-substituted phosphinyl allenes.The compounds were isolated and characterized by 1H-NMR,13C-NMR,31P-NMR,HR-MS,IR,m.p.,among which 26 compounds were reported for the first time.When treated with palladium acetate and NBS,pyrazolemethylene-substituted phosphinyl allenes can be easily transformed into multi-functionalized phosphinates via C-P(O)cleavage and rearrangement of diphenylphosphine oxide to the endmost carbon of allenes.