330807-80-2Relevant academic research and scientific papers
2-Pyridyl-2-phospholenes: New P,N ligands for the palladium-catalyzed isoprene telomerization
Leca, Francois,Reau, Regis
, p. 425 - 429 (2007/10/03)
2-(2-Pyridyl)-2-phospholenes are efficient ligands for the palladium-catalyzed telomerization of isoprene with diethylamine. Good selectivities for the tail-to-head or tail-to-tail aminoterpenes are achieved on optimization of the ligand substituents and
A new family of P,N chelates: Stereoselective synthesis of 2-pyridyl-2-phospholenes in the coordination sphere of palladium(II) complexes
Leca, Francois,Lescop, Christophe,Toupet, Loic,Reau, Regis
, p. 6191 - 6201 (2008/10/09)
The synthesis of Pd(II) complexes 2a,c′, bearing 2-(2-pyridyl) phosphole ligands which act as P,N chelates, is described. Ligands featuring a pendant pyridyl group spontaneously evolve to the corresponding 2-pyridyl-2-phospholene derivatives in the coordination sphere of Pd(II). This isomerization is a stereoselective process, the stereochemistry of the resulting derivatives 3a,a′ being established by X-ray diffraction studies. The isomerization of ligands lacking pendant pyridyl groups was accomplished by adding pyridine to the reaction media. High yields were achieved under very mild conditions for ligands possessing different substitution patterns. Multinuclear NMR spectroscopic data and X-ray diffraction studies showed that the stereoselectivity of the process is preserved under these new reaction conditions. The transformation did not occur with free 2-(2-pyridyl)phospholes, even at high temperatures in the presence of pyridine. DFT calculations confirmed that coordination to a Pd(II) center is required to make this isomerization thermodynamically feasible. The isomerization has also been demonstrated with Pt(II) precursors but failed with CuCl, CuCl2, and ZnCl2. The free 2-pyridyl-2-phospholenes 4a,c′ were obtained by reacting the complexes 3a,c′ with dppe. No inversion of the P atom of the phospholene ring was observed up to 90°C, indicating that this novel family of P,N chelates is a promising class of ligand for homogeneous catalysis.
