6533b825fe1ef96bd1281d7c

RESEARCH PRODUCT

Modular Phosphole-Methano-Bridged-Phosphine(Borane) Ligands. Application to Rhodium-Catalyzed Reactions

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The synthesis of the phospholyl(phosphinoborane)methane air- and moisture-stable hybrid ligands 4a–f, starting from 1-phenylphospholes 1a–d, was performed via P–C bond coupling on the methano bridge. Two strategies were investigated, according to the phospholyl moiety used as a nucleophilic or an electrophilic reagent. In the first pathway, the phospholyl anions react with the easily available (chloromethyl)diphenylphosphine–borane 3 to afford ligands 4a–d in 29–67% isolated yields. In the second pathway, the phospholyl(dicyclohexylphosphinoborane)methane ligands 4e,f were synthesized in 18–23% yields, through a nucleophilic substitution on the cyanophosphole. Removal of the BH3 moiety on 4a–c assisted by DABCO leads to the hybrid phospholyl(diphenylphosphino)methanes 5a–c. Compounds 4 and 5 were fully characterized by multinuclear NMR spectroscopy (1H, 31P, 13C, 11B), mass spectrometry, and elemental analysis, and the X-ray crystal structures of 4a,c and 5a,b have been established. Ligands 5a,b were used...