Water-soluble phosphines: Part XII. Pd catalyzed P-C coupling reactions: A novel synthetic route to cationic phosphines with para- and meta-guanidiniumphenyl moieties

Article abstract of DOI:10.1016/S0022-328X(00)00151-0

Mono- and bifunctional guanidinium phosphines (3c, 4a, 4b, 5a-5d, 5f) containing para-and meta-guanidiniumphenyl moieties -C₆H₄-NH-C(NH₂)(NR₂)⁺ (R=H, Me) are accessible in high yields by Pd catalyzed P-C coupling reactions between iodophenyl guanidines I-C₆H₄-NH-C(NH)NR₂ (meta-, para-isomers; R=H, Me) and phenyl- or diphenylphosphine. The X-ray structure of 3c·MeOH (space group P2₁2₁2₁) has been determined, showing a planar guanidinium group in a NH-O and NH-Cl hydrogen bridged arrangement. Pd(II) and Mo(0) complexes of 5c have been synthesized. The influence of the cationic guanidinium group on the electronic and steric parameters of 5c is discussed. A comparative study of 5c, phosphonated and sulfonated phosphine ligands in the biphasic Pd catalyzed Suzuki-type coupling between m-bromophenyldiphenyl phosphine oxide and para-tolylboronic acid shows 5c to be less active than Ph₂P-C₆H₄-4-PO₃Na₂.