Novel Electron‐Rich Hydrophilic Phosphanes with Carboxylated Cyclohexyl Substituents

Addition of diphenylphosphane or phenylphosphane to methyl 1‐cyclohexenecarboxylate (1) under base catalysis, yields the novel tertiary or secondary phosphanes 2a, 3, or4acontaining cyclohexyl backbones with the carboxylic groups in the 2‐position. The carboxylated derivative of the borane adduct of tricyclohexylphosphane 5ais accessible by a related reaction using Cy2P(BH3)Li instead of Ph2PH or PhPH2. The complete analysis of the 1H NMR spectrum of 2ausing 2D NMR spectroscopy (H,H‐, C,H‐COSY NMR spectra, 13C‐INADEQUATE) reveals the bis(equatorial) position of the Ph2P and COOMe substituents. This is supported by the results of the X‐ray structural analysis of 2b(space group P21/c). On addition of Cy2P(BH3)Li to 1and subsequent hydrolysis, 5a, the first functionalized derivative of tricyclohexylphosphane is obtained. In contrast to 2b, the COOMe substituent in 5aoccupies the axial position, the bulky phosphanyl group being equatorial as indicated by the X‐ray structural analysis (space group P21). Molybdenum(0) and palladium(II) complexes of 2aand 2bhave been synthesized. The influence of the carboxylated cyclohexyl substituent on the electronic and steric parameters of 2aand 2bis discussed.