Novel electron-rich hydrophilic phosphanes with carboxylated cyclohexyl substituents

Addition of diphenylphosphane or phenylphosphane to methyl 1-cyclohexenecar boxylate (1) under base catalysis, yields the novel tertiary or secondary p hosphanes 2a, 3, or 4a containing cyclohexyl backbones with the carboxylic groups in the 2-position. The carboxylated derivative of the borane adduct of tricyclohexylphosphane 5a is accessible by a related reaction using Cy2P (BH3)Li instead of Ph2PH or PhPH2. The complete analysis of the H-1 NMR spe ctrum of 2a using 2D NMR spectroscopy (H,H-, C,H-COSY NMR spectra, C-13-INA DEQUATE) reveals the bis(equatorial) position of the Ph2P and COOMe substit uents. This is supported by the results of the X-ray structural analysis of 2b (space group P2(1)/ c). On addition of Cy2P(BH3)Li to 1 and subsequent hydrolysis, 5a, the first functionalized derivative of tricydohexylphosphan e is obtained. In contrast to 2b, the COOMe substituent in 5a occupies the axial position, the bulky phosphanyl group being equatorial as indicated by the X-ray structural analysis (space group P2(1)). Molybdenum(0) and palla dium(II) complexes of 2a and 2b have been synthesized. The influence of the carboxylated cyclohexyl substituent on the electronic and steric parameter s of 2a and 2b is discussed.