Synthesis and Study of the Thermal Epimerization of r -2-Ethoxy- cis -4- cis -5-Dimethyl-1,3,2-λ 3 -Dioxaphospholane Using 31 P NMR
摘要:
The exclusive synthesis of r-2-ethoxy-cis-4-cis-5-dimethyl-1,3,2-,lambda(3)-dioxaphospholane (cis-1) is reported. The kinetic measurements of the epimerization of cis-1 to trans-1 were performed by P-31 NMR from 50 to 80degreesC in toluene. The energy of activation (E-a) of the epimerization process was calculated from Arrhenius plot. The thermodynamic parameters of the transition state led us to conclude that the activation barrier of the in version at phosphorus is driven by the enthalpy and by a large and negative entropy of activation.
imide -amide rearrangement of cyclic phosphorimidates. As a result of this work new types of oligomeric organophosphorus compounds, formed by a novel 1,4-addition type ring opening polymerisation, were identified. These compounds are the stable intermediates of the imide-amide rearrangement, which upon heating yield the previously reported rearranged product. A detailed study of the mechanism of the Lewis