Platinum-catalyzed enantioselective tandem alkylation/arylation of primary phosphines. Asymmetric synthesis of P-stereogenic 1-phosphaacenaphthenes

Enantioselective tandem alkylation/arylation of primary phosphines with 1-bromo-8-chloromethylnaphthalene catalyzed by Pt(DuPhos) complexes gave P-stereogenic 1-phosphaacenaphthenes (AcePhos) in up to 74% ee. Diastereoselective formation of four P-C bonds in one pot with bis(primary) phosphines gave C2-symmetric diphosphines, including the o-phenylene derivative DuAcePhos, for which the rac isomer was formed with high enantioselectivity. These reactions, which appear to proceed via an unusual metal-mediated nucleophilic aromatic substitution pathway, yield a new class of heterocycles with potential applications in asymmetric catalysis.     

Experimental and Computational Study of the Thermal Decomposition of 3‐Methyl‐3‐buten‐1‐ol in m‐Xylene Solution

An experimental study of the thermal decomposition of a β‐hydroxy alkene, 3‐methyl‐3‐buten‐1‐ol, in m‐xylene solution, has been carried out at five different temperatures in the range of 513.15–563.15 K. The temperature dependence of the rate constants for the decomposition of this compound in the corresponding Arrhenius equation is given by ln k (s^?1) = (25.65 ± 1.52) ? (17,944 ± 814) (kJ·mol^?1)·T^?1. A computational study has been carried out at the M05–2X/6–31+G(d,p) level of theory to calculate the rate constants and the activation parameters by the classical transition state theory. There is a good agreement between the experimental and calculated rate constants and activation Gibbs energies. The bonding characteristics of reactant, transition state, and products have been investigated by the natural bond orbital analysis, which provides the natural atomic charges and the Wiberg bond indices. Based on the results obtained, the mechanism proposed is a one‐step process proceeding through a six‐membered cyclic transition state, being a concerted and slightly asynchronous process. The results have been compared with those obtained previously by us (Struct Chem 2013, 24, 1811–1816) for the thermal decomposition of 3‐buten‐1‐ol, in m‐xylene solution. We can conclude that in the compound studied in this work, 3‐methyl‐3‐buten‐1‐ol, the effect of substitution at position 3 by a weakly activating CH₃ group is the stabilization of the transition state formed in the reaction and therefore a small increase in the rate of thermal decomposition.     

Structural and Kinetic Aspects of Blood Plasma Protein Adsorption on the Surface of Hydrophobic Polymers

Abstract

Due to the wide use of polymers in medicine, researchers are required to solve a very important problem–to understand the interaction between materials of nonphysiological origin and the surrounding biological liquids, and tissues, particularly blood.     

Derivatives of 1,1′-bis(diphenylphosphino)ferrocene (dppf): Electrochemistry, complexation and the X-ray structures of 1,1′-bis(diphenylphosphino)osmocene (dppo) and [PdCl2(dppo)]

The oxidative electrochemistry of 1,1′-bis(diphenylphosphino)osmocene (dppo) and 1,1′-bis(diphenylarsino)ferrocene (dpaf) was studied in dichloromethane with tetrabutylammonium hexafluorophosphate as the supporting electrolyte. The [MCl₂(P^∩P)] (M = Pd or Pt; P^∩P = dppo or 1,1′-bis(diphenylphosphinoindenyl)iron) complexes were prepared, studied electrochemically and the X-ray structures of dppo and [PdCl₂(dppo)] were determined.     

The coordination chemistry of the hydrotris(3-diphenylmethylpyrazol-1-yl)borate (Tp(CHPh2)) ligand

The new ligand, hydrotris[3-(diphenylmethyl)pyrazol-1-yl]borate, Tp(CHPh2), has been synthesized and its coordination chemistry was compared with that of the analogous Tp(iPr). The new ligand was converted to a variety of complexes, such as M[Tp(CHPh2)]X (M = Co, Ni, Zn; X = Cl, NCO, NCS), Pd[Tp(CHPh2)][eta3-methallyl], Co[Tp(CHPh2)](acac), and Co[Tp(CHPh2)](scorpionate ligand). Compounds Tl[Tp(CHPh2)], 1, Co[Tp(CHPh2)]Cl, 2, Co[Tp(CHPh2)](NCS)(DMF), 3, Ni[Tp(CHPh2)](NCS)(DMF)2, 4, Co[Tp(CHPh2)](acac), 5, Co[Tp(CHPh2)][Ph2Bp], 6, Co[Tp(CHPh2)][Bp(Ph)], 7, Co[Tp(CHPh2)][Tp], 8, and (Ni[Tp(CHPh2)])2[C2O4](H2O)2, 9, were structurally characterized.     

A stable alkyl hydride of a first row transition metal

Hydrogenolysis of a Cr(III) dialkyl precursor produced a binuclear chromium complex with a bridging hydride and a bridging alkyl; this structurally characterized organometallic compound is thermally very stable and does not undergo the expected reductive elimination of alkane.