Optimization of a Pd-catalyzed intramolecular α-arylation synthesis of tricyclo-[7.3.1.0]-trideca-2,4,6-trien-13-ones

We have optimized the Pd-catalyzed intramolecular α-arylation of 2-(2-halo-benzyl)-cyclohexanones and found that the use of 2-(dicyclohexylphosphino)-2′,4′,6′-tri-i-propyl-1,1′-biphenyl (X-Phos) as an added ligand led to a reproducible, efficient, and scalable synthesis of tricycle-[7.3.1.0^2,7]-trideca-2,4,6-trien-13-ones.     

The Effect of Time-Dependent Coupling on Non-Equilibrium Steady States

Consider (for simplicity) two one-dimensional semi–infinite leads coupled to a quantum well via time dependent point interactions. In the remote past the system is decoupled, and each of its components is at thermal equilibrium. In the remote future the system is fully coupled. We define and compute the non equilibrium steady state (NESS) generated by this evolution. We show that when restricted to the subspace of absolute continuity of the fully coupled system, the state does not depend at all on the switching. Moreover, we show that the stationary charge current has the same invariant property, and derive the Landau–Lifschitz and Landauer–Büttiker formulas. Submitted: July 11, 2008., Accepted: October 23, 2008.     

Synthesis of dihydroxy telechelic oligomers of β-butyrolactone catalyzed by titanium(IV)-alkoxides and their use as macrodiols in polyurethane chemistry

We report on a solvent-free approach for the synthesis of low molecular weight, α,ω-dihydroxy telechelic poly(β-butyrolactone). In the presence of Ti(IV) alkoxides, mixtures of β-butyrolactone and diols, like di- or triethylene glycol, were reacted in ratios between 4:1 and 10:1. The oligomerization proceeds at elevated temperatures (80–100°C). Different alkoxide substituents (R = Me, iPr, tBu) of the Ti(IV)(OR)₄ catalyst were investigated. The resulting oligomers were characterized by nuclear magnetic resonance (NMR), infra-red (IR), gel-permeation chromatography (GPC), titration, and matrix-assisted laser desorption-time-of-flight mass spectrometry (MALDI-ToF-MS) analysis. Aside from low molecular weight products, special effort was devoted to achieve high O-acyl cleavage selectivity and to circumvent the formation of unsaturated end-groups in order to form exclusively dihydroxy-telechelic oligomers. Optimized results in terms of selectivity and reaction rates were achieved at 100°C using catalyst loadings of 0.2 mol% with respect to the monomer. The molecular weights determined by GPC were in good accordance with the ratio of monomer to diol used, confirming successful oligomer formation. Polyurethanes prepared from crude macrodiols without any additional catalyst feature molecular weights up to 50,000 g/mol. The reported work serves as concept to utilize β-lactones for tailored polyol synthesis; the resulting products are suitable for polyurethane chemistry.