Gold(I)-catalyzed Claisen rearrangement of allenyl vinyl ethers; synthesis of substituted 1,3-dienes

Synthesis of substituted 1,3-dienes was achieved via gold(I)-catalyzed Claisen rearrangement of allenyl vinyl ethers. The N-heterocyclic carbene gold chloride catalyst (IPrAuCl) was superior in terms of activity and selectivity and afforded the 3,3-product in excellent yields. A proposed cation-π inter-action played a significant role in affecting the reaction rate.     

Regioselective cyclizations utilizing a gold-catalyzed [3,3] propargyl ester rearrangement

Switch-Au-roo: A new strategy for the regioselective synthesis of unsaturated carbocycles by chemoselective activation of a Rauhut-Currier zwitterion surrogate, formed from the Au-catalyzed [3,3]?sigmatropic rearrangement of propargylic esters, has been achieved. By reversing the regiochemistry of the propargyl ester the synthesis of either the endo- or exocyclic enones is feasible.     

Characterization of zinc hydroxynitrates by diffuse reflectance infrared spectroscopy--structural modifications during thermal treatment

Four zinc hydroxynitrates are known, but only the Infrared spectrum of Zn5(OH)8(NO3)2.2H2O is reported in the literature. Here, we report the IR spectra of the other three zinc hydroxynitrates, namely Zn(OH)(NO3).H2O, Zn3(OH)4(NO3)2 and Zn5(OH)8(NO3)2. The positions of the bands of the nitrate groups between 1000 and 1600 cm(-1) are discussed in relation to the structure of these compounds. The modifications of these IR spectra with temperature are consistent with previous studies on the thermal decomposition of these compounds.     

Nonturbulent stabilization of ion fluxes by the fan instability

Resonant interactions between energetic ion fluxes and wave packets they excite through fan instability are studied using self-consistent 3D simulations to explain the nonlinear wave–particle mechanisms at work and to estimate the energy lost by the flux and its sharing between wave emission and particle heating. The saturation of waves and the relaxation of particles are studied over long time periods. The ions are not only diffusing in the waves but are also trapped simultaneously by several potential wells of large amplitude overlapping waves. Estimates of the ion heating energy and rate are given and compared with space observations.     

Accuracy-Risk Trade-Off Due to Social Learning in Crowd-Sourced Financial Predictions

A critical question relevant to the increasing importance of crowd-sourced-based finance is how to optimize collective information processing and decision-making. Here, we investigate an often under-studied aspect of the performance of online traders: beyond focusing on just accuracy, what gives rise to the trade-off between risk and accuracy at the collective level? Answers to this question will lead to designing and deploying more effective crowd-sourced financial platforms and to minimizing issues stemming from risk such as implied volatility. To investigate this trade-off, we conducted a large online Wisdom of the Crowd study where 2037 participants predicted the prices of real financial assets (S&P 500, WTI Oil and Gold prices). Using the data collected, we modeled the belief update process of participants using models inspired by Bayesian models of cognition. We show that subsets of predictions chosen based on their belief update strategies lie on a Pareto frontier between accuracy and risk, mediated by social learning. We also observe that social learning led to superior accuracy during one of our rounds that occurred during the high market uncertainty of the Brexit vote.     

Independence numbers of product graphs

This paper deals with the problem of determining the independence number for the strong graph-product, especially for odd cycles. Using the concepts of a point-symmetric graph and the clique-number and introducing the notion of an independence graph, we extend and generalize some results of Hales [3] for cycle-products of power three.     

DasL/K- und dasM/L-Einfangverhältnis von65Zink

We have investigated theL/K- and theL/M-capture ratio of⁶⁵Zn. For the transitions to the first excited state of⁶⁵Cu we obtained (N _L/N _K) _A =0.120±3% and (N _M/N _L) _A =0.153±13% and for both transitions to the groundstate and the first excited state simultaneously we found (N _L/N _K) _G =0.118±3%. The values for (N _L/N _K) agree well with the results of Santos Ocampo and Conway but are higher than the results of Totzek and Hoffmann. All values are discussed in view of the different theoretical values obtainable.     

Generation of thioaldehydes via fluoride induced elimination of α-silyldisulfides

A mild, efficient and general method for the generation of reactive thioaldehydes from α-silyldisulfides is described.