Synthesis of new linear poly(phenylpyridyl) chains

This paper describes for the first time an efficient approach of Suzuki Miyaura cross-coupling reaction leading to new mixed linear unsymmetric phenylpyridyl chains (garlands). We have studied the synthesis of new phenylpyridyl boronic species and their reactivity with a dihalogenated bipyridine to obtain four and six unit phenylpyridines.     

Tert‐butyl hydroperoxide‐promoted guanylation of amines with benzoylthioureas: Mechanistic insights by HRMS and 1H NMR

Herein, we present a mechanistic study on tert‐butyl hydroperoxide‐promoted guanylation of thioureas by monitoring short lifetime intermediates using electrospray ionisation/time‐of‐flight high resolution mass spectrometry (ESI‐Q‐TOF HRMS). Moreover, ¹H nuclear magnetic resonance data allowed us to access kinetic parameters for the main species involved which, allied to the HRMS results, furnished valuable insights over previously reported observations. The results suggested an addition/elimination mechanism involving the aminoiminomethanesulphinic acid, RNC(SO₂H)NHR′, and the nucleophilic amine as the main pathway to yield the guanidine. Noteworthy, benzoylthiourea consumption rate presented a nonlinear kinetic behaviour, while ^tBuOOH and the nucleophilic amine consumptions were found to follow second‐order kinetics.     

Characterization of Anthocyanins and Anthocyanin-Derivatives in Red Wines during Ageing in Custom Oxygenation Oak Wood Barrels

The ageing of wines in oak barrels is a key stage in the production of high-quality red wines, with the type of oak chosen and the amount of oxygen received by the wine being the determining factors of the process. This work analyses the effect of ageing the same red wine in barrels with different oxygenation rates for one year (OTR), specifically the effect on the evolution of anthocyanins, their derivatives and the appearance of new pigments according to the oxygen dosage in barrels. Results show that wines aged in High-Wood-OTR barrels have a large quantity of monomeric anthocyanins and wine aged in Low-Wood-OTR barrels presents a major intensity of colour. Moreover, using LC-MS analysis, it was possible to detect and identify different families of anthocyanin derivatives, including the tentative identification of two new aldehyde-flavanol-methylpyranoanthocyanin pigments.     

Synthesis,Mechanism Elucidation and Biological Insights of Tellurium(IV)-Containing Heterocycles

Inspired by the synthetic and biological potential of organotellurium substances, a series of five- and six-membered ring organotelluranes containing a Te−O bond were synthesized and characterized. Theoretical calculations elucidated the mechanism for the oxidation-cyclization processes involved in the formation of the heterocycles, consistent with chlorine transfer to hydroxy telluride, followed by a cyclization step with simultaneous formation of the new Te−O bond and deprotonation of the OH group. Moreover, theoretical calculations also indicated anti-diastereoisomers to be major products for two chirality center–containing compounds. Antileishmanial assays against Leishmania amazonensis promastigotes disclosed 1,2λ⁴-oxatellurane LQ50 (IC₅₀=4.1±1.0; SI=12), 1,2λ⁴-oxatellurolane LQ04 (IC₅₀=7.0±1.3; SI=7) and 1,2λ⁴-benzoxatellurole LQ56 (IC₅₀=5.7±0.3; SI=6) as more powerful and more selective compounds than the reference, being up to four times more active. A stability study supported by ¹²⁵Te NMR analyses showed that these heterocycles do not suffer structural modifications in aqueous-organic media or at temperatures up to 65 °C.     

The first examples of the enantioselective Heck–Matsuda reaction: arylation of unactivated cyclic olefins using chiral bisoxazolines

Successful enantioselective Heck–Matsuda arylations were accomplished for the first time using chiral bisoxazolines as ligands. Enantioselective Heck arylations were performed with several cyclic nonactivated olefins to provide the Heck products in 63–96% isolated yields and in enantiomeric excesses of 54% up to 84%.     

Optimal operation of hydrothermal systems with Hydrological Scenario Generation through Bootstrap and Periodic Autoregressive Models

In electrical power systems with strong hydro generation, the use of adequate techniques to generate synthetic hydrological scenarios is extremely important for the evaluation of the ways the system behaves in order to meet the forecast energy demand. This paper proposes a new model to generate natural inflow energy scenarios in the long-term operation planning of large-sized hydrothermal systems. This model is based on the Periodic Autoregressive Model, PAR (p), where the identification of the p orders is based on the significance of the Partial Autocorrelation Function (PACF) estimated via Bootstrap, an intensive computational technique. The scenarios generated through this new technique were applied to the operation planning of the Brazilian Electrical System (BES), using the previously developed methodology of Stochastic Dynamic Programming based on Convex Hull algorithm (SDP-CHull). The results show that identification via Bootstrap is considerably more parsimonious, leading to the identification of lower orders models in most cases which retains the statistical characteristics of the original series. Additionally it presents a closer total mean operation cost when compared to the cost obtained via historic series.     

Differentiation and assignment of vinyl telluride regioisomers by 1H‐125Te gHMBC

Complete ¹H, ¹³C, and ¹²⁵Te NMR spectral data for some vinyl tellurides are described. The ¹H–¹²⁵Te gHMBC experiment was used for the complete chemical shift assignment and structure elucidation of a mixture of regioisomers. The assignment (¹²⁵Te NMR) and coupling constants (J_H,H) for all regioisomers are described for the first time. Copyright © 2012 John Wiley & Sons, Ltd.