Intramolecular meta photocycloaddition of 6-arylhex-2-enes Part 2

The course of the intramolecular meta photocycloaddition of ring-substituted (E)- and (Z)- 6-phenylhex-2-enes depends on the position and nature of the substituent. In this paper, the effects of methyl and cyano groups and the fluorine atom are described. The results are in agreement with a reaction mechanism in which the excited phenyl ring becomes polarized when it is approached by the alkene. The dipolar character becomes particularly apparent in the case of fluorine which, depending on its position, can stabilize either the negative charge through its inductive effect or the positive charge through its mesomeric effect. The configuration of the terminal methyl group sterically influences the photoreaction. The Z alkenes readily undergo the 1′,3′-addition, but fail to add in the 2′,6′-mode, even if substituents which strongly promote this mode are present. The E alkenes seem to suffer from steric hindrance in the 2′,6′- and the 1′,3′-mode, but the electronic effects of activating substituents provide compensation and substituents may have a pronounced influence on the ratio of the two modes.     

Robust optimization of uncertain multistage inventory systems with inexact data in decision rules

In production-inventory problems customer demand is often subject to uncertainty. Therefore, it is challenging to design production plans that satisfy both demand and a set of constraints on e.g. production capacity and required inventory levels. Adjustable robust optimization (ARO) is a technique to solve these dynamic (multistage) production-inventory problems. In ARO, the decision in each stage is a function of the data on the realizations of the uncertain demand gathered from the previous periods. These data, however, are often inaccurate; there is much evidence in the information management literature that data quality in inventory systems is often poor. Reliance on data “as is” may then lead to poor performance of “data-driven” methods such as ARO. In this paper, we remedy this weakness of ARO by introducing a model that treats past data itself as an uncertain model parameter. We show that computational tractability of the robust counterparts associated with this extension of ARO is still maintained. The benefits of the new model are demonstrated by a numerical test case of a well-studied production-inventory problem. Our approach is also applicable to other ARO models outside the realm of production-inventory planning.     

Derivatives of cis-NPCl2(NSOCl)2 and (NPCl2)2NSOCl. Part XIV—synthesis and nuclear magnetic resonance study of dimethylamino derivatives of NPCl2(NSOPh)2 and (NPCl2)2NSOPh

The compounds trans-NPCl_2?n(NMe₂)_n(NSOPh)₂(n=0-2iNPCl_2?n NMe₂)_n (NSOPh)₂ (n=0-2) and N₂P₂Cl_4?nl_4?n(NMe₂)_nNSOP₂P₂Cl_4?n(NMe₂)_nNSOPh(n=0-4), were prepared from their chloro-precursors. The substitution follows a completely non-geminal pathway, and all possible isomers are formed. The observed relative abundance of these isomers shows that the phenyl group exhibits a strong directing effect on the incoming amine. The ¹H, ³¹P and ¹³C NMR spectra of the most abundant isomers are reported. ²J(CP) couplings within the PNMe₂ grouping are affected by the number of substituents at the phosphorus atom. Almost linear relationships exist between the degree of substitution and the chemical shift of C-1 and C-4 of the phenyl groups. The effect of substitution on the ¹³C chemical shifts of these groups is ascribed to inductive effects.     

Selective optical recognition and quantification of parts per million levels of Cr(6+) in aqueous and organic media by immobilized polypyridyl complexes on glass

Selective optical sensing of parts per million levels of Cr(6+) in water under acidic conditions with robust, osmium-chromophore-based monolayers is demonstrated. The sensor system can be reset by washing with water at neutral pH and can be readily monitored by UV/vis spectroscopy.     

Remarkable steric effects and influence of monodentate axial ligands l on the spin-crossover properties of trans-[FeII(N4 ligand)L] complexes

Iron(II) complexes obtained from tetradentate, rigid, linear N4 ligands have been investigated to appraise the influence of steric effects and the impact of trans-coordinated anions on the spin-transition behavior. As expected, the well-designed ligands embrace the metal center, resulting in octahedral iron(II) complexes where the basal plane is fully occupied by the pyridine/pyrazole N4 ligand, while anions or solvent molecules are exclusively axially coordinated. Precursor complexes, namely, [Fe(bpzbpy)(MeOH)2](BF4)2 (where bpzbpy symbolizes the ligand 6,6'-bis(N-pyrazolylmethyl)-2,2'-bipyridine) and [Fe(mbpzbpy)(MeOH)2](BF4)2 (where mbpzbpy symbolizes the ligand 6,6'-bis(3,5-dimethyl-N-pyrazolmethyl)-2,2'-bipyridine), have been used for the in situ preparation of a series of structural analogues via the exchange of the weakly coordinated trans methanol molecules by various anions, such as thiocyanate, selenocyanate, or dicyanamide. The magnetic properties of all seven iron(II) compounds thus obtained have been investigated. Two iron(II) complexes, i.e., [Fe(bpzbpy)(NCS)2] and [Fe(bpzbpy)(NCSe)2], exhibit gradual spin-crossover (SCO) properties typical of isolated mononuclear species with weak cooperative interaction. These two SCO materials have been studied by M?ssbauer spectroscopy, and the light-induced excited spin state trapping effect has been investigated, revealing the possibility to induce the spin-transition both by temperature variation and by light irradiation. A correlation between steric/anion effect and SCO behavior is suggested.     

Determination of unbound prednisolone, prednisone and cortisol in human serum and saliva by on-line solid-phase extraction liquid chromatography tandem mass spectrometry and potential implications for drug monitoring of prednisolone and prednisone in saliva

Prednisolone (PLN) and prednisone (PN) are widely used glucocorticoids. Drug monitoring of PLN and PN is not routinely done owing to the need for multiple blood sampling and challenging measurement of unbound PLN and PN in blood. Here we present a robust method for quantification of cortisol, PLN and PN in serum, ultrafiltrate and saliva by on‐line solid‐phase extraction LC‐MS/MS. The method is linear for the three analytes over the range of 6–1400 nmol/L for serum and 2–450 nmol/L for ultrafiltrate and saliva. Within‐run precision of all three analytes was <10% and total precision was <15%. This method was applied to create time–concentration profiles of cortisol, PLN and PN after an oral dose of prednisolone in a healthy volunteer. Salivary levels of PLN correlated well with ultrafiltrate levels (p < 0.01), while this correlation was only marginal for PN (p = 0.052). The PN/PLN ratio was significantly higher in saliva than in ultrafiltrate and serum (p < 0.01). Addition sums of both metabolites in saliva showed excellent correlation with those of ultrafiltrate (p < 0.01). These findings have not been presented before and may have important implications for future studies concerning drug monitoring of PLN and PN in saliva. Copyright © 2011 John Wiley & Sons, Ltd.     

Dual-cure processes: towards deformable crosslinked coatings

Two dual-cure processes consisting of a UV-initiated radical polymerization followed by either a UV-induced cationic polymerisation, or a thermal addition reaction, were investigated. The feasibility of the processes was studied using an acrylate-oxetane monomer for the UV/UV combination, and an acrylated oligoester for the UV/Heat combination. It was shown by FTIR and Tg measurements, that both steps of each process could be performed efficiently and separately. This allowed the production of a deformable partially cured coating, whose cure can then be completed, leading to the required final properties. Furthermore, it was demonstrated that the increase of the functionality of the reactive diluent led to a decrease of the thermal crosslinking extent. This is probably due to the reduced mobility of the reactive species that is caused by an enhanced UV crosslinking taking place during the first step.     

Detection of fungal carbohydrate antigens by high-performance immunoaffinity chromatography using a protein A column with covalently linked immunoglobulin G.

Fungal carbohydrate antigens were analysed by high-performance immunoaffinity chromatography (HPIAC) with immunoglobulin G (IgG) antibodies raised against extracellular polysaccharides of Mucor racemosus. The protein A-IgG complex was covalently bound with dimethyl pimelimidate, which enabled the use of strong acidic buffers to release the tightly bound antigens from the column. Prior to pulsed-amperometric detection, an anion-micromembrane suppressor was used to raise the pH of the effluent to above 12 without dilution. The HPIAC system provides a sophisticated method for the rapid and sensitive detection of antigenic oligomeric carbohydrates in biological samples and is proposed as an alternative to quantitative enzyme-linked immunosorbent assay techniques.