An accelerating-reporting group for studies of radical heterolysis reactions and its application in an acid-catalyzed fragmentation reaction of an alpha,beta-dimethoxy radical

The 2,2-diphenylcyclopropyl group was employed to accelerate reactions of alpha-methoxy radicals containing beta-leaving groups, to trap the products of either migration or heterolysis of the leaving group, and to provide a useful chromophore for laser flash photolysis kinetic studies. The reporting group biases reactions in favor of heterolytic fragmentation and most likely intercepts radical cations in ion pairs. The 1-methoxy-1-methyl-2-(diethylphosphatoxy)-2-(2,2-diphenylcyclopropyl)ethyl radical (3a) reacted faster than the kinetic resolution of the instrument (k > 2 x 10(8) s(-1)) in all solvents studied, and the 2-acetoxy analogue (3b) reacted much faster than related radicals that do not contain the cyclopropyl group (e.g., k = 1.1 x 10(6) s(-1) in CH3CN at ambient temperature). The rate constants and Arrhenius parameters for reactions of 3b indicated that the rate-limiting step in the reaction was heterolytic cleavage. The 1,2-dimethoxy-1-methyl-2-(2,2-diphenylcyclopropyl)ethyl radical (26) reacted in a general acid-catalyzed heterolysis reaction, and rate constants for protonation of the beta-methoxy group by a series of carboxylic acids were determined. The results suggest that acid-catalyzed reactions of beta-alkoxy radicals might be employed in synthetic conversions.     

Detection and characterization of the spatial inhibition potential in electroperforated sheet materials

The spatial distribution of tiny holes in sheet materials generated by means of electrical discharges is investigated using spatial statistics techniques. It is shown that whereas the holes appear to be randomly distributed according to a Poisson point pattern, there is in fact a small region around each hole in which the generation of a new one is statistically inhibited as a consequence of the lower impedance path offered by the already made hole. The resulting pattern is known in spatial statistics as a point process with a soft-core inhibition potential, which can be characterized using the pair correlation function.     

Mass‐Spectrometric Observation of Counter Anion Production in SU‐8 Exposed to UV Light and its Use for Dill C Parameter Determination

Photopolymerization is a phenomenon that is the basis of much of today's microfabrication technology and intense research is conducted to improve its control and the characteristics of end products for a variety of applications. The design of microscopic structures often relies on the accurate knowledge and modeling of photopolymer's behavior upon exposure, i.e. the Dill parameters, for each radiation species of interest and therefore the development of flexible characterization techniques is of great importance. SU‐8 is a popular compound that is representative of a whole class that relies on cationic polymerization, where an acid is obtained via photolysis of an onium salt during exposure. Here we report on the observation of SbF₆^? via laser desorption mass spectrometry on SU‐8 exposed to UV light at the wavelength of 365 nm and demonstrate that the yield of this counter‐anion as a function of exposure is consistent with the Dill C parameter value available in the literature. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019 , 57, 967–972     

Syntheses,structure, and reactivity of acyclic enetriyne and enetetrayne derivatives

Sonogashira coupling of buta-1,3-diynylbenzene with ((2-iodophenyl)ethynyl)trimethylsilane and 1,2-diiodobenzene led to the novel enetriyne, 1-ethynyl-2-(phenylbuta-1,3-diynyl)benzene, and enetetrayne, 1,2-bis(phenylbuta-1,3-diynyl)benzene, respectively. Solid state structural and thermal analyses are also described. In solution, 1-ethynyl-2-(phenylbuta-1,3-diynyl)benzene was found to undergo thermal Bergman cyclization to afford 2-(phenylethynyl)naphthalene.     

Determination of fexofenadine in Hank's balanced salt solution by high‐performance liquid chromatography with ultraviolet detection: application to Caco‐2 cell permeability studies

The drug‐transporting proteins can affect the pharmacokinetics and pharmacodymanics of many drugs, resulting in an erratic and unpredictable pharmacological response. The Caco‐2 monolayer is routinely applied to investigate the carrier‐mediated transport of drugs. Therefore, the selection of a marker compound able to characterize the activity of such transporters is crucial. Fexofenadine (FEX), a P‐gp/OATP substrate, can be considered a suitable probe. However, in order to use be used as a marker compound, it is mandatory to develop an analytical method able to quantify this drug during the in vitro permeability assay. An HPLC method with ultraviolet detection was developed; the mobile phase consisted of phosphate buffer (pH 3.2) containing 10 m m of sodium octanosulphonate and acetonitrile (60:40) and the flow rate was set at 1.2 mL/min. Fexofenadine was eluted at 40°C, the retention time was about 4.6 min. The LOD and LOQ values were 1.9 and 6.2 ng/mL, respectively. Verapamil and ketoconazole, the most common P‐gp inhibitors, were eluted as distinct peaks of that corresponding to fexofenadine The method was successfully applied to quantify the amount of FEX transported across the Caco‐2 monolayer and could be an additional tool for those investigating the role of membrane transporters on drug absorption. Copyright © 2014 John Wiley & Sons, Ltd.