Solvent Effects on the Radical Copolymerizabilities of Styrene with p-Substituted N,N-Diethylcinnamamides and of p-Substituted Styrenes with Methyl Vinyl Sulfoxide

Radical copolymerizations of styrene (St) with p-substituted-N, N-diethylcinnamamides (I) and also of p-substituted styrenes (II) with methyl vinyl sulfoxide (MVSO) have been carried out in benzene, acetic acid or acetonitrile. The monomer reactivity ratios (r₁) were found to be affected by the solvents, p values obtained by using the modified Hammett equation, i. e., log(1/r₁) = ρσ + γ E_R, were also found to be altered by the solvents. The results are discussed in terms of the solvent effect in the transition state of the propagation reaction.     

Alternating copolymer based on sulfonamide‐substituted phenylmaleimide and vinyl monomers as polymer electrolyte membrane

The alternating copolymerization of phenylmaleimide (PMI) with a pendant sulfonamide acid group (sa‐PMI) and n‐butyl vinyl ether (BVE) as the aliphatic vinyl monomer afforded proton‐conducting polymer electrolytes—sa‐PMI‐BVEs—and their properties were compared with those of sa‐PMI‐STs that were synthesized from sa‐PMI and styrene. The ion exchange capacities (IECs) can be easily controlled by partly replacing sa‐PMI with unsubstituted PMI. sa‐PMI‐BVE is more flexible than sa‐PMI‐ST, and therefore, forms thin membranes even at high IECs, while sa‐PMI‐ST membranes are rigid and brittle. However, sa‐PMI‐BVE exhibits rather low thermal and oxidative stability. To realize polymer electrolyte membranes with reliable mechanical strength and a high IEC, gel‐filled membranes were prepared by polymerization in the presence of a small amount of a crosslinker, divinylbenzene, in porous polytetrafluoroethylene membranes. By using the gel‐filled membrane, H₂/O₂ fuel cells could be operated at 80 °C with reasonable performance. © 2013 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2013     

Designer Lewis acid based on molecular recognition

Abstract

A Lewis acid is an excellent candidate as a proton substitute in man-made organic reactions. The observation that organoaluminum compounds immediately ignite when exposed to air, a reflection of the high affinity of aluminum for oxygen, inspired us to devise a new series of reagents based on that metal. Our goal was to engineer an artificial proton of a special shape, which could be utilized as an effective tool for chemical reactions, by harnessing the high reactivity of the aluminum atom towards oxygen. Such a concept was initially researched by examining the influence of a specially designed organometallic reagent on a typical organic reaction. The successful diastereoface discrimination observed in the alcohol synthesis induced us to examine the more intricate question of enantioface differentiation. Creation of new chirality in a product molecule requires the use of a chiral catalyst. Therefore, an investigation was launched to determine whether a chiral Lewis acid could possibly achieve the desired result.     

General Method for the 11C‐Labeling of 2‐Arylpropionic Acids and Their Esters: Construction of a PET Tracer Library for a Study of Biological Events Involved in COXs Expression

Cyclooxygenase (COX) is a critical enzyme in prostaglandin biosynthesis that modulates a wide range of biological functions, such as pain, fever, and so on. To perform in vivo COX imaging by positron emission tomography (PET), we developed a method to incorporate ¹¹C radionuclide into various 2‐arylpropionic acids that have a common methylated structure, particularly among nonsteroidal anti‐inflammatory drugs (NSAIDs). Thus, we developed a novel ¹¹C‐radiolabeling methodology based on rapid C‐[¹¹C]methylation by the reaction of [¹¹C]CH₃I with enolate intermediates generated from the corresponding esters under basic conditions. One‐pot hydrolysis of the above [¹¹C]methylation products also allows the synthesis of desired ¹¹C‐incorporated acids. We demonstrated the utility of this method in the syntheses of six PET tracers, [¹¹C]Ibuprofen, [¹¹C]Naproxen, [¹¹C]Flurbiprofen, [¹¹C]Fenoprofen, [¹¹C]Ketoprofen, and [¹¹C]Loxoprofen. Notably, we found that their methyl esters were particularly useful as proradiotracers for a study of neuroinflammation. The microPET studies of rats with lipopolysaccharide (LPS)‐induced brain inflammation clearly showed that the radioactivity of PET tracers accumulated in the inflamed region. Among these PET tracers, the specificity of [¹¹C]Ketoprofen methyl ester was demonstrated by a blocking study. Metabolite analysis in the rat brain revealed that the methyl esters were initially taken up in the brain and then underwent hydrolysis to form pharmacologically active forms of the corresponding acids. Thus, we succeeded in general ¹¹C‐labeling of 2‐arylpropionic acids and their methyl esters as PET tracers of NSAIDs to construct a potentially useful PET tracer library for in vivo imaging of inflammation involved in COXs expression.