An expedient one-pot rhodium catalyzed C–H bond functionalization/electrocyclization/dehydration procedure has been developed for the synthesis of highly substituted pyridine derivatives from ...terminal alkynes and α,β-unsaturated ketoximes. The use of electron-deficient phosphite ligands is important to suppress dimerization of the terminal alkynes to enynes.
Purpose
Progress toward developing a novel radiocontrast agent for determining pO
2
in tumors in a clinical setting is described. The imaging agent is designed for use with electron paramagnetic ...resonance imaging (EPRI), in which the collision of a paramagnetic probe molecule with molecular oxygen causes a spectroscopic change which can be calibrated to give the real oxygen concentration in the tumor tissue.
Procedures
The imaging agent is based on a nanoscaffold of aluminum hydroxide (boehmite) with sizes from 100 to 200 nm, paramagnetic probe molecule, and encapsulation with a gas permeable, thin (10–20 nm) polymer layer to separate the imaging agent and body environment while still allowing O
2
to interact with the paramagnetic probe. A specially designed deuterated Finland trityl (dFT) is covalently attached on the surface of the nanoparticle through 1,3-dipolar addition of the alkyne on the dFT with an azide on the surface of the nanoscaffold. This click-chemistry reaction affords 100% efficiency of the trityl attachment as followed by the complete disappearance of the azide peak in the infrared spectrum. The fully encapsulated, dFT-functionalized nanoparticle is referred to as RADI-Sense.
Results
Side-by-side
in vivo
imaging comparisons made in a mouse model made between RADI-Sense and free paramagnetic probe (OX-071) showed oxygen sensitivity is retained and RADI-Sense can create 3D pO
2
maps of solid tumors
Conclusions
A novel encapsulated nanoparticle EPR imaging agent has been described which could be used in the future to bring EPR imaging for guidance of radiotherapy into clinical reality.
A stereo- and regioselective Diels–Alder reaction for the synthesis of highly substituted isoquinuclidines from dihydropyridines and electron-deficient alkenes has been developed. While reactions ...with activated dienophiles proceed readily under thermal conditions, the use of Lewis acid additives is necessary to facilitate cycloadditions for less reactive alkenes. This procedure affords the target compounds in high yields and diastereoselectivities.
A series of ammonium-diol and -triol ionic liquid (IL) monomers were synthesized and used in step-growth polymerization with the commercial di-isocyanate monomer, toluene-di-isocyanate (TDI), in the ...presence of free ammonium IL to form new curable ammonium-based polymerized ionic liquid/ionic liquid (PIL/IL) composite film coatings. The use of polyurethane chemistry allows for the near-complete curing of the alcohol and isocyanate monomers to yield solid, homogeneous, cross-linked polyurethane-based PIL/IL composite materials with no volatile side product formation. The physical properties and curing rates of these PIL/IL films were altered by tailoring the structures of the ammonium-alcohol IL monomers, the ratio of the linear vs. cross-linking IL monomers employed, and the amount of free IL in the curing reactions. Although ammonium-based PILs have been reported to be less thermally and electrochemically stable than their imidazolium counterparts in the literature, TGA results indicated a Tonset of up to 300 °C under air for the ammonium PIL/IL composites prepared in this study. These new PIL/IL materials were also tested as curable coatings in a toxic industrial chemical (TIC) vapor suppression and liquid uptake assay using o-dichlorobenzene (o-DCB) as a simulant for polychlorinated biphenyls. The curable PIL/IL coatings were found to suppress 88% of the o-DCB vapor on o-DCB-contaminated painted steel substrates and 79% of the o-DCB vapor on o-DCB-contaminated rubber substrates, relative to uncoated control samples. However, although effective for TIC vapor suppression, these ammonium PIL/IL coatings only sorbed less than 50% of the applied liquid o-DCB from the same test substrates, making them slightly less effective for this latter application than previously reported imidazolium-based curable PIL/IL coatings. These materials exhibited comparable ionic conductivity values to other types of PIL/IL systems previously reported in the literature. However, it was found that the more heavily cross-linked ammonium-based PIL/IL films were more prone to free IL leach-out at higher temperatures, leading to their unexpectedly higher ionic conductivity at elevated temperatures.
Display omitted
•Several novel ammonium ionic liquid alcohol monomers were synthesized for use in step-growth polyurethane polymerization.•Poly(ionic liquid)/ionic liquid composites were prepared using different ammonium monomers and degrees of cross-linking.•The composites were tested as curable films for organic vapor suppression, organic liquid uptake, and ionic conductivity.
A curable, imidazolium-based room-temperature ionic liquid (RTIL) coating system has been developed for the containment and decontamination of toxic industrial chemical-contacted surfaces. The curing ...times and mechanical properties of this poly(RTIL)/RTIL platform, which is based on alcohol–isocyanate step-growth polymerization chemistry, can be tuned by modifying the structures of the step-growth monomers, the stoichiometric ratio of linear (diol, A 2 ) to cross-linking (triol, A 3 ) RTIL monomers used, and the amount of free RTIL in the formulation. When applied to painted steel and rubber test substrates contacted with o-dichlorobenzene (o-DCB) (a polychlorinated biphenyl simulant), a 50:50 (A 2 :A 3 ) step-growth alcohol-RTIL monomer mixture cross-linked with a stoichiometric amount of a commercial di-isocyanate monomer (B 2 ) and containing 43 wt % free RTIL in the coating, reduced the o-DCB vapor amount by 96–99% compared to the uncoated, o-DCB-contacted control samples. This peelable, flexible, solid coating also removed by sorption up to >99% of the o-DCB liquid applied to the substrates after 24 h of contact.
An efficient synthetic route to a sterically crowded 1,8-diheteroarylnaphthalene-derived enantioselective fluorosensor that operates in two different detection modes utilizing fluorescence lifetime ...and intensity has been developed. Screening of palladium-catalyzed Negishi, Kumada, Suzuki, Hiyama, and Stille coupling methods showed that the latter affords highly congested 1,8-diarylnaphthalenes in superior yields. Despite severe steric hindrance, axially chiral 1,8-bis(3-(3‘,5‘-dimethylphenyl)-9-acridyl)naphthalene, 1, was obtained in 68% yield from 1,8-dibromonaphthalene, 14, and 3-(3‘,5‘-dimethylphenyl)-9-tributylstannylacridine, 13, via two consecutive Stille cross-coupling steps using tetrakis(triphenylphosphine)palladium(0) as catalyst in the presence of copper(II) oxide. The preparation of 1 involved formation of 4-(3‘,5‘-dimethylphenyl)-2-chlorobenzoic acid, 7, through microwave-assisted Suzuki coupling of 4-bromo-2-chlorobenzoic acid, 10, and 3,5-dimethylphenylboronic acid, 11, followed by regioselective amination with aniline and acridine ring construction in phosphorus oxybromide. Lithiation, subsequent treatment with trimethylstannyl chloride, and Stille cross-coupling then completed the five-reaction sequence providing 1 in 57% overall yield. The enantiomers of 1 were separated by semipreparative HPLC on a (R,R)-Whelk-O 1 column and successfully employed in enantioselective fluorosensing of N-t-Boc-protected serine, 20, glutamine, 22, proline, 23, and 2-hydoxy-2-methylsuccinic acid, 21. Fluorescence titration experiments with 23 revealed that both static and dynamic quenching occur with distinctive enantioselectivity. Addition of (R)-23 to a solution of (+)-1 in acetonitrile resulted in stronger fluorescence quenching than titration with the (S)-enantiomer of 23. The fluorescence lifetime, τ, of 1 was determined as 18.8 ns and steadily decreased to 7.5 and 6.8 ns in the presence of 0.1 M of (S)-23 and (R)-23, respectively.
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