Novel use of cross-linked poly(N-isopropylacrylamide) gel for organic reactions in aqueous media

A poly(N-isopropylacrylamide) (PNIPAAm) gel cross-linked with quaternized aminoalkyls was designed. A novel recyclable system based on the external solvent-responsive oil-absorption/elution transition ability of the PNIPAAm gel matrix was then developed.     

Synthesis and structural characterization of Al4SiC4-homeotypic aluminum silicon oxycarbide, [Al4.4Si0.6][O1.0C2.0]C

A new quaternary layered oxycarbide, [Al_4.39(5)Si_0.61(5)]_Σ5[O_1.00(2)C_2.00(2)]_Σ3C, has been synthesized and characterized by X-ray powder diffraction, transmission electron microscopy and energy dispersive X-ray spectroscopy (EDX). The title compound was found to be hexagonal with space group P6₃/mmc, Z=2, and unit-cell dimensions a=0.32783(1) nm, c=2.16674(7) nm and V=0.20167(1) nm³. The atom ratios Al:Si were determined by EDX, and the initial structural model was derived by the direct methods. The final structural model showed the positional disordering of one of the three types of Al/Si sites. The maximum-entropy methods-based pattern fitting (MPF) method was used to confirm the validity of the split-atom model, in which conventional structure bias caused by assuming intensity partitioning was minimized. The reliability indices calculated from the MPF were R_wp=3.73% (S=1.20), R_p=2.94%, R_B=1.04% and R_F=0.81%. The crystal was an inversion twin. Each twin-related individual was isostructural with Al₄SiC₄ (space group P6₃mc, Z=2).     

Discrimination of enantiomeric excess of optically active trifluorolactate by distillation: Evidence for a multi-center hydrogen bonding network in the liquid state

The paper provides evidence for the existence of a multi-center hydrogen bonding network of trifluorolactate, the structure of which was elucidated by single crystal X-ray diffraction analysis, in the liquid state. We reported that the trifluorolactate experienced discrimination of its enantiomeric excess by distillation. X-ray crystallographic analyses of the single crystals of the trifluorolactates suggested that the phenomenon could be caused by a homo-chiral recognizing hydrogen bonding system. Low-angle X-ray diffraction measurement of the trifluorolactate in the liquid state showed a ca. 5 Å repeated, which indicates the existence of the hydrogen bonding network in the liquid state. Here, the chiral recognition could be caused by the electrostatic repulsion of the negative charges on trifluoromethyl groups.     

Some aspects of nitroxide-mediated living radical polymerization of N-(p-vinylbenzyl)phthalimide

The free radical polymerization of N-(p-vinylbenzyl)phthalimide (VBP) “initiated” with the adduct of 2-benzoyloxy-1-phenylethyl and TEMPO (BS-TEMPO) or TEMPO-terminated polystyrene (PS-TEMPO) in N,N-dimethylformamide (DMF) at 125 °C was found to proceed in a living fashion, providing low-polydispersity PVBP and block copolymers of the type PS-b-PVBA, where TEMPO is 2,2,6,6-tetramethylpiperidinyl-1-oxy. Unlike TEMPO-mediated styrene polymerization, the polymerization rate slightly but distinctly depended on the adduct concentration, which was interpretable as a pre-stationary behavior. The hydrolysis of those polymers gave poly(p-aminomethylstyrene) (PAMS) and PS-b-PAMS, and further treatment of the block copolymer with hydrogen chloride provided an amphiphilic block copolymer. The polymeric amphiphile was used as an emulsifier in emulsion polymerization to produce a positively charged polymeric microsphere.     

Syntheses of some 2-hydroxypyrazine 1-oxides

A series of 2-hydroxypyrazine 1-oxides were prepared from the corresponding chloropyrazines by two methods, including oxidation processes in satisfactory yields. The treatment of 2,3-diphenylpyrazine 1,4-dioxide ( 6 ) led to 2,3-dichloro-5,6-diphenylpyrazine ( 7 ) and 2-chloro-5,6-diphenylpyrazine 1-oxide ( 8 ), and the latter was converted to 5,6-diphenyl-2-hydroxypyrazine 1-oxide ( 9 ) by an alkaline hydrolysis.     

Synthesis of thiophene/phenylene co‐oligomers. IV. 6‐ to 8‐ring molecules

We report the synthesis of various thiophene/phenylene co‐oligomers with a total number of thiophene and benzene (phenylene) rings of 6 to 8. These compounds include a phenyl‐capped sexithiophene, a thienyl‐capped quaterphenylene, as well as block and alternating co‐oligomers. The synthesis is based on either the Suzuki coupling reaction or the direct dimerization coupling. The latter method produces symmetric molecules with an even total ring number. These reaction schemes enabled us to obtain the target compounds in high quality. Although the resulting materials are difficult to dissolve in organic solvents and therefore difficult to identify by usual ¹H nmr spectroscopy, they have successfully been identified through Fourier‐transform ir spectroscopy. The specific group frequencies of ring‐stretching and out‐of‐plane deformation modes are characteristic of the substitution pattern of the individual thiophene and benzene rings.     

A new synthesis of dienone lactones using a combination of hypervalent iodine(III) reagent and heteropoly acid

The oxidation of non-phenolic alkanoic acid derivatives to oxygen heterocycles was investigated; a new oxidative route to dienone lactones has been developed using a combination of hypervalent iodine(III) reagent, phenyliodine(III) bis(trifluoroacetate)(PIFA), and heteropoly acid (HPA).     

Diastereomer method for determining ee by (1)H NMR and/or MS spectrometry with complete removal of the kinetic resolution effect

[structure: see text] Using chiral auxiliaries, 2-methoxy-2-(1-naphthyl)propionic acid (MalphaNP acid) (S)-(+)-1 and its deuterium-labeled enantiomer (R)-(-)-1-d(n)() (n = 3 or 6), we have developed a new diastereomer method for determining enantiomeric excess (% ee) of chiral alcohols by (1)H NMR and/or MS spectrometry, where the kinetic resolution effect is completely excluded. The data of % ee determined by this method agree well with those calculated by weight, the average error being ca. +/-1.08% ee.     

Stepwise bromination of two acetylene molecules on a butterfly-type tetrairon core and reactivity of the resulting bromoacetylene fragment toward nucleophiles

Treatment of the acetylene-coordinated tetrairon cluster, [(eta5-C5H4Me)4Fe4(HCCH)2]+, with N-bromosuccinimide led to stepwise bromination of two acetylene ligands to form [(eta5-C5H4Me)4Fe4(HCCBr)(HCCH)]+, [(eta5-C5H4Me)4Fe4(HCCBr)2]+, [(eta5-C5H4Me)4Fe4(BrCCBr)(HCCBr)]+, and [(eta5-C5H4Me)4Fe4(BrCCBr)2]+. The reactivity of the bromoacetylene fragment in [(eta5-C5H4Me)4Fe4(HCCBr)(HCCH)]+ toward water, pyridine, and ZnMe2 was also investigated.     

Preparation of J-aggregate liposome dispersions and their chromic transformation

We report the preparation of aqueous liposome dispersions of J-aggregates formed by the amphiphilic merocyanine dye (MD). A series of liposome-forming lipids were dispersed together with MD J-aggregates at different molar ratios of MD to lipid. The MD J-aggregate dispersions prepared with 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) at the MD to DMPC ratio of 0.16 exhibit good dispersibility; that is, they can be readily redispersed without any flocculation even after their precipitation. By use of different counterions for the MD molecules, two types of J-aggregate dispersions, one that exhibits an absorption band (J-band) at 635 nm (type I) and the other at 600 nm (type II), were obtained. As an example of the use of MD J-aggregates liposome dispersions, the thermochromic transformation of MD J-aggregates was demonstrated. When the dispersions are heated, J-aggregates of type I transformed into type II at a certain temperature (T(disp)). The parameters that control the speed of the transformation and the value of T(disp) were determined.