Poly(arylene thioether)s containing 9,9′‐spirobifluorene moieties in the main chain: Masked dithiol‐based synthesis and excellent optical properties

Poly(arylene thioether)s ( PTEs ) containing 9,9′‐spirobifluorene moieties were synthesized in high yields from 9,9′‐spirobifluorene‐2,2′‐bis(N,N‐dimethylcarbamothioate) 4 as the masked dithiol and various difluoroarenes as electrophilic monomers. All PTEs showed high thermal stability: The 10% weight loss temperature as evaluated by thermogravimetric analysis was over 470 °C under both nitrogen and air atmospheres. The glass transition temperature estimated by DSC was in the range 210–270 °C. The PTEs showed high solubility in ordinary organic solvents, such as CHCl₃, NMP, and THF. Most PTEs exhibited remarkably high refractive indices ranging from 1.69 to 1.73 at 587.6 nm, whereas no or little birefringence was observed for the PTEs . © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 4192–4199, 2010     

A Refined Method for the Removal of the Methoxymethyl (MOM) Protecting Group for Carbinols with Acidic Ion-Exchange Resin

The methoxymethyl protecting group for carbinols is best removed from acid-sensitive substrates by hydrolysis in aqueous methanol using a cationic exchange resin (Dowex-50W).     

Copolymerization of 2‐isothiocyanatoethyl methacrylate and 2‐hydroxyethyl methacrylate or methacrylic acid based on a nucleophile‐tolerant property of the isothiocyanato group

Radical copolymerizations of 2‐isothiocyanatoethyl methacrylate (ITEMA) and 2‐hydroxyethyl methacrylate (HEMA) or methacrylic acid (MAA) were examined, and fundamental properties of the obtained copolymers were investigated. The copolymerizations of various ITEMA/HEMA or ITEMA/MAA compositions proceeded effectively in THF or DMF by using 2,2′‐azobisbutyronitrile (AIBN) as an initiator, keeping the isothiocyanato groups and hydroxyl or carboxyl groups unchanged. Glass transition temperatures (T_g)s of poly(ITEMA‐co‐HEMA)s ranged from 68 to 100 °C, and they were thermally stable up to 200 °C. Meanwhile, T_gs of poly(ITEMA‐co‐MAA)s (ITEMA/MAA = 91/9, 76/24) were determined to be 91 and 109 °C, respectively. However, poly(ITEMA‐co‐MAA)s were thermally unstable, and significant weight loss was observed around 180 °C, which may be due to an addition of carboxyl groups to isothiocyanato groups followed by an elimination of COS to form amide structure in the copolymers. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013 , 51, 5221–5229     

Water‐stable copolymers containing isocyanate moiety protected by hydrophobic styrene segment and their reaction with amines

Reactive isocyanate groups were protected and stabilized by the hydrophobic styrene segment and acquired high tolerance toward water. Copolymers containing isocyanate groups were synthesized by a radical copolymerization of 2‐propenyl isocyanate (2PI) and styrene (St). The stability of the obtained copolymers on water was examined to find that isocyanate groups were protected by the hydrophobic polystyrene segment and were stable on water and these isocyanates reacted with primary amines including amino acids to form urea selectively on water. Primary amines with a higher octanol‐water partition coefficient or smaller steric hindrance were more reactive to the isocyanate groups in the side chain of the copolymer. The protection of reactive isocyanate groups using the hydrophobic styrene segment did not give side products which are produced in the usual chemical protection/deprotection process. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 1934–1940     

Determination of nitrogen mustard hydrolysis products, ethanolamines by gas chromatography-mass spectrometry after tert-butyldimethylsilyl derivatization

A method for determining N-ethyldiethanolamine (EDEA), N-methyldiethanolamine (MDEA) and triethanolamine (TEA), hydrolysis products of nitrogen mustards, in water, urine and blood samples using gas chromatography-mass spectrometry (GC-MS) after derivatization by tert-butyldimethylsilylation (TBDMS) is described. The sample solution was evaporated to dryness, and reacted with N-methyl-N-(tert-butyldimethylsilyl)trifluoroacetamide (MTBSTFA) at 60 degrees C for 1h. The TBDMS derivatives were separated on a DB-5 column and detected by electron-ionization MS. The quantitation of EDEA, MDEA and TEA was performed by measuring the respective peak areas on the extracted ion chromatograms of m/z 216, m/z 202 and m/z 346, respectively, using nonadecane (C19), the peak area of which was measured at m/z 268, as an internal standard. When the water sample was initially analyzed, considerable loss of EDEA, MDEA and TEA occurred by evaporation. The addition of hydrochloric acid (HCl) to the water sample (final 1 mM), however, permitted quantitative recoveries to be achieved (88%, 88% and 79% for EDEA-(TBDMS)2, MDEA-(TBDMS)2 and TEA-(TBDMS)3, respectively). The limits of detections (LODs, scan mode, S/N = 3) were 2.5, 2.5 and 10 ng/ml for EDEA, MDEA and TEA, respectively. Ethanolamines could be also determined in urine samples (volume 0.1 ml), with reasonable recoveries of 72-100% by the addition of HCl (final 1 mM). For the analysis of serum samples, the sample was precipitated by the addition of perchloric acid (final 3.2%), and the resulting supernatant was neutralized with potassium carbonate, and then acidified by the addition of HCl. The recovery of TBDMS derivatives of ethanolamines was found to rather low (7-31%).     

Enantioselective addition of vinylzinc reagents to 3,4-dihydroisoquinoline N-oxide

Ligand 2a promotes the enantioselective addition of vinylzinc reagents to 3,4-dihydroisoquinoline N-oxide to yield chiral allylic hydroxylamines. With 0.1 equiv of the ligand, the product is obtained in up to 84% ee, whereas with 1.2 equiv of the ligand, the ee is increased to the 90-95% range with a variety of aliphatic, cyclic, and aromatic vinylzinc reagents. This method was used to synthesize the protected unnatural amino acid N-Cbz-d-1,2,3,4-tetrahydroisoquinoline-1-carboxylic acid in three steps from the allylic hydroxylamine.     

Inhibition of phosphatase activity by positively-charged cyclodextrins

[formula: see text] Aminocyclodextrins are known to bind phosphate esters such as phosphotyrosine and p-nitrophenyl phosphate. This paper describes the inhibition of phosphate ester hydrolysis, as catalyzed by lambda-protein phosphatase and acid phosphatase, that is caused by such binding interactions. ROESY studies provide structural information about the cyclodextrin-aryl phosphate complexes. In addition, these experiments are used to generate approximations of the rates of dissociation of the noncovalent complexes.     

FTIR Emission Spectra, Molecular Constants, and Potential Curve of Ground State GeO

Extensive new high-temperature, high-resolution FTIR emission spectroscopy measurements for the five common isotopomers of GeO are combined with previous diode laser and microwave measurements in combined isotopomer analyses. New Dunham expansion parameters and an accurate analytical potential energy function are determined for the ground X1Sigma+ state. Copyright 1999 Academic Press.     

Effects of ionization mode on charge-site-remote and related fragmentation reactions of long-chain quaternary ammonium ions

Comparison of collisionally activated fragment spectra of long-chain quaternary ammonium ions, formed by liquid-assisted secondary ion mass spectrometry (LSIMS) and electrospray ionization (ESI), shows the latter are dominated by radical cations while the former yield mainly even-electron charge-site-remote (CSR) fragments, similar to the report for different precursors by Cheng et al., J. Am. Soc. Mass Spectrom. 1998, 9, 840. Here, mixed-site fragmentation products (formal loss of a radical directly bonded to the nitrogen plus a radical derived from the long chain) are of comparable importance for both ionization techniques. These observations are difficult to understand if the CSR ions are formed by a concerted rearrangement-elimination reaction, since precollision internal energies of the ESI ions are much lower than those of the ions from LSIMS. Alternatively, if one discards the concerted mechanism for high-energy CA, and assumes that the even-electron fragments are predominantly formed via homolytic bond cleavage, the colder radical cations from ESI survive to the detector while the more energized counterparts from LSIMS preferentially lose a hydrogen atom to yield the CSR ions, as proposed by Wysocki and Ross (Int. J. Mass Spectrom. Ion Processes 1991, 104, 179). The present work also attempts to reconcile discrepancies involving critical energies and known structures for neutral fragments.