DMAP catalysed vinylogous Rauhut–Currier reaction of allenoates with para-quinone methides

The hitherto unknown, organocatalysed (DMAP) vinylogous Rauhut-Currier reaction of 2,3-butadienoates with para-quinone methides has been achieved. The products, diarylmethane substituted allenoates, are formed in high to excellent yields under mild reaction conditions.     

Enhancement of electroosmotic flow using zwitterionic additives

Zwitterionic additives provide a means of altering the EOF without increasing conductivity. The magnitude of the EOF in a bare silica capillary increased by as much as 69% upon addition of 500 mM of zwitterion to the running buffer. The EOF enhancement increases linearly with the zwitterion concentration. With zwitterionic additives of the form +NH3-(CH2)n-COO-, the magnitude of the EOF increase is directly related to the number of methylene groups, (n), which ranges from n = 1 to 7. The endgroups on the zwitterions also affect the EOF enhancement. The effect of Z1-methyl (+N(CH3)3CH2CH2CH2SO3-) on EOF was not a function of either the buffer cation or pH. The EOF enhancement is a function of the dielectric increment of the additive and the nature of the amine functionality.     

Zwitterionic-type molten salt-catalyzed syn-selective aza-Henry reaction: solvent-free one-pot synthesis of β-nitroamines

Zwitterionic imidazolium sulfonates are excellent catalysts for stereoselective aza-Henry reaction under solvent-free conditions. The major syn-β-nitroamine is obtained in high yields. This three-component condensation reaction catalyzed by zwitterionic-type molten salt deserves attention in its own right as a useful method.     

Synthesis and properties of copper quinonoid complexes for optical recording application

We describe the synthesis of novel quinonemonimines Cu(II) coordination complexes, of the type:

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which, in addition to their intrinsic interest, have potential application in optical recording. The following key parameters have been highlighted: (i) the presence of coordinating arms on the quinonoid core of the ligand leads to octahedral complexes with increased solubility, (ii) the presence of Cu(II) as a metal centre leads to a favourable exothermic decomposition, (iii) the presence of quinonoid moieties results in the optical absorption to be in the desired wavelength range. To cite this article: P. Braunstein et al., C. R. Chimie 9 (2006).     

The dipole approach in the lon-interaction chromatography of zwitterions— Use of a potential approximation to obtain a simplified retention equation

Summary In ion-interaction chromatography (IIC) the zwitterionic analyte is believed to interact with the stationary phase potential as a result of its electrical dipole, and to compete with the ion-interaction reagent (IIR) for available inner layer sites. The most reliable set of literature data relating to the retention behavior of zwitterions in IIC has been used for successful testing of a high surface-potential approximation which enables the fitting of retention data without detailed information about the physical and chemical properties of the mobile phase. This approach can explain quantitatively, very simply, the retention behavior of zwitterions in IIC.     

Asymmetric α-2-tosylvinylation of in situ-generated N-2-tosylvinyl proline-derived ammonium ylides

Asymmetric α-2-tosylvinylation of N-substituted proline esters using ethynyl tolyl sulfone as an electrophile was shown to proceed in good yield with high enantioselectivities without the addition of any bases. The reaction proceeds via the formation of N-2-tosylvinyl ammonium ylides.     

Synthetic procedure to pyrido[2,1-f][1,2,4]triazinium salt and related compounds

N-aminopyridyl ketone salts were reacted with formamide to yield heteroaromatic pyrido[2,1-f][1,2,4]triazinium salts. Upon storage of these products in the presence of water, formation of covalent hydrates have been observed. Reaction of the same starting compound with urethane yielded 3-chloropyrido[2,1-f][1,2,4]triazinium salt which readily reacted with secondary amines to afford 3-amino derivatives. An analogous ring closure reaction of 2-formylaminomethyl- and formaminobenzylpyridine allowed the synthesis of the partially reduced 3,4-dihydropyrido[2,1-f][1,2,4]triazinium compounds. The cyclization procedure was also applied for the synthesis of the related pyrimido[2,1-f][1,2,4]triazinium salt.     

Stationary phase-related investigations of quinine-based zwitterionic chiral stationary phases operated in anion-, cation-, and zwitterion-exchange modes

The concept of recently introduced Cinchona alkaloid-type zwitterionic chiral stationary phases (CSPs) is based on fusing key cation- and anion-exchange (CX, AX) moieties in one single low-molecular mass chiral selector (SO) with the resulting CSPs allowing enantiomer separations of a wide range of chiral ionizable analytes comprising acids, bases, and zwitterionic compounds. Herein, we report principal, systematic investigations of the ion-exchange-type retention mechanisms available with the novel zwitterionic CSPs in nonaqueous polar organic mode. Typical CX and AX processes, corresponding to the parent single ion exchangers, are confirmed also for zwitterionic CSPs. Also the mechanism leading to recognition and retention of zwitterions was found to be ion exchange mediated in a zwitterion-exchange (ZX) mode. In both AX and CX modes the additional ionizable group within the SO besides the site responsible for the respective ion-exchange process could be characterized as an intramolecular counterion (IMCI) that effectively participates in the ion-exchange equilibria and thus, contributes to solute elution. In the ZX mode both oppositely charged groups of the zwitterionic SO were found not only to be the sites for simultaneous ion pairing with the analyte but also functioned as IMCIs at the same time. The main practical consequences of the IMCI feature were significant reduction of the amounts and even elimination of acidic and basic additives required in the eluent systems to afford analyte elution while still providing faster analysis than the parent single ion-exchanger-type CSPs. The set of ten structurally different zwitterionic CSPs employed in this study facilitated the establishment of correlations between chromatographic behavior of the CSPs with particular SO elements, thereby supporting the understanding of the working principles of these novel packing materials on a molecular level.     

Two-step liquid phase microextraction combined with capillary electrophoresis: A new approach to simultaneous determination of basic and zwitterionic compounds

In this work, two-step hollow fiber-based liquid-phase microextraction procedure was evaluated for extraction of the zwitterionic cetirizine (CTZ) and basic hydroxyzine (HZ) in human plasma. In the first step of extraction, the pH of sample was adjusted at 5.0 in order to promote liquid-phase microextraction of the zwitterionic CTZ. In the second step, the pH of sample was increased up to 11.0 for extraction of basic HZ. In this procedure, the extraction times for the first and the second steps were 30 and 20 min, respectively. Owing to the high ratio between the volumes of donor phase and acceptor phase, CTZ and HZ were enriched by factors of 280 and 355, respectively. The linearity of the analytical method was investigated for both compounds in the range of 10-500 ng mL(-1) (R(2) > 0.999). Limit of quantification (S/N = 10) for CTZ and HZ was 10 ng mL(-1) , while the limit of detection was 3 ng mL(-1) for both compounds at a signal to noise ratio of 3:1. Intraday and interday relative standard deviations (RSDs, n = 6) were in the range of 6.5-16.2%. This procedure enabled CTZ and HZ to be analyzed simultaneously by capillary electrophoresis.     

Effects of novel benzotriazole based zwitterionic salt as electrolyte additive for lithium ion batteries

A novel zwitterionic lithium-benzotriazole sulfobetaine is fabricated by grafting 1,3– propanesultone onto benzotriazole and then lithiating it. The resultant lithium-benzotriazole-sulfobetaine additive is used as an electrolyte additive in lithium ion batteries in 1 M LiPF₆ (ethylene carbonate/dimethyl carbonate = 1:1). The electrolytes with the lithium-benzotriazole sulfobetaine shows higher ionic conductivities (2.18 $\times$ 10⁻² S cm⁻¹) compared to the bare electrolyte (1.07 $\times$ 10⁻² S cm⁻¹) and greater electrochemical stability (anodic limit at ~5.5 V vs. Li/Li⁺) than the pure electrolyte (anodic limit at ~4.6 V vs. Li/Li⁺). The discharge capacity of the lithium cobalt oxide/graphite cells is improved at higher C-rates with the addition of lithium-benzotriazole sulfobetaine due to increased ionic conductivity. The lithium cobalt oxide/graphite cells with the lithium-benzotriazole sulfobetaine additive also show stable cycling performance. These findings warrant the use of lithium-benzotriazole sulfobetaine as an electrolyte additive in lithium ion batteries.