A one-pot electrochemical synthesis of 2-aminothiazoles from active methylene ketones and thioureas mediated by NH4I.

The electrochemical preparation of 2-aminothiazoles has been achieved by the reaction of active methylene ketones with thioureas assisted by ᴅʟ-alanine using NH4I as a redox mediator. The electrochemical protocol proceeds in an undivided cell equipped with graphite plate electrodes under constant current conditions. Various active methylene ketones, including ß-keto ester, ß-keto amide, ß-keto nitrile, ß-keto sulfone and 1,3-diketones, can be converted to the corresponding 2-aminothiazoles. Mechanistically, the in situ generated α-iodoketone was proposed to be the key active species.

pH-guided fluorescent sensing probe for the discriminative detection of Cl- and Br- in human serum.

The fluctuation of the halide ion concentration in human serum is of a high clinical implication. The measurement of Cl- in human serum samples is important because Cl- is a major constituent of human serum and certain Cl- levels are indicators of many acute diseases. Real-time monitoring of Br- levels in human serum samples from patients ingesting Br- salt-based antiepileptic drugs is important to regulate potential adverse drug effects. In this study, we developed a fluorescent probe for the discriminative sensing of Cl- and Br- using a naphthalimide-benzimidazole conjugate-based Ag+ complex (L1-Ag+ complex) by exploiting the strong interaction between Ag+ and halide ions with selectivity control by pH variation. The probe exhibited a dual function of detecting Cl- and Br- at pH levels of 4.5 and 8.0, respectively. Under this two pH conditions, the probe showed a high sensitivity (limit of detection (LOD) = 43 and 5 µM for Cl- and Br-, respectively) and selectivity toward Cl- and Br-. Importantly, the probe could be applied in the quantification of Cl- and Br- levels in human serum samples under two conditions: Cl- in normal human serum and Br- in the serum-mimicking that of epileptic patients during medication.

New methods for the synthesis of 2-(2,2,2-trichloroethoxy)-(3,4,6-tri-O-acetyl-1,2-dideoxy-α-D-glucopyrano)-[2,1-d]-2-oxazoline and its use for stereo-, chemo- and regioselective glycosylation.

New methods for the synthesis of the title oxazoline 2 from the corresponding 2-deoxy-2-(2,2,2- trichloroethoxycarbonylamino)glucosyl bromide were developed. The target 2-(2,2,2-trichloroethoxy) gluco-[2,1-d]-2-oxazoline 2 can be synthesized under conditions of halide ion catalysis, using triethylamine as a base. The synthesized 2-(2,2,2-trichloroethoxy)-2-oxazoline glycosyl donor was used for stereo-, regio-, and chemoselective glycosylation reactions under extremely mild conditions. The undesirable side reaction of intermolecular aglycone transfer between an ethyl thioglycoside glycosyl acceptor and the 2-(2,2,2-trichloroethoxy)-2-oxazoline glycosyl donor occurred to a relatively small extent. Regio-, and chemoselectivity of the disaccharide synthesis with the oxazoline glycosyl donor depended on the reaction conditions.

Photoinduced Halide Segregation in Ruddlesden-Popper 2D Mixed Halide Perovskite Films.

2D lead halide perovskites, which exhibit bandgap tunability and increased chemical stability, have been found to be useful for designing optoelectronic devices. Reducing dimensionality with decreasing number of layers (n = 10-1) also imparts resistance to light-induced ion migration as seen from the halide ion segregation and dark recovery in mixed halide (Br:I = 50:50) perovskite films. The light-induced halide ion segregation efficiency, as determined from difference absorbance spectra, decreases from 20% to <1% as the dimensionality is decreased for 2D perovskite film from n = 10 to 1. The segregation rate constant (ksegregation ), which decreases from 5.9 × 10-3  s-1 (n = 10) to 3.6 × 10-4  s-1 (n = 1), correlates well with nearly an order of magnitude decrease observed in charge-carrier lifetime (τaverage  = 233 ps for n = 10 vs τavg  = 27 ps for n = 1). The tightly bound excitons in 2D perovskites make charge separation less probable, which in turn decreases the halide mobility and resulting phase segregation. The importance of controlling the dimensionality of the 2D architecture in suppressing halide ion mobility is discussed.

A single-nanozyme colorimetric array based on target-induced differential surface passivation for quantification and discrimination of Cl-, Br- and I- ions.

Abnormal levels of halide ions in drinking water have enormous threats to human health, and thus designing reliable and sensitive methods to quantify and distinguish these ions becomes extremely crucial. Herein, we develop a single-nanozyme colorimetric array based on target-induced differential surface passivation for the quantification and discrimination of Cl-, Br- and I- ions. Silver citrate (Ag3Cit) is designed as an oxidase mimic to efficiently catalyze the 3,3',5,5'-tetramethylbenzidine (TMB) chromogenic reaction. When halide ions (Cl-, Br- and I-) are present, due to their different precipitation interactions with the Ag(Ⅰ) entity in Ag3Cit, they can passivate the active surface of the nanozyme to various degrees, resulting in the inhibited TMB chromogenic reaction differentially. According to this principle, simple and efficient quantitative detection of Cl-, Br- and I- ions was achieved, with all the detection limits down to the nM level. By employing Ag3Cit as a single sensing element, a nanozyme catalysis-based colorimetric array was further established, and both individual and mixed ions were successfully distinguished by integrating the array with principal component analysis. Accurate identification of unknown samples was also verified via a double-blind protocol, indicating potential applications of the array in practice.

Molecular modification of a halohydrin dehalogenase for kinetic regulation to synthesize optically pure (S)-epichlorohydrin.

Asymmetric synthesis of chiral epichlorohydrin (ECH) from 1,3-dichloro-2-propanol (1,3-DCP) using halohydrin dehalogenases (HHDHs) is of great value due to the 100% theoretical yield and high enantioselectivity. The vital problem in the asymmetric synthesis is to prepare optically pure ECH. In this study, key amino acid residues located at halide ion channels of HheC (P175S/W249P) (HheCPS) were modified to regulate the kinetic parameters. HheCPS I81W, F86N and V94R were constructed with the corresponding halide ion channels destroyed. The catalytically efficiencies (kcat/Km) of the three mutants exhibited 0.38-, 0.23- and 0.23-fold decrease toward (S)-ECH and the reverse reaction was significantly inhibited. As the results, (S)-ECH was synthesized with >99% enantiomeric excess (e.e.) and 63.42%, 67.08% and 57.01% yields, respectively, under 20 mM 1,3-DCP as substrate. To our knowledge, this is the first investigation of the molecule kinetic modification of HHDHs and also the first report for the biosynthesis of optically pure (S)-ECH from 1,3-DCP using HHDHs.

Halide anions are formed from reactions between atomic metal anions and halogenated aromatic molecules.

Atomic metal anions (AMAs) Fe- , Cs- , Cu- and Ag- were generated in the gas phase by collisionally decomposing the corresponding metal-oxalate anion. Mass selected AMAs were allowed to react with halogenated and nitrated molecules (C6H5Cl, C6H4Cl2, C6H3Cl3, C6H5I, C6H5Br and C6H5NO2) in the collision hexapole of a triple-quadrupole mass spectrometer. Observed reactions include the predominant formation of X- (X = Cl, Br and I), as well as FeCl- , FeCl2- and FeCl3- when Fe- reacted with the mono, di and tri-chlorobenzenes; reactions between 1,4-dichlorobenzene and Cs- produced Cl- , CsCl- and CsCl2- ; reactions involving iodobenzene also produced, CsI- , CsI2- and AgI- . The results suggest that the reaction to form X- (X = Cl, Br, I and NO2) may be a promising route to improving the detection efficiency by mass spectrometry for such analytes. Copyright © 2016 John Wiley & Sons, Ltd.