Electrochemical oxidation behavior of 2,4-dinitrophenol at hydroxylapatite film-modified glassy carbon electrode and its determination in water samples

Hydroxylapatite (HAP)-modified glassy carbon electrode (GCE) was fabricated and used to investigate the electrochemical oxidation behavior of 2,4-dinitrophenol (2,4-DNP) by cyclic voltammetry, differential pulse voltammetry, and chronocoulometry. The oxidation peak current of 2,4-DNP at the modified electrode was obviously increased compared with the bare GCE, indicating that HAP exhibits a remarkable enhancement effect on the electrochemical oxidation of 2,4-DNP. Based on this, a sensitive and simple electrochemical method was proposed for the determination of 2,4-DNP. The effects of HAP concentration, accumulation time, accumulation potential, pH, and scan rate were examined. Under optimal conditions, the oxidation peak current of 2,4-DNP was proportional to its concentration in the range from 2.0 × 10⁻⁶ to 6.0 × 10⁻⁴ M with a correlation coefficient of 0.9987. The detection limit was 7.5 × 10⁻⁷ M (S/N = 3). The proposed method was further applied to determine 2,4-DNP in water samples with recoveries from 96.75% to 106.50%.     

Aryne [3 + 2] cycloaddition with N-sulfonylpyridinium imides and in situ generated N-sulfonylisoquinolinium imides: a potential route to pyrido[1,2-b]indazoles and indazolo[3,2-a]isoquinolines

The aryne [3 + 2] cycloaddition process with pyridinium imides breaks the aromaticity of the pyridine ring. By equipping the imide nitrogen with a sulfonyl group, the intermediate readily eliminates a sulfinate anion to restore the aromaticity, leading to the formation of pyrido[1,2-b]indazoles. The scope and limitation of this reaction are discussed. As an extension of this chemistry, N-tosylisoquinolinium imides, generated in situ from N'-(2-alkynylbenzylidene)-tosylhydrazides via an AgOTf-catalyzed 6-endo-dig electrophilic cyclization, readily undergo aryne [3 + 2] cycloaddition to afford indazolo[3,2-a]-isoquinolines in the same pot, offering a highly efficient route to these potential anticancer agents.     

Three New C19‐Diterpenoid Alkaloids from Aconitum forrestii

A further study of the alkaloid constituents of Aconitum forrestii led to the isolation of three new C₁₉‐diterpenoid alkaloids, named 14‐acetoxy‐8‐O‐methylsachaconitine ( 1 ), 14‐acetoxyscaconine ( 2 ), and 8‐O‐ethylcammaconine ( 3 ). Their structures were determined by UV, IR, and MS, 1D‐ and 2D‐NMR analyses.     

Clean,One‐Pot Synthesis of Naphthopyran Derivatives in Aqueous Media

A general and practical one‐pot synthesis of naphthopyran derivatives using hexadecyltrimethylammonium bromide (HTMAB) as catalyst (10 mol%) is described. This method provides several advantages such as neutral conditions, high yields and simple workup procedure. The catalyst is low cost, facile, active, environmentally friendly, and reusable. In addition, water is chosen as a green solvent.     

Specific interaction between fluorine atoms and thiol groups accounting for higher domain purity and photostability in narrowband BHJ systems

In order to explore the role of fluorine atoms on photostability as well as morphology control of active layer in the presence of 1,4‐butanedithiol (BT), the four polymers with or without fluorine atoms in the backbones including polythieno[3,4‐b]thiophene/benzodithiophene, poly[(4,8‐bis‐(2‐ethylhexyloxy)‐benzo(1,2‐b:4,5‐b9)dithiophene)‐2,6‐diyl‐alt‐(4‐(2‐ethylhexanoyl)‐thieno[3,4‐b]thiophene‐)‐2‐6‐diyl)], poly[4,8‐bis(5‐(2‐ethylhexyl)thiophen‐2‐yl)benzo[1,2‐b;4,5‐b′]dithiophene‐2,6‐diyl‐alt‐(4‐(2‐ethylhexyl)‐3‐fluorothieno[3,4‐b]thiophene‐)‐2‐carboxylate‐2‐6‐diyl)], and poly[4,8‐bis‐(2‐ethyl‐hexyl‐thiophene‐5‐yl)‐benzo[1,2‐b:4,5‐b0]dithiophene‐2,6‐diyl]‐alt‐[2‐(20‐ethyl‐hexanoyl)‐thieno [3,4‐b]thiophen‐4,6‐diyl] were selected for comparison. It is found that the specimens containing fluorine atoms in polymer backbones showed of higher stability after illumination for 1 h in the presence of BT additive, contributing to the higher domain purity. The specific interaction between fluorine atoms and thiol groups was demonstrated by the appearance of novel absorption peak at 2663.1 cm^?1, in addition to the broadening of peak at 2556.2 cm^?1 ascribing to S? H stretching vibration as confirmed by Fourier transform infrared (FTIR) spectroscopy. The finding may guide the accurate use of thiols as effective solvent additive in morphology and stability optimization. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019 , 57, 941–951     

Palladium catalyzed cross-dimerization of terminal acetylenes and acrylates

A palladium catalyzed oxidative cross-coupling reaction between terminal alkynes and acrylates was developed. In the presence of palladium catalyst and copper(II) acetate as oxidant, the cross dimerization products with were formed. This protocol provides a novel method to construct the tetrasubstituted functionalized alkenes.     

初中化学基本概念学法指点

化学基本概念是初中化学教学内容的重要组成部分。因此,学生必须扎实地掌握化学基本概念,才能真正学好化学。考虑到许多化学概念在教材中集中出现,对于刚接触化学的初中生来说,学习时往往感到困惑。     

Expeditious one-pot synthesis of C3-piperazinyl-substituted quinolines: key precursors to potent c-Met inhibitors

An effective one-pot synthesis of quinolines bearing diverse C3-piperazinyl functions was developed by using a modified Friedl?nder's protocol. The method not only enables the synthesis of our early reported c-Met inhibitor on a large scale, but also provides a way to generate novel multi-substituted quinolines for further structure-activity relationship (SAR) study.