Remarkable regioselectivities in the course of the synthesis of two new Luotonin A derivatives

Ethyl 4-oxo-3,4-dihydroquinazoline-2-carboxylate reacts selectively with trimethylaluminium-activated 2-amino- or 4-aminobenzoic acid ethyl esters to give the corresponding anilides without self-condensation of the aminobenzoate building blocks. After propargylation, the quinazolinones were treated with Hendrickson's reagent, but only the para-substituted ester was found to undergo the expected [4 + 2] cycloaddition reaction, affording a new Luotonin A derivative. A different regioselectivity was observed with the ortho-substituted ester which affords a benzoxazinone under identical conditions. When the ester group in the ortho-substituted intermediate is replaced with a nitrile function, the outcome of the reaction with Hendrickson's reagent depends on the absence or presence of a base (DBU), yielding either a triphenylphosphonium-substituted iminobenzoxazine or a 4-cyano-substituted Luotonin A derivative.     

Studies on reaction of reduced lipoic acid with Mukaiyama reagent and its application for pharmaceutical and food analysis

A new sensitive method for the determination of lipoic acid (LA) in selected food items based on its reaction with Mukaiyama reagent (2-chloro-1-methylpyridinium iodide, CMPI) was developed. It was stated that CMPI reacts with reduced form of lipoic acid (dihydrolipoic acid, DHLA) and the stable product is produced. The spectrum of the labeled form of DHLA exhibits new band at 312?nm. Based on its spectral characteristics new spectrophotometric and UV–high-performance liquid chromatography (HPLC) methods of LA determination were elaborated. Both methods allowed determination of the analyte in the concentration range of 5?×?10^?6–1?×?10^?4?mol?L^?1 with limit of detection 0.39?×?10^?6 and 0.77?×?10^?6?mol?L^?1 for spectrophotometric and HPLC method, respectively. The practical usability of newly developed methods was checked by determination of lipoic acid contents in its pharmaceutical preparate Revitanerw. The proposed method was precise and accurate. The relative error of determination did not exceed ±0.067%. As chromatographic method allowed the determination of analyte in the presence of complex matrix, it was applied for assay of free fraction of α-lipoic acid in selected food items. A procedure of LA isolation from biological matrix was developed. The extraction with dichloromethane allowed quantitative recovery at 102.94?±?4.20%. The green barley appeared to be the richest source of LA.     

Introduction of (2‐CF3)Phenyl Group via Nickel‐catalyzed C–Cl Bond Activation and Arylation

A simple and mild catalytic arylation via C–Cl bond activation is described. The phenyl group containing a 2‐trifluoromethyl group was introduced into the aromatic imine molecules through C,C‐coupling reaction between chloroarenes and the organozinc reagent, bis(2‐(trifluoromethyl)phenyl)zinc, with tetrakis(trimethylphosphine)nickel(0) complex as an effective catalyst. Under catalytic conditions chlorinated benzalimines were quantitatively converted into the expected benzalimines with trifluoromethyl group(s).     

Acetylcholinesterase immobilised eggshell membrane-based optical biosensor for organophosphate detection

The development of an optical biosensor for the determination of malathion based on acetylcholinesterase (AChE) inhibition using Ellman’s reagent is reported. The AChE has been immobilised onto the eggshell membrane (ESM) using glutaraldehyde as a cross-linking agent. Scanning Electron Microscopic (SEM) studies and Fourier Transformed Infra-Red (FTIR) characterisations have been carried out to affirm the successful immobilisation of AChE onto the ESM. Under optimum conditions, the developed biosensor estimated the pesticide concentration in the range of 0.1–50 ng/mL with a limit of detection (LOD) of 0.1 ng/mL within 30 min. Parameters affecting the biosensor response such as concentration of enzyme, substrate and inhibition time were optimised. The stability and reusability of the AChE/ESM sensor have been observed as 31 days at 4°C and two times, respectively.     

IMSFT法中化学和物理发泡剂的选择问题

研究了IMSFT法中选择化学及物理发泡剂的一般要求,探讨了几类较为可行的化学发泡剂的发泡机理以及部门物理发泡剂的性能,并进行了比较。     

丙二酰氧基硼氢化钠与烯烃的选择性硼氢化

叙述了丙二酰氧基硼氢化钠的制备及其原位与烯烃的选择性硼氢化反应。通过化学反应证实,丙二酰氧基硼氢化钠在THF中与脂肪族末端烯烃例如1-庚烯的硼氢化反应,有98%的硼原子加到双键末端碳原子上,只有2%的硼原子加到2-位上,生成单取代的有机硼化合物,即丙二酰氧基硼氢化钠是一个单官能硼氢化试剂。     

等色点光度法测定指示剂类有机试剂的纯度

等摩尔连续变化法中部分吸收光谱（ＣＲ〉ｎＣＭ）相交形成一个等色点,另一部分光谱（ＣＲ〈ｎＣｍ）则不交于该等色点。我们利用等色点吸光度值与另一部分光谱在该波长吸光度值之比,可计算出试剂纯度。方法不依金属为基准,操作简单,结果可靠。     

用钙试剂羧酸钠为指示剂络合滴定法测定降水中钙离子

提出用钙试剂羧酸钠作指示剂络合滴定法测定降水中钙离子,在自然条件下终点的观察即能顺利进行。同《空气和废气监测分析方法》中钙离子络合滴定法相比较,此法终点敏锐,回收率为９５％～１００％,相对标准偏差均小于２．７％,方法简便、快速、准确、灵敏。具有推广性。     

Mechanism of the interaction of color reagent 1, 3-N, N’-bis-4-(4’-nitro benzenediazo) phenyl squaraine with oxoacid anions

By AM1 method, the interactions between 1, 3-N, N’ -Bis-4-(4’ -nitro benzenediazo) phenyl squaraine (BNBPS) and several oxoacid anions have been studied on the basis of the proposed model. The mechanism of the color reactions is suggested and the answers to the question of whether or not BNBPS colorates with HCO ₃ ^- , CO ₃ ^2- , NO₂, NO₃ etc. are given. It is theoritically predicted that BNBPS might be used as the color reagent for SO ₄ ² . Project supported by the National Natural Science Foundation of China (Grant No. 29706115).     

Replacement of Volatile Acetic Acid by Solid SiO2@COOH Silica (Nano)Beads for (Ep)Oxidation Using Mn and Fe Complexes Containing BPMEN Ligand

Mn and Fe BPMEN complexes showed excellent reactivity in catalytic oxidation with an excess of co-reagent (CH₃COOH). In the straight line of a cleaner catalytic system, volatile acetic acid was replaced by SiO₂ (nano)particles with two different sizes to which pending carboxylic functions were added (SiO₂@COOH). The SiO₂@COOH beads were obtained by the functionalization of SiO₂ with pending nitrile functions (SiO₂@CN) followed by CN hydrolysis. All complexes and silica beads were characterized by NMR, infrared, DLS, TEM, X-ray diffraction. The replacement of CH₃COOH by SiO₂@COOH (100 times less on molar ratio) has been evaluated for (ep)oxidation on several substrates (cyclooctene, cyclohexene, cyclohexanol) and discussed in terms of activity and green metrics.