Selective Reduction of an Aromatic Nitro Group to an Azoxy Unit in the Presence of an Aliphatic Nitro Group

Summary. Chemoselective reduction of 1-nitro-2-(2-nitro-2-methylpropyl)-benzene to 2,2′-di-(2-nitro-2-methylpropyl)-azoxybenzene was achieved with sodium borohydride in methanol in the presence of substoichiometric amounts of bismuth, whereas reduction with zinc in hydrochloric acid gave a mixture of the latter, 1-amino-2-(2-amino-2-methylpropyl)-benzene, and 3,3-dimethyl-3,4-dihydrocinnoline, and showed poor reproducibility. The crystal structure of the azoxybenzene was determined by single-crystal X-ray diffraction. Corresponding author. E-mail: siemeling@uni-kassel.de Received August 26, 2002; accepted September 2, 2002     

Comparison of the Leaching Behaviour of Alachlor and its Metabolites Under Field and Laboratory Conditions

Abstract

The aim of the investigation was to evaluate whether the results of field studies and those obtained from soil column experiments are comparable in order to describe leaching behaviour of pesticides. The fate of Alachlor and its metabolites 2,6-diethylaniline and 2-chloro-2′,6′-diethylacetanilide are described in this paper. Field leaching study and laboratory soil column experiments carried out with the formulated herbicide LASSO gave similar results. Applied Alachlor remained mostly in the top 10cm soil layer representing a limited mobility. Very small amounts of Alachlor in ground and percolated water indicated only a slight leaching potential. The calculated half-life of 15 days and 90% loss after 335 days demonstrate a remarkable persistence of alachlor. Only 2-chloro-2′,6′-diethylacetanilide but not 2,6-diethylaniline was detected in soil and percolated water. It is still uncertain if these residues originate from the formulated product or result partially from “metabolism”.

Column experiments with the same soil carried out under undisturbed conditions are a simple alternative to field studies and allow quantitative estimations. The column experiments support the assumption that most of the alachlor that cannot be found after application is not lost by wind drifting or volatilization but due to formation of bound residues.     

Reversible Migrations of Nitro Group in a Methyltetramethoxycarbonylcyclopentadiene System

Quantum chemical calculations by the density functional theory method at the B3LYP/6-311++G** level have shown that 5-nitro-5-methyl-1,2,3,4-tetramethoxycarbonylcyclopentadiene (1) and 5-nitro-2-methyl- 1,3,4,5-tetramethoxycarbonylcyclopentadiene (2) undergo interconversion by consecutive 1,5-sigmatropic shifts via the formation of an unstable isomer, 5-nitro-1-methyl-2,3,4,5- tetramethoxycarbonylcyclopentadiene (3), rather than through the NMR-detected 1,3-shift of the nitro group over the cyclopentadiene ring perimeter. According to calculations in the gas phase, isomer 3 is by ΔE _ZPE of 3.6 kcal/mol less stable than isomer 1, while the activation barrier of the stepwise 1 → 2 process is 24.5 kcal/mol, which agrees well with NMR data (ΔG_25C^≠, chlorobenzene, 26.5 kcal/mol).     

A Simple Method for the Synthesis of Nitriles from Primary Amides Under Neutral Conditions

1-(3-Dimethylaminopropyl)-3-ethylcarbodiimidehydrochloride (EDCI) is a very useful reagent for the preparation of nitriles in good yields under neutral conditions.     

Synthesis of Fluorinated Heteroaromatics through Formal Substitution of a Nitro Group by Fluorine under Transition‐Metal‐Free Conditions

An efficient and transition‐metal‐free approach was developed to access a series of fluorinated heteroaromatics in moderate to excellent yields. This one‐pot procedure features a triple‐relay transformation of rapid dearomatization, fluorination, and rearomatization processes, which represents a conceptually novel strategy of combining partial hydrogenation and electrophilic fluorination.     

Synthesis and Insecticidal Activities of Novel Analogues of Chlorantraniliprole Containing Nitro Group

Twelve novel analogues of chlorantraniliprole containing nitro group were synthesized,and their structures were characterized by 1H NMR and high-resolution mass spectrometry(HRMS).Their evaluated insecticidal activities against oriental armyworm(Mythimna separata) indicate that the nitro-containing analogues showed favorable insecticidal activities,while the activity of compounds 5g at 0.25mg/L was 40%,but still lower than chlorantraniliprole.     

Stability Monitoring of Electrolytic Conductivity Reference Materials Under Repeated Use Conditions by the Primary Measurement Method

This work presents the results from stability studies for several electrolytic conductivity (EC) reference materials submitted to repeated use conditions, as required by the last version of the ISO 17034 standard. Eight batches of reference materials, composed of water or water/n-propanol and HCl or KCl (at different concentrations), were studied, with nominal EC values ranging from 5 to 12,825 µS·cm−1. The materials were submitted to a simulation of repeated use, with the manipulation of bottles once a week and their storage under refrigeration with air gaps inside them. They were then analyzed once a month by the EC primary measurement method. The measurement results were evaluated to check for deviations from conventional long-term stability monitoring and for variation trends using normalized error and linear regression statistical tests. The results indicated that the repeated use simulation caused deviations in the EC for the 100 and 500 µS·cm−1 reference materials and variation trends in the EC for the 5000 and 12,825 µS·cm−1 reference materials. From the results, the uncertainty related to stability monitoring under repeated use conditions was calculated for each reference material.     

后重氮偶合法制备含硝基偶氮苯咔唑类聚合物

后重氮偶合;咔唑;生色团;后重氮偶合法制备含硝基偶氮苯咔唑类聚合物     

Determination of the Inductive Constant of the Succinimide Group from the Reaction Series of Thermolysis of Nitro Esters

The inductive constant σ* of the succinimide group was determined using the previously obtained equation correlating the rate constant k _l ofliquid-phase homolysis of the O-NO₂ bond in nitro esters with the σ* constants of electronegative substituents. The kinetics of thermolysis of N-nitroxymethyl- and N-(2-nitroxyethyl)succinimide in the melt and solutions was studied manometrically. Adequate data for k _l were obtained. The σ* constant of the succinimide group was determined to be 4.5. The σ* constants for the phthalimide group and some other imide substituents were determined by a similar procedure.__________Translated from Zhurnal Obshchei Khimii, Vol. 75, No. 6, 2005, pp. 954–957.Original Russian Text Copyright © 2005 by Goncharov, Dubikhin, Nazin, Fedorov, Shastin.     

Transient Voltammetry Under Hydrodynamic Conditions

The channel flow cell has been shown to be a powerful tool with which to study analytical, mechanistic and kinetic processes. In this article we describe a numerical strategy which provides an efficient and flexible alternative to previous computational techniques for simulating channel electrode problems. It is demonstrated that the finite element method can accurately simulate the transient currents measured in hydrodynamic systems under mass transport control, at both macro- and micro-electrodes. Results are compared to analytical theory where available, and to previously established methods of simulation.     

Substitution Reaction of Nitro Group on α-Nitrostyrene by Organozinc Halides under Microwave Irradiation

In recent years, organozinc reagents (R2Zn and RZnX) have been proved to be very useful in organic synthesis. [1] And the application of organozinc halides (RZnX) in organic synthesis has been extensively investigated.     

Asymmetric Organocatalysis Under Mechanochemical Conditions

Asymmetric organocatalysis is a robust methodology providing access to numerous valuable compounds while having green chemistry principles in mind. The realization of organocatalytic transformation under solvent-free mechanochemical conditions brings additional benefits in terms of yields, selectivities, and, last but not least overall improved sustainability. This overview describes developments in the use of mechanochemistry as a vehicle for asymmetric organocatalytic transformations. The material is organized according to main catalytic activation modes, starting with covalent activation and proceeding to non-covalent activation modes. The advantages of mechanochemical organocatalytic reactions are particularly highlighted, but in some cases also, limitations are mentioned. Possibilities for target compound synthesis are also discussed.     

Tetrahydropyranylation of Alcohols Under Solvent-Free Conditions

A green, efficient, and large-scale method for tetrahydropyranylation of alcohols in the presence of a catalytic amount of pyridinium chloride at room temperature under solvent-free conditions is reported.     

Studies on the Reduction of the Nitro Group in 4-Nitroindazoles by Anhydrous SnCl2 in Different Alcohols

The bakers' yeast reduction of a number of alkyl levulinates occurs in good to moderate yields to give the corresponding (S) alcohols in > 98% ee. The (S) alcohol la has been converted to synthetically useful (S)- or (R)-4- methylbutyro-lactone and (S)-(+)-l,4-pentanediol in good yields.     

Transport of Pesticides Under Aquifer Conditions

Abstract

Pesticide transport was determined in a quarternary coarse grained aquifer which was characterized by low organic carbon content. Water spiked with the pesticides atrazine, chlortoluron, isoproturon, simazine and terbuthylazine and chloride salt as conservative tracer, was injected in the aquifer. Mean residence times (MRT) of pesticides were generally 1.5 to 3 times higher than the MRT of the tracer. Sediment retention capacity calculated from experimental data yielded generally small values below 250 ng/kg sediment. Retardation characteristics were in the order of magnitude expected from literature data on organic carbon/water partition coefficients. Transport of pesticides was due to convection and dispersion whereas adsorption and degradation was low.     

RuCl3-DCHA Catalyst System: A Selective Aerobic Oxidation of Primary Benzylic Alcohols Under Mild Conditions

The aerobic oxidation of benzylic alcohols to their corresponding aldehydes was performed in a RuCl₃ · 3H₂O–dicyclohexylamine (DCHA) catalyst system under ambient atmosphere at room temperature. It is noteworthy that the RuCl₃ · 3H₂O–DCHA system displayed a preference for the primary versus secondary benzylic alcohols in both intermolecular and intramolecular competition experiments.