Iron-Catalyzed α‑Arylation of Deoxybenzoins with Arenes through an Oxidative Dehydrogenative Approach

A novel α-arylation of deoxybenzoins with non-prefunctionalized arenes is developed through an iron-catalyzed oxidative dehydrogenative approach. The reaction shows broad substrate scope and functional group tolerance and thus provides efficient access to synthetically useful 1,2,2-triarylethanones. A reasonable mechanism is also proposed

Iron-Catalyzed α‑Arylation of Deoxybenzoins with Arenes through an Oxidative Dehydrogenative Approach

A novel α-arylation of deoxybenzoins with non-prefunctionalized arenes is developed through an iron-catalyzed oxidative dehydrogenative approach. The reaction shows broad substrate scope and functional group tolerance and thus provides efficient access to synthetically useful 1,2,2-triarylethanones. A reasonable mechanism is also proposed

Iron-Catalyzed α‑Arylation of Deoxybenzoins with Arenes through an Oxidative Dehydrogenative Approach

A novel α-arylation of deoxybenzoins with non-prefunctionalized arenes is developed through an iron-catalyzed oxidative dehydrogenative approach. The reaction shows broad substrate scope and functional group tolerance and thus provides efficient access to synthetically useful 1,2,2-triarylethanones. A reasonable mechanism is also proposed

Concentrations of DDTs and Enantiomeric Fractions of Chiral DDTs in Agricultural Soils from Zhejiang Province, China, and Correlations with Total Organic Carbon and pH

Dichlorodiphenyltrichloroethanes (DDTs) are persistent organic pollutants that were widely used in China, especially eastern China, as insecticides. This work investigated the concentration, dissipation, and volatilization of DDTs and enantiomeric fractions (EFs) of <i>o</i>,<i>p</i>′-DDD and <i>o</i>,<i>p</i>′-DDT in agricultural soils collected in 2006 from 58 sites in Zhejiang province. Correlations between DDT residues and soil properties were assessed to determine the effect of soil properties on the environmental attenuation of DDTs. High concentrations and detection frequencies were found for DDTs in agricultural soils in the region even though large-scale use of DDTs was banned over 20 years ago. The amount of DDTs was about 485 tons in the upper 20 cm of the soil column of cropland in the province in 2010, with a dissipation half-life of ∼9 years. The mass flux of DDTs was 43 ng m^–2 h^–1, which corresponds to emissions of 7.6 tons with an emission factor of 1.6% in 2006. The low <i>p</i>,<i>p</i>′-DDT/<i>p</i>,<i>p</i>′-DDE ratios and high <i>o</i>,<i>p</i>′-DDT/<i>p</i>,<i>p</i>′-DDT ratios suggest that there were no recent inputs of DDTs but fresh application of dicofol, which contains DDT (<i>o</i>,<i>p</i>′-DDT in particular) impurities. The significant positive correlation between concentrations of DDTs and total organic carbon content (TOC) indicates the distribution of DDTs fit a typical “secondary distribution” pattern. DEVrac of <i>o</i>,<i>p</i>′-DDD, which is defined as the absolute value of EFs subtracted from 0.5, was significantly related with most of the physicochemical and microbial soil properties. The most significant correlation is that between DEVrac of <i>o</i>,<i>p</i>′-DDD and soil pH (<i>p</i> < 0.001), indicating that the soil pH plays a key role in enantioselective residues of DDTs

NH₄HF₂ as a Selective TBS-Removal Reagent for the Synthesis of Highly Functionalized Spiroketal via Tandem Deprotection/Spiroketalization Procedure

NH₄HF₂ has been used for the first time to selectively remove the TBS protecting groups from diol ketone precursors in the synthesis of highly functionalized spiroketals. This method allows the synthesis of [5,6], [6,6], and [6,7] spiroketal skeletons, as well as benzannulated spiroketal with retention of acid-sensitive groups. In this way, spiroketals can be synthesized with diverse substituent groups in the skeleton or on side chains. To demonstrate the utility of this methodology, the diverse transformations of highly functionalized spiroketal <b>3f</b> were also investigated

Assessing and Forecasting Atmospheric Outflow of α-HCH from China on Intra-, Inter-, and Decadal Time Scales

Atmospheric outflow of α-HCH from China from 1952 to 2009 was investigated using Chinese Gridded Pesticide Emission and Residue Model (ChnGPERM). The model results show that the outflows via the northeast boundary (NEB, longitude 115–135 °E along 55 °N and latitude 37–55 °N along 135 °E) and the mid-south boundary (MSB, longitude 100–120 °E along 17 °N) of China account for 47% and 35% of the total outflow, respectively. Two climate indices based on the statistical association between the time series of modeled α-HCH outflow and atmospheric sea-level pressure were developed to predict the outflow on different time scales. The first index explains 70/83% and 10/46% of the intra-annual variability of the outflow via the NEB and MSB during the periods of 1952–1984 and 1985–2009, respectively. The second index explains 16% and 19% of the interannual and longer time scale variability in the outflow through the NEB during June–August and via the MSB during October–December for 1991–2009, respectively. Results also revealed that climate warming may potentially result in stronger outflow via the NEB than the MSB. The linkage between the outflow with large scale atmospheric circulation patterns and climate warming trend over China was also discussed

Decabrominated Diphenyl Ethers (BDE-209) in Chinese and Global Air: Levels, Gas/Particle Partitioning, and Long-Range Transport: Is Long-Range Transport of BDE-209 Really Governed by the Movement of Particles?

In this paper, we report air concentrations of BDE-209 in both gas- and particle-phases across China. The annual mean concentrations of BDE-209 were from below detection limit (BDL) to 77.0 pg·m^–3 in the gas-phase and 1.06–728 pg·m^–3 in the particle-phase. Among the nine PBDEs measured, BDE-209 is the dominant congener in Chinese atmosphere in both gas and particle phases. We predicted the partitioning behavior of BDE-209 in air using our newly developed steady state equation, and the results matched the monitoring data worldwide very well. It was found that the logarithm of the partition quotient of BDE-209 is a constant, and equal to −1.53 under the global ambient temperature range (from −50 to +50 °C). The gaseous fractions of BDE-209 in air depends on the concentration of total suspended particle (TSP). The most important conclusion derived from this study is that, BDE-209, like other semivolatile organic compounds (SVOCs), cannot be sorbed entirely to atmospheric particles; and there is a significant amount of gaseous BDE-209 in global atmosphere, which is subject to long-range atmospheric transport (LRAT). Therefore, it is not surprising that BDE-209 can enter the Arctic through LRAT mainly by air transport rather than by particle movement. This is a significant advancement in understanding the global transport process and the pathways entering the Arctic for chemicals with low volatility and high octanol–air partition coefficients, such as BDE-209

Residues of Currently and Never Used Organochlorine Pesticides in Agricultural Soils from Zhejiang Province, China

Studies on residues of currently and never used organochlorine pesticides (OCPs) facilitate the assessment of the contamination level, distribution, sources, transportation, and trend of these selected OCPs in China. In this work we investigated the concentration levels of endosulfans and chlordane, which are currently used, and the never used aldrin and dieldrin in the province of Zhejiang, a rainy, and hilly tea-growing province in eastern China. The average/mean residue levels of OCPs was in the order ∑endosulfan > ∑chlordane > aldrin > dieldrin. The residue level was in good agreement with the usage of OCPs in Zhejiang. The spatial distribution showed that the residues of OCPs in soils from the mountain area were always higher than those in soils from the plains. The distribution characteristics were related to usage for current-use OCPs and temperature for never used OCPs. The isomeric ratios and enantiomeric fractions are useful tools to identify the degradation preference of contaminants. The wide range of ratios between <i>trans</i>-chlordane (TC) and <i>cis</i>-chlordane (CC) indicated that the degradation of the two isomers of chlordane was different at different sites. Nonracemic residues of TC and CC were observed in most soils; this is significant since the enantiomers have different toxicities

In Situ Cross-Linked Polymerization toward Poly(ether sulfone)/Poly(sodium acrylate) Hybrid Particles for the Removal of Environmental Toxins

In this study, poly­(ether sulfone) (PES)/poly­(sodium acrylate) (PSA) hybrid particles for the removal of environmental toxins were prepared via in situ cross-linked polymerization coupled with a liquid–liquid phase separation technique. The particles were characterized by Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA) and scanning electron microscopy (SEM). Batch experiments were performed to verify the adsorption capability of the particles, and the initial concentrations and pH values of the solutions significantly affected the adsorption process. In addition, both adsorption kinetic and adsorption isotherm models were used to analyze the adsorption process of Cu²⁺. The modified PES particles showed high adsorption capability for Cu²⁺ and methylene blue (MB), and a particle column was used to further study the removal ability of environmental toxins. The results indicated that the hybrid particles had great potential to remove heavy metal ions and cationic dyes for wastewater treatment on an industrial scale

Comparative Assessment of the Global Fate of α- and β-Hexachlorocyclohexane before and after Phase-Out

Technical hexachlorocyclohexane (HCH) was one of the most widely used pesticides during the 20th century. Although production and use were phased-out during the 1990s, two of its major components, α- and β-HCH, are still ubiquitous in the environment. Here, we have collected and analyzed data on concentrations of α- and β-HCH in the atmosphere and oceans, including spatial and temporal trends and seasonalities. We apply a global fate and transport model to both isomers over the period 1950 to 2050 to rationalize current levels and trends at remote locations with estimated emissions and to forecast into the near future. Our model results indicate that secondary emissions from soils and oceans are currently controlling the observed rates of decline in the atmosphere. β-HCH is declining more slowly than α-HCH due to its higher persistence, and we hypothesize that it will eventually become the predominant isomer of HCH in the environment. The model reproduces over 70% of measured concentrations of α-HCH in air and ocean water within factors of 3 and 5, respectively, and over 70% of measured concentrations of β-HCH within factors of 8 and 20, respectively. The model results are only weakly sensitive to climate change-induced trends in Arctic sea-ice cover and temperature