P-Chiral phosphorus ligands received little attention in organic chemistry until Knowles made his landmark contribution in asymmetric hydrogenation by developing the P-chiral ligands CAMP and DIPAMP. The development of P-chiral phosphorus ligands accelerated in the end of the last century with the advent of some highly efficient and renowned ligands for asymmetric hydrogenation, including BisP*, TangPhos, QuinoxP*, DuanPhos, et al. However, most reported ligands were air-sensitive, difficult to make, or lacked structural modularity, hampering their availability and applicability. The development of sterically and electronically tunable P-chiral phosphorus ligands is particularly desirable. Over the past decade, a family of sterically hindered, electron-rich, structurally tunable, and air-stable P-chiral dihydrobenzooxaphosphole ligands emerged that proved to be efficient and versatile for various asymmetric transformations. The last 5 years witnessed an increasing number of studies related to these ligands with the discovery of their unprecedented catalytic properties in various transformations. This review highlights the unique properties of P-chiral dihydrobenzooxaphosphole ligands in catalysis and their applications in the synthesis of natural products and therapeutic agents.
Three offshore areas including the East China Sea, Java Island in Indonesia, and Tampa Bay in the USA were selected as the survey regions.The effects of hydrological conditions on the abundance of microplastic in the survey marine regions were analyzed using the multiple linear regression analysis in this work.The regression models were constructed with the seawater temperature, salinity, and current velocity as independent variables.The models showed that current velocity was the most important factor that affected the accumulation or diffusion of microplastic.Seawater temperature and salinity also affected microplastic abundance by affecting the movement and density of seawater.It is feasible to establish a regression model of microplastic abundance through hydrological data in offshore areas to analyze and predict the migration and accumulation characteristics of microplastic.The interaction of hydrological factors determined the abundance of marine microplastic.
Using our 3-D long range transport handy model, we calculated and analyzed the quantity of sulfur transporting across the boundary of different countries and regions in East Asia. On the basis we discussed the budgets of sulfur and its seasonal variation on input, deposition and remnants for each country. It is shown the deposition is less than emission and the outputs are larger than the inputs in most countries of East Asia except North Korea. There are higher concentration of sulfur and more pollutants transported out of China in winter than those in summer.
We present an analysis of correlations between O 3 , NO x reaction products (NO z ), and peroxides in photochemical models for polluted environments in comparison with measurements in the vicinity of Nashville, Tennessee. This analysis is associated with the use of O 3 /NO z , H 2 O 2 /NO z , and similar ratios as indicators for the relative impact of NO x and hydrocarbons (volatile organic compounds, VOC) on ozone formation. The measurements are used both to evaluate the NO x ‐VOC indicator theory and to identify NO x ‐VOC chemistry in Nashville. Results show that a linear correlation exists between O 3 and the sum 2H 2 O 2 + NO z , consistent between models and measurements. The ratio O 3 /2H 2 O 2 + NO z has a near‐constant value in both the Nashville urban plume and surrounding rural area. A similar correlation is found with total peroxides (O 3 versus 2peroxides + NO z ) but with greater scatter. The correlations between O 3 , NO z , and peroxides are consistent with an assumed dry deposition rate of 5 cm s −1 for H 2 O 2 and HNO 3 . Changes in dry deposition and RO 2 reaction rates cause minor adjustments in the NO x ‐VOC‐indicator analysis for H 2 O 2 /NO z . Measured indicator ratios for Nashville are close to the NO x ‐VOC transition predicted by models and form an intermediate point between previous measurements for Atlanta (NO x sensitive) and Los Angeles (VOC sensitive). The model ozone production efficiency (P(O 3 )/L(NO x )) is 3–4, significantly lower than would be derived from the O 3 ‐NO z slope (5–8).
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