A Cu/CPA co-catalytic system has been developed for achieving the direct hydrophosphinylation of alkynes with phosphine oxides in delivering novel axially chiral phosphorus-containing alkenes in high yields and excellent enantioselectivities (up to 99 % yield and 99 % ee). DFT calculations were performed to elucidate the reaction pathway and the origin of enantiocontrol. This streamlined and modular methodology establishes a new platform for the design and application of new axially chiral styrene-phosphine ligands.
As the main anthropogenic source in open seas and coastal areas, ship emissions impact the climate, air quality, and human health. The latest marine fuel regulation with a sulfur content limit of 0.5% went into effect globally on January 1, 2020. Investigations of ship emissions after fuel switching are necessary. In this study, online field measurements at an urban coastal site and modeling simulations were conducted to detect the impact of ship emissions on air quality in the Greater Bay Area (GBA) in China under new fuel regulation. By utilizing a high massresolution single particle mass spectrometer, the vanadium(V) signal was critically identified and was taken as a robust indicator for ship-emitted particles (with relative peak area > 0.1). The considerable number fractions of high-V particles (up to 30−40% during ship plumes) indicated that heavy fuel oils via simple desulfurization or blending processes with low-sulfur fuels were extensively used in the GBA to meet the global 0.5% sulfur cap. Our results showed that ship-emitted particulate matter and NO x contributed up to 21.4% and 39.5% to the ambient, respectively, in the summertime, significantly affecting the air quality in the GBA. The sea-land breeze circulation also played an important role in the transport pattern of ship-emitted pollutants in the GBA.
Kinetic resolution | Hydroarylation | Tetrahydroquinoline | Asymmetric catalysis | Transition metalA highly efficient kinetic resolution of racemic 2-substituted 1,2-dihydroquinolines via Rh-catalyzed asymmetric hydroarylation has been described for the first time. A variety of arylboronic acids coupled with 2-substituted 1,2-dihydroquinolines under mild reaction condition. The transformations into the enantio-enriched 2,3-diaryl-tetrahydroquinolines as well as the recovered chiral 2-aryl-dihydroquinolines were obtained with high yields and excellent enantioselectivities (86%-99% ee, s factor up to 1057).
Transition metal‐catalyzed hydrofunctionalization of methylenecyclopropanes (MCPs) has presented a considerable challenge due to the difficult manipulation of regioselectivity and complicated reaction patterns. Herein, we report a straightforward Pd‐catalyzed ring‐opening hydrophosphinylation reaction of MCPs via highly selective C−C bond cleavage. This method allows for rapid and efficient access to a wide range of chiral allylic phosphine oxides in good yields and high enantioselectivities. Additionally, density functional theory (DFT) calculations were performed to elucidate the reaction mechanism and the origin of enantioselectivity.
A catalytic method for the incorporation of an SCF3 group to tryptamine derivatives was developed via a sulfide‐catalyzed cascade trifluoromethylthiolation‐cyclization. A series of C(3)‐CF3S pyrrolidinoindolines were obtained in moderate to good yields under mild conditions. Furthermore, some enantioselectivity was observed when using chiral sulfide thiocineole as a catalyst.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.