A palladium-catalyzed ketoxime-chelation-assisted enantioselective C-H olefination of 2-arylcyclohex-2-enone oxime ether with a wide range of olefins as coupling partners was developed. Employing ketoxime ether as an efficient directing group, a variety of axially chiral vinyl arenes was synthesized by Pd(ii)-catalyzed C-H functionalization with excellent enantioselectivities (96 → 99% ee) under mild conditions.
Conductive ink using copper nanoparticles has attracted much attention in the printed electronics industry because of its low cost and high electrical conductivity. However, the problem of easy oxidation under heat and humidity conditions for copper material limits the wide applications. In this study, antioxidative copper inks were prepared by dispersing the nanoparticles in the solution, and then conductive copper films can be obtained after calcining the copper ink at 250 °C in nitrogen atmosphere for 30 min. A low sheet resistance of 47.6 mΩ/□ for the copper film was measured by using the four-point probe method. Importantly, we experimentally demonstrate that the electrical conductivity of copper films can be improved by increasing the calcination temperature. In addition, these highly conductive copper films can be placed in an atmospheric environment for more than 6 months without the oxidation phenomenon, which was verified by energy-dispersive X-ray spectroscopy (EDS). These observations strongly show that our conductive copper ink features high antioxidant properties and long-term stability and has a great potential for many printed electronics applications, such as flexible display systems, sensors, photovoltaic cells, and radio frequency identification.
Highly enantio-and regioselective selective (3 + 2) formal cycloaddition of b-substituted ene-and thioenecarbamates as well as cyclic enamides with quinone diimides catalyzed by a BINOL-and SPINOL-derived phosphoric acid has been reported. A wide variety of 2-amino 2,3-disubtituted indolines, including polycyclic ones, were prepared in generally high yields (up to 98%) with moderate to complete diastereoselectivities and in most cases excellent enantioselectivities (up to 99% ee).Chiral 2,3-disubstituted indolines are privileged heterocyclic rings frequently encountered in various natural bioactive alkaloids (such as (-)-physostigmine, (+)-aspidospermidine and pircrinine, Figure 1) 1 and biologically active drugs (such as pentopril and relcovaptan). 2 In addition, they have been successfully employed as chiral auxiliaries and organocatalysts in asymmetric synthesis. 3 As a result, several asymmetric catalytic approaches have been established for the construction of indoline rings. 4 Despite these elegant achievements, the development of novel asymmetric synthetic routes of 2,3disubstituted indolines is still highly desirable.
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