An unprecedented Ir/f‐amphox‐catalyzed asymmetric hydrogenation of racemic 2,3‐syn‐dihydroxy‐1,4‐diones is presented involving dynamic kinetic resolution, which produces (1R,2R,3R,4R)‐tetraols. This protocol constitutes an efficient and straightforward approach to accessing sugar alcohols bearing four contiguous stereocenters. The strategy exhibits various advantages over existing methods, including excellent yields (up to 98 %), exceptional stereoselectivities (up to 99:1 dr, 99.9 % ee), operational simplicity and substrate generality. Moreover, the nature of the reaction was revealed as a stepwise transformation by in situ Fourier‐transform infrared spectroscopy and isolation of intermediates.
This study presents an Rh/DuanPhos-catalyzed double asymmetric hydrogenation of α-iminoketones for accessing chiral vicinal amino alcohols, which are privileged motifs in pharmaceuticals, agrochemicals, fine chemicals, chiral auxiliaries, organocatalysts, etc. Compared with existing methods, this methodology has the following advantages, such as one-pot operation, high efficiency, operational simplicity, limited waste, broad reaction scope, and high yields (90 to 96%) and stereoselectivities (up to >99:1 dr; >99.9% ee). In addition, the mechanism of the transformation was revealed to be a stepwise reaction by isolating and analyzing reaction intermediates.
In this work, a charge storage based enhancement mode (E-mode) AlGaN/GaN high electron mobility transistor (HEMT) is proposed and studied. A stacked gate dielectrics, consisting of a tunnel oxide, a charge trap layer and a blocking oxide are applied in the HEMT structure. The E-mode can be realized by negative charge storage within the charge trap layer during the programming process. The impact of the programming condition and the thickness of the dielectrics on the threshold voltage (Vth) are simulated systematically. It is found that the Vth increases with the increasing programming voltage and time due to the increase of the storage charge. Under proper programming condition, the Vth can be increased to more than 2 V. Moreover, It is also found that the Vth increases with the decrease of the thickness of the dielectrics. In addition, it is found that the breakdown voltage of such HEMT can be adjusted by varying the gate dielectric stacks.
An unprecedented Ir/f‐amphox‐catalyzed asymmetric hydrogenation of racemic 2,3‐syn‐dihydroxy‐1,4‐diones is presented involving dynamic kinetic resolution, which produces (1R,2R,3R,4R)‐tetraols. This protocol constitutes an efficient and straightforward approach to accessing sugar alcohols bearing four contiguous stereocenters. The strategy exhibits various advantages over existing methods, including excellent yields (up to 98 %), exceptional stereoselectivities (up to 99:1 dr, 99.9 % ee), operational simplicity and substrate generality. Moreover, the nature of the reaction was revealed as a stepwise transformation by in situ Fourier‐transform infrared spectroscopy and isolation of intermediates.
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