A Cu-catalyzed regio- and enantioselective aminoboration of alkylidenecyclopropanes (ACPs) with bis(pinacolato)-diboron (B2pin2) and hydroxylamines has been described in this paper, affording the corresponding cyclopropane-containing β-aminoalkylboranes in good yields under mild conditions. Moreover, a catalytic asymmetric variant of this transformation has also been realized by using a copper complex with a (S)-BINAP ligand along with further transformation of the product to give cyclopropane-containing 1,2-aminoalcohols.
The use of the chiral 1,1'-binaphthyl scaffold to construct chiral ligands can be traced back for a long time. However, the development of bidentate NHC ligands based on the same backbone has only appeared recently. In this account, we describe the design and synthesis of a new family of chiral NHC ligands based on the 1,1'-binaphthyl scaffold and demonstrate the applications of these chiral NHC-metal complexes in the catalyzed oxidative kinetic resolution of secondary alcohols, asymmetric carbon-carbon bond formations, hydrosilylations, and cyclizations of 1,6-enynes. The chiral NHC ligands containing the 1,1'-binaphthyl backbone can be synthesized in good yields from enantiomerically pure 1,1'-binaphthyl-2,2'-diamine. These transition metals coordinated with chiral bidentate NHC ligands exhibit high catalytic activities and good enantioselectivities for a wide range of metal-catalyzed asymmetric reactions.
We report on a one-second-cadence wide-field survey for M-dwarf flares using the Tomo-e Gozen camera mounted on the Kiso Schmidt telescope. We detect 22 flares from M3–M5 dwarfs with a rise time of 5 s ≲ trise ≲ 100 s and an amplitude of 0.5 ≲ ΔF/F⋆ ≲ 20. The flare light-curves mostly show steeper rises and shallower decays than those obtained from the Kepler one-minute cadence data and tend to have flat peak structures. Assuming a blackbody spectrum with a temperature of 9000–15000 K, the peak luminosities and energies are estimated to be 1029 erg s−1 ≲ Lpeak ≲ 1031 erg s−1 and 1031 erg ≲ Eflare ≲ 1034 erg, which constitutes the bright end of fast optical flares for M dwarfs. We confirm that more than $90\%$ of the host stars of the detected flares are magnetically active based on their Hα-emission-line intensities obtained by LAMOST. An estimated occurrence rate of detected flares is ∼0.7 per day per active star, indicating they are common in magnetically active M dwarfs. We argue that the flare light-curves can be explained by the chromospheric compression model: the rise time is broadly consistent with the Alfvén transit time of a magnetic loop with a length scale of lloop ∼ 104 km and a field strength of 1000 gauss, while the decay time is likely determined by the radiative cooling of the compressed chromosphere down near to the photosphere with a temperature of ≳ 10000 K. These flares from M dwarfs could be a major contamination source for a future search of fast optical transients of unknown types.
Autism is a developmental disorder characterized by deficits in social interaction and communication, and restricted, repetitive interests. As a minor group with deficiencies, they have long been misunderstood and even discriminated against which contributes to a weak position. In addition, given the significant increase in its prevalence since it has been reported, there appears a greater necessity to gain a better understanding of this condition. To better understand the obstacles and related factors encountered by autism people, the author consulted the relevant literature and systematically analyzed the related problems encountered by autistic patients according to the existing information. The result shows that the obstacles includes female individuals' misdiagnosis, sensory problems and selective attention, reading barriers and unemployment. Despite that autistic individuals experience difficulties which are barely known by the majority of people, they also show talents what they are interested in. They pay attention to details, patterns, and things that are normally overlooked. It will be beneficial for these autistic people for their families and society to help them enter the workplace.
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