No abstract

Asymmetric hydrogenation of tetrasubstituted alkenes is an important but challenging research topic. Herein, we report an efficient iridium-catalyzed asymmetric hydrogenation of tetrasubstituted α,β-unsaturated ketones for the synthesis of chiral 2-substituted cyclopentyl aryl ketones, an important chiral structural motif for the preparation of chiral pharmaceuticals and bioactive molecules. The reaction proceeded very well with good functional group compatibility and delivered the hydrogenated products in high yields and stereoselectivities (up to 99% yield, >20:1 dr and 99% ee). In addition, the reaction could be carried out on a gram-scale, and all four stereoisomers of the hydrogenated products bearing two contiguous stereocenters were obtained. Furthermore, the hydrogenated product can be transformed into the ERβ agonist Erteberel, and the reaction pathway was also studied via deuterium-labelling experiments.

With increasing numbers of crashes and injuries, understanding traffic accident spatial patterns and identifying blackspots is critical to improve overall road safety. This study aims at detecting blackspots using optimized hot spot analysis (OHSA). Traffic accidents were classified by their participants and severity to explore the relationship between blackspots and different types of accidents. Based on the outputs of incremental spatial autocorrelation, OHSA was then implemented on different types of accidents. Finally, the performance of OHSA in evaluating the road safety level of the proposed RBT index are examined using a binary correlation analysis (i.e., R2 = 0.89). The results show that: (1) The optimal scale distance varies from 0.6 km to 2.8 km and is influenced by the distance of the travel mode. (2) Central cities, with 54.6% of the total accidents, experiences more rigorous challenges regarding traffic safety than satellite cities. (3) There are many types of black spots in vulnerable communities, but in some specific areas, there are only black spots of non-motor vehicle accidents. Considering the practical significance of the above results, policy makers and traffic engineers are expected to give higher attention to central cities and vulnerable communities or prioritize the implementation of relevant optimization measures.