The direct asymmetric allylic alkylation of beta,gamma-butenolides with MBH carbonates to access gamma,gamma-disubstituted butenolides containing adjacent quaternary and tertiary chiral centers has been presented in excellent stereoselectivities (86-96% ee, dr >95:5) and moderate to good yield (50-83%). Their synthetic utility has been well demonstrated by the facile construction of bicyclic lactones bearing 4-5 stereogenic centers.

An unprecedented ruthenium(II)-catalyzed intramolecular oxidative C-N coupling method has been developed for the facile synthesis of a variety of synthetically challenging tri- and tetrasubstituted pyrazoles. Dioxygen gas is employed as the oxidant in this transformation. The reaction demonstrates excellent reactivity, functional group tolerance, and high yields.

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Through the initial screening and further rational design of chiral cyclopentadienyl ligands, a chiral rhodium-catalyzed enantioselective 1,2-carboamidation of aromatic tethered alkenes was developed, enabling the asymmetric preparation of various chiral 2,3-dihydro-3-benzofuranmethanamides with an enantioenriched all-carbon quaternary center at the β position of amide. This robust transformation has a broad functional group tolerance, excellent enantioselectivities (up to 98.5:1.5 er), and a mild reaction conditions, releasing CO2 as the single byproduct.

Large-scale drone swarms are expected to play an important role in information acquisition, rescue search and joint fire strikes. These swarms usually adopt a clustering structure to control formation flight for fast and stable communication. Effective clustering can improve the transmission efficiency and task execution ability of the network. On the basis of uniform clustering, we establish a model with the number of unmanned aerial vehicles (UAVs) and the number of cluster heads (CHs) as variables to minimize the communication latency. Using conditional criteria, the communication delay is minimized to solve the relationship between the number of drones and the number of CHs, and this model is for clustering. A simulation platform is built with OPNET to evaluate the impact of different numbers of CHs on the network performance. According to the proposed scheme, the optimal number of CHs for 500, 300, 100 UAVs is 31, 24, 14, respectively. In the case of specific simulation parameters, these optimal numbers of CHs can achieve excellent performance in terms of delay and packet loss rate. This result has value in drone swarms clustering applications. INDEX TERMSDrone swarms, formation flight, clustering method, communication delay. 2005, respectively, and the Ph.D. degree from the

A rhodium(iii)-catalyzed tandem annulative arylation/amidation reaction of aromatic tethered alkenes was developed to deliver a variety of 2,3-dihydro-3-benzofuranmethanamine derivatives.

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Highlights A life insurer capped by the borrower's credit risk and COVID-19 outbreak is modeled. The COVID-19 outbreak, hedging, and capital regulation are considered explicitly. The effect of COVID-19 outbreak on borrowing firm deteriorates insurance activities. The COVID-19 outbreak and insurer hedging harm policyholder protection. Stringent regulation reinforces insurance instability during COVID-19 outbreak period.