Search

Keywords: phosphine; cyclization; coumarin; furanone EN phosphine cyclization coumarin furanone 1587 1592 6 07/31/23 20230815 NES 230815 Graph Furan and tetrahydrofuran heterocycles are distributed widely in nature, and they are also prevalent building blocks in a vast array of pharmaceutically active molecules (Figure 1). [116] Otherwise, coumarin-fused bicyclo[3.2.0]heptenones will be produced via a phosphine-promoted tandem [3+2] cyclization/intramolecular Wittig cyclization performing the reaction in toluene or THF, which has been disclosed in our previous study. [96] Very recently, coumarin-fused cyclopentanones were selectively afforded in moderate to good yields with excellent diastereoselectivities under phosphine catalysis of 3-benzoyl coumarin with alkynone (Scheme 1c). [95] Followed by that, we then discovered an efficient method for the synthesis of coumarin-fused bicyclo[3.2.0]heptenones via phosphine-promoted tandem [3+2] cyclization/intramolecular Wittig cyclization from 3-aroylcoumarin and alkynone (Scheme 1b). [Extracted from the article]

[96] Very recently, coumarin-fused cyclopentanones were selectively afforded in moderate to good yields with excellent diastereoselectivities under phosphine catalysis of 3-benzoyl coumarin with alkynone (Scheme 1c). [116] Otherwise, coumarin-fused bicyclo[3.2.0]heptenones will be produced via a phosphine-promoted tandem [3+2] cyclization/intramolecular Wittig cyclization performing the reaction in toluene or THF, which has been disclosed in our previous study. [95] Followed by that, we then discovered an efficient method for the synthesis of coumarin-fused bicyclo[3.2.0]heptenones via phosphine-promoted tandem [3+2] cyclization/intramolecular Wittig cyclization from 3-aroylcoumarin and alkynone (Scheme 1b). Keywords: phosphine; cyclization; coumarin; furanone EN phosphine cyclization coumarin furanone 1587 1592 6 07/31/23 20230801 NES 230801 Graph Furan and tetrahydrofuran heterocycles are distributed widely in nature, and they are also prevalent building blocks in a vast array of pharmaceutically active molecules (Figure 1). [Extracted from the article]

This study investigates the potential of permeable crystalline materials to improve the properties of recycled aggregates and recycled aggregate concrete (RAC). The use of recycled aggregates in concrete production has gained increasing attention due to environmental and economic benefits. However, the lower quality and poorer durability of recycled aggregates limit their wider application. In this study, three types of recycled aggregates were treated with permeable crystalline materials, and their water absorption and crushing index were compared before and after modification. RAC was then produced using modified recycled aggregates with different substitution rates, and their mechanical properties were evaluated. To investigate the mechanism of permeable crystalline materials modification, the microstructure of the modified RAC was observed using nuclear magnetic resonance and scanning electron microscopy. The results demonstrated that the permeable crystalline materials treatment effectively reduced the water absorption and crushing index of the recycled aggregates. The compressive strength of modified RAC also improved, with a higher modification time leading to higher strength. Furthermore, the pore distribution and microstructural denseness of the modified recycled aggregates and RAC were enhanced, as revealed by the microstructural observations. These findings suggest that permeable crystalline materials modification is a promising method for improving the properties of recycled aggregates and RAC, which could contribute to the sustainable development of the construction industry. [ABSTRACT FROM AUTHOR]

The capability of path tracking and obstacle avoidance in a complex ocean environment is the basis of the autonomous ocean vehicle voyage. In this paper, a hybrid sea surface path tracking guidance and controller for the autonomous surface underwater vehicle based on the carrot-chasing (CC) and deep reinforcement learning (DRL) is proposed. Firstly, the reference heading angle is provided by the CC algorithm, and then the DRL algorithm is used to combine it with the vehicle-borne sensor information for decision and control. The vehicle's tracking capability is self-developed through a Markov decision process model that includes states, actions, and reward functions, so as to interact and train with the surrounding environment without prior knowledge. The simulation experiments are carried out in high-fidelity sea surface environments with wind, wave and current disturbances, and the experimental results show that the proposed method can converge effectively, has high tracking accuracy and flexible obstacle avoidance ability while avoiding the calculation of complex parameters. [ABSTRACT FROM AUTHOR]

Aiming at the confrontation game problems between pursuit-evasion unmanned surface vehicles under complex multi-obstacle environment, a pursuit-evasion game strategy is proposed. Firstly, the multi-obstacle environment is set up, and the gaming situation can be judged by the perception between pursuit-evasion USVs. For the pursuers, the model training is performed based on multi-agent deep reinforcement learning, so that they can quickly plan a reasonable obstacle avoidance and pursuit route, and form an effective encirclement posture before the evader approaches the target point. Meanwhile, the credit assignment problem among the members of the pursuing group is considered. For the evader, deep reinforcement learning is combined with imitation learning to train the escape model, so that it can reach the preset point in as short a time as possible and avoid the obstacles on the way. Finally, an adversarial-evolutionary game training method under multiple random scenarios is designed and combined with curriculum learning to iteratively update the pursuit and escape models. Through the detailed comparative analysis of the model training process and simulation experiments, it is proved that the proposed two types of models have higher convergence efficiency and stability, and they can have higher intelligence to pursue, escape and avoid obstacles respectively. • A pursuit-evasion strategy is proposed for USVs under complex obstacles environment. • Based on DRL, flexible rewards guide pursuers form stable encirclement. • Combined DRL and IL, escape strategies are trained to make a evader intelligent. • An adversarial-evolutionary training method is designed to iteratively update models. [ABSTRACT FROM AUTHOR]

This paper studies a guidance and control framework of multiple autonomous surface underwater vehicles (multi-ASUV) based on deep reinforcement learning (DRL) for target tracking. The framework enables the vehicles to complete the standoff tracking and sampling tasks in a predetermined circular trajectory centered on the target and maintain predetermined relative positions during the process to obtain high-precision spatio-temporal synchronization data. We design an end-to-end architecture that maps the sensor inputs to control commands and develop autonomous capable of achieving the hybrid objective of cooperative guidance, standoff tracking, and dynamic obstacle avoidance without having prior knowledge about the goal or the environment. The results demonstrate the feasibility of the end-to-end DRL method with higher accuracy than the traditional "guidance-control" two-step method. Meanwhile, the obstacle avoidance and standoff tracking experiment for swarm and the sampling experiment in the mesoscale eddy area are stimulated further to verify the proposed framework's effectiveness and robust ability. • We propose a Deep-Reinforcement-Learning-based Multi-vehicle Cooperative Standoff Tracking Framework. • Through end-to-end control, each vehicle eventually converges to the tracking circle and distributes evenly. • This paper solve the difficult-to-eliminate uncertainty and delay caused by the combination of "guidance-control" two steps method. [ABSTRACT FROM AUTHOR]

A phosphine-promoted intermolecular annulation reaction of functionalized 3-benzoyl coumarin with alkynone has been disclosed. This reaction was found to be highly dependent on the nucleophilicity of the phosphine. Two classes of coumarin-fused cyclopentanones were selectively afforded in moderate to good yields with excellent diastereoselectivities under the mild reaction conditions. [ABSTRACT FROM AUTHOR]