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1.
J Org Chem ; 89(12): 9051-9055, 2024 Jun 21.
Artigo em Inglês | MEDLINE | ID: mdl-38814735

RESUMO

An N-iodosuccinimide-promoted annulation of alkylidene pyrazolones with enamino esters has been explored to construct a spiropyrazolone moiety through a Michael addition/iodination/intramolecular nucleophilic substitution sequence. When the reaction was performed in acetonitrile at 100 °C, it furnished pyrrolinyl spiropyrazolones exclusively in an anti configuration through N-attacking cyclization. When the reaction was performed in dimethyl sulfoxide at 80 °C in the presence of K2HPO4, it afforded cyclopentenyl spiropyrazolones exclusively in the syn configuration through C-attacking cyclization. A plausible mechanism has also been proposed.

2.
Sci Rep ; 14(1): 770, 2024 Jan 08.
Artigo em Inglês | MEDLINE | ID: mdl-38191602

RESUMO

The characteristics of floor failure and stress changes during the mining process of protective layers are crucial for determining the effectiveness of pressure relief. Three boreholes were designed in the 21104 fully mechanized mining face of Hulusu Coal Mine to implant optical fibers into the floor of the working face. A fiber optic monitoring system was established to monitor the dynamic evolution of stress in the floor rock mass at different mining distances. Based on the information entropy in information theory, the monitoring results in the fiber optic monitoring system are calculated to obtain the stress information entropy at different mining distances. A quantitative dynamic analysis is conducted on the stress change process of the mining floor rock layer, and the stress change law of the protective layer after mining is verified through numerical calculation and similar simulation experiments. The results indicate that the evolution of stress information entropy can be divided into four stages, namely the original rock stress stage, stress concentration stage, stress release stage, and stress recovery stage. The stress information entropy shows a fluctuating upward trend, indicating that coal seam mining leads to a decrease in the orderliness of the overlying rock system and an increase in disorder. In different spatial evolution processes, there are also significant differences in stress information entropy. In the vertical direction, the entropy value of shallow rock layers changes greatly, while the entropy value of deep rock layers changes slightly. Mining leads to a decrease in the orderliness of the entire overlying rock system, an increase in stress information entropy, and a fluctuating upward trend in stress information entropy. The information entropy of overlying rock deformation and re compaction increases, but the degree of change of the former is greater than that of the latter. The Brillouin fiber optic sensing technology provides a new method for monitoring the stress changes in the protective layer mining floor, achieving quantitative analysis of floor rock failure.

3.
Org Lett ; 23(14): 5305-5310, 2021 07 16.
Artigo em Inglês | MEDLINE | ID: mdl-34213352

RESUMO

The solvent-free reaction of 4-alkylidene pyrazolones with amidines can furnish 4,5'-imidazolinyl spiropyrazolones in good to excellent yields when promoted by N-iodosuccinimide under solvent-free ball-milling conditions, whereas it almost exclusively affords 4,4'-imidazolinyl spiropyrazolones if mediated by N-bromosuccinimide in heated toluene. On the basis of this switchable cyclization strategy, a powerful metal-free method for regioselective and diastereoselective synthesis of structurally diverse 4,5'- and 4,4'-imidazolinyl spiropyrazolones has been successfully developed.

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