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An H2O/heating or [bis(trifluoroacetoxy)iodo]benzene promoted radical cascade nitro/azide cyclization of 1-acryloyl-2-cyanoindoles with tert-butyl nitrite/azidotrimethylsilane was accomplished, which offered a series of nitro/azide-featuring pyrrolo[1,2-a]indolediones in good yields. Meanwhile, some scale-up experiments and substituent transformations were performed to test the synthetic value. In addition, the corresponding radical intermediates were successfully detected by HRMS to support the possible reaction pathway.
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A metal-free electrochemical oxidative difluoroethylation of 2-arylbenzimidazoles was accomplished, which provided an efficient strategy for the synthesis of MeCF2-containing benzo[4,5]imidazo[2,1-a]-isoquinolin-6(5H)-ones. In addition, the method also enabled the efficient construction of various difluoroethylated indolo[2,1-a]isoquinolin-6(5H)-ones. Notably, this electrochemical synthesis protocol proceeded well under mild conditions without metal catalysts or exogenous additives/oxidants added.
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A new strategy of electrochemical oxidative difluoroethylation to generate difluoroethyl radical with sodium difluoroethylsulfinate (DFES-Na) has been reported for the first time. The method allows quick access to a variety of valuable difluoroethylated azaheterocycles including oxindoles and isoquinoline-1,3-diones via radical tandem difluoroethylation/cyclization in moderate to good yields. The electrochemical cyclopropyldifluoromethylation of N-arylacrylamides also works well using this strategy. Moreover, radical capture and cyclic voltammetry (CV) experiments are also carried out to determine the proposed mechanism.
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A cyanomethylation/cyclization of aryl acetylenes/ethylenes with bromoacetonitrile was finished in a photopromoted condition, which offers an efficient and mild protocol for the preparation of cyanomethylated 7- or 5-membered N-heterocycles with good yields. Meanwhile, trichloroacetonitrile was also compatible with this radical pathway. In addition, a variety of single-crystal X-ray diffraction measurements, scaled-up operations to 1 mmol, functional group transformations of final products, light on/off experiments, and even radial inhibition studies were smoothly performed in this tandem system.
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A metal/peroxide-free involved simple cascade 6-exo-trig spirocyclization of tert-butyl nitrite with biaryl ynones has been finished, which resulted in various NO2-modified spiro[5,5]trienones with good regioselectivity/yields. A variety of scaled-up experiments, reduction/epoxidation operations, and mechanistic studies were performed to verify the merits and spirocyclization process of this radical system. Finally, the structure of the spirocycles was confirmed by single-crystal X-ray diffraction.
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Photoinduced silylation of silanes with 2-aryl-2H-indazoles was developed under mild conditions, which could efficiently result in diverse 3-silylated 2H-indazoles with good substrate scopes. A series of scaled-up to gram level and radical capture operations were performed in this system. Meanwhile, a bioactive molecule was tolerated well under typical conditions.
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Organic thiocyanates are valuable biological moities and drug-building blocks. They can also transform effectively into thioethers, thiols, alkynyl thioethers, and thiocarbamates in synthetic chemistry. With respect to the merits of thiocyanates, many chemists and our research team have developed diverse strategies to access SCN-revised heterocycles/spirocycles via an effective radical cyclization process. Hence, this review article first describes the importance/application of thiocyanates. Subsequently, it summarizes the reaction conditions, substrate scopes, and plausible mechanism, respectively, of the excellent work stated above.
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Persulfate-promoted radical cascade trifluoromethylthiolation of aryl acetylenes with AgSCF3 provides a simple reaction system for the synthesis of SCF3-substituted dibenzazepines or dioxodibenzothiazepines with good Z/E selectivity. The single-crystal X-ray diffraction data confirms the structures of the final products. A series of scaled-up experiments, further transformations, and radical inhibition experiments were operated in the reaction system.
Assuntos
Alcinos , Dibenzazepinas , Catálise , Radicais LivresRESUMO
Free radical-initiated cascade cyclization of unactivated alkenes with chloralkanes, which undergoes selective activation of the α-C(sp3)-H bond of chloralkanes, provides a protocol for the synthesis of chlorinated heterocycles or polycyclic compounds. A series of radical inhibition experiments, radical capture operations, and radical clock tests were studied in this system.
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Alcenos , Compostos Policíclicos , Ciclização , Radicais LivresRESUMO
An efficient cascade oxysulfonylation of o-vinylanilides with sodium aryl- or alkylsulfinates by a free radical mechanism has been developed, which provides a mild, facile and convenient method for the synthesis of various benzoxazines. Control experiments, including gram-level reactions and mechanistic studies, are involved in the reaction system.
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Free radical initiated bicyclization of 1,6-enynes with chloralkanes, is achieved via selective activation of the C(sp3)-H bond of the chloralkane, resulting in diverse polychlorinated/chlorinated polyheterocycles. Two kinds of transformations and a scaled-up experiment were performed to test the synthetic importance of the organic chlorides. Finally, a range of radical inhibition operations and radical clock tests were explored to support the reaction process.
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Free radical three-component nitration/spirocyclization of unsaturated sulfonamides/amides with tert-butyl nitrite was developed for the construction of diverse NO2-revised 4-azaspiro[4.5]decanes. This tandem system featured metal-free participation, simple operation, good selectivity/yields, and a green/low-cost O source. Meanwhile, one nitro-containing complex molecule and a scaled-up operation were performed well to test the synthetic potential of the cascade reaction. Isotopic labeling, radical inhibition experiments, and DFT analysis were carried out to gain insight into the reaction process.
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OBJECTIVE: Early diagnosis of infant cerebral palsy (CP) is very important for infant health. In this paper, we present a novel training-free method to quantify infant spontaneous movements for predicting CP. METHODS: Unlike other classification methods, our method turns the assessment into a clustering task. First, the joints of the infant are extracted by the current pose estimation algorithm, and the skeleton sequence is segmented into multiple clips through a sliding window. Then we cluster the clips and quantify infant CP by the number of cluster classes. RESULTS: The proposed method was tested on two datasets, and achieved state-of-the-arts (SOTAs) on both datasets using the same parameters. What's more, our method is interpretable with visualized results. CONCLUSION: The proposed method can quantify abnormal brain development in infants effectively and be used in different datasets without training. SIGNIFICANCE: Limited by small samples, we propose a training-free method for quantifying infant spontaneous movements. Unlike other binary classification methods, our work not only enables continuous quantification of infant brain development, but also provides interpretable conclusions by visualizing the results. The proposed spontaneous movement assessment method significantly advances SOTAs in automatically measuring infant health.
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Paralisia Cerebral , Lactente , Humanos , Paralisia Cerebral/diagnóstico , Movimento , Algoritmos , EncéfaloRESUMO
Correction for 'Iron-promoted free radical cascade difunctionalization of unsaturated benzamides with silanes' by Yaxin Ge et al., Chem. Commun., 2020, 56, 12656-12659, https://doi.org/10.1039/D0CC05213B.
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Iron salt/peroxide promoted cascade difunctionalization of unsaturated benzamides with silanes has been reported. It provides a convenient, highly selective, and efficient protocol for the synthesis of various silylated dihydroisoquinolinones and 1,3-isoquinolinediones. In particular, the present methodology only gives cyclization products in good isolated yields under the typical conditions.
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A copper-catalyzed C(sp3)-H bond functionalization of simple alkanes with olefinic amides was developed for the efficient synthesis of important benzoxazine derivatives. It involves new C-C and C-O bond formation in one step via a radical cascade process.
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A first free-radical triggered site-specific cross dehydrogenative coupling reaction of heterocycles with simple nitriles is developed. It allows efficient and facile access to various C-2 cyanoalkylated furans, thiophenes, indoles, and pyrroles. The extremely high selectivities in this case indicate that functionalization of an inert C-H bond could be well-controlled by radical initiation.
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An efficient hydrocyanoalkylation of unactivated alkenes with alkyl nitriles was developed. Through this free-radical-initiated selective activation of the α-C(sp(3))-H bond of acetonitriles, an anti-Markovnikov addition of an α-cyano C-centered radical to olefins has been achieved, which allows a facile and convenient access to functionalized nitriles in large scales.
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A scalable, selective, and operationally easy iodotrifluoromethylation of a wide range of alkenes and alkynes by using two simple and safe solids, sodium trifluoromethanesulfinate and iodine pentoxide, in aqueous medium has been developed. Mechanistic studies confirm that free-radical processes are involved in this system since the key radical intermediates such as CF(3) and ß-CF(3) alkyl radicals have been clearly detected by spin trapping and electron spin resonance.
Assuntos
Alcenos/química , Alcinos/química , Hidrocarbonetos Fluorados/química , Compostos de Iodo/química , Mesilatos/química , Óxidos/química , Espectroscopia de Ressonância de Spin Eletrônica , Estrutura MolecularRESUMO
An I(2)O(5)-promoted free-radical cascade trifluoromethylation/cyclization of a broad range of N-arylmethacrylamides and enynes with sodium trifluoromethanesulfinate in aqueous medium has been achieved. This strategy allows highly selective access to a variety of CF(3)-containing oxindoles and pyrrolidines. Electron spin resonance (ESR) studies indicate that atom-transfer processes are involved in this system.