4687-25-6Relevant articles and documents
Benzofurans as efficient dienophiles in normal electron demand [4 + 2] cycloadditions
Chopin, Nathalie,Gerard, Helene,Chataigner, Isabelle,Piettre, Serge R.
, p. 1237 - 1246 (2009)
Dearomatization of electron-poor benzofurans is possible through involvement of the aromatic 2,3-carbon-carbon double bond as dienophile in normal electron demand [4 + 2] cycloadditions. The tricyclic heterocycles thereby produced bear a quaternary center at the cis ring junction, a feature of many alkaloids such as morphine, galanthamine, or lunaridine. The products arising from the reaction have been shown to depend on different factors among which the type of the electron-withdrawing substituent of the benzofuran, the nature of the reacting diene, and the method of activation. In the presence of all-carbon dienes, the reaction yields the expected Diels-Alder adducts. When thermal activation is insufficient, a biactivation associating zinc chloride catalysis and high pressure is required to generate the cycloadducts in good yields and high stereoselectivities, for instance, when cyclohexadiene is involved in the process. The use of more functionalized dienes, such as those bearing alkoxy or silyloxy substituents, also shows the limits of the thermal activation, and hyperbaric conditions are, in this case, well-suited. The involvement of Danishefsky's diene induces a competition in the site of reactivity. The aromatic 2,3-carbon-carbon double bond is unambiguously the most reactive dienophile, and the 3-carbonyl unit becomes a competitive site of reactivity with benzofurans bearing substituents prone to heterocyloaddition, in particular under Lewis acid activation. The sequential involvment of both the aromatic double bond and the carbonyl moiety as dienophiles is then possible by using an excess of diene under high-pressure activation. In line with the experimental results, DFT computations suggest that the Diels-Alder process involving the aromatic double bond is preferred over the hetero-Diels-Alder route through an asynchronous concerted transition state. However, Lewis acid catalysis appears to favor the heterocycloaddition pathway through a stepwise mechanism in some cases. 2009 American Chemical Society.
Visible-Light-Induced Radical Carbo-Cyclization/ gem-Diborylation through Triplet Energy Transfer between a Gold Catalyst and Aryl Iodides
Hashmi, A. Stephen K.,Rominger, Frank,Si, Xiaojia,Zhang, Lumin
, p. 10485 - 10493 (2020/07/03)
Geminal diboronates have attracted significant attention because of their unique structures and reactivity. However, benzofuran-, indole-, and benzothiophene-based benzylic gem-diboronates, building blocks for biologically relevant compounds, are unknown. A promising protocol using visible light and aryl iodides for constructing valuable building blocks, including benzofuran-, indole-, and benzothiophene-based benzylic gem-diboronates, via radical carbo-cyclization/gem-diborylation of alkynes with a high functional group tolerance is presented. The utility of these gem-diboronates has been demonstrated by a 10 g scale conversion, by versatile transformations, by including the synthesis of approved drug scaffolds and two approved drugs, and even by polymer synthesis. The mechanistic investigation indicates that the merging of the dinuclear gold catalyst (photoexcitation by 315-400 nm UVA light) with Na2CO3 is directly responsible for photosensitization of aryl iodides (photoexcitation by 254 nm UV light) with blue LED light (410-490 nm, λmax = 465 nm) through an energy transfer (EnT) process, followed by homolytic cleavage of the C-I bond in the aryl iodide substrates.
Mercapto-amide boronic acid derivative and application thereof as MBL (metal beta-lactamase) and/or SBL (serine beta-lactamase) inhibitor
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Paragraph 0090; 0091; 0096; 0097, (2019/09/14)
The invention provides a compound of a formula (I) shown in the specification, or a conformational isomer, or an optical isomer or a pharmaceutically acceptable salt thereof. The compound of the formula (I) shown in the specification has excellent broad-spectrum inhibitory activity on MBL (metal beta-lactamase) and/or SBL (serine beta-lactamase), and can be used for preparing MBL and/or SBL inhibitors. Moreover, the compound disclosed by the invention has excellent antibacterial activity on multiple drug-resistant bacteria and is capable of reversing drug resistance of carbapenem drug-resistant bacteria, and the antibacterial effect of the compound is prior to those of positive control products such as L-captopril and tazobactam. The compound disclosed by the invention has very great potential in preparation of MBL/SBL dual inhibitors and medicines reversing drug resistance of carbapenem drug-resistance bacteria.
Facile One-Pot Transformation of Primary Alcohols into 3-Aryl- and 3-Alkyl-isoxazoles and -pyrazoles
Kobayashi, Eiji,Togo, Hideo
, p. 3723 - 3735 (2019/09/30)
Various primary alcohols were smoothly transformed into 3-aryl- and 3-alkylisoxazoles in good yields in one pot by successive treatment with PhI(OAc) 2 in the presence of TEMPO, NH 2 OH, and then NCS, followed by reaction with alkynes in the presence of Et 3 N. Similarly, various primary alcohols were smoothly transformed into 3-aryl- and 3-alkylpyrazoles in good yields in one pot by successive treatment with PhI(OAc) 2 in the presence of TEMPO, PhNHNH 2, and then NCS and decyl methyl sulfide, followed by reaction with alkynes in the presence of Et 3 N. Thus, both 3-aryl- and 3-alkylisoxazoles, and 3-aryl- and 3-alkylpyrazoles could be prepared from readily available primary alcohols in one pot under transition-metal-free conditions.
