The development of processes that streamline the synthesis of complex, functionalized carbocycles and heterocycles remains a hotly pursued topic because their scaffolds are present in a range of bioactive molecules and electronic materials. Although the Nazarov reaction has emerged to be useful in the synthesis of carbocycles and heterocycles, using an electrocyclization to trigger a migration remains underdeveloped. By constructing several bonds in one operation, domino reaction sequences are particularly effective at improving the efficiency of synthesis. The use of transition metal catalysts has the potential to render these processes stereoselective. This review examines the use of electrocyclization-[1,2] migrations to construct molecules and is organized by the type of ring constructed and the order of the two steps in this process.
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http://dx.doi.org/10.1039/c5ob01334h | DOI Listing |
Transition metal-catalyzed carbocyclization reactions provide a powerful method for the stereoselective assembly of complex, highly substituted (poly)cyclic scaffolds. Although 1,6-enynes are common substrates for these transformations, using polysubstituted alkene derivatives to construct functionalized cyclic products remains challenging due to their significantly lower reactivity. This highlights key developments in stereoselective semi-intramolecular metal-catalyzed [(2+2)+1] and [(2+2)+2] carbocyclizations of 1,6-enynes containing 1,1-disubstituted alkenes, which produce cycloadducts with quaternary stereogenic centers.
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November 2024
Institute of Pharmaceutical Chemistry, University of Pécs, H-7624 Pécs, Hungary.
In vitro relative cytotoxicity (IC ()/IC () of ()-3-(4'-methylbenzylidene)-4-chromanone () towards human Molt 4/C8 and CEM T-lymphocytes showed a >50-fold increase in comparison to those of the respective tetralone derivative (). On the other hand, such an increase was not observed in the analogous 4-OCH ( and ) derivatives. In order to study whether thiol reactivity-as a possible basis of the mechanism of action-correlates with the observed cytotoxicities, the kinetics of the non-enzyme catalyzed reactions with reduced glutathione (GSH) and N-acetylcysteine (NAC) of and were investigated.
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December 2024
Natural and Medical Sciences Research Center (NMSRC), University of Nizwa Nizwa 616 Sulanate of Oman.
Diazo compounds are known to be good coupling partners in the synthesis of heterocycles, carbocycles and functionalized molecules a rhodium carbene-based strategy. Many heterocyclic and carbocyclic compounds, including isoquinolones and isocoumarins, quinoxalines, indoles, pyrrones, benzothazines, enaminones, benzenes and seven-membered rings, can be constructed using this rhodium-catalyzed system. The reaction mechanism involves C-H activation, carbene insertion and an annulation/functionalization sequence.
View Article and Find Full Text PDFEuro Surveill
December 2024
Research Center for Influenza and Respiratory Viruses, National Institute of Infectious Diseases, Tokyo, Japan.
An outbreak of influenza A(H1N1)pdm09 viruses exhibiting cross-resistance to oseltamivir and peramivir occurred in Yokohama, Japan, in September 2024. Among 24 students in a class, 11 were diagnosed with influenza or influenza-like illness, and viruses harbouring the NA H275Y and HA Q210H substitutions were isolated from four. Deep sequencing analysis confirmed the clonal spread of these mutants.
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November 2024
Frontier Institute of Science and Technology (FIST), Xi'an Jiaotong University Yanxiang Road 99 Xi'an 710045 China
The first Ni-catalyzed asymmetric decarboxylative strategy for the construction of carbocycles with contiguous quaternary all-carbon stereocenters is reported. The key to the success of these reactions is the utilization of rationally designed allenylic methylene cyclic carbonates as substrates with Ni catalysis. The floppy allenylic group exerts unique electronic properties on the carbonate, which allows further asymmetric nucleophilic annulations with alkenes.
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