RESUMO
A cascade 6-endo-dig cyclization reaction was developed for the switchable synthesis of halogen and non-halogen-functionalized pyrazolo[3,4-b]pyridines from 5-aminopyrazoles and alkynyl aldehydes via C≡C bond activation with silver, iodine, or NBS. In addition to its wide substrate scope, the reaction showed good functional group tolerance as well as excellent regional selectivity. This new protocol manipulated three natural products, and the arylation, alkynylation, alkenylation, and selenization of iodine-functionalized products. These reactions demonstrated the potential applications of this new method.
Assuntos
Produtos Biológicos , Iodo , Aldeídos/química , Iodo/química , Estrutura Molecular , Pirazóis , Piridinas/química , PrataRESUMO
An unexpected global disorder (co-existing rotational disorder and glide disorder) has been observed during an X-ray investigation of the crystal structure of (E)-[1-(biphenyl-4-yl)ethylidene]hydrazine, C14H14N2, at room temperature. When the temperature decreases to 273â K, the disorder disappears, but the quality of the data set is low. The diffraction data were collected again at 110â K. Differential scanning calorimetry (DSC) analysis and polarizing-microscopy experiments, as well as a fourth set of single-crystal data collected at 283â K, proved that the order-disorder transformation occurs continuously. The analyses of these crystal structures and full-range relaxed potential energy surface scans showed that this kind of global disorder is not very difficult to achieve inside the crystal. Experimental and theoretical studies via UV-Vis and fluorescence spectra impart an understanding on the prediction methods of optical properties, which are essential for the rational design of biphenyl-based materials with pre-defined properties.