A Zinc-Mediated Deprotective Annulation Approach to New Polycyclic Heterocycles

A straightforward approach to new polycyclic heterocycles, 1H-benzo[4,5]imidazo[1,2-c][1,3]oxazin-1-ones, is presented. It is based on the ZnCl₂-promoted deprotective 6-endo-dig heterocyclization of N-Boc-2-alkynylbenzimidazoles under mild conditions (CH₂Cl₂, 40 °C for 3 h). The zinc center plays a dual role, as it promotes Boc deprotection (with formation of the tert-butyl carbocation, which can be trapped by substrates bearing a nucleophilic group) and activates the triple bond toward intramolecular nucleophilic attack by the carbamate group. The structure of representative products has been confirmed by X-ray diffraction analysis.     

Incorporation of 2-(5-amino-3,4-dicyano-2H-pyrrol-2-ylidene)-1,1, 2-tricyanoethanide in crosslinked polyvinylformal: Formation and properties of the Copper(II) complex in the matrix

The metal(II) coordinating anion 2-(5-amino-3,4-dicyano-2H-pyrrol-2-ylidene)-1,1,2-tricyanoethanide (C₁₁N₇H ₂ ^– , L, _max = 570 nm) has been incorporated by impregnation as the sodium salt in a membrane (0.1 mm thick) of crosslinked polyvinylformal (PVF) at a concentration 1.5 × 10^–3 M. The L-doped PVF membrane, soaked in a concentrated aqueous solution of Cu²⁺ (0.1 M), changes colour from violet to blue on formation of the corresponding pure bis-pyrrolizinato complex CuL₂ (_max = 660 nm). The CuL₂-doped PVF membrane reacts in the gas phase on exposure to species (X) that are copper-coordinating ligands stronger than L, generating the reverse colour change to violet. The remarkable stability towards water of CuL₂/PVF is a promising indication for prospective use of ML₂ complexes, incorporated in polymeric membranes, for the detection of (X) species in the atmosphere even in the presence of moisture, or directly in aqueous solutions.Abbreviations average molecular weight; - wt weight - min minutes - max maximum - M molar - c concentration     

TDPAC study of Cd-doped SnO

The combination of hyperfine techniques and ab initio calculations has been shown to be a powerful tool to unravel structural and electronic characterizations of impurities in solids. A recent example has been the study of Cd-doped SnO, where ab initio calculations questioned previous TDPAC assignments of the electric-field gradient (EFG) in ¹¹¹In-implanted Sn-O thin films. Here we present new TDPAC experiments at ¹¹¹In-difused polycrystalline SnO. A reversible temperature dependence of the EFG was observed in the range 295–900 K. The TDPAC results were compared with theoretical calculations performed with the full-potential linearized augmented plane wave (FP-LAPW) method, in the framework of the density functional theory. Through the comparison with the theoretical results, we infer that different electronic surroundings around Cd impurities can coexist in the SnO sample.