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- Intramolecular addition of acyldiazenecarboxylates onto double bonds in the synthesis of heterocyclesPublication . Prata, José V.; Clemente, Dina-Telma S.; Prabhakar, Sundaresan; Lobo, Ana M.; Mourato, Isabel; Branco, Paula SérioAppropriate aryl-substituted unsymmetrical azodicarbonyl compounds, generated from bishydrazides by oxidation, undergo intramolecular cyclisations to furnish a variety of useful heterocycles such as N-substituted oxindoles, carbostyrils, benzazepinones, benzazocinones, benzimidazolones, benzoxazinones and pyrazolones in varying degrees of efficiency. Methods are described to remove the N-acyl groups from the heteroaromatic compounds. Under mildly acidic conditions where equal opportunities are available for an ipso or a normal cyclisation it is the former process that occurs preferentially. Evidence is presented in favour of a C-to-C migration in the ipso product for the formation of a methoxy-substituted carbostyril derivative. One of the spiro substances is shown to participate in dienone–phenol rearrangement to provide the corresponding quinolone–phenol in high yield.
- Novel fluorescent (p-Phenylene ethynylene)-Calix[4]arene- based polymer: design, synthesis, and propertiesPublication . Costa, Alexandra I.; Ferreira, Luís F. V.; Prata, José V.A novel fluorescent (p-phenylene ethynylene)-calix[4]arene-based polymer (CALIX-PPE) has been successfully synthesized by cross-coupling polymerization of bis-calix[4]arene 1 with 1,4-diethynylbenzene. The polycondensation was carried out in toluene/NEt3 at 35 8C for 24 h, using PdCl2(PPh3)2/CuI as the catalytic system, furnishing CALIX-PPE in excellent isolated yields (higher than 95%, several runs). The yellow polymer is freely soluble in several nonprotic organic solvents. The GPC trace of the isolated polymer showed a monomodal distribution and a number-average molecular weight of 23,300 g mol-1 (Mw/Mn¼ 2.05). No evidence was found in the structural analysis (FTIR and 1H/13C NMR) regarding the formation of alkyne homocoupled segments along the polymer chain. For comparative purposes, the syn- thesis of an analogous poly(p-phenylene ethynylene) containing p-t-butyl-phenoxy- methyl side chains (TBP-PPE) was also undertaken. A great similarity was found between the photophysical properties of CALIX-PPE and TBP-PPE in solution (UV–vis and laser induced luminescence), clearly demonstrating their unique de- pendence on the structure and conformation of the conjugated PPE backbone. The fluorescence spectra of polymers are of nearly identical shape, displaying their maxi- mum emission around 420 nm. The calculated solution photoluminescence quantum yields of CALIX-PPE and TBP-PPE are of similar magnitude (Ø/F(CALIX-PPE) = 0.43; Ø/F(TBP-PPE) = 0.51).
- Calix[4]arene-carbazole-containing polymers synthesis, properties and thin films as molecular sensorsPublication . Costa, Alexandra; Barata, Patrícia; Fialho, Carina B.; Prata, José VirgílioCalix[4]arenes, an interesting bow-shaped macrocyles, have been explored due to their valuable properties, e.g. molecular recognition, proving outstanding complexability towards neutral and ionic guests of several origins. In this communication we report the synthesis and the chemosensing ability on the solid state of a new bicyclic calix[4]arene-based polymers integrating phenylene-ethynylene-carbazole units as fluorescente segments (Calix-OCP-PPE-CBZs), in the detection of several nitroanilines (NAs) in vapor phase.