A facile, efficient and environment-friendly protocol for the synthesis of 6-chloro-5-formyl-1,4-dihydropyridine derivatives has been developed by the convenient ultrasound-mediated reaction of 2(1H)pyridone derivatives with the Vilsmeier-Haack reagent. This method provides several advantages over current reaction methodologies including a simpler work-up procedure, shorter reaction times and higher yields.

Several conditions for hydroxyapatite ceramic preparation were used: sintering at 1150 °C in air or under H2O vapor flow, quenched in water at room temperature after sintering, or slow cooling inside the furnace. Depending on specific combinations of these preparation conditions, in the resulting ceramics significant differences are observed in the phase composition and dielectric properties, ranging from capacitive to a semiconducting response. Comparison between the experimental x-ray diffraction patterns and those calculated by the Rietveld method show that during sintering in air, approximately 40% of hydroxyapatite is transformed to tricalcium phosphate. The XRD analysis shows that this transformation could be possible using the following process: Ca10(PO4)6(OH)2 = 2Ca3(PO4)2 + Ca2P2O7 + 2CaO + H2O.

No abstract