Abstract
Abstract The volcanic ash from the Andes mountain range (Puyehue-Cordon Caulle volcanic complex situated in western South America on the Argentinean-Chilean border) was used as heterogeneous acid catalyst in the suitable synthesis of 3H-1,5-benzodiazepines. The natural ashes were classified according to their particle size to generate the different catalytic materials. The catalysts were characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS), vibrational spectroscopies (FT-IR and Raman), and textural properties were determined by N2 adsorption (SBET). Potentiometric titration with n-butylamine was used to determine the acidic properties of the catalytic materials. Several 3H-1,5-benzodiazepines were obtained by reaction of o-phenylenediamine and substituted 1,3-diphenyl-1,3-propanedione in solvent-free conditions, giving good to excellent yields of a variety benzodiazepines. The method was carried out in environmentally friendly conditions and it was operationally simple. The volcanic ash resulted in a safe and recyclable catalyst.
Highlights
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We report the treatment, characterization and application as catalysts of volcanic ashes obtained from the Puyehue-Cordon Caulle volcanic complex (Argentina-Chile), located at 2236 m above sea level, which is part of the southern Andes system
Volcanic ashes from the Puyehue-Cordon Caulle volcanic complex (PVA), collected from natural accumulations in S
Summary
Volcanic ashes from the Puyehue-Cordon Caulle volcanic complex (PVA), collected from natural accumulations in S. C. de Bariloche (Río Negro Province, Argentina), were washed with distilled water at room temperature for 72 h, dried and separated according to particle size by sieving. The particle sizes were selected using four mesh sizes: greater than #40 (0.420 mm), #40-60 (0.420-0.250 mm), #60-100 (0.250-0.149 mm) and lower than #100 (0.149 mm). The systems were named PVA N, where N stands for the mesh size (PVA 40, PVA 40-60, PVA 60-100, and PVA 100). Ashes without any treatment were called natural PVA. Commercial acid catalysts based on natural montmorillonite modified by hydrothermal treatment (K-10 and K-30 from Fluka, general formula (Al4(Si4O10)2(OH)4)) were evaluated for comparison
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