Acid–base M²⁺MgAlO and M²⁺AlO mixed oxides (where M²⁺ = Mg, Cu, Co, Zn, and Ni) were obtained by thermal decomposition of the corresponding layered double hydroxide (LDH) precursors and used as catalysts for cyclohexanol and benzaldehyde condensation under solvent-free conditions. The catalysts were characterized by X-ray diffraction (XRD), X-ray fluorescence (XRF), scanning electron microscopy (SEM), and temperature-programmed desorption of CO₂ (TPD-CO₂). Gas chromatography–mass spectroscopy (GC/MS) was used for the identification and quantification of the product mixtures. In the reaction of cyclohexanol and benzaldehyde on M²⁺MgAlO and MgAlO catalysts, a 2,6-dibenzylidene-cyclohexanone was obtained as the main product as a result of consecutive one-pot dehydrogenation of cyclohexanol to cyclohexanone and subsequent Claisen–Schmidt condensation. In the reaction mixture obtained in the presence of NiAlO, CoAlO, and ZnAlO catalysts, a cyclohexyl ester of 6-hydroxyhexanoic acid was detected together with the main product. This is most likely a by-product obtained after the oxidation, ring opening, and subsequent esterification of the cyclohexanol.

The Rzhanski granitoid pluton and Ignatitsa diorite porphyry bodies are considered Late Paleozoic in age, belonging to the Western Balkan Zone (WBZ) in Northwestern Bulgaria. Here, we provide U-Pb zircon geochronology of these magmatic bodies, together with their geochemistry complemented by the geochemistry of the overlying volcanic rocks. Geochemical data indicate that the intermediate to acid magmatic rocks are mostly peraluminous, calc-alkaline diorite/andesite to granite, that have an origin in a continental magmatic arc tectonic environment. All plutonic, subvolcanic and volcanic rocks exhibit uniform LILE- and LREE-enriched characteristics of an arc-related igneous suite. Zircons in the Ignatitsa diorite porphyry yield a magmatic crystallization age of 315 Ma, while the zircons in the Rzhanski aplitic metagranite pluton crystallize at 294 Ma. The record of the Variscan intrusive magmatism encompasses a region-wide, well-defined time interval 332–294 Ma in the WBZ, which coincides with those of the Central Balkan Zone and the adjacent Sredna Gora Zone. The age of the Variscan greenschist facies metamorphism using the metagranite and host greenschists relationships is limited between 294 Ma and the unpublished depositional age of 268 Ma for the overlying clastic formation in the studied part of the WBZ.