Catalytic Activity of Manganese Oxide Anchored on to Alumina and Zirconia for the Synthesis of Dihydropyrimidinones: Role of Acidity, Crystal Phase and Morphology

Catalytic role of Cu(I) species in Cu2O/CuI supported on MWCNTs in the oxidative amidation of aryl aldehydes with 2-aminopyridines

“…It has been reported that NH3 desorption peaks in the range of 50-250 °C correspond to weakly acidic sites on the surface of the catalyst, while those in the range of 250-350 °C are indicative of moderately/strongly acidic sites. Furthermore, NH3 desorption peaks above 350 °C correspond to strongly acidic sites on the surface of the catalyst [33]. The NH3 desorption peak area can therefore be used to represent the concentration of the acidic sites on the surface of a catalyst.…”

Similarity and Competition between Biginelli and Hantzsch Reactions: an Opportunity for Modern Medicinal Chemistry

“…There are several examples in the literature which demonstrate that the increase of reaction temperatures to over 100°C is responsible for both the release of the water absorbed on the solid surface, thus activating the catalytic hydrolysis of urea, and the switch to the Hantzsch reaction (entries 3-5, Table 2). Moreover, the morphology of the solid catalyst, as well as its acidity, play a role in the competition, [98][99][100] in particular for a solid support with a higher surface area and lower acidity. Indeed, low acidity means low catalytic efficiency toward both MCRs.…”

“…[98,99] A high superficial area means high amounts of absorbed water, released in an uncontrollable manner at high temperatures. [99] Regarding the hydrophobic/hydrophilic surface balance, hydrophobic solid supports promote a faster absorption of hydrophobic reactants (i.e. aldehydes and 1,3-diketones), thus avoiding the penetration of the more hydrophilic ones (i.e.…”