An improved and greener protocol for the synthesis of benzimidazole derivatives, starting from o-phenylenediamine, with different aldehydes is reported. Double-condensation products were selectively obtained when Er(OTf)3 was used as the catalyst in the presence of electron-rich aldehydes. Conversely, the formation of mono-condensation products was the preferred path in absence of this catalyst. One of the major advantages of these reactions was the formation of a single product, avoiding extensive isolation and purification of products, which is frequently associated with these reactions.Theoretical calculations helped to understand the different reactivity established for these reactions. Thus, we found that the charge density on the oxygen of the carbonyl group has a significant impact on the reaction pathway. For instance, electron-rich aldehydes better coordinate to the catalyst, which favours the addition of the amine group to the carbonyl group, therefore facilitating the formation of double-condensation products.Reactions with aliphatic or aromatic aldehydes were possible, without using organic solvents and in a one-pot procedure with short reaction time (2–5 min), affording single products in excellent yields (75–99%). This convenient and eco-friendly methodology offers numerous benefits with respect to other protocols reported for similar compounds.

The aim of this study was to elucidate the structural and electronic factors that determine the antioxidant capacity of 5-Ocaffeoylquinic, caffeic and quinic acids under different experimental conditions. Antioxidant capacity was measured using different in vitro assays, involving diverse mechanisms of antioxidant action, namely, radical scavenging or reduction. The mechanisms of these reactions were analyzed by a theoretical study using the Density Functional Theory. Results allow relating in vitro antioxidant capacity of these three compounds with their chemical structures. The antioxidant capacity ex-perimentally observed for these three acids was interpreted considering the reaction mechanism involved, the nature and stability of the intermediate formed, the formation and reaction of secondary compounds, and the effect of the reaction medium. The main goal of this report is presenting a theoretical analysis of reactions implicated in the antioxidant capacity, identifying the causes that increase or decrease such property. Thus, we present a quantum mechanical description of the antioxidant properties involved with these three compounds, considering equilibria and secondary oxidations involved.

Synthesis of methanol from CO2via amines and formamides using NaBH4 as hydrogen source.

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