Hydrolysis of amides to carboxylic acids catalyzed by Nb₂O₅

Abstract

An efficient heterogeneous Nb2O5 catalytic system has been developed for industrially important and challenging amide hydrolysis reaction to carboxylic acid through cleavage of resonance stabilized amidic C–N bond.

Hydrolysis of Acetamide on Low-Index CeO2 Surfaces: Ceria as a Deamidation and General De-esterification Catalyst

“…The first three oxides were reported to achieve conversion of acetamide to acetic acid over 45%, including 100% conversion over Nb 2 O 5 . The authors proposed mechanisms for the hydrolysis and alcoholysis of amides based on the concerted actions of Lewis-acidic metal cation and basic O anion that attack the carbonyl O and carbonyl C, respectively, and supported them with density functional theory (DFT) calculations on CeO 2 (111). , They also identified a correlation between the increasing basicity of lattice oxygen in metal oxides, as represented by the O 1s binding energy, and higher initial reaction rates for several oxides. It remains unclear why CeO 2 is more effective than Nb 2 O 5 in alcoholysis but not in hydrolysis …”

“…This has led to investigation into solid ceria (CeO 2 ) as a possible deamidation catalyst. Over the past decade, Shimizu and co-workers demonstrated efficient alcoholysis and subsequent esterification of amides over high loadings of CeO 2 in batch mode in hot, boiling alcohols. − Recently, the same group investigated the hydrolysis of acetamide under similar conditions of boiling solvents and high catalyst loadings using various solid oxides including Nb 2 O 5 , ZrO 2 , CeO 2 , TiO 2 , SiO 2 , and Al 2 O 3 , among others as catalysts . The first three oxides were reported to achieve conversion of acetamide to acetic acid over 45%, including 100% conversion over Nb 2 O 5 .…”

“…Ceria-catalyzed hydrolysis and alcoholysis reported thus far in the literature have been based on commercially available polycrystalline ceria powder. − It is not clear which low-index facet or what surface structure, if any, plays a dominant role in the observed deamidation activity. Surface structure sensitivity has been observed for many reactions on ceria. − Mullins and co-workers showed that small organic molecules, including water, alcohols, acetic acid, and acetaldehyde, exhibit qualitatively different temperature-programmed desorption (TPD) results on CeO 2 (111) vs CeO 2 (100) thin films .…”

Synthesis of adiponitrile from dimethyl adipate and ammonia in the vapor-phase over niobium oxide

“…On the other hand, the fraction of strong acid sites in all Nb 2 O 5 -T samples, except for Nb 2 O 5 -400, increases Previous studies have demonstrated that niobium oxide exhibits excellent catalytic properties even in the presence of water and/or organic amines. 42,43 Water-blocked niobium oxide could still function as an effective L acid. 44 Besides, kinetic studies suggested that L-acidic Nb 5+ sites interact preferentially with carboxylic acid derivatives in the presence of excess basic molecules, such as water and organic amines.…”

Ammonium Niobium Oxalate (ANO)

“…In a preliminary screening, ANO was applied in the hydrolysis of acetamide under reflux in moderate yield (45%) after 20 h. However, the best results of the study were obtained using the heterogeneous catalyst niobium oxide. 9 (F) Enantiomerically enriched alcohols have an important role in the synthesis of different chiral biologically active compounds present in pharmaceuticals and food products. Enzymatic kinetic resolution (KR) is the most used method to obtain chiral secondary alcohols using lipases as biocatalysts.…”