MCF-supported boronic acids as efficient catalysts for direct amide condensation of carboxylic acids and amines

Abstract

For efficient direct amide condensations, a new class of catalysts are developed by immobilizing boronic acids on mesocellular siliceous foam. Associated with their large pores, the microenvironments surrounding the immobilized active species greatly influence the catalytic activity. The fluoroalkyl moieties on the silica surface significantly enhance the catalytic performance along with easy recovery and reuse. This approach proposes a potential way to optimize various types of silica-supported catalysts.

Boronic Acid-Catalyzed Reactions of Carboxylic Acids

“…In 2014, Gu and Lee et al reported mesocellular siliceous foam-supported boronic acids as efficient catalysts for direct amide condensation of carboxylic acids and amines (Scheme 9) [34]. Associated with their large pores, the microenvironments surrounding the immobilized active species greatly influence the catalytic activity.…”

Design of Boronic Acid–Base Complexes as Reusable Homogeneous Catalysts in Dehydrative Condensations between Carboxylic Acids and Amines

“…Boronic acid catalysts for the amidation between carboxylic acids and amines have enjoyed great success over the past two decades since the first report in 1996 by Yamamoto and colleagues . After that report, considerable efforts have been devoted to the development of reusable boronic acid catalysis (Figure ) . The most prevalent strategy involves the development of solid‐phase amidation boron catalysts, which are both reusable and easily removed from the solution.…”

“…Therefore, Yamamoto and colleagues developed a new generation of polystyrene‐bound 4‐pyridiumboronic acids in 2005 that are quite stable and can be reused ten times without a loss of catalytic activity . Recently, Lee and colleagues reported mesocellular siliceous foam (MCF)‐supported boronic acid catalysts for a direct amide condensation . They found that MCF‐supported boronic acids optimized with capped fluoroalkyl groups had greater catalytic activity than their homogeneous counterparts.…”

Graphene Oxide as a Metal‐free Carbocatalyst for Direct Amide Synthesis from Carboxylic Acid and Amine Under Solvent‐Free Reaction Condition

“…Several methodologies have been developed for direct amidation of carboxylic acids using biocatalysts, homogeneous catalyst, Lewis acid catalyst, boron reagents, [14] or metal-based catalytic systems such as Ti(OiPr), [15] Cp 2 ZrCl 2 , [16] and ZrCl 4 [14] and heterogeneous catalytic systems, including immobilized enzymes, [17] solid-supported boronic acids, [18] alumina-ball, [19] and silica gel. [20] Though, considerable drawbacks remain due to the complex synthesis of catalysts, generation of unavoidable by-products, and limited substrate scope.…”