Solvent-free, Efficient Transamidation of Carboxamides with Amines Catalyzed by Recyclable Sulfated Polyborate Catalyst

Abstract

Transamidation is a significant reaction in organic and medicinal chemistry. The amide is one of the most important functional groups used in organic transformations, and it is found in a wide variety of dyes, polymers, peptide dendrimers, agrochemicals, pharmaceuticals, and biologically active compounds. In 2007, the American Chemical Society Green Chemistry Institute Pharmaceutical Roundtable (ACS GCIPR) designated amidation as a challenging goal in organic chemistry for which green, efficient, and sustainable alternative methods are required. The amide link forms the backbone of proteins and peptides. It is an inherent part of many natural products such as capsaicin, piperine, Nacetyl anthranilic acid, taxol, and penicillin-G and drugs such as mepivacaine, lidocaine, articaine, amoxicillin, acetazolamide, valsartan, atorvastatin, protirelin, captopril, enalapril, chloramphenicol, methyprylon, benzipram, zolpidem, and many others. Fatty acid amides exhibit excellent antimicrobial, anti-inflammatory, antiproliferative, and antitubercular activities. Amides are useful intermediates for the synthesis of pharmacologically important heterocycles containing nitrogen and oxygen. It has been estimated that nearly 25% of active pharmaceutical ingredients contain amide functional groups. Transamidation involves the cleavage of the C-N bond in an amide reactant and the formation of a new C-N bond in the product. The exchange of the amine moiety of an amide is a conceptually simple but rare organic transformation, due to the modest reactivity of amides. Traditionally, amide synthesis involves the reaction of amines with carboxylic acid derivatives (chlorides, anhydrides, or esters), aldehydes, alcohols, or hydration of nitriles and hydroamination of alkynes. These procedures are often limited by harsh reagents, high temperature, tedious isolation, or the generation of waste. In this vein, a number of traditional name reactions, including the Schmidt, Ritter, Beckmann, and Ugi reactions have been reported for amide synthesis. Up to the present, the literature for transamidation includes the use of Bronsted acid ionic liquid, KOBu, polymer-bound HfCl4, 20 AlCl3, 21 Eu(OTf)3, 22 ZrCl4, 23 Ti(NMe2)4, 24 Sc(OTf)3, 25 CeO2, 26 binuclear Mn(II) complexes, Cp2ZrCl2, 28 Fe(III), Rh(II) NHC complexes, benzoic acid, boric acid, L-proline, hypervalent iodine, copper acetate, MnO2, 34 H2SO4-SiO2, 35 H-b Zeolite, Chitosan, B(OCH2CF3)3, 37