Catalytic synthesis of amides via aldoximes rearrangement

Abstract

Amide bond formation reactions are among the most important transformations in organic chemistry because of the widespread occurrence of amides in pharmaceuticals, natural products and biologically active compounds. The Beckmann rearrangement is a well-known method to generate secondary amides from ketoximes. However, under the acidic conditions commonly employed, aldoximes RHC=NOH rarely rearrange into the corresponding primary amides RC(=O)NH2. In recent years, it was demonstrated that this atom-economical transformation can be carried out efficiently and selectively with the help of metal catalysts. Several homogeneous and heterogenous systems have been described. In addition, protocols offering the option to generate the aldoximes in situ from the corresponding aldehydes and hydroxylamine, or even from alcohols, have also been developed, as well as a series of tandem processes allowing the access to N-substituted amide products. In this Feature article a comprehensive overview of the advances achieved in this particular research area is presented.

How Strong is Hydrogen Bonding to Amide Nitrogen?

“…Despite the information abundance on the amide functionality, [1][2][3] there is a continued interest in chemical synthesis, [4][5][6][7][8][9] biosynthesis [10][11][12] and reactivity [13][14][15][16][17][18][19] of amides due to their importance in medicine, biology, chemistry and other related interdisciplinary sciences. [20][21][22][23][24][25][26][27][28][29][30][31][32] This relevance encourages the research of the amide group's fundamental characteristics, e. g. the cis-trans isomerization barrier, [33][34][35][36] the resonance energy [37][38][39] or acid-base properties.…”

A Facile One‐Pot Transformation of Aromatic Aldehydes/Ketones to Amides: Fe2O3@SiO2 as an Environmentally Benign Core‐Shell Catalyst

“…In spite of the multitude of ways in which Beckmann rearrangement has been carried out, there is not much literature for the one pot conversion of aldehydes and ketones directly to amides via the oxime in liquid‐phase using solid acid catalyst (Scheme ). A few catalyst systems have been developed to both generate the oxime in situ and then carry out its Beckmann rearrangement to the corresponding amide . Catalysts comprising of organics like formic acid, oxalic acid, methanesulfonic acid, methanesulfonyl chloride; simple metal salts like AlCl 3 , FeCl 3 , NiCl 2 , ZnCl 2 , CuSO 4 , Cu(OAc) 2 ; and metal complexes containing heavy metals like Ru, Ir, In and Pd have been reported.…”

Exfoliation effect of PEG-type surfactant on Pd supported GO (SE-Pd(nanoparticle)/GO) in cascade synthesis of amides: A comparison with Pd(nanoparticle)/rGO

“…Synthesis of amides by traditional procedures through the reaction of carboxylic acids (or their activated derivatives such as chlorides, anhydrides or esters) and amine, could be inconvenient and unselective in a total synthesis or a densely functionalized compounds. Hence, many other methods are developed [2][3][4]. Among them and based on "green chemistry" desire, cascade-type and tandem amidation processes are the considerable part of recent developments.…”