Oxidative Amidation of Aldehydes with Amines Catalysed by Fe(II) – Hydride Complex and N‐ Heterocyclic Carbenes (NHC)

Abstract

Oxidative amidation reaction of aldehydes with amines, by tert butyl hydrogen peroxide in toluene was achieved. The reaction utilised the in situ generated catalyst produced by Fe(II)hydride complex [FeH 2 (PPh 3) 4 ], and N-heterocyclic carbene (NHC) ligand. The catalytic system was found efficient for the synthesis of wide variety of mono and disubstiuted amides.

Copper and N-Heterocyclic Carbene-Catalyzed Oxidative Amidation of Aldehydes with Amines

“…25 Because of our interest in using cheaper metal along with NHCs for the synthesis of amides, we recently developed an amidation reaction catalyzed by an Fe complex and an NHC. 26 Here, we report our attempts to develop a onepot two-step oxidative pathway for amide synthesis from aldehydes and amines through hemiaminal formation by using TBHP with CuI and an NHC (Figure 1) as catalysts in the absence of any additives. Pleasingly, our initial coupling reaction of benzaldehyde (2a) (2.5 mmol) with morpholine (2a) (2.5 mmol), catalyzed by CuBr (10 mol%) and NHC precursor 1a (10 mol%), with NaH (10 mol%) as a base and TBHP (3 equiv) as the oxidant in acetonitrile (3 mL) under an inert atmosphere at 90 °C for 20 hours resulted in the formation of the amide product 4-benzoylmorpholine (4a) in 54% yield (Table 1, entry 1).…”

Synthesis and characterization of rare earth/lithium complexes stabilized by ethylenediamine-bridged bis(phenolate) ligands and their activity in catalyzing amidation reactions

“…In the last few decades, the transition metal-catalyzed direct amidation reaction has been highlighted as an attractive alternative using aldehydes and amines. 3 The reported examples include Ru, 4 Ni, 5 Cu, 6 Fe, 7 and Rh 8 based catalysts, which are in general efficient but mostly rely on complicated and/or harsh reaction conditions such as additional oxidants (e.g., I 2 , TBHP, NCS, and styrene), 6-7,8b strong bases (e.g., KO t Bu, NaH, CsOAc, and CaCO 3 ), 4,6c,7,8b high temperatures (e.g., 65-155 °C) 4-5,8b and long reaction times (e.g., 12-24 h). 4,8 Recent developments have witnessed tremendous advances in utilizing rare-earth metals for the amidation reaction.…”

“…In the last few decades, the transition metal-catalyzed direct amidation reaction has been highlighted as an attractive alternative using aldehydes and amines. 3 The reported examples include Ru, 4 Ni, 5 Cu, 6 Fe, 7 and Rh 8 based catalysts, which are in general efficient but mostly rely on complicated and/or harsh reaction conditions such as additional oxidants ( e.g. , I 2 , TBHP, NCS, and styrene), 6–7,8 b strong bases ( e.g.…”

“…Symmetry operator: 1 1 − X, 1 − Y, −Z. Selected bond distances (Å) and bond angles (°): Nd1-O1 2.271(2), Nd1-O2 2.272(2), Nd1-N3 2.329(2), Nd-N4 2.324 (2), Li1-O1 1.886(5), Li1-O2 1.897(5), Li1-N1 2.113(5), Li1-N2 2.118(5); O1-Nd1-O2 77.03(6), O1-Nd1-N3 119.78(7), O1-Nd1-N4 112.33(7), O2-Nd1-N3 114.71(7), and O2-Nd1-N4 116.86(7).…”

Substituted, Bicyclic 3‐Benzoyl Flavanones Synthesis by Highly Efficient N‐Heterocyclic Carbene (NHC) Catalysis

“…Utilizing the above approach and as a part of our ongoing research on the exploration of NHCs as organocatalysts, [21] we hereby report the novel synthesis of various substituted, 3benzoyl flavanones utilizing NHC bis-(1,3-dimesityl) imidazolium chloride as organocatalyst, I 2 co-catalyst, and tert butyl hydroperoxide as an oxidant for the [4 + 2] annulations of substituted salicylaldehyde and chalcones to flavanones in solvent ethanol. The chalcone dipolarophilesare versatile synthones for the formation of many complex heterocycles and spiro-heterocycles as well owing to the presence of varying dipolarophile functions such as C=C and C=O.…”