Direct Oxidative Amidation between N,N‐dimethylanilines and Anhydrides Using Metal‐Organic Framework [Cu₂(EDB)₂(BPY)] as an Efficient Heterogeneous Catalyst

Abstract

A crystalline porous metal‐organic framework [Cu2(EDB)2(BPY)] was synthesized and used as a heterogeneous catalyst for the direct oxidative amidation between N,N‐dimethylanilines and anhydrides to form tertiary amides as the principal products. The [Cu2(EDB)2(BPY)] exhibited similar activity as compared to that of [Cu2(BDC)2(BPY)], [Cu2(BDC)2(DABCO)], MOF‐143, and other common homogeneous salt catalysts. The optimal reaction conditions employed were [Cu2(EDB)2(BPY)] (10 % mol), TBHP (2 equiv), pyridine (1 equiv) in CH3CN at 80 °C over 2 h. The Cu2(EDB)2(BPY) could be separated from the reaction mixture by filtration, and could be recovered and reused several times without a significant degradation in catalytic activity and selectivity. Furthermore, generality of the optimal conditions was confirmed by employing various N,N‐dimethylaniline and anhydride derivatives.

Amide Bond Formation Catalyzed by Recyclable Copper Nanoparticles Supported on Zeolite Y under Mild Conditions

“…Thus, the reaction of 1 a and 2 a under the optimized conditions was not affected by the presence of TEMPO, giving 3 aa with the same rate and yield as in the absence of this additive (Scheme 2). It is worthy of note, that this experimental evidence is in contrast with the results by Phan and co-workers, [8] as they reported that no further reaction progress was detected for the same transformation catalyzed by the Cu-MOF [Cu 2 (EDB) 2 (BPY)], after addition of TEMPO.…”

“…In order to get some information about the plausible mechanistic pathway, and based on previous reports by other authors, [6,8] we next studied the effect of the addition of TEMPO to the reaction mixture as a radical scavenger. Thus, the reaction of 1 a and 2 a under the optimized conditions was not affected by the presence of TEMPO, giving 3 aa with the same rate and yield as in the absence of this additive (Scheme 2).…”

“…A further SET process from radical A (path v) would led to iminium cation C which is the key intermediate in the way to the desired amide product. [6,8,12] Alternatively, as depicted in Scheme 3, the formation of C through elimination from peroxide intermediate E, or even through a direct hydrogen atom transfer (HAT) from B, could not be disregarded. Nevertheless, it should be noted that this last HAT process (path iv) could be inhibited by the presence of a radical scavenger.…”

“…Full data for the new compounds 3 da, 3 ea and 3 ma are provided below. 8,144.7,129.8,127.8,127.2,37.3, 8,142.0,137.6,130.3,126.8,37.2,22.3, 5, 143.7, 133.1, 128.9, 121.5, 37.2, 22.5. N-(3-hydroxyphenyl 9,158.28,151.4,130.5,124.5,121.2,120.8,37.3,22.5 ppm.…”

“…In that paper, Phan and co-workers, reported on the use of copper-based metal-organic framework (MOF) composites for the direct oxidative amidation of N,N-dimethylanilines using anhydrides as acylating agents, in the presence of pyridine and TBHP as an oxidant. [8] The metal-organic framework [Cu 2 (EDB) 2 (BPY)] demonstrated to be an efficient heterogeneous catalyst and robust enough to be recycled and reused, but its synthesis is time-demanding and the scope of the method was tested with only four substrates ( Figure 1a).…”