Solid acid-catalyzed dehydration/Beckmann rearrangement of aldoximes: towards high atom efficiency green processes

Abstract

Rare earth metal ion exchanged (La 3+ , Ce 3+ , RE 3+) KFAU-Y zeolites were prepared by simple ion-exchange methods and have been characterized using different physico-chemical techniques. In this paper a novel application of solid acid catalysts in the dehydration/Beckmann rearrangement of aldoximes; benzaldoxime and 4-methoxybenzaldoxime is reported. Dehydration/Beckmann rearrangement reactions of benzaldoxime and 4-methoxybenzaldoxime is carried out in a continuous down flow reactor at 473 K. 4-Methoxybenzaldoxime gave both Beckmann rearrangement product (4-methoxyphenylformamide) and dehydration product (4-methoxybenzonitrile) in high overall yields. The difference in behavior of the aldoximes is explained in terms of electronic effects. The production of benzonitrile was near quantitative under heterogeneous reaction conditions. The optimal protocol allows nitriles to be synthesized in good yields through the dehydration of aldoximes. Time on stream studies show a fast decline in the activity of the catalyst due to neutralization of acid sites by the basic reactant and product molecules.

Acidity enhanced [Al]MCM-41 via ultrasonic irradiation for the Beckmann rearrangement of cyclohexanone oxime to ɛ-caprolactam

“…A major industrial strategy is to develop solid acids for the liquid-phase Beckmann rearrangement [4][5][6][7][8][9][10][11][12][13][14][15][16][17]. It can produce CPL at moderate temperature (373-403 K) with less catalyst deactivation [8,18], and the flexibility to replace homogeneous catalyst in existing plants, in comparison to that in the vapor-phase [19][20][21][22][23][24].…”

Why Is the Oxidation State of Iron Crucial for the Activity of Heme-Dependent Aldoxime Dehydratase? A QM/MM Study

“…In more general terms, Int1 is an example of a {FeL} 6 complex (where 6 is the total number of electrons in the Fe d orbitals and 6 complexes are close to linear in most cases, due to two back-donations from π xz * and π yz * of iron to the two π NO * orbitals of NO. 82 By contrast, the Fe−N1−C1 angle in Int1 is 151.6°(155.7°), 142.3°and 142.4°for the open-shell (closed-shell) singlet, the triplet, and the quintet, respectively.…”

Silica-Supported Dichlorophosphate Catalyzed Beckmann Rearrangement and Dehydration of Oximes Under Microwave Irradiation

“…The dehydration of aldoximes was also reported to conduct by using EtOPOCl 2 -DBU [16], ClSO 3 H [17], Ga(OTf) 3 [18], zeolite [19], ZnO/CH 3 COCl [20], KF/Al 2 O 3 [21], [RuCl 2 (pcymene)] 2 [22], and Cu(OAc) 2 [23] [25] have been reported, which could efficiently resolve the separation problem and therefore eliminate the pollution caused by the above catalysts.…”