A Simple Method for Synthesis of Methylene Dioximes Using Poly(ethylene glycol)‐400 as a Phase Transfer Catalyst

Abstract

A simple method for synthesis of methylene dioximes by reaction of ketoximes with dichloromethane in the presence of aqueous sodium hydroxide solution using poly (ethylene glycol)-400 (PEG-400) as a phase transfer catalyst is described.

A green protocol for synthesis of methylene dioximes promoted by an ionic liquid [bmim]BF4

“…As shown in 1, Entry 3), which provided the product 3a in 96% yield in 30 min. Whereas in other reported methods, [12][13][14][15][16][17][18] to obtain the same yield needed 3.5 h. It was clear that synthesis of methylene dioximes using the ionic liquid as a catalyst was a quick and effective method. So [bmim]BF 4 was chosen for further study in this work.…”

“…11 The main synthetic route involves the use of phase transfer catalysts (PTCs) in the heterogenous reaction between oximes and dichloromethane. The synthesis of methylene dioximes involves alkylation of oximes with dichloromethane using either: (1) quaternary ammonium salt with 50% aqueous solutions of sodium hydroxide for 16 h, 12 (2) sodium hydroxide in combination with tetrabutylammonium bromide for 20 h, 13 (3) potassium superoxide in the presence of di-μchlorobis (2-methylallyl) dipalladium (II) catalyst for 72 h, 14,15 (4) potassium carbonate in combination with 18-crown-6 for 12 h under argon at 50 °C, 15 (5) sodium hydroxide in the presence of a low-molecular weight polyethylene glycol-400 (PEG-400) for 14-20 h, 16 (6) potassium hydroxide in combination with 18-crown-6 in acetonitrile at 70 °C, 17 (7) and sodium hydroxide in the presence of benzyldimethyltetradecylammonium chloride for 2-3.5 h. 18 However, some of these methods have not been entirely satisfactory, with disadvantages such as relatively long reaction times, low yield, high reaction temperature and using a catalyst that cannot be recycled. Therefore, the development of a simple, efficient, and environmentally benign method for the synthesis of methylene dioximes remains desirable.…”

“…For most of substrates, the reaction was completed at 20-30 min with high yields. whereas in reported methods, [12][13][14][15][16][17][18] the reaction was completed to need not less than 2 h with similar or lower yields. For example, compound 3e was previously prepared in 90% yield within 3.5 h under ultrasonication, 18 whereas in the presence of [bmim]BF 4 , 3e was obtained in 93% yield in 30 min.…”

"Polyethylene Glycol-400 Used as Phase Transfer Catalyst for One-Pot Synthesis of 2-Amino-3- Cyanopyridine Derivatives Under Aqueous Conditions"

“…[15][16][17][18][19] PEG-400 emerged as a powerful phase transfer catalyst and also a reaction medium for many organic transformations under mild reaction conditions. Moreover, PEG-400 is inexpensive, easy to handle, thermally stable, non-toxic and recyclable in various organic transformations, such as synthesis of thiadiazoles, 20 quinazolines, 21 α-amino acids 22 and many transformations.…”