A reusable catalytic system for efficient aerobic oxidation of alcohols with bi-functionalized PEG1000 ionic liquid [Imim-PEG1000-TEMPO][CuCl2−] was described.

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A simple and efficient protocol for the formylation of amines with ammonium formate with excellent yields catalyzed by Fe 3 O 4 nanoparticles in PEG-400 is described. Notably, this method shows excellent activity and chemoselectivity for the formylation of primary and secondary arylamines. Moreover, the nano-Fe 3 O 4 catalyst and PEG-400 could be easily recovered and reused.

In this paper, a green and facile protocol was described which was efficient for synthesis of benzimidazoles using nano‐Fe3O4 catalyst with continuous bubbling of air as the oxidant in PEG‐400/H2O aqueous system at room temperature. This protocol afforded the target products in good to excellent yields and the catalytic system could be recycled and reused without significant loss of catalytic activity. Copyright © 2014 John Wiley & Sons, Ltd.

General informationAll starting materials were purchased from commercial sources and used without further treatment. Analytical thin layer chromatography (TLC) was performed on precoated silica plates. Yields of the products refer to purification by silica-gel column chromatography. All starting chemicals are commercially available. Melting points were determined on a Perkin-Elmer differential scanning calorimeter. Elemental analysis were performed on Elementar Vario Micro spectrometer. 1 HNMR were recorded on a Bruker Advance III (500MHz) spectrometer with tetramethylsilane (TMS) as an internal standard. High performance liquid chromatography experiments were performed on a liquid chromatograph (Shimazhu LC-20AT). General procedure for preparation of catalyst:To a solution of PEG-4000 (0.06 mol) in toluene (150 mL), pyridine(0.12 mol) was added, followed by the addition of thionyl chloride (0.12 mol) within 30 min under N 2 atmosphere at 0 o C. The resulting slurry was stirred for 24 h at room temperature and filtered. The toluene was then removed by rotator evaporation under reduced pressure to give intermediate 1 as a gray viscous liquid. 4-hydroxy-TEMPO (0.05mol) was added to a suspension of Na (0.05 mol) in benzene (100 mL)and the resulting slurry was stirred for 8 h at room temperature. Intermediate 1 (0.025 mol) was then added and stirring for 24 h at room temperature. The suspension was then filtered and the filtrate concentrated under reduced pressure. This solution was then added to ether (100 mL) that was stirred vigorously and the precipitate collected by filtration, washed twice with ether (50 mL) and dried under vacuum. The product 2 was obtained as orange red viscous solid.In the next step, intermediate 2 (0.025 mol) was added to N-methylimidazole (0.025 mol) solution which was dissolved in toluene(100 mL) and the mixture was stirred at 80 °C for 20 h. The reaction was determined by HPLC and evaporated under reduced pressure to give intermediate 3 as an orange red oil. In the last step, the intermediate 3 (0.05 mol) and CuCl 2 (0.05 mmol)was mixed with t-BuONa(0.01 mol) in dry THF at room temperature under N 2 atmosphere for 12 h. The obtained viscous brown solid was washed with ether and dried in vacuum successively. General procedure for synthesis of benzimidazoles:To a 10 mL round-bottom flask O-phenylenediamine 1.08g (10 mmol), benzyl alcohol (10 mmol), TEMPO-PEG 4000 -NHC-Cu(II) complex (0.5 mmol), t-BuONa(0.5 mmol), H 2 O(1.0 ml) was successively added under a constant vigorous stiring. The reaction