Ultrasounds in Melted Poly(ethylene glycol) Promote Copper‐Catalyzed Cyanation of Aryl Halides with K₄[Fe(CN)₆]

Abstract

Melted poly(ethylene glycols) (PEGs) were used for the first time as solvent for the sonochemically promoted cyanation of aryl halides employing inexpensive and safe K4[Fe(CN)6] and a relatively low amount of Cu-based catalyst. The Mw (weight-average polymer molecular weight) of PEG proved to notably influence the substrate conversion, which is indicative of a strong dependence of the sonication efficacy on solvent properties. Gel permeation chromatography (GPC), X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM) contributed to the characterization of the polymer and the elucidation of the catalytic system.

Copper-Mediated C–X Functionalization of Aryl Halides

“…Colacino and co-workers used ultrasounds in melted PEG to promote the copper-catalyzed cyanation of aryl iodides/bromides with K 4 [Fe(CN) 6 ]. 114 An analogous reaction conducted with palladium catalyst also proceeded smoothly; however, the reaction failed when conducted in the presence of microwave instead of ultrasound. The crown ether like chelation of potassium cations by PEG accounted the improved reactivity of the "naked" [Fe(CN) 6 ] 4− counterion under ultrasound activation.…”

“…Colacino and co-workers used ultrasounds in melted PEG to promote the copper-catalyzed cyanation of aryl iodides/bromides with K 4 [Fe­(CN) 6 ] . An analogous reaction conducted with palladium catalyst also proceeded smoothly; however, the reaction failed when conducted in the presence of microwave instead of ultrasound.…”

Poly(ethylene) glycols and mechanochemistry for the preparation of bioactive 3,5-disubstituted hydantoins

“…The N-alkylation (Method C) was improved when poly(ethylene) glycol (HO-PEG-400-OH) was used as the reaction solvent (entry 1, Table 3): ethotoin 12 was obtained in a 40% yield, a similar result to the previous methods A and B. Poly(ethylene) glycols are green solvents 38 with low toxicity, nding applications in the biomedical eld 39 and catalysis. 40 Very recently, their peculiar role was highlighted in metal- catalyzed processes in a ball-mill 32 or by ultrasounds, 41 having in common similar activation effects, 42 or in Polymer-Assisted Grinding (POLAG) processes for co-crystal formation. 31 Considering the preliminary result indicating that PEG polymer seemed to improve the efficiency of N-alkylation, the conditions were transposed to a ball-milled reaction (Table 3).…”

Copper Mediated Chemo‐ and Stereoselective Cyanation Reactions

“…PEG M w (weight‐average polymer molecular weight) effectively prompted the subsisted conversion (See Figure 17). [28] …”