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. 2021 Mar 5;6(10):6766-6779.
doi: 10.1021/acsomega.0c05840. eCollection 2021 Mar 16.

Highly Active Cellulose-Supported Poly(hydroxamic acid)-Cu(II) Complex for Ullmann Etherification

Choong Jian Fui  1 , Tang Xin Ting  1 , Mohd Sani Sarjadi  1 , Zarina Amin  2 , Shaheen M Sarkar  3 , Baba Musta  1 , MdLutfor Rahman  1
Affiliations

Highly Active Cellulose-Supported Poly(hydroxamic acid)-Cu(II) Complex for Ullmann Etherification

Choong Jian Fui et al. ACS Omega. .

Abstract

Highly active natural pandanus-extracted cellulose-supported poly(hydroxamic acid)-Cu(II) complex 4 was synthesized. The surface of pandanus cellulose was modified through graft copolymerization using purified methyl acrylate as a monomer. Then, copolymer methyl acrylate was converted into a bidentate chelating ligand poly(hydroxamic acid) via a Loosen rearrangement in the presence of an aqueous solution of hydroxylamine. Finally, copper species were incorporated into poly(hydroxamic acid) via the adsorption process. Cu(II) complex 4 was fully characterized by Fourier transform infrared (FTIR), field emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray (EDX), transmission electron microscopy (TEM), inductively coupled plasma optical emission spectrometry (ICP-OES), thermogravimetric analysis (TGA), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) analyses. The cellulose-supported Cu(II) complex 4 was successfully applied (0.005 mol %) to the Ullmann etherification of aryl, benzyl halides, and phenacyl bromide with a number of aromatic phenols to provide the corresponding ethers with excellent yield [benzyl halide (70-99%); aryl halide (20-90%)]. Cu(II) complex 4 showed high stability and was easily recovered from the reaction mixture. It could be reused up to seven times without loss of its original catalytic activity. Therefore, Cu(II) complex 4 can be commercially utilized for the preparation of various ethers, and this synthetic technique could be a part in the synthesis of natural products and medicinal compounds.

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Conflict of interest statement

The authors declare no competing financial interest.

Figures

Scheme 1
Scheme 1. Preparation of Cu(II) Complex 4
Figure 1
Figure 1
FTIR spectra of (a) cellulose 1, (b) poly(methyl acrylate) 2, (c) poly(hydroxamic acid) 3, (d) Cu(II) complex 4, and (e) Cu(II) complex 4 after the seventh cycle of reaction.
Figure 2
Figure 2
SEM of (a) cellulose 1, (b) poly(methyl acrylate) 2, (c) poly(hydroxamic acid) 3, (d) Cu(II) complex 4, and (e) Cu(II) complex 4 after the seventh cycle reaction.
Figure 3
Figure 3
TEM image of (a) fresh Cu(II) complex 4 and (b) Cu(II) complex 4 after the seventh cycle reaction (c) measurement.
Figure 4
Figure 4
EDX image of Cu(II) complex 4.
Figure 5
Figure 5
TG graphs of (a) Cu(II) complex 4, (b) poly(hydroxamic acid) 3, (c) cellulose 1, and (d) poly(methyl acrylate) 2.
Figure 6
Figure 6
XRD spectra of the comparison of (a) untreated pandanus fruit fiber and cellulose 1, (b) poly(methyl acrylate) 2 and poly(hydroxamic acid) 3, and (c) before and after anchoring copper onto poly(hydroxamic acid) 3.
Figure 7
Figure 7
Survey scan of XPS for (a) poly(hydroxamic acid) 3 and (b) Cu(II) complex 4.
Figure 8
Figure 8
Narrow scan of XPS for Cu(II) complex 4 at the copper-binding site.
Figure 9
Figure 9
O 1s core-level XPS spectra of (a) poly(hydroxamic acid) 3 and (b) Cu(II) complex 4 and N 1s core-level spectra of (c) poly(hydroxamic acid) 3 and (d) Cu(II) complex 4.
Scheme 2
Scheme 2. Plausible Mechanism for the Catalytic Synthesis of Ether over Cu(II) Complex 4
Figure 10
Figure 10
Reusability of Cu(II) complex 4 in O-arylation of phenol with 4-nitrobenzyl bromide.
Figure 11
Figure 11
Hot filtration test of the Ullmann reaction (a) in the presence of Cu(II) complex 4 in the whole reaction and (b) on removing Cu(II) complex 4 after 30 min.
Figure 12
Figure 12
(a) Poly(hydroxamic acid) 3 before copper anchoring and (b) poly(hydroxamic acid) 3 after complexation with copper (Cu(II) complex 4).
See this image and copyright information in PMC

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