Synlett 2017; 28(10): 1177-1182
DOI: 10.1055/s-0036-1588741
letter
© Georg Thieme Verlag Stuttgart · New York

Copper Oxide Nanoparticles as a Mild and Efficient Catalyst for N-Arylation of Imidazole and Aniline with Boronic Acids at Room Temperature

Raju Kumar Borah
a   Department of Chemical Sciences, Tezpur University, Napaam, 784028, Assam, India   Email: ashim@tezu.ernet.in
,
Prasanta Kumar Raul
b   Defence Research Laboratory, Post Bag no. 2, Solmara, Tezpur 784001, Assam, India
,
Abhijit Mahanta
a   Department of Chemical Sciences, Tezpur University, Napaam, 784028, Assam, India   Email: ashim@tezu.ernet.in
,
Andrey Shchukarev
c   Department of Chemistry, Umeå University, 90187 Umeå, Sweden
,
Jyri-Pekka Mikkola
c   Department of Chemistry, Umeå University, 90187 Umeå, Sweden
d   Industrial Chemistry & Reaction Engineering, ÅboAkademi University, 20500 Åbo-Turku, Finland
,
Ashim Jyoti Thakur*
a   Department of Chemical Sciences, Tezpur University, Napaam, 784028, Assam, India   Email: ashim@tezu.ernet.in
› Author Affiliations
Further Information

Publication History

Received: 02 February 2017

Accepted after revision: 14 February 2017

Publication Date:
09 March 2017 (online)


Abstract

The present work describes the excellent catalytic activity of copper(II) oxide nanoparticles (NPs) towards N-arylation of aniline and imidazole at room temperature. The copper(II)oxide NPs were synthesized by a thermal refluxing technique and characterized by FT-IR spectroscopy; powder XRD, SEM, EDX, TEM, TGA, XPS, BET surface area analysis, and particle size analysis. The size of the NPs was found to be around 12 nm having a surface area of 164.180 m2 g–1.The catalytic system was also found to be recyclable and could be reused in subsequent catalytic runs without a significant loss of activity.

Supporting Information

 
  • References and Notes

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  • 19 Typical Procedure: N-Arylation of Aniline with Phenylboronic Acid In a 50 mL round-bottomed flask, aniline (0.5 mmol), phenylboronic acid (1 mmol), K2CO3 (1.5 mmol), nanocatalyst (30 mol% with respect to aniline substrate) were added and stirred in MeOH–H2O (1:1) under air at r.t. for the required time, monitoring by TLC. After completion, the mixture was diluted with H2O, and the product was extracted with EtOAc (3×). The combined extracts were washed with brine (3×) and dried over Na2SO4. The product was purified by column chromatography (60–120 mesh silica gel, eluting with EtOAc–hexane solvent). The product was a grey crystalline solid, mp 54 °C; isolated yield: 92%. 1H NMR (400 MHz, CDCl3): δ = 5.63 (br s, 1 H), 6.90 (t, J = 8 Hz, 2 H), 7.04–7.02 (m, 4 H), 7.25–7.21 (m, 4 H) ppm. 13C NMR (100 MHz, CDCl3): δ = 143.2, 129.5, 121.1, 117.9 ppm.
  • 20 Typical Procedure: N-Arylation of Imidazole with Phenylboronic Acid In a 50 mL round-bottomed flask, imidazole (1 mmol), phenylboronic acid (1.2 mmol), K2CO3 (1.5 mmol), nanocatalyst (15 mol% with respect to imidazole substrate) were added and stirred in MeOH–H2O (1:1) under air at r.t. for the required time, monitoring by TLC. After completion, the mixture was diluted with H2O and the product was extracted with EtOAc (3×). The combined extracts were washed with brine (3×) and dried over Na2SO4. The product was purified using column chromatography (60–120 mesh silica gel, eluting with EtOAc–hexane). The product was isolated as white solid. 1H NMR (400 MHz, CDCl3): δ = 7.87 (s, 1 H), 7.50–7.47 (m, 2 H), 7.40–7.35 (m, 3 H), 2.28 (m, 1 H), 7.21 (s, 1 H) ppm. 13C NMR (100 MHz, CDCl3): δ = 137.4, 135.6, 130.3, 129.9, 127.6, 121.6, 118.3 ppm.
  • 22 Analytical Data for 4-Bromo-N-(4-fluorophenyl)benzenamine (Table 3, Entry 3) Colorless crystals; mp 43 °C. 1H NMR (400 MHz, CDCl3): δ = 5.54 (br s, 1 H), 7.32–7.25 (m, 2 H), 7.02–6.96 (m, 4 H), 6.82 (d, J = 8 Hz, 2 H) ppm. 13C NMR (100 MHz, CDCl3): δ = 143.3, 132.2, 121.3, 121.2, 118.1, 116.2, 116.0, 112.2 ppm.