A Ligand-free CuCl Catalytic System for the N-Arylation of Benzotriazoles

Abstract

A general copper(I) chloride (CuCl) catalyst system was developed for the N-arylation of benzotriazoles using substituted aryl iodides under ligand-free conditions. Herein, 20 mol% CuCl was used to synthesise N-aryl benzotriazole derivatives in moderate to good yields. The practicality and low cost of this method make it well suited for both academic research and large-scale industrial applications.

Keywords

N-arylation - Copper(I) chloride - Benzotriazoles - Ligand-free - Aryl iodides

Publication History

Received: 12 November 2025

Accepted after revision: 28 January 2026

Article published online:
19 February 2026

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• 14 1-Phenyl-1H-benzo[d][1,2,3]triazole (Table 2, Entry 1); Typical Procedure: To a reaction vial were added CuCl (0.3 mmol, 0.2 equiv), Cs₂CO₃ (3.0 mmol, 2.0 equiv) and benzotriazole (1.5 mmol, 1.0 equiv), followed by 750 μL of dimethylformamide (DMF) and bromobenzene (3.0 mmol, 2.0 equiv). The vial was sealed with a screw cap and the mixture was stirred at room temperature for 5 min. The reaction mixture was then heated at 125 °C under air in a silicon oil bath for 18 h. After completion, the reaction was cooled to room temperature and diluted with dichloromethane (3 × 10 mL). The organic layer was dried over anhydrous Na₂SO₄, filtered, and concentrated under reduced pressure. The crude product was purified by column chromatography on silica gel to afford the desired compound. The structure and purity of the product were confirmed by ¹H and ¹³C NMR spectroscopy, as well as elemental analysis. Following the general procedure, the reaction provided 82% yield of the coupling product, after purification by silica gel-chromatography. ¹H NMR (400MHz CDCl₃): d = 8.15 (d, J = 8.4 Hz, 1H), d = 7.75–7.81 (m, 3H), d = 7.60–7.64 (m, 2H), d = 7.49–7.57 (m, 2H), d = 7.42–7.46 (m, 1H); ¹³C NMR (100 MHz, CDCl₃): 110.4, 120.4, 122.9, 124.4, 128.3, 128.7, 129.9, 137.0, 139.9, 146.5; Anal. calcd: C, 73.83; H, 4.65; N, 21.52; found: C, 74.02; H, 4.96; N, 21.43. 1-(3-fluorophenyl)-1H-benzo[d][1,2,3]triazole (Table 2, Entry 6): Following the general procedure, the reaction provided 74% yield of the coupling product, after purification by silica gel-chromatography. FTIR (neat): 1501.9, 1461.3, 1225.3, 1086.4, 741.9, 682.2 cm^{−1 1}H NMR (400 MHz CDCl₃): d = 8.16 (d, J = 8.4 Hz, 1H), d = 7.78 (d, J = 8.4 Hz, 1H), d = 7.57–7.64 (m, 4H), d = 7.44–7.48 (m, 1H), d = 7.19–7.24 (m, 1H); ¹³C NMR (100 MHz, CDCl₃): 110.2, 115.5, 115.7, 120.6, 124.7, 128.7, 131.2, 131.3, 132.1, 146.6, 161.9, 164.4.; Anal. calcd: C, 67.60; H, 3.78; N, 19.71; found: C, 67.82; H, 3.81; N, 19.63. 1-(3-methoxyphenyl)-1H-benzo[d][1,2,3]triazole (Table 2, Entry 9): Following the general procedure, the reaction provided 70% yield of the coupling product, after purification by silica gel-chromatography. FTIR (neat): 1497.1, 1471.1, 1322.1, 1235.7, 1092.0, 735.9, 687.8 cm^{−1 1}H NMR (400MHz CDCl₃): d = 8.15 (d, J = 8.4 Hz, 1H), d = 7.77 (d, J = 8.4 Hz, 1H), d = 7.49–7.57 (m, 2H), d = 7.42–7.46 (m, 1H), d = 7.35–7.38 (m, 2H), – = 7.03–7.06 (m, 1H), d = 3.91 (s, 3H); ¹³C NMR (100 MHz, CDCl₃): 55.7, 108.7, 110.5, 114.5, 114.8, 120.4, 124.4, 128.3, 130.6, 132.3, 138.1, 146.6, 160.7; Anal. calcd: C, 69.32; H, 4.92; N, 18.66; found: C, 69.16; H, 5.11; N, 18.63. 1-(4-chlorophenyl)-1H-benzo[d][1,2,3]triazole (Table 2, Entry 13): Following the general procedure, the reaction provided 70% yield of the coupling product, after purification by silica gel-chromatography. FTIR (neat): 1501.2, 1453.4, 1248.2, 1072.8, 740.1, 662.7 cm^{−1 1}H NMR (400MHz CDCl₃): d = 8.16 (d, J = 8.4 Hz, 1H), d = 7.71–7.77 (m, 3H), d = 7.56–7.62 (m, 3H), d = 7.44–7.48 (m, 1H); ¹³C NMR (100 MHz, CDCl₃): 110.1, 120.5, 124.0, 124.6, 128.6, 130.1, 132.2, 134.5, 135.6, 146.6; Anal. calcd: C, 62.76; H, 3.51; N, 18.39; found: C, 63.05; H, 3.65; N, 18.13. 1-(4-(trifluoromethyl)phenyl)-1H-benzo[d][1,2,3]triazole (Table 2, Entry 17): Following the general procedure, the reaction provided 71% yield of the coupling product, after purification by silica gel-chromatography. FTIR (neat): 1524.4, 1456.8, 1247.5, 1109.1, 748.7, 660.1 cm^{−1 1}H NMR (400MHz CDCl₃): d = 8.18 (d, J = 8.4 Hz, 1H), d = 7.89–8.00 (m, 4H), d = 7.79 (d, J = 8.5 Hz, 1H), d = 7.60–7.63 (m, 1H), d = 7.46–7.51 (m, 1H); ¹³C NMR (100 MHz, CDCl₃): 110.1, 120.7, 122.6, 124.8, 127.1, 127.2, 128.9, 130.7, 132.0, 139.9, 146.8; Anal. calcd: C, 59.32; H, 3.06; N, 15.96; found: C, 59.45; H, 2.98; N, 16.07.