LiClO₄/EG as an Environmentally Benign Lewis Acidic Catalytic System for the Expeditious Synthesis of 2,3-Dihydroquinazolin-4 (1H)-ones and NH-1,2,3-Triazoles

Abstract

An environmentally benign protocol has been developed for the synthesis of two biologically important N-heterocycles; namely, 2,3-dihydroquinazolin-4(1H)-ones and NH-1,2,3-triazoles. These two N-heterocyclic systems are synthesized using readily available and inexpensive LiClO₄ in ethylene glycol (EG) and PEG-400 with good to excellent product yield. The method provides an important benchmark for the rapid, operationally simple synthesis of these two heterocycles. Sc-XRD analysis of one of the products gives structural information and DFT calculations provide important information on the mechanistic pathway.

Key words

quinazolinone - triazole - DFT - gram-scale reactions - synthesis

Publication History

Received: 14 December 2024

Accepted after revision: 04 February 2025

Accepted Manuscript online:
04 February 2025

Article published online:
25 March 2025

• References and Notes

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• 39 Garg A, Borah N, Sultana J, Kulshrestha A, Kumar A, Sarma D. Appl. Organomet. Chem. 2021; 35: e6298 Synthesis of 2,3-Dihydroquinazolin-4(1H)-one Derivatives; General Procedure A mixture of anthranilamide (1 mmol), aldehyde or ketone derivative (1.2 mmol), LiClO₄ (0.5 mmol), and ethylene glycol (3 mL) was taken in a round-bottom flask and stirred at 80 °C for the time indicated in Table 2 and Table 3. The progress of the reaction was monitored by TLC. Upon completion of the reaction, the mixture was extracted with EtOAc (3 × 20 mL), washed with distilled water and brine solution, dried over anhydrous sodium sulfate, and concentrated under reduced pressure. The resulting residue was purified by silica gel column chromatography (10–15% EtOAc/hexane) to give the desired product. Synthesis of NH-1,2,3-Triazole Derivatives; General Procedure A mixture of benzaldehyde derivative (1 mmol), nitro-methane (2.5 mmol), sodium azide (2.5 mmol), LiClO₄ (0.5 mmol), and PEG-400 (3 mL) was taken in a round-bottom flask and then stirred at 110 °C for the time indicated in Table 4_. The progress of the reaction was monitored by TLC. Upon completion of the reaction, the mixture was extracted with EtOAc (3 × 20 mL), washed with distilled water and brine solution, dried over anhydrous sodium sulfate, and concentrated under reduced pressure. The resulting residue was purified by silica gel column chromatography (5–15% EtOAc/hexane) to give the desired product. Compounds 3ae, 3af, 3ag, 3ah, 3aj, 3ak, 3am, 3ap, 4ab, 4ac, 4ae, 4af ³⁹ and 5a, 5b, 5d, 5h, 5k ⁴⁰ are previously reported. 2-(4-Bromophenyl)-2,3-dihydroquinazolin-4(1H)-one (3aa) Yield: 92% (209 mg); mp 200–204 °C^. ESI-MS: m/z = 302.96 [M]⁺. ¹H NMR (500 MHz, DMSO-d ₆): δ = 8.36 (s, 1 H), 7.64–7.47 (m, 3 H), 7.45 (d, J = 8.4 Hz, 2 H), 7.28–7.17 (m, 1 H), 7.17 (s, 1 H), 6.77 (d, J = 8.0 Hz, 1 H), 6.71–6.68 (m, 1 H), 5.78 (s, 1 H). ¹³C NMR (125 MHz, DMSO-d ₆): δ = 164.08, 148.20, 141.66, 133.99, 131.82, 129.66, 127.95, 122.16, 117.88, 115.51, 114.04, 66.38. 2-(4-Methoxyphenyl)-2,3-dihydroquinazolin-4(1H)-one (3ab) Yield: 62% (113 mg); mp 175–177 °C^. ESI-MS: m/z = 255.17 [M + 1]⁺. ¹H NMR (500 MHz, DMSO-d ₆): δ = 8.21 (s, 1 H), 7.64 (d, 1 H), 7.45 (d, 2 H), 7.27 (t, 1 H), 7.04 (s, 1 H), 6.98 (d, 2 H), 6.77 (d, 1 H), 6.70 (t, 1 H), 5.73 (s, 1 H), 3.78 (s, 3 H). ¹³C NMR (125 MHz, DMSO-d ₆): δ = 164.23, 159.96, 148.66, 134.01, 133.78, 128.74, 127.88, 117.62, 114.94, 114.1, 66.81. 55.72. 2-(4-Fluorophenyl)-2,3-dihydroquinazolin-4(1H)-one (3ac) Yield: 88% (213 mg); mp 277–280 °C. ¹H NMR (500 MHz, DMSO-d ₆): δ = 8.29 (s, 1 H), 7.63 (dd, J = 7.7, 1.3 Hz, 1 H), 7.61–7.53 (m, 1 H), 7.24–7.21 (m, 4 H), 7.10 (s, 1 H), 6.75 (d, J = 8.0 Hz, 1 H), 6.70–6.67 (m, 1 H), 5.78 (s, 1 H). ¹³C NMR (125 MHz, DMSO-d ₆): δ = 164.08, 148.31, 138.31, 138.29, 133.87, 129.58, 129.52, 127.88, 117.77, 115.68, 115.51, 115.46, 114.96, 66.45. 2-(4-Chlorophenyl)-2,3-dihydroquinazolin-4(1H)-one (3ad) Yield: 92% (249 mg); mp 197–200 °C. ¹H NMR (500 MHz, DMSO-d ₆): δ = 8.35 (s, 1 H), 7.65–7.45 (m, 2 H), 7.28–7.18 (m, 4 H), 7.18 (s, 1 H), 6.79–6.65 (dd, J = 15.5, 7.7 Hz, 2 H), 5.85 (s, 1 H). ¹³C NMR (125 MHz, DMSO-d ₆): δ = 163.9, 147.3, 140.1, 133.9, 133.3, 129.1, 128.7, 127.7, 117.7, 115.2, 114.8, 66.2. 2-(3-Bromophenyl)-2,3-dihydroquinazolin-4(1H)-one (3ai) Yield: 90% (273 mg); mp 221–225 °C. ESI-MS: m/z = 302.95 [M]⁺. ¹H NMR (500 MHz, DMSO-d ₆): δ = 8.39 (s, 1 H), 7.67 (s, 1 H), 7.62 (dd, J = 7.7, 1.2 Hz, 1 H), 7.60–7.48 (m, 2 H), 7.37 (t, J = 7.8 Hz, 1 H), 7.26–7.21 (m, 2 H), 6.77 (d, J = 8.1 Hz, 1 H), 6.75–6.66 (m, 1 H), 5.78 (s, 1 H). ¹³C NMR (125 MHz, DMSO-d ₆): δ = 162.88, 146.96, 144.10, 132.95, 130.64, 130.07, 129.12, 126.84, 125.26, 121.06, 116.80, 114.36, 113.94, 64.98. 2-(3-Hydroxyphenyl)-2,3-dihydroquinazolin-4(1H)-one (3al) Yield: 85% (205 mg); mp 217–219 °C. ESI-MS: m/z = 240.99 [M + 1]⁺. ¹H NMR (500 MHz, DMSO-d ₆): δ = 9.49 (s, 1 H), 8.23 (s, 1 H), 7.58 (d, J = 7.5 Hz, 1 H), 7.18 (dt, J = 15.5, 7.5 Hz, 2 H), 7.06 (s, 1 H), 6.87 (d, J = 8.2 Hz, 2 H), 6.71 (d, J = 7.9 Hz, 2 H), 6.64 (t, J = 7.4 Hz, 1 H), 5.63 (s, 1 H). ¹³C NMR (125 MHz, DMSO-d ₆): δ = 163.94, 157.76, 148.24, 143.63, 133.71, 129.75, 127.75, 117.86, 117.40, 115.75, 115.27, 114.75, 114.06, 66.86. 2-(2,4-Dichlorophenyl)-2,3-dihydroquinazolin-4(1H)-one (3an) Yield: 94% (318 mg); mp 271–275 °C. ESI-MS: m/z = 292.96 [M + 1]⁺. ¹H NMR (500 MHz, DMSO-d ₆): δ = 8.26 (s, 1 H), 7.70 (dd, J = 8.2, 3.4 Hz, 2 H), 7.64 (s, 1 H), 7.49 (d, J = 8.5 Hz, 1 H), 7.28 (t, J = 7.7 Hz, 1 H), 7.04 (s, 1 H), 6.80 (d, J = 8.2 Hz, 1 H), 6.74 (t, J = 7.5 Hz, 1 H), 6.16 (s, 1 H). ¹³C NMR (125 MHz, DMSO-d ₆): δ = 164.08, 148.02, 137.45, 134.46, 133.96, 133.42, 130.63, 129.43, 128.11, 127.92, 118.10, 115.17, 115.12, 63.87. 2-(4-(Dimethylamino)phenyl)-2,3-dihydroquinazolin-4(1H)-one (3ao) Yield: 38% (102 mg); mp 230 °C. ESI-MS: m/z = 268.09 [M + 1]⁺. ¹H NMR (500 MHz, DMSO-d ₆): δ = 8.13 (s, 1 H), 7.63 (d, J = 7.7 Hz, 1 H), 7.33 (d, J = 8.3 Hz, 2 H), 7.26 (t, J = 7.6 Hz, 1 H), 6.97 (s, 1 H), 6.70 (dt, J = 14.8, 5.7 Hz, 4 H), 5.67 (s, 1 H), 2.92 (s, 6 H). ¹³C NMR (125 MHz, DMSO-d ₆): δ = 164.35, 151.22, 148.74, 133.65, 129.14, 128.23, 127.85, 117.45, 115.55, 114.89, 112.45, 67.14. 2-(4-(Trifluoromethyl)phenyl)-2,3-dihydroquinazolin-4(1H)-one (3aq) Yield: 85% (249 mg); mp 201–205 °C. ESI-MS: m/z = 293.01 [M + 1]⁺. ¹H NMR (500 MHz, DMSO-d ₆): δ = 8.47 (s, 1 H), 7.77 (d, J = 8.5 Hz, 2 H), 7.74 (d, J = 8.7 Hz, 2 H), 7.66 (d, J = 6.4 Hz, 1 H), 7.31–7.23 (m, 2 H), 6.80 (d, J = 8.1 Hz, 1 H), 6.70 (t, J = 7.5 Hz, 1 H), 5.90 (s, 1 H). ¹³C NMR (125 MHz, DMSO-d ₆): δ = 163.94, 147.97, 146.83, 133.92, 129.49 (q, J = 31.5 Hz), 128.14, 127.89, 125.73 (q, J = 3.9 Hz), 123.53, 117.83, 115.43, 114.98, 66.27. 2-(2,4-Diethoxyphenyl)-2,3-dihydroquinazolin-4(1H)-one (3ar) Yield: 75% (235 mg). ESI-MS: m/z = 312.92 [M + 1]⁺. ¹H NMR (500 MHz, DMSO-d ₆): δ = 8.15 (s, 1 H), 7.66–7.62 (m, 1 H), 7.25 (t, J = 7.7 Hz, 1 H), 7.14 (s, 1 H), 7.03–6.97 (m, 2 H), 6.93 (d, J = 8.2 Hz, 1 H), 6.77 (d, J = 8.1 Hz, 1 H), 6.68 (t, J = 7.5 Hz, 1 H), 5.71 (s, 1 H), 3.75 (d, J = 7.5 Hz, 4 H), 1.55 (t, J = 9.2 Hz, 3 H), 1.27 (t, J = 9.5 Hz, 3 H). ¹³C NMR (126 MHz, DMSO-d ₆): δ = 164.23, 149.51, 148.54, 145.81, 134.69, 134.06, 133.64, 127.84, 126.31, 119.69, 117.59, 114.92, 111.73, 111.14, 67.09, 63.32, 55.95, 14.44. 2-(3-Chlorophenyl)-2,3-dihydroquinazolin-4(1H)-one (3as) Yield: 88% (228 mg); mp 178–183 °C. ¹H NMR (500 MHz, DMSO-d ₆): δ = 8.43 (s, 1 H), 7.64 (d, J = 8.1 Hz, 1 H), 7.56 (s, 1 H), 7.46 (s, 1 H), 7.41 (d, J = 5.8 Hz, 2 H), 7.27 (t, J = 8.1 Hz, 1 H), 7.23 (s, 1 H), 6.80 (s, 1 H), 6.70 (t, J = 7.7 Hz, 1 H), 5.81 (s, 1 H). ¹³C NMR (125 MHz, DMSO-d ₆): δ = 163.95, 147.99, 144.86, 133.96, 133.50, 130.76, 128.75, 127.87, 127.24, 125.88, 117.83, 115.39, 114.97, 66.10. 2-(4-Hydroxy-3-methoxyphenyl)-2,3-dihydroquinazolin-4(1H)-one (3at) Yield: 78% (211 mg). ¹H NMR (500 MHz, DMSO-d ₆): δ = 9.12 (s, 1 H), 8.13 (s, 1 H), 7.63 (d, J = 7.6 Hz, 1 H), 7.25 (t, J = 7.6 Hz, 1 H), 7.11 (s, 1 H), 6.97 (s, 1 H), 6.90 (d, J = 8.1 Hz, 1 H), 6.77 (t, J = 7.5 Hz, 2 H), 6.69 (t, J = 7.4 Hz, 1 H), 5.67 (s, 1 H), 3.77 (s, 3 H). ¹³C NMR (125 MHz, DMSO-d ₆): δ = 164.29, 148.66, 147.88, 147.37, 133.69, 132.38, 127.82, 120.10, 117.59, 115.48, 115.38, 114.89, 111.56, 67.29, 56.05. 2-(5-Bromo-2-hydroxyphenyl)-2,3-dihydroquinazolin-4(1H)-one (3au) Yield: 83% (265 mg). ¹H NMR (500 MHz, DMSO-d ₆): δ = 10.27 (s, 1 H), 8.05 (s, 1 H), 7.64 (d, J = 7.8 Hz, 1 H), 7.42 (s, 1 H), 7.33 (d, J = 10.8 Hz, 1 H), 7.25 (t, J = 7.7 Hz, 1 H), 6.85 (d, J = 8.7 Hz, 2 H), 6.79 (d, J = 8.1 Hz, 1 H), 6.69 (t, J = 7.5 Hz, 1 H), 5.98 (s, 1 H). ¹³C NMR (125 MHz, DMSO-d ₆): δ = 164.29, 154.54, 148.28, 133.85, 132.35, 130.15, 127.83, 118.13, 117.75, 115.09, 115.05, 110.34, 61.38. 2-(5-Chloro-2-hydroxyphenyl)-2,3-dihydroquinazolin-4(1H)-one (3av) Yield: 85% (234 mg). ESI-MS: m/z = 274.99 [M + 1]⁺. ¹H NMR (500 MHz, DMSO-d ₆): δ = 10.24 (s, 1 H), 8.05 (s, 1 H), 7.64 (d, J = 7.8 Hz, 1 H), 7.28 (d, J = 2.6 Hz, 1 H), 7.26–7.17 (m, 2 H), 6.89 (d, J = 8.7 Hz, 1 H), 6.84 (s, 1 H), 6.78 (d, J = 8.1 Hz, 1 H), 6.69 (t, J = 7.6 Hz, 1 H), 5.97 (s, 1 H). ¹³C NMR (125 MHz, DMSO-d ₆): δ = 164.28, 154.07, 148.28, 133.84, 129.66, 129.45, 127.82, 127.28, 122.72, 117.74, 117.59, 115.11, 115.05, 61.40. 2-(2-Chloro-6-hydroxyphenyl)-2,3-dihydroquinazolin-4(1H)-one (3aw) Yield: 66% (182 mg). ESI-MS: m/z = 274.94 [M + 1]⁺. ¹H NMR (500 MHz, DMSO-d ₆): δ = 10.11 (s, 1 H), 8.10 (s, 1 H), 7.71 (d, J = 7.8 Hz, 1 H), 7.27 (t, J = 7.7 Hz, 1 H), 7.22 (d, J = 8.1 Hz, 1 H), 6.99 (s, 1 H), 6.95 (d, J = 7.9 Hz, 1 H), 6.91 (d, J = 8.2 Hz, 1 H), 6.77 (d, J = 8.1 Hz, 1 H), 6.73 (t, J = 7.5 Hz, 1 H), 6.61 (s, 1 H). ¹³C NMR (125 MHz, DMSO-d ₆): δ = 164.21, 158.59, 148.70, 134.33, 133.48, 130.84, 127.73, 123.30, 121.19, 117.45, 115.85, 115.27, 114.66, 62.78. 2,3-Dihydroquinazolin-4(1H)-one (4aa) Yield: 42% (63 mg). ESI-MS: m/z = 149.08 [M + 1]⁺. ¹H NMR (500 MHz, DMSO-d ₆): δ = 7.93 (s, 1 H), 7.57 (d, J = 8.2 Hz, 1 H), 6.83–6.69 (m, 4 H), 4.45 (s, 2 H). ¹³C NMR (125 MHz, DMSO-d ₆): δ = 163.86, 151.06, 138.86, 130.13, 117.70, 115.15, 114.15, 66.65. 1′H-Spiro[cycloheptane-1,2′-quinazolin]-4′(3′H)-one (4ad) Yield: 60% (139 mg). ¹H NMR (500 MHz, DMSO-d ₆): δ = 8.04 (s, 1 H), 7.54 (d, J = 7.5 Hz, 1 H), 7.20 (t, J = 7.1 Hz, 1 H), 6.78–6.67 (m, 2 H), 6.59 (t, J = 7.4 Hz, 1 H), 1.97–1.74 (m, 4 H), 1.51 (m, 8 H). ¹³C NMR (125 MHz, DMSO-d ₆): δ = 163.39, 147.21, 133.59, 127.53, 116.76, 114.80, 114.69, 72.37, 41.46, 29.72, 21.32. 2-Heptyl-2,3-dihydroquinazolin-4(1H)-one (4ag) Yield: 88% (217 mg). ESI-MS: m/z = 247.11 [M + 1]⁺. ¹H NMR (500 MHz, DMSO-d ₆): δ = 7.90 (s, 1 H), 7.59 (d, J = 7.8 Hz, 1 H), 7.21 (t, J = 7.8 Hz, 1 H), 6.73 (d, J = 8.1 Hz, 1 H), 6.65 (t, J = 7.5 Hz, 1 H), 6.56 (s, 1 H), 4.68 (t, J = 5.5 Hz, 1 H), 1.66–1.59 (m, 2 H), 1.24 (d, J = 18.6 Hz, 10 H), 0.86 (t, J = 6.8 Hz, 3 H). ¹³C NMR (125 MHz, DMSO-d ₆): δ = 164.44, 148.99, 133.44, 127.82, 114.82, 64.91, 35.50, 31.69, 29.41, 29.23, 23.73, 22.55, 14.42. 4-(4-(Trifluoromethyl)phenyl)-1H-1,2,3-triazole (5c) Yield: 90% (192 mg). ESI-MS: m/z = 214.01 [M + 1]⁺. ¹H NMR (500 MHz, DMSO-d ₆): δ = 15.36 (s, 1 H), 8.48 (s, 1 H), 8.08 (d, J = 8.2 Hz, 2 H), 7.77 (d, J = 8.4 Hz, 2 H). ¹³C NMR (125 MHz, DMSO-d ₆): δ = 145.02, 135.09, 127.88, 126.47, 126.28 (J = 3.95 Hz), 125.72, 123.56, 121.39. 4-(2-Chloro-6-fluorophenyl)-1H-1,2,3-triazole (5e) Yield: 78% (155 mg). ESI-MS: m/z = 197.98 [M + 1]⁺. ¹H NMR (500 MHz, DMSO-d ₆): δ = 15.32 (s, 1 H), 8.04 (s, 1 H), 7.46 (dt, J = 13.0, 6.4 Hz, 2 H), 7.33 (t, J = 8.6 Hz, 1 H). ¹³C NMR (125 MHz, DMSO-d ₆): δ = 161.67, 159.68, 134.34, 131.65, 126.29 (J = 3.44 Hz), 115.33, 115.15 4-(3-Chlorophenyl)-1H-1,2,3-triazole (5f) Yield: 98% (176 mg). ESI-MS: m/z = 180.00 [M + 1]⁺. ¹H NMR (500 MHz, DMSO-d ₆): δ = 15.19 (s, 1 H), 8.44 (s, 1 H), 7.93 (s, 1 H), 7.85 (d, J = 7.9 Hz, 1 H), 7.47 (t, J = 7.9 Hz, 1 H), 7.39 (d, J = 7.9 Hz, 1 H). ¹³C NMR (125 MHz, DMSO-d ₆): δ = 145.27, 134.22, 133.32, 131.22, 128.26, 125.62, 124.52. 4-Chloro-2-(1H-1,2,3-triazol-4-yl)phenol (5g) Yield: 96% (188 mg). ESI-MS: m/z = 195.99 [M + 1]⁺. ¹H NMR (500 MHz, DMSO-d ₆): δ = 10.49 (s, 1 H), 7.90 (s, 1 H), 7.22 (d, J = 11.3 Hz, 1 H), 6.99 (d, J = 8.7 Hz, 1 H). ¹³C NMR (125 MHz, DMSO-d ₆): δ = 153.63, 142.20, 128.79, 126.74, 123.41, 119.29, 118.29. 4-(Anthracen-9-yl)-1H-1,2,3-triazole (5i) Yield: 79% (194 mg). ESI-MS: m/z = 246.04 [M + 1]⁺. ¹H NMR (500 MHz, DMSO-d ₆): δ = 15.46 (s, 1 H), 8.73 (s, 1 H), 8.16 (d, J = 8.5 Hz, 2 H), 7.71 (t, J = 11.2 Hz, 2 H), 7.54 (t, J = 7.4 Hz, 3 H), 7.48 (t, J = 7.6 Hz, 2 H). ¹³C NMR (125 MHz, DMSO-d ₆): δ = 147.56, 143.18, 135.94, 131.30, 131.03, 128.96, 128.41, 127.55, 126.84, 126.07, 125.91. 4-(4-Chlorophenyl)-1H-1,2,3-triazole (5j) Yield: 88% (156 mg). ESI-MS: m/z = 180.02 [M + 1]⁺. ¹H NMR (500 MHz, DMSO-d ₆): δ = 15.22 (d, J = 158.5 Hz, 1 H), 8.28 (s, 1 H), 7.89 (d, J = 8.2 Hz, 2 H), 7.51 (d, J = 8.2 Hz, 2 H). ¹³C NMR (125 MHz, DMSO-d ₆): δ = 133.05, 131.47, 129.43, 127.74, 120.38. 4-(4-Iodophenyl)-1H-1,2,3-triazole (5l) Yield: 80% (217 mg). ESI-MS: m/z = 271.96 [M + 1]⁺. ¹H NMR (500 MHz, DMSO-d ₆): δ = 15.07 (s, 1 H), 8.27 (s, 1 H), 7.80 (d, J = 8.2 Hz, 2 H), 7.68 (d, J = 8.4 Hz, 2 H). ¹³C NMR (125 MHz, DMSO-d ₆): δ = 138.15, 137.66, 131.26, 130.86, 128.07.