Synlett 2016; 27(11): 1738-1742
DOI: 10.1055/s-0035-1561852
letter
© Georg Thieme Verlag Stuttgart · New York

Reaction between 4-Nitro-1,3-diarylbutan-1-ones and Ammonium Acetate in the Presence of Morpholine and Sulfur: An Efficient Synthesis of 2,4-Diarylpyrroles

Mehdi Adib*
a   School of Chemistry, College of Science, University of Tehran, P. O. Box 14155-6455, Tehran, Iran   Email: madib@khayam.ut.ac.ir
,
Neda Ayashi
a   School of Chemistry, College of Science, University of Tehran, P. O. Box 14155-6455, Tehran, Iran   Email: madib@khayam.ut.ac.ir
,
Fatemeh Heidari
a   School of Chemistry, College of Science, University of Tehran, P. O. Box 14155-6455, Tehran, Iran   Email: madib@khayam.ut.ac.ir
,
Peiman Mirzaei
b   Department of Chemistry, Shahid Beheshti University, Tehran, Iran
› Author Affiliations
Further Information

Publication History

Received: 10 December 2015

Accepted after revision: 01 March 2016

Publication Date:
30 March 2016 (online)


Abstract

An efficient synthesis of 2,4-diarylpyrroles is described. Heating a mixture of a 4-nitro-1,3-diarylbutan-1-one and ammonium acetate in the presence of morpholine and sulfur afforded the corresponding 2,4-diarylpyrroles in excellent yields.

 
  • References and Notes

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  • 20 General Procedure for the Preparation of 2,4-Diarylpyrroles 3a–o, Exemplified with 3a A mixture of 4-nitro-1,3-diphenylbutan-1-one (1a, 1 mmol), sulfur (3 mmol), morpholine (3 mmol), and NH4OAc (6 mmol) within a 5 mL round-bottomed flask was magnetically stirred in a silicone oil bath at 80 °C for 30 min. Progress of the reaction was followed by TLC monitoring. Then the reaction mixture was cooled to ambient temperature, H2O (2.5 mL) was added, and the product was extracted into CH2Cl2 (2 × 2.5 mL). The organic layer was dried over Na2SO4, filtered, the solvent was removed, and the residue was purified by crystallization from EtOAc. 2,4-Diphenyl-1H-pyrrole (3a) Colorless crystals, mp 176–177 °C, yield 0.214 g, 98%. IR (KBr): 3435 (NH), 1598, 1481, 1451, 1411, 1258, 1185, 1157, 1129, 1075, 1030, 903, 807, 746, 688 cm–1. 1H NMR (300.1 MHz, DMSO-d 6): δ = 6.96 (1 H, s, CH), 7.13 (1 H, t, J = 7.5 Hz, CH), 7.18 (1 H, t, J = 7.5 Hz, CH), 7.32 (2 H, t, J = 7.5 Hz, 2 × CH), 7.35 (1 H, s, CH), 7.37 (2 H, t, J = 7.6 Hz, 2 × CH), 7.61 (2 H, d, J = 7.5 Hz, 2 × CH), 7.69 (2 H, d, J = 7.5 Hz, 2 × CH), 11.45 (1 H, br s, NH). 13C NMR (75.5 MHz, DMSO-d 6): δ = 103.7 (C3H), 117.1 (C5H), 123.9 (2 × CH), 124.9 (2 × CH), 125.2 (C4), 125.5 and 126.2 (2 × CH), 129.0 (2 × CH), 129.2 (2 × CH), 132.7 and 133.1 (2 × C) 136.2 (C2). MS: m/z (%) = 219 (100) [M+], 191 (37), 165 (15), 115 (38), 110 (13), 102 (10), 95 (6), 89 (11), 77 (10), 63 (10), 51 (11). HRMS (ES+): m/z calcd for C16H14N [M + H]+: 220.1126; found: 220.1124. 4-(3-Methylphenyl)-2-phenyl-1H-pyrrole (3c) Colorless crystals, mp 140–141 °C, yield 0.214 g, 92%. IR (KBr): 3401 (NH), 1597, 1479, 1451, 1413, 1265, 1225, 1188, 1130, 1038, 929, 898, 760, 688 cm–1. 1H NMR (300.1 MHz, DMSO-d 6): δ = 2.34 (3 H, s, CH3), 6.95 (1 H, d, J = 7.5 Hz, CH), 6.97 (1 H, s, CH), 7.19 (1 H, t, J = 7.8 Hz, CH), 7.21(1 H, dd, J = 8.1, 7.8 Hz, CH), 7.33 (1 H, s, CH), 7.36 (1 H, d, J = 7.5 Hz, CH), 7.40 (2 H, t, J = 7.5 Hz, 2 × CH), 7.46 (1 H, s, CH), 7.69 (2 H, d, J = 7.8 Hz, 2 × CH), 11.45 (1 H, br s, NH). 13C NMR (75.5 MHz, DMSO-d 6): δ = 21.7 (CH3), 103.7 (C3H), 117.0 (C5H), 122.1 (CH), 123.8 (2 × CH), 125.2 (C4), 125.5, 126.1, 126.2 and 128.9 (4 × CH), 129.2 (2 × CH), 132.6, 133.1, 136.0 and 137.9 (3 × C and C2). MS: m/z (%) = 233 (100) [M+], 217 (17), 202 (13), 189 (15), 165 (7), 129 (11), 115 (25), 102 (10), 89 (8), 77 (13), 63 (7), 51 (8). HRMS (ES+): m/z calcd for C17H16N [M + H]+: 234.1283; found: 234.1291. 2-(4-Methylphenyl)-4-phenyl-1H-pyrrole (3h) Colorless crystals, mp 207–209 °C, yield 0.214 g, 92%. IR (KBr): 3385 (NH), 1598, 1532, 1491, 1442, 1259, 1212, 1184, 1132, 1078, 1033, 922, 802, 747, 688 cm–1. 1H NMR (300.1 MHz, DMSO-d 6): δ = 2.30 (3 H, s, CH3), 6.90 (1 H, s, CH), 7.12 (1 H, t, J = 7.5 Hz, CH), 7.19 (2 H, d, J = 7.8 Hz, 2 × CH), 7.31 (1 H, s, CH), 7.32 (2 H, t, J = 7.5 Hz, 2 × CH), 7.58 (2 H, d, J = 7.5 Hz, 2 × CH), 7.61 (2 H, d, J = 7.8 Hz, 2 × CH), 11.39 (1 H, br s, NH). 13C NMR (75.5 MHz, DMSO-d 6): δ = 21.2 (CH3), 103.1 (C3H), 116.6 (C5H), 123.8 (2 × CH), 124.8 (2 × CH), 125.0 (C4), 125.4 (CH), 129.0 (2 × CH), 129.7 (2 × CH), 130.4, 132.8, 135.3 and 136.2 (3 × C and C2). MS: m/z (%) = 233 (100) [M+], 217 (25), 202 (21), 189 (21), 178 (8), 165 (9), 128 (8), 115 (43), 102 (12), 89 (15), 77 (16), 63 (11), 51 (11). HRMS (ES+): m/z calcd for C17H16N [M + H]+: 234.1283; found: 234.1278. 4-(4-Methoxyphenyl)-2-(4-methylphenyl)-1H-pyrrole (3j) Colorless crystals, mp 179–181 °C, yield 0.239 g, 91%. IR (KBr): 3437 (NH), 1610, 1581, 1533, 1500, 1439, 1297, 1238, 1177, 1130, 1033, 1032, 923, 829, 793, 716, 631 cm–1. 1H NMR (300.1 MHz, DMSO-d 6): δ = 2.30 (3 H, s, CH3), 3.75 (3 H, s, OCH3), 6.81 (1 H, s, CH), 6.90 (2 H, d, J = 8.7 Hz, 2 × CH), 7.18 (2 H, d, J = 8.1 Hz, 2 × CH), 7.19 (1 H, s, CH), 7.51 (2 H, d, J = 8.7 Hz, 2 × CH), 7.56 (2 H, d, J = 8.1 Hz, 2 × CH), 11.27 (1 H, br s, CH). 13C NMR (75.5 MHz, DMSO-d 6): δ = 21.2 (CH3), 55.5 (OCH3), 102.9 (C3H), 114.4 (2 × CH), 115.7 (C5H), 123.8 (2 × CH), 124.9 (C4), 126.0 (2 × CH), 129.0 (C), 129.7 (2 × CH), 130.5 and 132.6 (2 × C), 135.1 (C2), 157.5 (CO). MS: m/z (%) = 263 (100) [M+], 248 (90), 220 (12), 204 (12), 178 (14), 165 (7), 152 (6), 132 (10), 119 (23), 102 (6), 91 (17), 77 (10), 65 (7).
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