Catalyst-Free Three-Component Synthesis of Spirobenzimidazolidines Bearing an Indole Scaffold

Abstract

An efficient catalyst-free one-pot three-component reaction was developed for the synthesis of a new family of N- and S-containing spirocyclic compounds. Various derivatives of spirobenzimidazolidine containing an indole scaffold were synthesized for the first time in a modestly toxic solvent and under mild reaction conditions. The reaction times were of the order of several minutes, and all the products were obtained in moderate to high yields (overall yields 58–80%).

Key words

indoles - benzimidazolidines - spiro compounds - multicomponent reaction - catalyst-free reaction

• References and Notes

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• 18 2H-Thieno[2,3-b]indole-2,3(8H)-dione (4a); Typical Procedure A solution of oxalyl chloride (0.126 g, 1 mmol) in CH₃CN (1 mL) was added dropwise at 25 °C to a stirred solution of thione 1a (0.149 g, 1 mmol) in acetonitrile (3 mL). The orange solid that rapidly formed was collected by filtration, washed with CH₃CN, and dried to give an orange powder; yield: 0.12 g (60%); mp 215–217 °C. IR (KBr): 3232 (NH), 1733 (C=O), 1681 (C=O), 1448, 1399 and 1339 (Ar) cm^–1. ¹H NMR (500 MHz, DMSO-d ₆): δ_H = 6.99 (d, ³ J _HH = 7.6 Hz, 1 H, CH of Ar), 7.08 (t, ³ J _HH = 7.5 Hz, 1 H, CH of Ar), 7.25 (t, ³ J _HH = 7.7 Hz, 1 H, CH of Ar), 7.28 (d, ³ J _HH = 7.2 Hz, 1 H, CH of Ar), 12.61 (s, 1 H, NH). ¹³C NMR (125 MHz, DMSO-d ₆): δ_C = 112.9, 113.6, 119.4, 124.3, 124.7, 126.2, 139.6, 156.6, 170.8, 188.3. Anal. calcd for C₁₀H₅NO₂S (203.00): C, 59.10; H, 2.48; N, 6.89. Found: C, 59.05; H, 2.44; N, 6.92. 8-Methyl-2H-thieno[2,3-b]indole-2,3(8H)-dione (4b) Orange powder; yield: 0.09 g (40%); mp 206–208 °C. IR (KBr): 1767 (C=O), 1688 (C=O), 1511, 1453 and 1415 (Ar) cm^–1. ¹H NMR (500 MHz, DMSO-d ₆): δ_H = 3.81 (s, 3 H, NCH₃), 7.37 (t, ³ J _HH = 7.6 Hz, 1 H, CH of Ar), 7.46 (t, ³ J _HH = 7.5 Hz, 1 H, CH of Ar), 7.67 (d, ³ J _HH = 8.5 Hz, 1 H, CH of Ar), 8.18 (d, ³ J _HH = 8.0 Hz, 1 H, CH of Ar). ¹³C NMR (125 MHz, DMSO-d ₆): δ_C = 31.0, 110.8, 112.3, 120.8, 121.7, 124.3, 126.0, 138.6, 154.5, 167.6, 184.7. Anal. calcd for C₁₁H₇NO₂S (217.02): C, 60.82; H, 3.25; N, 6.45. Found: C, 60.90; H, 3.34; N, 6.38. 8-Phenyl-2H-thieno[2,3-b]indole-2,3(8H)-dione (4c) Orange powder; yield: 0.16 g (58%); mp 168–170 °C. IR (KBr): 1764 (C=O), 1695 (C=O), 1592, 1499 and 1453 (Ar) cm^–1. ¹H NMR (500 MHz, DMSO-d ₆): δ_H = 6.95 (d, ³ J _HH = 8.5 Hz, 1 H, CH of Ar), 7.14–7.28 (m, 3 H, CH of Ar), 7.33–7.40 (m, 3 H, CH of Ar), 7.65 (t, ³ J _HH = 7.5 Hz, 1 H, CH of Ar), 8.24 (d, ³ J _HH = 7.8 Hz, 1 H, CH of Ar). ¹³C NMR (125 MHz, DMSO-d ₆): δ_C = 111.2, 111.7, 119.9, 121.9, 124.4, 126.3, 128.6, 129.4, 130.2, 135.0, 139.5, 156.3, 167.4, 185.1. Anal. calcd for C₁₆H₉NO₂S (279.31): C, 68.80; H, 3.25; N, 5.01. Found: C, 68.77; H, 3.36; N, 5.08.
• 19 1,3-Dihydrospiro[benzimidazole-2,2′-thieno[2,3-b]indol]-3′(8′H)-one (3a); Typical Procedure In a round-bottomed flask equipped with a magnetic stirrer bar, thione 1a (1.5 mmol) was added to CH₃CN (3 mL). A solution of oxalyl chloride (1.5 mmol) in CH₃CN (1 mL) was added slowly to the flask. When the addition was complete, benzene-1,2-diamine (2a; 1 mmol) was added, and the mixture was stirred at r.t. until the reaction was complete (TLC). The mixture was then filtered and the precipitate was washed with CH₃CN (3 × 4 mL) to give an red amorphous powder; yield: 0.22 g (76%); mp 302–304 °C (dec.). IR (KBr): 3187 (NH), 1673 (C=O), 1588, 1504, 1456 and 1388 (Ar) cm^–1. ¹H NMR (500 MHz, DMSO-d ₆): δ_H = 7.03–7.13 (m, 3 H, CH of Ar), 7.21–7.30 (m, 3 H, CH of Ar), 7.48 (d, ³ J _HH = 7.7 Hz, 1 H, CH of Ar), 8.71 (d, ³ J _HH = 8.1 Hz, 1 H, CH of Ar), 11.92 (s, 1 H, NH of indole), 12.35 (s, 1 H, NH), 12.43 (s, 1 H, NH). ¹³C NMR (125 MHz, DMSO-d ₆): δ_C = 106.6, 109.6, 115.5, 116.9, 121.4, 124.4, 124.5, 126.0, 126.0, 126.4, 129.1, 139.1, 144.0, 157.0, 176.8. Anal. calcd for C₁₆H₁₁N₃OS (293.06): C, 65.51; H, 3.78; N, 14.32. Found: C, 65.55; H, 3.72; N, 14.24. 5-Chloro-1,3-dihydrospiro[benzimidazole-2,2′-thieno[2,3-b]indol]-3′(8′H)-one (3b) Amorphous red powder: 0.24 g (72%); mp 368–370 °C (dec.); IR (KBr): 3112 (NH), 1688 (C=O), 1592, 1499, 1455 and 1383 (Ar) cm^–1. ¹H NMR (500 MHz, DMSO-d ₆): δ_H = 7.02 (t, ³ J _HH = 7.3 Hz, 1 H, CH of Ar), 7.05–7.17 (m, 4 H, CH of Ar), 7.47 (s, 1 H, CH of Ar), 8.68 (d, ³ J _HH = 8.1 Hz, 1 H, CH of Ar), 11.99 (s, 1 H, NH of indole), 12.33 (s, 1 H, NH), 12.49 (s, 1 H, NH).¹³C NMR (125 MHz, DMSO-d ₆): δ_C = 107.3, 109.7, 114.8, 116.7, 117.0, 121.6, 123.0, 125.2, 126.7, 127.3, 128.0, 139.4, 143.5, 156.9, 177.9. Anal. calcd for C₁₆H₁₀ClN₃OS (327.02): C, 58.63; H, 3.08; N, 12.82. Found: C, 58.68; H, 3.02; N, 12.89. 5-Methyl-1,3-dihydrospiro[benzimidazole-2,2′-thieno[2,3-b]indol]-3′(8′H)-one (3c) Amorphous red powder; yield: 0.24 g (78%); mp 296–298 °C (dec.); IR (KBr): 3246 (NH), 1672 (C=O), 1590, 1523, 1450 and 1385 (Ar) cm^–1. ¹H NMR (500 MHz, DMSO-d ₆): δ_H = 2.34 (s, 3 H, CH₃), 7.02–7.11 (m, 5 H, CH of Ar), 7.35 (d, ³ J _HH = 8.3 Hz, 1 H, CH of Ar), 8.71 (d, ³ J _HH = 7.9 Hz, 1 H, CH of Ar), 11.82 (s, 1 H, NH of indole), 12.24 (s, 1 H, NH), 12.36 (s, 1 H, NH). ¹³C NMR (125 MHz, DMSO-d ₆): δ_C = 20.8, 106.6, 109.6, 115.3, 116.7, 121.3, 121.4, 123.3, 124.4, 125.6, 126.4, 127.0, 134.1, 139.1, 143.9, 156.8, 176.6. Anal. calcd for C₁₇H₁₃N₃OS (307.08): C, 66.43; H, 4.26; N, 13.67. Found: C, 66.39; H, 4.34; N, 13.73. 5,6-Dimethyl-1,3-dihydrospiro[benzimidazole-2,2′-thieno[2,3-b]indol]-3′(8′H)-one (3d) Amorphous red powder; yield: 0.26 g (80%); mp 334–336 °C (dec.); IR (KBr): 3157 (NH), 1682 (C=O), 1591, 1508, 1450 and 1391 (Ar) cm^–1. ¹H NMR (500 MHz, DMSO-d ₆): δ_H = 2.15 (s, 6 H, 2CH₃), 6.86–7.23 (m, 5 H, CH of Ar), 8.70 (d, ³ J _HH = 6.4 Hz, 1 H, CH of Ar), 11.77 (s, 1 H, NH of indole), 12.23 (s, 1 H, NH), 12.31 (s, 1 H, NH). ¹³C NMR (125 MHz, DMSO-d ₆): δ_C = 19.4, 107.8, 109.6, 113.7, 116.1, 118.3, 123.7, 125.6, 126.2, 126.5, 131.9, 140.3, 155.6, 177.3. Anal. calcd for C₁₈H₁₅N₃OS (321.09): C, 67.27; H, 4.70; N, 13.07. Found: C, 67.34; H, 4.73; N, 13.03. 8′-Methyl-1,3-dihydrospiro[benzimidazole-2,2′-thieno[2,3-b]indol]-3′(8′H)-one (3e) Amorphous red powder; yield: 0.20 g (66%); mp 286–288 °C (dec.); IR (KBr): 3032 (NH), 1669 (C=O), 1521, 1454 and 1363 (Ar) cm^–1. ¹H NMR (500 MHz, DMSO-d ₆): δ_H = 3.74 (s, 3 H, NCH₃), 7.22–7.35 (m, 6 H, CH of Ar), 7.50 (d, ³ J _HH = 7.9 Hz, 1 H, CH of Ar), 8.72 (d, ³ J _HH = 8.1 Hz, 1 H, CH of Ar), 11.92 (s, 1 H, NH), 12.35 (s, 1 H, NH). ¹³C NMR (125 MHz, DMSO-d ₆): δ_C = 31.4, 109.3, 110.6, 115.4, 116.9, 122, 124.2, 124.4, 128.1, 129.7, 138.1, 143.4, 157.0, 173.1. Anal. calcd for C₁₇H₁₃N₃OS (307.08): C, 66.43; H, 4.26; N, 13.67. Found: C, 66.37; H, 4.33; N, 13.62. 5-Chloro-8′-methyl-1,3-dihydrospiro[benzimidazole-2,2′-thieno[2,3-b]indol]-3′(8′H)-one (3f) Amorphous red powder; yield: 0.21 g (61%); mp 350–352 °C (dec.); IR (KBr): 3054 (NH), 1691 (C=O), 1500, 1455 and 1388 (Ar) cm^–1. ¹H NMR (500 MHz, DMSO-d ₆): δ_H = 3.69 (s, 3 H, NCH₃), 7.14–7.24 (m, 4 H, CH of Ar), 7.28 (d, ³ J _HH = 7.9 Hz, 1 H, CH of Ar), 7.45 (s, 1 H, CH of Ar), 8.67 (d, ³ J _HH = 8.1 Hz, 1 H, CH of Ar), 11.97 (s, 1 H, NH), 12.31 (s, 1 H, NH). ¹³C NMR (125 MHz, DMSO-d ₆): δ_C = 30.6, 109.4, 110.6, 114.8, 116.2, 117.0, 118.4, 122.2, 123.0, 125.2, 127.0, 127.3, 128.0, 138.5, 142.9, 155.4, 176.3. Anal. calcd for C₁₇H₁₂ClN₃OS (341.04): C, 59.74; H, 3.54; N, 12.29. Found: C, 59.66; H, 3.63; N, 12.37. 5,8′-Dimethyl-1,3-dihydrospiro[benzimidazole-2,2′-thieno[2,3-b]indol]-3′(8′H)-one (3g) Amorphous red powder; yield: 0.21 g (64%); mp 272–274 °C (dec.); IR (KBr): 3042 (NH), 1687 (C=O), 1594, 1455 and 1362 (Ar) cm^–1. ¹H NMR (500 MHz, DMSO-d ₆): δ_H = 2.36 (s, 3 H, CH₃), 3.75 (s, 3 H, NCH₃), 7.10–7.24 (m, 4 H, CH of Ar), 7.34–7.38 (m, 2 H, CH of Ar), 8.73 (d, ³ J _HH = 7.6 Hz, 1 H, CH of Ar), 12.32 (s, 1 H, NH), 12.35 (s, 1 H, NH). ¹³C NMR (125 MHz, DMSO-d ₆): δ_C = 20.8, 31.4, 109.2, 110.6, 115.5, 116.7, 120.7, 121.9, 124.2, 124.4, 127.0, 128.1, 129.6, 134.0, 136.0, 143.4, 156.8, 173.6. Anal. calcd for C₁₈H₁₅N₃OS (321.09): C, 67.27; H, 4.70; N, 13.07. Found: C, 67.30; H, 4.76; N, 13.11. 5,6,8′-Trimethyl-1,3-dihydrospiro[benzimidazole-2,2′-thieno[2,3-b]indol]-3′(8′H)-one (3h) Amorphous red powder; yield: 0.22 g (67%); mp 312–314 °C (dec.); IR (KBr): 3061 (NH), 1680 (C=O), 1514, 1447 and 1394 (Ar) cm^–1. ¹H NMR (500 MHz, DMSO-d ₆): δ_H = 2.16 (s, 6 H, 2CH₃), 3.77 (s, 3 H, NCH₃), 7.14–7.28 (m, 5 H, CH of Ar), 8.70 (d, ³ J _HH = 7.5 Hz, 1 H, CH of Ar), 11.79 (s, 1 H, NH), 12.28 (s, 1 H, NH). ¹³C NMR (125 MHz, DMSO-d ₆): δ_C = 19.4, 30.7, 108.9, 111.3, 114.9, 116.1, 118.6, 123.8, 127.1, 128.6, 129.2, 131.5, 141.6, 155.6, 179.2. Anal. calcd for C₁₉H₁₇N₃OS (335.11): C, 68.04; H, 5.11; N, 12.53. Found: C, 68.11; H, 5.08; N, 12.44. 5-Methyl-8′-phenyl-1,3-dihydrospiro[benzimidazole-2,2′-thieno[2,3-b]indol]-3′(8′H)-one (3i) Amorphous red powder; yield: 0.27 g (71%); mp 280–282 °C (dec.); IR (KBr): 3035 (NH), 1669 (C=O), 1491, 1430 and 1358 (Ar) cm^–1. ¹H NMR (500 MHz, DMSO-d ₆): δ_H = 2.33 (s, 3 H, CH₃), 7.06–7.13 (m, 3 H, CH of Ar), 7.38 (d, ³ J _HH = 7.5 Hz, 2 H, CH of Ar), 7.48 (d, ³ J _HH = 7.0 Hz, 1 H, CH of Ar), 7.56 (t, ³ J _HH = 8.0 Hz, 2 H, CH of Ar), 7.65 (t, ³ J _HH = 7.5 Hz, 2 H, CH of Ar), 7.96 (d, ³ J _HH = 8.5 Hz, 1 H, CH of Ar), 8.75 (d, ³ J _HH = 7.5 Hz, 1 H, CH of Ar), 12.31 (s, 1 H, NH), 12.34 (s, 1 H, NH). ¹³C NMR (125 MHz, DMSO-d ₆): δ_C = 20.8, 106.8, 109.3, 111.1, 116.9, 122.0, 122.1, 123.1, 124.5, 126.4, 127.1, 127.5, 128.6, 129.2, 130.1, 134.2, 137.2, 141.2, 144.2, 156.7, 177.2. Anal. calcd for C₂₃H₁₇N₃OS (383.47): C, 72.04; H, 4.47; N, 10.96. Found: C, 71.95; H, 4.53; N, 10.93. 5-Chloro-8′-phenyl-1,3-dihydrospiro[benzimidazole-2,2′-thieno[2,3-b]indol]-3′(8′H)-one (3j) Amorphous red powder; yield: 0.27 g (68%); mp 292–294 °C (dec.); IR (KBr): 3047 (NH), 1677 (C=O), 1495, 1437 and 1361 (Ar) cm^–1. ¹H NMR (500 MHz, DMSO-d ₆): δ_H = 7.10–7.14 (m, 3 H, CH of Ar), 7.38 (d, ³ J _HH = 7.5 Hz, 2 H, CH of Ar), 7.55–7.59 (m, 3 H, CH of Ar), 7.65 (t, ³ J _HH = 8.0 Hz, 2 H, CH of Ar), 7.95 (d, ³ J _HH = 7.5 Hz, 1 H, CH of Ar), 8.73 (d, ³ J _HH = 7.5 Hz, 1 H, CH of Ar), 11.99 (s, 1 H, NH), 12.46 (s, 1 H, NH).¹³C NMR (125 MHz, DMSO-d ₆): δ_C = 107.4, 109.5, 111.2, 114.8, 116.5, 117.0, 122.0, 123.1, 125.9, 126.7, 127.0, 128.3, 129.1, 129.3, 130.2, 137.0, 141.5, 143.9, 156.9, 176.7. Anal. calcd for C₂₂H₁₄ClN₃OS (403.88): C, 65.43; H, 3.49; N, 10.40. Found: C, 65.46; H, 3.41; N, 10.45. 5-Nitro-1,3-dihydrospiro[benzimidazole-2,2′-thieno[2,3-b]indol]-3′(8′H)-one (3k) Amorphous brown powder; yield: 0.23 g (70%); mp 348–350 °C (dec.); IR (KBr): 3186 (NH), 1683 (C=O), 1602 (NO₂), 1528, 1461, 1386 (Ar), 1334 (NO₂) cm^–1. ¹H NMR (500 MHz, DMSO-d ₆): δ_H = 6.87–7.22 (m, 4 H, CH of Ar), 7.88 (s, 1 H, CH of Ar), 7.92 (d, ³ J _HH = 7.4 Hz, 1 H, CH of Ar), 8.69 (d, ³ J _HH = 7.3 Hz, 1 H, CH of Ar), 11.74 (s, 1 H, NH of indole), 12.37 (s, 1 H, NH), 12.60 (s, 1 H, NH). ¹³C NMR (125 MHz, DMSO-d ₆): δ_C = 109.9, 110.2, 111.6, 112.0, 114.6, 116.8, 120.2, 122.0, 123.6, 125.9, 127.2, 133.8, 138.7, 142.4, 157.1, 178.5. Anal. calcd for C₁₆H₁₀N₄O₃S (338.34): C, 56.80; H, 2.98; N, 16.56. Found: C, 56.87; H, 3.07; N, 16.52. 8′-Methyl-5-nitro-1,3-dihydrospiro[benzimidazole-2,2′-thieno[2,3-b]indol]-3′(8′H)-one (3l) Amorphous brown powder; yield: 0.20 g (58%); mp 306–308 °C (dec.); IR (KBr): 3049 (NH), 1689 (C=O), 1601 (NO₂), 1529, 1456, 1334 (Ar), 1327 (NO₂) cm^–1. ¹H NMR (500 MHz, DMSO-d ₆): δ_H = 3.7 (s, 3 H, NCH₃), 7.16–7.23 (m, 2 H, CH of Ar), 7.34–7.38 (m, 2 H, CH of Ar), 7.95 (s, 1 H, CH of Ar), 7.98 (d, ³ J _HH = 7.4 Hz, 1 H, CH of Ar), 8.73 (d, ³ J _HH = 8.5 Hz, 1 H, CH of Ar), 12.43 (s, 1 H, NH), 12.67 (s, 1 H, NH). ¹³C NMR (125 MHz, DMSO-d ₆): δ_C = 106.8, 109.3, 111.1, 116.9, 122.0, 122.1, 123.1, 124.5, 126.4, 127.1, 127.5, 128.6, 129.2, 130.1, 134.2, 137.2, 141.2, 144.2, 156.7, 177.2. Anal. calcd for C₁₇H₁₂N₄O₃S (352.37): C, 57.95; H, 3.43; N, 15.90. Found: C, 57.90; H, 3.37; N, 15.98. 2-[(2-Aminoethyl)imino]-2H-thieno[2,3-b]indol-3(8H)-one (5) Amorphous yellow powder; yield: 0.17 g (71%); mp 184–186 °C (dec.); IR (KBr): 3295 (NH), 3201 (NH), 1660 (C=O), 1522, 1437, 1328 (Ar) cm^–1. ¹H NMR (500 MHz, DMSO-d ₆): δ_H = 3.39–3.42 (m, 4 H, CH₂), 6.86 (d, ³ J _HH = 7.6 Hz, 1 H, CH of Ar), 6.93 (t, ³ J _HH = 8.2 Hz, 1 H, CH of Ar), 7.92 (d, ³ J _HH = 8.4 Hz, 1 H, CH of Ar), 8.07 (s, 2 H, NH₂), 8.34 (t, ³ J _HH = 7.5 Hz, 1 H, CH of Ar), 10.92 (s, 1 H, NH). ¹³C NMR (125 MHz, DMSO-d ₆): δ_C = 36.5, 41.0, 108.2, 109.4, 119.0, 120.3, 121.1, 123.8, 137.4, 152.3, 160.6, 171.2. Anal. calcd for C₁₂H₁₁N₃OS (245.30): C, 58.76; H, 4.52; N, 17.13. Found: C, 58.71; H, 4.59; N, 17.09.