Chiral BrØnsted acid-catalyzed friedel-crafts reaction of indoles

Current Organic Chemistry

Volumn 18, Issue 16, 2014, Pages 2108-2124

  Bhadury, Pinaki S ^a   Pang, Jun ^a  

^a NorthernChem Inc   (Canada)

Author keywords

Asymmetric organocatalysis; BINOL; Bioactivity; Chiral Br nsted acids; Enantioselectivity; Friedel Crafts alkylation; Hydrogenbond; Indole; Synthesis

Indexed keywords

ALKYLATION; FRIEDEL-CRAFTS REACTION; POLYCYCLIC AROMATIC HYDROCARBONS; STEREOCHEMISTRY;

ASYMMETRIC ORGANOCATALYSIS; BINOL; CHIRAL BRØNSTED ACID; FRIEDEL-CRAFT REACTIONS; FRIEDEL-CRAFTS ALKYLATION; HYDROGENBOND; INDOLE; NATURAL PRODUCTS; ORGANOCATALYTIC; PHARMACOPHORES;

CATALYSIS;

EID: 84911465207     PISSN: 13852728     EISSN: None     Source Type: Journal    
DOI: 10.2174/1385272819666140809010818     Document Type: Article

References (96)

1. Lim, K. H.; Hiraku, O.; Komiyama, K.; Koyano, T.; Hayashi, M.; Kam, T. S. Biologically active indole alkaloids from Kopsia arborea. J. Nat. Prod., 2007, 70, 1302-1307.
2. Yokoshima, S.; Ueda, T.; Kobayashi, S.; Sato, A.; Kuboyama, T.; Toku-yama, H.; Fukuyama, T. Stereocontrolled total synthesis of (+)-vinblastine. J. Am. Chem. Soc., 2002, 124, 2137-2139.
3. Yamashita, T.; Kawai, N.; Tokuyama, H.; Fukuyama, T. Stereocontrolled total synthesis of (-)-eudistomin C. J. Am. Chem. Soc., 2005, 127, 15038-15039.
4. Cai, X. H.; Tan, Q. G.; Liu, Y. P.; Feng, T.; Du, Z. Z.; Li, W. Q.; Luo, X. D. A cage-monoterpene indole alkaloid from Alstonia scholaris. Org. Lett., 2008, 10, 577-580.
5. Somei, M.; Yamada, M. Simple indole alkaloids and those with a nonrearranged monoterpenoid unit. Nat. Prod. Rep., 2004, 21, 278-311.
6. Humphrey, G. R.; Kuethe, J. T. Practical methodologies for the synthesis of indoles. Chem. Rev., 2006, 106, 2875-2911.
7. Bandini, M.; Eichholzer, A. Catalytic functionalization of indoles in a new dimension. Angew. Chem. Int. Ed., 2009, 48, 9608-9644.
8. Bandini, M. Electrophilicity: The "dark side" of indole chemistry. Org. Biomol. Chem., 2013, 11, 5206-5212.
9. Poulsen, T. B.; Jørgensen, K. A. Catalytic asymmetric Friedel-Crafts alkyla-tion reactions-copper showed the way. Chem. Rev., 2008, 108, 2903-2915.
10. Giuseppe, B.; Paolo, M. A novel organocatalytic tool for the iminium activation of α, ß-unsaturated ketones. Synlett., 2008, (12), 1759-1772.
11. Rueping, M.; Leawsuwan, W.; Antonchick, A. P.; Nachtsheim, B. J. Chiral Brønsted acids in the catalytic asymmetric Nazarov cyclization-the first enantioselective organocatalytic electrocyclic reaction. Angew. Chem. Int. Ed., 2007, 46, 2097-2100.
12. Nakashima, D.; Yamamoto, H. Design of chiral N-triflyl phosphoramide as a strong chiral Brønsted acid and its application to asymmetric Diels-Alder reaction. J. Am. Chem. Soc., 2006, 128, 9626-9627.
13. Bhadury, P. S.; Yang, S.; Song, B. A. Catalytic synthesis of optically active β-amino acid derivatives. Curr. Org. Synth., 2012, 9, 695-726.
14. Bhadury, P. S.; Li, H. Organocatalytic asymmetric hydrophosphonyla-tion/Mannich reactions using thiourea, cinchona and Brønsted acid catalysts. Synlett., 2012, 23, 1108-1131.
15. Bhadury, P. S.; Yao, Y.; He, Y. Organocatalytic application of axially dissymmetric BINOLs and their conversion into binaphthyl phosphoric acids. Curr. Org. Chem., 2012, 16, 1730-1753.
16. Bhadury, P. S.; Song, B. A. Chemistry of organocatalytic asymmetric Man-nich reactions. Curr. Org. Chem., 2010, 14, 1989-2006.
17. Bhadury, P. S.; Song, B. A.; Yang, S.; Hu, D. Y.; Xue, W. Bifunctional chiral organocatalysts in organic transformations. Curr. Org. Synth., 2009, 6, 380-399.
18. Bhadury, P. S.; Song, B. A.; Yang, S.; Zhang, Y. P.; Zhang, S. Some potential chiral catalysts for preparation of asymmetric α-aminophosphonates. Curr. Org. Synth., 2008, 5, 134-150.
19. Bhadury, P. S.; Sun, Z. Axially chrial BrØnsted acid-catalyzed transformations of electrophilic imines. Curr. Org. Chem., 2014, 18, 127-150.
20. Jia, Y. X.; Xie, J. H.; Duan, H. F.; Wang, L. X.; Zhou, Q. L. Asymmetric Friedel-Crafts addition of-ilndoles to N-sulfonyl aldimines: A simple approach to optically active 3-indolyl-methanamine derivatives. Org. Lett., 2006, 8, 1621-1624.
21. Johannsen, M. An enantioselective synthesis of heteroaromatic N-tosyl α-amino acids. Chem. Commun., 1999, (21), 2233-2234.
22. Faulkner, J. Marine natural products. Nat. Prod. Rep., 2002, 19, 1-49.
23. Bosch, J.; Bennasar, M. L. A general method for the synthesis of bridged indole alkaloids. Addition of carbon nucleophiles to N-alkylpyridinium salts. Synlett., 1995, (6), 587-596.
24. Wang, Y. Q.; Song, J.; Hong, R.; Li, H.; Deng, L. Asymmetric Friedel-Crafts reaction of indoles with imines by an organic catalyst. J. Am. Chem. Soc., 2006, 128, 8156-8157.
25. Kang, Q.; Zhao, Z. A.; You, S. L. Highly enantioselective Friedel-Crafts reaction of indoles with imines by a chiral phosphoric acid. J. Am. Chem. Soc., 2007, 129, 1484-1485.
26. Rowland, G. B.; Rowland, E. B.; Liang, Y.; Perman, J. A.; Antilla, J. C. The highly enantioselective addition of indoles to N-acyl imines with use of a chiral phosphoric acid catalyst. Org. Lett., 2007, 9, 2609-2611.
27. Ramesh, C.; Banerjee, J.; Pal, R.; Das, B. Silica supported sodium hydrogen sulfate and amberlyst-15: two efficient heterogeneous catalysts for facile synthesis of bis-and tris(1H-indol-3-yl)methanes from indoles and carbonyl compounds. Adv. Synth Catal., 2003, 345, 557-559.
28. Nair, V.; Thomas, S.; Mathew, S. C.; Abhilash, K. G. Recent advances in the chemistry of triaryl-and triheteroarylmethanes. Tetrahedron, 2006, 62, 6731-6747.
29. Shchepinov, M. S.; Korshun, V. A. Recent applications of bifunctional trityl groups. Chem. Soc. Rev., 2003, 32, 170-180.
30. Nair, V.; Abhilash, K. G.; Vidya, N. Practical synthesis of triaryl-and trihet-eroarylmethanes by reaction of aldehydes and activated arenes promoted by gold(III) chloride. Org. Lett., 2005, 7, 5857-5859.
31. Podder, S.; Choudhury, J.; Roy, U. K.; Roy, S. Dual-reagent catalysis within Ir-Sn domain: Highly selective alkylation of arenes and heteroarenes with aromatic aldehydes. J. Org. Chem., 2007, 72, 3100-3103.
32. Wang, Z.; Sun, X.; Wu, J. FeC An efficient catalyst for reactions of electron-rich arenes with imines or aziridines. Tetrahedron, 2008, 64, 5013-5018.
33. Sun, S.; Wang, M.; Deng, H.; Liu, Q. A practical route to 2, 3-di-/1, 2, 3-trisubstituted indolizines from α-EWG ketene S, S-acetals and their application in bis(1-indolizinyl)methane synthesis. Synthesis, 2008, (4), 573-583.
34. Liu, C. R.; Li, M. B.; Yang, C. F.; Tian, S. K. Catalytic selective bis-arylation of imines with anisole, phenol, thioanisole and analogues. Chem. Commun., 2008, (10), 1249-1251.
35. Sun, F. L.; Zheng, X. J.; Gu, Q.; He, Q. L.; You, S. L. Enantioselective synthesis of unsymmetrical triarylmethanes by chiral Brønsted acids. Eur. J. Org. Chem., 2010, 2010, 47-50.
36. Akiyama, T.; Itoh, J.; Yokota, K.; Fuchibe, K. Enantioselective Mannich-type reaction catalyzed by a chiral Brønsted acid. Angew. Chem. Int. Ed., 2004, 43, 1566-1568.
37. Terada, M. Chiral phosphoric acids as versatile catalysts for enantioselective transformations. Synthesis, 2010, (12), 1929-1982.
38. Uraguchi, D.; Terada, M. Chiral Brønsted acid-catalyzed direct Mannich reactions via electrophilic activation. J. Am. Chem. Soc., 2004, 126, 5356-5357.
39. Nakashima, D.; Yamamoto, H. Design of chiral N-triflyl phosphoramide as a strong chiral Brønsted acid and its application to asymmetric Diels-Alder reaction. J. Am. Chem. Soc., 2006, 128, 9626-9627.
40. Hatano, M.; Maki T.; Moriyama, K.; Arinobe, M.; Ishihara, K. Pyridinium 1, 1'-binaphthyl-2, 2'-disulfonates as highly effective chiral Brønsted acid-base combined salt catalysts for enantioselective Mannich-type reaction. J. Am. Chem. Soc., 2008, 130, 16858-16860.
41. Hatano, M.; Sugiura, Y.; Akakura, M.; Ishihara, K. Enantioselective Friedel-Crafts aminoalkylation catalyzed by chiral ammonium 1, 1'-binaphthyl-2, 2'-disulfonates. Synlett., 2011, (9), 1247-1250.
42. Hatano, M.; Sugiura, Y.; Ishihara, K. Synthesis of chiral 3, 3'-disubstituted I, 1'-binaphthyl-2, 2'-disulfonic acids. Tetrahedron: Asymm., 2010, 21, 1311-1314.
43. Chen, L. Y.; He, H.; Chan, W. H.; Lee, Albert W. M. Chiral sulfonamide as a Brønsted acid organocatalyst for asymmetric Friedel-Crafts alkylation of indoles with imines. J. Org. Chem., 2011, 76, 7141-7147.
44. Feng, J.; Yan, W.; Wang, D.; Li, P.; Sun, Q.; Wang, R. The highly enantiose-lective addition of indoles and pyrroles to isatins-derived N-Boc ketimines catalyzed by chiral phosphoric acids. Chem. Commun., 2012, 48, 8003-8005.
45. Duce, S.; Pesciaioli, F.; Gramigna, L.; Bernardi, L.; Mazzanti, A.; Ricci, A.; Bartoli, G.; Bencivenni, G. An easy entry to optically active spiroindolinones: Chiral Brønsted acid-catalysed Pictet-Spengler reactions of isatins. Adv. Synth. Catal., 2011, 353, 860-864.
46. Wu, K.; Jiang, Y. J.; Fan, Y. S.; Sha, D.; Zhang, S. Double axially chiral bisphosphorylimides catalyzed highly enantioselective and efficient Friedel-Crafts reaction of indoles with imines. Chem. Eur. J., 2013, 19, 474-478.
47. Terada, M.; Sorimachi, K. Enantioselective Friedel-Crafts reaction of electron-rich alkenes catalyzed by chiral Brønsted acid. J. Am. Chem. Soc., 2007, 129, 292-293.
48. Kawasak, T.; Higuchi, K. Simple indole alkaloids and those with a nonrearranged monoterpenoid unit. Nat. Prod. Rep., 2005, 22, 761-793.
49. Ishikura, M.; Yamada, K.; Abe, T. Simple indole alkaloids and those with a nonrearranged monoterpenoid unit. Nat. Prod. Rep., 2010, 27, 1630-1680.
50. Hong, L.; Sun, W.; Liu, C.; Wang, L.; Wang, R. Asymmetric organocatalytic N-alkylation of indole-2-carbaldehydes with α, ß-unsaturated aldehydes: One-pot synthesis of chiral pyrrolo[1, 2-a]indole-2-carbaldehydes. Chem. Eur. J., 2010, 16, 440-444.
51. Cai, Q.; Zheng, C.; You, S. L. Enantioselective intramolecular aza-Michael additions of indoles catalyzed by chiral phosphoric acids. Angew. Chem. Int. Ed., 2010, 49, 8666-8669.
52. Cai, Q.; Zhao, Z. A.; You, S. L. Asymmetric construction of polycyclic indoles through olefin cross-metathesis/intramolecular Friedel-Crafts alkyl-ation under sequential catalysis. Angew. Chem. Int. Ed., 2009, 48, 7428-7431.
53. Franzén, J.; Fisher, A. Asymmetric alkaloid synthesis: A one-pot organocatalytic reaction to quinolizidine derivatives. Angew. Chem. Int. Ed., 2009, 48, 787-791.
54. Zhang, J. W.; Cai, Q.; Shi, X. X.; Zhang, W.; You, S. L. Enantioselective synthesis of tetrahydropyrano[3, 4-b]indoles catalyzed by chiral N-triflyl phosphoramide via intramolecular Friedel-Crafts alkylation reaction. Synlett., 2011, (9), 1239-1242.
55. Li, C. F.; Liu, H.; Liao, J.; Cao, Y. J.; Liu, X. P.; Xiao, W. J. Enantioselective organocatalytic intramolecular ring-closing Friedel-Crafts-type alkylation of indoles. Org. Lett., 2007, 9, 1847-1850.
56. Klausen, R. S.; Jacobsen, E. N. Weak Brønsted acid-thiourea co-catalysis: Enantioselective, catalytic Protio-Pictet-Spengler reactions. Org. Lett., 2009, II, 887-890.
57. Mergott, D. J.; Zuend, S. J.; Jacobsen, E. N. Catalytic asymmetric total synthesis of (+)-yohimbine. Org. Lett., 2008, 10, 745-748.
58. Sewgobind, N. V.; Wanner, M. J.; Ingemann, S.; de Gelder, R.; van Maarsev-een, J. H.; Hiemstra, H. Enantioselective BINOL-phosphoric acid catalyzed Pictet-Spengler reactions of N-benzyltryptamine. J. Org. Chem., 2008, 73, 6405-6408.
59. Raheem, I. T.; Thiara, P. S.; Peterson, E. M.; Jacobsen, E. N. Enantioselective Pictet-Spengler-type cyclizations of hydroxylactams: H-bond donor catalysis by anion binding. J. Am. Chem. Soc., 2007, 129, 13404-13405.
60. Muratore, M. E.; Holloway, C. A.; Pilling, A. W.; Storer, R. I.; Trevitt, G.; Dixon, D. J. Enantioselective Brønsted acid-catalyzed N-acyliminium cycli-zation cascades. J. Am. Chem. Soc., 2009, 131, 10796-10797.
61. Cheng, D. J.; Wu, H. B.; Tian, S. K. Catalytic asymmetric Pictet-Spengler-type-reaction for the synthesis of optically active indolo[3, 4-cd][1]benzazepines. Org. Lett., 2011, 13, 5636-5639.
62. Bartoli, G.; Bencivenni, G.; Dalpozzo, R. Organocatalytic strategies for the asymmetric functionalization of indoles. Chem. Soc. Rev., 2010, 39, 4449-4465.
63. You, S. L.; Cai, Q.; Zeng, M. Chiral Brønsted acid catalyzed Friedel-Crafts alkylation reactions. Chem. Soc. Rev., 2009, 38, 2190-2201.
64. Bandini, M.; Eichholzer, A. Catalytic functionalization of indoles in a new dimension. Angew. Chem. Int. Ed., 2009, 48, 9608-9644.
65. de Sa Alves, F. R.; Barreiro, E. J.; Fraga, C. A. M. From nature to drug discovery: The indole scaffold as a 'privileged structure'. Mini-Rev. Med. Chem., 2009, 9, 782-793.
66. Courant, T.; Kumarn, S.; He, L.; Retailleau, P.; Masson, G. Chiral phosphoric acid-catalyzed enantioselective aza-Friedel-Crafts alkylation of indoles with γ-hydroxy-γ-lactams. Adv. Synth Catal., 2013, 355, 836-840.
67. Bandini, M.; Tragni, M. π-Activated alcohols: An emerging class of alkylating agents for catalytic Friedel-Crafts reactions. Org. Biomol. Chem., 2009, 7, 1501-1507.
68. Liu, H.; Dagousset, G.; Masson, G.; Retailleau, P.; Zhu, J. Chiral Brønsted acid-catalyzed enantioselective three-component Povarov reaction. J. Am. Chem. Soc., 2009, 131, 4598-4599.
69. Cheng, X.; Vellalath, S.; Goddard, R.; List, B. Direct catalytic asymmetric synthesis of cyclic aminals from aldehydes. J. Am. Chem. Soc., 2008, 130, 15786-15787.
70. Hu, W.; Xu, X.; Zhou, J.; Liu, W. J.; Huang, H.; Hu, J.; Yang, L.; Gong, L. Z. Cooperative catalysis with chiral Brønsted acid-Rh2(OAc)4: Highly enanti-oselective three-component reactions of diazo compounds with alcohols and imines. J. Am. Chem. Soc., 2008, 130, 7782-7783.
71. Enders, D.; Narine, A. A.; Toulgoat, F.; Bisschops, T. Asymmetric Brønsted acid catalyzed isoindoline synthesis: Enhancement of enantiomeric ratio by stereoablative kinetic resolution. Angew. Chem. Int. Ed., 2008, 47, 5661-5665.
72. Kang, Q.; Zhao, Z. A.; You, S. L. Enantioselective synthesis of (3-indolyl)glycine derivatives via asymmetric Friedel-Crafts reaction between indoles and glyoxylate imines. Tetrahedron, 2009, 65, 1603-1607.
73. Sun, F. L.; Zeng, M.; Gu, Q.; You, S. L. Enantioselective synthesis of fluorene derivatives by chiral phosphoric acid-catalyzed tandem double Friedel-Crafts reaction. Chem. Eur. J., 2009, 15, 8709-8712.
74. Wong, W. Y. Metallated molecular materials of fluorene derivatives and their analogues. Coord. Chem. Rev., 2005, 249, 971-997.
75. Li, G.; Wang, E.; Chen, H.; Li, H.; Liu, Y.; Wang, P. G. A general and efficient synthesis of substituted fluorenes and heterocycle-fused indenes containing thiophene or indole rings utilizing a Suzuki-Miyaura coupling and acid-catalyzed Friedel-Crafts reactions as key steps. Tetrahedron, 2008, 64, 9033-9043.
76. Fuchibe, K.; Akiyama, T. Low-valent niobium-mediated double activation of C-F/C-H bonds: Fluorene synthesis from o-arylated α, α, α-trifluorotoluene derivatives. J. Am. Chem. Soc., 2006, 128, 1434-1435.
77. Tang, H. Y.; Lu, A. D.; Zhou, Z. H.; Zhao, G. F.; He, L. N.; Tang, C. C. Chiral phosphoric acid catalyzed asymmetric Friedel-Crafts alkylation of indoles with simple α, ß-unsaturated aromatic ketones Eur. J. Org. Chem., 2008, (8), 1406-1410.
78. Scettri, A.; Villano, R.; Acocella, M. R. Asymmetric Friedel-Crafts alkylation of indole with chalcones catalyzed by chiral phosphoric acids. Molecules, 2009, 14, 3030-3036.
79. Rueping, M.; Nachtsheim, B. J.; Moreth, S. A.; Bolte, M. Asymmetric Brønsted acid catalysis: enantioselective nucleophilic substitutions and 1, 4-additions. Angew. Chem. Int. Ed., 2008, 47, 593-596.
80. Sakamoto, T.; Itoh, J.; Mori, K. Akiyama, T. Chiral Brønsted acid catalyzed asymmetric Friedel-Crafts alkylation reaction of indoles with α, ß-unsaturated ketones: Short access to optically active 2-and 3-substituted indole derivatives. Org. Biomol. Chem., 2010, 8, 5448-5454.
81. Jandu, K. S.; Barrett, V.; Brockwell, M.; Cambridge, D.; Farrant, D. R.; Foster, C.; Giles, H.; Glen, R. C.; Hill, A. P.; Hobbs, H.; Honey, A.; Martin, G. M.; Salmon, J.; Smith, S.; Woollard, P.; Selwood, D. L. Discovery of 4-[3-(trans-3-dimethylaminocyclobutyl)-1H-indol-5-ylmethyl]-(4S)-oxazolidin-2-one (4991W93), a 5HT1B/1D receptor partial agonist and a potent inhibitor of electrically induced plasma extravasation. J. Med. Chem., 2001, 44, 681-693.
82. Jørgensen, K. A. Asymmetric Friedel-Crafts reactions: Catalytic enantioselective addition of aromatic and heteroaromatic C-H bonds to activated alkenes, carbonyl compounds, and imines. Synthesis, 2003, (7), 1117-1125.
83. Bandini, M.; Melloni, A.; Umani-Ronchi, A. New catalytic approaches in the stereoselective Friedel-Crafts alkylation reaction. Angew. Chem. Int. Ed., 2004, 43, 550-556.
84. Tsogoeva, S. B. Recent advances in asymmetric organocatalytic 1, 4-conjugate additions. Eur. J. Org. Chem., 2007, (11), 1701-1716.
85. Singh, P. K.; Bisai, A.; Singh, V. K. Enantioselective Friedel-Crafts alkylation of indoles with nitroalkenes catalyzed by a bis(oxazoline)-Cu(II) complex. Tetrahedron Lett., 2007, 48, 1127-1129.
86. Jia, Y. X.; Zhu, S. F.; Yang, Y.; Zhou, Q. L. Asymmetric Friedel-Crafts alkyla-tions of indoles with nitroalkenes catalyzed by Zn(II)-bisoxazoline complexes. J. Org. Chem., 2006, 71, 75-80.
87. Bandini, M.; Garelli, A.; Rovinetti, M.; Tommasi, S.; Umani-Ronchi, A. Catalytic enantioselective addition of indoles to arylnitroalkenes: An effective route to enantiomerically enriched tryptamine. Chirality, 2005, 17, 522-529.
88. Zhuang, W.; Hazell, R. Z.; Jørgensen, K. A. Enantioselective Friedel-Crafts type addition of indoles to nitro-olefins using a chiral hydrogen-bonding catalyst-synthesis of optically active tetrahydro-β-carbolines. Org. Biomol. Chem., 2005, 3, 2566-2571.
89. Itoh, J.; Fuchibe, K.; Akiyama, T. Chiral phosphoric acid catalyzed enantioselective Friedel-Crafts alkylation of indoles with nitroalkenes: Cooperative effect of 3 A molecular sieves. Angew. Chem. Int. Ed., 2008, 47, 4016-4018.
90. Akiyama, T.; Morita, H.; Itoh, J.; Fuchibe, K. Chiral Brønsted acid catalyzed enantioselective hydrophosphonylation of imines: asymmetric synthesis of α-amino phosphonates. Org. Lett., 2005, 7, 2583-2585.
91. Yamanaka, M.; Itoh, J.; Fuchibe, K.; Akiyama, T. Chiral Brønsted acid catalyzed enantioselective Mannich-type reaction. J. Am. Chem. Soc., 2007, 129, 6756-6764.
92. Safe, S.; Papineni, S.; Chintharlapalli, S. Cancer chemotherapy with indole-3-carbinol, bis(3'-indolyl)methane and synthetic analogs. Cancer Lett., 2008, 269, 326-328.
93. Chintharlapalli, S.; Papineni, S.; Safe, S. 1, 1-Bis(3'-Indolyl)-1-(p-substitutedphenyl)methanes inhibit growth, induce apoptosis, and decrease the androgen receptor in LNCaP prostate cancer cells through peroxisome proliferator-activated receptor γ-independent pathways. Mol. Pharmacol., 2007, 71, 558-569.
94. Zhuo, M. H.; Jiang, Y. J.; Fan, Y. S.; Gao, Y.; Liu, S.; Zhang, S. Enantioselec-tive synthesis of triarylmethanes by chiral imidodiphosphoric acids catalyzed Friedel-Crafts reactions. Org. Lett., 2014, 16, 1096-1099.
95. Qi, S.; Liu, C. Y.; Ding, J. Y.; Han, F. S. Chiral phosphoramide-catalyzed enantioselective synthesis of 2, 3'-diindolylarylmethanes from indol-2-yl carbinols and indoles. Chem. Commun., 2014, 50, 8605-8608.
96. Chen, Y.; Xie, Z. Research progress in Friedel-Crafts reaction of indoles and imines. Chin. J. Org. Chem., 2012, 32, 462-471.