Download PDF
Synlett 2023; 34(06): 651-656
DOI: 10.1055/s-0042-1751358
cluster
Chemical Synthesis and Catalysis in India

Concise Synthesis of N-Aryl Tetrahydroquinolines via a One-Pot Sequential Reduction of Quinoline/Chan–Evans–Lam Coupling ­Reaction

Dipanjan Bhattacharyya
a   Department of Chemistry, Indian Institute of Technology Guwahati, Guwahati - 781039, Assam, India
,
Siddhartha Kumar Senapati
a   Department of Chemistry, Indian Institute of Technology Guwahati, Guwahati - 781039, Assam, India
,
Animesh Das  ∗
a   Department of Chemistry, Indian Institute of Technology Guwahati, Guwahati - 781039, Assam, India
b   Centre for Sustainable Polymers, Indian Institute of Technology Guwahati, Guwahati - 781039, Assam, India
› Author AffiliationsA.D. gratefully acknowledges the Science and Engineering Research Board (SERB), the Department of Science and Technology (DST) (ECR/2016/001459), and DST-INSPIRE (IFA-14-CH-135) for financial support. D.B. and S.K.S. would like to thank the Indian Institute of Technology Guwahati (IITG) for their research fellowships.
› Further Information
    Permissions and Reprints All articles of this category


Abstract

A boronic acid catalyzed one-pot reduction of quinolines with Hantzsch ester followed by N-arylation via external base-free Chan–Evans–Lam coupling has been demonstrated. This step-economical synthesis of N-aryl tetrahydroquinolines has been accomplished from readily available quinoline, Hantzsch ester, and arylboronic acid under mild reaction conditions. The dual role of boronic acid as a catalyst (in the reduction of quinolines) and a reagent (in the N-arylation) has been realized for the first time. The use of an inexpensive N-arylation protocol, aerobic reaction conditions, and functional group diversity are important practical features.

Key words

N-aryl tetrahydroquinolines - dual role boronic acid - Chan–Evans–Lam coupling - N-arylation - one-pot reaction

Supporting Information

    Supporting information for this article is available online at https://doi.org/10.1055/s-0042-1751358.
  • Supporting Information


Publication History

Received: 27 May 2022

Accepted after revision: 19 July 2022

Article published online:
19 August 2022

© 2022. Thieme. All rights reserved

Georg Thieme Verlag KG
Rüdigerstraße 14, 70469 Stuttgart, Germany

 

  • References and Notes

    • 1a Muthukrishnan I, Sridharan V, Menéndez JC. Chem. Rev. 2019; 119: 5057
      CrossrefPubMed
    • 1b Katritzky AR, Rachwal S, Rachwal B. Tetrahedron 1996; 52: 15031
      Crossref
    • 1c Sridharan V, Suryavanshi PA, Menéndez JC. Chem. Rev. 2011; 111: 7157
      CrossrefPubMed
    • 2a Zhang C, Westaway SM, Speake JD, Bishop MJ, Goetz AS, Carballo LH, Hu M, Epperly AH. Bioorg. Med. Chem. Lett. 2011; 21: 670
      CrossrefPubMed
    • 2b Wang S.-B, Wang X.-F, Qin B, Ohkoshi E, Hsieh K.-Y, Hamel E, Cui M.-T, Zhu D.-Q, Goto M, Morris-Natschke SL, Lee K.-H, Xie L. Bioorg. Med. Chem. 2015; 23: 5740
      CrossrefPubMed
    • 2c Yu J, Zhang L, Yan G, Zhou P, Cao C, Zhou F, Li X, Chen Y. Eur. J. Med. Chem. 2019; 171: 265
      CrossrefPubMed
    • 2d Liu X, Chen P, Li X, Ba M, Jiao X, Guo Y, Xie P. Bioorg. Med. Chem. Lett. 2018; 28: 1699
      CrossrefPubMed
  • 3 Sano H, Noguchi T, Tanatani A, Hashimoto Y, Miyachi H. Bioorg. Med. Chem. 2005; 13: 3079
    CrossrefPubMed
  • 4 Getautis V, Stumbraite J, Gaidelis V, Jankauskas V, Kliucius A, Paulauskas V. Synth. Met. 2007; 157: 35
    CrossrefPubMed
  • 5 Warsitz M, Doye S. Eur. J. Org. Chem. 2020; 6997
    CrossrefPubMed
    • 6a Joe CL, Doyle AG. Angew. Chem. Int. Ed. 2016; 55: 4040
      CrossrefPubMed
    • 6b Hernandez-Perez AC, Collins SK. Angew. Chem. Int. Ed. 2013; 52: 12696
      CrossrefPubMed
    • 6c Buckley BR, Christie SD. R, Elsegood MR. J, Gillings CM, Bulman Page PC. B, Pardoe WJ. M. Synlett 2010; 939
    • 6d Meneyrol J, Helissey P, Tratrat C, Giorgi-Renault S, Husson H.-P. Synth. Commun. 2001; 31: 987
      Crossref
    • 6e Guari Y, van Es DS, Reek JN. H, Kamer PC. J, van Leeuwen PW. N. M. Tetrahedron Lett. 1999; 40: 3789
      Crossref
  • 7 Yoshida Y, Otsuka S, Nogi K, Yorimitsu H. Org. Lett. 2018; 20: 1134
    CrossrefPubMed
  • 8 Gao K, Yorimitsu H, Osuka A. Eur. J. Org. Chem. 2015; 2678
    CrossrefPubMed
  • 9 Geier SJ, Chase PA, Stephan DW. Chem. Commun. 2010; 46: 4884
    CrossrefPubMed
    • 10a Adhikari P, Bhattacharyya D, Nandi S, Kancharla P, Das A. Org. Lett. 2021; 23: 2437
      CrossrefPubMed
    • 10b Bhattacharyya D, Nandi S, Adhikari P, Sarmah BK, Konwar M, Das A. Org. Biomol. Chem. 2020; 18: 1214
      CrossrefPubMed
  • 11 West MJ, Fyfe JW. B, Vantourout JC, Watson AJ. B. Chem. Rev. 2019; 119: 12491
    CrossrefPubMed
  • 12 The possible reason for high loading copper salts is inhibiting the regeneration of reduced copper(I) or copper(0) species under the reaction conditions.§#ITL#
  • 13 Synthesis of N-Aryl Tetrahydroquinoline Derivatives; General Procedure:A mixture of substituted quinoline (1 mmol, 1 equiv), Hantzsch ester (2.2 mmol, 2.2 equiv), arylboronic acid (0.3 mmol, 0.3 equiv) and DCE (2 mL) was added into a reaction tube (25 mL) equipped with stirring bar. The reaction tube was properly closed and placed in a preheated oil bath at 60 °C with continuous stirring for 7 h. To the resulting mixture, arylboronic acid (0.7 mmol, 0.7 equiv), copper(II) acetate monohydrate (0.7 mmol, 0.7 equiv) and 4 Å MS was added and the mixture was stirred at room temperature for 40 h. After completion of the reaction, the reaction mixture was passed through a bed of Celite, the filtrate was collected and concentrated under reduced pressure. The crude reaction mixture was purified by column chromatography over silica gel using petroleum ether or ethyl acetate/petroleum ether mixture as eluent.1-Phenyl-1,2,3,4-tetrahydroquinoline (3a)By following the general procedure, the title compound 3a was isolated as colourless liquid using silica gel column chromatography with petroleum ether/ethyl acetate (v/v = 100/1, Rf = 0.5) in 94% yield (0.196 g). 1H NMR (600 MHz, CDCl3): δ = 7.34 (t, J = 8.3 Hz, 2 H), 7.24 (d, J = 7.5 Hz, 2 H), 7.09 (t, J = 7.3 Hz, 1 H), 7.05 (d, J = 7.3 Hz, 1 H), 6.93 (t, J = 7.8 Hz, 1 H), 6.75 (d, J = 8.2 Hz, 1 H), 6.70 (t, J = 7.3 Hz, 1 H), 3.63 (t, J = 5.6 Hz, 2 H), 2.85 (t, J = 6.4 Hz, 2 H), 2.07–2.03 (m, 2 H). 13C NMR (151 MHz, CDCl3): δ = 148.5, 144.5, 129.5, 126.5, 124.8, 124.7, 123.7, 118.4, 115.9, 51.0, 27.9, 22.9.1-(p-Tolyl)-1,2,3,4-tetrahydroquinoline (3b)By following the general procedure, the title compound 3b was isolated as colourless liquid using silica gel column chromatography with petroleum ether/ethyl acetate (v/v = 100/1, Rf = 0.5) in 94% yield (0.209 g). 1H NMR (400 MHz, CDCl3): δ = 7.20–7.11 (m, 4 H), 7.03 (d, J = 7.2 Hz, 1 H), 6.91 (t, J = 8.1 Hz, 1 H), 6.69–6.63 (m, 2 H), 3.62 (t, J = 5.6 Hz, 2 H), 2.88 (t, J = 6.4 Hz, 2 H), 2.37 (s, 3 H), 2.10–2.05 (m, 2 H). 13C NMR (101 MHz, CDCl3): δ = 146.0, 145.0, 133.8, 130.2, 129.5, 126.5, 125.4, 124.0, 117.8, 115.3, 51.3, 28.0, 22.7, 21.0. HRMS (ESI): m/z [M + H]+ calcd for C16H18N: 224.1434; found: 224.1439.1-(4-Methoxyphenyl)-1,2,3,4-tetrahydroquinoline (3c)By following the general procedure, the title compound 3c was isolated as colourless liquid using silica gel column chromatography with petroleum ether/ethyl acetate (v/v = 100/1, Rf = 0.5) in 96% yield (0.229 g). 1H NMR (600 MHz, CDCl3): δ = 7.18–7.16 (m, 2 H), 7.02 (d, J = 7.3 Hz, 1 H), 7.01–6.87 (m, 3 H), 6.63 (t, J = 7.3 Hz, 1 H), 6.47 (d, J = 8.2 Hz, 1 H), 3.83 (s, 3 H), 3.56 (t, J = 5.6 Hz, 2 H), 2.87 (t, J = 6.4 Hz, 2 H), 2.08–2.05 (m, 2 H). 13C NMR (151 MHz, CDCl3): δ = 156.9, 145.7, 141.5, 129.4, 127.8, 126.6, 123.1, 117.3, 115.0, 114.4, 55.6, 51.8, 28.0, 22.6. HRMS (ESI): m/z [M + H]+ calcd for C16H18N: 240.1383; found: 240.1384.1-(4-Bromophenyl)-1,2,3,4-tetrahydroquinoline (3d)By following the general procedure, the title compound 3d was isolated as colourless liquid using silica gel column chromatography with petroleum ether/ethyl acetate (v/v = 50/1, Rf = 0.5) in 86% yield (0.247 g). 1H NMR (400 MHz, CDCl3): δ = 7.44–7.41 (m, 2 H), 7.13–7.07 (m, 2 H), 7.05 (d, J = 8.0 Hz, 1 H), 6.94 (t, J = 8.0 Hz, 1 H), 6.80–6.71 (m, 2 H), 3.60 (t, J = 5.7 Hz, 2 H), 2.84 (t, J = 6.4 Hz, 2 H), 2.06–2.00 (m, 2 H). 13C NMR (101 MHz, CDCl3): δ = 147.6, 143.9, 132.4, 129.6, 126.5, 125.8, 125.6, 119.2, 116.4, 115.8, 50.8, 27.8, 22.9. HRMS (ESI): m/z [M + H]+ calcd for C15H15BrN: 288.0383; found: 288.0379.1-(4-Chlorophenyl)-1,2,3,4-tetrahydroquinoline (3e)By following the general procedure, the title compound 3e was isolated as colourless liquid using silica gel column chromatography with petroleum ether/ethyl acetate (v/v= 50/1, Rf = 0.5) in 75% yield (0.182 g). 1H NMR (600 MHz, CDCl3): δ = 7.29 (d, J = 8.8 Hz, 1 H), 7.16 (d, J = 8.8 Hz, 1 H), 7.05 (d, J = 7.3 Hz, 1 H), 6.94 (t, J = 7.9 Hz, 1 H), 6.75 ‒ 6.72 (m, 2 H), 3.59 (t, J = 5.7 Hz, 2 H), 2.84 (t, J = 6.4 Hz, 2 H), 2.05–2.01 (m, 2 H). 13C NMR (151 MHz, CDCl3): δ = 147.1, 144.0, 129.6, 129.5, 128.4, 126.6, 125.6, 125.3, 119.0, 116.2, 50.9, 27.8, 22.8. HRMS (ESI): m/z [M + H]+ calcd for C15H15ClN: 244.0888; found: 244.0884.1-(4-Fluorophenyl)-1,2,3,4-tetrahydroquinoline (3f)By following the general procedure, the title compound 3f was isolated as colourless liquid using silica gel column chromatography with petroleum ether/ethyl acetate (v/v= 50/1, Rf = 0.5) in 60% yield (0.136 g). 1H NMR (600 MHz, CDCl3): δ = 7.22–7.19 (m, 2 H), 7.09–7.03 (m, 3 H), 6.93 (t, J = 7.5 Hz, 1 H), 6.69 (t, J = 7.3 Hz, 1 H), 6.56 (d, J = 8.2 Hz, 1 H), 3.58 (t, J = 5.6 Hz, 2 H), 2.88 (t, J = 6.4 Hz, 2 H), 2.09–2.04 (m, 2 H). 13C NMR (126 MHz, CDCl3): δ = 160.7, 158.7, 145.0, 144.6, 144.6, 129.6, 127.4, 127.4, 126.6, 123.9, 118.1, 116.4, 116.3, 115.1, 51.6, 27.9, 22.7. 19F NMR (377 MHz, CDCl3): δ = –118.31. HRMS (ESI): m/z [M + H]+ calcd for C15H15FN: 228.1184; found: 228.1176.1-(3-(Trifluoromethyl)phenyl)-1,2,3,4-tetrahydroquinoline (3g)By following the general procedure, the title compound 3g was isolated as colourless liquid using silica gel column chromatography with petroleum ether/thyl acetate (v/v= 50/1, Rf = 0.5) in 85% yield (0.235 g). 1H NMR (400 MHz, CDCl3): δ = 7.45 (brs, 1 H), 7.40–7.39 (m, 2 H), 7.27–7.26 (m, 1 H), 7.08 (d, J = 7.4 Hz, 1 H), 6.98 (t, J = 8.1 Hz, 1 H), 6.86 (d, J = 8.0 Hz, 1 H), 6.81 (t, J = 7.3 Hz, 1 H), 3.65 (t, J = 5.6 Hz, 2 H), 2.83 (t, J = 6.4 Hz, 2 H), 2.07–2.01 (m, 2 H). 13C NMR (101 MHz, CDCl3): δ = 149.0, 143.3, 129.8, 129.6, 126.6, 126.4, 119.9, 119.8, 119.3, 116.9, 50.5, 27.7, 23.1. 19F NMR (377 MHz, CDCl3): δ = –62.71.1-(3-Chlorophenyl)-1,2,3,4-tetrahydroquinoline (3h)By following the general procedure, the title compound 3h was isolated as colourless liquid using silica gel column chromatography with petroleum ether/ethyl acetate (v/v= 50/1, Rf = 0.5) in 86% yield (0.209 g). 1H NMR (400 MHz, CDCl3): δ = 7.24–7.19 (m, 2 H), 7.11–7.05 (m, 2 H), 7.01–6.95 (m, 2 H), 6.86 (d, J = 8.1 Hz, 1 H), 6.78–6.75 (m, 1 H), 3.60 (t, J = 5.6 Hz, 2 H), 2.81 (t, J = 6.4 Hz, 2 H), 2.07–1.98 (m, 2 H). 13C NMR (101 MHz, CDCl3): δ = 149.8, 143.5, 134.9, 130.3, 129.5, 126.6, 126.2, 123.4, 122.9, 121.6, 119.6, 117.0, 50.5, 27.7, 23.0. HRMS (ESI): m/z [M + H]+ calcd for C15H15ClN: 244.0888; found: 244.0893.6-Methyl-1-phenyl-1,2,3,4-tetrahydroquinoline (3i)By following the general procedure, the title compound 3i was isolated as colourless liquid using silica gel column chromatography with petroleum ether/ethyl acetate (v/v = 100/1, Rf = 0.5) in 91% yield (0.203 g). 1H NMR (400 MHz, CDCl3): δ = 7.32–7.28 (m, 2 H), 7.22–7.19 (m, 2 H), 7.03 (t, J = 7.3 Hz, 1 H), 6.87 (brs, 1 H), 6.77–6.71 (m, 2 H), 3.60 (t, J = 5.6 Hz, 2 H), 2.79 (t, J = 6.4 Hz, 2 H), 2.23 (s, 3 H), 2.03–1.97 (m, 2 H). 13C NMR (101 MHz, CDCl3): δ = 148.9, 141.9, 130.0, 129.4, 128.0, 127.0, 125.3, 123.9, 123.0, 116.6, 50.8, 27.8, 23.0, 20.6. HRMS (ESI): m/z [M + H]+ calcd for C16H18N: 224.1434; found: 224.1431.6-Methoxy-1-phenyl-1,2,3,4-tetrahydroquinoline (3j)By following the general procedure, the title compound 3j was isolated as colourless liquid using silica gel column chromatography with petroleum ether/ethyl acetate (v/v = 100/1, Rf = 0.5) in 93% yield (0.222 g). 1H NMR (400 MHz, CDCl3): δ = 7.30–7.25 (m, 2 H), 7.17–7.15 (m, 2 H), 7.00–6.98 (m, 1 H), 6.83 (d, J = 8.9 Hz, 1 H), 6.65 (d, J = 3.0 Hz, 1 H), 6.57 (dd, J = 9.0, 3.0 Hz, 1 H), 3.75 (s, 3 H), 3.60 (t, J = 5.6 Hz, 2 H), 2.80 (t, J = 6.4 Hz, 2 H), 2.01–1.95 (m, 2 H). 13C NMR (101 MHz, CDCl3): δ = 153.1, 149.4, 137.9, 129.3, 127.7, 122.8, 122.2, 119.0, 114.4, 112.4, 55.8, 50.6, 28.0, 22.9. HRMS (ESI): m/z [M + H]+ calcd for C16H18N: 240.1383; found: 240.1388.6-Chloro-1-phenyl-1,2,3,4-tetrahydroquinoline (3k)By following the general procedure, the title compound 3k was isolated as colourless liquid using silica gel column chromatography with petroleum ether/ethyl acetate (v/v = 100/1, Rf = 0.5) in 88% yield (0.214 g). 1H NMR (400 MHz, CDCl3): δ = 7.35 (t, J = 8.0 Hz, 2 H), 7.20 (d, J = 7.8 Hz, 2 H), 7.11 (t, J = 7.3 Hz, 1 H), 7.01 (d, J = 2.2 Hz, 1 H), 6.86 (dd, J = 8.8, 2.4 Hz, 1 H), 6.64 (d, J = 8.8 Hz, 1 H), 3.60 (t, J = 5.6 Hz, 2 H), 2.82 (t, J = 6.5 Hz, 2 H), 2.06–2.00 (m, 2 H). 13C NMR (151 MHz, CDCl3): δ = 148.2, 143.2, 129.7, 129.0, 126.3, 126.2, 124.9, 124.1, 122.8, 117.0, 50.9, 27.8, 22.5. HRMS (ESI): m/z [M + H]+ calcd for C15H15ClN: 244.0888; found: 244.0895.4-Methyl-1-phenyl-1,2,3,4-tetrahydroquinoline (3l)By following the general procedure, the title compound 3l was isolated as colourless liquid using silica gel column chromatography with petroleum ether/ethyl acetate (v/v = 100/1, Rf = 0.5) in 90% yield (0.201 g). 1H NMR (600 MHz, CDCl3): δ = 7.35–7.32 (m, 2 H), 7.24–7.23 (m, 2 H), 7.15 (d, J = 7.5 Hz, 1 H), 7.10–7.07 (m, 1 H), 6.95–6.92 (m, 1 H), 6.77–6.73 (m, 2 H), 3.68–3.64 (m, 1 H), 3.61–3.58 (m, 1 H), 3.00–2.96 (m, 1 H), 2.15–2.09 (m, 1 H), 1.79–1.74 (m, 1 H), 1.36 (d, J = 7.0 Hz, 3 H). 13C NMR (151 MHz, CDCl3): δ = 148.5, 143.9, 130.1, 129.9, 129.5, 128.2, 126.5, 124.5, 123.6, 119.0, 118.5, 116.1, 47.9, 31.0, 30.6, 22.3. HRMS (ESI): m/z [M + H]+ calcd for C16H18N: 224.1434; found: 224.1433.3-Methyl-1-phenyl-1,2,3,4-tetrahydroquinoline (3m)By following the general procedure, the title compound 3m was isolated as colourless liquid using silica gel column chromatography with petroleum ether/ethyl acetate (v/v = 100/1, Rf = 0.5) in 83% yield (0.184 g). 1H NMR (600 MHz, CDCl3): δ = 7.35–7.32 (m, 2 H), 7.24 (d, J = 7.5 Hz, 1 H), 7.11–7.08 (m, 1 H), 7.04–7.01 (m, 2 H), 6.92 (t, J = 7.7 Hz, 1 H), 6.74 (d, J = 8.2 Hz, 1 H), 6.69 (t, J = 7.2 Hz, 1 H), 3.64–3.61 (m, 1 H), 3.24–3.21 (m, 1 H), 2.90–2.86 (m, 1 H), 2.55–2.50 (m, 1 H), 2.21–2.16 (m, 1 H), 1.06 (d, J = 6.6 Hz, 3 H). 13C NMR (151 MHz, CDCl3): δ = 148.4, 144.0, 129.9, 129.7, 129.5, 126.5, 125.0, 124.1, 123.9, 123.4, 119.0, 118.4, 115.4, 57.8, 36.2, 27.8, 19.1. HRMS (ESI): m/z [M + H]+ calcd for C16H18N: 224.1434; found: 224.1439.2-Methyl-1-phenyl-1,2,3,4-tetrahydroquinoline (3n)By following the general procedure, the title compound 3n was isolated as colourless liquid using silica gel column chromatography with petroleum ether/ethyl acetate (v/v = 100/1, Rf = 0.5) in 85% yield (0.189 g). 1H NMR (400 MHz, CDCl3): δ = 7.38–7.34 (m, 2 H), 7.24–7.21 (m, 2 H), 7.17–7.13 (m, 1 H), 7.04 (d, J = 7.4 Hz, 1 H), 6.91–6.87 (m, 1 H), 6.67–6.63 (m, 1 H), 6.51 (d, J = 8.2 Hz, 1 H), 3.93–3.96 (m, 1 H), 2.95–2.78 (m, 1 H), 2.87–2.77 (m, 1 H), 2.11–2.03 (m, 1 H), 1.88–1.81 (m, 1 H), 1.15 (d, J = 6.6 Hz, 3 H). 13C NMR (101 MHz, CDCl3): δ = 147.5, 144.3, 129.6, 129.3, 127.1, 126.5, 124.7, 123.2, 117.5, 115.9, 54.3, 28.5, 24.4, 19.9. HRMS (ESI): m/z [M + H]+ calcd for C16H18N: 224.1434; found: 224.1425.2-(4-Methoxyphenethyl)-1-phenyl-1,2,3,4-tetrahydroquinoli ne (3o)By following the general procedure, the title compound 3o was isolated as colourless liquid using silica gel column chromatography with petroleum ether/ethyl acetate (v/v = 50/1, Rf = 0.5) in 61% yield (0.21 g). 1H NMR (600 MHz, CDCl3): δ = 7.32–7.29 (m, 2 H), 7.17–7.15 (m, 2 H), 7.08–7.03 (m, 4 H), 6.95–6.92 (m, 1 H), 6.81–6.79 (m, 2 H), 6.75–6.71 (m, 2 H), 3.78 (s, 3 H), 2.93–2.87 (m, 1 H), 2.82–2.79 (m, 1 H), 2.72–2.68 (m, 1 H), 2.65–2.59 (m, 1 H), 2.07–2.01 (m, 1 H), 1.98–1.91 (m, 2 H), 1.84–1.78 (m, 1 H), 1.34–1.26 (m, 1 H). 13C NMR (126 MHz, CDCl3): δ = 157.9, 148.8, 143.5, 134.1, 129.45, 129.49, 129.3, 126.4, 125.3, 124.7, 123.5, 118.7, 118.4, 113.9, 58.8, 55.4, 34.1, 31.7, 24.6, 23.7. HRMS (ESI): m/z [M + H]+ calcd for C24H26NO: 344.2009; found: 344.2014.2-(4-Methoxyphenyl)-1-phenyl-1,2,3,4-tetrahydroquinoline (3p)By following the general procedure, the title compound 3p was isolated as colourless liquid using silica gel column chromatography with petroleum ether/ethylacetate (v/v = 50/1, Rf = 0.5) in 53% yield (0.167 g). 1H NMR (400 MHz, CDCl3): δ = 7.27–7.22 (m, 3 H), 7.21–7.16 (m, 4 H), 7.06–6.95 (m, 3 H), 6.86 (d, J = 8.0 Hz, 1 H), 6.81 (d, J = 8.6 Hz, 2 H), 6.71 (t, J = 7.3 Hz, 1 H), 4.89 (t, J = 4.2 Hz, 1 H), 3.77 (s, 3 H), 2.72–2.59 (m, 2 H), 2.34–2.28 (m, 1 H), 2.14–2.05 (m, 1 H). 13C NMR (101 MHz, CDCl3): δ = 158.5, 148.1, 144.0, 136.0, 129.4, 127.7, 126.7, 125.1, 124.1, 123.9, 118.1, 115.8, 113.9, 62.7, 55.3, 29.2, 23.9.1,1′-Diphenyl-1,1′,2,2′,3,3′,4,4′-octahydro-6,6′-biquinoline (4)The title compound 4 was isolated as brown oil using silica gel column chromatography with petroleum ether/ethyl acetate (v/v = 20:1, Rf = 0.50). Yield: 0.188 g (90%). 1H NMR (600 MHz, CDCl3): δ = 7.35 (t, J = 7.6 Hz, 4 H), 7.27–7.23 (m, 6 H), 7.13–7.07 (m, 4 H), 6.81 (d, J = 8.5 Hz, 2 H), 3.65 (t, J = 5.6 Hz, 4 H), 2.90 (t, J = 6.4 Hz, 4 H), 2.06 (p, J = 6.0 Hz, 4 H). 13C NMR (126 MHz, CDCl3): δ = 148.5, 143.1, 131.7, 129.5, 127.4, 125.0, 124.6, 124.5, 123.6, 116.3, 51.0, 28.1, 23.0. HRMS (ESI): m/z [M + H] + calcd for C30H29N2: 417.2331; found: 417.2337.1-Phenyl-2,3-dihydroquinolin-4(1H)-one (5)The title compound 5 was isolated as pale-yellow oil using silica gel column chromatography with petroleum ether/ethyl acetate (v/v = 20:1, Rf = 0.66); Yield: 0.124 g (56%). 1H NMR (500 MHz, CDCl3): δ = 7.95 (d, J = 7.8 Hz 1 H), 7.6–7.43 (m, 2 H), 7.29–7.24 (m, 3 H), 7.21 (m, 1 H), 6.78 (t, J = 7.8 Hz, 1 H), 6.63 (d, J = 8.5 Hz, 1 H), 3.91 (t, J = 6.8 Hz, 2 H), 2.84 (t, J = 6.8 Hz, 2 H). 13C NMR (126 MHz, CDCl3): δ = 193.5, 151.4, 146.1, 134.9, 130.1, 128.2, 126.2, 125.9, 115.7, 50.9, 38.5. HRMS (ESI): m/z [M + H]+ calcd for C15H14NO: 224.1070; found: 224.0973.
  • 14 Maddala S, Mallick S, Venkatakrishnan P. J. Org. Chem. 2017; 82: 8958
    CrossrefPubMed
  • 15 Vantourout JC, Miras HN, Isidro-Llobet A, Sproules S, Watson AJ. B. J. Am. Chem. Soc. 2017; 139: 4769
    CrossrefPubMed