Synlett 2005(17): 2653-2657  
DOI: 10.1055/s-2005-917111
LETTER
© Georg Thieme Verlag Stuttgart · New York

An Expeditious Approach to Quinolines via Friedländer Synthesis Catalyzed by FeCl3 or Mg(ClO4)2

Jie Wu*a,b, Liang Zhanga, Tian-Ning Diaoa
a Department of Chemistry, Fudan University, 220 Handan Road, Shanghai 200433, P. R. of China
Fax: +86(21)65102412; e-Mail: jie_wu@fudan.edu.cn;
b State Key Laboratory of Organometallic Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, 354 Fenglin Road, Shanghai 200032, P. R. of China
Further Information

Publication History

Received 14 August 2005
Publication Date:
05 October 2005 (online)

Abstract

A mild and efficient route for the synthesis of quinolines and polycyclic quinolines utilizing FeCl3 or Mg(ClO4)2 as a novel catalyst via Friedländer annulation was described.

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General Procedure.
A mixture of the 2-aminoaryl ketone (0.5 mmol), α-methylene ketone (1.5 equiv) and FeCl3 or Mg(ClO4)2 (10 mol%) in EtOH (5 mL) was stirred at r.t. After completion of the reaction as indicated by TLC, the reaction mixture was quenched with H2O (15 mL) and extracted with EtOAc (2 × 10 mL). Evaporation of the solvent followed by purification on silica gel afforded pure quinoline (all the products are known compounds; the characterizations of these compounds are identical with the literature reports).
Ethyl 2-Methyl-4-phenylquinoline-3-carboxylate ( 3a) [9i]

1H NMR (500 MHz, CDCl3): δ = 0.94 (t, J = 7.1 Hz, 3 H), 2.79 (s, 3 H), 4.04-4.09 (m, 2 H), 7.36-7.72 (m, 8 H), 8.07 (d, J = 8.4 Hz, 1 H) ppm.
1-(2-Methyl-4-phenylquinolin-3-yl)ethanone ( 3b) [9i]

1H NMR (400 MHz, CDCl3): δ = 2.00 (s, 3 H), 2.71 (s, 3 H), 7.36-8.11 (m, 9 H) ppm.
9-Phenyl-2,3-dihydro-1 H -cyclopenta[ b ]quinoline ( 3c) [9i]

1H NMR (400 MHz, CDCl3): δ = 2.16-2.19 (m, 2 H), 2.91 (t, J = 7.3 Hz, 2 H), 3.25 (t, J = 7.6 Hz, 2 H), 7.36-8.10 (m, 9 H) ppm.
9-Phenyl-3,4-dihydroacridin-1 (2 H )-one ( 3d) [9e]

1H NMR (400 MHz, CDCl3): δ = 2.24-2.27 (m, 2 H), 2.69 (t, J = 6.6 Hz, 2 H), 3.36 (t, J = 6.4 Hz, 2 H), 7.17-7.19 (m, 2 H), 7.40-7.46 (m, 6 H), 8.05 (d, J = 8.7 Hz, 1 H) ppm.
Ethyl 2,4-Dimethylquinoline-3-carboxylate ( 3e) [9i]

1H NMR (500 MHz, CDCl3): δ = 1.41 (t, J = 7.1 Hz, 3 H), 2.61 (s, 3 H), 2.71 (s, 3 H), 4.45-4.49 (m, 2 H), 7.46 (t, J = 7.6 Hz, 1 H), 7.66 (t, J = 7.6 Hz, 1 H), 7.91 (d, J = 8.4 Hz, 1 H), 7.99 (d, J = 8.4 Hz, 1 H) ppm.
1-(2,4-Dimethylquinolin-3-yl)ethanone ( 3f) [9j]

1H NMR (500 MHz, CDCl3): δ = 2.54 (d, J = 12.3 Hz, 6 H), 2.62 (s, 3 H), 7.49 (t, J = 7.6 Hz, 1 H), 7.66 (t, J = 7.6 Hz, 1 H), 7.91 (d, J = 8.3 Hz, 1 H), 7.99 (d, J = 8.4 Hz, 1 H) ppm.
Ethyl 6-Chloro-2-methyl-4-phenylquinoline-3-carboxylate ( 3g) [9j]

1H NMR (500 MHz, CDCl3): δ = 0.94 (t, J = 7.1 Hz, 3 H), 2.77 (s, 3 H), 4.04-4.09 (m, 2 H), 7.34-7.66 (m, 7 H), 8.00 (d, J = 9.0 Hz, 1 H) ppm.
1-(6-Chloro-2-methyl-4-phenylquinolin-3-yl)ethanone ( 3h) [9i]

1H NMR (500 MHz, CDCl3): δ = 2.00 (s, 3 H), 2.68 (s, 3 H), 7.33-7.35 (m, 2 H), 7.53-7.66 (m, 5 H), 8.00 (d, J = 8.9 Hz, 1 H) ppm.
1-[6-Chloro-4-(2-chlorophenyl)-2-methylquinolin-3-yl]ethanone ( 3i) [9f]

1H NMR (400 MHz, CDCl3): δ = 2.15 (s, 3 H), 2.71 (s, 3 H), 7.23-7.28 (m, 2 H), 7.40-7.67 (m, 4 H), 8.01 (d, J = 9.2 Hz, 1 H) ppm.
7-Chloro-9-phenyl-2,3-dihydro-1 H -cyclo-penta[ b ]quinoline ( 3j) [9i]

1H NMR (400 MHz, CDCl3): δ = 2.14-2.18 (m, 2 H), 2.89 (t, J = 7.3 Hz, 2 H), 3.21 (t, J = 7.8 Hz, 2 H), 7.32-7.34 (m, 2 H), 7.52-7.53 (m, 5 H), 7.98 (d, J = 9.2 Hz, 1 H) ppm.