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Synlett 2011(1): 104-110  
DOI: 10.1055/s-0030-1259105
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© Georg Thieme Verlag Stuttgart ˙ New York

Efficient One-Pot Synthesis of Substituted 4,7-Phenanthroline, Pyrano-[3,2-f]quinoline and Pyrano[3,2-g]quinoline Derivatives by Aza-Diels-Alder Reaction

K. C. Majumdar*, Sudipta Ponra, Debankan Ghosh, Abu Taher
Department of Chemistry, University of Kalyani, Kalyani 741235, West Bengal, India
e-Mail: kcm_ku@yahoo.co.in;
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Publication History

Received 15 August 2010
Publication Date:
10 December 2010 (online)

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Abstract

A mild and efficient method for the synthesis of py­rano[3,2-f]quinoline and 4,7-phenanthroline derivatives via three-component domino reaction of heterocyclic amines, aldehydes, and terminal alkyne using BF3˙OEt2 as Lewis acid catalyst is described. The features of this procedure are mild reaction conditions, good to high yields, and operational simplicity.

Key words

multicomponent reaction - BF3˙OEt2 - 4,7-phenanthroline - pyrano[3,2-f]quinoline - pyrano[3,2-g]quinoline - aromatic aldehyde - phenyl acetylene

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Synthesis of Compound 4a A mixture of the heterocyclic amine 1a (0.287 mmol) and aromatic aldehyde 2a (0.287 mmol) was stirred in toluene at r.t. for 10 min. After addition of 10 mol% BF3˙OEt2 (mol% calcd relative to the phenyl acetylene 3) phenyl acetylene (3, 0.261 mmol) was added, and the reaction mixture was refluxed for 4 h. After completion of the reaction as monitored by TLC the reaction mixture was cooled and diluted with sat. NaHCO3 solution (40 mL). This was extracted with EtOAc (3 × 20 mL). The combined organic extract was washed with brine and dried over Na2SO4. The solvent was distilled off. The resulting crude product was purified by column chromatography over silica gel (60-120 mesh) using PE-EtOAc (4:1) as eluent to give the compound 4a. Yield 87%; colorless solid; mp 270-272 ˚C. IR (KBr): 1123, 1475, 1543, 1668, 2949 cm-¹.¹H NMR (400 MHz, CDCl3): δ = 3.89 (s, 3 H), 6.36 (d, J = 10.0 Hz, 1 H), 7.43 (q, J = 2.7 Hz, 2 H), 7.50 (d, J = 10.0 Hz, 1 H), 7.54-7.55 (m, 3 H), 7.66 (d, J = 8.4 Hz, 2 H), 7.78 (s, 1 H), 7.89 (d, J = 8.8 Hz, 1 H), 8.10 (d, J = 8.4 Hz, 2 H), 8.38 (d, J = 9.2 Hz, 1 H). ¹³C NMR (100 MHz, CDCl3): δ = 30.4, 114.8, 118.8, 119.0, 122.5, 123.1, 124.1, 128.3, 128.7, 128.8, 129.4, 132.0, 133.8, 137.1, 137.4, 140.4, 141.7, 145.7, 148.1, 154.1, 161.7. MS: m/z = 441, 443 [M + H]+. Anal. Calcd (%) for C25H17BrN2O: C, 68.04; H, 3.88; N, 6.35. Found: C, 67.82; H, 3.67; N, 6.37.