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Synlett 2014; 25(2): 243-246
DOI: 10.1055/s-0033-1340217
letter
© Georg Thieme Verlag Stuttgart · New York

1-(2-Allylaryl)-1H-pyrroles as Building Blocks for Novel 4-Methyl-4,5-di­hydropyrrolo[1,2-a]quinoline Derivatives

Julio Cesar Orejarena
a   Laboratorio de Síntesis Orgánica, Escuela de Química, Universidad Industrial de Santander, Carrera 27, Calle 9, A.A 678, Bucaramanga, Colombia   Fax: +57(7)6349069   eMail: apalma@uis.edu.co
,
Sandra Liliana Gómez
a   Laboratorio de Síntesis Orgánica, Escuela de Química, Universidad Industrial de Santander, Carrera 27, Calle 9, A.A 678, Bucaramanga, Colombia   Fax: +57(7)6349069   eMail: apalma@uis.edu.co
,
Alirio Palma*
a   Laboratorio de Síntesis Orgánica, Escuela de Química, Universidad Industrial de Santander, Carrera 27, Calle 9, A.A 678, Bucaramanga, Colombia   Fax: +57(7)6349069   eMail: apalma@uis.edu.co
,
Justo Cobo
b   Inorganic and Organic Department, University of Jaén, Campus Las Lagunillas s/n, 23071, Jaén, Spain   Fax: +34(953)211876   eMail: jcobo@ujaen.es
,
Manuel Nogueras
b   Inorganic and Organic Department, University of Jaén, Campus Las Lagunillas s/n, 23071, Jaén, Spain   Fax: +34(953)211876   eMail: jcobo@ujaen.es
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Publikationsverlauf

Received: 03. September 2013

Accepted after revision: 10. Oktober 2013

Publikationsdatum:
02. Dezember 2013 (online)

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Abstract

Novel substituted 4-methyl-4,5-dihydropyrrolo[1,2-a]-quinolines were prepared by a simple two-step approach involving a Clauson-Kaas reaction of a substituted ortho-allylaniline followed by acid-catalyzed regioselective intramolecular Friedel–Crafts alkylation of the resulting 1-(2-allylaryl)-1H-pyrroles. All the synthetized compounds were fully characterized by IR, 1H and 13C NMR spectroscopy, and mass spectrometry.

Key words

pyrroles - quinolines - alkylation - heterocycles - cyclization

Supporting Information

    for this article is available online at http://www.thieme-connect.com/ejournals/toc/synlett.
  • Supporting Information
 

  • References

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  • 17 4-Methyl-4,5-dihydropyrrolo[1,2-a]quinolines 3a–h; General Procedure Concd H2SO4 (98%, 4 mmol) was added to a stirred and cooled solution of the appropriate 1-(2-allylaryl)pyrrole 2a–h (1 mmol) in CH2Cl2 (5 mL), and the mixture was stirred at 0 °C for 5–15 min (TLC). It was then poured onto ice-water (50 mL), neutralized to pH 7.5–8.0 with sat. aq Na2CO3, and extracted with CH2Cl2 (3 × 50 mL). The organic layers were combined, dried (Na2SO4), and concentrated under reduced pressure. The crude product was purified by column chromatography [silica gel, heptane–EtOAc (90:1 to 70:1)]. 4-Methyl-4,5-dihydropyrrolo[1,2-a]quinoline (3a) Colorless viscous oil; yield: 58%; Rf = 0.38 (1% EtOAc–heptane). IR (liquid film): 2962 (C–H aliphatic), 1558 (C=C pyrrole), 1500 (C=C benzene), 1332 (=C–H pyrrole), 1168 (C–N) cm–1. 1H NMR (400 MHz, CDCl3): δ = 7.36 (br d, J = 7.6 Hz, 1 H, H9), 7.29 (br t, J = 7.6 Hz, 1 H, H8), 7.26 (br d, J = 7.6 Hz, 1 H, H6), 7.20 (br dd, J = 2.8, 1.2 Hz, 1 H, H1), 7.09 (td, J = 7.6, 1.0 Hz, 1 H, H7), 6.32 (t, J = 3.2 Hz, 1 H, H2), 6.08 (dt, J = 3.2, 1.2 Hz, 1 H, H3), 3.09–3.00 (m, 1 H, H4), 2.89 (dd, J = 14.8, 5.2 Hz, 1 H, H5B), 2.63 (dd, J = 14.8, 12.4 Hz, 1 H, H5A), 1.41 (d, J = 6.8 Hz, 3 H, 4-CH3). 13C NMR (100 MHz, CDCl3): δ = 136.5 (C9a), 135.2 (C3a), 129.0 (C6), 128.0 (C5a), 127.4 (C8), 123.8 (C7), 115.1 (C9), 114.7 (C1), 109.7 (C2), 104.1 (C3), 35.5 (C5), 28.2 (C4), 18.6 (4-CH3). GC/MS (EI, 70 eV): m/z (%) = 183 (30) [M+•], 182 (9), 168 (100), 167 (39), 154 (3). HRMS: m/z [M]+ calcd for C13H13N: 183.1048; found: 183.1047.