Synlett 2012(5): 717-722  
DOI: 10.1055/s-0031-1290565
LETTER
© Georg Thieme Verlag Stuttgart ˙ New York

One-Pot Synthesis of Pyrrolo[3,2-f]- and Pyrrolo[2,3-h]quinoline Derivatives: Observation of an Unexpected Mechanistic Pathway

Subburethinam Ramesh, Rajagopal Nagarajan*
School of Chemistry, University of Hyderabad, Hyderabad 500046, India
Fax: +91(40)23012460; e-Mail: rnsc@uohyd.ernet.in;
Further Information

Publication History

Received 11 November 2011
Publication Date:
24 February 2012 (online)

Abstract

One-pot synthesis of pyrrolo[3,2-f]- and pyrrolo[2,3-h]quinolines were obtained starting from substituted 5-aminoindoles, benzaldehydes, and phenylacetylenes in the presence of La(OTf)3 as a catalyst in good yields. The indole moiety in 5-aminoindole is believed to be mainly responsible for the observation of unexpected mechanistic pathway to the formation of pyrrolo[2,3-h]quinoline.

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The CCDC deposition number for compound 4a is 796984. Formula: C26H22N2. Unit cell parameters: a = 7.3436 (16), b = 11.1808 (17), c = 12.467 (3), α = 99.382 (15), β = 102.495 (19), γ = 94.742 (15), space group P-1. The CCDC deposition number for compound 5g is 796985. Formula: C58H56N4. Unit cell parameters: a = 8.3864 (9), b = 13.2389 (14), c = 21.6848 (19), α = 80.350 (8), β = 82.567 (8), γ = 82.391 (9), space group P-1.

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See the Supplementary Information for 5-aminoindoles 1a-h preparation.