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Synlett 2010(5): 757-760  
DOI: 10.1055/s-0029-1219364
LETTER
© Georg Thieme Verlag Stuttgart ˙ New York

A Flexible Approach to the Chromenoquinolines under Copper/Lewis Acid Catalysis

Subburethinam Ramesh, Vikram Gaddam, Rajagopal Nagarajan*
School of Chemistry, University of Hyderabad, Central University (P.O.), Hyderabad 500046, India
Fax: +91(40)23012460; e-Mail: rnsc@uohyd.ernet.in;
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Publication History

Received 18 November 2009
Publication Date:
02 February 2010 (online)

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Abstract

The synthesis of chromenoquinolines via cyclization of different substituted anilines or naphthylamine with O-propargylated salicylaldehydes using CuI/La(OTf)3 as an efficient catalyst in the reflux temperature of acetonitrile is reported.

Key words

chromenoquinoline - estrogenic agents - catalyst

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The CCDC deposition number of 3c is 753403; molecular formula: C17H13NO2, chemical formula weight 263.28, monoclinic, unit cell parameters: a = 13.037 (8), b = 7.587 (4), c = 13.158 (8), β = 97.576 (9), space group P21/c.
The CCDC deposition number of 6a is 753401; molecular formula: C30H13NO, chemical formula weight 283.31, monoclinic, unit cell parameters: a = 8.6729 (14), b = 15.418 (3), c = 10.8031 (18), β = 106.891 (2), space group P21/c.
The CCDC deposition number of 3b is 753402; molecular formula: C17H13NO, chemical formula weight 247.29, monoclinic, unit cell parameters: a = 12.9795 (11), b = 23.1902 (19), c = 8.4440 (7), β = 95.2790 (10), space group P21/c.
The CCDC deposition number of 3f is 753404; molecular formula: C16H10ClNO, chemical formula weight 267.71, monoclinic, unit cell parameters: a = 31.333 (3), b = 3.8586 (4), c = 40.188 (5), β = 102.334 (4), space group C2/c.

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A Typical Procedure for the Preparation of 3a
In a round-bottom flask equipped with a magnetic stirring bar, aniline (1a, 1.0 mmol), O-propargylated salicylaldehyde (2a, 1.0 mmol) in MeCN (20 mL), was added La(OTf)3 (10 mol%) and CuI (10 mol%). Reaction mixture was stirred at reflux temperature of MeCN for 4 h. After completion of the reaction, as indicated by the TLC, the MeCN was evaporated and H2O (20 mL) was added to the crude reaction mass. Then aqueous layer was extracted with CH2Cl2 (3 × 20 mL), and the combined organic layers were dried over anhyd Na2SO4, filtered, and concentrated under reduced pressure. The product was purified by column chromatography on silica gel (eluent: hexane-EtOAc) afforded 3a (0.210 g, 90%); mp 126 ˚C. IR (KBr): 3051, 2295, 1649, 1033, 740 cm-¹. ¹H NMR (400 MHz, CDCl3, TMS): δ = 8.48 (1 H, d, J = 8.0 Hz), 8.11 (1 H, d, J = 8.0 Hz), 7.81 (1 H, s), 7.72 (1 H, d, J = 7.5 Hz), 7.67 (1 H, t, J = 7.5 Hz), 7.46 (1 H, t, J = 6.5 Hz), 7.36 (1 H, t, J = 7.5 Hz), 7.16 (1 H, t, J = 7.5 Hz), 7.01 (1 H, d, J = 7.5 Hz), 5.32 (2 H, s). ¹³C NMR (100 MHz, CDCl3, TMS): δ = 157.4, 149.0, 148.3, 131.8, 130.9, 129.5, 129.4, 127.5, 127.4, 126.2, 125.5, 125.2, 123.2, 122.5, 117.3 (arom. C); 68.4 (aliph. C). MS (+): m/z = 234 [M + H]. Anal. Calcd for C16H11NO: C, 82.38; H, 4.75; N, 6.00. Found: C, 82.25; H, 4.80; N, 6.12.