Synlett 2007(9): 1379-1382  
DOI: 10.1055/s-2007-980354
LETTER
© Georg Thieme Verlag Stuttgart · New York

Magnesium Perchlorate: An Efficient Catalyst for One-Pot Synthesis of Pyrano- and Furanoquinolines

Vinod T. Kamble*, Vijaymala R. Ekhe, Neeta S. Joshi, Ankush V. Biradar
Organic Chemistry Research Laboratory, School of Chemical Sciences, Swami Ramanand Teerth Marathwada University, Nanded 431606 (M.S.), India
Fax: +91(2462)259465; e-Mail: vtkd@rediffmail.com;
Further Information

Publication History

Received 29 November 2006
Publication Date:
23 May 2007 (online)

Abstract

The pyranoquinoline moiety is a structural feature of many natural products. By using a reaction of anilines, aldehydes and 3,4-dihydro-2H-pyran or 2,3-dihydrofuran catalyzed by trace amount of magnesium perchlorate at room temperature, various pyrano- and furanoquinoline derivatives were synthesized efficiently. The noteworthy features of the present system are mild conditions, shorter reaction time, and high diastereoselectivity.

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General Experimental Procedure
A mixture of the aniline (5 mmol), aldehyde (5 mmol), dihydropyran or dihydrofuran (7 mmol), Mg(ClO4)2 (0.25 mmol, 5 mol%) in MeCN (2 mL) was stirred at r.t. for an appropriate time (Table [1] ). After completion of the reaction, as indicated by TLC, the reaction mixture was diluted with EtOAc (2 × 10 mL) and washed with H2O (2 × 10 mL) followed by brine (2 × 15 mL). The combined organic extracts were dried over Na2SO4, concentrated in vacuo and purified by column chromatography on silica gel (Merck, 100-200 mesh; EtOAc-hexane, 1:9) to afford the pure pyrano- or furanoquinoline.
Spectral data of selected compounds:
Compound 4j: IR (KBr): 3325 cm-1. 1H NMR (200 MHz, CDCl3): δ = 1.35 (m, 1 H), 1.50 (m, 1 H), 1.65 (m, 1 H), 1.85 (m, 1 H), 2.15 (m, 1 H), 3.75 (m, 1 H), 3.90 (br s, 1 H), 4.15 (m, 1 H), 4.40 (d, J = 2.8 Hz, 1 H), 4.70 (d, J = 10.5 Hz, 1 H), 6.70 (t, J = 8.0 Hz, 1 H), 7.05 (dd, J = 8.0, 0.8 Hz, 1 H), 7.15 (dd, J = 8.0, 1.5 Hz, 1 H), 7.30-7.35 (m, 1 H), 7.40-7.45 (m, 2 H), 7.50-7.55 (m, 2 H). MS: m/z = 311 [M+ + 1]. Anal. Calcd for C18H18N2O3: C, 69.66; H, 5.84; N, 9.02. Found: C, 69.64; H, 5.83; N, 9.01.
Compound 5j: IR (KBr): 3375 cm-1. 1H NMR (200 MHz, CDCl3): δ = 1.40-1.60 (m, 4 H), 2.10 (m, 1 H), 3.41 (m, 1 H), 3.55-3.70 (m, 2 H), 4.65 (d, J = 2.5 Hz, 1 H), 5.25 (d, J = 5.2 Hz, 1 H), 6.70 (t, J = 7.8 Hz, 1 H), 7.05 (dd, J = 7.8, 0.8 Hz, 1 H), 7.35-7.45 (m, 6 H). MS: m/z = 311 [M+ + 1].
Compound 4m: IR (KBr): 3315 cm-1. 1H NMR (200 MHz, CDCl3): δ = 1.72 (m, 1 H), 2.00 (m, 1 H), 2.45 (m, 1 H), 3.42-3.85 (m, 3 H), 4.08 (m, 1 H), 4.58 (d, J = 5.0 Hz, 1 H), 6.42 (d, J = 8.0 Hz, 1 H), 6.64 (d, J = 8.0 Hz, 1 H), 7.05 (t, J = 8.0 Hz, 1 H), 7.14 (d, J = 8.0 Hz, 1 H), 7.35 (s, 4 H). MS: m/z = 297 [M+ + 1]. Anal. Calcd for C17H16N2O3: C, 68.90; H, 5.44; N, 9.45. Found: C, 69.84; H, 5.48; N, 9.44.
Compound 5m: IR (KBr): 3365 cm-1. 1H NMR (200 MHz, CDCl3): δ = 1.50-1.62 (m, 2 H), 2.18 (m, 1 H), 3.40-3.62 (m, 2 H), 3.78 (br s, 1 H), 4.65 (d, J = 3.0 Hz, 1 H), 5.25 (d, J = 8.0 Hz, 1 H), 6.53 (t, J = 8.0 Hz, 1 H), 6.68 (t, J = 8.0 Hz, 1 H), 7.05 (t, J = 8.0 Hz, 1 H), 7.36 (s, 4 H), 7.40 (d, J = 8.0 Hz, 1 H). MS: m/z = 297 [M+ + 1].
Compound 4o: IR (KBr): 3320 cm-1. 1H NMR (200 MHz, CDCl3): δ = 1.65 (m, 1 H), 2.05 (m, 1 H), 2.35 (s, 3 H), 2.45 (m, 1 H), 3.80 (m, 2 H), 4.05 (m, 2 H), 4.60 (d, J = 5.0 Hz, 1 H), 6.72 (t, J = 7.8 Hz, 1 H), 6.95 (d, J = 7.8 Hz, 1 H), 7.22-7.45 (m, 6 H); MS: m/z = 266 [M+ + 1]. Anal. Calcd for C18H19NO: C, 81.47; H, 7.21; N, 5.27. Found: C, 81.45; H, 7.24; N, 5.26.
Compound 5o: IR (KBr) 3370 cm-1; 1H NMR (200 MHz, CDCl3): δ = 1.50 (m, 1 H), 2.20 (m, 1 H), 2.40 (s, 3 H), 2.75 (m, 1 H), 3.60 (br s, 1 H), 3.70 (m, 1 H), 3.80 (m, 1 H), 4.65 (d, J = 2.6 Hz, 1 H), 5.25 (d, J = 8.0 Hz, 1 H), 6.70 (d, J = 8.1 Hz, 1 H), 7.00 (t, J = 8.0 Hz, 1 H), 7.25 (t, J = 8.0 Hz, 1 H), 7.35-7.50 (m, 5 H). MS: m/z = 266 [M+ + 1].
Compound 4s: IR (KBr): 3340 cm-1. 1H NMR (200 MHz, CDCl3): δ = 1.65 (m, 1 H), 1.92 (m, 1 H), 2.43 (m, 1 H), 3.82 (m, 2 H), 4.02 (m, 2 H), 4.55 (d, J = 4.9 Hz, 1 H), 6.72 (t, J = 7.5 Hz, 1 H), 6.99 (t, J = 7.5 Hz, 1 H), 7.26-7.46 (m, 6 H). MS: m/z = 297 [M+ + 1].
Compound 5s: IR (KBr): 3385 cm-1. 1H NMR (200 MHz, CDCl3): δ = 1.46 (m, 1 H), 2.20 (m, 1 H), 2.79 (m, 1 H), 3.66-3.80 (m, 3 H), 4.70 (d, J = 3.0 Hz, 1 H), 5.32 (d, J = 8.0 Hz, 1 H), 6.77 (t, J = 7.5 Hz, 1 H), 6.99 (d, J = 6.6 Hz, 1 H), 7.25 (d, J = 6.6 Hz, 1 H), 7.33-7.51 (m, 5 H). MS: m/z = 297 [M+ + 1].