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Synlett 2011(3): 341-344  
DOI: 10.1055/s-0030-1259509
LETTER
© Georg Thieme Verlag Stuttgart ˙ New York

A Simple Method for the Synthesis of Functionalised Chromenes via Vinylogous Michael Addition of α,α-Dicyanoalkenes on Iminocoumarin Derivatives

Thelagathoti Hari Babu, Paramasivan T. Perumal*
Organic Chemistry Division, Central Leather Research Institute (a CSIR Laboratory), Adyar, Chennai 600 020, India
Fax: +91(44)24911589; e-Mail: ptperumal@gmail.com;
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Publication History

Received 30 November 2010
Publication Date:
25 January 2011 (online)

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Abstract

A one-pot synthesis of 2-amino-4H-chromenes was achieved in good yields from three-component reaction of salicyl­aldehyde, malononitrile, and α,α-dicyanoalkenes catalysed by triethylamine.

Key words

2-amino-4H-chromenes - vinylogous Michael addition - α,α-dicyanoalkenes - multicomponent reactions

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General Procedure for the Synthesis of 2-Amino Chromenes 4a-h from Salicylaldehyde, Malononitrile, and α,α-Dicyanoalkenes 3a-h - Representative Procedure for 2-Amino-4-(3,3-dicyano-2-phenylallyl)-4 H -chromene-3-carbonitrile (4a)
To a stirred mixture of salicylaldehyde (1 mmol) and malononitrile (1 mmol) in EtOH, vinyl malononitrile 3a (1.5 mmol), and Et3N (0.5 mmol) were added. The reaction mixture was stirred at r.t. for the appropriate time (Table  [²] ). After complete conversion as indicated by TLC, the mixture was concentrated under vacuo and subjected to chromatographic purification over silica gel (Merck; 100-200 mesh; EtOAc-hexane, 3:7) to obtain chromene 4a (78%).
Spectral Data of 2-Amino-4-(3,3-dicyano-2-phenylallyl)-4 H -chromene-3-carbonitrile (4a, Table 2, Entry 1) Pale pink solid; yield 78%. ¹H NMR (500 MHz, DMSO-d 6): δ = 3.18 (dd, J 1 = 7.65 Hz, J 2 = 5.35 Hz, 1 H), 3.31 (dd, J 1 = 5.35 Hz, J 2 = 8.4 Hz, 1H), 3.56 (t, J = 5.35 Hz, 1 H), 6.93 (d, J = 7.6 Hz, 1 H), 7.09 (s, 2 H, D2O exchangeable), 7.13 (t, J = 6.1 Hz, 4 H), 7.28 (t, J = 8.4 Hz, 1 H) 7.53 (m, 3 H) 7.65 (d, J = 7.6 Hz, 1 H). ¹³C NMR (125 MHz, DMSO-d 6): δ = 35.6, 48.1, 52.7, 86.1, 113.2, 113.7, 116.5, 121.0, 122.8, 125.2, 128.8, 128.9, 128.9, 129.2, 129.4, 129.4, 132.6, 134.5, 149.6, 162.7, 177.0. IR (KBr): νmax = 3384, 3326, 2183, 1653, 1423, 1050, 757 cm-¹. ESI-MS: 339 [M + 1]. Anal. Calcd (%) for C21H14N4O: C, 74.54; H, 4.17; N, 16.56. Found: C, 75.97; H, 4.11; N, 15.71.
Spectral Data of 3-Amino-1-[2-(dicyanomethylene)-4-methylpentyl]-1 H -benzo[ f ]chromene-2-carbonitrile (6) Pale brown solid; yield 70%. ¹H NMR (500 MHz, CDCl3): δ = 0.86 (d, J = 6.1 Hz, 3 H), 1.01 (d, J = 6.15 Hz, 3 H), 1.91 (m, 1 H), 2.42 (dd, J 1 = 8.4 Hz, J 2 = 4.6 Hz, 1 H) 2.59 (dd, J 1 = 6.85 Hz, J 2 = 6.15 Hz, 1 H), 2.85 (dd, J 1 = 9.2 Hz, J 2 = 3.8 Hz, 1 H), 3.00 (dd, J 1 = 3.8 Hz, J 2 = 8.45 Hz, 1 H), 4.55 (dd, J 1 = 4.6 Hz, J 2 = 4.6 Hz, 1 H), 5.00 (s, 2 H, D2O exchangeable), 7.20 (d, J = 9.15 Hz, 1 H), 7.52 (t, J = 6.9 Hz, 1 H), 7.64 (t, J = 7.65 Hz, 1 H), 7.85 (m, 3 H). ¹³C NMR (125 MHz, CDCl3): δ = 22.2, 22.8, 29.2, 32.6, 43.2, 45.1, 56.5, 89.5, 111.7, 112.0, 115.1, 116.9, 119.6, 121.5, 125.7, 128.0, 129.3, 129.7, 130.0, 131.5, 147.7, 161.9, 180.1. IR (KBr): νmax = 3434, 3327, 2959, 2183, 1643 cm-¹. ESI-MS: 369 [M + 1]. Anal. Calcd (%) for C23H20N4O: C, 74.98; H, 5.47; N, 15.21%. Found: C, 74.87; H, 5.11; N, 15.11.

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Crystallographic data for compound 4m in this paper have been deposited with the Cambridge Crystallographic Data Centre as supplemental publication No. CCDC-796193. Copies of the data can be obtained, free of charge on application to CCDC, 12 Union Road, Cambridge CB2 1EZ, UK [fax: +44 (1223)336033 or email: deposit@ccdc.cam.ac.uk].