Synlett 2008(18): 2791-2794  
DOI: 10.1055/s-0028-1087297
LETTER
© Georg Thieme Verlag Stuttgart ˙ New York

Indium-Mediated One-Pot Synthesis of New 4-Allyl-2-amino-4H-chromenes in Water

Gnanamani Shanthi, Paramasivan T. Perumal*
Organic Chemistry Division, Central Leather Research Institute, Adyar, Chennai 600020, India
Fax: +91(44)24911589; e-Mail: ptperumal@gmail.com;
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Publikationsverlauf

Received 30 June 2008
Publikationsdatum:
21. Oktober 2008 (online)

Abstract

A one-pot synthesis of new 4-allyl-2-amino-4H-chromene-3-carbonitriles was achieved in good yields by indium-mediated three-component reaction of salicylaldehyde and malononitrile with different allyl bromides in water.

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General Procedure for the Synthesis of 2-Amino-chromenes 4a-k and 7a,b from Salicylaldehyde, Malononitrile and Allyl Bromide/Prenyl Bromide; Representative Procedure for 4-Allyl-2-amino-4 H -chromene-3-carbonitrile (4a; Table 1, entry 1): A mixture of salicylaldehyde (1 mmol) and malononitrile (1 mmol) in H2O (10 mL) was stirred for about 15-20 min. Allyl bromide (1.5 mmol), indium (1.05 mmol) and NaI (1.55 mmol) were then added and the mixture was stirred at r.t. for the appropriate time (Table  [¹] ). After complete conversion as indicated by TLC, the reaction was quenched with few drops of 1 N HCl solution. The mixture was extracted with Et2O and the Et2O extract was washed with brine, dried (Na2SO4) and evaporated to leave the crude product which was purified by column chromatography over silica gel (Merck, 60-120 mesh, EtOAc-hexane, 1:9) to furnish pure product 4a (80%).

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2-Amino-4-(1,1-dimethylprop-2-en-1-yl)-4 H -chromene-3-carbonitrile (4b; Table 1, entry 2): white solid; mp 182-184 ˚C. IR (KBr): 3439, 3341, 2971, 2177, 1635, 1572, 1411, 1261, 764 cm. ¹H NMR (500 MHz, DMSO-d 6): δ = 0.84 (s, 3 H), 0.89 (s, 3 H), 3.21 (s, 1 H), 4.73 (d, 1 H, J = 17.6 Hz), 4.86 (d, 1 H, J = 10.7 Hz), 5.71 (dd, 1 H, J = 17.6, 10.7 Hz), 6.90 (br s, 2 H, NH2, D2O exchangeable), 6.96 (d, 1 H, J = 8.4 Hz), 7.07 (t, 1 H, J = 7.6 Hz), 7.12 (d, 1 H, J = 6.9 Hz), 7.20 (t, 1 H, J = 6.9 Hz). ¹³C NMR (75 MHz, DMSO-d 6): δ = 22.9, 23.9, 44.2, 45.6, 52.2, 112.5, 115.6, 122.0, 123.0, 123.4, 127.8, 129.9, 145.1, 150.8, 163.4. MS: m/z = 240 [M+]. Anal. Calcd for C15H16N2O: C, 74.97; H, 6.71; N, 11.66. Found: C, 74.94; H, 6.65; N, 11.62.

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1-Allyl-3-amino-1 H -benzo[ f ]chromene-2-carbonitrile (7a; Scheme 4): light yellow solid; mp 250-252 ˚C. IR (KBr): 3435, 3365, 2966, 2186, 1733, 1643, 1563, 1411, 1216, 817 cm. ¹H NMR (500 MHz, DMSO-d 6): δ = 2.39 (t, 2 H, J = 6.1 Hz), 4.26 (t, 1 H, J = 5.4 Hz), 4.80 (d, 1 H, J = 16.8 Hz), 4.86 (d, 1 H, J = 9.9 Hz), 5.52 (m, 1 H), 6.91 (br s, 2 H, NH2, D2O exchangeable), 7.14 (d, 1 H, J = 9.2 Hz), 7.41 (t, 1 H, J = 6.9 Hz), 7.52 (t, 1 H, J = 8.5 Hz), 7.78 (d, 1 H, J = 9.2 Hz), 7.86 (d, 1 H, J = 8.5 Hz), 7.97 (d, 1 H, J = 8.4 Hz). ¹³C NMR (75 MHz, DMSO-d 6): δ = 32.0, 40.7, 53.9, 116.3, 116.5, 118.1, 120.9, 122.8, 124.8, 127.1, 128.6, 128.7, 129.8, 130.7, 133.8, 147.2, 161.7. MS: m/z = 262 [M+]. Anal. Calcd for C17H14N2O: C, 77.84; H, 5.38; N, 10.68. Found: C, 77.80; H, 5.32; N, 10.62.