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Synlett 2009(12): 1921-1922  
DOI: 10.1055/s-0029-1217542
LETTER
© Georg Thieme Verlag Stuttgart ˙ New York

An Efficient Synthesis of Functionalized 6,10-Dioxo-6,10-dihydro-5H-pyrido[1,2-a]quinoxalines and 6,10-Dioxo-6,10-dihydropyrido[2,1-c][1,4]benz­oxazines

Issa Yavari*, Sanaz Souri, Mehdi Sirouspour, Mohammad J. Bayat
Chemistry Department, Tarbiat Modares University, PO Box 14115-175, Tehran 18716, Iran
Fax: +98(21)82883455; e-Mail: yavarisa@modares.ac.ir;
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Publication History

Received 9 March 2009
Publication Date:
03 July 2009 (online)

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Abstract

An efficient synthesis of alkyl 8-hydroxy-6,10-di­oxo-6,10-dihydro-5H-pyrido[1,2-a]quinoxaline-7-carboxylates and alkyl 8-hydroxy-6,10-dioxo-6,10-dihydropyrido[2,1-c][1,4]benzoxa­zine-7-carboxylates is described. This involves the reaction between malonyl dichloride and alkyl 2-[3,4-dihydro-3-oxo­quinoxaline 2(1H)-ylidene]acetates or alkyl 2-(2-oxo-2H-benzo[b][1,4]oxazin-3(4H)-ylidene)acetates in CH2Cl2 at room temperature.

Key words

malonyl dichloride - pyrido[1,2-a]quinoxaline - pyrido[2,1-c][1,4]benzoxazine - benzene-1,2-diamine - 2-aminophenol - acetylenic ester

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General Procedure for the Synthesis of Compounds 4
To a suspension of 3 (2 mmol) [¹8] in CH2Cl2 (10 mL) was added of malonyl dichloride (0.29 g, 2.1 mmol) at r.t. The reaction mixture was then stirred for 15 min. The formed precipitate was filtered off and washed with CH2Cl2 to afford the pure product. Compound 4a: pale yellow powder; mp 300-304 ˚C (dec.); yield 0.56 g (98%). IR (KBr): νmax = 3450, 1729, 1693, 1655, 1490, 1418, 1365, 1306, 1258, 1106, 757 cm-¹. ¹H NMR (500 MHz, CDCl3): δ = 3.74 (3 H, s, OMe), 6.08 (1 H, s, CH), 7.12 (1 H, d, ³ J = 7.8 Hz, CH), 7.20 (1 H, t, ³ J = 7.9 Hz, CH), 7.30 (1 H, t, ³ J = 8.0 Hz, CH), 9.19 (1 H, d, ³ J = 7.8 Hz, CH), 11.76 (1 H, s, OH), 11.84 (1 H, s, NH) ppm. ¹³C NMR (125.7 MHz, CDCl3): δ = 52.6 (OMe), 102.9 (CH), 112.4 (C), 116.4 (CH), 121.5 (CH), 122.8 (CH), 123.9 (C), 127.3 (CH), 128.1 (C), 133.0 (C), 156.2 (COH), 162.1 (CO), 162.9 (CO), 165.3 (CO2) ppm. MS: m/z (%) = 285 (20) [M - 1+], 262 (20), 236 (35), 179 (10), 123 (40), 97 (50), 83 (55), 69 (60), 57 (100), 43 (90). Anal. Calcd (%) for C14H10N2O5 (286.24): C, 58.75; H, 3.52; N, 9.79. Found: C, 58.60; H, 3.44; N, 9.65. Compound 4d: pale yellow powder; mp 298-300 ˚C (dec.); yield 0.55 g (97%). IR (KBr) νmax = 3505, 1764, 1721, 1661, 1618, 1499, 1408, 1333, 1304, 1294, 1106, 759 cm-¹. ¹H NMR (500 MHz, CDCl3): δ = 3.79 (3 H, s, OMe), 6.12 (1 H, s, CH), 7.27 (1 H, t, ³ J = 7.0 Hz, CH), 7.30 (1 H, d, ³ J = 7.9 Hz, CH), 7.33 (1 H, t, ³ J = 8.0 Hz, CH), 9.18 (1 H, d, ³ J = 8.6 Hz, CH), 12.01 (1 H, s, OH) ppm.¹³C NMR (125.7 MHz, CDCl3): δ = 52.5 (OMe), 104.1 (CH), 114.8 (C), 116.8 (CH), 120.6 (CH), 123.1 (C), 124.3 (CH), 127.0 (CH), 127.9 (C), 141.1 (C), 154.2 (COH), 161.4 (CO), 161.5 (CO), 164.1 (CO2) ppm. Anal. Calcd (%) for C14H9NO6 (287.22): C, 58.54; H, 3.16; N, 4.88. Found: C, 58.60; H, 3.14; N, 4.85. Compound 4g: yellow powder; mp 298-301 ˚C (dec.); yield 0.58 g (98%). IR (KBr) νmax = 3440, 1764, 1722, 1665, 1621, 1455, 1324, 1286, 1250, 1107, 765 cm-¹. ¹H NMR (500 MHz, CDCl3): δ = 2.32 (3 H, s, Me), 3.78 (3 H, s, OMe), 6.10 (1 H, s, CH), 7.15 (1 H, d, ³ J = 8.3 Hz, CH), 7.19 (1 H, d, ³ J = 8.3 Hz), 9.03 (1 H, s, CH), 11.99 (1 H, s, OH) ppm. ¹³C NMR (125.7 MHz, CDCl3): δ = 20.9 (Me), 52.4 (OMe), 104.1 (CH), 114.8 (C), 116.5 (CH), 120.7 (CH), 122.6 (C), 127.4 (CH), 127.9 (C), 133.5 (C), 139.0 (C), 154.3 (C-OH), 161.3 (CO), 161.4 (CO), 164.1 (CO2) ppm. Anal. Calcd (%) for C15H11NO6 (301.25): C, 59.81; H, 3.68; N, 4.65. Found: C, 59.80; H, 3.65; N, 4.65.
All other novel compounds isolated possessed spectroscopic and analytical data in keeping with their proposed structures.