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DOI: 10.1055/s-2008-1072656
Proline-Promoted Efficient Synthesis of 4-Aryl-3,4-dihydro-2H,5H-pyrano[3,2-c]chromene-2,5-diones in Aqueous Media
Publication History
Publication Date:
16 April 2008 (online)
Abstract
The reaction of 4-hydroxycoumarin with Meldrum’s acid and benzaldehydes in aqueous media in the presence of proline (10 mol%) led to 4-aryl-3,4-dihydro-2H,5H-pyrano[3,2-c]chromene-2,5-diones in good yields.
Key words
chromene - proline - aqueous media - Meldrum’s acid - 4-hydroxycoumarin - benzaldehydes
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References and Notes
4-Phenyl-3,4-dihydro-2 H ,5 H -pyrano[3,2- c ]chromene-2,5-dione (4a) To a stirred solution of benzaldehyde (0.21 g, 2 mmol) and Meldrum’s acid (0.29 g, 2 mmol) in 50% aq EtOH (10 mL) were added 4-hydroxycoumarin (0.32 g, 2 mmol) and proline (11.5 mg, 10 mol%). The reaction mixture was stirred at reflux for 40 min. After completion of the reaction (monitored by TLC), the precipitate was collected by filtration and washed by cold 50% aq EtOH (5 mL) to afford 4a, yield 0.55 g (94%); white powder; mp 169-171 °C. IR (KBr): 1788 (C=O), 1707 (C=O), 1630, 1104 cm-1. 1H NMR (500.1 MHz, CDCl3): δ = 3.15 (dd, 2 J = 16.2 Hz, 3 J = 1.7 Hz, 1 H, CH), 3.21 (dd, 2 J = 16.2 Hz, 3 J = 7.6 Hz, 1 H, CH), 4.54 (dd, 3 J = 7.6 Hz, 3 J = 1.7 Hz, 1 H, CH), 7.26-7.29 (m, 3 H, 3 CH), 7.31 (d, 3 J = 6.8 Hz, 1 H, CH), 7.32 (d, 3 J = 6.9 Hz, 1 H, CH), 7.36-7.39 (m, 2 H, 2 CH), 7.62 (t, 3 J = 7.3 Hz, 1 H, CH), 7.92 (dd, 3 J = 8.2 Hz, 4 J = 1.6 Hz, 1 H, CH). 13C NMR (125.7 MHz, CDCl3): δ = 36.3 (CH2), 36.4 (CH), 106.8 (C), 113.9 (C), 117.3 (CH), 123.2 (CH), 125.1 (CH), 127.1 (2 CH), 128.5 (CH), 129.7 (2 CH), 133.4 (CH), 139.8 (C), 153.6 (C), 157.7 (C), 161.2 (C=O), 164.7 (C=O). MS (EI): m/z (%) = 292 (8) [M+], 264 (5), 249 (5), 111 (18), 95 (18), 85 (30), 71 (58), 57 (100), 43 (94). Anal. Calcd (%) for C18H12O4 (292.29): C, 73.97; H, 4.14. Found: C, 73.70; H, 4.31. All other compounds isolated possessed spectroscopic and analytical data in agreement with their proposed structures.