1154
I. Yavari et al.
LETTER
O
O
O
O
_
C
COOH
O
O
O
H
O
O
acetone
Ar
Ar
O
O
HOOC
+
1
H
O
N
3
H
O
O
O
Ar
8
9
7
O
O
HOOC
N+
O
COOH
O
O
H
Ar
O
O
H
CO2
5
Ar
HOOC
N
Ar
4
2
O
6
10
Scheme 1
(8) Yavari, I.; Adib, M.; Sayahi, M. H. Tetrahedron Lett. 2002,
43, 2927.
(9) Yavari, I.; Sabbaghan, M.; Hossaini, Z. Synlett 2006, 2501.
(10) Yavari, I.; Hossaini, Z.; Sabbaghan, M. Tetrahedron Lett.
2006, 47, 6037.
(11) Yavari, I.; Moradi, L. Tetrahedron Lett. 2006, 47, 1627.
(12) 4-Phenyl-3,4-dihydro-2H,5H-pyrano[3,2-c]chromene-
2,5-dione (4a)
and then undergoes cyclization and decarboxylation to
produce 4.
In conclusion, we have described a convenient route to 4-
aryl-3,4-dihydro-2H,5H-pyrano[3,2-c]chromene-2,5-di-
ones from 4-hydroxycoumarin, Meldrum’s acid, and benz-
aldehydes in aqueous media in the presence of proline (10
mol%). The functionalized chromenes reported in this
work may be considered as potentially useful synthetic in-
termediates because they possess atoms with different ox-
idation states. The advantage of the present procedure is
that the reaction is performed under neutral conditions by
simple mixing of the starting materials. The simplicity of
the present procedure makes it an interesting alternative to
other approaches.
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): d = 3.15 (dd, 2J = 16.2 Hz, 3J = 1.7 Hz,
1 H, CH), 3.21 (dd, 2J = 16.2 Hz, 3J = 7.6 Hz, 1 H, CH), 4.54
(dd, 3J = 7.6 Hz, 3J = 1.7 Hz, 1 H, CH), 7.26–7.29 (m, 3 H,
3 CH), 7.31 (d, 3J = 6.8 Hz, 1 H, CH), 7.32 (d, 3J = 6.9 Hz, 1
H, CH), 7.36–7.39 (m, 2 H, 2 CH), 7.62 (t, 3J = 7.3 Hz, 1 H,
CH), 7.92 (dd, 3J = 8.2 Hz, 4J = 1.6 Hz, 1 H, CH). 13C NMR
(125.7 MHz, CDCl3): d = 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.
References and Notes
(1) Miao, H.; Yang, Z. Org. Lett. 2000, 2, 1765.
(2) Kumar, P.; Bodas, M. S. Org. Lett. 2000, 2, 3821.
(3) Chauder, B. A.; Lopes, C. C.; Lopes, R. S. C.; Dasilva, A. J.
M.; Snieckus, V. Synthesis 1998, 279.
(4) Parker, A. K.; Mindt, T. L. Org. Lett. 2001, 3, 3875.
(5) Yu, N.; Aramini, J. M.; Germann, M. W.; Huang, Z.
Tetrahedron Lett. 2000, 41, 6993.
(6) Hepworth, J. D.; Gabbutt, C. D.; Heron, B. M.
Comprehensive Heterocyclic Chemistry, Vol. 5; Katritzky,
A. R.; Rees, C. W.; Scriven, E. F. V., Eds.; Pergamon:
Oxford, 1996, 351–468.
(7) Yavari, I.; Ramazani, A. J. Chem. Res., Synop. 1996, 382.
Synlett 2008, No. 8, 1153–1154 © Thieme Stuttgart · New York