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Reduction of 3-Formylchromones
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GENERAL PROCEDURE FOR REDUCTION OF
FORMYLCHROMONES
About 1 g of basic alumina and about 50 mg of the corresponding
formyl chromone (5% of alumina weight) dissolved in 10 mL of 2-pro-
panol were placed in a round-bottomflask containing a magnetic bar, the
mixture is stirred for 4 h at 75ꢀC. Vacuumfiltration through celite, and
rotatory evaporation of solvent give crude alcohols which may be
purified by column chromatography using ethyl acetate/hexane 1:1 as
eluent.
3-(Hydroxymethyl)-4-oxo-4H-1-benzopyrane (2a). M.p. 109–110ꢀC
(Lit.[6] 108–110ꢀC). 1H NMR, ꢀ (CDCl3): 3.00 (t, 1H, J ¼ 6.3 Hz,
CH2OH), 4.59 (dd, 2H, J1 ¼ 6.3 Hz, J2 ¼ 0.7 Hz, CH2OH), 7.43 (ddd,
1H, J1 ¼ 7.9 Hz, J2 ¼ 7.3 Hz, J3 ¼ 1.0 Hz, 6-H), 7.48 (1H, d, J ¼ 8.6 Hz,
8-H), 7.70 (ddd, 1H, J1 ¼ 8.6 Hz, J2 ¼ 6.9 Hz, J3 ¼ 1.6 Hz, 7-H), 7.95 (t,
1H, J ¼ 0.7 Hz, 2-H), 8.24 (dd, 1H, J1 ¼ 7.9 Hz, J2 ¼ 1.6 Hz, 5-H).
5-Hydroxy-3-(hydroxymethyl)-4-oxo-4H-1-benzopyrane (2b). M.p.
102–104ꢀC. 1H NMR, ꢀ (CDCl3): 4.58 (s, 2H, CH2OH), 5.12 (t, 1H,
J ¼ 0.8 Hz, CH2OH), 6.82 (dd, 1H, J1 ¼ 8 Hz, J2 ¼ 0.9 Hz, 6-H), 6.92
(1H, dd, J1 ¼ 8.4 Hz, J2 ¼ 0.8 Hz, 8-H), 7.55 (dd, 1H, J1 ¼ J2 ¼ 8.4 Hz,
7-H); 7.94 (t, 1H, J ¼ 0.8 Hz, 2-H), 12.25 (s, 1H, 5-H).
13C NMR, ꢀ (CDCl3): 58.3, 107.5, 111.15, 111.8, 122.09, 136.07,
154.0, 157.2, 160.98, 183.0. IR: 3415, 1651, 1271. Anal. calcd. for
C10H8O4: C, 62.50; H, 4.20. Found: C, 61.93; H, 4.28.
6-Hydroxy-3-(hydroxymethyl)-4-oxo-4H-1-benzopyrane (2c). M.p.
217–219ꢀC (Lit.[11] 215–218.5ꢀC). H NMR, ꢀ (DMSO-d6): 4.42 (d, 2H,
1
J ¼ 4.5 Hz, CH2OH), 5.17 (t, 1H, J ¼ 4.5 Hz, CH2OH), 7.29 (dd, 1H,
J1 ¼ 2.5 Hz, J2 ¼ 8.9 Hz, 7-H); 7.39 (d, 1H, J ¼ 2.5 Hz, 5-H), 7.58 (d,
1H, J ¼ 9 Hz, 8-H), 8.22 (s, 1H, 2-H), 10.08 (s, 1H, 6-OH).
3-(Hydroxymethyl)-6-methoxy-4-oxo-4H-1-benzopyrane (2d). M.p.
151–152ꢀC (Lit.[6] 150–153.5ꢀC). 1H NMR, ꢀ (CDCl3): 2.99 (t, 1H,
J ¼ 6.5 Hz, CH2OH), 3.91 (s, 3H, OCH3), 4.59 (d, 2H, J ¼ 5.6 Hz,
CH2OH), 7.29 (dd, 1H, J1 ¼ 9.3 Hz, J2 ¼ 3.0 Hz, 7-H), 7.42 (d, 1H,
J ¼ 9.2 Hz, 8-H), 7.57 (d, 1H, J ¼ 2.9 Hz, 5-H), 7.93 (s, 1H, 2-H).
ACKNOWLEDGMENTS
This work was supported by FONDECYT Grant Nꢀ 1000859,
J. H.-M. thanks DAAD for a fellowship.