January 2011
Synthesis and Reactivity of 6-Methyl-4H-furo[3,2c]pyran-3,4-dione
35
4-Hydroxy-6-methyl-3-(2-methylthiazol-4-yl)-2H-pyran-2-
one (11a). This compound was obtained as a white solid with
mp 140–141ꢂC; IR (m, cmꢁ1): 3100–3500, 2980, 1754, 1660,
1448, 1490, 1379, 990, 820, 735; UV (kmax, nm): 344 (e,
0.227); 1H NMR (DMSO-d6): d 2.22 (s, 3H, 6-CH3), 2.23(s,
3H, 60-CH3), 6.17 (s, 1H, H-5), 7.13 (s, 1H, H-50), 14.13 (s,
General procedure for the synthesis of 2-arylidene-6-
methyl-2H-furo[3,2-c]pyran-3,4-dione (14a–f).
Classical
heating conditions. A solution of 6-methyl-2H-furo[3,2-c]py-
ran-3,4-dione 8 (0.38 g, 2.3 mmol) and the appropriate benzal-
dehyde (5 mmol) in a mixture of glacial acetic acid (12 mL)
and hydrochloric acid (12 mL) was refluxed, with stirring, for
1 h. After cooling the reaction mixture to room temperature,
the obtained solid was collected by filtration and purified by
recrystallization from boiling chloroform, yielding 2-arylidene-
6-methyl-2H-furo[3,2-c]pyran-3,4-diones (14a–f): 14a (0.28 g,
49%); 14b (0.37 g, 57%), 14c (0.34 g, 52%); 14d (0.44 g,
58%), 14e (0.35 g, 52%); 14f (0.31 g, 46%).
13
1H, OH); C NMR (DMSO-d6): d 20.5 (6-CH3), 35.2 (20-
CH3), 98.4 (C-3), 102.6 (C-5), 101.6 (C-50), 140.2 (C-40),
160.8 (C-6), 162.7 (C-20), 168.7 (C-2), 181.0 (C-4); ESI(þ)
-
MS: m/z 224 [(M þ H)þ, 100], 246 [(M þ Na)þ, 10]. Anal.
Calcd. for C10H9NO3S: C, 53.90; H, 4.06; N, 6.27. Found: C,
53.82; H, 4.02; N, 6.15.
3-(2-Aminothiazol-4-yl)-4-hydroxy-6-methyl-2H-pyran-2-
one (11b). This compound was obtained as a yellow solid
with mp 290–292ꢂC; IR (m, cmꢁ1): 3100–3500, 2980, 1754,
1660, 1448, 1490, 1379, 990, 820, 735; UV (kmax, nm): 344
Microwave conditions. A solution of 6-methyl-2H-furo[3,2-
c]pyran-3,4-dione 8 (0.19 g, 1.15 mmol) and the appropriate
benzaldehyde (2.3 mmol) in a mixture of glacial acetic acid
(10 mL) and hydrochloric acid (10 mL) was irradiated with
microwave radiation (600 W) for a 2–3 min. After cooling the
reaction mixture to room temperature, the resulting solid is fil-
tered and recrystallized from chloroform, yielding 2-arylidene-
6-methyl-2H-furo[3,2-c]pyran-3,4-diones (14a–f): 14a (0.16 g,
55%); 14b (0.20 g, 62%), 14c (0.19 g, 60%); 14d (0.24 g,
65%), 14e (0.20 g, 59%); 14f (0.18 g, 55%).
2-Benzylidene-6-methyl-2H-furo[3,2-c]pyran-3,4-dione
(14a). This compound was obtained as a yellow solid with
mp 219–220ꢂC. IR (m, cmꢁ1): 1767, 1660, 1590, 1480, 1247,
1040, 895, 760, 700; 1H NMR (DMSO-d6): d 2.46 (s, 1H, 6-
CH3), 6.84 (s, 1H, H-7), 7.13 (s, 1H, ¼¼CH), 7.50–7.53 (m,
1H, H-40), 7.70–7.73 (m, 2H, H-30,50), 7.81–7.84 (m, 2H, H-
20,60); 13C NMR (DMSO-d6): d 21.2 (6-CH3), 96.8 (C-7),
101.0 (C-9), 126.2 (C-30,50), 128.0 (C-40), 128.9 (C-20,60),
130.2 (¼¼CH), 132.5 (C-10), 155.5 (C-6), 169.3 (C-2), 173.9
(C-4), 188.6 (C-8), 193.0 (C-3); ESI(þ)-MS: m/z 255 [(M þ
H)þ, 100], 277 [(M þ Na)þ, 60]. Anal. Calcd. for C15H10O4:
C, 70.86; H, 3.96. Found: C, 70.93; H, 3.99.
1
(e, 0.227); H NMR (DMSO-d6): d 2.23 (s, 3H, 6-CH3), 6.18
(s, 1H, H-5), 7.15 (s, 1H, H-50), 8.40 (s, 2H, NH2), 14.27 (s,
1H, OH); 13C NMR (DMSO-d6): d 19.4 (6-CH3), 92.7 (C-3),
101.3 (C-5), 101.9 (C-50), 139.2 (C-40), 162.0 (C-6), 168.0 (C-
20), 169.3 (C-2), 178.5 (C-4); ESI(þ)-MS: m/z ESI(þ)-MS: m/z
225 [(M þ H)þ, 100], 247 [(M þ Na)þ, 45]. Anal. Calcd. for
C9H8N2O3S: C, 48.21; H, 3.60; N, 12.49. Found: C, 48.18; H,
4.00; N, 12.38.
3-(2-Hydrazinylthiazol-4-yl)-4-hydroxy-6-methyl-2H-pyran-
2-one (11c). This compound was obtained as a yellow solid
with mp 240–242ꢂC; IR (m, cmꢁ1) 3100–3500, 2980, 1754,
1660, 1448, 1490, 1379, 990, 820, 735; UV (kmax, nm) 344 (e,
0.227); 1H NMR (DMSO-d6): d 2.23 (s, 3H, 6-CH3), 6.20 (s,
1H, H-5), 7.43 (s, 1H, H-50), 9.94 (s, 1H, NH), 14.02 (s, 1H,
OH); 13C NMR (DMSO-d6): d 19.4 (6-CH3), 94.0 (C-3), 101.2
(C-5), 104.5 (C-50), 141.6 (C-40), 161.5 (C-6), 168.4 (C-20),
169.9 (C-2), 179.6 (C-4); ESI(þ)-MS: m/z 240 [(M þ H)þ,
100], 262 [(M þ Na)þ, 60]. Anal. Calcd. for C9H9N3O3S: C,
45.18; H, 3.79; N, 17.56. Found: C, 45.01; H, 3.83; N, 17.46.
4-(4-Hydroxy-6-methyl-2-oxo-2H-pyran-3-yl)thiazole-2-
carbothioamide (11d). This compound was obtained as a
yellow solid with mp 268–269ꢂC; IR (m, cmꢁ1): 3100–3500,
2-(4-Methoxybenzylidene)-6-methyl-2H-furo[3,2-c]pyran-3,4-
dione (14b). This compound was obtained as a yellow solid
with mp 171–172ꢂC. IR (m, cmꢁ1): 1767, 1662, 1590, 1480,
1
1247, 1005, 730, 700; H NMR (DMSO-d6): d 2.39 (s, 1H, 6-
2980, 1754, 1660, 1448, 1490, 1379, 990, 820, 735; UV (kmax
,
CH3), 3.84 (s, 3H, OCH3), 6.74 (s, 1H, H-7), 7.15 (s, 1H,
¼¼CH), 7.50–7.53 (m, 2H, H-30,50), 7.70–7.73 (m, 2H, H-20,60);
13C NMR (DMSO-d6): d 21.2 (6-CH3), 56.1 (OCH3), 96.8 (C-
7), 101.0 (C-9), 114.2 (C-30,50), 130.2 (¼¼CH), 131.0 (C-10, C-
20,60), 154.5 (C-40), 155.5 (C-6), 169.3 (C-2), 174.0 (C-4),
188.6 (C-8), 193.0 (C-3); ESI(þ)-MS: m/z 285 [(M þ H)þ,
100], 307 [(M þ Na)þ, 48)]. Anal. Calcd. for C16H12O5: C,
67.60; H, 4.25. Found: C, 67.67; H, 4.30.
nm): 344 (e, 0.227); 1H NMR (DMSO-d6): d 2.26 (d, 3H,
J ¼ 0.6 Hz, 6-CH3), 6.31(s, 1H, H-5), 8.52 (s, 1H, H-50),
10.32 (s, 2H, NH2), 12.42 (s, 1H, OH); 13C NMR (DMSO-d6):
d 19.4 (6-CH3), 94.3 (C-3), 100.9 (C-5), 124.9 (C-50), 149.3
(C-40), 161.7 (C-6), 167.6 (C-20), 169.9 (C-2), 179.3 (C-4),
185.50 (C¼¼S); ESI(þ)-MS: m/z ESI(þ)-MS: m/z 269 [(M þ
H)þ, 100], 291 [(M
þ
Na)þ, 55]. Anal. Calcd. for
C10H8N2O3S2: C, 44.76; H, 3.01; N, 10.44. Found: C, 44.70;
H, 2.95; N, 10.32.
2-(4-Chlorobenzylidene)-6-methyl-2H-furo[3,2-c]pyran-3,4-
dione (14c). This compound was obtained as a yellow solid
with mp 268–269ꢂC. IR (m, cmꢁ1): 1766, 1660, 1593, 1482,
4-Hydroxy-6-methyl-3-(2-(phenyldiazenyl)thiazol-4-yl)-2H-
pyran-2-one (11e). This compound was obtained as a red
solid with mp 275–277ꢂC; IR (m, cmꢁ1) 3100–3500, 2980,
1754, 1660, 1448, 1490, 1379, 990, 820, 735; UV (kmax, nm)
344 (e, 0.227); 1H NMR (DMSO-d6): d 2.31(s, 3H, 6-CH3),
6.09 (s, 1H, H-5), 8.48 (s, 1H, H-50), 7.58–7.62 (m, 3H, Ph-
Hortho þ para), 8.01–8.05 (m, Ph-Hmeta), 13.84 (s, 1H, OH); 13C
NMR (DMSO-d6): d 20.1 (6-CH3), 94.3 (C-3), 101.5 (C-5),
117.9 (C-50), 124.1 (Ph-Cortho þ para), 129.5 (Ph-Cmeta), 133.5
(Ph-Cipso), 142.2 (C-40), 162.2 (C-6), 162.3 (C-20), 169.0 (C-2),
177.4 (C-4); ESI(þ)-MS: m/z 314 [(M þ H)þ, 100], 336 [(M þ
Na)þ, 40]. Anal. calcd. for C15H11N3O3S: C, 57.50; H, 3.54;
N, 13.41. Found: C, 57.45; H, 3.43; N, 16.08.
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1247, 1040; H NMR (DMSO-d6): d 2.43 (d, 3H, J ¼ 0.6 Hz,
6-CH3), 6.97 (d, 1H, J ¼ 0.6 Hz, H-7), 7.05 (s, 1H, ¼¼CH),
7.59 (d, 2H, J ¼ 8.6 Hz, H-30,50), 7.94 (d, 2H, J ¼ 8.6 Hz, H-
20,60); 13C NMR (DMSO-d6): d 21.2 (6-CH3), 96.8 (C-7),
101.0 (C-9), 127.2 (C-20,60), 128.9 (C-30,50), 130.2 (¼¼CH),
133.0 (C-10, C-40), 155.5 (C-6), 169.3 (C-2), 174.0 (C-4),
188.6 (C-8), 192.9 (C-3); ESI(þ)-MS: m/z 289 [(M þ H)þ,
35Cl, 48], 291 [(M þ H)þ, 37Cl, 14], 311 [(M þ Na)þ, 35Cl,
100], 313 [(M þ Na)þ, 37Cl, 30]. Anal. Calcd. for C15H9ClO4:
C, 62.41; H, 3.14. Found: C, 62.38; H, 3.10.
2-(4-Bromobenzylidene)-6-methyl-2H-furo[3,2-c]pyran-3,4-
dione (14d). This compound was obtained as a yellow solid
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet