γꢀPyrones
Russ.Chem.Bull., Int.Ed., Vol. 59, No. 8, August, 2010
1603
Freshly distilled isopropenyl acetate (Lancaster, b.p. 94 °С
IR, νmax/cm–1: 3320—2180 (ОН), 1729 (C=O), 1704 (C=О),
1619 (C=О, C=С), 1606 (C=О, C=С), 1459, 1421, 1361, 1301,
1245, 1172. 1Н NMR of the diketo form, δ: 2.24 (s, 6 Н, 2 Ме);
3.59 (s, 2 Н, СH2). Н NMR of the enol form, δ: 2.04 (s, 6 Н,
2 Ме); 5.50 (s, 1 Н, Н(3)); 15.44 (s, 1 Н, ОH).
(760 Torr), n20 1.4011), 1,2ꢀdichloroethane (Lancaster,
D
b.p. 83 °С (760 Torr), n20 1.4440), and anhydrous powdered
D
1
aluminum chloride (Lancaster, m.p. 190 °С (subl.)) were used
in the reaction.
3,5ꢀDiacetylꢀ2,6ꢀdimethylꢀ4Нꢀpyranꢀ4ꢀone (2) and 3ꢀacetylꢀ
2,6ꢀdimethylꢀ4Нꢀpyranꢀ4ꢀone (3). Freshly distilled isopropenyl
acetate (1.5 g, 0.015 mol) was added dropwise for 3 min to
a vigorously stirred suspension of anhydrous AlCl3 (4.0 g,
0.03 mol) in anhydrous 1,2ꢀdichloroethane (15 mL), cooling
the flask with iceꢀcold water. A transparent light yellow solution
that formed was refluxed for 1 h. After cooling to ~20 °C, the
solution was poured to a mixture of 20 mL of 15% hydrochloric
acid and 10 g of chipped ice. The organic layer was separated
and washed with 5% hydrochloric acid (3×10 mL). The aqueous
phases were combined, and the reaction products were addiꢀ
tionally extracted with chloroform (3×30 mL). The combined
organic phases were washed with water (3×15 mL) to the neutral
pH in the washings and dried (Na2SO4). The solvent was
removed, and the residue was chromatographed on a column
with SiO2. Elution with a hexane—acetone (6 : 1) mixture gave
0.133 g (17%) of γꢀpyrone 2, light yellow needles, m.p. 125—126 °С
(from hexane) (cf. Ref. 1: m.p. 124 °С; Ref. 4: m.p. 120—121 °С;
Ref. 12: m.p. 125.5—127 °С). IR, νmax/cm–1: 1697 (C=O), 1649
The subsequent elution with a hexane—acetone (15 : 1)
mixture gave 0.013 g of heptaneꢀ2,4,6ꢀtrione (diacetylacetone),
colorless crystals, m.p. 48—49 °С (from hexane) (cf. Ref. 1:
m.p. 49 °С; Ref. 11: m.p. 45—47 °С). IR, νmax/cm–1: 3390—2320
(ОН), 1732 (C=O), 1716 (C=О), 1626 (C=О, C=С), 1615
(C=О, C=С), 1601 (C=О, C=С), 1590, 1583, 1485, 1460, 1415,
1370, 1359, 1300, 1242, 1176. 1Н NMR of the triketo form, δ:
2.22 (s, 6 Н, 2 Ме); 3.70 (s, 4 Н, 2 СН2). 1Н NMR of the
monoenol form, δ: 1.98 (s, 3 Н, С(2)Ме); 2.26 (s, 3 Н, С(6)Ме);
3.40 (s, 2 Н, СН2); 5.56 (s, 1 Н, Н(3)); 15.20 (s, 1 Н, ОH).
1Н NMR of the dienol form, δ: 2.08 (s, 6 Н, 2 Ме); 5.14 (s, 2 Н,
Н(3), Н(5)); 14.17 (s, 2 Н, 2 ОH).
The subsequent elution with a hexane—acetone (10 : 1)
mixture gave 0.036 g of 3ꢀacetylpentaneꢀ2,4ꢀdione (triacetylꢀ
methane), poorly mobile light yellow liquid, n25 = 1.4903,
D
(cf. Ref. 9: n25D = 1.4893; Ref. 10: n20D = 1.5600). IR, νmax/cm–1
:
3370—2190 (ОН), 1679 (C=O), 1619 (C=О, C=С), 1598 (C=О,
C=С), 1587 (C=О, C=С), 1414, 1359, 1299, 1235, 1154.
1Н NMR, δ: 2.24 (s, 6 Н, 2 Ме); 2.43 (s, 3 Н, С(3)СОМе);
17.20 (s, 1 Н, ОH).
1
(C=О), 1626 (C=С), 1403, 1371, 1357, 1150, 1061. Н NMR,
δ: 2.36 (s, 6 Н, С(2)Me, С(6)Ме); 2.55 (s, 6 Н, С(3)COMe,
С(5)СОМе). 13С NMR, δ: 18.6 (C(7), C(10)); 31.8 (C(9),
C(12)); 127.4 (C(3), С(5)); 166.4 (C(2), C(6)); 175.1 (C(4));
199.7 (C(8), C(11)). MS, m/z (Irel (%)): 209 [М + 1]+ (14), 208
[М]+ (100), 207 [М – 1]+ (3), 193 (2), 192 (4), 166 (6), 165 (18),
162 (3), 152 (5), 151 (48), 148 (9), 138 (4), 127 (6), 125 (21),
123 (6), 111 (5), 109 (31), 85 (8), 67 (33), 44 (49). Found (%):
С, 63.29; Н, 5.86. С11Н12О4. Calculated (%): С, 63.45; Н, 5.81.
The subsequent elution with a hexane—acetone (4 : 1)
mixture gave 0.009 g (1%) of γꢀpyrone 3, light yellow prisms,
m.p. 56—58 °С (from hexane) (cf. Ref. 17: m.p. 58—60 °С;
Ref. 1: m.p. 63—64 °С). IR, νmax/cm–1: 1694 (C=O), 1664
(C=О), 1625 (C=С), 1621 (C=С), 1402, 1372, 1356, 1159,
The subsequent elution with a hexane—acetone (6 : 1)
mixture gave 0.031 g (4%) of γꢀpyrone 2 identical to that
described above.
The subsequent elution with a hexane—acetone (4 : 1)
mixture gave 0.003 g (0.4%) of γꢀpyrone 3 identical to that
described above.
3ꢀAcetylꢀ2,6ꢀdimethylꢀ4Нꢀpyranꢀ4ꢀone (3). A solution of
γꢀpyrone 2 (0.019 g, 0.091 mmol) in 3 mL of 2% hydrochloric
acid was stirred for 16 h at ~20 °C, diluted with 10 mL of water,
and extracted with chloroform (3×5 mL). The combined organic
extract was washed with brine (3×3 mL) and dried (Na2SO4).
The solvent was removed, and the residue was chromatographed
on a column with SiO2. Elution with a hexane—acetone (4 : 1)
mixture gave 0.013 g (87%) of γꢀpyrone 3 identical to that
described above.
2,6ꢀDimethylꢀ4Нꢀpyranꢀ4ꢀone (4). A solution of γꢀpyrone 2
(0.103 g, 0.493 mmol) in 2 mL of acetone and 20 mL of 17%
hydrochloric acid was refluxed for 3 h, then cooled to ~20 °C,
diluted with 20 mL of water, and extracted with chloroform
(3×20 mL). The combined organic extract was washed with
brine (3×10 mL) and dried (Na2SO4), the solvent was removed,
and the residue was recrystallized from a benzene—acetone (8 : 1)
mixture. γꢀPyrone 4 was obtained in a yield of 0.037 g (61%),
colorless needles, m.p. 131—132 °С (cf. Ref. 7: m.p. 131—132 °С;
Ref. 1: m.p. 130—131 °С). IR, νmax/cm–1: 1667 (C=О), 1613
(C=С), 1442, 1398, 1374, 1332, 1194, 1159, 1034. 1Н NMR, δ:
2.25 (s, 6 Н, С(2)Me, С(6)Ме); 6.06 (s, 2 Н, Н(3), Н(5)).
13С NMR, δ: 19.7 (C(7), C(8)); 113.7 (C(3), C(5)); 165.5 (C(2),
C(6)); 180.3 (C(4)). MS, m/z (Irel (%)): 125 [М + 1]+ (8), 124 [М]+
(100), 109 (2), 97 (3), 96 (26), 95 (34), 85 (4), 84 (6), 82 (2), 81
(23), 69 (39), 67 (5), 56 (3), 53 (8), 44 (59), 40 (11).
1
1042. Н NMR, δ: 2.26 (d, 3 Н, С(6)Ме, J = 0.6 Hz); 2.36 (s,
3 Н, С(2)Ме); 2.55 (s, 3 Н, С(3)СОМе); 6.15 (q, 1 Н, Н(5),
J = 0.6 Hz). 13С NMR, δ: 18.8 C(10)); 19.6 (C(7)); 32.0 (C(9));
114.9 (C(5)); 126.5 (С(3)); 164.8 (C(6)); 167.3 (C(2)); 177.4
(C(4)); 200.6 (C(8)). MS, m/z (Irel (%)): 167 [М + 1]+ (10), 166
[М]+ (100), 165 [М – 1]+ (7), 152 (3), 151 (42), 149 (8), 148 (50),
125 (9), 124 (18), 123 (6), 110 (5), 109 (35), 85 (16), 69 (9), 67
(86), 44 (49). Found (%): С, 65.17; Н, 6.12. С9Н10О3. Calculꢀ
ated (%): С, 65.05; Н, 6.07.
Under the conditions described,12 0.02 g of γꢀpyrone 2 gave
0.017 g of its 2,4ꢀdinitrophenylhydrazone as yellow needles,
m.p. 188—190 °С (from EtOH) (cf. Ref. 12: m.p. 189—191 °С).
Under the conditions described,12 0.02 g of γꢀpyrone 3 gave
0.015 g of its 2,4ꢀdinitrophenylhydrazone as orange needles,
m.p. 193—195 °С (from EtOH) (cf. Ref. 17: m.p. 194—196 °С).
Interaction of isopropenyl acetate with AlCl3 at room temperaꢀ
ture. As described above, a transparent solution, which was stored
for 24 h at ~20 °C, was obtained from freshly distilled isopropenyl
acetate (1.5 g, 0.015 mol), anhydrous AlCl3 (4.0 g, 0.03 mol),
and anhydrous 1,2ꢀdichloroethane (15 mL). The treatment
analogous to that described above gave a mixture of products,
which was separated on a column with SiO2. Elution with a
hexane—acetone (20 : 1) mixture gave 0.011 g of pentaneꢀ
2,4ꢀdione (acetylacetone), mobile colorless liquid, n25D = 1.4497.
This work was financially supported by the FarꢀEastern,
Siberian, and Ural Branches of the Russian Academy
of Sciences (Program No. 09ꢀIIꢀSUꢀ05ꢀ001) and the
FarꢀEastern Branch of the Russian Academy of Sciences
(Program No. 09ꢀIIIꢀAꢀ05ꢀ149).