Synthesis of c-pyrones via decarboxylative condensation of b-ketoacids
2,6-Bis(4-methoxyphenyl)-4H-pyran-4-one
(2b, C19H16O4)
2,6-Bis(4-bromophenyl)-4H-pyran-4-one
(2e, C17H10Br2O2)
The product was obtained starting from 0.36 mmol of b-
ketoacid [determined by H NMR (400 MHz, d6-DMSO)
The product was obtained starting from 0.25 mmol of b-
ketoacid [determined by H NMR (400 MHz, d6-DMSO)
1
1
using the characteristic signals: d = 3.97 (s, 2H, CH2 b-
ketoacid), 2.57 (s, 3H, CH3 ketone)]. White solid (49 mg,
0.16 mmol, 89%) after purification by column chromatog-
raphy (heptane/EtOAc = 40/60). 1H NMR (400 MHz,
CDCl3): d = 7.79 (d, 3J = 8.9 Hz, 4H), 7.02 (d,
3J = 8.9 Hz, 4H), 6.68 (s, 2H), 3.88 (s, 6H) ppm; 13C
NMR (101 MHz, CDCl3): d = 180.5, 163.3, 162.3, 127.7,
using the characteristic signals: d = 4.04 (s, 2H, CH2 b-
ketoacid), 5.85 (s, 1H, CH enol tautomer), 2.56 (s, 3H, CH3
ketone)]. White solid (19 mg, 0.047 mmol, 38%) after
purification by column chromatography (heptane/
EtOAc = 60/40). 1H NMR (400 MHz, CDCl3):
d = 7.79-7.54 (m, 8H), 6.79 (s, 2H) ppm; 13C NMR
(101 MHz, CDCl3): d = 179.8, 162.6, 132.7, 130.5, 127.5,
ꢀ
ꢀ
124.1, 114.7, 109.9, 55.6 ppm; IR: m = 3413.34, 3073.07,
2929.16, 1842.10, 1642.00, 1602.30, 1507.76, 1461.64,
126.4, 111.9 ppm; IR: m = 3365.83, 3051.06, 2922.62,
1652.22, 1614.11, 1486.45, 1410.83, 1379.67, 946.70,
821.47 cm-1; HRMS (ESI): m/z calculated for [M?H]?
404.9120, found 404.9122.
1425.15,
1388.20,
1259.26,
1177.43,
1022.74,
832.33 cm-1; HRMS (ESI): m/z calculated for [M?H]?
309.1121, found 309.1108.
2,6-Bis(3-bromophenyl)-4H-pyran-4-one
(2f, C17H10Br2O2)
2,6-Bis(2-methoxyphenyl)-4H-pyran-4-one
(2c, C19H16O4)
The product was obtained starting from 4.16 mmol of b-
ketoacid [determined by H NMR (400 MHz, d6-DMSO)
1
The product was obtained starting from 0.29 mmol of b-
ketoacid [determined by H NMR (400 MHz, d6-DMSO)
1
using the characteristic signals: d = 4.08 (s, 2H, CH2 b-
ketoacid), 5.89 (s, 1H, CH enol tautomer), 2.59 (s, 3H, CH3
ketone)]. White solid (21 mg, 0.052 mmol, 26%) after
purification by column chromatography (heptane/
using the characteristic signals: d = 3.85 (s, 2H, CH2 b-
ketoacid), 5.95 (s, 1H, CH enol tautomer), 2.52 (s, 3H, CH3
ketone)]. White solid (18 mg, 0.058 mmol, 41%) after
purification by column chromatography (heptane/
1
EtOAc = 60/40). H NMR (400 MHz, CDCl3): d = 7.96
(dd, 4J = 1.7, 1.7 Hz, 2H), 7.76 (ddd, 3J = 7.9 Hz,
1
EtOAc = 40/60). H NMR (400 MHz, CDCl3): d = 7.79
3
4
4J = 1.7, 1.0 Hz, 2H), 7.68 (ddd, J = 7.9 Hz, J = 1.7,
3
4
3
(dd, J = 7.8 Hz, J = 1.7 Hz, 2H), 7.46 (ddd, J = 8.4,
7.8 Hz, 4J = 1.8 Hz, 2H), 7.09 (s, 2H), 7.08 (ddd,
3J = 7.8, 7.8 Hz, 4J = 1.0 Hz, 2H), 7.04 (dd,
3J = 8.4 Hz, 4J = 1.0 Hz, 2H), 3.94 (s, 6H) ppm; 13C
NMR (101 MHz, CDCl3): d = 181.4, 161.2, 157.9, 132.2,
129.3, 121.0, 120.9, 116.1, 111.9, 55.8, 29.8 ppm; IR:
3
1.0 Hz, 2H), 7.42 (dd, J = 7.9, 7.9 Hz, 2H), 6.78 (s, 2H)
ppm; 13C NMR (101 MHz, CDCl3): d = 179.6, 162.1,
134.6, 133.5, 130.9, 129.1, 124.7, 123.5, 112.5 ppm; IR:
mꢀ = 3362.24, 3081.69, 2922.50, 2852.62, 1656.61,
1616.13, 1582.05, 1424.06, 1379.87, 1256.10, 1230.82,
917.37, 872.12, 785.53, 687.67 cm-1; HRMS (ESI): m/z
calculated for [M?H]? 404.9120, found 404.9101.
ꢀ
m = 3413.45, 3078.18, 2924.97, 2849.82, 1637.68,
1588.26, 1491.72, 1458.57, 1392.75, 1293.53, 1250.97,
1019.97, 757.63 cm-1; HRMS (ESI): m/z calculated for
[M?H]? 309.1121, found 309.1108.
2,6-Di-(tert-butyl)-4H-pyran-4-one (2g)
The product was obtained starting from 0.39 mmol of b-
ketoacid [determined by 1H NMR (400 MHz, CDCl3)
using the characteristic signals: d = 3.60 (s, 2H, CH2 b-
ketoacid), 5.10 (s, 1H, CH enol tautomer), 2.14 (s, 3H, CH3
ketone)]. White solid (250 mg, 1.2 mmol, 58%) after
purification by column chromatography (heptane/
2,6-Di-(p-tolyl)-4H-pyran-4-one (2d)
The product was obtained starting from 3.14 mmol of b-
ketoacid [determined by 1H NMR (400 MHz, CDCl3)
using the characteristic signals: d = 4.05 (s, 2H, CH2 b-
ketoacid), 5.68 (s, 1H, CH enol tautomer), 2.58 (s, 3H, CH3
ketone)]. Yellow solid (210 mg, 0.76 mmol, 48%) after
purification by column chromatography (heptane/
1
EtOAc = 30/70). H NMR (400 MHz, CDCl3): d = 6.11
(s, 2H), 1.26 (s, 18H) ppm; 13C NMR (101 MHz, CDCl3):
ꢀ
d = 181.5, 175.4, 109.6, 36.4, 27.9 ppm; IR: m = 3364.25,
1
EtOAc = 60/40). H NMR (400 MHz, CDCl3): d = 7.73
2961.00, 2933.97, 2870.52, 1648.26, 1613.70, 1481.30,
1461.79, 1397.12, 1380.17, 1361.50, 1256.56, 1221.79,
941.68, 921.52, 873.82 cm-1. Physical data are in accor-
dance with the literature [19].
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3
(d, J = 8.3 Hz, 4H), 7.32 (d, J = 8.0 Hz, 4H), 6.75 (s,
2H), 2.43 (s, 6H) ppm; 13C NMR (101 MHz, CDCl3):
d = 180.5, 163.5, 142.0, 130.0, 128.9, 126.0, 110.8,
ꢀ
21.6 ppm; IR: m = 3363.26, 3067.44, 2920.18, 2852.73,
1643.46, 1607.22, 1508.89, 1413.77, 1384.45, 943.62,
819.27 cm-1. Physical data are in accordance with the
literature [19].
2,6-Dibutyl-4H-pyran-4-one (2h, C13H20O2)
The product was obtained starting from 4.16 mmol of b-
ketoacid [determined by 1H NMR (400 MHz, CDCl3)
123