ꢀꢀꢀꢁ
510ꢀ ꢀB. Prek et al.: Thermal metal-free [2+2] cycloadditions
Ph + chloroform). –ꢀ13C NMR (CDCl3, 75.5 MHz): δꢀ=ꢀ34.6,
35.3, 37.2, 38.2, 39.4, 40.6, 50.6, 52.5, 84.6, 106.2, 116.5,
122.2, 128.6, 128.9, 129.4, 130.4, 135.6, 144.3, 163.3, 167.2,
4.5 Diethyl 2-(3,3-bis(dimethylamino)
allylidene)-3-(1,3-dioxo-1,3-dihydro-2H-
indene-2-ylidene)succinate (2e)
170.7, 174.2. – HRMS ((+)-EI): m/zꢀ=ꢀ455.2279 (calcd.
+
455.2289 for C24H31N4O5, [Mꢀ+ꢀH] ). – IR: νmaxꢀ=ꢀ3011, 2943, The product was prepared from 2-(3,3-bis(dimethylamino)
2796, 2247, 2203, 1715, 1671, 1629, 1579, 1532, 1515, 1465, allylidene)-1H-indene-1,3(2H)-dione (1d, 62 mg, 0.23 mmol)
1447, 1433, 1392, 1329, 1295, 1245, 1229, 1186, 1159, 1118, and DEAD (73 μL, 0.64 mmol) in 0.4 mL of acetonitrile,
1060, 1021, 915, 846, 725, 699 cm−1.
75°C, 20 min. Column chromatography, ethyl acetate–etha-
nolꢀ=ꢀ1:1. Yield: 44% (45 mg), red-brown oil. – 1H NMR (CDCl3,
500 MHz): δꢀ=ꢀ1.24 (3H, t, Jꢀ=ꢀ7.1 Hz, CH3), 1.33 (3H, t, Jꢀ=ꢀ7.1 Hz,
CH3), 3.12 (12 H, s, N(CH3)2), 4.18 (2H, q, Jꢀ=ꢀ7.1 Hz, OCH2), 4.35
(2J, q, Jꢀ=ꢀ7.1 Hz, OCH2), 6.10 (1H, d, Jꢀ=ꢀ15.0 Hz, CH), 7.37 (1H,
d, Jꢀ=ꢀ15.0 Hz, CH), 7.47–7.50 (2H, m, Ph), 7.60–7.63 (2H, m, Ph).
4.3 1-Ethyl 4,5-dimethyl 1-cyano-6-
(dimethylamino)hexa-1,3,5-trien-1,4,5-
tricarboxylate (2c)
13
– C NMR (CDCl3, 125 MHz): δꢀ=ꢀ14.2, 14.22, 43.0, 60.3, 61.6,
The product was prepared from ethyl 2-cyano-5- 105.3, 110.3, 111.9, 120.6, 132.3, 140.7, 149.8, 153.6, 167.5, 170.1,
(dimethylamino)penta-2,4-dienoate
(1c,
47
mg, 171.7, 189.8. – HRMS ((+)-EI): m/zꢀ=ꢀ441.2022 (calcd. 441.2020
+
0.24 mmol) and DMAD (209 μL, 1.70 mmol) in 1 mL of ace- for C24H29N2O6, [Mꢀ+ꢀH] ). – IR: νmaxꢀ=ꢀ3484, 2978, 2929, 2900,
tonitrile, 100°C, 40 min. Column chromatography, ethyl 1723, 1707, 1612, 1572, 1495, 1398, 1361, 1341, 1308, 1231, 1189,
acetate–petroleum etherꢀ=ꢀ1:1. Yield: 42% (35 mg), red oil. 1166, 1123, 1056, 1016, 968, 948, 877, 796, 729, 666 cm−1.
– 1H NMR (CDCl3, 300 MHz): δꢀ=ꢀ1.36 (3H, t, Jꢀ=ꢀ7.1 Hz, CH3),
2.88 (6H, br. s, N(CH3)2), 3.65 (3H, s, OCH3), 3.83 (3H, s,
OCH3), 4.33 (2H, q, Jꢀ=ꢀ7.1 Hz, OCH2), 7.53 (1H, d, Jꢀ=ꢀ12.1 Hz,
4.6 Dimethyl 2-(3-benzyl-5-methyl-1,3,4-
thiadiazol-2(3H)-ylidene)-3-(2-
CH), 7.76 (1H, s, CH), 7.79 (1H, d, Jꢀ=ꢀ12.1 Hz, CH). – 13C NMR
(CDCl3, 75.5 MHz): δꢀ=ꢀ14.2, 43.1, 51.6, 53.0, 62.8, 91.2, 109.2,
113.9, 129.9, 143.7, 150.2, 153.1, 161.7, 167.4, 168.3. – HRMS
((+)-EI): m/zꢀ=ꢀ337.1394 (calcd. 337.1394 for C16H21N2O6,
oxo-2-phenylethylidene) succinate (2f)
The product was prepared from 2-(3-benzyl-5-methyl-1,3,4-
thiadiazol-2(3H)-ylidene)-1-phenylethan-1-one (1e, 185 mg,
0.60 mmol) and DMAD (148 μL, 1.20 mmol) in 1 mL of
acetonitrile, 90 C, 15 min. Column chromatography, ethyl
acetate–petroleum etherꢀ=ꢀ1:3. Yield: 73% (270 mg), red oil.
– 1H NMR (CDCl3, 300 MHz): δꢀ=ꢀ2.45 (3H, s, CH3), 3.42 (3H, s,
OCH3), 3.59 (3H, s, OCH3), 5.11 (1H, br. s, CH2), 5.28 (1H, br. s,
CH2), 6.96–7.00 (2H, m, Ph), 7.19–7.26 (3H, m, Ph), 7.40–7.46
(2H, m, Ph), 7.53–7.58 (1H, m, Ph), 7.78 (1H, s, CH), 7.84–7.88
(2H, m, Ph). – 13C NMR (CDCl3, 75.5 MHz): δꢀ=ꢀ15.3, 51.6, 52.7,
56.2, 83.7, 126.8, 127.2, 127.7, 128.5, 128.6, 131.7, 133.4, 135.5,
136.9, 137.4, 152.7, 161.3, 167.7, 167.9, 191.7. – HRMS ((+)-EI):
+
[Mꢀ+ꢀH] ). – IR: νmaxꢀ=ꢀ2985, 2953, 2848, 2224, 1873, 1718,
1603, 1433, 1232, 1140, 1086, 1041, 1014, 949, 915, 842, 783,
762, 732 cm−1.
4.4 Dimethyl 2-(3,3-bis(dimethylamino)
allylidene)-3-(1,3-dioxo-1,3-dihydro-2H-
indene-2-ylidene)succinate (2d)
The product was prepared from 2-(3,3-bis(dimethylamino)
allylidene)-1H-indene-1,3(2H)-dione (1d, 32.8 mg,
0.12 mmol) and DMAD (30 μL, 0.24 mmol) in 0.4 mL of
acetonitrile, 80°C, 10 min. Column chromatography,
ethyl acetate–ethanolꢀ=ꢀ1:1. Yield: 22% (11 mg), brown oil.
+
m/zꢀ=ꢀ451.1327 (calcd. 451.1322 for C24H23N2O5S, [Mꢀ+ꢀH] ).
– IR: νmaxꢀ=ꢀ3030, 2993, 2944, 2833, 1716, 1654, 1594, 1583,
1494, 1449, 1427, 1317, 1247, 1183, 1107, 1043, 1013, 983, 941,
891, 865, 796, 739, 697 cm−1.
1
– H NMR (CDCl3, 500 MHz): δꢀ=ꢀ3.11 (12H, s, 2×ꢀ N(CH3)2),
3.70 (3H, s, OCH3), 3.87 (3H, s, OCH3), 7.34 (1H, d, Jꢀ=ꢀ15.1 Hz,
CH), 7.34 (1H, d, Jꢀ=ꢀ15.0 Hz, CH), 7.47–7.50 (2H, m, Ph), 7.58–
7.61 (2H, m, Ph). – 13C NMR (CDCl3, 125 MHz): δꢀ=ꢀ43.0, 51.5,
52.7, 105.5, 110.0, 111.5, 120.7, 132.3, 140.6, 149.1, 152.9, 167.9,
170.7, 171.5, 189.9. – HRMS ((+)-EI): m/zꢀ=ꢀ413.1703 (calcd.
4.7 Dimethyl 2-(3,5-dimethyl-1,3,4-tiadiazol-
2(3H)-ylidene)-3-(2-(4-methoxyphenyl)-
2-oxoethylidene)succinate (2g)
+
413.1707 for C22H25N2O6, [Mꢀ+ꢀH] ). – IR: νmaxꢀ=ꢀ3486, 2948,
2925, 2853, 1718, 1614, 1572, 1522, 1488, 1432, 1392, 1336,
1314, 1236, 1191, 1173, 1126, 1056, 964, 914, 891, 773,725, The product was prepared from 2-(3,5-dimethyl-1,3,4-thi-
665 cm−1.
adiazol-2(3H)-ylidene)-1-(4-methoxyphenyl)ethan-1-one
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